The two mechanical therapies to treat HOCM are surgical myomectomy and catheter based alcohol septal ablation.

The indications for mechanical therapy for HOCM are simply persistent symptoms despite optimal medical therapy (New York Heart Association functional class III and IV) or recurrent syncope despite medical therapy.

Surgical myectomy (a.k.a. septal myectomy) is simply performed when the surgeon removes the hypertrophied part of the interventricular septum relieving the outflow tract obstruction. Complications include a ventricular septal defect (if too much tissue is removed), LV dysfunction (if other myocardial segments are damaged during surgery), or the development of complete heart block (due to injury of the AV node).

Alcohol (Ethanol) septal ablation is a catheter based, minimally invasive intervention during which the septal perforator coronary arteries are identified and alcohol is infused. This causes thrombosis and infarction of the interventricular septum. This causes the infarcted tissue to thin thus relieving the outflow tract obstruction. Complications can be serious and include complete heart block, ventricular arrhythmias, sudden cardiac death, coronary dissection/perforation resulting in pericardial effusion, and LV systolic dysfunction.

The above two procedures have never been compared head-to-head in any clinical trials. Observational data suggest that alcohol septal ablation has more variable results with some patients achieving excellent results while others had no benefit. Both procedures have similar mortality rates. Cardiovascular complications (complete heart block) are lower with surgical myectomy, but non-surgical complications (infection) were higher. Both procedures similarly improve symptoms of heart failure. Alcohol septal ablation was more likely to result in the need for a second procedure.