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119 CARDIOMYOPATHIES AND MYOCARDITIS

119 CARDIOMYOPATHIES AND MYOCARDITIS
Harrison’s Manual of Medicine

119

CARDIOMYOPATHIES AND MYOCARDITIS

Dilated Cardiomyopathy (CMP)
Restrictive Cardiomyopathy
Hypertrophic Obstructive Cardiomyopathy (HOCM)
Myocarditis
Bibliography
DILATED CARDIOMYOPATHY (CMP)
Symmetrically dilated left ventricle (LV), with poor systolic contractile function; right ventricle (RV) commonly involved.
ETIOLOGY   Previous myocarditis or “idiopathic” most common; also toxins (ethanol, doxorubicin), connective tissue disorders, muscular dystrophies, “peripartum.” Severe coronary disease/infarctions or chronic aortic/mitral regurgitation may behave similarly.
SYMPTOMS   Congestive heart failure (Chap. 116); tachyarrhythmias and peripheral emboli from LV mural thrombus occur.
PHYSICAL EXAMINATION   Jugular venous distention (JVD), rales, diffuse and dyskinetic LV apex, S3, hepatomegaly, peripheral edema; murmurs of mitral and tricuspid regurgitation are common.
LABORATORY   ECG   Left bundle branch block and ST-T-wave abnormalities common.
CXR   Cardiomegaly, pulmonary vascular redistribution, pulmonary effusions common.
Echocardiogram   LV and RV enlargement with globally impaired contraction. Regional wall motion abnormalities suggest coronary artery disease rather than primary cardiomyopathy.

TREATMENT
Standard therapy of CHF (Chap. 116); vasodilator therapy with ACE inhibitor (preferred) or hydralazine-nitrate combination shown to improve longevity. Add beta blocker in ambulatory pts (Chap. 116). Chronic anticoagulation with warfarin, recommended for very low ejection fraction (<25%), if no contraindications. Antiarrhythmic drugs (Chap. 115) e.g., amiodarone, indicated for symptomatic or sustained arrhythmias but may cause proarrhythmic side effects; implanted internal defibrillator is often a better alternative. Possible trial of immunosuppressive drugs, if active myocarditis present on RV biopsy (controversial as long-term efficacy has not been demonstrated). In selected pts, consider cardiac transplantation.

RESTRICTIVE CARDIOMYOPATHY
Increased myocardial “stiffness” impairs ventricular relaxation; diastolic ventricular pressures are elevated. Etiologies include infiltrative disease (amyloid, sarcoid, hemochromatosis, eosinophilic disorders), myocardial fibrosis, and fibroelastosis.
SYMPTOMS   Are of CHF, although right-sided heart failure often predominates, with peripheral edema and ascites.
PHYSICAL EXAMINATION   Signs of right-sided heart failure: JVD, hepatomegaly, peripheral edema, murmur of tricuspid regurgitation. Left-sided signs may also be present.
LABORATORY   ECG   Low limb lead voltage, sinus tachycardia, ST- T-wave abnormalities.
CXR   Mild LV enlargement.
Echocardiogram   Bilateral atrial enlargement; increased ventricular thickness (“speckled pattern”) in infiltrative disease, especially amyloidosis. Systolic function is usually normal, but may be mildly reduced.
Cardiac Catheterization   Increased LV and RV diastolic pressures with “dip and plateau” pattern; RV biopsy useful in detecting infiltrative disease (rectal or fat pad biopsy useful in diagnosis of amyloidosis).
Note: Must distinguish restrictive cardiomyopathy from constrictive pericarditis, which is surgically correctable (Table 119-1).

Table 119-1 Constrictive Pericarditis vs. Restrictive Cardiomyopathy

TREATMENT
Salt restriction and diuretics ameliorate pulmonary and systemic congestion; digitalis is not indicated unless systolic function impaired or atrial arrhythmias present. Note: Increased sensitivity to digitalis in amyloidosis. Anticoagulation often indicated, particularly in pts with eosinophilic endomyocarditis. For specific therapy of hemochromatosis and sarcoidosis, see Chap. 345 and Chap. 318, respectively, in HPIM-15.

HYPERTROPHIC OBSTRUCTIVE CARDIOMYOPATHY (HOCM)
Marked LV hypertrophy; often asymmetric, without underlying cause. Systolic function is normal; increased LV stiffness results in elevated diastolic filling pressures.
SYMPTOMS   Secondary to elevated diastolic pressure, dynamic LV outflow obstruction, and arrhythmias; dyspnea on exertion, angina, and presyncope; sudden death may occur.
PHYSICAL EXAMINATION   Brisk carotid upstroke with pulsus bisferiens; S4, harsh systolic murmur along left sternal border, blowing murmur of mitral regurgitation at apex; murmur changes with Valsalva and other maneuvers (Chap. 112).
LABORATORY   ECG   LV hypertrophy with prominent “septal” Q waves in leads I, aVL, V5–6. Periods of atrial fibrillation or ventricular tachycardia are often detected by Holter monitor.
Echocardiogram   LV hypertrophy, often with asymmetric septal hypertrophy (ASH) and ³1.3 × thickness of LV posterior wall; LV contractile function excellent with small end-systolic volume. If LV outflow tract obstruction is present, systolic anterior motion (SAM) of mitral valve and midsystolic partial closure of aortic valve are present. Doppler shows early systolic accelerated blood flow through LV outflow tract. Carotid pulse tracing shows “spike and dome” configuration.

TREATMENT
Strenuous exercise should be avoided. Beta blockers, verapamil, or disopyramide used individually to reduce symptoms. Digoxin, other inotropes, diuretics, and vasodilators are contraindicated. Endocarditis antibiotic prophylaxis (Chap. 80) is necessary when outflow obstruction or mitral regurgitation is present. Antiarrhythmic agents, especially amiodarone, may suppress atrial and ventricular arrhythmias. In selected pts, LV outflow gradient can be reduced by dual-chamber permanent pacemaker or controlled septal infarction by ethanol injection into the septal artery. Consider implantable automatic defibrillator for pts with high-risk ventricular arrhythmias. Surgical myectomy may be useful in pts refractory to medical therapy.
Table 119-2 summarizes distinguishing features of the cardiomyopathies.

Table 119-2 Characteristics of the Cardiomyopathies

MYOCARDITIS
Inflammation of the myocardium most commonly due to acute viral infection; may progress to chronic dilated cardiomyopathy. Myocarditis may develop in pts with HIV infection or Lyme disease.
HISTORY   Fever, fatigue, palpitations; if LV dysfunction is present, then symptoms of CHF are present. Viral myocarditis may be preceded by URI.
PHYSICAL EXAMINATION   Fever, tachycardia, soft S1; S3 common.
LABORATORY   CK-MB isoenzyme may be elevated in absence of MI. Convalescent antiviral antibody titers may rise.
ECG   Transient ST-T-wave abnormalities.
CXR   Cardiomegaly
Echocardiogram   Depressed LV function; pericardial effusion present if accompanying pericarditis present.

TREATMENT
Rest; treat as CHF (Chap. 116); immunosuppressive therapy (steroids and azathioprine) may be considered if RV biopsy shows active inflammation, but long-term efficacy not demonstrated.

Bibliography

For a more detailed discussion, see Wynne J, Braunwald E: The Cardiomyopathies and Myocarditides, Chap. 238, p. 1359, in HPIM-15.

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