Cardiomyopathy
I. Hypertrophic Cardiomyopathy
II. Sudden Death
III. Dilated Cardiomyopathy
IV. Restrictive Cardiomyopathy
V. Specific Heart Muscle Disease
GLOSSARY
heart failure a failure of the heart to pump sufficient blood
from the chambers into the aorta; inadequate supply of blood
reaches organs and tissues. hemodynamics the study of the movement of blood and the
forces involved in the circulation of blood. mutations a permanent transmissible change in the genetic
material. outflow tract gradient marked thickness of the left ventricular
septum obstructs the blood flow from the left ventricle that is
to be delivered into the aorta. paroxysmal nocturnal dyspnea patient awakens at night from
sleep with severe shortness of breath and must dangle the legs
or walk to an open window; relief occurs only after several
minutes. sarcomere the contractile unit of a myofibril; sarcomeres are
repeating units, delimited by the Z bands, along the length of
the myofibril that make up the myocardium of the heart.
CARDIOMYOPATHY IS A RARE FORM OF HEART disease that affects only the heart muscle. The term cardiomyopathy is derived from the word cardio, the heart, and myopathy, which indicates a weakness or disturbance of the muscle. Heart muscle diseases of unknown cause are classified under the term cardiomyopathy.
- I. HYPERTROPHIC CARDIOMYOPATHY
Hypertrophic cardiomyopathy (HCM) is found through¬out the world with a prevalence in North America of 0.2%. Before the diagnosis of HCM is considered hyper¬tensive heart disease, a major cause of the left ventricle hypertrophy, and other causes of hypertrophy must be excluded. In practice HCM is defined and diagnosed by the demonstration of unexplained left ventricular hypertrophy. - II. SUDDEN DEATH
Death is most often sudden in HCM and unfortunately this may occur in asymptomatic patients, in those who were unaware that they have the disease, or in individuals with an otherwise stable course. - III. DILATED CARDIOMYOPATHY
Heart failure is rare in individuals younger than age 20. If congenital heart disease is excluded, the most common cause of heart failure in the young is idiopathic dilated cardiomyopathy (DCM). More than 50 known specific diseases of heart muscle can produce the signs, symptoms, and manifestations of idiopathic DCM. Some of these diseases include the following: - IV. RESTRICTIVE CARDIOMYOPATHY
Restrictive cardiomyopathy is rare in the western world and in Europe. Diseases that cause damage to the muscle and restrict the flow of blood into the ventricle include amyloidosis, sarcoidosis, hemochromatosis, scleroderma, Adriamycin toxicity, and heart involvement by infectious agents. The most common cause of restrictive cardiomyo-pathy, especially in tropical regions, is endomyocardial fibrosis. - V. SPECIFIC HEART MUSCLE DISEASE
Specific heart muscle disease usually produces a dilated form of cardiomyopathy with impaired systolic function. Restrictive physiology is seen with amyloid, sarcoid, neoplasm, radiation, scleroderma, hemochromatosis, and eosinophilic endomyocardial disease, in which eosino-philia is usually present. Rarely, myocardial tuberculosis is present with restrictive features. Amyloid heart disease and EMF are usually considered examples of RCM, but when cardiac involvement is associated with multiple organ disease, they qualify as specific heart muscle disease (see Table 1). - BIBLIOGRAPHY
Ackerman, M. J., McKenna, W. J., Thierfelder, L. et al. Mutations in the genes for cardiac troponins T and alpha tropomyosin in hypertrophic cardiomyopathy. N. Engl. J. Med., 332:1058–64, 1995.