Ann Thorac Surg 1996;61:564
© 1996 The Society of Thoracic Surgeons
Discussion
Discussion
See also page 558.
DR ALDEN H. HARKEN (Denver, CO):
Doctor Zellner, I think this is a tremendously important paper because you are talking about the preemptive therapy for something that many of us do everyday. I am interested in the discrimination or the distinction or the semantic issue between what is preconditioning and what is the pharmacologic reversal of stunning. I think of the pharmacologic reversal of stunning and ß-adrenergic responsiveness as being inherent in the definition of the stunning process. And preconditioning can be followed up on three different potentially parallel tangents: improvement of mechanical function, electrophysiologic stability, and then cell viability. The cardiologists tend to look at cell viability as decreasing infarct size. You have appropriately focused on mechanical function, which is what we, as cardiac surgeons, are primarily interested in. Can you distinguish or discriminate or just even define for me what the difference is between an improvement in myocardial mechanical function with or without a test of ß-adrenergic responsiveness? What I am really trying to get at is, do you believe that all of those myocytes—and I think your model may be perfect to analyze this—are improved somewhat, or are there some myocytes, like 50% of them, that completely dropped out and died while others are perfectly normal? Is this a global phenomenon with all myocytes or is this a much less democratic physiologic phenomenon?
Again, I think this is very important work.
DR ZELLNER:
Thank you, Dr Harken. Myocytes within the different layers of the heart may behave differently to different stimuli. I can only speak to those myocytes that we studied, which were from the midmyocardium of the left ventricle. Second, the preconditioning phenomenon and the decrease in contractile function that was observed may not be necessary for the beneficial or protective effects of preconditioning. Although our study showed preserved ß-adrenergic responsiveness, there is evidence, I believe, for stunning. Although we do not know from our study whether this is a global effect or not, it would seem that this is such. To develop our preconditioning protocol, we performed viability studies. We found that this was the optimal time period for the preconditioning protocol, and extending this time period resulted in cell death. There are some studies that suggest you do not need stunning for the beneficial effects of preconditioning, and that is an area we are working on right now.
Related Article
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Beneficial Effects of Myocyte Preconditioning on Contractile Processes After Cardioplegic Arrest
- James L. Zellner, Latha Hebbar, Fred A. Crawford, Jr, Rupak Mukherjee, and Francis G. Spinale
Ann. Thorac. Surg. 1996 61: 558-564.
[Abstract]
[Full Text]
