MYOCARDIAL INFARCT SIZE AND SHOCK/HEART FAILURE: DOES REPERFUSION STRATEGY MATTER IN EARLY PRESENTING STEMIS?

Abstract

A pharmacoinvasive (PI) reperfusion strategy for early presenting STEMI patients showed a trend towards reduced 30-day congestive heart failure (CHF) and shock as compared with those undergoing primary percutaneous coronary intervention (pPCI) (STREAM NEJM 2013). We evaluated whether infarct size was related to this trend. Utilizing at least two sequential peak cardiac biomarkers (CK, CKMB or troponin) measured as first available, at 8-12 hrs and 24 ± 4 hrs, infarct size was divided into three groups: Group 1 (less than 2 upper limit normal, ULN), group 2 (2-5 ULN) and group 3 (greater than 5 ULN). Group 1 included patients with an aborted MI, a pre-specified end-point in STREAM (defined by less than two fold biomarker rise, >50% resolution in ST segment elevation and absence of Q-wave development). The association between infarct size and 30-day shock/CHF was subsequently examined. Data on infarct size and outcomes (CHF/shock) was available on 1833 (96.9%) patients enrolled in STREAM. A higher proportion of pPCI patients had larger infarct sizes i.e. PI vs. pPCI patients were distributed as follows (group 1: 144 vs. 142, group 2: 171 vs. 129, group 3: 599 vs. 648, p=0.02). This distribution occurred despite comparable times to reperfusion for each strategy (PI and pPCI across groups] i.e. group 1=98 min and 186 min; group 2=105 min and 185 min; group 3=100 min and 175 min, respectively). Group 3 patients had more baseline ST segment elevation and Q waves compared to groups 1 and 2 (table). As infarct size increased, a parallel increment in CHF/shock occurred in both treatment arms, except for pPCI patients in group 1. The difference in shock/CHF in the minimally elevated biomarker group 1 (4.2% vs. 11.4%, p=0.02) in favor of PI likely relates to the higher frequency of aborted MI with the PI strategy (73.3% vs. 54.7%, p=0.004). After adjusting for TIMI risk, a trend favoring PI persisted in this sub-group (RR 0.39 95%CI 0.15-1.03, p=0.057): no difference in treatment-related outcomes was evident in groups 2 and 3 (group 2: RR 1.11 95%CI 0.48-2.58, p=0.798, and group 3: RR 0.85 95%CI 0.62-1.15, p=0.291). These data indicate that a PI strategy resulted in a higher frequency of smaller infarcts compared to pPCI strategy. In addition, despite comparable infarct sizes in group 1, PI patients tended to have less 30-day CHF/shock, likely related to a greater incidence of aborted MI’s.