Why Are There Two Murmurs in HOCM?

Medically Reviewed on 2/9/2023
Two Murmurs in HOCM
The myocardial muscle cells are thickened in HOCM, especially in the ventricles.

There are two murmurs in hypertrophic obstructive cardiomyopathy.

  • The first murmur is due to the systolic anterior motion of the mitral valve, leading to mitral valve regurgitation.
  • The second murmur is due to the turbulent flow tract and is present as a mid-systolic, crescendo-decrescendo murmur that is often considered the loudest murmur at the left lower border of the sternum, which mimics the murmur of aortic stenosis.

Causes of HOCM

The following are the causes of hypertrophic obstructive cardiomyopathy:

What is HOCM?

Hypertrophic obstructive cardiomyopathy (HOCM) is an autosomal dominant disorder in most patients and accounts for about 60 percent of HOCM cases that are primarily due to mutations. Different genes that are involved in the mutations may result in HOCM. The most common gene is the cardiac myosin binding protein C which is followed by the mutations in the cardiac beta myosin heavy chain.

HOCM may lead to clinical heart failure, life-threatening arrhythmias, mitral valve regurgitations, and sudden cardiac deaths.

In HOCM, the myocardial muscle cells are thickened, especially in the ventricles (lower chambers of the heart), and ventricular stiffness, mitral valve changes, and cellular changes are observed.

Thickening of the myocardial muscles

Thickening of the myocardial muscles mostly occurs in the septum that divides the right and left ventricles of the heart. This thickness in the septum may block or reduce the blood flow from the left ventricle to the aorta. The ventricles need to pump harder to overcome the blockage.

Muscle thickening can also be seen in other parts of the heart, such as the bottom of the heart, the right ventricle, or the entire left ventricle. This is called hypertrophic nonobstructive cardiomyopathy.

Stiffness of the left ventricle

Stiffness of the left ventricle is caused by cellular changes that occur in the heart muscles as they thicken. When the left ventricle relaxes normally, blood fills the left ventricle. The stiffness results in excess pressure inside the heart that may result in symptoms such as:

Mitral valve changes

When the ventricle outflow tract becomes narrow, the mitral valve performs abnormally. This abnormal mitral valve function blocks the flow, resulting in increased pressure in the left ventricle. When this occurs, the mitral valve begins to leak, causing blood to return to the left atrium.


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What are the signs and symptoms of HOCM?

The following are the signs and symptoms of hypertrophic obstructive cardiomyopathy (HOCM):

The following conditions are associated with HOCM:

How is HOCM diagnosed?

Ways to diagnose hypertrophic obstructive cardiomyopathy (HOCM) include:

  • Family history
  • Medical examination and physical examination (the healthcare provider will listen to the heart and lungs and especially check for murmurs)
  • ECG (it is the most effective test for diagnosing HOCM because it shows the thickened muscles of the heart)

Other tests include the following:

How to manage HOCM

The following are the ways to prevent hypertrophic obstructive cardiomyopathy:

Medically Reviewed on 2/9/2023
Image Source: iStock image