Evidence for Anti-Ischemic Effect of Dual-Chamber Pacing in Patients with the Obstructive Form of Hypertrophic Cardiomyopathy

Dual-chamber pacing reportedly improves the quality of life by reducing the frequency of anginal episodes in selected patients with the obstructive form of hypertrophic cardiomyopathy (HCM), although the underlying mechanism or coronary effect is poorly understood. We report 3 patients with obstructive HCM in whom the effects of atrial vs. dual-chamber tachypacing on systemic hemodynamics and myocardial lactate metabolism were studied. In all patients myocardial lactate production, objective evidence of myocardial ischemia, was demonstrated during atrial pacing, whereas no patient developed myocardial ischemia during dual-chamber pacing. By contrast, the responses of pressure gradient to pacing varied among the patients. These observations demonstrate for the first time that dual-chamber pacing exerted an anti-ischemic effect in obstructive HCM, which may contribute, at least partly, to the beneficial effects of chronic AV pacing on angina status and/or LV function.