The Anatomy of Full Term Neonate
Gray's Anatomy 39th edition. Elsevier. 2008
Figure 1 Timetable of development of the body systems. The development of individual systems can be seen progressing from left to right. Embryonic stages, weeks of development and embryo length are shown. Embryonic stages are associated with external and internal morphological features rather than embryonic length. To identify the systems and organs at risk at any time of development, follow a vertical progression from top to bottom. (Click Image to Enlarge)
Figure 2 The two timescales used to depict human development. Embryonic development, in the upper scale, is counted from fertilization (or from ovulation, i.e. in postovulatory days; see O'Rahilly & Muller 1987). Throughout this book, times given for development are based on this scale. The clinical estimation of pregnancy is counted from the last menstrual period and is shown on the lower scale; throughout this book, fetal ages relating to neonatal anatomy and growth will have been derived from the lower scale. Note that there is a 2 week discrepancy between these scales. The perinatal period is very long, because it includes all preterm deliveries.
Immediately after parturition the fetus, once it has been exposed to the environment external to the maternal uterus, becomes a neonate. In Western societies, technological advances have enabled successful management of preterm infants, many at ages that were considered non-viable a decade or two previously. Now, the study of neonatology very much overlaps the later stages of fetal development. Preterm infants, although obviously past organogenetic processes, are still engaged in maturational processes with local interactions and pattern formation driving development at local and body-system levels. The sudden release of such fetuses into a gaseous environment, of variable temperature, with full gravity and a range of microorganisms promotes the rapid maturation of some systems and the compensatory growth, in terms of effect of gravity or enteral feeding or exposure to microorganisms, of others. To understand this multitude of mechanisms operating within a newly delivered fetus, as much information as possible concerning normal embryological and fetal development is required.
Details of the relative positions of the viscera and the skeleton in a full term neonate are shown in Figs 3A, B, C; 4. The newborn infant is not a miniature adult, and extremely preterm infants are not the same as full-term infants. Thus, just as there are immense differences in the relations of some structures between the full-term neonate, child and adult, so there are also major differences between the 20 week gestation fetus and the 40 week fetus, just before birth. The study of fetal anatomy at 20, 25, 30 and 35 weeks is vital for the investigative and life-saving procedures carried out on preterm infants today.
Figure 11.4 Topographical representation of the anatomy of a full-term neonate. The surface markings of all organs are shown, with some coloured and others only in outline. The female genital tract is shown on the right of the body in C, with the male tract on the left.
Figure 4. The extent of the ossified skeleton in the full term neonate. Note the derivation of the parts of the skeleton: the skull is derived from paraxial mesenchyme and neural crest mesenchyme; the axial skeleton, vertebrae and ribs are derived from paraxial mesenchyme; the skeletal elements in the limbs are derived from the somatopleuric mesenchyme, which forms the limb buds.
Details of the relative positions of the viscera and the skeleton in a full term neonate are shown in Figs 3 and 4. The newborn infant is not a miniature adult, and extremely preterm infants are not the same as full-term infants. Thus, just as there are immense differences in the relations of some structures between the full-term neonate, child and adult, so there are also major differences between the 20 week gestation fetus and the 40 week fetus, just before birth. The study of fetal anatomy at 20, 25, 30 and 35 weeks is vital for the investigative and life-saving procedures carried out on preterm infants today.
Neonatal measurements and period of time in utero
The 10th to 90th centile ranges for length of full-term neonates are c.48 cm to c.53 cm Length of the newborn is measured from crown to heel. In utero, length has been estimated either from crown-rump length, i.e. the greatest distance between the vertex of the skull and the ischial tuberosities, with the fetus in the natural curved position, or from the greatest length exclusive of the lower limbs. Greatest length is independent of fixed points and thus much simpler to measure. It is generally taken to be the sitting height in postnatal life. This measurement is recommended by O'Rahilly and Muller (2000) as the standard in ultrasound examination. The 10th to 90th centile ranges for weight of the full-term infant at parturition ranges are c.2700 g to c.3800 g , the average being 3400 g; 75-80% of this weight is body water and a further 15-28% is composed of adipose tissue. After birth, there is a general decrease in the total body water, but a relative increase in intracellular fluid. Normally, the newborn loses c.10% of the birth weight by 3-4 days postnatally, because of loss of excess extracellular fluid and meconium. By 1 year, total body water makes up 60% of the body weight. Two populations of neonates are at particular risk, namely those who are preterm, and those who are small-for-dates, some of whom have suffered 'intrauterine growth restriction'.
Low birth weight has been defined as less than 2500 g, very low birth weight as less than 1500 g, and extremely low birth weight as less than 1000 g. Infants may weigh less than 2500 g but not be premature by gestational age. Measurement of the range of weights fetuses may attain before birth has led to the production of weight charts, which allow babies to be described according to how appropriate their birth weight is for their gestational age, e.g. small for gestational age, appropriate for gestational age and large for gestational age. Small for gestational age infants, also termed 'small-for-dates', are often the outcome of intrauterine growth retardation. The causes of growth restriction are many and various and beyond the scope of this text.
For both premature and growth-retarded infants, an assessment of gestational age, which correlates closely with the stage of maturity, is desirable. Gestational age at birth is predicted by its proximity to the estimated date of delivery and the results of ultrasonographic examinations during pregnancy. It is currently assessed in the neonate by evaluation of a number of external physical and neuromuscular signs. Scoring of these signs results in a cumulative score of maturity that is usually within ± 2 weeks of the true age of the infant. The scoring scheme has been devised and improved over many years. For an account of methods of assessing gestational age in neonates, consult Gandy (1992).
Sunday, August 31, 2008
Anatomy of the Neonates
Syncope
Syncope
Ann Maguire - Kochar's Clinical Medicine for Students, 5th Edition. Lippincott Williams & Wilkins. 2008
Differential Diagnosis
Neurally Mediated Syncope
Table 1 Causes of syncope
Orthostatic Hypotension
| Table 2 Clinical features, electrocardiogram, and other key diagnostic testing related to common causes of syncope | ||||||||||||||||||||||||||||||||||||||||||||||||||
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Neurologic Disease
Medications
Psychiatric Disorders
Evaluation
prolonged QT syndromes), palpitations (tachyarrhythmias), postictal symptoms (neurologic syncope), situational symptoms (such as defecation and urination), use of medications, and history of organic heart disease (predisposing to arrhythmias or ischemia). Careful evaluation for the presence of physical findings including murmurs, carotid bruits, asymmetric pulses, and muffled heart sounds is important. Assessment of pulse and blood pressure while lying, sitting, and standing should be performed on all patients presenting with syncope during the initial examination. Every patient should also undergo electrocardiogram (ECG) testing to screen further for evidence of organic heart disease including ischemia, prolonged QT, and arrhythmia (Fig. 1).
Evaluation of Unexplained Syncope
Branch 1: High Likelihood of Underlying Organic Heart Disease
Branch 3: No Suspected Organic Heart Disease, Age <60>
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Saturday, August 30, 2008
Valvular Heart Disease
Valvular Heart Disease
MITRAL STENOSIS
Etiology and Pathology
Rheumatic fever is the leading cause of mitral stenosis (MS) (Table 1). Other less common etiologies of obstruction to left atrial outflow include congenital mitral valve stenosis, cor triatriatum, mitral annular calcification with extension onto the leaflets, systemic lupus erythematosus, rheumatoid arthritis, left atrial myxoma, and infective endocarditis with large vegetations. Pure or predominant MS occurs in approximately 40% of all patients with rheumatic heart disease and a history of rheumatic fever. In other patients with rheumatic heart disease, lesser degrees of MS may accompany mitral regurgitation (MR) and aortic valve disease. With reductions in the incidence of acute rheumatic fever, particularly in temperate climates and developed countries, the incidence of MS has declined considerably over the past few decades. However, it remains a major problem in developing nations, especially in tropical and semitropical climates (see "Global Burden of Valvular Heart Disease").
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| Note: AV, atrioventricular; HOCM, hypertrophic obstructive cardiomyopathy; HTN, hypertension; IE, infective endocarditis; LV, left ventricular; MI, myocardial infarction; MVP, mitral valve prolapse; RA, rheumatoid arthritis; RV, right ventricular; SAM, systolic anterior motion of the anterior mitral valve leaflet; SLE, systemic lupus erythematosus; TVP, tricuspid valve prolapse. |
In rheumatic MS, the valve leaflets are diffusely thickened by fibrous tissue and/or calcific deposits. The mitral commissures fuse, the chordae tendineae fuse and shorten, the valvular cusps become rigid, and these changes, in turn, lead to narrowing at the apex of the funnel-shaped ("fish-mouth") valve. Although the initial insult to the mitral valve is rheumatic, the later changes may be a nonspecific process resulting from trauma to the valve caused by altered flow patterns due to the initial deformity. Calcification of the stenotic mitral valve immobilizes the leaflets and narrows the orifice further. Thrombus formation and arterial embolization may arise from the calcific valve itself, but in patients with atrial fibrillation (AF), thrombi arise more frequently from the dilated left atrium (LA), particularly the left atrial appendage.
