Optimal Electrode Implantation Site for Asynchronous Dipolar Cardiac Pacing

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Abstract
After surgically induced heart block, reproducible measurements of cardiac function were obtained over many hours of asynchronous dipolar ventricular stimulation. An optimal ventricular stimulation rate was identified in each animal. Several stimulation sites were then compared. Left ventricular apical stimulation significantly increased cardiac output over all other sites tested and the increase was maximum during optimal rate stimulation. Using an externally controllable completely implanted pacemaker, left ventricular apical stimulation significantly improved systemic blood pressure over that during right ventricular apical stimulation. During norepinephrine induced hypertension in a small series cardiac output increased 50% while left ventricular apical stimulation remained optimal. The applicability of the results to clinical practice and the effects of random atrio-ventricular synchrony are discussed.