Abstract 84: Thirty-day Mortality of Patients with ST-Elevation Myocardial Infarction (STEMI) According to Hospital Reperfusion Strategy: The Importance of Examining Outcomes of Both Treated and Not Treated Patients

Abstract

BACKGROUND: In Quebec (Canada), patients with STEMI present to 1 of 4 types of hospitals: 1) primary percutaneous coronary intervention (PPCI) centers; 2) non-PPCI centers that systematically transfer patients for PPCI; 3) ‘mixed centers’ that transfer some patients for PPCI and treat others with fibrinolysis; and 4) centers that exclusively treat with fibrinolysis. In all centers, substantial proportions of STEMI patients do not receive any reperfusion therapy for a variety of reasons. Overall STEMI outcomes may vary by type of reperfusion strategy and who is selected to receive it. METHODS: All acute care centers that annually treated ≥ 30 acute myocardial infarctions participated in 2 field evaluations (n=80 in 2006-7; n=81 in 2008-9). All patients had a final diagnosis of myocardial infarction, characteristic symptoms and STEMI confirmed by centralized ECG interpretation. Clinical factors and comorbidities were compared across type of center for all patients, and by reperfusion therapy status. Odds ratios (OR) of 30-day mortality were estimated separately for treated, untreated and all STEMI patients. RESULTS: Of the 3731 STEMI patients, 29.7% presented to PPCI-capable centers, 33.0% to exclusive PPCI transfer centers, 26.7% to mixed centers (66% transferred for PPCI, 34% received fibrinolysis) and 10.6% to exclusive fibrinolysis centers. The proportion of untreated patients increased with decreasing PPCI access: 16.7% in PPCI centers, 21.4% in transfer PPCI centers, 24.9% in mixed centers and 29.8 % in fibrinolysis centers. Mixed center patients transferred for PPCI had the longest treatment delays (only 17% within guidelines). For treated patients, there were no significant differences in adjusted OR across type of center (see Table). However, for untreated patients, risk of death was significantly higher in transfer PPCI and mixed centers compared to PPCI centers. Risk was significantly higher in mixed centers for all STEMI patients combined. CONCLUSION: These findings suggest that in centers that transfer for PPCI, treatment selection bias may mask important disparities in STEMI outcomes, especially in centers with long transfer delays. When evaluating hospital outcomes for STEMI, it is important to examine not only those who are treated but also patients who do not receive reperfusion therapy.