Hypertrophic cardiomyopathy (HCM) is characterized hypertrophy of the ventricles. The pattern of hypertrophy is variable but tends to preferentially affect the interventricular septum. In patients with septal hypertrophy adjacent to the left ventricular outflow tract, it can cause outflow tract obstruction. In these patients, the condition is called hypertrophic obstructive cardiomyopathy (HOCM) and accounts for one-third of cases of HCM. The disease leads to myocyte hypertrophy and disarray, disrupting ventricular contraction, and can cause abnormal mitral valve movement and mitral regurgitation. Read about other types of cardiomyopathy.
Most cases are inherited as an autosomal-dominant trait. However, spontaneous mutations may account for some cases of hypertrophic cardiomyopathy.. 2 most common mutations responsible for about 70% cases are: (1) cardiac myosin binding protein C gene (2) cardiac beta myosin heavy chain gene
- Usually, patients are often asymptomatic but may also present with syncope, lightheadedness, dyspnea, palpitations, angina, or sudden cardiac death.
- A key finding is a harsh systolic ejection crescendo-decrescendo murmur in the lower left sternal edge that ↑ with ↓ preload (eg, Valsalva maneuver, standing) and ↓ with ↑ preload (eg, passive leg raise).
- Symptoms worsen with exercise, diuretics, dehydration, ACEIs/ARBs, digoxin, and hydralazine.
- Examination often reveals a sustained apical impulse, an S4 gallop, paradoxical S2, and an abnormal bifid or bisferiens pulse (sudden quick rise followed by a slower longer rise due to LV outflow tract obstruction).
Diagnosis of Hypertrophic cardiomyopathy
- Best initial test: Echocardiography is diagnostic and shows an asymmetrically hypertrophied interventricular septum and dynamic obstruction of blood flow (due to systolic anterior motion of the mitral valve against hypertrophied septum).
- ECG may be normal or show signs of LVH and nonspecific ST- and T-wave changes. Septal Q waves are common in HOCM (inferior and lateral leads).
- CXR may reveal left atrial enlargement (LAE) 2° to mitral regurgitation.
Treatment of Hypertrophic cardiomyopathy
- Best initial treatment: β-blockers are the best initial therapy for symptomatic relief in both HCM and HOCM; non-dihydropyridine CCBs (negative inotropic effect) and ventricular pacemakers are second-line agents.
- Digoxin and spironolactone are contraindicated. Diuretics may help in HCM but are contraindicated in HOCM.
- Implantable defibrillators should be used in symptomatic HOCM patients.
- Patients should avoid intense athletic competition and training.
- Surgical options for HOCM with persistent symptoms include partial excision or alcohol ablation of the myocardial septum.
- Surgical septal myomectomy is reserved for patients when medical and catheter procedures fails. Patients should avoid intense athletic competition and training. Surgical options for HOCM with persistent symptoms include partial excision or alcohol ablation of the myocardial septum.