Cardiology Core Curriculum A problem-based approach - part 7 ppt

Cardiology Core Curriculum Clinical detection Coarse systolic murmur Assessment of severity History, PE, CXR ECG, echo, ±catheterization AVA >1·0 cm2 AVA ≤1·0 cm2 Symptom status No angina, syncope, or CHF Angina, syncope, or CHF present Treatment Medical therapy Follow ≤q months Prophylaxis Valve replacement Figure 12.4 Timing of surgery for aortic stenosis The optimal timing of valve replacement for patients with aortic stenosis depends on the hemodynamic severity of the underlying lesion and the symptomatic status of the patient AVA, aortic valve area; CHF, congestive heart failure; CXR, chest x ray; ECG, electrocardiogram; echo, Doppler echocardiogram; PE, physical examination Mitral regurgitation Mitral regurgitation has many causes Irrespective of etiology, a portion of left ventricular output is ejected into the low pressure left atrium Cardiac output may be maintained at rest but is reduced during exercise, resulting in fatigue during exertion The optimal timing of surgery in mitral regurgitation is complicated and depends on several factors such as the etiology, acuity, and severity of regurgitation; degree of functional impairment; and left ventricular ejection fraction Etiology and natural history Normal functioning of the mitral valve depends on the coordinated action of each of its components including the leaflets, annulus, chordae, papillary muscles, and underlying left ventricular myocardium Disruption of normal function of any of these components may lead to mitral regurgitation (Box 12.1) In myxomatous degeneration the mitral leaflet tissue or chordae may be redundant, preventing precise coaptation of leaflet edges In rheumatic deformity of the mitral valve, excessive scarring may 372 Valvular disease and infective endocarditis shorten the leaflets or chordae, allowing a potential orifice to form during systole During marked left ventricular dilatation, the geometric orientation of the papillary muscles may pull the leaflet edges away from one another during systole, causing secondary mitral regurgitation Box 12.1 Causes of mitral regurgitation Ischemic heart disease with papillary muscle dysfunction Myxomatous degeneration (prolapse, Marfan’s syndrome) Infective endocarditis Rheumatic Idiopathic hypertrophic subaortic stenosis Left ventricular dilatation of any cause Mitral annular calcification Congenital In all cases of mitral regurgitation, a fraction of left ventricular blood is ejected into the low pressure left atrium This reduces left ventricular afterload and improves systolic emptying The clinical presentation of mitral regurgitation is related to left atrial compliance, and this in turn is related to the acuity of regurgitation The characteristics of acute mitral regurgitation include a small “unprepared” left atrium with reduced compliance, a high left atrial pressure, a tall “v” wave, pulmonary hypertension, and pulmonary edema (Figure 12.5) In acute mitral regurgitation, forward cardiac output usually falls at the expense of mitral regurgitation (forward cardiac output = total cardiac output – mitral regurgitation), because of preferential ejection of blood from the left ventricle into the low pressure left atrial “sink” at the expense of ejection into the higher pressure aorta This reduction in forward cardiac output stimulates peripheral baroreceptors to activate the sympathetic nervous system, which produces a reflexive increase in myocardial contractility (increased inotropy), vasoconstriction, and tachycardia The increase in contractility contributes to supranormal left ventricular emptying, often producing left ventricular ejection fractions greater than 80% Vasoconstriction and tachycardia, however, may further exacerbate the degree of regurgitation (at the expense of forward output) and further raise left atrial pressure In acute severe mitral regurgitation a vicious cycle of worsening forward output, worsening regurgitation, and rising left atrial pressures can cause rapid decompensation and pulmonary edema The physiologic hallmarks of chronic mitral regurgitation, on the other hand, include a marked increase in left atrial size and compliance, 373 Cardiology Core Curriculum ECG V V 40 mmHg LV LA 20 Figure 12.5 Acute mitral regurgitation Simultaneous measurement of left atrial pressure (LA) and left ventricular pressure (LV) pressure during an episode of acute mitral regurgitation related to ischemic papillary muscle dysfunction The large systolic “v” wave in the left atrial pressure tracing is caused by the normal return of pulmonary venous flow of blood to the left atrium, the regurgitation of blood from the left ventricle across the incompetent mitral valve, and the rise in end-diastolic pressure in the non-compliant ischemic left ventricle ECG, electrocardiogram near normal left atrial pressure, the frequent occurrence of atrial fibrillation and symptoms of fatigue due to low forward cardiac output The reason that pulmonary congestion is not a consistent feature of chronic mitral regurgitation is that the left atrium dilates and increases its compliance to accommodate large regurgitant volumes from