Duration of ischemia and treatment effects of pre- versus in-hospital ticagrelor in patients with ST-segment elevation myocardial infarction

BACKGROUND: Among patients with STEMI in the ATLANTIC study, pre-hospital administration of ticagrelor improved post-PCI ST-segment resolution and 30-day stent thrombosis. We investigated whether this clinical benefit with pre-hospital ticagrelor differs by ischemic duration.METHODS: In a post hoc analysis we compared absence of ST-segment resolution post-PCI and stent thrombosis at 30 days between randomized treatment groups (pre- versus in-hospital ticagrelor) stratified by symptom onset to first medical contact (FMC) duration [≤1 hour (n = 773), >1 to ≤3 hours (n = 772), and >3 hours (n = 311)], examining the interaction between randomized treatment strategy and duration of symptom onset to FMC for each outcome.RESULTS: Patients presenting later after symptom onset were older, more likely to be female, and have higher baseline risk. Patients with symptom onset to FMC >3 hours had the greatest improvement in post-PCI ST-segment elevation resolution with pre- versus in-hospital ticagrelor (absolute risk difference: ≤1 hour, 2.9% vs. >1 to ≤3 hours, 3.6% vs. >3 hours, 12.2%; adjusted p for interaction = 0.13), while patients with shorter duration of ischemia had greater improvement in stent thrombosis at 30 days with pre- versus in-hospital ticagrelor (absolute risk difference: ≤1 hour, 1.3% vs. >1 hour to ≤3 hours, 0.7% vs. >3 hours, 0.4%; adjusted p for interaction = 0.55). Symptom onset to active ticagrelor administration was independently associated with stent thrombosis at 30 days (adjusted OR 1.89 per 100 minute delay, 95%CI 1.20-2.97, P < .01), but not post-PCI ST-segment resolution (P = .41).CONCLUSIONS: The effect of pre-hospital ticagrelor to reduce stent thrombosis was most evident when given early within 3 hours after symptom onset, with delay in ticagrelor administration after symptom onset associated with higher rate of stent thrombosis. These findings re-emphasize the need for early ticagrelor administration in primary PCI treated STEMI patients.