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Ann Thorac Surg 1996;61:1657
© 1996 The Society of Thoracic Surgeons
DR WILLIAM A. GAY, JR (St. Louis, MO): That was a very interesting study, and I had just one question. Some of your slides suggested that there was an additive effect when you added l-arginine to the reperfusate. This would then suggest that there is a systemic deficit of l-arginine in the preparation. How do you explain the additive effect of l-arginine in the reperfusate?
DR CARRIER: We do not know yet how we can explain that, but effectively in some of the slides, the difference between the two groups that received l-arginine was shown just by the end of the period of reperfusion. I am not sure exactly how to explain both, but in most of the experiments that use segmental ischemia, the investigator used to inject l-arginine during reperfusion to show that there is a difference. I do not have any explanation for that at that moment.
DR ROBERT A. GUYTON (Atlanta, GA): I enjoyed the paper very much, and it was a very nice presentation. I presume that the total volume of cardioplegia infused was almost twice as high with l-arginine. If that is the case, have you looked at any nonspecific vasodilator during the cardioplegia infusion to determine whether a vasodilator that does not lead to nitric oxide production could have the same beneficial effects, because nitric oxide production can be a double-edged sword?
DR CARRIER: No, we have not. The only other group we've used was the l-NAME, and that was supposed to block the nitric oxide synthesis, but we should try to use, for example, just nitroglycerin or other vasodilators.
DR GERALD D. BUCKBERG (Los Angeles, CA): Do you think it was an increase in coronary blood flow during your ischemia to that collateral area, or do you think that the l-arginine allowed the endothelium to produce normal nitric oxide to prevent white cell aggregation to the endothelial wall with the subsequent oxygen radical productivity that may follow that?
DR CARRIER: I think that you have expressed the two theories behind it. The first one is you vasodilate the vessels; the second one is you decrease the interaction between neutrophils and the vessel wall itself. Some recent data in the literature seem to suggest that the second hypothesis is probably the most interesting.
DR RALPH J. DAMIANO (Hershey, PA): I congratulate you. You know you have a good study when you raise more questions than you answer.
You did not show the effect of l-NAME on cardioplegic flow. I am very concerned that differences in the amount of cardioplegia delivered may account for some of the differences you found. Could you enlighten us on the effect that l-NAME had on cardioplegic flow? One thing I noticed on your pH slide is that there was no indication that that difference in pH was significant between the l-arginine and l-NAME group. Was it?
DR CARRIER: The difference was significant. We added the fourth group just again to show whether trying to block the nitric oxide will make a difference. The other way around would be to use d-arginine, which was not available at that time.
I do not have the answer regarding coronary flow. We still have to study it. We just measure the pH in that last group to make sure that we are not in the wrong direction with the l-arginine. The only thing I can tell you is that when we injected the l-NAME during reperfusion we saw an increase in blood pressure of the animals, but I do not know about the blood flow of the coronary arteries; we will know in a couple of weeks or months.
DR DAMIANO: We are all familiar with the fact that often when we find a metabolic deficit after ischemia and reperfusion, it does not correlate at all with a functional abnormality. I was wondering if you happened to measure any indices of left ventricular function in these groups.
DR CARRIER: Yes, we measured in a small group of animals the systolic shortening of the wall itself by microcrystals, and it was preserved in the l-arginine group and decreased by about 40% in the control group. We still need to do left ventricular loops and make sure that the global function is improved, but the segmental function seems to be well protected with l-arginine.
Related Article
Ann. Thorac. Surg. 1996 61: 1651-1657.
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