Cardiomyopathy

A functional abnormality of the ventricular myocardium.

Cardiomyopathy generally refers to a diffuse or generalized myocardial disorder, often without a known underlying cause; involvement of the myocardium is primary (idiopathic). However, valvular heart disease, hypertension, or coronary artery disease may coexist with primary cardiomyopathy. The main types of cardiomyopathy, which may overlap, are dilated (congestive), hypertrophic, and restrictive (infiltrative).

Dilated Cardiomyopathy

Myocardial disorders characterized by systolic dysfunction with dilation of chambers and an increase in muscle mass without full compensatory increase in wall thickness.

About 10% of patients with dilated cardiomyopathy are > 65. Dilated cardiomyopathy is usually chronic, and patients present with effort dyspnea and fatigability because of elevated left ventricular diastolic pressure and low cardiac output. Less commonly, when an infective agent is the cause, onset is acute and is associated with fever; this syndrome is called acute myocarditis, which is rare among the elderly. Usually, no specific cause of myocarditis can be identified, although the disorder has been attributed to viruses (especially coxsackievirus) and rickettsiae. Acute myocarditis may be difficult to diagnose clinically.

The diagnosis of dilated cardiomyopathy is made by excluding other causes of diffuse myocardial dysfunction (eg, doxorubicin toxicity, radiation damage, chronic alcoholism) and is confirmed by echocardiographic evidence of four-chamber dilation with depressed systolic ventricular function. Dilated cardiomyopathy may be misdiagnosed as heart failure caused by coronary artery disease.

Treatment should be aimed at managing heart failure due to systolic dysfunction. Immunosuppressive therapy has not been shown to be effective as treatment for myocarditis.

Hypertrophic Cardiomyopathy

A disease of the myocardium characterized by marked ventricular hypertrophy and a nondilated left ventricle without other known cardiovascular disease.

Hypertrophic cardiomyopathy is relatively common among the elderly (4% in one series) and more common among women than among men. Causes of hypertrophic cardiomyopathy in the elderly are not well defined. Most cases are associated with severe, poorly controlled systemic hypertension and may be acquired. However, some cases appear similar to those in younger patients and are probably congenital.

Hypertrophic cardiomyopathy is characterized by normal or small chamber size, increased wall thickness, hyperdynamic systolic ejection, and impaired diastolic filling. Ventricular hypertrophy may be substantial and is usually concentric, especially in elderly patients with a history of hypertension, but it may be asymmetric, as in patients with congenital hypertrophic cardiomyopathy.

In some patients, septal thickening narrows the left ventricular outflow tract. During left ventricular ejection, the anterior leaflet of the mitral valve is drawn toward the septum, further narrowing the outflow tract and causing a systolic gradient. In other patients, a systolic gradient results from obstruction at the level of the mid left ventricular cavity, mitral annulus, or, rarely, the apex.

Symptoms and Signs

Elderly and younger patients commonly present with chest pain, dyspnea, dizziness, palpitations, and syncope (due to tachyarrhythmias or decreased cardiac output resulting from outflow obstruction). Although CAD may be present, chest pain does not necessarily indicate CAD. Ischemic infarction occasionally occurs, even in patients with normal coronary arteries. Ventricular tachycardia, which increases the likelihood of sudden death, may be present but appears to be less common in elderly than in younger patients. Supraventricular tachyarrhythmias are also common as the left atrium enlarges. Atrial fibrillation may cause rapid hemodynamic deterioration.

A late systolic murmur that is heard from the lower left sternal border to the apex and terminates before the second heart sound is characteristic. Other signs include a rapid bisferious carotid pulse and a prominent fourth heart sound. Provocative maneuvers (eg, Valsalva maneuver, standing after squatting) accentuate the systolic murmur, which decreases or disappears when the patient squats; however, many elderly patients cannot adequately perform these maneuvers. With the patient supine, passive lifting of the legs to 90° increases venous return, enlarges the left ventricular outflow tract, and decreases the murmur. The murmur may also disappear as systolic function deteriorates and the cavity dilates.

Diagnosis

Hypertrophic cardiomyopathy should be considered in patients with a systolic murmur and anginal chest discomfort or syncope. Often, the disorder is not suspected because prominent carotid pulses, basal systolic murmurs, and fourth heart sounds are common among elderly persons without heart disease.

Echocardiography is diagnostic and characterizes the pattern of left ventricular hypertrophy, the site and severity of dynamic outflow obstruction, systolic and diastolic function, and associated pathologies. An ECG typically shows left atrial abnormality and left ventricular hypertrophy; about 20% of patients have left anterior fascicular block. Septal hypertrophy may produce nonspecific inferior and apical Q waves mimicking myocardial infarction.

Differentiating the disorder from aortic valve stenosis or CAD with papillary muscle dysfunction is important because therapy differs. The murmur must also be differentiated from murmurs due to aortic sclerosis, mitral regurgitation, or mitral valve prolapse, all of which are common among the elderly.

Prognosis and Treatment

Elderly patients have a better prognosis than younger patients, with less likelihood of sudden death.

Treatment of elderly and younger patients is similar. A -blocker is used most commonly and provides relief of dyspnea and chest pain. Calcium channel blockers with negative inotropic properties (eg, verapamil) and possibly ACE inhibitors (in low doses) may help. Nitroglycerin, diuretics, vasodilators, digoxin, and other positive inotropic drugs may exacerbate outflow obstruction and symptoms.

Patients who have palpitations, presyncope, or syncope (which are less common among elderly than among younger patients) should be monitored for malignant arrhythmias. If patients have syncope, an electrophysiologic study should be performed to determine whether sustained monomorphic ventricular tachycardia can be stimulated. Patients who have monomorphic sustained ventricular tachycardia with symptoms should be considered for an automatic implantable cardioverter-defibrillator.

Myomectomy or an electronic pacemaker can be considered for patients who are very symptomatic and have a significant ventricular outflow gradient refractory to medical therapy.

Antimicrobial prophylaxis against infective endocarditis is indicated before invasive and surgical procedures. (see Table 90-1)

Restrictive Cardiomyopathy

Myocardial disorders characterized by rigid, noncompliant walls of one or both ventricles (most commonly the left) that resist diastolic filling.

In restrictive cardiomyopathy, increased myocardial stiffness is secondary to infiltrative pathology. Amyloid heart disease is a common cause in the elderly. Other causes include postradiation damage and postoperative pericarditis.

The atria are often dilated, and systolic function, as well as diastolic function, is impaired. Other findings include small ventricles, thickened walls (of both ventricles and of the interatrial septum), a sparkling of the thickened myocardium (seen on an echocardiogram), low QRS voltage and arrhythmias or conduction defects (seen on an ECG), and elevated ventricular filling pressures.

Restrictive cardiomyopathy caused by amyloid heart disease is differentiated from other disorders characterized by age-related amyloid accumulation in the heart. One such disorder is senile cardiac amyloidosis, a separate pathologic entity that is present in 80% of persons > 95. The heart appears normal, but microscopic examination detects amyloid accumulation, usually in the atria. Amyloid accumulation is associated with atrophied myocardial fibers. Two immunologically distinct forms exist: one with only atrial deposits, and the other with ventricular deposits and often with minor extracardiac deposits. Senile cardiac amyloidosis is not characterized by cardiomegaly. Primary amyloidosis, another distinct pathologic entity, is characterized by cardiomegaly. It may also occur in the elderly but is much rarer.

Treatment of restrictive cardiomyopathy is the same for elderly and younger patients. It is directed at ameliorating the primary cause if possible and at optimizing ventricular filling and enhancing diastolic function.