The Journal of Thoracic and Cardiovascular Surgery, Vol 103, 849-854, Copyright © 1992 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Exercise response assessed by continuous monitoring of ventricular function in patients with coronary bypass operations
M Kawasuji, H Takemura, T Tedoriya, S Sawa, J Taki and T Iwa
Department of Surgery (I), Kanazawa University School of Medicine, Japan.
The response of left ventricular function during exercise and recovery
after exercise was assessed in 35 patients with coronary artery bypass
grafting before and after the operation by means of a continuous
ventricular function monitor, which records serial beat-to-beat
radionuclide data and calculates left ventricular ejection fractions every
20 seconds. The mean ejection fraction decreased with graded bicycle
exercise from 48% +/- 9% to 41% +/- 11% (p less than 0.001) before
operation but increased with exercise from 50% +/- 9% to 55% +/- 11% (p
less than 0.001) after operation. Cardiac response was divided into four
types with respect to the profiles of the ejection fractions during
exercise. Type A continued to increase; type B initially increased but then
decreased in late exercise stages; type C did not change significantly;
type D continued to decrease. Most patients had type C or D responses
before operation but type A after operation. Seven patients with occluded
grafts or ungrafted coronary arteries had type B or D responses. Three
patients with complete revascularization, including an internal thoracic
artery and saphenous vein grafts, had type B responses. Three patients with
extensive infarction and poor left ventricular function showed type C. In
the early recovery period after exercise, most patients had an "overshoot"
elevation of ejection fraction. The mean value increased from 59% +/- 10%
before operation to 64% +/- 11% after operation (p less than 0.01). The
recovery time after exercise was reduced from 2.8 minutes before operation
to 1.8 minutes after operation (p less than 0.001). The continuous
ventricular function monitor elucidated changes in left ventricular
function both during exercise and recovery after exercise, as well as
unmasking abnormalities in left ventricular function after coronary bypass
operation.
