Hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a type of cardiomyopathy and is the leading cause of sudden death (from arrhythmias) in infants, teenagers and young adults. 

Epidemiology

There is no gender predilection and has a prevalence of around 0.3 - 0.5% in the general population ⁴.

Pathology

Hypertrophic cardiomyopathy is a genetic disorder involving the cardiac sarcomere. It is characterized by left ventricular hypertrophy (wall thickness > 12 - 15 mm) without obvious aetiology.  Associated right ventricular hypertrophy may be seen in 15% of cases.

Morphologically there are several recognised sub types ⁴

• asymmetrical (commonest and most frequently involve the anteroseptal myocardium)
• symmetrical
• apical
• mass like hypertrophic cardiomyopathy / tumefactive hypertrophic cardiomyopathy ⁸

Location

Most common location is the basal septum. Rare apical wall hypertrophy cases reported (more in Asian groups). Concentric left ventricular wall also described.  Myocardial enhancement on viability studies (MR post-gadolinium late sequences) demonstrated a worse outcome.

Can be associated with SAM (systolic anterior motion) of the anterior mitral leaflet, which can increase LVOT obstruction and decreased coronary and systemic outflow.  Mitral regurgitation and left auricle dilation are some other secondary signs.

Radiographic features

Plain film - chest radiograph

Can vary from a normal to enlarged heart.

Cardiac MRI

Often shows concentric but asymmetrical hypertrophy of myocardium. May show a typical spade-like configuration on left ventricular long axis images (similar to the angiographic RAO projection) ⁵.

Treatment

Base of treatment is to control heart rate by avoiding extreme physical effort and by drugs (e.g. Beta-blockers). In cases of family history of sudden death and obstructive sign of LVOT and/or presence of myocardial fibrosis, defibrillator device placement or alcohol arterial embolization are evaluated.