Myocardial salvage and infarct characteristics in patients with ST-elevation myocardial infarction classified by ORBI risk score

Abstract Background The Observatoire Régional Breton sur l'Infarctus (ORBI) [1] risk score was developed to predict in-hospital cardiogenic shock (CS) development in patients with ST elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention. The association between infarct characteristics determined by cardiac magnetic resonance imaging (CMR) and ORBI risk classification have not previously been reported in patients with STEMI. Methods The Third DANish Study of Optimal Acute Treatment of Patients With ST-Segment Elevation Myocardial Infarction (DANAMI 3) trial investigated multiple revascularization strategies in patients with STEMI. CS on admission was an exclusion criterion, thus only low and intermediate scores were included. Stratification into ‘low’ (0-7) and ‘intermediate-high’ (>=8) ORBI risk score was performed (n=1,396), and CMR data from admission and three months follow-up at the largest participating centre were analysed using logistic- and Cox-regression (n=534, 38%). Results A total of 1,149 (82%) were ‘low’ risk, and 247 (18%) ‘intermediate-high’ risk. Patients with ‘intermediate-high’ risk were older (median age 71 (interquartile range (IQR) 61-78) vs. 60 (52-68), p<0.001), and more had an admission systolic blood pressure < 90 mm Hg (4.9% vs. 1.4%, p=0.002), and heart rate > 100 bpm (30% vs. 5%, p<0.001). Left ventricular ejection fraction was lower at discharge (40% (30-50%) vs. 50% (45-55%), p<0.001), and more had an anterior infarction (61% vs. 38%, p<0.001) compared to ‘low’ risk patients. Moreover, median peak troponin was higher (5010 ng/L (2195-9930) vs. 2820 ng/L (1138-5805), p<0.001). Aside from hypertension (52% vs. 39%, p<0.001), there were no differences in factors not covered by the ORBI score. In patients with ‘intermediate-high’ risk, both median acute and final infarct size were larger compared to those with ‘low’ risk (21% (12-28%) vs. 15% (7-24%), p=0.004, and 15% (10-26%) vs. 10% (4-17%), p<0.001). Median final salvage index was lower (0.66 (0.47-0.76) vs. 0.69 (0.55-0.87), p=0.048). ‘Intermediate-high’ risk was associated with higher odds of an above-median acute infarct size (odds ratio (OR) 2.02 (95% confidence interval (CI) 1.13-3.68) p=0.019), final infarct size (OR 3.00 (1.65-5.37), p<0.001), and lower odds of an above-median final salvage index (OR 0.52 (0.29-0.91), p=0.026). One-year mortality was higher in patients with ‘intermediate-high’ (9.7% (95%CI 5.9-13)) compared to "low" risk patients (1.9% (1.1-2.7), p<0.001). In univariate analyses, ‘intermediate-high’ risk was associated with a higher mortality risk (hazard ratio 5.31 (95%CI 2.98-9.48), p<0.001). Conclusions In patients with STEMI, an intermediate-high ORBI risk score of >=8 was associated with larger infarct size and less myocardial salvage, and a 5-time higher mortality risk relative to the overall favorable outcomes in those with a low-risk score.Kaplan-Meier Plot, one-year survival