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.
(For additional information, see Chapter 14 on details of the infiltrative diseases of the heart.)