Pathophysiology
In normal adults, the area of the mitral valve orifice is 4–6 cm2. In the presence of significant obstruction, i.e., when the orifice area is reduced to < ~2 cm2, blood can flow from the LA to the left ventricle (LV) only if propelled by an abnormally elevated left atrioventricular pressure gradient (see Fig. 223-2), the hemodynamic hallmark of MS. When the mitral valve opening is reduced to <1>2, often referred to as "severe" MS, a LA pressure of ~25 mmHg is required to maintain a normal cardiac output (CO). The elevated pulmonary venous and pulmonary arterial (PA) wedge pressures reduce pulmonary compliance, contributing to exertional dyspnea. The first bouts of dyspnea are usually precipitated by clinical events that increase the rate of blood flow across the mitral orifice, resulting in further elevation of the LA pressure (see below).
To assess the severity of obstruction hemodynamically, both the transvalvular pressure gradient and the flow rate must be measured. The latter depends not only on the CO but on the heart rate as well. An increase in heart rate shortens diastole proportionately more than systole and diminishes the time available for flow across the mitral valve. Therefore, at any given level of CO, tachycardia including that associated with AF augments the transvalvular pressure gradient and elevates further the LA pressure. Similar considerations apply to the pathophysiology of tricuspid stenosis.
The LV diastolic pressure and ejection fraction (EF) are normal in isolated MS. In MS and sinus rhythm, the elevated LA and PA wedge pressures exhibit a prominent atrial contraction (ay descent) (see Fig. 223-2). In severe MS and whenever pulmonary vascular resistance is significantly increased, the pulmonary arterial pressure (PAP) is elevated at rest and rises further during exercise, often causing secondary elevations of right ventricular (RV) end-diastolic pressure and volume.
Cardiac Output
In patients with moderate MS (mitral valve orifice 1.0 cm2–1.5 cm2), the CO is normal or almost so at rest but rises subnormally during exertion. In patients with severe MS (valve area <1.0>2), particularly those in whom pulmonary vascular resistance is markedly elevated, the CO is subnormal at rest and may fail to rise or may even decline during activity.
Pulmonary Hypertension
The clinical and hemodynamic features of MS are influenced importantly by the level of the PAP. Pulmonary hypertension results from: (1) passive backward transmission of the elevated LA pressure; (2) pulmonary arteriolar constriction, which presumably is triggered by LA and pulmonary venous hypertension (reactive pulmonary hypertension); (3) interstitial edema in the walls of the small pulmonary vessels; and (4) organic obliterative changes in the pulmonary vascular bed. Severe pulmonary hypertension results in RV enlargement, secondary tricuspid regurgitation (TR) and pulmonic regurgitation (PR), as well as right-sided heart failure.
Symptoms
In temperate climates, the latent period between the initial attack of rheumatic carditis (in the increasingly rare circumstances in which a history of one can be elicited) and the development of symptoms due to MS is generally about two decades; most patients begin to experience disability in the fourth decade of life. Studies carried out before the development of mitral valvotomy revealed that once a patient with MS became seriously symptomatic, the disease progressed continuously to death within 2–5 years.
In patients whose mitral orifices are large enough to accommodate a normal blood flow with only mild elevations of LA pressure, marked elevations of this pressure leading to dyspnea and cough may be precipitated by sudden changes in the heart rate, volume status, or CO, as for example with severe exertion, excitement, fever, severe anemia, paroxysmal AF and other tachycardias, sexual intercourse, pregnancy, and thyrotoxicosis. As MS progresses, lesser stresses precipitate dyspnea, and the patient becomes limited in daily activities, and orthopnea and paroxysmal nocturnal dyspnea develop. The development of permanent AF often marks a turning point in the patient's course and is generally associated with acceleration of the rate at which symptoms progress.
Hemoptysis results from rupture of pulmonary-bronchial venous connections secondary to pulmonary venous hypertension. It occurs most frequently in patients who have elevated LA pressures without markedly elevated pulmonary vascular resistances and is almost never fatal. Recurrent pulmonary emboli, sometimes with infarction, are an important cause of morbidity and mortality late in the course of MS. Pulmonary infections, i.e., bronchitis, bronchopneumonia, and lobar pneumonia, commonly complicate untreated MS, especially during the winter months. Infective endocarditis is rare in isolated MS.
Pulmonary Changes
In addition to the aforementioned changes in the pulmonary vascular bed, fibrous thickening of the walls of the alveoli and pulmonary capillaries occurs commonly in MS. The vital capacity, total lung capacity, maximal breathing capacity, and oxygen uptake per unit of ventilation are reduced. Pulmonary compliance falls further as pulmonary capillary pressure rises during exercise.
Thrombi and Emboli
Thrombi may form in the left atria, particularly in the enlarged atrial appendages of patients with MS. Systemic embolization, the incidence of which is 10–20%, occurs more frequently in patients with AF, in older patients, and in those with a reduced CO. However, systemic embolization may be the presenting feature in otherwise asymptomatic patients with only mild MS.
Physical Findings
Inspection and Palpation
In patients with severe MS, there may be a malar flush with pinched and blue facies. In patients with sinus rhythm and severe pulmonary hypertension or associated tricuspid stenosis (TS), the jugular venous pulse reveals prominent a waves due to vigorous right atrial systole. The systemic arterial pressure is usually normal or slightly low. An RV tap along the left sternal border signifies an enlarged RV. A diastolic thrill may be present at the cardiac apex, with the patient in the left lateral recumbent position.
Auscultation
The first heart sound (S1) is usually accentuated and slightly delayed. The pulmonic component of the second heart sound (P2) also is often accentuated, and the two components of the second heart sound (S2) are closely split. The opening snap (OS) of the mitral valve is most readily audible in expiration at, or just medial to the cardiac apex. This sound generally follows the sound of aortic valve closure (A2) by 0.05–0.12 s. The time interval between A2 and OS varies inversely with the severity of the MS. The OS is followed by a low-pitched, rumbling, diastolic murmur, heard best at the apex with the patient in the left lateral recumbent position (see Fig. 220-4B). It is accentuated by mild exercise (e.g., a few rapid sit-ups) carried out just before auscultation. In general, the duration of this murmur correlates with the severity of the stenosis in patients with preserved CO. In patients with sinus rhythm, the murmur often reappears or becomes louder during atrial systole (presystolic accentuation). Soft grade I or II/VI systolic murmurs are commonly heard at the apex or along the left sternal border in patients with pure MS and do not necessarily signify the presence of MR. Hepatomegaly, ankle edema, ascites, and pleural effusion, particularly in the right pleural cavity, may occur in patients with MS and RV failure.
Associated Lesions
With severe pulmonary hypertension, a pansystolic murmur produced by functional TR may be audible along the left sternal border. This murmur is usually louder during inspiration and diminishes during forced expiration (Carvallo's sign). When the CO is markedly reduced in MS, the typical auscultatory findings, including the diastolic rumbling murmur, may not be detectable (silent MS), but they may reappear as compensation is restored. The Graham Steell murmur of PR, a high-pitched, diastolic, decrescendo blowing murmur along the left sternal border, results from dilatation of the pulmonary valve ring and occurs in patients with mitral valve disease and severe pulmonary hypertension. This murmur may be indistinguishable from the more common murmur produced by aortic regurgitation (AR), though it may increase in intensity with inspiration and is accompanied by a loud P2.
Laboratory Examination
ECG
In MS and sinus rhythm, the P wave usually suggests LA enlargement (see Fig. 221-8). It may become tall and peaked in lead II and upright in lead V1 when severe pulmonary hypertension or TS complicates MS and right atrial (RA) enlargement occurs. The QRS complex is usually normal. However, with severe pulmonary hypertension, right axis deviation and RV hypertrophy are often present.
Echocardiogram
Transthoracic two-dimensional echocardiography (TTE) with color flow Doppler imaging provides critical information, including an estimate of the transvalvular peak and mean gradients and of mitral orifice size, the presence and severity of accompanying MR, the extent of restriction of valve leaflets and their thickness, the degree of distortion of the subvalvular apparatus, and the anatomic suitability for percutaneous mitral balloon valvotomy (PMBV; see below). In addition, TTE provides an assessment of the size of the cardiac chambers, an estimation of LV function, an estimation of the pulmonary artery pressure (PAP), and an indication of the presence and severity of associated valvular lesions. Transesophageal echocardiography (TEE) provides superior images and should be employed when TTE is inadequate for guiding therapy. TEE is especially indicated to exclude the presence of left atrial thrombi prior to PMBV.
