The effect of exercise and atrial pacing on left ventricular volume and contractility in patients with innervated and denervated hearts

Abstract

The effect of maximum exercise on left ventricular function was assessed in 12 patients with normally innervated hearts (IH) and six patients with denervated hearts (DH) who had undergone cardiac transplantation. Left ventricular function was assessed by computer-assisted analysis of the motion of surgically implanted midwall myocardial tantalum markers, visualized fluoroscopically. Measurements were made at rest, and peak supine exercise in both groups of patients. The effect of atrial pacing to the heart rate achieved with peak exercise was also assessed in the patients with denervated hearts. The mean ejection fraction was increased at peak exercise in both groups of patients, although to a greater extent in patients with DH (14% vs 5%). With atrial pacing the mean ejection fraction decreased from the resting value by 4% in DH. The velocity of circumferential fiber shortening increased with peak exercise by 43% in IH and 38% in DH, but did not increase with atrial pacing in the DH group. Stroke volume index increased with peak exercise by 3% in IH and 14% in DH, but decreased by 6% with atrial pacing. There was no significant difference between end-diastolic volumes at rest, exercise or atrial pacing. Although these data may be important with milder exercise, they suggest that the preload effect was not predominant at peak exercise. By exclusion, adrenergic drive was the most important inotropic factor in the left ventricular response to peak exercise. The comparison between denervated and innervated patients' response to strenuous exercise suggests that comparably good exercise performance can be obtained by the denervated heart in the absence of normal autonomic control. Circulating catecholamines may therefore be contributing a very important inotropic action at peak excercise.