Electromechanical left ventricular behavior after nonsurgical septal reduction in patients with hypertrophic obstructive cardiomyopathy

OBJECTIVES To investigate the electromechanical consequences of nonsurgical septal reduction in a group of patients with hypertrophic obstructive card iomyopathy (HOCM). BACKGROUND Patients with HOCM may benefit symptomatically from nonsurgical septal reduction as an alternative to dual chamber pacing and sensing (DDD) pacing and surgical myectomy. METHODS We studied 20 symptomatic patients with HOCM (12 men), mean age 52 +/- 17 years, before and after septal reduction using echocardiography and electrocardiogram (ECG). RESULTS Septal reduction with a significant rise in cardiac enzymes was suc cessfully achieved in all patients resulting in a 50% reduction in resting left ventricular (LV) outflow tract gradient within 24 h of procedure and a n 80% reduction after six months. Left ventricular outflow tract diameter i ncreased at 24 h with a further increase six months later. QRS duration inc reased by 35 ms at 24 h after procedure associated with right bundle branch block (RBBB) and significant rightward axis rotation in 16 patients. R-wav e amplitude in V1 fell by 7 +/- 4 mm in 15/20 patients, 13 of whom develope d reduction of septal long axis excursion. Left-axis deviation appeared in three patients and septal q-wave was suppressed in 12 long-axis excursion; peak shortening and lengthening rates all fell at the septal site by 20% at 24 h. Only septal excursion returned back to baseline values at six months . Wall motion also became incoordinate so that postejection septal shorteni ng increased by three times control values at 24 h and by four times six mo nths later. CONCLUSIONS Nonsurgical septal reduction is associated with a drop in LV ou tflow tract obstruction and the creation of a localized myocardial infarcti on (MI) increasing LV outflow tract diameter. The technique also results in a consistent alteration of septal activation and secondary incoordination. The latter could play a significant role in gradient reduction and symptom atic improvement in a manner similar to that seen with DDD pacing. (J Am Co ll Cardiol 1999;34:1117-22) (C) 1999 by the American College of Cardiology.