Red Cell Distribution Width may be Related to the Degree of Coronary Collateral Circulation

Abstract

We read the article ‘‘Relation of Coronary Collateral Circulation With Red Cell Distribution Width in Patients With Non-ST Elevation Myocardial Infarction’’ by Tanboga et al with interest. They aimed to investigate the relationship between red cell distribution width (RDW) value and coronary collateral circulation (CCC) in patients with non-ST elevation myocardial infarction (NSTEMI). They concluded that high RDW, high creatine kinase-MB, and absence of preinfarction angina were found to be independent predictors for impaired CCC. We believe that these findings will enlighten further studies about the relationships of coronary collateral (CC) development. Thanks to the authors for their contribution. The CCC is an adaptive response to myocardial ischemia. Well-developed collaterals are associated with reduced mortality in patients with stable coronary artery disease and reduced infarct size in patients with acute myocardial infarction. There are interconnecting vessels between the main arteries, which can prevent ischemia despite coronary artery occlusion in many patients. These interconnections of vessels, which can be visualized and graded by angiography, represent the CCC, an alternative route for the myocardial perfusion. In this study, CCs were scored by visual analyses and were evaluated according to the Rentrop grading system; patients with Rentrop grades 0 and 1 were classified as group 1 (in whom CC development was coded as inadequate), and patients with Rentrop grade 2 and 3 were classified as group 2 (adequate CC development). Then, they compared between these 2 groups. But, in some studies like Refiker et al the patients were classified into impaired CC development (group 1, Rentrop grades 0-1-2) and adequate CC development (group 2, Rentrop grades 3) groups. Duran et al accepted Rentrop grade 0 as absence of CC vessels, and they accepted Rentrop grade 1 as presence of CC vessels. So, what are the criteria for the definition of adequate or inadequate CC development? A subgroup analysis of Rentrop grading system according to each of the 4 groups might affect the results of the study. It would be better if the authors added subgroup analysis according to Rentrop grading system, respectively. The RDW has been recently proposed as an independent predictor of all-cause long-term mortality in patients with NSTEMI 2 and in another study. Sometimes conditions like the differential diagnosis of anemia might affect RDW parameter, and so this parameter might be changed in such an underlying condition. The anemic disease situation may mask the chronic ongoing inflammation. After that, not only RDW but also neutrophil–lymphocyte ratio, gamma-glutamyltransferase, and uric acid are easy methods to assess the CCC in the patients. These might be useful in clinical practice. The RDW itself alone without other inflammatory markers may not give information to clinicians about the inflammatory condition and prognostic indication of the patient. So, we think that it should be evaluated together with other serum inflammatory markers. Finally, it would be better if the authors define how much time they spent in measuring RDW levels, because delayed blood sampling can cause abnormal results in RDW measurements. We think that further studies should be made to enlighten the role of RDW as a prognostic indicator in patients with NSTEMI.