HOCM

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Hypertrophic Cardiomyopathy (HOCM)

HOCM is an autosomal dominant heritable disorder that results in increased LV wall thickening, abnormal LV filling with a dynamic LV outflow tract obstruction and LV diastolic dysfunction due to stiff/hypertrophied LV. This clinically presents with dyspnea, presyncope/syncope, or sudden cardiac death during exercise. Patients with have a systolic murmur best heard at the LLSB that increases with Valsalva (decreases venous return) and decreases with squatting/leg raise (increase venous return). ECG will commonly demonstrate increased QRS voltage, LA enlargement, LVH, pathologic Q waves (dagger-like) in the lateral + inferior leads, and repolarization abnormalities.

Diagnosis is established by TTE which shows dynamic LVOT obstruction. After TTE diagnosis, patient needs evaluation for arrhythmia by 24-hour ECG monitoring or functional hypotension by exercise stress testing which are predictors of sudden cardiac death (SCD).

Patients may require primary prophylaxis of SCD with ICD placement if:

  • First degree relative with SCD

  • LV wall thickness >30 mm

  • Syncope

  • Nonsystained VT

  • Abnormal BP during treadmill exercise

Patients should be advised to avoid high-intensity sports, dehydration (diuretics) and vasodilation (heat, nitrates, phosphodiasterase type 5 inhibitors, dihydropyridine calcium channel blockers). Medical therapy includes beta-blocker (avoid carvedilol, labetalol which have vasodilatory component) and non-dihydropyridine calcium channel blockers (verapamil, diltiazem).

Septal myectomy or septal ablation may be considered in patients with :

  • mod-severe obstruction despite maximal medical therapy + LVOT gradient >50 mmHg

  • recurrent syncope

Surveillance is indicated in patient and first degree relatives. Patients should undergo 24-hour ECG monitoring every 1-2 years. Family members should receive genetic counseling, with ECG and TTE testing every 5 years.

- Natalie Hood, MD