Background: Morphine is commonly used for analgesia in the setting of chest discomfort associated with acute coronary syndromes (ACS). However, a retrospective analysis in non-ST elevation acute coronary syndrome (NSTE-ACS) patients suggesting increased mortality with morphine administration and further studies suggesting morphine may delay and inhibit the absorption of the oral anti-platelet agents has placed its utility in ACS under closer scrutiny. In a large single center retrospective study, we analyzed the association between morphine and in-hospital outcomes in ST elevation myocardial infarction (STEMI) and NST-ACS patients undergoing coronary angiogram +/- percutaneous coronary intervention (PCI).
Methods: All STEMI and NSTE-ACS patients undergoing PCI between January 2009 and July 2016 in Massachusetts General Hospital were included in our study. Following institutional board review approval, baseline patient characteristics (demographics, risk factors and medical history) was obtained. In-hospital outcomes included mortality, post-procedure cardiogenic shock, length of hospital stay and infarct size as measured by troponin level.
Results: Overall, 3027 patients were examined. Of those, 1287/3027 (42.52%) had STEMI, of which 359/1287 patients received morphine (27.89%). STEMI patients who received morphine were younger, had a higher prevalence of prior MI, PCI, and angina, were more likely to be on oxygen therapy, and had a longer time to PCI. 1740/3027 (57.48%) of study patients had NST-ACS, of which 424 (24.37%) received morphine. NSTE-ACS patients who received morphine were younger, had a higher prevalence of cerebrovascular disease, peripheral vascular disease, prior PCI, MI, congestive heart failure and valvular surgery. In unadjusted outcomes, STEMI patients who received morphine had a lower in-hospital mortality [4.18% versus 7.54%, odds ratio (OR): 0.53, p=0.03] and smaller infarct size (mean troponin level 0.75 ng/ml versus 1.29 ng/ml, p=0.02). There was no significant difference in post procedure cardiogenic shock or length of hospital stay (p= 0.26 and p=0.29 respectively). After adjusting for basic characteristics no outcomes remained significant in the STEMI cohort. In the NST-ACS cohort, patients who received morphine had a longer hospital stay (mean 6.58 days versus 4.78 days, p<0.0001) and larger infarct size (mean troponin 1.16 ng/ml versus 0.90 ng/ml, p= 0.05). There was no statistical difference in in-hospital mortality or cardiogenic shock (p=0.17 and p=0.80 respectively). After adjusting for basic characteristics, length of hospital stay (p <0.0001) and infarct size (p=0.02) remained significant.
Conclusion: In a large retrospective study, morphine was associated with larger infarct size and a longer hospital admission in NSTE-ACS patients but had no effect on outcomes in STEMI patients.