Park's Pediatric Cardiology for Practitioners, 6th Ed.

Valvular Heart Disease

Valvular heart diseases are either congenital or acquired in origin. The pathophysiology and clinical manifestations are similar for both entities and are discussed in Chapter 10, Pathophysiology of Obstructive and Valvular Regurgitant Lesions. Congenital stenoses of the aortic and pulmonary valves are discussed in depth in the section on obstructive lesions in Chapter 13.

In this chapter, mitral stenosis (MS), mitral regurgitation (MR), and aortic regurgitation (AR) of both congenital and acquired etiology are discussed if they are isolated or the major lesion. Although the cause of mitral valve prolapse (MVP) is not entirely clear, it is discussed in this chapter because it involves a cardiac valve. Isolated congenital pulmonary regurgitation (PR), tricuspid regurgitation, and tricuspid stenosis of significance are exceedingly rare and therefore are not discussed. PR after tetralogy of Fallot (TOF) surgery is discussed under TOF in Chapter 14. Tricuspid regurgitation is most frequently seen with Ebstein’s anomaly and is discussed under that condition.

Most acquired valvular heart diseases are of rheumatic etiology. They are, however, rare in the industrialized countries, although they still occur frequently in less developed countries. Among rheumatic heart disease, mitral valve involvement occurs in about three fourths and aortic valve involvement in about one fourth of the cases. Stenosis and regurgitation of the same valve usually occur together. Isolated aortic stenosis (AS) of rheumatic origin without mitral valve involvement is extremely rare. Rheumatic involvement of the tricuspid and pulmonary valves almost never occurs.

Mitral Stenosis

Prevalence

Isolated congenital MS is very rare. It is usually associated with other anomalies such as Shone complex. MS of rheumatic origin is rare in children (because it requires 5 to 10 years from the initial attack to develop the condition), but it is the most common valvular involvement in adult rheumatic patients in areas where rheumatic fever is still prevalent.

Pathology and Pathophysiology

1. Congenital MS usually is associated with obstruction at more than one level. The stenosis may be at the level of the valve leaflets (fusion of the leaflets), papillary muscle (single papillary muscle seen with parachute mitral valve), chordae (thickened and fused chordae seen in single papillary muscle), or supravalvar region (supravalvar mitral ring), and it may be caused by hypoplasia of the valve ring itself (as seen with hypoplastic left heart syndrome).

2. In rheumatic MS, thickening of the leaflets and fusion of the commissures dominate the pathologic findings. Calcification with immobility of the valve results over time.

3. Regardless of the etiology, a significant MS results in the enlargement of the left atrium (LA), pulmonary venous hypertension, and PA hypertension with resulting enlargement and hypertrophy of the right side of the heart.

4. In patients with severe pulmonary venous hypertension, pulmonary congestion and edema, fibrosis of the alveolar walls, hypertrophy of the pulmonary arterioles, and loss of lung compliance result.

Clinical Manifestations

History

1. Patients with mild MS are asymptomatic.

2. In infants with severe MS, symptoms develop early in life with shortness of breath and failure to thrive.

3. Dyspnea with or without exertion is the most common symptom in older children. Orthopnea, nocturnal dyspnea, or palpitation is present in more severe cases.

Physical Examination (Fig. 21-1)

1. An increased right ventricular (RV) impulse is palpable along the left sternal border. Neck veins are distended if right-sided heart failure supervenes.

2. A loud S1 at the apex and a narrowly split S2 with accentuated P2 are audible if pulmonary hypertension is present. An opening snap (a short snapping sound accompanying the opening of the mitral valve) may be audible in rheumatic MS. A low-frequency mitral diastolic rumble is present at the apex (see Fig. 21-1). A crescendo presystolic murmur may be audible at the apex. Occasionally, a high-frequency diastolic murmur of PR (Graham Steell’s murmur) is present at the upper left sternal border, but it is difficult to distinguish from AR.

Electrocardiography

Right-axis deviation, left atrial hypertrophy (LAH), and right ventricular hypertrophy (RVH) (caused by pulmonary hypertension) are common. Atrial fibrillation (AF) is rare in children.

Chest Radiography

1. The LA and RV are usually enlarged, and the main pulmonary artery (PA) segment is usually prominent.

2. Lung fields show pulmonary venous congestion, interstitial edema shown as Kerley’s B lines (dense, short horizontal lines most commonly seen in the costophrenic angles), and redistribution of pulmonary blood flow with increased pulmonary vascularity to the upper lobes.

