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hypertrophic cardiomyopathy (HOCM)

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Alternative Names 
hypertrophic obstructive cardiomyopathy, idiopathic hypertrophic subaortic stenosis

Hypertrophic cardiomyopathy is a condition in which a portion of the heart muscle is abnormally thick. This can make it harder for blood to flow into and out of the heart and cause other problems.

What is going on in the body? 
One of the main blood-pumping chambers of the heart, called the left ventricle, is affected in hypertrophic cardiomyopathy. The walls of this heart chamber become abnormally thick for unknown reasons. The abnormal thickness of the walls makes the heart chamber stiff, which makes it harder for blood to flow in and out of the heart.

What are the signs and symptoms of the condition? 
The symptoms of hypertrophic cardiomyopathy can be absent, mild, or severe. Sometimes, sudden death occurs in a person with no history of symptoms. More commonly, the following symptoms occur, usually during or shortly after exercise: What are the causes and risks of the condition? 
The cause is of hypertrophic cardiomyopathy is unknown, but most cases are thought to be inherited. Someone who has a close relative with this condition has a much higher risk than others do.

What can be done to prevent the condition? 
There are no known ways to prevent hypertrophic cardiomyopathy.

How is the condition diagnosed? 
After a complete history and physical, the doctor may order tests to help confirm the diagnosis of hypertrophic cardiomyopathy. These tests may include:
  • an electrocardiogram, or ECG
  • a chest X-ray
  • an echocardiogram, an imaging test that uses ultrasound waves to see the beating heart. This test confirms the diagnosis by showing the abnormally thick walls of the heart.
What are the long-term effects of the condition? 
The long-term effects of hypertrophic cardiomyopathy are hard to predict. There is an increased risk of abnormal heartbeats, called arrhythmias, and heart infections, called endocarditis.

Hypertrophic cardiomyopathy also causes an increased risk of sudden death. This risk is not related to how severe the person's symptoms are. It is not known why sudden death occurs, but in most cases it is thought to be due to arrhythmias.

What are the risks to others? 
Hypertrophic cardiomyopathy is not contagious, but it may be inherited by an affected person's children. Genetic counselling may be helpful to couples with a family history of this condition.

What are the treatments for the condition? 
The goals of therapy are to reduce symptoms of hypertrophic cardiomyopathy and prevent death. Because sudden death has been linked to exercise, strenuous exercise should be avoided, whether or not the person has symptoms.

Heart medications are often used to reduce symptoms such as chest pain, palpitations, and fainting. Commonly used medications include atenolol, amiodarone, and diltiazem.

A type of pacemaker device called a defibrillator may also be used for dangerous abnormal heartbeats. Minor surgery is needed to put a defibrillator in place.

For someone with severe symptoms that cannot be controlled by medication, open heart surgery may be advised. The surgery involves removing part of one of the thickened walls of the heart.

What are the side effects of the treatments? 
All medications have possible side effects. For example, atenolol may cause sleepiness and erectile dysfunction. Diltiazem may cause stomach upset or swelling in the legs. Surgery carries a risk of infection, bleeding, and allergic reaction to anaesthesia.

What happens after treatment for the condition? 
The exact course of hypertrophic cardiomyopathy is hard to predict. Treatment is usually needed for long periods of time, sometimes for life.

How is the condition monitored? 
Any new or worsening symptoms should be reported to the doctor. Regular visits to the doctor allow ongoing monitoring for arrhythmias or worsening of the hypertrophic cardiomyopathy. Repeat electrocardiograms, or ECGs, and echocardiograms are often used to help with monitoring.

Author: Eric Berlin, MD
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 11/11/2004
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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