Affiliation:
1. Cardiovascular Research Institute, University of California San Francisco Medical Center, San Francisco, California 94122 and the Department of Medicine, Charing Cross Hospital Medical School London W.6., England
Abstract
An increase in heart rate produced in 12 conscious dogs by right atrial pacing resulted in a fall of end-diastolic volume, stroke volume, stroke work and end-diastolic pressure. Stroke power and the maximum rate of increase of left ventricular pressure (LV dP/dt max) were affected only slightly. Sudden large changes of rate produced transient changes in LV dP/dt max typical of the positive and negative inotropic effects of activation, but steady-state LV dP/dt max was not affected; these effects persisted after autonomic blockade with propranolol and atropine. Postural changes produced no change in LV dP/dt max even after autonomic blockade. We conclude that in this preparation, the interval-strength relationship has a plateau at the physiologic range of heart rate, i.e., myocardial contractility is unaffected by change in heart rate over the range 90 to 190 beats/min.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
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