ABSTRACT
BACKGROUND: Right ventricular apex pacing for gradient reduction in hypertrophic obstructive cardiomyopathy (HOCM) with severe left ventricular (LV) obstruction has yielded conflicting results. OBJECTIVE: The purpose of this study was to assess the feasibility and effectiveness of biventricular pacing in HOCM. METHODS: Transvenous biventricular pacing was attempted in 12 severely symptomatic HOCM patients. Optimal intervals were programmed after implant. Echocardiographic LV pressure gradient and synchrony were assessed. LV lead implantation was successful in 9 patients. Optimal pacing mode was biventricular in 6 patients, left ventricular only in 2 patients, and right ventricular only in 1 patient. RESULTS: Functional capacity and quality of life progressively improved. New York Heart Association functional class decreased from 3.2 ± 0.4 at baseline to 1.9 ± 0.3 at 3 months and to 1.4 ± 0.5 at 1 year (P <.05); 6-minute walk test increased from 349 ± 116 m at baseline to 454 ± 144 m at 3 months and to 517 ± 206 m (P <.05); and quality of life increased from 54 ± 16 points at baseline to 28 ± 13 points at 3 months and 27 ± 15 points at 1 year (P <.05). There was also a progressive reduction in LV gradient from 74 ± 23 mmHg at baseline to 50 ± 27 mmHg acutely, 40 ± 26 mmHg at 3 months, and 28 ± 17 mmHg at 1 year (P <.05). Gradient reduction was associated with diminished peak longitudinal displacement of the LV septum and earlier displacement of the lateral wall. A progressive reduction of LV mass was observed, from 356 ± 110 g at baseline to 315 ± 70 g at 3 months (P = .13) and to 284 ± 42 g at 1 year (P <.05). CONCLUSION: Biventricular pacing is feasible and usually the best configuration for gradient reduction in HOCM. Biventricular pacing reduces LV hypertrophy.