Echocardiography

Echocardiography is the most accurate noninvasive tool for the detection of MS.

1. A two-dimensional echocardiographic study should define structural abnormalities of the valve, supravalvar region, chordae, and papillary muscles.

2. It shows a dilated LA. The main PA, RV, and right atrium (RA) also are dilated.

3. Doppler studies can estimate the pressure gradient and thus the severity of stenosis. A mean Doppler gradient of less than 4 to 5 mm Hg results from mild stenosis, 6 to 12 mm Hg is seen with moderate stenosis, and a mean gradient greater than 13 mm Hg is seen with severe stenosis. RV systolic pressure can be estimated from the TR jet velocity (by Bernoulli equation), which may be elevated.

4. In patients with rheumatic MS, an M-mode echocardiogram may show a diminished E to F slope (reflecting a slow diastolic closure of the anterior mitral leaflet), anterior movement of the posterior leaflet during diastole, multiple echoes from thickened mitral leaflets, and large LA dimension.

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FIGURE 21-1 Cardiac findings of mitral stenosis. Abnormal sounds are shown in black and include a loud S1, an ejection click (EC), a loud S2, and an opening snap (OS). Also note the mid-diastolic rumble and presystolic murmur. The murmur of pulmonary regurgitation indicates long-standing pulmonary hypertension.

Natural History

1. Infants with significant MS with failure to thrive require either balloon or surgical intervention.

2. Most children with mild MS are asymptomatic but become symptomatic with exertion.

3. Recurrence of rheumatic fever worsens the stenosis.

4. Atrial flutter or fibrillation and thromboembolism (related to the chronic atrial arrhythmias) are rare in children.

5. Hemoptysis can develop from the rupture of small vessels in the bronchi as a result of long-standing pulmonary venous hypertension.

Management

Medical

1. Mild and moderate MS is managed with anticongestive measures (diuretics).

2. Balloon dilatation of the valve should be considered in infants with failure to thrive and with repeated respiratory infections. It may delay surgical intervention. Balloon dilatation is an effective and safe option for children with rheumatic MS.

3. If AF develops, propranolol, verapamil, or digoxin may be used to slow the atrioventricular (AV) conduction. Intravenous procainamide may be used for conversion to sinus rhythm in hemodynamically stable patients. For patients with chronic AF, anticoagulation with warfarin should be started 3 weeks before cardioversion to prevent systemic embolization of atrial thrombus. Anticoagulation is continued for 4 weeks after restoration of sinus rhythm (see Chapter 24 for further discussion). Quinidine may prevent recurrence.

4. Good dental hygiene and antibiotic prophylaxis against subacute bacterial endocarditis (SBE) are important.

5 Varying degrees of restriction of activity may be indicated.

6. Recurrence of rheumatic fever should be prevented with penicillin or sulfonamide (see Chapter 20).

Surgical

Indications

According to the American College of Cardiology/American Heart Association (ACC/AHA) 2006 Guidelines, the indications for mitral valve surgery for congenital MS in adolescents and young adults are as follows.

1. Surgery is indicated in patients with congenital MS who have symptoms (New York Heart Association [NYHA] functional class III or IV) and mean Doppler MV gradient greater than 10 mm Hg. (Symptoms may include angina, syncope, or dyspnea on exertion.)

2. Surgery is reasonable in mildly symptomatic patients with congenital MS (NYHA functional class I) and a mean Doppler MV gradient greater than 10 mm Hg.

3. Surgery is reasonable in asymptomatic patients with PA pressure of 50 mm Hg or greater and a mean MV gradient of 10 mm Hg or greater.

For infants and children with severe MS, the following indications may also apply.

1. Symptomatic infants or children with failure to gain weight, dyspnea on exertion, pulmonary edema, or paroxysmal dyspnea may be candidates for surgery (or balloon dilatation).

2. Failed balloon dilatation or severe MR resulting from the balloon procedure is an indication for surgery.

3. Recurrent AF, thromboembolic phenomenon, and hemoptysis may be indications for surgery in children.

Procedures and Mortality

1. Resection of a supravalvar mitral ring or splitting of thickened and fused chordae is an option depending on the nature of the lesion.

2. For rheumatic MS, if balloon dilatation is unsuccessful, closed or open mitral commissurotomy remains the procedure of choice for those with pliable mitral valves without calcification or MR. The operative mortality rate is less than 1%.

