Very late effects of dual chamber pacing therapy for obstructive hypertrophic cardiomyopathy.

BACKGROUND: The very long-term effects of dual chamber pacing as a primary treatment for hypertrophic obstructive cardiomyopathy (HOCM) are poorly known and controversial.

AIMS: To examine the intermediate- and long-term clinical and haemodynamic effects of permanent dual chamber pacing in patients presenting with HOCM.

METHODS: Between 1991 and 2007, 51 patients (mean age 59 ± 14 years) presenting with HOCM and New York Heart Association (NYHA) functional class ≥ II despite optimal medical therapy underwent implantation of DDD pacemakers with or without a defibrillator and were followed for 11.5 years (range 0.4-21.8 years).

RESULTS: During follow-up, no patient underwent myectomy or septal alcohol ablation. NYHA functional class and other disease manifestations decreased significantly over 1-2 years of follow-up and remained stable thereafter. The left intraventricular (LV) gradient decreased by a mean of 78% over 1-2 years, reaching 89% at end of follow-up, along with disappearance of systolic anterior motion of the mitral valve. Mean LV ejection fraction decreased from a mean of 64 ± 8% before pacing to 56 ± 9% at end of follow-up (P=0.05), while LV end-diastolic diameter did not change significantly. The 5- and 10-year actuarial survival rates were 90% and 65%, respectively. Among 22 deaths, 10 were due to cardiovascular and 12 to non-cardiovascular causes; two patients underwent cardiac transplantation after 8 and 13 years of DDD pacing, respectively.

CONCLUSIONS: In this sample of patients with HOCM, DDD pacing alleviated symptoms and improved haemodynamic function over the very long term. The merits of this treatment should be revisited in a controlled trial.