Dual chamber pacemaker therapy for mid-cavity obstructive hypertrophic cardiomyopathy

Intracavitary LV obstruction is an important determinant of clinical outcom e in hypertrophic cardiomyopathy (HCM). In a minority of patients the obstr uction is at the level of the papillary muscles. Mid-cavity obstructive HCM may be associated with a distal LV aneurysm and a worse prognosis. It is o ften not amenable to standard cardiac surgery for LV out-flow obstruction. The long-term effects (mean follow-up 4.8 +/- 2.9 years) of dual chamber (D DD) pacemaker therapy in 14 patients with mid-cavity obstructive HCM (mean age 34 +/- 16 years, range 15-65 years) were studied. Patients were evaluat ed by cardiac catheterization at baseline and 6 months to 1 year after rece iving DDD pacemakers off all drug therapy. Symptoms were improved in all pa tients and NYHA functional class reduced from 2.8 +/- 0.1 to 1.9 +/- 0.4 (P < 0.0005), Intracavitary LV pressure gradients was reduced significantly ( 43 +/- 36 vs 84 +/- 31 mmHg at baseline, P < 0.0005). There was a significa nt associated reduction in apical LV systolic pressure (152 +/- 37 vs 188 /- 34 mmHg, P < 0.001). In addition, there was a trend towards increased ex ercise tolerance (445 +/- 123 vs 396 +/- 165). Cardiac output and LV fillin g pressures were unchanged. In conclusion, chronic DDD pacing results in si gnificant symptomatic and hemodynamic improvement in this uncommon but impo rtant subset of patients with obstructive HCM in whom the role of cardiac s urgery is less well defined compared with the more typical outflow tract lo cation of LV obstruction.