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 group of patients with hypertrophic obstructive cardiomyopathy (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 significant rise in cardiac enzymes was successfully achieved in all patients resulting in 50% reduction in resting left ventricular (LV) outflow tract gradient within 24 h of procedure and an 80% reduction after six months. Left ventricular outflow tract diameter increased at 24 h with further increase six months later. QRS duration increased by 35 ms at 24 h after procedure associated with right bundle branch block (RBBB) and significant rightward axis rotation in 16 patients. R-wave amplitude in V1 fell by 7 ± 4 mm in 15/20 patients, 13 of whom developed 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 shortening increased by three times control values at 24 h and by four times six months later. CONCLUSIONS Nonsurgical septal reduction is associated with drop in LV outflow tract obstruction and the creation of localized myocardial infarction (MI) increasing LV outflow tract diameter. The technique also results in consistent alteration of septal activation and secondary incoordination. The latter could play significant role in gradient reduction and symptomatic improvement in manner similar to that seen with DDD pacing.