[Show abstract][Hide abstract] ABSTRACT: Collaterals, which develop in response to ischemic stimuli derived from coronary artery disease (CAD), contribute to reduction of infarct size, left ventricular dysfunction, and mortality. However, there is considerable variation among patients with coronary heart disease regarding the extent of coronary collateral development (CCD). In this study, we aimed to investigate the association of the degree of platelet activation via mean platelet volume (MPV) with coronary collateral circulation. Therefore, 210 patients who underwent coronary angiography and had coronary stenosis ≥50 % in at least one coronary artery were included in the study. Clinical information and analyses of blood samples were obtained from a review of the patients' chart. Blood samples for MPV were analyzed by K3 EDTA and collateral vessels were graded according to the Rentrop classification. In the study group, 150 of the 210 patients were found to have inadequate CCD. Although there was no difference between the two groups with regard to platelet count, MPV levels were significantly higher in the patients who had inadequate CCD (11.3 ± 1.0 fl vs. 9.5 ± 1.5 fl, p < 0.001). Furthermore, the Gensini score was significantly lower in patients who had inadequate CCD (45 ± 46 vs. 91 ± 35, p < 0.001). MPV, Gensini score, age, female gender, total cholesterol, red cell distribution width, triglyceride, and fasting glucose levels were found to have univariate association with poor CCD. In multivariate logistic regression model, MPV (OR = 2.45, p < 0.001) and Gensini score (OR = 0.98, p < 0.001) were found to be the independent predictors of impaired CCD. In receiver operator characteristic curve analysis, optimal cut-off value of MPV to predict inadequate CCD was found as >9.6 fl, with 96% sensitivity and 84.7% positive predictive value. In conclusion, we can say that MPV is an important, simple, effortless, and cost effective tool and can be useful in predicting the CCD in patients with significant CAD.