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FINDING out whether you’re among the one in 500 people with hypertrophic cardiomyopathy could save your life - and could prevent the sudden death of someone you love, says the October 2013 issue of the Harvard Medical School’s Harvard Heart Letter.

Hypertrophic cardiomyopathy (HCM), despite its long name, often makes headlines - it’s the most common reason why young, apparently healthy athletes collapse and die.

“Some of these deaths might have been avoided had the individuals known they had a close relative with the same condition,” says Dr. Christine Seidman, professor of medicine and genetics at Brigham and Women’s Hospital and Harvard Medical School.

“People need to know that in a large percentage of cases, this is a genetic, inherited disease,” says Dr. Seidman, whose team discovered the first genetic mutation that causes HCM.

“When we recognize that individuals have this disease, we can help manage their symptoms and reduce their risk of really devastating outcomes like sudden death.”

Although it is a genetic disease, HCM can appear at almost any stage of life, from childhood to old age.

“For many years it was felt that if you didn’t have manifestations of HCM by age 35 to 40, you probably would never get the disease. That is wrong,” says the doctor.

“We now know that some of the mutations result in very late manifestations of HCM, after the age of 50.”

Thus, genetic testing or lifetime follow-up care is needed.

While many individuals with HCM don’t have any symptoms, when they do develop, symptoms include shortness of breath during exercise, chest pain, heart palpitations, dizziness and sometimes fainting.

Sometimes the first symptom is sudden death - the absence of symptoms doesn’t mean there’s nothing going on inside the heart.

Under normal circumstances, the left ventricle must relax quickly to fill with oxygen-rich blood and then, with perfect timing, contract forcefully to propel it into the body.

However, having HCM means there’s thickening of the left ventricle, the hardest-working chamber of the heart.

In nearly all cases, the worst thickening is in the septum, the wall between the left and right ventricles.

Blood must flow past the septum to exit the heart but, in some individuals with HCM, over 35 percent to 50 percent of the time, the thickening results in obstruction to the outward flow of blood into the aorta, says Seidman.

Also, there may be changes to or interference with the mitral valve separating the upper and lower chambers of the left side of the heart, allowing blood to leak backward.

Clearly, HCM is more dangerous when blood flow is obstructed, but the degree of obstruction varies.

Besides, some individuals almost have no obstruction when at rest but massive obstruction during exercise or after a meal, adds the health letter.

Aside from obstruction, HCM sufferers also have the problem of a thick left ventricle which doesn’t relax as it should, resulting in too much pressure on the left atrium - the upper heart chamber that’s trying to fill the ventricle with blood - and the atrium gets stretched.

This results in atrial fibrillation, an abnormal heart rhythm.

Left untreated, HCM can have three outcomes - not mutually exclusive:

• Sudden cardiac death when, unpredictably, heart rhythm becomes irregular and abnormally fast - fortunately, this is rare.

A person with HCM has a 1 percent annual risk of sudden cardiac death.

• Heart failure

• Atrial fibrillation, often associated with heart failure.

Atrial fibrillation increases risk of stroke.

Only genetic tests can show whether a person carries the mutation, and only clinical tests can show whether a person has HCM - “Sadly, many individuals only come to us when a family member has died of HCM,” says Seidman.

“It is so very important that anyone with HCM have first-degree family members screened clinically - not just once, but over the long term. Or there should be genetic tests to ascertain who is at risk of having or developing the disease. That is really important.”

Dr. Seidman believes 70 percent of individuals with thickening of the left ventricle not explained by some other disease carry at least one of the more than 1,400 mutations known to cause HCM and most if not all of the remaining 30 percent likely have HCM mutations not yet discovered.

HCM doesn’t just strike individuals but families - half of an affected person’s first-degree relatives (parents, siblings, and children) probably carry the mutation.

A person who inherits one of these harmful genes (dominant mutations) from either parent will develop HCM and has a 50-50 chance of passing the mutation on to his or her children.

Since genetic testing can be expensive, and insurance coverage varies, the Hypertrophic Cardiomyopathy Association (www.4hcm.org) offers:

• financial support as well as advice to families considering genetic testing

• a tool that individuals with HCM can use to estimate their risk of sudden cardiac death

While individuals who carry HCM genes are at high risk of developing the disease, not all do - thus, anyone carrying the HCM genes needs regular testing to look for the first signs of disease, as early treatment can change the course of HCM.

Treatment of HCM varies:

• For those with HCM but no symptoms - Avoiding strenuous activity - especially competitive athletics - is essential.

• Because other forms of heart disease shorten survival in those with HCM, individuals with HCM should aggressively reduce heart disease risk factors.

• Individuals whose HCM has begun to obstruct blood flow in the heart, even if they have no symptoms, should be particularly careful to drink plenty of water and to avoid high-dose diuretic and medications that dilate the blood vessels.

• Drug therapy - can help control HCM symptoms such as shortness of breath, heart palpitations and chest discomfort.

• Surgery may be the best option, when drug therapy isn’t enough - An open-heart procedure called myectomy removes excess heart tissue and relieves obstructed blood flow.

• Alcohol septal ablation - for patients who are not good candidates for surgery, or who prefer to avoid it - which uses a catheter to inject alcohol into selected arteries feeding the thickened area, killing off excess tissue and relieving obstruction.

• New treatments are in clinical trials - exciting research is under way - Dr. Seidman is urging individuals with a family history of HCM to participate and be part of the progress, concludes the health letter.