Cardiac Output as a Function of Ventricular Rate in a Patient with Complete Heart Block

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Abstract
Hemodynamic effects of varying heart rate and activity have been studied in a young woman in good health except for complete heart block. As cardiac rate was increased from 50 to 110 beats per minute by means of an external cardiac pacemaker, cardiac output and stroke volume were found to reach maximum values at a rate of 75. Stroke volume increased 43 per cent with exercise when heart rate was fixed at 68 beats per minute. The ability of this patient to increase stroke volume with exercise, in contrast to average normal subjects, may be related to her past experience with chronically increased volume loads on the heart secondary to heart block.