Chest X-Ray
The earliest changes are straightening of the upper left border of the cardiac silhouette, prominence of the main pulmonary arteries, dilatation of the upper lobe pulmonary veins, and posterior displacement of the esophagus by an enlarged LA. Kerley B lines are fine, dense, opaque, horizontal lines that are most prominent in the lower and mid-lung fields and that result from distention of interlobular septae and lymphatics with edema when the resting mean LA pressure exceeds approximately 20 mmHg.
Differential Diagnosis
Like MS, significant MR may also be associated with a prominent diastolic murmur at the apex due to increased flow, but in MR this diastolic murmur commences slightly later than in patients with MS, and there is often clear-cut evidence of LV enlargement. An apical pansystolic murmur of at least grade III/VI intensity as well as an S3 suggests significant associated MR. Similarly, the apical mid-diastolic murmur associated with severe AR (Austin Flint murmur) may be mistaken for MS but can be differentiated from it because it is not intensified in presystole. TS, which occurs rarely in the absence of MS, may mask many of the clinical features of MS or be clinically silent.
Atrial septal defect may be mistaken for MS; in both conditions there is often clinical, ECG, and chest x-ray evidence of RV enlargement and accentuation of pulmonary vascularity. However, the absence of LA enlargement and of Kerley B lines and the demonstration of fixed splitting of S2 all favor atrial septal defect over MS.
Left atrial myxoma may obstruct LA emptying, causing dyspnea, a diastolic murmur, and hemodynamic changes resembling those of MS. However, patients with an LA myxoma often have features suggestive of a systemic disease, such as weight loss, fever, anemia, systemic emboli, and elevated serum IgG and interleukin 6 (IL-6) concentrations. The auscultatory findings may change markedly with body position. The diagnosis can be established by the demonstration of a characteristic echo-producing mass in the LA with TTE.
Cardiac Catheterization
Left and right heart catheterization is useful when there is a discrepancy between the clinical and TTE findings that cannot be resolved with either TEE or cardiac magnetic resonance (CMR) imaging. The growing experience with CMR for the assessment of patients with valvular heart disease may decrease the need for invasive catheterization. Catheterization is helpful in assessing associated lesions such as aortic stenosis (AS) and AR. Catheterization and coronary arteriography are not usually necessary to aid in the decision about surgery in younger patients, with typical findings of severe obstruction on clinical examination and TTE. In males over 45 years of age, females over 55 years of age, and younger patients with coronary risk factors, especially those with positive noninvasive stress tests for myocardial ischemia, coronary angiography is advisable preoperatively to detect patients with critical coronary obstructions that should be bypassed at the time of operation. Computed tomographic angiography (CTA) is now used in some centers to screen preoperatively for the presence of coronary artery disease (CAD) in patients with valvular heart disease. Catheterization and left ventriculography are also indicated in most patients who have undergone PMBV or previous mitral valve surgery and who have redeveloped serious symptoms, if questions remain after both TTE and TEE.
Treatment
Management strategy for patients with mitral stenosis (MS) and mild symptoms. There is controversy as to whether patients with severe MS (MVA <1.0>2) and severe pulmonary hypertension(PH) (PASP >60 mmHg) should undergo percutaneous mitral balloon valvotomy (PMBV) or mitral valve replacement (MVR) to prevent right ventricular failure. CXR, chest x-ray; ECG, electrocardiogram; echo, echocardiography; LA, left atrial; MR, mitral regurgitation; MVA, mitral valve area; MVG, mean mitral valve pressure gradient; NYHA, New York Heart Association; PASP, pulmonary artery systolic pressure; PAWP, pulmonary artery wedge pressure; 2D, 2-dimensional. (From Bonow et al.)
Penicillin prophylaxis of Group A β-hemolytic streptococcal infections to prevent rheumatic fever is important for at-risk patients with MS (Table 2). Recommendations for infective endocarditis prophylaxis have recently changed. In symptomatic patients, some improvement usually occurs with restriction of sodium intake and maintenance doses of oral diuretics. Digitalis glycosides usually do not benefit patients with MS and sinus rhythm, but they are helpful in slowing the ventricular rate of patients with AF. Beta blockers and nondihydropyridine calcium channel blockers (e.g., verapamil or diltiazem) are also useful in this regard. Warfarin to an international normalized ration (INR) of 2–3 should be administered indefinitely to patients with MS who have AF or a history of thromboembolism. The routine use of warfarin in patients in sinus rhythm with LA enlargement (maximal dimension >5.5 cm) with or without spontaneous echo contrast is more controversial.
If AF is of relatively recent onset in a patient whose MS is not severe enough to warrant PMBV or surgical commissurotomy, reversion to sinus rhythm pharmacologically or by means of electrical countershock is indicated. Usually, cardioversion should be undertaken after the patient has had at least 3 consecutive weeks of anticoagulant treatment to a therapeutic INR. If cardioversion is indicated more urgently, then intravenous heparin should be provided and a TEE performed to exclude the presence of left atrial thrombus before the procedure. Conversion to sinus rhythm is rarely successful or sustained in patients with severe MS, particularly those in whom the LA is especially enlarged or in whom AF has been present for more than 1 year.
Unless there is a contraindication, mitral valvotomy is indicated in symptomatic [New York Heart Association (NYHA) Functional Class II–IV] patients with isolated MS whose effective orifice (valve area) is < ~1.0 cm2/m2 body surface area, or <1.5>2 in normal-sized adults. Mitral valvotomy can be carried out by two techniques: PMBV and surgical valvotomy. In PMBV (Figs. 2 and 3), a catheter is directed into the LA after transseptal puncture, and a single balloon is directed across the valve and inflated in the valvular orifice. Ideal patients have relatively pliable leaflets with little or no commissural calcium. In addition, the subvalvular structures should not be significantly scarred or thickened and there should be no left atrial thombus. The short- and long-term results of this procedure in appropriate patients are similar to those of surgical valvotomy, but with less morbidity and a lower periprocedural mortality rate. Event-free survival in younger (<45>
Inoue balloon technique for mitral balloon valvotomy.A. After transseptal puncture, the deflated balloon catheter is advanced across the inter-atrial septum, then across the mitral valve and into the left ventricle. B. The balloon is then inflated stepwise within the mitral orifice.
Simultaneous left atrial (LA) and left ventricular (
Transthoracic echocardiography is helpful in identifying patients for the percutaneous procedure, and TEE is performed routinely to exclude left atrial thrombus. An "echo score" has been developed to help guide decision-making. The score accounts for the degree of leaflet thickening, calcification, and mobility, and for the extent of subvalvular thickening. A lower score predicts a higher likelihood of successful PMBV.
In patients in whom PMBV is not possible or unsuccessful, or in many patients with restenosis, an "open" valvotomy using cardiopulmonary bypass is necessary. In addition to opening the valve commissures, it is important to loosen any subvalvular fusion of papillary muscles and chordae tendineae and to remove large deposits of calcium, thereby improving valvular function, as well as to remove atrial thrombi. The perioperative mortality rate is ~2%.
Successful valvotomy is defined by a 50% reduction in the mean mitral valve gradient and a doubling of the mitral valve area. Successful valvotomy, whether balloon or surgical, usually results in striking symptomatic and hemodynamic improvement and prolongs survival. However, there is no evidence that the procedure improves the prognosis of patients with slight or no functional impairment. Therefore, unless recurrent systemic embolization or severe pulmonary hypertension has occurred (PA systolic pressures >50 mmHg at rest or >60 mmHg with exercise), valvotomy is not recommended for patients who are entirely asymptomatic and/or who have mild stenosis (mitral valve area >1/5 cm2). When there is little symptomatic improvement after valvotomy, it is likely that the procedure was ineffective, that it induced MR, or that associated valvular or myocardial disease was present. About half of all patients undergoing surgical mitral valvotomy require reoperation by 10 years. In the pregnant patient with MS, valvotomy should be carried out if pulmonary congestion occurs despite intensive medical treatment. PMBV is the preferred strategy in this setting and is performed with TEE and no or minimal x-ray exposure.