the ventricle without an excessive increase in pressure Thus, the effects of mitral regurgitation on the pulmonary circulation are minimized Left atrial dilatation is adaptive as it prevents increases in pulmonary vascular pressures However, this adaptation occurs at the cost of inadequate forward cardiac output, because the compliant left atrium 374 Valvular disease and infective endocarditis becomes a preferred low pressure “sump” for left ventricular ejection Consequently, as progressively larger fractions of blood regurgitate into the left atrium, the main symptoms of chronic mitral regurgitation become those of low forward cardiac output In addition, chronic left atrial dilatation predisposes the patient to atrial fibrillation The natural history of mitral regurgitation depends on its etiology The natural history of chronic mitral regurgitation caused by rheumatic scarring or myxomatous degeneration is one of very slow progression with survival exceeding 70% at 15 years in medically treated patients On the other hand, an abrupt worsening in mitral regurgitation in the setting of spontaneous rupture of chordae tendineae, endocarditis, or ischemic heart disease may lead to a lifethreatening medical or surgical emergency Mitral valve prolapse Mitral valve prolapse is a common and often asymptomatic billowing of the mitral leaflets into the left atrium during ventricular systole Other names for this condition include “floppy” mitral valve or myxomatous degeneration Pathologic findings include enlarged, often redundant valve leaflets with the normal collagen and elastin matrix of the valvular fibrosa, which is fragmented and replaced with loose myxomatous connective tissue Isolated involvement of the posterior leaflet of the mitral valve is not uncommon In more severe cases, elongated or ruptured chordae, annular enlargement, and thickened leaflets may be seen Mitral valve prolapse occurs in about 5% of the normal population and is more common in women Mitral valve prolapse may be inherited as a primary autosomal dominant disorder with variable penetrance, or may occur as a secondary complication of other heritable diseases of connective tissue such as Marfan’s syndrome or Ehlers–Danlos syndrome Mitral valve prolapse is often silent, but may manifest as symptoms of palpitations or chest discomfort atypical for angina pectoris Physical examination may reveal a mid-systolic click and late systolic murmur that is heard best at the apex The systolic click is believed to correspond to the snapping of an everted leaflet or chordae as the leaflet is forced back through the mitral annulus, whereas the murmur is believed to correspond with regurgitant flow back through the incompetent mitral valve To make the diagnosis, however, the click and murmur should change characteristically with dynamic auscultation Maneuvers such as squatting or release of Valsalva that increase the volume of blood in the left ventricle should cause the click and murmur to occur later in the cardiac cycle (closer to S2) Conversely, if the volume of blood in the left ventricle is decreased by 375 Cardiology Core Curriculum suddenly standing from the squatting position or by the initiation of the Valsalva maneuver, then the click and murmur should occur earlier (closer to S1) Confirmation of the diagnosis is obtained by echocardiography, which demonstrates posterior displacement of one or both mitral leaflets during systole The clinical course of mitral prolapse is almost always uneventful and benign The most common serious complication is the development of isolated mitral regurgitation, attributed to stretching and elongation of the mitral chordae or leaflets during prolapse Rupture of a chordae, however, can cause the sudden onset of severe regurgitation Other rare complications of mitral prolapse include infective endocarditis, peripheral emboli due to microthrombus formation behind the redundant tissue, arrhythmias, and sudden death The baseline echocardiogram is an excellent screening test for predicting complications of mitral valve prolapse Patients with thickened leaflets or significant mitral regurgitation are at increased risk for complications of worsening mitral regurgitation, heart failure, or endocarditis.18 Treatment thus consists of reassurance of those patients without high risk echocardiographic features of the generally benign prognosis, and of re-examination with echocardiography at appropriate intervals, as well as endocarditis prophylaxis, when significant mitral regurgitation or thickened valves are present Clinical evaluation The symptoms of chronic mitral regurgitation, namely fatigue and weakness, are predominantly caused by low cardiac output during exertion On physical examination, a murmur may be accompanied by a third heart sound (S3) The physical examination of a patient with mitral regurgitation may reveal an apical holosystolic murmur that radiates to the axilla There are many exceptions, however, to conventional description of the apical holosystolic murmur radiating to the axilla For example, when mitral regurgitation is caused by posterior papillary muscle ischemia, the regurgitant jet is directed at the