Background: SYNTAX score (SxS) has been demonstrated to predict long-term outcomes in stable patients with coronary artery disease. But its prognostic value for patients with acute coronary syndrome remains unknown.

Aim: To evaluate whether SxS could predict in-hospital outcomes for patients admitted with ST elevation myocardial infarction (STEMI) who undergo primary percutaneous coronary intervention (pPCI).

Methods: The study included 538 patients with STEMI who underwent pPCI between January 2010 and December 2012. The patients were divided into two groups: low SxS (< 22) and high SxS (> 22). The SxS of all patients was calculated from aninitial angiogram and TIMI flow grade of infarct related artery was calculated after pPCI. Left ventricular systolic functions of the patients were evaluated with an echocardiogram in the following week. The rates of reinfarction and mortality during hospitalisation were obtained from the medical records of our hospital.

Results: The high SxS group had more no-reflow (41% and 25.1%, p < 0.001, respectively), lower ejection fraction (38.2 ± 7.5% and 44.6 ± 8.8%, p < 0.001, respectively), and greater rates of re-infarction (9.5% and 7.3%, p = 0.037, respectively) and mortality (0.9% and 0.2%, p = 0.021, respectively) during hospitalisation compared to the low SxS group. On multivariatelogistic regression analysis including clinical variables, SxS was an independent predictor of no-reflow (OR 1.081, 95% CI 1.032–1.133, p = 0.001).

Conclusions: SxS is a useful tool that can predict in-hospital outcomes of patients with STEMI undergoing pPCI.