The Annals of Thoracic Surgery, Vol 31, 224-232, Copyright © 1981 by The Society of Thoracic Surgeons
Myocardial protection from permanent injury during aortic cross- clamping: effectiveness of pharmacological cardiac arrest combined with topical cardiac hypothermia
WH Schraut, K Kampman, JL Lamberti, M Freeburger, C Anagnostopoulos and S Glagov
In two groups of animals (6 and 9 dogs), the aorta was cross-clamped 60 and
90 minutes, respectively, during hypothermic cardiopulmonary bypass.
Immediately after cross-clamping, pharmacological cardiac arrest was
induced by injecting 100 ml of a cold cardioplegic solution into the aortic
root. Topical cardiac hypothermia was added. In hearts undergoing 90
minutes of ischemia, a repeat injection of the cardioplegic solution was
done at 45 minutes. In 14 dogs (control group), only topical cardiac
hypothermia was instituted for myocardial protection during 60 minutes of
ischemia. Seven weeks after operation the surviving animals (6 in each
group) were killed. Study of myocardial performance failed to demonstrate
significant differences among the groups. Microscopic examination of
transmural samples taken from anatomically defined sides of both
ventricles, disclosed isolated, punctuate subendocardial scars in only 2
hearts of the control group. All the hearts having 90 minutes of
pharmacological cardiac arrest and topical cardiac hypothermia exhibited
diffuse fibrosis replacing 10 to 20% of the left ventricular myocardium.
Extent and incidence of fibrosis were significantly higher in these hearts
in comparison to those of the other groups. We conclude that
pharmacological cardiac arrest plus topical cardiac hypothermia makes a
safe and efficient method of myocardial protection during aortic
cross-clamping only if the ischemic intervals is limited to 60 minutes. It
cannot prevent permanent myocardial injury if the ischemic arrest is
extended to 90 minutes.
