What Is Hypertrophic Cardiomyopathy? (HCM)

Cardiomyopathy is a condition in which the muscle of the heart is abnormal in the absence of an apparent cause. This terminology is purely descriptive and is based on the Latin deviation. There are three types of cardiomyopathy: "hypertrophic", "dilated" and "restrictive". The main feature of Hypertrophic Cardiomyopathy is an excessive thickening of the heart muscle (hypertrophy literally means to thicken). Heart muscle may thicken in normal individuals as a result of high blood pressure or prolonged athletic training. In Hypertrophic Cardiomyopathy (HCM), however the muscle thickening occurs without an obvious cause. In addition, microscopic examination of the heart muscle in HCM shows abnormal. The normal alignment of muscle cells is absent and this abnormality is called "myocardial disarray"

How Common is Hypertrophic Cardiomyopathy?

Hypertrophic Cardiomyopathy is a relatively uncommon heart disease. Its exact frequency is unknown. A paper issued by Dr. Barry Maron of the Minneapolis Heart Institute, August 1995, estimated that 1 in 500 births could be effected by HCM. In the United Kingdom it is estimated that approximately 10,000 people have the condition. It is not possible to estimate the number of affected people in the United States at this time. It is one of the goal of this organization to establish how many people in the USA are affected.

When Does Hypertrophic Cardiomyopathy Develop?

Although hypertrophy may be present at birth or in childhood, it is much more common for the heart to appear normal at this time. Occasionally, Hypertrophic Cardiomyopathy is the cause of a stillbirth or develops during infancy, with heart failure which may be fatal. However, hypertrophy more commonly develops in association with growth and is usually apparent by the late teens or early twenties. After this time it appears that there is no significant change in muscle thickness in the years of adult life. Children and adolescents with the condition usually come to attention when a family screening is performed after an adult in the family is found to be affected. Approximately 50% of adults with the condition present with symptoms. In the remainder the diagnosis is made during family screening or following the detection of a murmur or abnormality on routine electrocardiogram (ECG).

What Symptoms Does Hypertrophic Cardiomyopathy Cause?

There is no particular symptom or complaint which is unique Hypertrophic Cardiomyopathy. Symptoms may occur at any stage in a person's life even though the condition may have been present for some time. The reason for the onset of symptoms is often not clear.

Shortness of Breath

Exercise capacity may be limited by breathlessness and fatigue. Most individuals experience only mild exercise limitations, but occasionally limitation is severe and a minority may have shortness of breath at rest.

Chest Pain

Chest pain is a common symptom. It is usually brought on by exertion and relieved by rest, but pain may occur at rest or during sleep and may persist. The cause of the pain is thought to be insufficient oxygen supply to the myocardium. In Hypertrophic Cardiomyopathy the main coronary arteries are usually normal, but the greatly thickened muscle demands and increased oxygen supply which cannot be met in some circumstances.


Palpitation is an uncomfortable awareness of the heart beat. People may occasionally feel an extra beat or a skipped beat and this is usually normal. Sometimes an awareness of the heart beating does suggest and irregular heart rhythm. In this case, palpitation may start suddenly, appear to be very fast and may be associated with sweating or light-headedness. The cause of such episodes should be determined and treated.

Light-Headedness and Blackouts

Persons with the condition may experience light-headedness, dizziness and more seriously, blackouts. Episodes may occur in association with exercise, with palpitations or without any apparent provocation. The reasons for these episodes are not always clear. They may be due to an irregularity if the heart beat, or fall in blood pressure. Episodes of light-headedness and certainly a blackout should be reported to one's doctor and investigated.

Physical Examination

In the majority of patients with Hypertrophic Cardiomyopathy, the physical examination is unremarkable and the abnormalities may be subtle. Most patients have forceful or jerky pulse and a forceful heart beat, which can be felt on the left side of the chest. Both of these reflect the thickened, strongly contracting heart. However the most obvious abnormality on physical examination is a heart murmur, which is present in 30 - 40% of patients.

Is a CURE available??

At present there is no cure for Hypertrophic Cardiomyopathy. There is a slight possibility that some drugs may decrease the degree of muscle thickening. And more recently studies are being performed on the use of pacemakers to reduce the effects of "obstruction". However, no treatment has been shown to return the heart to normal. Research continues in this area. Developments are most likely to come from the early detection of persons carrying the gene for Hypertrophic Cardiomyopathy and treating them to prevent the development of hypertrophy. The achievement of this goal will require much further research.

The preceding was referenced at the Hypertrophic Cardiomyopathy Association.

Return to Marcela's Heart Transplant page by pressing the "Home" button below.

Nedstat Counter