Adverse event rates following primary PCI for STEMI at US and non-US hospitals: three-year analysis from the HORIZONS-Mill trial

Aims: To examine outcomes in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI) at US sites versus sites outside the US (OUS). Methods and results: In the HORIZONS-AMI trial 3,602 STEMI patients in 11 countries were randomised to primary PCI with bivalirudin versus heparin + glycoprotein IIb/IIIa inhibitors. US patients (n=814) had more diabetes, prior infarction, prior bypass surgery, and renal insufficiency. OUS patients (n=2,788) had longer door-to-balloon times, more radial access, fewer bypass surgeries, and were discharged more often on beta-blockers and statins. At three years US patients had higher mortality (9.7% vs. 6.0%, p=0.0003), reinfarction (10.2% vs. 6.4%, p=0.001), major adverse cardiac events (MACE; 28.2% vs. 20.1%, p<0.0001), major bleeding (16.9% vs. 6.4%, p<0.0001) and net adverse clinical events (NACE; 36.6% vs. 23.8%, p<0.0001), which persisted after adjusting for baseline risk. Conclusions: In the HORIZONS-AMI trial, STEMI patients undergoing primary PCI at US versus OUS sites had higher rates of adverse events, which persisted after adjusting for baseline risk. The reasons for these differences are not clear but may be due to unmeasured confounders, different thresholds for event reporting, or valid differences in systems of care and treatments. Registration: ClinicalTrials.gov number NCT00433966.