Cardiac Hemodynamics During Stimulation of the Right Atrium, Right Ventricle, and Left Ventricle in Normal and Abnormal Hearts

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Abstract
Artificial stimulation of the right atrium and the right ventricle at rates between 80 and 180 1 min. was performed in 8 normal subjects, in 7 patients with compensated heart disease, and in 4 patients with heart failure. For any given rate of arterial or ventricular stimulation there were no significant differences for cardiac index, stroke index, mean arterial pressure, ventricular power, and ejection time in normal subjects. In patients with compensated heart disease there was a slight tendency for higher figures for these parameters during artrial pacing, but these differences were not statistically significant. Stimulation of the right and left ventricles at equivalent rates in the range of 80 to 180 1 min. did not show any statistically significant changes for cardiac index, stroke index, mean arterial pressure, stroke work and power, ventricular power, ejection time, tension-time index, and peripheral resistance. Stimulation of the outflow tract, the midportion and the inflow tract of the right ventricle at a fixed rate of 100 1 min. did not show any significant changes in cardiac index, stroke index, mean arterial pressure, and other related parameters. Pacing sites do not significantly influence cardiac dynamics in unanesthetized man. Furthermore, the contribution of artrial systole to the cardiac function is minimal in normal subjects but slightly greater in patients with heart disease.