J Thorac Cardiovasc Surg 1997;114:514-515
© 1997 Mosby, Inc.
Hypothermia during preconditioned ischemia-reperfusion attenuates the myocardial protection of preconditioning
Er-Xiong Lu , MDa,
Gui-Lin Ying , MDa,
Xun Guo , PhDb
Department of Cardiosurgerya
Xiangya Hospital of Hunan Medical University
Department of Pharmacologyb
Hunan Medical University
Changsha, Hunan 410008, People's Republic of China
To the Editor:
Perrault and colleagues
1 are to be congratulated on their elegant and sophisticated study in exploring ischemic preconditioning in cardiac surgery. However, the authors conclude that "preconditioning does not enhance cardioplegic protection and might even be deleterious." This potentially important conclusion was thrown into doubt by a number of significant limitations by Dr. Steven F. Bolling, in his discussion of the article: (1) Is the model actually a model of ischemic preconditioning? (2) Did preconditioning occur? (3) Why were right atrial biopsy specimens used? (4) Why were a few unimportant indices used, instead of the sensitive indices such as protein kinase C isoenzymes, in explaining the occurrence of preconditioning?
We are also part of a group that studies preconditioning both in animal experiments and in clinical trials in cardiac surgery. 2,3 Many factors can interfere with the induction of preconditioning. Recently, we conducted research on the effects of hypothermia during preconditioned ischemia-reperfusion of the myocardial protection of preconditioning in isolated perfused rat hearts (Table I). Male Sprague-Dawley rat hearts were used in the model of modified Langendorff perfusion. Preconditioning was elicited by a single 5-minute period of ischemia and a 10-minute period of reperfusion. After preconditioning, all hearts were arrested by infusion of 4° C St. Thomas' Hospital cardioplegic solution, 5 ml per dose, every 30 minutes for 3 hours and then reperfused by 37° C Krebs-Henseleit buffer solution for 45 minutes. The results indicated that hypothermic preconditioning attenuates the myocardial protection of preconditioning, as shown in Table I. We therefore doubt that the hearts in the experimental group in Perrault's study were really preconditioned. For the purpose of exploring the effectiveness of preconditioning protocol in cardiac operations, ST-segment depression was used as a predictor of preconditioned ischemia in our studies (unpublished data). In addition, many details throughout the operation can disturb the results of preconditioning from an opposite view in cardiac surgery. These factors mainly include unstable anesthesia, cardiopulmonary bypass, body temperature, hypotension, ischemia, and even some inotropic remedies. 4 These factors should be checked seriously because an actual preconditioning may be induced before the preconditioned ischemia. Therefore it may be a prerequisite to answer whether the hearts in the experimental group were really preconditioned or whether the hearts in the control group were actually preconditioned before the evaluation of preconditioning in cardiac surgery.
View this table:
[in this window]
[in a new window]
|
Table I. Effects of hypothermia during preconditioned ischemia-reperfusion on the myocardial protection of preconditioning in isolated perfused rat heart
|
|
12/8/83072
References
-
Perrault LP, Menasché P, Bel A, et al. Ischemic preconditioning in cardiac surgery: a word of caution. J Thorac Cardiovasc Surg 1996;112:1378-86. [Abstract/Free Full Text]
-
Chen X-S, Lu E-X, Yuan M-D, et al. Observation on myocardial protective effects of ischemic preconditioning in intracardiac operation. Bull Human Med Univ 1996;21:320-6 (in Chinese).
-
Marshall ES, Raichlen JS, Tighe DA, Paul JJ, Breuninger KM, Chung EK. ST-segment depression during adenosine infusion as a predictor of myocardial ischemia. Am Heart J 1994;127:305-11. [Medline]
-
Lu E-X, Peng C-F, Li Y-J, Chen S-X. Calcitonin gene-related peptide-induced preconditioning improves preservation with cardioplegia. Ann Thorac Surg 1996;62:1748-51.[Abstract/Free Full Text]
