['Larger mean platelets volumes (MPV) are thrombogenic and frequently seen after ST-segment elevation myocardial infarction (STEMI). This study aimed to examine the association of MPV and resolution of ST-segment after thrombolysis in STEMI patients as and its impact on clinical outcome.', 'Patients presenting to the emergency department with the diagnosis of first STEMI and were referred to thrombolysis were screened. Patients with ≥50% ST-segment resolution (STR) 90minutes after thrombolysis were assigned as "Responder" and those with <50% STR were assigned as "Non-Responders". Demographic, clinical comorbidities and risk factor were recorded along with and angiographic data. In-hospital occurrence of major adverse cardiac events (MACE), including acute heart failure (AHF), reinfarction and death were investigated. Additionally, the patients were followed for 6 additional months after their discharge from the hospital.', 'STR≥50% was seen in 60.2% of patients after thrombolysis. Responders had significantly lower MPV (P=0.001) and the critical MPV values were 8.0 femtoliter (fL) and 8.2fL in predicting STR and MACE. Patients with MPV ≥8.2fL had lower probability of STR and higher rates of AHF (P<0.001), and MACE (P=0.001) compared to the patients with lower platelet volume. In multivariate regression, MPV was an independent predictor of STR (P<0.001) as well as MACE (HR=4.8, 95% CI of 1.8-12.4; P=0.001). Triple vessel disease was another independent factor that predicted MACE.'] Is mean platelet volume a predictor of ST resolution following thrombolysis in acute ST elevation myocardial infarction?