The Relation of Heart Rate to Cardiovascular Dynamics

Abstract

Hemodynamic studies were carried out as heart rates were controlled by atrial pacing on 10 normal patients at rest and during exercise. Each patient served as his own control. In both states tested the cardiac index, left ventricular work, and peripheral resistance were not significantly altered by changes in heart rate. The stroke index and mean systolic ejection rate decreased linearly with heart rate. During exercise the cardiac index increased up to 98% and again remained constant at all paced heart rates tested. At comparable heart rates the tension-time index, left ventricular work, stroke index, and mean systolic ejection rate were higher during exercise than at rest. At comparable heart rates [see figure in the PDF file] peripheral resistance was 38% lower during exercise than at rest. Myocardial oxygen consumption, as inferred from the tension-time index, increased with heart rate in both states.