3. Mitral valve replacement: A prosthetic valve (Starr-Edwards, Bjork-Shiley, St. Jude) is inserted either in the annulus or in a supra-annular position. The surgical mortality rate is 0% to 19%. All mechanical valves require anticoagulation with warfarin with its long-term risk, and reoperation may become necessary because of valve entrapment by pannus formation. The bioprostheses (porcine valve, heterograft valve) do not require anticoagulation therapy but require low-dose aspirin. Bioprostheses tend to deteriorate more rapidly because of calcific degeneration in children.

4. In patients with a parachute mitral valve, creation of fenestration among the fused chordae may increase effective orifice area and improve symptoms dramatically. MV replacement may occasionally be necessary but is especially problematic in patients with a hypoplastic mitral annulus in whom an annulus-enlarging operation may be necessary.

5. Rarely, a valved conduit can be placed between the LA and the apex of the left ventricle (LV).

Complications

1. Postoperative congestive heart failure (CHF) is the most common cause of early postoperative death.

2. Arterial embolization is a rare complication.

3. Bleeding diathesis is possible with anticoagulation therapy for an implanted prosthetic valve.

Postoperative Follow-up

1. Regular checkups every 6 to 12 months with echocardiography and Doppler studies should be done for possible dysfunction of the repaired or replaced valve.

2. After replacement with a mechanical valve with no risk factors, warfarin is indicated to achieve an international normalized ratio (INR) of 2.5 to 3.5. Low-dose aspirin is also indicated. After replacement with a bioprosthesis and risk factors (which may include AF, previous thromboembolism, LV dysfunction, and hypercoagulable state), warfarin is also indicated.

3. When there are no risk factors after bioprosthesis placement, aspirin alone is indicated at 75 to 100 mg/day (see the ACC/AHA 2006 Guidelines).

Mitral Regurgitation

Prevalence

Mitral regurgitation is more common than MS. It is most often congenital and associated with AV canal defect. MR of rheumatic origin is rare but is the most common valvular involvement in children with rheumatic heart disease.

Pathology

1. Mitral valve regurgitation associated with AV canal occurs frequently through the cleft in the mitral valve. When the valve annulus is dilated from any causes that dilate the LV (e.g., aortic regurgitation (AR) or dilated cardiomyopathy), central regurgitation occurs.

2. In rheumatic heart disease, mitral valve leaflets are shortened because of fibrosis, resulting in MR.

3. With increasing severity of MR, dilatation of the LA and LV results, and the mitral valve ring may become dilated. Pulmonary hypertension may eventually develop as with MS.

Clinical Manifestations

History

1. Patients are usually asymptomatic with mild MR.

2. Rarely, fatigue (caused by reduced forward cardiac output) and palpitation (caused by AF) develop.

Physical Examination (Fig. 21-2)

1. The jugular venous pulse is normal in the absence of CHF. A heaving, hyperdynamic apical impulse is palpable in severe MR.

2. The S1 is normal or diminished. The S2 may split widely as a result of shortening of the LV ejection and early closure of the aortic valve. The S3 commonly is present and loud. The hallmark of MR is a regurgitant systolic murmur starting with S1, grade 2 to 4 of 6, at the apex, with good transmission to the left axilla (best demonstrated in the left decubitus position). A short, low-frequency diastolic rumble may be present at the apex (see Fig. 21-2).

Electrocardiography

1. ECG findings are normal in mild cases.

2. Left ventricular hypertrophy (LVH) or LV dominance, with or without LAH, is usually present.

3. AF is rare in children but often develops in adults.

Chest Radiography (Fig. 21-3)

1. The LA and LV are enlarged to varying degrees.

2. Pulmonary vascularity usually is within normal limits, but a pulmonary venous congestion pattern may develop if CHF supervenes.

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FIGURE 21-2 Cardiac findings of mitral regurgitation. The arrow near the apex indicates the direction of radiation of the murmur toward the left axilla.

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FIGURE 21-3 Posteroanterior (A) and lateral (B) views of chest radiographs in a patient with moderately severe mitral regurgitation of rheumatic origin. The lateral view was obtained with barium swallow. The cardiothoracic ratio is increased (0.64), and the apex is displaced downward and laterally in the posteroanterior view. The lateral view shows an indentation of the barium-filled esophagus by an enlarged left atrium, and the left ventricle is displaced posteriorly.

