by Nicole Evans M.D.

Created on: November 02, 2008   Last Updated: October 18, 2009

Dilated cardiomyopathy is enlargement of the left or right ventricle of the heart. This dilation causes a loss of cardiac contractile function which loss of function eventually results in congestive heart failure, arrhythmias and thrombus (clot) formation in the heart.

The causes of dilated cardiomyopathy can be broadly grouped into four categories: infectious, toxic, endocrine, and metabolic. Within these categories there are often both irreversible and reversible causes of the dilated cardiomyopathy.

Infectious Causes of Dilated Cardiomyopathy:

Irreversible- viral myocarditis (Coxsackie A or B virus, Echovirus, HIV, Cytomegalovirus, Influenza, Epstein-Barr virus, Hepatitis B virus or adenovirus)

Reversible- unfortunately none

Toxic Causes of Dilated Cardiomyopathy:

Irreversible- chemotherapeutic agent Doxorubicin (Adriamycin), cocaine, heavy metals such as lead, mercury and cobalt

Reversible- prolonged alcohol abuse

Endocrine Causes of Dilated Cardiomyopathy:

Irreversible- acromegaly (disorder of excess growth hormone), pheochromocytoma (adrenal medullary tumor)

Reversible- hypothyroid or hyperthyroid disease

Metabolic Causes of Dilated Cardiomyopathy:

Reversible- hypocalcemia, hypophosphatemia, thiamine deficiency (wet beriberi), selenium deficiency

Usually reversible- pregnancy

Usually irreverisble- Neuromuscular disease, Idiopathic (unknown cause)

Irreversible- Genetic, accounting for approximately 20% of cases of dilated cardiomyopathy

The pathophysiology for the development of dilated cardiomyopathy is similar despite the cause. The ventricles become dilated and stiff.
The heart valves become dilated as well. Mitral valve and tricuspid valve regurgitation occurs due to misalignment of the papillary muscles. Arrhythmias occur and mural (endocardial wall) thrombi may form.

The symptoms of dilated cardiomyopathy are usually minor until heart failure develops. Symptoms then include easy fatigueability, shortness of breath on exertion, increasing breathlessness on reclining (orthopnea), sudden awakening in the night with severe breathlessness (paroxysmal nocturnal dyspnea). Other symptoms include chest pain due to increased oxygen demands of the enlarged ventricles. Additionally, the mural thrombus may throw emboli, resulting in brain infarcts with subsequent neurologic deficits.

Dilated cardiomyopathy can be diagnosed when a chest x-ray shows an enlarged cardiac silhouette and pulmonary venous congestion. Echocardiography (ultrasound of the heart) shows enlarged ventricles and possibly atria, regurgitant valves, and low ventricular ejection fractions. An electrocardiogram (ECG) may show ventricular hypertrophy, bundle branch blocks, nonspecific ST segment or T wave changes and/or arrhythmias. The most common arrhythmia detected is the irregularly irregular rhythm with lack of P waves known as atrial fibrillation.

There may be extra heart sounds due to the ventricular stiffening. An S3 or S4 gallop may be heard. Regurgitant murmurs may be auscultated and pulmonary rales, a sign of pulmonary edema from left-sided congestive heart failure, may be picked up as well.

The treatment for dilated cardiomyopathy involves addressing any reversible causes and providing supportive care. Heart failure should be medically managed, i.e. ACE inhibitors, beta-blockers, etc. Implanted automatic cardiac defibrillators should be placed for patients with life-threatening arrhythmias. A heart transplant is eventually required in many individuals.

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