Nonsurgical septal reduction therapy for hypertrophic obstructive cardiomyopathy: short-term results in 50 consecutive procedures.

Background: Nonsurgical septal reduction therapy (NSRT) has been shown to improve left ventricular outflow tract (LVOT) gradients, decrease septal thickness, and improve symptoms in patients with hypertrophic obstructive cardiomyopathy (HOCM). The major complication of this procedure has been the development of complete heart block (CHB) requiring permanent pacemaker implantation, which has been reported in up to 33% of patients in early studies. Since this procedure was first reported, there have been refinements in the technique such as the use of echocardiographic contrast material to localize the site of infarction, slower injection of alcohol, as well as improvement in balloon technology.

Hypothesis: We sought to determine the results of NSRT using echocardiographic contrast localization, slow injection of alcohol, and short balloon length. We theorized that the incidence CHB would be lower than earlier reported results using these refined techniques.

Methods: We performed 50 NSRT procedures on 46 patients using echocardiographic contrast localization, slow alcohol injection, and currently available balloons. Patients had an echocardiogram before, immediately after NSRT, and at 3 months, and a treadmill test before and at 3 months after NSRT. In the hospital, patients were observed for the development of CHB or other complications, and infarct size was determined by serial creatine kinase (CK) measurements.

Results: There was a decrease in the LVOT gradient from 84.2 (+/- 30.8) mmHg at baseline, to 18.5 (+/- 14.8) mmHg immediately after NSRT (p < 0.001). At 3 months, the gradient was not statistically different at 22.7 (+/- 22.2) mmHg 0.27). The septal thickness decreased from 2.21 (+/- 0.66) cm at baseline, to 1.67 (+/- 0.51) cm at 3 months (p < 0.001). New York Heart Association symptom class improved from 3.2 (+/- 0.4) at baseline, to 1.1 (+/- 0.6) at 3 months (p < 0.001). Mean treadmill time in 30 patients was 235 (+/- 142) s at baseline, to 367 (+/- 159) s at 3 months (p < 0.001). Of the 50 procedures, 45 were performed in patients without a previously placed permanent pacemaker or intracardiac cardioverter defibrillator, only 3 (6.7%) of the 45 developed complete heart blocks required permanent pacing. While only three patients in the series had a preexisting left bundle-branch block (LBBB), two of the three patients who required a permanent pacemaker had an LBBB before the prcoedure.

Conclusion: Using contrast echocardiographic localization, slow injection of alcohol, and shorter balloon catheters, there continues to be excellent improvement in LVOT gradients, septal thickness, and symptoms, with a reduced incidence of CHB requiring permanent pacemaker implantation. Left bundle-branch block appears to be a strong predictor for the development of CHB after NSRT.