Echocardiography

1. Two-dimensional echocardiography shows dilated LA and LV; the degree of dilatation is related to the severity of MR.

2. Color-flow mapping of the regurgitant jet into the LA and Doppler studies can assess the severity of the regurgitation.

3. The echocardiogram can distinguish eccentric regurgitation through the cleft mitral valve from central regurgitation (associated with annular dilatation).

Natural History

1. Patients are relatively stable for a long time with mild regurgitation.

2. Infective endocarditis is a rare complication.

3. LV failure and consequent pulmonary hypertension may occur in adult life.

Management

Medical

1. Prophylaxis against recurrence of rheumatic fever (see Chapter 20) is important.

2. Activity need not be restricted in most mild cases.

3. Afterload-reducing agents are particularly useful in maintaining the forward cardiac output.

4. Anticongestive therapy (with diuretics and digoxin) is provided if CHF develops.

5. If AF develops (rare in children), digoxin is indicated to slow the ventricular response. For further discussion of the management of AF, see Chapter 24.

Surgical

Indications

The indications for valve repair surgery are not so stringent because surgery can significantly improve the regurgitation. Indications for valve surgery in adolescents and young adults with severe MR are as follows, according to the ACC/AHA 2006 Guidelines (Circulation 2006).

The following are noninvasive findings of severe MR: vena contracta width larger than 0.7 cm with large central MR jet (area >40% of LA size) or with a wall-impinging jet of any size, swirling in LA, or enlargement of the LA and LV size.

1. Symptomatic patients with severe congenital MR with NYHA functional class III or IV. (see earlier discussion for noninvasive findings of severe MR).

2. Asymptomatic patients with severe congenital MR (see earlier discussion) and LV systolic dysfunction (ejection fraction [EF] ≤0.6).

3. Surgery may be considered in patients with preserved LV function if the likelihood of successful repair without residual MR is great.

Some centers consider an LV diastolic dimension of 60 mm in adults an indication for mitral valve replacement. For children, intractable CHF, progressive cardiomegaly with symptoms, and pulmonary hypertension may be indications.

Procedures and Mortality

Mitral valve repair or replacement is performed under cardiopulmonary bypass.

1. Valve repair surgery is preferred over valve replacement, performed usually beyond infancy and during childhood. For cleft leak, repair of the cleft is performed. For central regurgitation with dilated annulus, anuloplasty is performed by commissuroplasty (not using an anuloplasty ring, which restricts growth potential). Valve repair has a lower mortality rate (<1%), and anticoagulation is not necessary.

2. Valve replacement is rarely necessary for unrepairable regurgitation. Frequently used low-profile prostheses are the Bjork-Shiley tilting disk and the St. Jude pyrolytic carbon valve. The surgical mortality rate is 2% to 7% for valve replacement. If a prosthetic valve is used, anticoagulation therapy must be continued.

Complications

Complications are similar to those listed for MS.

Postoperative Follow-up

1. Valve function (of either the repaired natural valve or the replacement valve) should be checked by echocardiography and Doppler studies every 6 to 12 months.

2. After replacement with a mechanical valve with no risk factors, warfarin is indicated to achieve an INR of 2.5 to 3.5 along with low-dose aspirin. After replacement with a bioprosthesis with no risk factors, aspirin alone is indicated at the dose of 75 to 100 mg/day; when there are risk factors (e.g., AF, previous thromboembolism, LV dysfunction, hypercoagulable state), warfarin is also indicated.

Aortic Regurgitation

Prevalence

Aortic regurgitation is more often congenital than rheumatic in origin. AR of rheumatic origin is almost always associated with mitral valve disease.

Pathology

1. Congenital causes of AR include the following:

a. Congenital bicuspid aortic valve

b. After balloon dilatation of aortic valve

c. Associated with ventricular septal defect (VSD, either subpulmonary or membranous)

d. Secondary to subaortic stenosis

e. In association with dilated aortic root (Marfan’s syndrome or Ehlers-Danlos syndrome)

2. Rarely, rheumatic heart disease is a cause of AR.

Clinical Manifestations

History

1. Patients with mild regurgitation are asymptomatic.

2. Exercise tolerance is reduced with more severe AR or CHF.

Physical Examination (Fig. 21-4)

1. With moderate or severe AR, the precordium may be hyperdynamic with a laterally displaced apical impulse. A diastolic thrill occasionally is present at the third left intercostal space. A wide pulse pressure and a bounding water-hammer pulse may be present with severe AR.

