Department of Cardiac Surgery, Modarres Hospital, Saadat-Abad, Tehran, Iran
To the Editor:
We read with great interest the article by Onorati and colleagues , who tried to analyze transit-time flow and in-hospital results of pedicled vs skeletonized left internal mammary artery (LIMA) in first-time myocardial revascularization. Although we are impressed with the results, we ponder over a few queries that arise in our minds.
Because the study is based on the comparison between pedicled vs skeletonized LIMA, the study needs to be designed such that the myocardial territory nourished by the left anterior descending artery (presumably to which all LIMAs have been anastomosed) can be evaluated.
On the other hand, an average of more than 3 anastomoses were performed in each patient; therefore, it does not seem reasonable to attribute the rise of troponin I to the LIMA, because this may equally be related to any of other bypass grafts. This is also true regarding the 5 patients with perioperative myocardial infarction. In the scope of the higher rate of venous graft occlusion compared with the LIMA, the doubt in the conclusion of this study becomes even more meaningful.
Even in the echocardiographic studies, we would recommend evaluation of the anterior and septal myocardium if the LIMA flow were to be evaluated. Abnormal wall motion in these sections of the heart would be a more acceptable guide to the patency of the LIMA in the two groups of patients.
It is noted that nitric oxide, as the active component of nitrovasodilators such as nitroglycerin, induces vasodilation through the activation of soluble guanylate cyclase in the vascular smooth muscle. Also, a normally functioning endothelium inhibits platelet aggregation and adhesion by negative feedback secondary to platelet-derived adenosine diphosphate-stimulated nitric oxide production. Impairment of nitric oxide production by the traumatized endothelium might be expected to interrupt the protective feedback, and platelet aggregation and adhesion could occur .
It is already and accurately mentioned in the Comment section of the article that "different pathologic studies show a tendency for skeletonized grafts to contain a larger number of lesions in the endothelium, microscopic intimal dissection and detachment, and injuries to the external elastic lamina ... ." . We think, however, this may not affect free flow measurements immediately at the time of surgery. Because of the close relation between endothelial integrity and nitric oxide production, any vessel wall injury will have a strong effect on early and late postoperative LIMA patency, and normal operative pulsation and a free conduit flow does not exclude this unpleasant result.
Because this excellent article is evaluating a very important issue, with its results and conclusions crucial to the strategic planning of the coronary artery bypass grafting surgery by cardiac surgeons, we recommend consideration of all aspects of such study designs. Hopefully, by overcoming all study limitations, a satisfactory guideline may be proposed.
This article has been cited by other articles:
F. Onorati, G. Santarpino, and A. Renzulli
Ann. Thorac. Surg., September 1, 2008; 86(3): 1053 - 1054.
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