WHAT IS HYPERTROPHIC CARDIOMYOPATHY?

Learn what hypertrophic cardiomyopathy is, what causes it, and associated symptoms.  This section provides information on the genetics that can lead to hypertrophic cardiomyopathy or HCM.

What is it?

Hypertrophic cardiomyopathy (HCM), also called hypertrophic obstructive cardiomyopathy (HOCM) occurs in one out of  500 people.  Men and women have the condition at the same frequency.  The heart muscle in abnormally thickened or hypertrophied. Hypertrophic cardiomyopathy can cause obstruction of blood as it exits the heart (left ventricle).  This does not occur in all patients.  A pressure gradient is generated between the heart and the aorta (the large blood vessel that the heart pumps blood into as it

In Hypertrophic Obstructive Cardiomyopathy, abnormally enlarged heart muscle obstructs (or blocks) blood flow from the heart and often causes mitral valve abnormalities. Click to enlarge.

travels the body).    When it does, it is referred to as hypertrophic obstructive cardiomyopathy (HOCM).  HOCM is a relatively common finding in young people who experience sudden cardiac arrest.  HOCM is often associated with a mitral valve condition called SAM (which stands for Systolic Anterior Motion of the mitral valve).  Basically, one of the two leaflets of the mitral valve gets caught in the blood as it leaves the ventricle (anteriorly) which adds to the blockage and usually causes a leaky mitral valve (mitral regurgitation). Other names for hypertrophic cardiomyopathy include:  idiopathic hypertrophic subaortic stenosis (IHSS), asymmetric septal hypertrophy, and hypertrophic nonobstructive cardiomyopathy.

What causes it?

Familial hypertrophic cardiomyopathy is caused by mutations in genes that code for sarcomere proteins which form muscle. Click to enlarge.

HCM is usually caused by genetic mutations in the smooth muscle sarcomere (engine of the muscle cells).  It can be inherited (familial, autosomal dominant) or acquired through genetic mutation.  Chronic hypertension, aging, asbestosis, and sarcoid can lead to HCM as well.  It can involve both ventricles.

What symptoms does it produce?

Most importantly, a person can be completely asymptomatic and be completely unaware they have it.  This is why some have advocated for screening although controversial.  The symptoms depend on the pattern of hypertrophy.  If there is an obstructive component (blocking egress of blood from the heart, the most dangerous condition), symptoms are typically more likely to occur.  Symptoms associated with HCM include: shortness of breath, palpitations, light-headedness or fainting (especially with exercise), dizziness, chest pain, and fatigue.