What is HOCM or Hypertrophic Cardiomyopathy?

Thanks to Dr Sesh Narasimhan, a Taree Cardiologist, who has thoughtfully put this simple description of Hypertrophic Cardiomyopathy  (HOCM) together for us.

HOCM: Hypertrophic CardiomyopathyHOCM Hypertrophic Cardiomyopathy

Cardiomyopathy is a medical condition where heart muscle is structurally and functionally abnormal without blockages in the heart blood vessels (coronary artery disease), high blood pressure, heart valve problems or congenital heart diseases.

Hypertrophic cardiomyopathy (HCM) is a disease in which the heart muscle becomes abnormally thick. The thickened heart muscle can make it harder for the heart to pump blood.

HCM often goes undiagnosed because many people with the disease have few, if any, symptoms and can lead normal lives with no significant problems.

However, in a small number of people with HCM, the thickened heart muscle can cause shortness of breath, chest pain or problems in the heart’s electrical system, resulting in life threatening abnormal heart rhythms, which can be fatal.


The symptoms may include one or more of the following:

  • Shortness of breath, especially during exercise
  • Chest pain, especially during exercise
  • Fainting, especially during or just after exercise or exertion
  • Sensation of rapid, fluttering or pounding heartbeats (palpitations)
  • Heart murmur, which a doctor might detect while listening to your heart


If there is a family history of HCM or unexplained sudden death, it is important that you see your GP and get a referral to see a Cardiologist.

It is vital to get a prompt, accurate diagnosis and appropriate care.

Call 000 if you experience any of the following symptoms for more than a few minutes:

  • Chest pain
  • Difficulty breathing
  • Rapid or irregular heartbeat
  • Unexplained collapse

CAUSES of HOCM: Hypertrophic Cardiomyopathy

Abnormal genes (gene mutations) cause the heart muscle to grow abnormally thick in HCM.

Besides abnormally thick heart muscles, they also have an abnormal arrangement of heart muscle cells, which can cause life-threatening, abnormal heart rhythms.

The severity of HCM varies widely. Most people have a form of the disease in which the wall (septum) between the two bottom chambers of the heart (ventricles) becomes enlarged and impedes blood flow out of the heart. This condition is sometimes called obstructive HCM (HOCM).

Sometimes HCM occurs without significant blocking of blood flow. However, the heart’s main pumping chamber (left ventricle) may become stiff, reducing the amount of blood the ventricle can hold and the amount pumped out to the body with each heartbeat. This condition is sometimes called non-obstructive hypertrophic cardiomyopathy.


HCM is usually inherited. There’s a 50% chance that the children of a parent with HCM will inherit the genetic mutation for the disease. Close relatives — parents, children or siblings — of a person with HCM should ask their doctors about screening for the disease.

COMPLICATIONS of HOCM: Hypertrophic Cardiomyopathy

Many people with HCM don’t experience significant health problems. But some people experience complications, including:

  • Abnormal heart rhythms: Thickened heart muscle, as well as the abnormal structure of heart cells, can disrupt the normal functioning of the heart’s electrical system, resulting in fast or irregular heartbeats. They are non-life threatening (AF) or life threatening (VT, VF).
  • Obstructed blood flow. In many people, the thickened heart muscle obstructs the blood flow leaving the heart. Obstructed blood flow can cause shortness of breath with exertion, chest pain, dizziness and fainting spells.
  • Dilated cardiomyopathy. Over time, thickened heart muscle may become weak and ineffective in a very small percentage of people with HCM. The ventricle becomes enlarged (dilated), and its pumping ability becomes less forceful.
  • Mitral valve problems. The thickened heart muscle can leave a smaller space for blood to flow, causing blood to rush through your heart valves more quickly and forcefully. This increased force can prevent one of the valves on the left side (Mitral Valve) from closing properly. As a result, this causes the valve to leak, which may lead to worsening symptoms.
  • Heart failure. The thickened heart muscle can eventually become too stiff to effectively fill with blood. As a result, your heart can’t pump enough blood to meet your body’s needs and one can develop heart failure.
  • Sudden cardiac death. Ventricular tachycardia and ventricular fibrillation can cause sudden cardiac death. People with HCM have an increased risk of sudden cardiac death, although such deaths are rare. Sudden cardiac death is estimated to occur in about 1% of HCM patients each year. HCM can cause heart-related sudden death in people of all ages, but the condition most often causes sudden cardiac death in people under the age of 30.


Your GP will most likely recommend an ECHOCARDIOGRAM (which assesses if your heart muscle is abnormally thick, if your heart valves are moving normally). Based on the results, your GP will refer you to meet a cardiologist. Some cases will require a CARDIAC MRI in addition to the echocardiogram.


Family screening is recommend if you have a first-degree relative — parent, sibling or child — with HCM and sudden cardiac death.

There are two types of screening:

  1. Genetic testing. Genetic tests may not provide a definitive answer because the genetic causes of hypertrophic cardiomyopathy aren’t fully understood. Only 50-60% of families with HCM have a currently detectable mutation. However, if an abnormal gene is detected in your family, then other family members can learn if they are at risk of HCM and more importantly, sudden cardiac death through genetic testing. Consultation with a genetic counsellor is recommended to help you determine whether genetic testing is a good option for you. Dr. Seshasayee (Sesh) Narasimhan The Heart Centre, 39, Commerce Street, Taree, NSW 2430 Telephone: 02-6550-1528, 02-6550-1526
  2. Echocardiography. If genetic testing is not done, or if the results are not helpful, then your doctor may recommend echocardiography on a regular basis if you have a family member with HCM. Adolescents and competitive athletes should be screened once a year. Adults who don’t compete in athletics should be screened every five years.

TREATMENT for HOCM: Hypertrophic Cardiomyopathy

The goal of treatment is to relieve symptoms and prevent sudden cardiac death in people at high risk. Specific treatment varies depending on the severity of your symptoms. The options are:

  • Medications. You may be given medications to relax the heart muscle and to slow the heart rate so that the heart can pump more efficiently. If you have atrial fibrillation, your doctor may prescribe blood thinners (not Aspirin) to prevent you having a stroke.
  • Septal Myemectomy. It is an open-heart procedure in which the cardiac surgeon removes part of the thickened, overgrown heart muscles. Removing part of this overgrown muscle improves blood flow and reduces valve problems.
  • Septal Ablation. It is less invasive that Septal Myemectomy. In this procedure, a small portion of the thickened heart muscle is destroyed by injecting alcohol through a long, thin tube (catheter) into the artery supplying blood to that area. This procedure may improve your symptoms. There is a modest chance that you may need a pacemaker.
  • Implantable Defibrillator. If you have HCM and there is a family history of sudden cardiac death, your cardiologist will recommend that you have an implantable defibrillator. An ICD is a small device that continuously monitors your heartbeat. It’s implanted in your chest like a pacemaker. If a life-threatening arrhythmia occurs, the ICD delivers precisely calibrated electrical shocks to restore a normal heart rhythm.
Dr. Seshasayee (Sesh) Narasimhan
The Heart Centre
39 Commerce Street
Taree, NSW 2430
Telephone:     02-6550-1528

For more information about HOCM or Hypertrophic Cardiomyopathy contact

Cardiomyopathy Australia www.cmaa.org.au


The Heart Foundation www.heartfoundation.org.au