Preload reduction with right ventricular pacing: Effects on left ventricular hemodynamics and contractile pattern

Studies were performed in 32 patients to evaluate left ventricular pressure‐volume changes and contractile pattern during right ventricular pacing as compared to normal sinus rhythm. Coronary artery disease was present in 27 patients, while 5 patients (control group) had no evidence of coronary artery or left ventricular disease. Studies were performed during both normal sinus rhythm and right ventricular pacing at comparable heart rates, utilizing angiographic methods to determine heart volumes. Right ventricular pacing in all patients resulted in decreased left ventricular systolic (p< 0.01) and diastolic (p< 0.01) pressures and decreased stroke work (p< 0.001). In the control group, right ventricular pacing caused a decrease in left ventricular end‐diastolic volume (p< 0.01) and stroke volume (p< 0.01), with no change in ejection fraction. The patients with coronary artery disease were divided into four groups, dependent on the left ventricular contractile pattern during normal sinus rhythm and the percentage of change in hemiaxis shortening during right ventricular pacing. In group A (six patients with asynergy) and group B (seven patients with asynergy), there was no significant change in the percentage of hemiaxis shortening during right ventricular pacing when compared to normal sinus rhythm. Ventricular volume studies in these patients (groups A and B) were similar to the control groups and no change in contractile pattern was observed during pacing. In group C, twelve patients had asynergy and a 10% increase in percentage of hemiaxis shortening during right ventricular pacing when compared to normal sinus rhythm. Right ventricular pacing resulted in decreased end‐diastolic pressure (p< 0.01) and end‐diastolic volume (p< 0.001), no change in stroke volume, and an increased ejection fraction (p< 0.01). Contractile patterns improved in all patients in group C during pacing. Group D consisted of two patients with asynergy and a 10% decrease in percentage of hemiaxis shortening during pacing, associated with a decrease in end‐diastolic volume and ejection fraction with deterioration of left ventricular contractile pattern. These results indicate that right ventricular pacing in patients with coronary artery disease decreases preload, which may be accompanied by improved left ventricular contractile pattern (11/27) and in some patients (2/27) deterioration of left ventricular function.