Hypertrophic Cardiomyopathy

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Hypertrophic cardiomyopathy (HCM , or HOCM when obstructive) is a condition in which muscle tissues of the heart become thickened without an obvious cause. The parts of the heart most commonly affected are the interventricular septum and the ventricles. This results in the heart being less able to pump blood effectively and also may cause electrical conduction problems. Specifically affected are the bundle branches that conduct impulses through the interventricular septum and into the Purkinje fibers, as these are responsible for the depolarization of contractile cells of both ventricles.

People who have HCM may have a range of symptoms. People may be asymptomatic, or may have fatigue, leg swelling, and shortness of breath. It may also result in chest pain or fainting. Symptoms may be worse when the person is dehydrated. Complications may include heart failure, an irregular heartbeat, and sudden cardiac death.

HCM is most commonly inherited in an autosomal dominant pattern. It is often due to mutations in certain genes involved with making heart muscle proteins. Other inherited causes of left ventricular hypertrophy include Fabry disease and Friedreich's ataxia. Other considerations for causes of enlarged heart are athlete's heart and hypertension (high blood pressure). Making the diagnosis of HCM often involves a family history or pedigree, an electrocardiogram, echocardiogram, and stress testing. Genetic testing is recommended for affected people and their family members. HCM can be distinguished from other inherited causes of cardiomyopathy by its autosomal dominant pattern, whereas Fabry disease is X-linked, and Friedreich's ataxia is inherited in an autosomal recessive pattern.

Treatment depends on symptoms and other risk factors. Medications may include beta blockers, verapamil or disopyramide. An implantable cardiac defibrillator may be recommended in those with certain types of irregular heartbeat. Surgery, in the form of a septal myectomy or heart transplant, may be done in those who do not improve with other measures. With treatment, the risk of death from the disease is less than one percent per year.

HCM affects up to one in 500 people. People of all ages may be affected. The first modern description of the disease was by Donald Teare in 1958.