Cardiomyopathy II: Dilated Cardiomyopathy

Dilated cardiomyopathy results from various factors including hypertension, viral infections like Coxsackievirus B, cardiotoxic chemotherapeutic agents such as doxorubicin, and endocrine disorders like thyrotoxicosis. Heavy alcohol intake also contributes to heart muscle weakening. When no specific cause is identified, the condition is termed idiopathic dilated cardiomyopathy, though familial cases often have genetic etiology.

Dilated cardiomyopathy causes diffuse inflammation and degeneration of heart fibers, resulting in ventricular dilation and impaired systolic function. The dilated ventricles increase wall stress and decrease cardiac output, triggering compensatory mechanisms like the renin-angiotensin-aldosterone system and sympathetic nervous system activation. These responses initially maintain cardiac output but eventually worsen heart failure through myocardial remodeling and increased afterload.

Early symptoms include reduced exercise capacity, fatigue, dyspnea at rest, and palpitations. As the disease progresses, patients may develop paroxysmal nocturnal dyspnea, orthopnea, dry cough, and abnormal S3 and S4 heart sounds. Physical examination may reveal pulmonary crackles, edema, weak peripheral pulses, pallor, hepatomegaly, and jugular venous distention.

Chest X-ray reveals cardiomegaly with signs of pulmonary venous hypertension and pleural effusion. An electrocardiogram may show tachycardia, bradycardia, or dysrhythmias with conduction abnormalities. Laboratory studies showing elevated B-type natriuretic peptide levels indicate heart failure and confirm the diagnosis of dilated cardiomyopathy.

Diuretics like furosemide and nitrates decrease preload, while ACE inhibitors reduce afterload. Beta-blockers such as metoprolol and aldosterone antagonists like spironolactone control neurohormonal stimulation. Antidysrhythmics treat dysrhythmias, and anticoagulation therapy reduces the risk of systemic embolization from clots forming in cardiac chambers.

A ventricular assist device allows the heart to rest or serves as a bridge to transplant. Cardiac resynchronization therapy improves contraction coordination by electrically stimulating both ventricles. An implantable cardioverter-defibrillator prevents sudden cardiac death by monitoring rhythm and delivering shocks for dangerous arrhythmias. Heart transplant or destination therapy may be considered for end-stage disease.

Dilated cardiomyopathy is characterized by ventricular chamber enlargement and systolic dysfunction, distinguishing it from restrictive cardiomyopathy and hypertrophic forms. Each type requires distinct diagnostic and therapeutic approaches. Understanding these differences helps clinicians differentiate between conditions and provide optimal patient management tailored to the specific cardiomyopathy type.