Mitral valve replacement (MVR) is necessary in patients with MS and significant associated MR, those in whom the valve has been severely distorted by previous transcatheter or operative manipulation, or those in whom the surgeon does not find it possible to improve valve function significantly. MVR is now routinely performed with preservation of the chordal attachments to optimize
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| aData are for calendar year 2004, in which 594 sites reported a total of 232,050 procedures. Data are available from the Society of Thoracic Surgeons at http://www.sts.org/sections/stsnationaldatabase/publications/executive/article.html. Abbreviations: AVR, aortic valve replacement; CAB, coronary artery bypass; MVR, mitral valve replacement; MVP, mitral valve repair; TV surgery, tricuspid valve repair and replacement; PV surgery, pulmonic valve repair and replacement. |
MITRAL REGURGITATION
MR may result from an abnormality or disease process that affects any one or more of the five functional components of the mitral valve apparatus (leaflets, annulus, chordae tendineae, papillary muscles, and subjacent myocardium) (Table 1). Acute MR can occur in the setting of acute myocardial infarction (MI) with papillary muscle rupture, following blunt chest wall trauma, or during the course of infective endocarditis. With acute MI, the posteromedial papillary muscle is involved much more frequently than the anterolateral papillary muscle because of its singular blood supply. Transient, acute MR can occur during periods of active ischemia and bouts of angina pectoris. Rupture of chordae tendineae can result in "acute on chronic MR" in patients with myxomatous degeneration of the valve apparatus.
Chronic MR can result from rheumatic disease, mitral valve prolapse (MVP) (see "Mitral Valve Prolapse"), extensive mitral annular calcification, congenital valve defects, hypertrophic obstructive cardiomyopathy (HOCM), and dilated cardiomyopathy. Rheumatic heart disease is the cause of chronic MR in only about one-third of cases and occurs more frequently in males. The rheumatic process produces rigidity, deformity, and retraction of the valve cusps and commissural fusion, as well as shortening, contraction, and fusion of the chordae tendineae. The MR associated with both MVP and HOCM is usually dynamic in nature. MR in HOCM occurs as a consequence of anterior papillary muscle displacement and systolic anterior motion of the anterior mitral valve leaflet into the narrowed
Irrespective of cause, chronic severe MR is often progressive, since enlargement of the LA places tension on the posterior mitral leaflet, pulling it away from the mitral orifice and thereby aggravating the valvular dysfunction. Similarly, LV dilatation increases the regurgitation, which in turn enlarges the LA and LV further, causing chordal rupture and resulting in a vicious circle; hence the aphorism "mitral regurgitation begets mitral regurgitation."
The resistance to
During early diastole, as the distended LA empties, there is a particularly rapid y descent in the absence of accompanying MS. A brief, early diastolic LA-LV pressure gradient [often generating a rapid filling sound (S3) and mid-diastolic murmur masquerading as MS] may occur in patients with pure MR as a result of the very rapid flow of blood across a normal-sized mitral orifice.
Quantitative estimates of left ventricular ejection fraction (LVEF), CO, PA pressure, regurgitant volume, regurgitant fraction (RF), and the effective regurgitant orifice area can be obtained during a careful Doppler echocardiographic examination. These measurements can also be obtained with CMR. Left and right heart catheterization with contrast ventriculography is utilized less frequently. Severe MR is defined by a regurgitant volume >60 mL/beat, regurgitant fraction (RF) >50%, and effective regurgitant orifice area >0.40 cm2.
In acute severe MR, the regurgitant volume is delivered into a normal-sized LA having normal or reduced compliance. As a result, LA pressures rise markedly for any increase in LA volume. The v wave in the LA pressure pulse is usually prominent (see Fig. 223-3), LA and pulmonary venous pressures are markedly elevated, and pulmonary edema is common. Because of the rapid rise in LA pressures during ventricular systole, the murmur of acute MR is early in timing and decrescendo in configuration, as a reflection of the progressive diminution in the LV-LA pressure gradient.
Patients with chronic severe MR, on the other hand, develop marked LA enlargement and increased LA compliance with little if any increase in LA and pulmonary venous pressures for any increase in LA volume. The LA v wave is relatively less prominent. The murmur of chronic MR is classically holosystolic in timing and plateau in configuration, as a reflection of the near-constant LV-LA pressure gradient. These patients usually complain of severe fatigue and exhaustion secondary to a low CO, while symptoms resulting from pulmonary congestion are less prominent initially; AF is almost invariably present once the LA dilates significantly.
Most common are patients whose clinical and hemodynamic features are intermediate between those in the two aforementioned groups.
Patients with chronic mild-to-moderate isolated MR are usually asymptomatic. This form of
In patients with chronic severe MR, the arterial pressure is usually normal, though the arterial pulse may show a sharp upstroke. A systolic thrill is often palpable at the cardiac apex, the
In patients with acute severe MR, the arterial pressure may be reduced with a narrow pulse pressure, the jugular venous pressure and wave forms may be normal or increased and exaggerated, the apical impulse is not displaced, and signs of pulmonary congestion are prominent.
The S1 is generally absent, soft, or buried in the holosystolic murmur of chronic MR. In patients with severe MR, the aortic valve may close prematurely, resulting in wide but physiologic splitting of S2. A low-pitched S3 occurring 0.12–0.17 s after the aortic valve closure sound, i.e., at the completion of the rapid-filling phase of the
A systolic murmur of at least grade III/VI intensity is the most characteristic auscultatory finding in chronic severe MR. It is usually holosystolic (see Fig. 220-4), but as previously noted it is decrescendo and ceases in mid- to late systole in patients with acute severe MR. The systolic murmur of chronic MR is usually most prominent at the apex and radiates to the axilla. However, in patients with ruptured chordae tendineae or primary involvement of the posterior mitral leaflet with prolapse or flail, the regurgitant jet is eccentric, directed anteriorly, and strikes the LA wall adjacent to the aortic root. In this situation, the systolic murmur is transmitted to the base of the heart and therefore may be confused with the murmur of AS. In patients with ruptured chordae tendineae, the systolic murmur may have a cooing or "sea gull" quality, while a flail leaflet may cause a murmur with a musical quality. The systolic murmur of chronic MR not due to MVP is intensified by isometric exercise (handgrip) but is reduced during the strain phase of the Valsalva maneuver.
In patients with sinus rhythm, there is evidence of LA enlargement, but RA enlargement also may be present when pulmonary hypertension is severe. Chronic severe MR is generally associated with AF. In many patients there is no clear-cut ECG evidence of enlargement of either ventricle. In others, the signs of
TTE with Doppler imaging is indicated to assess the mechanism of the MR and its hemodynamic severity.
The LA and
Management strategy for patients with chronic severe mitral regurgitation. *Mitral valve (MV) repair may be performed in asymptomatic patients with normal left ventricular (Medical
The management of chronic severe MR depends to some degree on its cause. Warfarin should be provided once AF intervenes with a target INR of 2–3. Cardioversion should be considered depending on the clinical context and left atrial size. In contrast to the acute setting, there are no large, long-term prospective studies to substantiate the use of vasodilators for the treatment of chronic, isolated severe MR in the absence of systemic hypertension. The severity of MR in the setting of an ischemic or nonischemic dilated cardiomyopathy may diminish with aggressive, evidence-based treatment of heart failure, including the use of diuretics, beta blockers, ACE inhibitors, and digitalis. Asymptomatic patients with severe MR in sinus rhythm with normal
Patients with acute severe MR require urgent stabilization and preparation for surgery. Diuretics, intravenous vasodilators (particularly sodium nitroprusside), and even intraaortic balloon counterpulsation may be needed for patients with post-MI papillary muscle rupture or other forms of acute severe MR.
In the selection of patients with chronic severe MR for surgical treatment, the often slowly progressive nature of the condition must be balanced against the immediate and long-term risks associated with operation. These risks are significantly lower for primary valve repair than for valve replacement (Table 3). Repair usually consists of valve reconstruction utilizing a variety of valvuloplasty techniques and insertion of an annuloplasty ring. Repair spares the patient the long-term adverse consequences of valve replacement, i.e., thromboembolic and hemorrhagic complications in the case of mechanical prostheses and late valve failure necessitating repeat valve replacement in the case of bioprostheses (see "Valve Replacement"). In addition, by preserving the integrity of the papillary muscles, subvalvular apparatus, and chordae tendineae, mitral repair and valvuloplasty maintain
Surgery for chronic severe MR is indicated once symptoms occur, especially if valve repair is feasible (Fig. 4). Other indications for early consideration of mitral valve repair include recent-onset AF and pulmonary hypertension, defined as a PA pressure 
50 mmHg at rest or 60 mmHg with exercise. Surgical treatment of chronic severe MR is indicated for asymptomatic patients when
In patients with significantly impaired
Patients with acute severe MR can often be stabilized temporarily with appropriate medical therapy, but surgical correction will be necessary, emergently in the case of papillary muscle rupture and within days to weeks in most other settings.
