7th March 2024

Pathology

HCM is defined as myocardial hypertrophy in the absence of abnormal loading conditions (such as hypertension or valvular disease like aortic stenosis), which would otherwise precipitate a compensatory myocardial thickening. 

HCM is one of the most common of the cardiomyopathies, and left ventricular hypertrophy without abnormal loading conditions is seen in approximately 0.2% of the population – though not all of these will experience signs and symptoms of cardiac disease. 

The symptoms experienced in HCM are typically caused by cellular disarray, leading to disorganised left ventricular architecture and increased myocardial thickening. This can lead to left ventricular diastolic dysfunction due to impaired relaxation, abnormal intramural coronary arteries and dynamic obstruction of the left ventricular outflow tract (LVOT).

HCM is more commonly genetically inherited in an autosomal dominant manner, and almost all components of the sarcomere can be involved. Commonest include the beta myosin heavy chain, myosin binding protein C and troponins I and T. There are many other genetic conditions which can lead to an HCM including Fabry’s disease, Noonan’s syndrome and Friedreich’s Ataxia. Non-genetic causes include AL amyloid and obesity.