2. The heart sounds are normal with mild AR. The S1 is decreased in intensity with moderate to severe AR. The S2 may be normal or single. A high-pitched diastolic decrescendo murmur, best audible at the third or fourth left intercostal space, is the auscultatory hallmark. This murmur is more easily audible with the patient sitting and leaning forward. The longer the murmur, the more severe the regurgitation (see Fig. 21-4). A systolic murmur of varying intensity may be present at the second right intercostal space because of relative AS caused by an increased stroke volume. The combination of the diastolic and systolic murmurs gives rise to a to-and-fro murmur in patients with severe AR. A mid-diastolic mitral rumble (Austin Flint murmur) may be present at the apex when the AR is severe.

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FIGURE 21-4 Cardiac findings of aortic regurgitation. The S1 is abnormally soft (black bar). The predominant murmur is a high-pitched, diastolic decrescendo murmur at the third left intercostal space.

Electrocardiography

The ECG is normal in mild cases. In severe cases, LVH usually is present. LAH may be present in long-standing cases.

Chest Radiography

Cardiomegaly of varying degree involving the LV is present. A dilated ascending aorta and a prominent aortic knob frequently are present. Pulmonary venous congestion develops if LV failure supervenes.

Echocardiography

The LV dimension is increased, but the LA remains normal in size. The LV diastolic dimension is proportional to the severity of AR. Color-flow and Doppler examination can aid in estimating the severity of the regurgitation. LV systolic dysfunction develops at a later stage in severe AR.

Natural History

1. Patients with mild to moderate AR remain asymptomatic for a long time, but when symptoms begin to develop, many patients deteriorate rapidly.

2. Anginal pain, CHF, and multiple premature ventricular contractions are unfavorable signs occurring with severe AR.

3. Infective endocarditis is a rare complication.

Management

Medical

1. In case of a rheumatic cause, prophylaxis should be continued against the recurrence of rheumatic fever with penicillin or sulfonamides (see Chapter 20).

2. Activity need not be restricted in mild cases, but varying degrees of restriction are indicated in more severe cases. Aerobic exercise is a better form of exercise, and weightlifting exercise should be discouraged.

3. When used on a long-term basis, the angiotensin-converting enzyme inhibitors have been shown to reduce (or even reverse) the dilatation and hypertrophy of the LV in children with AR but without CHF.

4. If CHF develops, digoxin, diuretics, and afterload-reducing agents may be beneficial, but the benefits are rarely maintained.

Surgical

Indications

A major clinical decision in AR is the timing of aortic valve replacement. Ideally, it should be performed before irreversible dilatation of the LV develops, but there is no reliable method of detecting that point. According to ACC/AHA 2006 Guidelines, the following are surgical indications in adolescents and adult patients with chronic severe AR. (Chronic severe AR is considered present when central jet width >86% LV outflow tract or Doppler vena contracta width >0.6 cm is present.) Similar indications may apply for younger children.

1. Symptomatic patients (with angina, syncope, or dyspnea on exertion) with severe AR

2. Asymptomatic patients with LV systolic dysfunction (EF <0.5) on serial studies 1 to 3 months apart

3. Asymptomatic patients with progressive LV enlargement (end-diastolic dimension > mean +4 standard deviation)

Procedure and Mortality

Aortic valve repair is favored over valve replacement whenever possible. Valve replacement does not incorporate growth potential except for the Ross procedure. Surgery is performed under cardiopulmonary bypass. The mortality rate for valve repair is near 0%, and that for valve replacement is about 2% to 5%.

1. Valve repair may include repair of simple tears or valvuloplasty for prolapsed cusps and so on.

2. Valve replacement surgery

a. The antibiotic-sterilized aortic homograft has been widely used and appears to be the device of choice.

b. The porcine heterograft has the risk of accelerated degeneration.

c. The Bjork-Shiley and St. Jude prostheses require anticoagulation therapy and are less suitable for young patients.

3. A pulmonary root autograft (Ross procedure) may be an attractive alternative to the conventional valve replacement surgery (see Fig. 13-9) in selected adolescents and young adults. In this procedure, the patient’s own pulmonary valve and the adjacent PA are used to replace the diseased aortic valve and the adjacent aorta. The coronary arteries are detached from the aorta and implanted into the PA. The surgical mortality rate is near 0%. This procedure does not require anticoagulant therapy, the autograft may last longer than a porcine bioprosthesis, and there is a growth potential for the autograft pulmonary valve.

