Long-term effects of dual-chamber pacing with periodic echocardiographic evaluation of optimal atrioventricular delay in patients with hypertrophic cardiomyopathy >50 years of age.

Various treatment modalities have been introduced to reduce the subaortic pressure gradient in patients with obstructive hypertrophic cardiomyopathy, including pacemaker insertion. Complete ventricular capture during pacing is essential and requires optimization of the atrioventricular interval (AVI). In this study, a protocol using echocardiographic examination assessing the changes in the left ventricular outflow tract (LVOT) gradient in different AVIs, pacing rates, and pacing modes was used for optimal pacemaker programming. Twenty-five patients with obstructive hypertrophic cardiomyopathy were implanted with DDD pacemakers and evaluated prospectively. The LVOT gradient was measured during periodic evaluations every 3 to 6 months. Gradient measurements were done with 5 different AVIs and 3 different rate combinations. After each evaluation, the optimal AVI, pacing rate, and mode were set on the basis of the minimal LVOT gradient not associated with systolic arterial cuff pressure reduction. Follow-up ranged from 18 to 126 months. Peak LVOT gradient immediately decreased in 92% of patients. During follow-up, the optimal AVI was prolonged in most patients. Sixty-four percent of patients showed a clear relation between pacemaker modifications and gradient reduction. In 75% of these patients, optimal gradient reduction required repeated AVI and pacing rate programming on the basis of echocardiographic evaluation. Symptoms decreased in 92% of patients, and New York Heart Association class improved significantly (3.1+/-0.7 vs 1.3+/-0.4, p<0.001) during follow-up. The symptomatic reduction was positively correlated with the LVOT gradient reduction. In conclusion, DDD pacing is effective in reducing the LVOT gradient and improving functional capacity in adult patients with hypertrophic cardiomyopathy. Pacemaker programming with the periodic echocardiographic evaluation of the optimal AVI, pacing rate, and mode is imperative for optimal results.