Abstract 2845: Grade 3 Ischemia on the Admission Electrocardiogram Predicts Failure of ST Resolution and of Adequate Flow Restoration Following Primary Angioplasty for Acute Myocardial Infarction
Failure of ST resolution (STR) is a strong negative predictor following primary PCI (PPCI) but currently cannot be predicted on admission. Grade 3 ischemia (G3I) is a measure of the severity of ischemia in pts with STEMI, defined by absence of S waves in the right precordial leads or take-off the ST segment at >50% of the R wave in other leads. ST elevation that does not fulfill these criteria is termed grade 2 ischemia (G2I). We showed that G3I on admission is the strongest predictor of failure of STR after thrombolysis. In pts undergoing PPCI G3I predicts mortality but the mechanism is uncertain and whether it involves failure of STR is unknown. We prospectively studied 100 consecutive pts who had PPCI for a first STEMI. Multiple variables available on admission were analyzed as predictors of STR, measured immediately after PPCI. EKG’s were read in a core lab. Angiograms were analyzed by an angiographer who was blinded to clinical and EKG data. Fifty pts (50%) achieved 70% STR. STR was achieved in 42% and 16% of pts with G2I and G3I, respectively (p<0.01). No other admission parameter, including time to admission and pre infarction angina, predicted STR. STR was observed in 42/71 patients with G2I (59%) vs.8/29 patients with G3I (28%) (p=0.004). After adjusting for age, sex, time to treatment, pre-infarction angina, previous therapy, diabetes, grade of ischemia and Q waves, G3I remained the sole predictor of failure of STR (OR: 0.26, 95% CI=0.1–0.72). Similar findings were obtained when the analysis was repeated with 50% STR as the end point. Angiographic analysis revealed similar initial flow in pts with G2I and G3I. However, post PCI corrected TIMI frame count was 11±6 vs. 21±22 in patients with G2I and G3I, respectively (p<0.01). G3I was the strongest independent predictor of failure to achieve TIMI grade 3 flow (OR: 0.07, 95% CI=0.02–0.33) and TIMI myocardial perfusion grade 3 (OR: 0.09, 95% CI=0.02–0.39).
Conclusion: G3I is the strongest independent predictor on admission of failure to achieve myocardial reperfusion after PPCI, as reflected both by ST resolution and by angiography. This association may underlie the larger infarcts associated with G3I and may allow the identification upon admission of patients who require more aggressive management to improve reperfusion.