Hypertrophic cardiomyopathy (HCM) is a genetic disease in which the heart muscle, or the myocardium, becomes abnormally thick. It is inherited in an autosomal dominant fashion and has variable penetrance. There are defects in the genes encoding for sarcomeric proteins, chiefly myosin heavy chain proteins. The hypertrophy is asymmetrical and occurs in the absence of an inciting stimulus. This thickened heart muscle can make it harder for the heart to pump blood efficiently. There is an abnormal arrangement of heart muscle cells, known as myofibril disarray, which can contribute to arrhythmia in some people/
Although most people with HCM are asymptomatic, symptoms can include dyspnea, syncope, angina, palpitations, dizziness and most devastatingly, sudden cardiac death. Although rare, sudden cardiac death has the highest incidence in adolescent and preadolescent children and is related to physical exertion. Physical findings may include double apical impulse, split second heart sound, systolic ejection crescendo-decrescendo murmur, jugular venous pulse revealing a prominent a wave. Complications include arrhythmias, obstructed blood flow, dilated cardiomyopathy, mitral valve problems, and heart failure.
Echocardiography is diagnostic for HCM. Findings may be summarized as:
- Abnormal systolic anterior leaflet motion of mitral valve
- Left ventricular hypertrophy
- Left atrial enlargment
- Small ventricular chamber size
- Septal hypertrophy with septal to free wall ratio > 1.4:1
- Mitral valve prolapse and mitral regurgitation
- Decreased midaortic flow
- Partial systolic closure of the aortic valve in midsystole
Since HCM presents variably, management depends on the presentation. Medications may include beta blockers, calcium channel blockers and rarely, diltiazem, amiodarone and disopyramide. Surgical treatments include left ventricular myomectomy, mitral valve replacement, permanent pacemaker implantation, catheter septal ablation and placement of an implantable cardioverter defibrillator.
Patient should avoid highly strenuous competitive athletic activity or physical exertion. No special diet is required. However, patients should maintain a healthy weight and avoid alcohol. Patients should avoid ionotropic drugs, nitrates, sympathomimetic amines and digitalis. Diuretics should be used with caution.