Mitral Valve Prolapse
MVP, also variously termed the systolic click-murmur syndrome, Barlow's syndrome, floppy-valve syndrome, and billowing mitral leaflet syndrome, is a relatively common but highly variable clinical syndrome resulting from diverse pathogenic mechanisms of the mitral valve apparatus. Among these are excessive or redundant mitral leaflet tissue, which is commonly associated with myxomatous degeneration and greatly increased concentrations of acid mucopolysaccharide.
In most patients with MVP, the cause is unknown, but in some it appears to be a genetically determined collagen disorder. A reduction in the production of type III collagen has been incriminated, and electron microscopy has revealed fragmentation of collagen fibrils.
MVP is a frequent finding in patients with heritable disorders of connective tissue, including Marfan syndrome, osteogenesis imperfecta, and Ehler-Danlos syndrome.
MVP may be associated with thoracic skeletal deformities similar to but not as severe as those in Marfan syndrome, encompassing a high-arched palate and alterations of the chest and thoracic spine, including the so-called straight back syndrome.
In most patients with MVP, myxomatous degeneration is confined to the mitral (or, less commonly, the tricuspid or aortic) valves without other clinical or pathologic manifestations of disease. The posterior leaflet is usually more affected than the anterior, and the mitral valve annulus is often greatly dilated. In many patients, elongated, redundant, or ruptured chordae tendineae cause or contribute to the regurgitation.
MVP also may occur rarely as a sequel to acute rheumatic fever, in ischemic heart disease, and in various cardiomyopathies, as well as in 20% of patients with ostium secundum atrial septal defect.
MVP may lead to excessive stress on the papillary muscles, which in turn leads to dysfunction and ischemia of the papillary muscles and the subjacent ventricular myocardium. Rupture of chordae tendineae and progressive annular dilatation and calcification also contribute to valvular regurgitation, which then places more stress on the diseased mitral valve apparatus, thereby creating a vicious circle. The ECG changes (see below) and ventricular arrhythmias appear to result from regional ventricular dysfunction related to increased stress placed on the papillary muscles.
MVP is more common in females and occurs most commonly between the ages of 15 and 30 years; the clinical course is often benign. MVP may also be observed in older (>50 years) patients, often males, in whom MR is often more severe and requires surgical treatment. There is an increased familial incidence for some patients, suggesting an autosomal dominant form of inheritance. MVP encompasses a broad spectrum of severities, ranging from only a systolic click and murmur and mild prolapse of the posterior leaflet of the mitral valve to severe MR due to chordal rupture and massive prolapse of both leaflets. In many patients this condition progresses over years or decades. In others it worsens rapidly as a result of chordal rupture or endocarditis.
Most patients are asymptomatic and remain so for their entire lives. However, in North America MVP is now the most common cause of isolated severe MR requiring surgical treatment. Arrhythmias, most commonly ventricular premature contractions and paroxysmal supraventricular and ventricular tachycardia, as well as AF, have been reported and may cause palpitations, light-headedness, and syncope. Sudden death is a very rare complication and occurs most often in patients with severe MR and depressed
The most important finding is the mid- or late (nonejection) systolic click, which occurs 0.14 s or more after the S1 and is thought to be generated by the sudden tensing of slack, elongated chordae tendineae or by the prolapsing mitral leaflet when it reaches its maximum excursion. Systolic clicks may be multiple and may be followed by a high-pitched, late systolic crescendo-decrescendo murmur, which occasionally is "whooping" or "honking" and is heard best at the apex. The click and murmur occur earlier with standing, during the strain of the Valsalva maneuver, and with any intervention that decreases
The ECG most commonly is normal but may show biphasic or inverted T waves in leads II, III, and aVF, and occasionally supraventricular or ventricular premature beats. TTE is particularly effective in identifying the abnormal position and prolapse of the mitral valve leaflets. A useful echocardiographic definition of MVP is systolic displacement (in the parasternal long axis view) of the mitral valve leaflets by at least 2 mm into the LA superior to the plane of the mitral annulus. Color flow and continuous wave Doppler imaging is helpful in revealing and evaluating associated MR. TEE is indicated when more accurate information is required and is performed routinely for intraoperative guidance for valve repair. Invasive left ventriculography is rarely necessary but can also show prolapse of the posterior and sometimes of both mitral valve leaflets.
Mitral Valve Prolapse: Treatment
Aortic Stenosis
AS occurs in about one-fourth of all patients with chronic valvular heart disease; approximately 80% of adult patients with symptomatic valvular AS are male.
AS in adults may be due to degenerative calcification of the aortic cusps. It may be congenital in origin or it may be secondary to rheumatic inflammation. Age-related degenerative calcific AS (also known as senile or sclerocalcific AS) is now the most common cause of AS in adults in North America and
The congenitally affected valve may be stenotic at birth and may become progressively more fibrotic, calcified, and stenotic. In other cases the valve may be congenitally deformed, usually bicuspid [bicuspid aortic valve (BAV)], without serious narrowing of the aortic orifice during childhood; its abnormal architecture makes its leaflets susceptible to otherwise ordinary hemodynamic stresses, which ultimately lead to valvular thickening, calcification, increased rigidity, and narrowing of the aortic orifice.
Rheumatic disease of the aortic leaflets produces commissural fusion, sometimes resulting in a bicuspid-appearing valve. This condition in turn makes the leaflets more susceptible to trauma and ultimately leads to fibrosis, calcification, and further narrowing. By the time the obstruction to
Other Forms of Obstruction to Left Ventricular Outflow
Besides valvular AS, three other lesions may be responsible for obstruction to
The obstruction to
A mean systolic pressure gradient >40 mmHg with a normal CO or an effective aortic orifice area < ~1.0 cm2 (or ~<0.6>2/m2 body surface area in a normal-sized adult)—i.e., less than approximately one-third of the normal orifice—is generally considered to represent severe obstruction to
The hypertrophied
AS is rarely of clinical importance until the valve orifice has narrowed to approximately 1.0 cm2. Even severe AS may exist for many years without producing any symptoms because of the ability of the hypertrophied
Most patients with pure or predominant AS have gradually increasing obstruction for years but do not become symptomatic until the sixth to eighth decades. Exertional dyspnea, angina pectoris, and syncope are the three cardinal symptoms. Often there is a history of insidious progression of fatigue and dyspnea associated with gradual curtailment of activities. Dyspnea results primarily from elevation of the pulmonary capillary pressure caused by elevations of
Since the CO at rest is usually well maintained until late in the course, marked fatigability, weakness, peripheral cyanosis, cachexia, and other clinical manifestations of a low CO are usually not prominent until this stage is reached. Orthopnea, paroxysmal nocturnal dyspnea, and pulmonary edema, i.e., symptoms of
When AS and MS coexist, the reduction in CO induced by MS lowers the pressure gradient across the aortic valve and thereby masks many of the clinical findings produced by AS.
The rhythm is generally regular until late in the course; at other times, AF should suggest the possibility of associated mitral valve disease. The systemic arterial pressure is usually within normal limits. In the late stages, however, when stroke volume declines, the systolic pressure may fall and the pulse pressure narrow. The peripheral arterial pulse rises slowly to a delayed sustained peak (pulsus parvus et tardus; see Fig. 220-2). In the elderly, the stiffening of the arterial wall may mask this important physical sign. In many patients the a wave in the jugular venous pulse is accentuated. This results from the diminished distensibility of the RV cavity caused by the bulging, hypertrophied interventricular septum.
The
An early systolic ejection sound is frequently audible in children and adolescents with congenital noncalcific valvular AS. This sound usually disappears when the valve becomes calcified and rigid. As AS increases in severity,
The murmur of AS is characteristically an ejection (mid) systolic murmur that commences shortly after the S1, increases in intensity to reach a peak toward the middle of ejection, and ends just before aortic valve closure (see Fig. 220-4). It is characteristically low-pitched, rough and rasping in character, and loudest at the base of the heart, most commonly in the second right intercostal space. It is transmitted upward along the carotid arteries. Occasionally it is transmitted downward and to the apex, where it may be confused with the systolic murmur of MR (Gallavardin effect). In almost all patients with severe obstruction and preserved CO, the murmur is at least grade III/VI. In patients with mild degrees of obstruction or in those with severe stenosis with heart failure in whom the stroke volume and therefore the transvalvular flow rate are reduced, the murmur may be relatively soft and brief.
