DILATED CMP

Dilated left ventricle (LV) with poor systolic contractile function; right ventricle (RV) often involved.

ETIOLOGY

Over 30% of pts have a familial form; mutations in TTN (encodes large sarcomeric protein titin) are the most common. Additional causes include myocarditis (e.g., viral and other infections, sarcoidosis, giant cell, eosinophilic), toxins (e.g., ethanol, antineoplastic agents [e.g., doxorubicin, trastuzumab, imatinib], hydroxychloroquine, heavy metals), connective tissue disorders, hypothyroidism, hemochromatosis, muscular dystrophies, “peripartum,” transient stress “takotsubo” CMP. Impaired LV function owing to severe coronary disease/infarction or chronic aortic/mitral regurgitation may behave similarly.

SYMPTOMS

Heart failure (Chap. 126: Heart Failure and Cor Pulmonale) often with secondary mitral and tricuspid regurgitation; tachyarrhythmias and peripheral emboli from LV mural thrombus occur.

PHYSICAL EXAMINATION

Jugular venous distention (JVD), pulmonary crackles, diffuse and dyskinetic LV apex, S₃, hepatomegaly, peripheral edema; murmurs of mitral and tricuspid regurgitation are common.

LABORATORY ECG

Left bundle branch block or nonspecific ST-T-wave abnormalities are common.

CXR

Cardiomegaly, pulmonary vascular redistribution, pulmonary effusions common.

ECHOCARDIOGRAM, CT, AND CARDIAC MRI

LV and RV enlargement with globally impaired contraction. Regional wall motion abnormalities suggest coronary artery disease rather than primary CMP.

B-TYPE NATRIURETIC PEPTIDE (BNP)

Level elevated in heart failure/CMP but not in pts with dyspnea due to lung disease.

Treatment: Dilated CMP

Possible use of immunosuppressive drugs if specific forms active myocarditis present on RV biopsy (e.g., for sarcoidosis or giant cell myocarditis). Standard therapy of heart failure (Chap. 126: Heart Failure and Cor Pulmonale): Diuretic for volume overload, vasodilator therapy with ACE inhibitor (preferred), angiotensin receptor blocker or hydralazine-nitrate combination, and beta-blocker therapy (e.g., metoprolol succinate, carvedilol) limit disease progression and improve longevity. Consider aldosterone antagonist therapy for pts with class II–IV heart failure, and chronic anticoagulation if there is accompanying atrial fibrillation (AF), prior embolism, or recent large anterior MI. Antiarrhythmic drugs (e.g., amiodarone or dofetilide) may be useful to maintain sinus rhythm in pts with AF. Consider implanted cardioverter defibrillator (ICD) for class II–III pts with LVEF <35%. For those with class III–IV heart failure, LVEF <35%, and prolonged QRS duration, consider cardiac resynchronization therapy (CRT) using biventricular pacing; greatest benefit in pts with LBBB and QRS ≥150 msec (ICD and CRT functions can be provided by a single implanted device). In selected pts, consider cardiac transplantation.