left atrial wall immediately posterior to the aorta, producing a systolic murmur that is best heard radiating to the “aortic” area Non-invasive evaluation The chest radiograph in chronic mitral regurgitation may show ventricular or left atrial enlargement, mitral annular calcification, or pulmonary congestion The electrocardiogram may show left atrial enlargement, left ventricular hypertrophy, atrial fibrillation, or may be normal 376 Valvular disease and infective endocarditis The Doppler echocardiographic examination is an important part of the clinical evaluation of patients with mitral regurgitation Not only will the study provide an approximate estimate of the severity of mitral regurgitation, but it may also identify the etiology and provide an estimate of left ventricular function The echocardiographic estimate of left ventricular ejection fraction is one of the most important determinants of long term survival in mitral regurgitation after mitral valve surgery Because mitral regurgitation is inherently associated with improved left ventricular emptying caused by reduced afterload, any reduction in ejection fraction reveals a substantial reduction in left ventricular contractility.19 Echocardiograms are used for surveillance of left ventricular function every 6–12 months in patients who are asymptomatic with severe mitral regurgitation to monitor left ventricular ejection fraction and end-systolic diamensions Invasive evaluation In contrast to the non-invasive assessment of mitral stenosis, the non-invasive assessment of mitral regurgitation is less accurate For this reason, cardiac catheterization and left ventriculography are required in many patients with symptomatic mitral regurgitation Cardiac catheterization is useful for defining a possible coronary ischemic (i.e papillary muscle) cause, grading the severity of mitral regurgitation, assessing left ventricular contractile function, and making a hemodynamic assessment During left ventriculography a radiocontrast agent is injected into the left ventricle and the severity of mitral regurgitation is judged on the basis of the rapidity and degree to which the left atrium becomes opacified (Table 12.2) Patients with 3+ to 4+ regurgitation have a condition potentially correctable with surgery, whereas those with 1+ to 2+ mitral regurgitation are generally treated with medical therapy Hemodynamic measurements may provide insights into the severity of mitral regurgitation and its consequences Although the height of the “v” wave in the pulmonary capillary wedge tracing provides little information about the severity of mitral regurgitation, elevation in the mean wedge pressure implies that the mitral regurgitation is either acute or associated with left ventricular dysfunction Treatment The use of vasodilators and diuretics in patients with symptomatic mitral regurgitation result in symptomatic improvement by increasing forward flow and reducing the degree of regurgitation 377 Cardiology Core Curriculum Table 12.2 Angiographic grades of mitral regurgitation Grade Angiographic details 1+ 2+ 3+ Contrast enters but does not completely opacify the left atrium Contrast faintly but completely opacifies the left atrium Contrast completely and quickly opacifies the left atrium equal in intensity to that of the left ventricle Contrast quickly concentrates in the left atrium to a degree greater than that for the left ventricle, and contrast also enters the pulmonary veins 4+ Mitral valve surgery is recommended for non-ischemic, severe mitral regurgitation in several circumstances (Box 12.2) Most importantly, surgery is reserved for symptomatic improvement in patients with moderately severe (3+) or severe (4+) grades of regurgitation Patients with acute forms of mitral regurgitation related to endocarditis or chordal rupture are unlikely to stabilize with medical therapy and often require surgery Patients with impaired left ventricular function, however, have worse postoperative survival than those with normal left ventricular function Patients with mitral regurgitation caused by etiologies that are amenable to valve repair such as posterior leaflet redundancy from myxomatous degeneration may have better survival than those who require valve replacement.20 Thus, a lower threshold for surgical referral should be used for patients with “reparable” valves than for those who will require a valve replacement The operative mortality rate is about 2–4% for mitral valve repair and about 8–10% for mitral replacement The 10-year survival rate is about 80% for mitral repair and about 50% for mitral replacement The differences between valve repair and replacement in postoperative survival cannot be entirely ascribed to surgical technique Patients who are candidates for valve repair tend to be younger than those who require valve replacement Box 12.2 Indications for surgery in severe, non-ischemic mitral regurgitation1 Acute, symptomatic mitral regurgitation, in which repair is likely Patients with New York Heart Association functional class II, III, or IV symptoms, with normal left ventricular function (left ventricular ejection fraction [LVEF] >60% and end-systolic diameter