In most patients with severe AS there is
The key findings are
Echocardiography is useful for identifying coexisting valvular abnormalities such as MS and AR, which sometimes accompany AS; for differentiating valvular AS from other forms of outflow obstruction; and for measurement of the aortic root. Aneurysmal enlargement (maximal dimension >4.5 cm) of the root or ascending aorta can occur in up to 20% of patients with bicuspid aortic valve disease, independent of the severity of the valve lesion. Dobutamine stress echocardiography is useful for the evaluation of patients with severe AS and severe
The chest x-ray may show no or little overall cardiac enlargement for many years. Hypertrophy without dilatation may produce some rounding of the cardiac apex in the frontal projection and slight backward displacement in the lateral view; severe AS is often associated with poststenotic dilatation of the ascending aorta. As noted above, however, aortic enlargement may be an independent process and mediated by the same type of structural changes that occur in patients with Marfan syndrome. Aortic calcification is usually readily apparent on fluoroscopic examination or by echocardiography; the absence of valvular calcification in an adult suggests that severe valvular AS is not present. In later stages of the disease, as the
Right and left heart catheterization for invasive assessment of AS is performed infrequently but can be useful when there is a discrepancy between the clinical and echocardiographic findings. Concerns have been raised that attempts to cross the aortic valve for measurement of left ventricular pressures are associated with a risk of cerebral embolization. Catheterization is also useful in three distinct categories of patients: (1) patients with multivalvular disease, in whom the role played by each valvular deformity should be defined to aid in the planning of definitive operative treatment; (2) young, asymptomatic patients with noncalcific congenital AS, to define with precision the severity of obstruction to LV outflow, since operation [which does not usually require aortic valve replacement (AVR)] or PABV may be indicated if severe AS is present, even in the absence of symptoms; balloon valvotomy may follow left heart catheterization immediately; and (3) patients in whom it is suspected that the obstruction to LV outflow may not be at the aortic valve but rather in the sub- or supravalvular regions.
Coronary angiography is indicated to detect or exclude CAD in patients >45 years old with severe AS who are being considered for operative treatment. The incidence of significant CAD for which bypass grafting is indicated at the time of AVR exceeds 50% among adult patients.
Death in patients with severe AS occurs most commonly in the seventh and eighth decades. Based on data obtained at postmortem examination in patients before surgical treatment became widely available, the average time to death after the onset of various symptoms was as follows: angina pectoris, 3 years; syncope, 3 years; dyspnea, 2 years; congestive heart failure, 1.5–2 years. Moreover, in >80% of patients who died with AS, symptoms had existed for <4>2/year and an annual increase in mean gradient averaging 7 mmHg/year.
Management strategy for patients with severe aortic stenosis. Preoperative coronary angiography should be performed routinely as determined by age, symptoms, and coronary risk factors. Cardiac catheterization and angiography may also be helpful when there is discordance between clinical findings and echocardiography. AVA, aortic valve area; BP, blood pressure; CABG, coronary artery bypass graft surgery; echo, echocardiography; LV, left ventricle; Vmax, maximal velocity across aortic valve by Doppler echocardiography. (From Bonow et al. Modified from CM Otto: J Am Coll Cardiol 47:2141, 2006.)
Medical Treatment
In patients with severe AS (<1.0>2), strenuous physical activity should be avoided, even in the asymptomatic stage. Care must be taken to avoid dehydration and hypovolemia to protect against a significant reduction in CO. Medications used for the treatment of hypertension or CAD, including beta blockers and ACE inhibitors, are generally safe for asymptomatic patients with preserved left ventricular systolic function. Nitroglycerin is helpful in relieving angina pectoris. Retrospective studies have shown that patients with degenerative calcific AS who receive HMG-CoA reductase inhibitors ("statins") exhibit slower progression of leaflet calcification and aortic valve area reduction than those who do not. One prospective randomized clinical trial using high-dose atorvastatin failed to show a measurable benefit, although a more recent trial using rosuvastatin did show a beneficial effect. The role of statin medications may be more clearly defined with further study.
Asymptomatic patients with calcific AS and severe obstruction should be followed carefully for the development of symptoms and by serial echocardiograms for evidence of deteriorating
Operation should, if possible, be carried out before frank
Because many patients with calcific AS are elderly, particular attention must be directed to the adequacy of hepatic, renal, and pulmonary function before AVR is recommended. Age alone is not a contraindication to AVR for AS. The mortality rate depends to a substantial extent on the patient's preoperative clinical and hemodynamic state. The 10-year survival rate of patients with AVR is approximately 60%. Approximately 30% of bioprosthetic valves evidence primary valve failure in 10 years, requiring re-replacement, and an approximately equal percentage of patients with mechanical prostheses develop significant hemorrhagic complications as a consequence of treatment with anticoagulants (see "Valve Replacement").
Percutaneous Balloon Aortic Valvuloplasty
Aortic Regurgitation
AR may be caused by primary valve disease or by primary aortic root disease.
In approximately two-thirds of patients with valvular AR, the disease is rheumatic in origin, resulting in thickening, deformity, and shortening of the individual aortic valve cusps, changes that prevent their proper opening during systole and closure during diastole. A rheumatic origin is much less common in patients with isolated AR who do not have associated mitral valve disease. Patients with congenital BAV disease may develop predominant AR. Congenital fenestrations of the aortic valve occasionally produce mild AR. Membranous subaortic stenosis often leads to thickening and scarring of the aortic valve leaflets with secondary AR. Prolapse of an aortic cusp, resulting in progressive chronic AR, occurs in approximately 15% of patients with ventricular septal defect but may also occur as an isolated phenomenon or as a consequence of myxomatous degeneration sometimes associated with mitral (see "Mitral Valve Prolapse") and/or tricuspid valve involvement.
AR may result from infective endocarditis, which can develop on a valve previously affected by rheumatic disease, a congenitally deformed valve, or, rarely, on a normal aortic valve, and may lead to perforation or erosion of one or more leaflets. The aortic valve leaflets may become scarred and retracted during the course of syphilis or ankylosing spondylitis and contribute further to the AR that derives primarily from the associated root disease. Although traumatic rupture or avulsion of the aortic valve is an uncommon cause of acute AR, it does represent the most frequent serious lesion in patients surviving nonpenetrating cardiac injuries. The coexistence of hemodynamically significant AS with AR usually excludes all the rarer forms of AR because it occurs almost exclusively in patients with rheumatic or congenital AR. In patients with AR due to primary valvular disease, dilatation of the aortic annulus may occur secondarily and intensify the regurgitation.
AR may also be due entirely to marked aortic dilatation, i.e., aortic root disease, without primary involvement of the valve leaflets; widening of the aortic annulus and separation of the aortic leaflets are responsible for the AR. Cystic medial degeneration of the ascending aorta, which may or may not be associated with other manifestations of Marfan syndrome; idiopathic dilatation of the aorta; annulo-aortic ectasia; osteogenesis imperfecta; and severe hypertension may all widen the aortic annulus and lead to progressive AR. Occasionally AR is caused by retrograde dissection of the aorta involving the aortic annulus. Syphilis and ankylosing spondylitis, both of which may affect aortic valves, may also be associated with cellular infiltration and scarring of the media of the thoracic aorta, leading to aortic dilatation, aneurysm formation, and severe regurgitation. In syphilis of the aorta, now a very rare condition, the involvement of the intima may narrow the coronary ostia, which in turn may be responsible for myocardial ischemia.
The total stroke volume ejected by the
The reverse pressure gradient from aorta to
In patients with chronic severe AR, the effective forward CO usually is normal or only slightly reduced at rest, but often it fails to rise normally during exertion. Early signs of
Myocardial ischemia may occur in patients with AR because myocardial oxygen requirements are elevated by
Approximately three-fourths of patients with pure or predominant valvular AR are males; females predominate among patients with primary valvular AR who have associated mitral valve disease. A history compatible with infective endocarditis may sometimes be elicited from patients with rheumatic or congenital involvement of the aortic valve, and the infection often precipitates or seriously aggravates preexisting symptoms.
In patients with acute severe AR, as may occur in infective endocarditis, aortic dissection, or trauma, the
Chronic severe AR may have a long latent period, and patients may remain relatively asymptomatic for as long as 10–15 years. However, uncomfortable awareness of the heartbeat, especially on lying down, may be an early complaint. Sinus tachycardia, during exertion or with emotion, or premature ventricular contractions may produce particularly uncomfortable palpitations as well as head pounding. These complaints may persist for many years before the development of exertional dyspnea, usually the first symptom of diminished cardiac reserve. The dyspnea is followed by orthopnea, paroxysmal nocturnal dyspnea, and excessive diaphoresis. Anginal chest pain occurs frequently in patients with severe AR, even in younger patients, and it is not necessary to invoke the presence of CAD to explain this symptom in patients with severe AR. Anginal pain may develop at rest as well as during exertion. Nocturnal angina may be a particularly troublesome symptom, and it may be accompanied by marked diaphoresis. The anginal episodes can be prolonged and often do not respond satisfactorily to sublingual nitroglycerin. Systemic fluid accumulation, including congestive hepatomegaly and ankle edema, may develop late in the course of the disease.
