Cardiomyopathy takes two basic forms: dilated cardiomyopathy, and hypertrophic cardiomyopathy.
Dilated cardiomyopathy occurs when the ventricle (generally the left ventricle) becomes dilated, and the ventricular muscle weak and relatively flaccid. As a result, the pumping action of the ventricle becomes weak; the amount of blood pumped with each heart beat drops; and the body’s organs do not receive their full quotient of blood. Probably the best measure of the severity of a person’s dilated cardiomyopathy is the left ventricular ejection fraction (LVEF), a measure of the percentage of the left ventricle’s volume that is ejected with each heart beat. Normally, the LVEF is greater than 50%. Patients generally experience a reduction in exercise capacity as the LVEF approaches 40%, and often experience symptoms at rest (weakness, fatigue, shortness of breath) when the LVEF is in the 20 - 30% range.
As dilated cardiomyopathy progresses, symptoms of shortness of breath, weakness, fatigue, and leg swelling worsen. The propensity to develop life-threatening arrhythmias (ventricular tachycardia and ventricular fibrillation) also increases as the LVEF drops. The mainstay of therapy is drug treatment: digitalis, diuretics, ACE inhibitors and beta blockers are commonly used. For many patients, a new breed of pacemakers that synchronize and optimize ventricular contraction can improve both symptoms and survival. (Read about this new type of pacing for heart failure here.) Various types of cardiac assist devices (essentially, implantable pumps) are also progressing rapidly. Click here for a complete review of heart failure and its treatment.
Hypertrophic cardiomyopathy is usually a genetic condition that tends to run in families. It is characterized by a thickening of the ventricular muscle that results in muscle “stiffness.” This stiffness can lead to episodes of extreme shortness of breath in some patients, especially during exercise. The thickening of the heart muscle can also cause an obstruction in the left ventricle similar to that seen with aortic stenosis. And some patients with hypertrophic cardiomyopathy can develop ventricular tachycardia and ventricular fibrillation, and some thus require insertion of an implantable defibrillator. (Click here to read more about hypertrophic cardiomyopathy.)
