Family ties heighten the risk of enlarged heart.For years, heart researchers have speculated about the cause of cardiomyopathy Cardiomyopathy Definition
Cardiomyopathy is a chronic disease of the heart muscle (myocardium), in which the muscle is abnormally enlarged, thickened, and/or stiffened. , a mysterious and sometimes deadly disease of the heart muscle. Now, a study suggests that genetic heritage may play a stronger role inthe development of cardiomyopathy than previously believed.
In some cases, alcohol abuse or a viral infection viral infection,
n an infection by a pathogenic virus. A virus acts on the cell nucleus, taking over the genetic material within the nucleus and replicating itself. damages the heart muscle so that the lower chambers, or ventricles Ventricles
The two chambers of the heart that are involved in pumping blood. The right ventricle pumps blood into the lungs to receive oxygen. The left ventricle pumps blood into the circulation of the body to deliver oxygen to all of the body's organs and tissues. , enlarge and fail to pump blood effectively. However, most cases of cardiomyopathy occur for no known reason.
Although researchers had dentified several large families with a tendency to the disease, they considered such "familial" cardiomyopathy uncommon. But when cardiologists at the Mayo Clinic in Rochester, Minn., noticed a number of families prone to the disease, they decided to take a closer look at the frequency of familial cardiomyopathy.
Mayo geneticist ge·net·i·cist
A specialist in genetics.
a specialist in genetics.
geneticist Virginia V. Michels and her colleagues tudied 59 unrelated individuals with cardiomyopathy of unknown origin, as well as 315 of their relatives. Using echocardiography Echocardiography Definition
Echocardiography is a diagnostic test that uses ultrasound waves to create an image of the heart muscle. Ultrasound waves that rebound or echo off the heart can show the size, shape, and movement of the heart's valves and , a sound-wave method of determining the heart's size, the researchers discovered that 18 relatives of 12 cardiomyopathy patients also suffered from the heart ailment.
Thus, the team concludes that 12 of the 59 cardiomyopathy patients (20 percent) had a familial form of the disease. This suggests that cardiomyopathy may run in families more frequently than believed, says James H. Chesebro, a coauthor of the study. The researchers describe their findings in the Jan. 9 NEW ENGLAND JOURNAL OF MEDICINE The New England Journal of Medicine (New Engl J Med or NEJM) is an English-language peer-reviewed medical journal published by the Massachusetts Medical Society. It is one of the most popular and widely-read peer-reviewed general medical journals in the world. .
Of the 18 relatives identified, 15 first learned that they had cardiomyopathy during the study, Michels says, and eight of these had no idea they had any heart problem at all.
Healthy people with a family history of cardiomyopathy may run a risk of eventually developing the disease, the researchers note. The team identified 22 healthy relatives who had slightly enlarged ventricles. Although their hearts still pumped normally, Michels says she wonders whether the slight swelling of the ventricles represents an early sign of a diseased heart.
"It could mean nothing, or it could mean that these are people who have a genetic predisposition genetic predisposition Molecular medicine The tendency to suffer from certain genetic diseases–eg, Huntington's disease, or inherit certain skills–eg, musical talent to developing full-blown disease," Michels says. Her team will monitor these 22 people to see whether they develop cardiomyopathy later in life.
Scientists still don't know Don't know (DK, DKed)
"Don't know the trade." A Street expression used whenever one party lacks knowledge of a trade or receives conflicting instructions from the other party. how cardiomyopathy originates. Indeed, Michels says, the new findings don't rule out the possibility of other factors playing a role in the disease. The observation that cardiomyopathy runs in families doesn't necessarily mean the cause is genetic. Michels notes that family members often share the same environment, which may harbor some unidentified, heart-damaging factor -- a virus, perhaps, or a dietary deficiency (SN: 9/27/86, p.201).
However, she suspects that one or more genes play a hefty role in making some people vulnerable to the disease. The Mayo team is now searching for a specific genetic culprit. Identifying the defective gene or genes might enable researchers to pinpoint the biochemical defect causing the muscle damage, and perhaps to devise a treatment for preventing the heart's decline, Michels says.
The new evidence suggests that people with a family history of cardiomyopathy should ask their doctors about getting an echocardiogram ech·o·car·di·o·gram
A visual record produced by echocardiography.
A non-invasive ultrasound test that shows an image of the inside of the heart. , Chesebro adds. This painless test can reveal swollen ventricles and impaired pumping ability.
Shortness of breath Shortness of Breath Definition
Shortness of breath, or dyspnea, is a feeling of difficult or labored breathing that is out of proportion to the patient's level of physical activity. , weakness and other symptoms of cardiomyopathy might seem harmless, yet the disease, if left untreated, can leave some people prone to a type of erratic heartbeat that can cause sudden death, Chesebro notes. With early diagnosis and treatment, doctors hope to prevent such lethal heartbeats and forestall further weakening of the body's powerhouse pump, he adds.