In chronic severe AR, the jarring of the entire body and the bobbing motion of the head with each systole can be appreciated, and the abrupt distention and collapse of the larger arteries are easily visible. The examination should be directed toward the detection of conditions predisposing to AR, such as Marfan syndrome, ankylosing spondylitis, and ventricular septal defect.
A rapidly rising "water-hammer" pulse, which collapses suddenly as arterial pressure falls rapidly during late systole and diastole (Corrigan's pulse), and capillary pulsations, an alternate flushing and paling of the skin at the root of the nail while pressure is applied to the tip of the nail (Quincke's pulse), are characteristic of free AR. A booming "pistol-shot" sound can be heard over the femoral arteries (Traube's sign), and a to-and-fro murmur (Duroziez's sign) is audible if the femoral artery is lightly compressed with a stethoscope.
The arterial pulse pressure is widened, and there is an elevation of the systolic pressure, sometimes to as high as 300 mmHg, and a depression of the diastolic pressure. The measurement of arterial diastolic pressure with a sphygmomanometer may be complicated by the fact that systolic sounds are frequently heard with the cuff completely deflated. However, the level of cuff pressure at the time of muffling of the Korotkoff sounds (Phase IV) generally corresponds fairly closely to the true intraarterial diastolic pressure. As the disease progresses and the
In patients with chronic severe AR, the
In patients with severe AR, the aortic valve closure sound (A2) is usually absent. An S3 and systolic ejection sound are frequently audible, and occasionally an S4 also may be heard. The murmur of chronic AR is typically a high-pitched, blowing, decrescendo diastolic murmur, heard best in the third intercostal space along the left sternal border (see Fig. 220-4B). In patients with mild AR, this murmur is brief but, as the severity increases, generally becomes louder and longer, indeed holodiastolic. When the murmur is soft, it can be heard best with the diaphragm of the stethoscope and with the patient sitting up, leaning forward, and with the breath held in forced expiration. In patients in whom the AR is caused by primary valvular disease, the diastolic murmur is usually louder along the left than the right sternal border. However, when the murmur is heard best along the right sternal border, it suggests that the AR is caused by aneurysmal dilatation of the aortic root. "Cooing" or musical diastolic murmurs suggest eversion of an aortic cusp vibrating in the regurgitant stream.
A mid-systolic ejection murmur is frequently audible in isolated AR. It is generally heard best at the base of the heart and is transmitted along the carotid vessels. This murmur may be quite loud without signifying aortic obstruction. A third murmur frequently heard in patients with severe AR is the Austin Flint murmur, a soft, low-pitched, rumbling mid-diastolic murmur. It is probably produced by the diastolic displacement of the anterior leaflet of the mitral valve by the AR stream but does not appear to be associated with hemodynamically significant mitral obstruction. The auscultatory features of AR are intensified by strenuous handgrip, which augments systemic resistance.
In acute severe AR, the elevation of
In patients with chronic severe AR, the ECG signs of
The extent and velocity of wall motion are normal or even supernormal, until myocardial contractility declines. A rapid, high-frequency fluttering of the anterior mitral leaflet produced by the impact of the regurgitant jet is a characteristic finding. The echocardiogram is also useful in determining the cause of AR, by detecting dilatation of the aortic annulus and root or aortic dissection (see Fig. 222-3). Thickening and failure of coaptation of the leaflets also may be noted. Color flow Doppler echocardiographic imaging is very sensitive in the detection of AR, and Doppler echocardiography is helpful in assessing its severity. With severe AR, the central jet width exceeds 65% of the left ventricular outflow tract, the regurgitant volume is >60 ml/beat, the regurgitant fraction is >50%, and there is diastolic flow reversal in the proximal descending thoracic aorta. The continuous wave Doppler profile shows a rapid deceleration time in patients with acute severe AR, due to the rapid increase in
In chronic severe AR, the apex is displaced downward and to the left in the frontal projection. In the left anterior oblique and lateral projections, the
Cardiac Catheterization and Angiography
When needed, right and left heart catheterization with contrast aortography can provide accurate confirmation of the magnitude of regurgitation and the status of
Aortic Regurgitation: Treatment
Management strategy for patients with chronic severe aortic regurgitation. Preoperative coronary angiography should be performed routinely, as determined by age, symptoms, and coronary risk factors. Cardiac catheterization and angiography may also be helpful when there is discordance between clinical findings and echocardiography. "Stable" refers to stable echocardiographic measurements. In some centers, serial follow-up may be performed with radionuclide ventriculography (RVG) or magnetic resonance imaging (MRI) rather than echocardiography (echo) to assess left ventricular (Acute Aortic Regurgitation
Patients with acute severe AR may respond to intravenous diuretics and vasodilators (such as sodium nitroprusside), but stabilization is usually short-lived and operation is indicated urgently. Intraaortic balloon counterpulsation is contraindicated. Beta-blockers are also best avoided so as not to reduce the CO further or slow the heart rate, which might allow proportionately more time in diastole for regurgitation to occur. Surgery is the treatment of choice.
Early symptoms of dyspnea and effort intolerance respond to treatment with diuretics and vasodilators (ACE inhibitors, dihydropyridine calcium channel blockers, or hydralazine) may be useful as well. Surgery can then be performed in more controlled circumstances. The use of vasodilators to extend the compensated phase of chronic severe AR before the onset of symptoms or the development of
In deciding on the advisability and proper timing of surgical treatment, two points should be kept in mind: (1) patients with chronic severe AR usually do not become symptomatic until after the development of myocardial dysfunction; and (2) when delayed too long (defined as >1 year from onset of symptoms or LV dysfunction), surgical treatment often does not restore normal LV function. Therefore, in patients with chronic severe AR, careful clinical follow-up and noninvasive testing with echocardiography at approximately 6-month intervals are necessary if operation is to be undertaken at the optimal time, i.e., after the onset of LV dysfunction but prior to the development of severe symptoms. Operation can be deferred as long as the patient both remains asymptomatic and retains normal
AVR is indicated for the treatment of severe AR in symptomatic patients irrespective of
Surgical options for management of aortic valve and root disease have expanded considerably over the past decade. AVR with a suitable mechanical or tissue prosthesis is generally necessary in patients with rheumatic AR and in many patients with other forms of regurgitation. Rarely, when a leaflet has been perforated during infective endocarditis or torn from its attachments to the aortic annulus by thoracic trauma, primary surgical repair may be possible. When AR is due to aneurysmal dilatation of the annulus and ascending aorta rather than to primary valvular involvement, it may be possible to reduce the regurgitation by narrowing the annulus or by excising a portion of the aortic root without replacing the valve. Resuspension of the native aortic valve leaflets is possible in approximately 50% of patients with acute AR in the setting of Type A aortic dissection. In other conditions, however, regurgitation can be eliminated only by replacing the aortic valve, excising the dilated or aneurysmal ascending aorta responsible for the regurgitation, and replacing it with a graft. This formidable procedure entails a higher risk than isolated AVR.
As in patients with other valvular abnormalities, both the operative risk and the late mortality are largely dependent on the stage of the disease and on myocardial function at the time of operation. The overall operative mortality for isolated AVR is about 3% (Table 3). However, patients with marked cardiac enlargement and prolonged
Tricuspid Stenosis
TS, much less prevalent than MS in North America and
A diastolic pressure gradient between the RA and RV defines TS. It is augmented when the transvalvular blood flow increases during inspiration and declines during expiration. A mean diastolic pressure gradient of 4 mmHg is usually sufficient to elevate the mean RA pressure to levels that result in systemic venous congestion. Unless sodium intake has been restricted and diuretics administered, this venous congestion is associated with hepatomegaly, ascites, and edema, sometimes severe. In patients with sinus rhythm, the RA a wave may be extremely tall and may even approach the level of the RV systolic pressure. The y descent is prolonged. The CO at rest is usually depressed, and it fails to rise during exercise. The low CO is responsible for the normal or only slightly elevated LA, PA, and RV systolic pressures despite the presence of MS. Thus, the presence of TS can mask the hemodynamic and clinical features of the MS, which usually accompanies it.
Since the development of MS generally precedes that of TS, many patients initially have symptoms of pulmonary congestion. Spontaneous improvement of these symptoms should raise the possibility that TS may be developing. Characteristically, patients complain of relatively little dyspnea for the degree of hepatomegaly, ascites, and edema that they have. However, fatigue secondary to a low CO and discomfort due to refractory edema, ascites, and marked hepatomegaly are common in patients with TS and/or TR. In some patients, TS may be suspected for the first time when symptoms of right-sided failure persist after an adequate mitral valvotomy.
