European Journal of Cardio-Thoracic Surgery, Vol 4, 33-39, Copyright © 1990 by European Association for Cardio-thoracic Surgery
Amelioration of reperfusion injury following hypothermic, ischemic cardioplegia in isolated, infarcted rat hearts
S Lindal, S Gunnes, K Ytrehus, BK Straume, L Jorgensen and D Sorlie
Department of Pathology, University of Tromso, Norway.
The left coronary artery was ligated and myocardial infarction developed in
28 rats. Three weeks later, the hearts were excised and mounted in an
apparatus for perfusion of non-working isolated hearts (Langendorff).
Hypothermic (15 degrees C), ischemic cardioplegia was induced for either 2
or 3 1/2 h followed by reperfusion for 45 min. Half of the hearts were
reperfused with an initially gradual rise in temperature and pressure of
the perfusion fluid, whereas the other half was reperfused directly with
the perfusate at 37 degrees C and 100 cm H2O pressure. The hearts were
examined by transmission electron microscopy and randomized for
stereological analysis based on point counting on electron micrographs.
Cardioplegia of 2 h duration was tolerated better than cardioplegia for 3
1/2 h (interstitial edema; P = 0.03, fraction of altered mitochondria; P =
0.001). Particularly in the hearts undergoing the longest cardioplegia,
myocardial injury was less severe following a gentle reperfusion as
compared with those exposed to the clinically common abrupt technique
(fraction of mitochondria in the myocyte; P = 0.03, fraction of altered
mitochondria; P = 0.008). In the interstitium, the luminal area of
capillaries was significantly increased and the endothelial swelling less
pronounced in the groups undergoing the gentle reperfusion technique,
(luminal/endothelial fraction; P = 0.01). The study shows that previously
infarcted hearts are susceptible to ischemic damage even after 2 h of
regular hypothermic, ischemic cardioplegia and that a gentle reperfusion
technique significantly ameliorates reperfusion injury.
