Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a heart condition characterized by abnormal thickening of the left ventricular wall in the absence of other causes such as aortic stenosis or hypertension. It affects approximately 1 in 500 individuals and can present with varying patterns of hypertrophy.

The most common and well-recognized features are asymmetrical septal hypertrophy and dynamic left ventricular outflow tract (LVOT) obstruction. About 30% of patients with septal hypertrophy have resting LVOT obstruction, and an additional 30% develop obstruction when provoked by maneuvers such as the Valsalva maneuver.

Impaired diastolic function caused by the thickened myocardium is the major mechanism underlying patients’ symptoms.

HCM is notable for producing heart failure symptoms despite preserved systolic function. Common symptoms include:

• Shortness of breath during exertion
• Fatigue
• Orthopnea (difficulty breathing when lying flat)
• Paroxysmal nocturnal dyspnea

Patients may also experience chest pain similar to angina, often attributed to microvascular ischemia. Arrhythmias can cause palpitations, dizziness, or syncope, and in some cases, sudden cardiac death may occur.

Because symptoms primarily stem from diastolic dysfunction, they often do not differ significantly between patients with and without LVOT obstruction.

HCM is usually inherited in an autosomal dominant pattern. Mutations in at least 11 sarcomeric genes have been implicated. The most common are:

• Beta-myosin heavy chain
• Myosin-binding protein C

Less common mutations include those in troponin T and I, and alpha-tropomyosin.

For family members of patients with HCM, echocardiography, electrocardiography, history-taking, and physical examination are the main tools for screening, rather than genetic testing alone. Screening is generally recommended every 12–18 months, beginning around age 12. If no evidence of HCM is detected by age 21, it is unlikely that a genetic predisposition exists.