Mechanisms and efficacy of LV pre-excitation for patients with heart failure and supra-normal systolic function.

Ventricular hypertrophy due to genetic mutations of sarcomeric proteins or that associated with long-standing hypertension typically yields a cavity with hyperdynamic ejection, elevated diastolic pressures, and limited filling volumes. The net result is reduced reserve capacity, dyspnea with exertional intolerance, and chest discomfort despite normal appearing coronary vessels. In addition to pharmacologic therapy by agents having negative inotropic effects, recent studies have examined the potential of ventricular pacing using right apical pre-excitation as a treatment for these disorders. This form of pacing can increase end-systolic volume and reduce cavity obliteration in both forms of the disease, yet has no demonstrable acute benefit on diastolic function. Chronic therapy trials have yielded mixed results, with more favorable responses observed in older patients particularly those with hypertensive hypertrophic disease. These data have also highlighted the importance of enhancing systolic reserve rather than diastolic function as a key therapeutic effect from pacing therapy. This review discusses the mechanisms by which pacing with ventricular pre-excitation acutely influences ventricular function, and summarizes results of recent clinical trials, putting the data into perspective regarding the relative role of systolic versus diastolic effects in these patients.