Abstract 11231: Intravenous Morphine Administration in Patients with ST-Elevation Myocardial Infarction - Impact on Reperfusion Success Assessed by Cardiac Magnetic Resonance Imaging

Abstract

Background Current AHA/ACC guidelines recommend intravenous (IV) morphine administration in patients with STEMI with a class IC indication. As indicated by the level of evidence, due to lacking data this recommendation is based on expert opinions. However, despite the observed cardioprotective effects in animal models, IV morphine has been shown to be independently associated with an increased mortality in patients with non-STEMI. Thus, we thought to analyze the impact of IV morphine on infarct size, microvascular obstruction (MO) and myocardial salvage index (MSI) assessed by cardiac magnetic resonance imaging (CMR) in an unselected cohort of patients with STEMI reperfused by primary PCI.

Methods STEMI patients reperfused by primary PCI (n=276) within 12 hours after symptom onset underwent CMR 3 days after the index event (IQR 2-4). Infarct size and MO were measured 15 minutes after gadolinium injection. T2-weighted and contrast-enhanced CMR was then used to calculate MSI. If IV morphine was administered it was given prior to arrival at the catheterization lab.

Results IV morphine was administered in 44.7 % (n=123) of all patients. The area at risk was similar between patients with and without IV morphine administration (p=0.73). Patients receiving IV morphine displayed a larger infarct size (19.1 [IQR 8.9;29.1]%LV vs. 14.1 [IQR 6.6;24.9]%LV, p=0.02) and a higher extent of MO (0.84 [IQR 0.19;2.01]%LV vs. 0.59 [IQR 0.00;1.40]%LV, p=0.04). In addition, MSI was significantly lower after IV morphine administration (51.1 [IQR 33.0;73.1] vs. 60.5 [IQR 45.6;81.8], p=0.02). In multivariable logistic regression models including variables such as TIMI-flow pre- and post-PCI, time from symptom-onset-to-PCI and the TIMI-risk score, IV morphine was identified as an independent predictor for MSI <median (OR 1.73, 95%CI 1.05-2.87, p=0.03), an infarct size ≥median (OR 1.79, 95%CI 1.07-3.02, p=0.02) and extent of MO ≥median (OR 1.71, 95%CI 1.04-2.80, p=0.03).

Conclusion In patients with STEMI, IV morphine administration prior to PCI is independently associated with an increased infarct size, larger areas of MO and less MSI. The findings of the current analysis warrant further randomized clinical trials assessing the effect of IV morphine use on clinical outcome.