BACKGROUNDThe definitive treatment for myocardial ischemia is reperfusion. However, reperfusion injury has the potential to cause additional reversible and irreversible damage to the myocardium. One likely candidate for a cardioprotection is adenosine. The present study aimed at investigating the effect of intravenous adenosine on clinical outcomes in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).

METHODSPatients with STEMI within 12 hours from the onset of symptoms were randomized by 1:1:1 ratio to receive either adenosine 50 µg×kg(-1)×min(-1) (low-dose group, n = 31), or 70 µg×kg(-1)×min(-1) (high-dose group, n = 32), or saline 1 ml/min (control group, n = 27) for three hours. Drugs were given to the patients immediately after the guide wire crossed the culprit lesion. Recurrence of no-reflow, TIMI flow grade (TFG) and TIMI myocardial perfusion grade (TMPG), and collateral circulation were recorded. The postoperative and preoperative ST segment elevation sum of 18-lead electrocardiogram (ECG) and their ratio (STsum-post/STsum-pre) were recorded, as well as the peak time and peak value of CK-MB enzyme. Serial cardiac echo and myocardial perfusion imaging were performed at 24 hours and 6 months post-stenting. The primary endpoint was left ventricular function, and infarct size. The secondary end-point was the occurrence of cardiac and non-cardiac death, non-fatal myocardial infarction, and heart failure.

RESULTSA total of 90 STEMI patients were studied. No-reflow immediately after stent procedure was seen in 11 (35.5%) patients in the control group, significantly different from 6.3% in the low-dose group or 3.7% in the high-dose group (both P = 0.001). STsum-post/STsum-pre in the low-dose and high-dose groups was significantly different from the control group (low-dose group vs. control group, P = 0.003 and high-dose group vs. control group, P = 0.001), without a dose-dependent pattern (P = 0.238). The peak value of CK-MB enzyme was significantly reduced in the high-dose group compared to the control group (P = 0.024). Compared to the left ventricular ejection fraction (LVEF) in control group, LVEF in the low-dose group increased by 5.8% at 24 hours (P = 0.012) and by 10.9% at 6 months (P = 0.007), LVEF in the high-dose group increased by 9.5% at 24 hours (P = 0.001) and by 10.0% at 6 months (P = 0.001), respectively. Significant reduction of infarct size by 24.2% was detected in the high-dose group vs. low-dose or control groups (P = 0.008). There was no significant difference regarding secondary endpoints at 6 months among the treated groups. Cardiac function by NYHA classification in both the low-dose and the high-dose groups was improved significantly (P = 0.013, P = 0.016).

CONCLUSIONIntravenous adenosine administration might significantly reduce the recurrence of no-reflow, with resultant improved left ventricular systolic function. High-dose adenosine was further associated with significant reduction of infarct size.