Background: Mean platelet volume to platelet count (MPV/Plt) ratio has been demonstrated to be a good indicator of long-term mortality in patients with non-ST-segment elevation myocardial infarction (NSTEMI). However, the prognostic value of MPV/Plt in ST-elevation myocardial infarction (STEMI) is not reported.

Aim: To determine whether the MPV/Plt ratio on admission has any predictive value for major adverse cardiac events includ­ing short- and long-term mortality in STEMI.

Methods: In this prospective study, 470 STEMI patients who underwent primary percutaneous coronary intervention (PCI) were enrolled. The patients were divided into three tertiles based on the MPV/Plt ratio on admission. The first tertile (n = 149) was defined as MPV/Plt ratio ≤ 0.029, second tertile (n = 154) 0.029–0.038, and third tertile (n = 159) ≥ 0.038. Primary clinical outcomes consisted of the sum of cardiovascular (CV) mortality, non-fatal re-infarction, and stroke. Secondary clini­cal outcomes were CV mortality, non-fatal re-infarction, target-vessel revascularisation, stroke, and advanced heart failure.

Results: There was no difference between study groups regarding the primary (p > 0.05) and the secondary outcomes (p > 0.05) except for one-year non-fatal re-infarction rate, which was found to be significantly higher in the highest MPV/Plt ratio group (p = 0.045). Age, Killip class > 1, and left ventricular ejection fraction were found to be independent predictors of long-term CV mortality in multivariate analysis (p = 0.009, p = 0.035, and p < 0.001, respectively).

Conclusions: While the MPV/Plt ratio was demonstrated to be associated with one-year non-fatal re-infarction, it was not related to in-hospital, one-month, and one-year CV mortality in patients with STEMI, who underwent primary PCI.