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.
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.
- 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.
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 )
