Valvular heart disease is either congenital or acquired. Many congenital valvular abnormalities are associated with other major defects. A relatively isolated form of valvular heart disease is rheumatic in origin, which still occurs in some parts of the world. Among rheumatic heart disease, mitral valve involvement occurs in about three-fourths and aortic valve involvement in about one-fourth of cases. Rheumatic involvement of the tricuspid and pulmonary valves almost never occurs. Although the cause of mitral valve prolapse (MVP) is not entirely clear, it is discussed in this chapter.
I
Mitral Stenosis
A. Prevalence
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. Congenital MS occurs in 0.2 to 0.6% of CHDs, usually as part of other defects.
B. Pathology and Pathophysiology
- 1.
Congenital MS encompasses different types of obstructions occurring at different levels near the mitral valve position. The stenosis may be due to obstruction at the valve level (fusion of the leaflets), at the papillary muscle level (single papillary muscle seen with parachute mitral valve), at the chordae (thickened and fused chordae seen in single papillary muscle), or at the supravalvar region (supravalvar mitral ring), and it may be due to the hypoplasia of the valve ring itself (as seen with HLHS). Some of these anomalies are associated with other CHD.
- 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 LA, pulmonary venous hypertension, and pulmonary artery hypertension with resulting enlargement and hypertrophy of the right side of the heart.
- 4.
In patients with severe MS, pulmonary congestion and edema, fibrosis of the alveolar walls, hypertrophy of the pulmonary arterioles, and loss of lung compliance result.
C. Clinical Manifestations
- 1.
In infants with severe MS, symptoms develop early with shortness of breath and failure to thrive. Children with mild MS are asymptomatic. With significant MS, dyspnea with or without exertion is the most common symptom in older children. Orthopnea, nocturnal dyspnea, or palpitation is present in more severe cases.
- 2.
Neck veins are distended if right-sided heart failure supervenes. A loud S1 at the apex and a narrowly split S2 with accentuated P2 are audible if pulmonary hypertension is present ( Fig. 13.1 ). In older children, an opening snap (a short snapping sound accompanying the opening of the mitral valve) and a low-frequency mitral diastolic rumble may be present at the apex. A crescendo presystolic murmur may be audible at the apex. Occasionally, a high-frequency diastolic murmur of PR (Graham Steell murmur) is present at the ULSB in patients with pulmonary hypertension.
Fig. 13.1
Cardiac findings of MS. 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 insufficiency indicates long-standing pulmonary hypertension.
- 3.
The electrocardiogram (ECG) may show RAD, LAH, and RVH (caused by pulmonary hypertension). AF is rare in children.
- 4.
Chest radiographs show enlargement of the LA and RV. The main PA segment is usually prominent. Lung fields show pulmonary venous congestion, interstitial edema shown as Kerley 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.
- 5.
Echo studies provide accurate diagnosis and severity of MS.
- a.
Dilated LA, RV, and RA and prominent main PA are imaged.
- b.
A mean Doppler gradient of <4 to 5 mm Hg results from mild stenosis, 6 to 12 mm Hg from moderate stenosis, and >13 mm Hg from severe stenosis.
- c.
RV systolic pressure can be estimated from the TR jet velocity.
- a.
C. 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.
For rheumatic MS, 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.
D. Management
Different management plans apply to congenital MS and rheumatic MS.
E. For Congenital Mitral Stenosis
- 1.
Patients with mild or moderate stenosis usually do not warrant surgery or catheter intervention.
- a.
Diuretic therapy and/or varying degrees of restriction of activity may be indicated.
- b.
If atrial fibrillation (AF) develops, medical treatment with propranolol, verapamil, or digoxin may be used. Cardioversion may be indicated for patients with chronic AF. Quinidine may prevent recurrence.
- c.
Recurrent AF, thromboembolic phenomenon, and hemoptysis may be indications for surgery in children.
- a.
- 2.
Patients with severe MS require relief of obstruction. Options of intervention include balloon mitral valvuloplasty, surgical valvuloplasty, or surgical valve replacement. Surgical management is challenging due to the limited life span of prosthesis, need for replacement due to growth, and need for chronic anticoagulation. Therefore in some infants with severe pathology, a Norwood or hybrid approach (as used for HLHS) early in life may be an option.
F. For Rheumatic Mitral Stenosis
- 1.
For patients with rheumatic MS, secondary prevention of rheumatic fever with penicillin or sulfonamide is indicated (see Chapter 12 ).
- 2.
2014 American Heart Association/American College of Cardiology (AHA/ACC) guidelines recommend the following (Nishimura et al., 2014).
- a.
Anticoagulation with warfarin or heparin is indicated in patients with (1) MS and AF or (2) MS and a prior embolic event, or (3) MS and a left atrial thrombus.
- b.
Percutaneous mitral balloon commissurotomy is recommended for symptomatic patients with severe MS (defined as mitral valve area ≤1.5 cm 2 , stage D) and favorable valve morphology in the absence of left atrial thrombus or moderate-to-severe MR.
- c.
Mitral valve surgery (repair, commissurotomy, or valve replacement) is indicated in severely symptomatic patients with severe MS (as defined earlier) who are not at high risk for surgery and who are not candidates for or who have failed previous percutaneous mitral balloon commissurotomy.
- a.
- 3.
Mitral valve replacement surgery . A prosthetic valve insertion carries a surgical mortality of 0 to 19%. All mechanical valves require anticoagulation with warfarin. Reoperation may become necessary due to valve deterioration or malfunction.
G. Postintervention Follow-Up
- 1.
Regular checkups every 6 to 12 months with echo and Doppler studies should be done for possible dysfunction of the repaired or replaced valve.
- 2.
After replacement with a mechanical valve , warfarin is indicated to achieve an international normalized ratio (INR) of 2.5 to 3.5. Low-dose aspirin is also indicated.
- 3.
After replacement with a bioprosthesis , if there are risk factors (e.g., AF, a prior embolic event, and a left atrial thrombus), warfarin is also indicated. When there are no risk factors, aspirin alone is indicated at 75 to 100 mg per day.
II
Mitral Regurgitation
A. Prevalence
MR is more common than MS. Congenital MR is most often associated with AV canal defect. MR of rheumatic origin is rare but it is the most common valvular involvement in children with rheumatic heart disease.
B. Pathology
- 1.
Congenital MR associated with AV canal defects occurs through the cleft in the mitral valve (with eccentric regurgitation). Rheumatic MR results from the shortening of the mitral leaflet by fibrosis (with central regurgitation).
- 2.
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 but is less common than with MS.
C. Clinical Manifestations
- 1.
Patients are usually asymptomatic with mild MR. With increasing severity of MR, a history of fatigue and palpitation may be present.
- 2.
The S2 may split widely as a result of shortening of the LV ejection and early closure of the aortic valve. A loud S3 is common. The hallmark of MR is a grade 2 to 4/6 regurgitant systolic murmur 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 ( Fig. 13.2 ).
