Effects of Atrial Pacing on Left Ventricular Performance in Patients with Heart Disease

Hemodynamic data and systolic time intervals were obtained at resting heart rate and during atrial pacing in 10 patients with heart disease, eight with left ventricular dysfunction, and two with mitral stenosis. The mean increase in heart rate was 44 beats/min. During atrial pacing there was no significant alteration in cardiac output, minute work, left atrial or pulmonary wedge mean pressure, or duration of left ventricular pre-ejection period. When the pressure events which determine the duration of the isovolumic time and the left ventricular pre-ejection period were examined, aortic diastolic pressure rose while left ventricular end-diastolic pressure fell. The rate of pressure rise (dp/dt) determined from high-fidelity left ventricular pressure pulses in three patients increased out of proportion to the increased pressure developed throughout isovolumic contraction. The augmentation in dp/dt from lower end-diastolic pressure indicates improved mechanical performance of the left ventricle, which is not necessarily translated into hemodynamic improvement.