Since TS usually occurs in the presence of other obvious valvular disease, the diagnosis may be missed unless it is considered and searched for. Severe TS is associated with marked hepatic congestion, often resulting in cirrhosis, jaundice, serious malnutrition, anasarca, and ascites. Congestive hepatomegaly and, in cases of severe tricuspid valve disease, splenomegaly are present. The jugular veins are distended, and in patients with sinus rhythm there may be giant a waves. The v waves are less conspicuous, and since tricuspid obstruction impedes RA emptying during diastole, there is a slow y descent. In patients with sinus rhythm there may be prominent presystolic pulsations of the enlarged liver as well.
On auscultation, an OS of the tricuspid valve may occasionally be heard approximately 0.06 s after pulmonic valve closure. The diastolic murmur of TS has many of the qualities of the diastolic murmur of MS, and since TS almost always occurs in the presence of MS, the less-common valvular lesion may be missed. However, the tricuspid murmur is generally heard best along the left lower sternal margin and over the xiphoid process, and it is most prominent during presystole in patients with sinus rhythm. The murmur of TS is augmented during inspiration, and it is reduced during expiration and particularly during the strain phase of the Valsalva maneuver, when tricuspid blood flow is reduced.
The ECG features of RA enlargement (see Fig. 221-8) include tall, peaked P waves in lead II, as well as prominent, upright P waves in lead V1. The absence of ECG evidence of right ventricular hypertrophy (RVH) in a patient with right-sided heart failure who is believed to have MS should suggest associated tricuspid valve disease. The chest x-ray in patients with combined TS and MS shows particular prominence of the RA and superior vena cava without much enlargement of the PA and with less evidence of pulmonary vascular congestion than occurs in patients with isolated MS. On echocardiographic examination, the tricuspid valve is usually thickened and domes in diastole; the transvalvular gradient can be estimated by Doppler echocardiography. TTE provides additional information regarding mitral valve structure and function,
Tricuspid Regurgitation
Most commonly, TR is functional and secondary to marked dilatation of the tricuspid annulus. Functional TR may complicate RV enlargement of any cause, including inferior wall infarcts that involve the RV. It is commonly seen in the late stages of heart failure due to rheumatic or congenital heart disease with severe pulmonary hypertension (pulmonary artery systolic pressure >55 mmHg), as well as in ischemic heart disease and dilated cardiomyopathy. It is reversible in part if pulmonary hypertension is relieved. Rheumatic fever may produce organic (primary) TR, often associated with TS. Infarction of RV papillary muscles, tricuspid valve prolapse, carcinoid heart disease, endomyocardial fibrosis, infective endocarditis, and trauma all may produce TR. Less commonly, TR results from congenitally deformed tricuspid valves, and it occurs with defects of the atrioventricular canal, as well as with Ebstein's malformation of the tricuspid valve. TR also develops eventually in patients with chronic RV apical pacing.
As is the case for TS, the clinical features of TR result primarily from systemic venous congestion and reduction of CO. With the onset of TR in patients with pulmonary hypertension, symptoms of pulmonary congestion diminish, but the clinical manifestations of right-sided heart failure become intensified. The neck veins are distended with prominent v waves and rapid y descents, marked hepatomegaly, ascites, pleural effusions, edema, systolic pulsations of the liver, and a positive hepatojugular reflux. A prominent RV pulsation along the left parasternal region and a blowing holosystolic murmur along the lower left sternal margin, which may be intensified during inspiration and reduced during expiration or the strain of the Valsalva maneuver (Carvallo's sign), are characteristic findings; AF is usually present.
The ECG usually shows changes characteristic of the lesion responsible for the enlargement of the RV that leads to TR, e.g., inferior wall myocardial infarction or severe RVH. Echocardiography may be helpful by demonstrating RV dilatation and prolapsing, flail, scarred, or displaced tricuspid leaflets; the diagnosis of TR can be made by color flow Doppler echocardiography, and its severity can be estimated by Doppler examination (see Fig. 222-4). Severe TR is accompanied by hepatic vein systolic flow reversal. Continuous wave Doppler is also useful in estimating PA pressure. Roentgenographic examination usually reveals enlargement of both the RA and RV.
In patients with severe TR, the CO is usually markedly reduced, and the RA pressure pulse may exhibit no x descent during early systole but a prominent c-v wave with a rapid y descent. The mean RA and the RV end-diastolic pressures are often elevated.
Tricuspid Regurgitation: Treatment
Pulmonic Valve Disease
The pulmonic valve is affected by rheumatic fever far less frequently than are the other valves, and it is uncommonly the seat of infective endocarditis. The most common acquired abnormality affecting the pulmonic valve is regurgitation secondary to dilatation of the pulmonic valve ring as a consequence of severe pulmonary hypertension. This produces the Graham Steell murmur, a high-pitched, decrescendo, diastolic blowing murmur along the left sternal border, which is difficult to differentiate from the far more common murmur produced by AR. Pulmonic regurgitation is usually of little hemodynamic significance; indeed, surgical removal or destruction of the pulmonic valve by infective endocarditis does not produce heart failure unless serious pulmonary hypertension is also present.
Valve Replacement
The results of replacement of any valve are dependent primarily on (1) the patient's myocardial function and general medical condition at the time of operation; (2) the technical abilities of the operative team and the quality of the postoperative care; and (3) the durability, hemodynamic characteristics, and thrombogenicity of the prosthesis. Increased perioperative mortality is associated with advanced age and comorbidity (e.g., pulmonary or renal disease, the need for nonvalvular cardiovascular surgery, diabetes mellitus) as well as with greater levels of preoperative functional disability and pulmonary hypertension. Late complications of valve replacement include paravalvular leakage, thromboemboli, bleeding due to anticoagulants, structural deterioration of the prosthesis, and infective endocarditis.
The considerations involved in the choice between a bioprosthetic (tissue) and artificial mechanical valve are similar in the mitral and aortic positions and in the treatment of stenotic, regurgitant, or mixed lesions. All patients who have undergone replacement of any valve with a mechanical prosthesis are at risk of thromboembolic complications and must be maintained permanently on anticoagulants, a treatment that imposes a hazard of hemorrhage. The primary advantage of bioprostheses over mechanical prostheses is the virtual absence of thromboembolic complications 3 months after implantation, and except for patients with chronic AF, few such instances have been associated with their use. The major disadvantage of bioprosthetic valves is their structural deterioration, the incidence of which is inversely proportional to the patient's age. This deterioration results in the need to replace the prosthesis in up to 30% of patients by 10 years and in 50% by 15 years. Rates of structural valve deterioration are higher for mitral than for aortic bioprostheses. This phenomenon may be due in part to the greater closing pressure to which a mitral prosthesis is exposed.
Traditionally, a mechanical prosthesis was considered preferable for a patient under age 65 who could take anticoagulation reliably. Bioprostheses were recommended for older patients (>65 years) who did not otherwise have an indication for anticoagulation (for example, AF). However, more recent surveys of cardiac surgery in the United States, as reflected in the Society of Thoracic Surgeons database, show a clear and progressive trend favoring the implantation of bioprosthetic valves in younger (<65>
Bioprostheses remain the preferred valve choice for patients >65 years, in both the aortic and mitral position. Bioprosthetic valves are also indicated for women who expect to become pregnant, as well as for others who refuse to take anticoagulation or for whom anticoagulation may be contraindicated. Types of bioprostheses include xenografts (i.e., porcine aortic valves; cryopreserved, mounted bovine pericardium), homograft (allograft) aortic valves obtained from cadavers, as well as pulmonary autografts transplanted into the aortic position. Homograft replacement may be preferred for the management of complicated aortic valve infective endocarditis.
Global Burden of Valvular Heart Disease
Primary valvular heart disease ranks well below coronary heart disease, stroke, hypertension, obesity, and diabetes as major threats to the public health. Nevertheless, it is the source of significant morbidity and mortality. Rheumatic fever is the dominant cause of valvular heart disease in developing countries. Its prevalence has been estimated to range from as low as 1.0 per 100,000 school-age children in
TS, a relatively uncommon valvular lesion in North America and Western Europe, is more common in tropical and subtropical climates, especially in southern Asia and in
As of the year 2000, worldwide death rates for rheumatic heart disease approximated 5.5 per 100,000 population (n = 332,000), with the highest rates reported from
The incidence of infective endocarditis has increased with the aging of the population, the more widespread prevalence of vascular grafts and intracardiac devices, the emergence of more virulent multidrug-resistant microorganisms, and the growing epidemic of diabetes. Infective endocarditis has become a more frequent cause of acute valvular regurgitation.
