Clinical progress after randomized on/off pacemaker treatment for hypertrophic obstructive cardiomyopathy

Background The therapeutic options for hypertrophic obstructive cardiomyopa thy (HOCM) classically include medical treatment with beta-blockers and cal cium antagonists or myectomy-myotomy as a surgical possibility for refracto ry cases. The observation that pacemaker activation of the heart in HOCM re duces the subaortic gradient is well known but less well investigated. Methods Eighty-three patients (33 female and 50 male) mean age 53 (18-82) y ears, with symptoms refractory to drug treatment and a resting gradient abo ve 30 mmHg, who responded favourably to temporary pacing, were included in this prospective study and had a pacemaker (DDD) implanted. After an initia l double-blind crossover phase of 6 months, patients were reinvestigated at 12 months and followed for a mean of 36 months. Results As observed during a screening investigation, the obstruction was s ignificantly reduced from 72 +/- 35 mmHg to 29 +/- 24 mmHg (P<0.01) when th e pacemaker was on, while no major effect was seen during the sham phase. T he effect was persistent at 1 year with a remaining resting gradient of 28 +/- 24 mmHg. In parallel, we documented an improvement in functional capaci ty, according to the NYHA classification and by quality of Life analysis, a nd a significant improvement in dyspnoea and angina. Exercise on treadmill improved only in patients with reduced initial tolerance (<8 min). During t he mean follow-up of 36 months. 65 patients remained on pacing alone, with eight patients having additional AV-node ablation and five patients finally having surgery. Conclusion This controlled multicentre study shows that pacemaker treatment is an option for HOCM patients; it is inoffensive and does not exclude alt ernative methods, but satisfies 79% of patients beyond 3 years.