Complications

1. Postoperative acute cardiac failure is the most common cause of death.

2. Thromboembolism, chronic hemolysis, and anticoagulant-induced hemorrhage may occur with a prosthetic valve.

3. Porcine valves tend to develop early calcification in children.

4. Prosthetic valve endocarditis is a rare complication.

Postoperative Follow-up

1. Regular follow-up of valve function should be done every 6 to 12 months by echocardiography and Doppler studies.

2. Anticoagulation is needed after a prosthetic mechanical valve replacement. INR should be maintained between 2.5 and 3.5 for the first 3 months and 2.0 to 3.0 beyond that time. Low-dose aspirin (75–100 mg/day for adolescents) is also indicated in addition to warfarin (ACC/AHA 2006 Guidelines).

3. After aortic valve replacement with bioprosthesis and no risk factors, aspirin (75–100 mg) is indicated, but warfarin is not indicated. When there are risk factors (which include AF, previous thromboembolism, LV dysfunction, and hypercoagulable state), warfarin is indicated to achieve an INR of 2.0 to 3.0 (ACC/AHA 2006 Guidelines).

4. After the Ross procedure, anticoagulation is not indicated.

5. The importance of good oral hygiene and antibiotic prophylaxis against SBE should be emphasized.

Mitral Valve Prolapse

Prevalence

The reported incidence of MVP of 2% to 5% in the pediatric population probably is an overestimate. The prevalence of MVP increases with age. This condition usually occurs in older children and adolescents (it is more common in adults) and has a female preponderance (male-to-female ratio of 1:2).

Pathology

1. MVP is generally sporadic but is associated with disorders of the connective tissue, including Marfan syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta, and others. Secondary cases of MVP can be caused by other conditions, including rupture or dysfunction of the papillary muscles caused by myocardial infarction or ischemia, rupture of chordae tendineae caused by infective endocarditis, or abnormal LV wall motion associated with ischemia or primary myocardial disease. Only primary MVP is discussed in this chapter.

2. In the primary form of MVP, thick and redundant mitral valve leaflets bulge into the mitral annulus (caused by myxomatous degeneration of the valve leaflets, chordae, or both). The posterior leaflet is more commonly and more severely affected than the anterior leaflet.

3. MVP is associated with several of the most common heritable disorders of connective tissue disease, such as Marfan’s syndrome, Ehlers-Danlos syndrome, Stickler syndrome, and polycystic kidney disease in adults. Nearly all patients with Marfan’s syndrome have MVP.

4. A congenital heart defect is present in one third of patients with MVP. Secundum atrial septal defect is most common; VSD and Ebstein’s anomaly are found rarely.

Clinical Manifestations

History

1. MVP usually is asymptomatic, but a history of nonexertional chest pain; palpitation; and, rarely, syncope may be elicited. Chest discomfort may be typical of anginal pain but more atypical in that it is not related to exertion and is often brief attacks or stabbing pain at the apex. Whether the chest pain is actually cardiac in origin (from papillary muscles) has not been fully determined, but the discomfort could be secondary to abnormal tension on papillary muscle. Palpitation may be related to cardiac arrhythmias. Syncope or presyncope may be caused by arrhythmias or a manifestation of an orthostatic phenomenon.

2. The patient occasionally has a family history of MVP.

Physical Examination (Fig. 21-5)

1. An asthenic build with a high incidence of thoracic skeletal anomalies (80%), including pectus excavatum (50%), straight back (20%), and scoliosis (10%), is common. (Straight-back syndrome is a condition in which the normal dorsal curvature of the spine is lost, resulting in a shortening of the chest’s anteroposterior diameter.)

2. The midsystolic click with or without a late systolic murmur is the auscultatory hallmark of this syndrome and is best audible at the apex (see Fig. 21-5). The presence or absence of the click and murmur, as well as their timing, varies from one examination to the next.

a. The click and murmur may be brought out by held expiration, left decubitus position, sitting, standing, or leaning forward. They may disappear on inspiration.

b. Various maneuvers can alter the timing of the click and the murmur:

(1) The click moves toward the S1 and the murmur lengthens with maneuvers that decrease the LV volume, such as standing, sitting, Valsalva’s strain phase, tachycardia, and the administration of amyl nitrite.

