Surgical aspects of typical subaortic and atypical midventricular hypertrophic obstructive cardiomyopathy (HOCM).

Hypertrophic obstructive cardiomyopathy (HOCM) is a special form of left ventricular outflow tract obstruction. Clinical experience demonstrates 2 different types of HOCM of the left ventricle: the typical subaortic or subvalvular HOCM and the atypical midventricular form of myocardial obstruction. In a series of 108 patients operated upon, 96 had typical and 12 had atypical HOCM. Indications for surgical treatment were increase of clinical symptoms to class III or IV (NYHA) and unresponsiveness to drug therapy (beta-blocking agents, calcium-antagonists). The male: female ratio was 21:1. The mean age in the group with typical HOCM was 38.8 years, in the group with atypical HOCM 46.5 years. Transaortic myectomy (n = 85) was the predominant surgical approach for relief of isolated subaortic and midventricular obstruction. Patients with severe mitral insufficiency and mitral valve replacement were identified as a problematic group. The total hospital mortality was 8.3% (9 of 108 patients), 7.9% (7 of 96 patients) in the typical group, and 16.7% (2 of 12 patients) in the atypical group. Postoperative cardiological follow-up indicates the superior effect of surgery as compared to drug therapy. The late mortality for the medical group was 10% and for the postoperative group 2.5%. These facts support our recommendation for the surgical treatment of HOCM in symptomatic patients in clinical stages III and IV (NYHA).