Complete heart block: determinants and clinical impact in patients with hypertrophic obstructive cardiomyopathy undergoing nonsurgical septal reduction therapy

OBJECTIVES: The purpose of this paper is to examine the incidence and determinants of permanent complete heart block (CHB) after nonsurgical septal reduction therapy (NSRT), and to evaluate the clinical impact of permanent pacemaker (PPM) placement. BACKGROUND: Nonsurgical septal reduction therapy with ethanol improves the clinical and hemodynamic parameters in patients with symptomatic hypertrophic obstructive cardiomyopathy. Complete heart block is a common complication after NSRT. METHODS: The database of 261 consecutive patients who underwent NSRT at Baylor College of Medicine was reviewed. Clinical variables that were considered as possible determinants for CHB after NSRT were: age, gender, New York Heart Association (NYHA) functional class, left ventricular outflow tract (LVOT) gradient at rest or with provocation, septal thickness, and baseline exercise duration. For electrocardiographic (ECG) variables, the presence of first-degree atrioventricular (AV) block, bifascicular block, left bundle branch block, atrial fibrillation, and left ventricular hypertrophy were analyzed. In addition, the volume of ethanol injected, the method of administration of ethanol (i.e., bolus vs. slow injection [over 30 to 60 s]), number of septal arteries occluded, use of myocardial echocardiography, and infarct size as determined by peak creatine kinase level. RESULTS: Of 261 consecutive patients, 37 had PPM or automatic implantable cardiac defibrillator placed before NSRT. Of the remaining 224 patients, 31 (14%) developed CHB after the procedure. Multivariate logistic regression analysis showed that female gender (odds ratio [OR] 4.3; P = 0.02), bolus injection of ethanol (OR 51; P = 0.004), injecting more than one septal artery (OR 4.6; P = 0.016), the presence of left bundle branch block (OR 39; P = 0.002), and first-degree AV block (OR 14; P = 0.001) on the baseline ECG are independent predictors of CHB after NSRT. Patients requiring PPM placement had a similar improvement in their NYHA functional class, septal thickness reduction, LVOT gradient reduction, and improvement of exercise capacity when compared with patients who did not require pacing. CONCLUSIONS: Multiple demographic, electrocardiographic, and technical factors seem to increase the risk of CHB after NSRT. Patients with CHB after NSRT derive similar clinical and hemodynamic benefit to patients who did not require permanent pacing.