Abstract: Objective To investigate the safety and efficacy of prophylactic injection of sodium nitroprusside in primary percutaneous coronary intervention (pPCI) without reflow in elderly patients with ST segment elevation myocardial infarction (STEMI). Methods A total of 185 elderly patients with STEMI were divided into sodium nitroprusside group (n= 92) and control group (n=93) with completely randomized design. All patients were treated with pPCI. Sodium nitroprusside group received sodium nitroprusside 200 μg immediately after opening coronary artery. Control group received equal amount of physiological saline. The incidence of no-reflow, the levels of troponin T (cTnT) and ejection fraction (EF), the incidence of major adverse cardiovascular events (MACE) during hospitalization and 1 year follow-up were compared between two groups, and the risk factors of no-reflow were analyzed. Results In nitroprusside group, the incidence of no flow and cTnT, CRP, and the number of stent were significantly lower and LVEF, EF were significantly higher than those in control group (P＜0.05). There were no significant differences in HbA1c, infarct related artery (IRA), TIMI grade, Gensini score, SYNTAX score and incidence of MACE during hospitalization between two groups (P＞0.05). In nitroprusside group, the incidence of MACE in 1-year follow-up was significantly lower than that in control group (P＜0.05). Logistic regression analysis showed that without injection of nitroprusside, diabetes and the high SYNTAX scores were independent risk factors for no reflow. Conclusion The application of sodium nitroprusside can significantly reduce the incidence of no flow and MACE in 1-year follow up in elderly patients with STEMI treated with pPCI，and which has good safety.

Key words: myocardial infarction, angioplasty, transluminal, percutaneous coronary, nitroprusside, no-reflow phenomenon, ST segment elevation myocardial infarction, primary percutaneous coronary intervention