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Shortness of breath (dyspnea) occurs in approximately 90% of symptomatic individuals with HCM. It occurs due to a combination of abnormalities, including poor relaxation of the stiff, thickened heart muscle (diastolic dysfunction), reduced blood flow into the main heart pumping chamber (impaired ventricular filling), and increased pressures in the left atrium and pulmonary veins.

Fainting and near-fainting (syncope and near-syncope) can occur in HCM patients due to inadequate cardiac output during times of increased demand (such as physical exertion or severe stress). Serious arrhythmias can also result in fainting episodes; in fact, such arrhythmias are a top cause of sudden death in otherwise healthy children and young adults.

Chest pain (angina pectoris) occurs in up to three-fourths of symptomatic patients.The discomfort is a result of an imbalance between a reduced oxygen supply to the heart (because of thickened and narrowed heart arteries) and increased demand (due to greater heart muscle).
What noninvasive testing can be used to evaluate patients with suspected DCM or HCM?


Useful tests include electrocardiography (ECG), chest x-ray, and ultrasound (echocardiography).
In symptomatic individuals, the ECG is usually abnormal, but no specific findings are diagnostic of either DCM or HCM.

A chest x-ray will demonstrate an enlarged cardiac silhouette in DCM patients and in some HCM patients.

An echocardiogram provides the most useful and specific information. In DCM patients, severe dilatation of the ventricles is demonstrated, and an accurate estimation can be made of the impairment of heart function. In HCM patients, thickening of the left ventricle is the cardinal feature. Other findings include narrowing of the outflow tract through which blood flows from the left ventricle and out through the aortic valve and into the aorta, a small left ventricular cavity size, and abnormal motion of the mitral valve.


What medical and invasive therapies are available to treat HCM patients?

Beta-blockers (examples include metoprolol and atenolol), which are drugs that slow down the heart rate, are the cornerstone of medical therapy for HCM. In up to two-thirds of patients, they reduce the frequency of chest pain, shortness of breath, and near fainting.
Calcium channel blockers, such as verapamil, have also been utilized with good success; they appear to help the thick heart muscle relax better (decreased diastolic dysfunction) and can reduce the outflow tract obstruction.

Insertion of a pacemaker may be useful in some patients with an outflow gradient and severe symptoms.

In high-risk patients, especially in those who have had serious ventricular arrhythmias or aborted sudden death, an implantable cardiac defibrillator (ICD) should be inserted.

Surgical and invasive options exist for severely symptomatic patients. A surgical myomectomy, or excision of excess heart muscle, has a mortality rate of 3% or less in large centers. Surgery results in long-term improvement in symptoms and exercise capacity in most patients.

A nonsurgical invasive approach involves injection of alcohol into 1 of the arteries supplying the excessively thickened septal wall; this is done via left catheterization (a small incision is made in a leg or arm artery to allow delivery of a catheter into the specific artery under x-ray guidance). Short-term results in experienced centers have been promising, but long-term results are still not available.

What is restrictive cardiomyopathy (RCM), and what are the most common forms?


Restrictive cardiomyopathy (RCM)—the least common of the cardiomyopathies—is characterized by abnormal relaxation of the heart muscle in the presence of normal ejection fraction. RCM is often classified into myocardial (throughout the heart muscle) and endocardial (from inside the ventricle).

The most common myocardial forms are amyloidosis and sarcoidosis (infiltrative diseases); scleroderma or idiopathic (noninfiltrative diseases); and hemochromatosis, glycogen storage diseases, and Fabry's disease (storage diseases).

Infiltrative diseases refer to abnormal proteins and cells generated by certain disease states that penetrate the heart muscle. Noninfiltrative diseases are typically diseases related to activation of the autoimmune system or due to a genetic abnormality that activates abnormal cardiac muscle growth, where the storage diseases refer to genetic abnormalities that lead to abnormal storage of sugars and other substances inside the heart muscle cells.

The most common endocardial forms of RCM are carcinoid, metastatic malignancy (spread of cancer), and endomyocardial fibrosis. READMORE...