Cardioprotective Effects of Intracoronary Morphine in ST‐Segment Elevation Myocardial Infarction Patients Undergoing Primary Percutaneous Coronary Intervention: A Prospective, Randomized Trial

BACKGROUND: A cardioprotective role of morphine acting via opioid receptors has been demonstrated, and previous preclinical studies have reported that morphine could reduce reperfusion injury and myocardial infarct size in a way similar to that of ischemic periconditioning. This study aimed to evaluate the effect of intracoronary morphine on myocardial infarct size in patients with ST‐elevation myocardial infarction undergoing primary percutaneous coronary intervention. METHODS AND RESULTS: This study was designed as a 2‐center, prospective, randomized, open‐label, blinded end point trial. A total of 91 ST‐elevation myocardial infarction patients with thrombolysis in myocardial infarction flow grade of 0 to 1 undergoing primary percutaneous coronary intervention were randomly assigned to a morphine or control group at a 1:1 ratio. The morphine group received 3 mg of morphine sulfate diluted with 3 mL of normal saline, and the control group received 3 mL of normal saline into a coronary artery immediately after restoration of coronary flow. The primary end point was myocardial infarct size assessed by cardiac magnetic resonance imaging The cardiac magnetic resonance images were evaluated for 42 and 38 patients in the morphine and control groups, respectively. Myocardial infarct size was not different between the 2 groups (25.6±11.2% versus 24.6±10.5%, P=0.77), nor was the extent of microvascular obstruction or myocardial salvage index (6.0±6.3% versus 5.1±4.6%, P=0.91; 31.1±15.2% versus 30.3±10.9%, P=0.75, respectively). There was no difference in peak creatine kinase‐MB level, final thrombolysis in myocardial infarction flow, myocardial brush grade, or complete resolution of ST‐segment. CONCLUSIONS: Intracoronary morphine administration could not reduce myocardial infarct size in ST‐elevation myocardial infarction patients undergoing primary percutaneous coronary intervention. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01738100.