Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a form of cardiomyopathy characterised by left ventricular hypertrophy in the absence of a provoking disease like hypertension or aortic stenosis. The hypertrophy is often asymmetric.

Hypertrophic obstructive cardiomyopathy (HOCM) is a subtype of HCM characterised by obstruction of the left ventricular outflow tract due to excessive hypertrophy of the ventricular septum.

It’s a common cause of sudden cardiac death, especially in athletes. It may also progress into left ventricular dilation. It’s the second most common CMP, affecting 1/500.

Etiology

HCM is a genetic disorder, most commonly caused by mutations in sarcomeric proteins like myosin. Inheritance is autosomal dominant with varying penetrance.

Pathomechanism

HCM causes diastolic dysfunction and increased filling pressure. During systole, there is a narrowing of the LV outflow tract and increased ejection speed. This increased ejection speed decreases the pressure in this region, causing the anterior leaflet of the mitral valve to be pulled in that direction. This is called systolic anterior motion (SAM) of the anterior cusp of the mitral valve, which can intermittently obstruct the outflow tract, causing a sudden decrease in CO. This phenomenon occurs more frequently during exercise.

HCM predisposes to development of arrhythmias, including fatal ones.

Clinical features

Many are asymptomatic. Possible symptoms include dyspnoea, angina pectoris, and syncope (due to LVOT obstruction).

For some affected people, sudden cardiac death is the first manifestation of HCM.

Diagnosis and evaluation

ECG shows signs of left ventricular hypertrophy and strain. Echocardiography shows left ventricular hypertrophy, a septum which is thicker than the posterior wall, normal LV chamber size. SAM may also be visualised.

MRI is the gold standard for the evaluation. 1st degree relatives should be screened for the condition.

Treatment

There’s no specific treatment. Strenuous physical activity should be avoided to prevent sudden cardiac death. In case of significant LVOT obstruction, medical treatment is indicated, but it’s not certain whether medical treatment is indicated for HCM without significant LVOT obstruction. Medical treatment includes beta blockers, CCBs, and antiarrhythmic drugs.

Prevention of SCD by ICD implantation is generally indicated but depends on the patients calculated risk.

Procedures to reduce the size of the septum may also be used, and include surgical septal myectomy, and the use of alcohol to ablate the septum. Heart transplant is a last-line option.