(2) The click moves toward the S2, and the murmur shortens with maneuvers that increase the LV volume, such as squatting, hand grip exercise, Valsalva’s release phase, bradycardia, and the administration of pressor agents or propranolol.

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FIGURE 21-5 Diagram of auscultatory findings in mitral valve prolapse and the effect of various maneuvers on the timing of the midsystolic click (MC) and the murmur. The maneuvers that reduce ventricular volume enhance leaflet redundancy and move the click and murmur earlier in systole. An increase in left ventricular dimension has the opposite effect.

Electrocardiography

1. The ECG findings are usually normal, but a superiorly directed T vector (with flat or inverted T waves in II, III, and aVF) occurs in 20% to 60% of patients (Fig. 21-6).

2. Arrhythmias are relatively uncommon and include supraventricular tachycardia, premature atrial contractions, and premature ventricular contractions.

3. First-degree AV block and right bundle branch block are occasionally present.

4. The incidence of Wolff-Parkinson-White preexcitation or prolonged QT interval is higher in patients with MVP than in the general population.

5. LVH or LAH rarely is present.

Chest Radiography

1. Chest radiographs are unremarkable except for LA enlargement in patients with severe MR.

2. Thoracoskeletal abnormalities (e.g., straight back, pectus excavatum, scoliosis) may be present.

Echocardiography

Echocardiographic findings for adult patients with MVP have been established, but those for pediatric patients are not clearly defined.

1. Two-dimensional echocardiography shows prolapse of the mitral valve leaflet(s) superior to the plane of the mitral valve. The parasternal long-axis view is most reliable. The superior displacement seen only on the apical four-chamber view is not diagnostic because more than 30% of preselected normal children show this finding. The “saddle-shaped” mitral valve ring explains the superior displacement of the mitral valve seen in normal people in the apical four-chamber view.

2. In adults, one or both mitral valve leaflets bulge by at least 2 mm into the LA during systole in the parasternal long-axis view. Thickening of the involved leaflet to more than 5 mm supports the diagnosis. In more severe myxomatous disease, leaflet redundancy, chordal elongation, and dilatation of the mitral annulus may be present.

3. Some pediatric patients with the characteristic body build and auscultatory findings of the condition do not show the adult echocardiographic criterion of MVP; they may only show thickened mitral leaflets with systolic straightening or systolic superior doming and some posterosuperior displacement of the coaptation point of the mitral valve, some even with mild MR. It may be because MVP is a progressive disease that shows its full manifestations only in adult life.

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FIGURE 21-6 Tracing from a 14-year-old girl with mitral valve prolapse. The T wave in aVF is inverted.

4. A large number of first-degree relatives of patient with MVP have echocardiographic findings of MVP.

Natural History

1. The majority of patients are asymptomatic, particularly during childhood.

2. Complications that are reported in adult patients, although rare in childhood, include sudden death (probably from ventricular arrhythmias), SBE, spontaneous rupture of chordae tendineae, progressive MR, CHF, arrhythmias, and conduction disturbances.

Management

1. Asymptomatic patients require no treatment or restriction of activity.

2. Antibiotic prophylaxis against bacterial endocarditis is recommended when significant MR is present by auscultation or by echo studies.

3. β-Adrenergic blockers (propranolol or atenolol) are often used in the following situations.

a. Patients who are symptomatic (with palpitation, lightheadedness, dizziness, or syncope) secondary to ventricular arrhythmias. Symptomatic patients suspected to have arrhythmias should undergo ambulatory ECG monitoring, treadmill exercise testing, or both. Although beta-blockers are the drug of choice, other drugs, such as calcium blockers, quinidine, or procainamide, may prove to be effective in some patients.

b. Patients with self-terminating episodes of supraventricular tachycardia may also receive beta-blockers.

c. Patients with chest discomfort may also be treated with propranolol. (It is not relieved by nitroglycerin but may worsen it.)

4. Physical activities that require prolonged periods of straining, such as weightlifting, push-ups, pull-ups, sit-ups, and hanging on monkey bars, are discouraged; these activities add stress to the mitral valve apparatus.

5. Reconstructive surgery or mitral valve replacement rarely may be indicated in patients with severe MR. MVP is the most common cause of isolated MR requiring surgical treatment in the United States.