DAPT Initiation Timing for STEMI Post-Catheterization
DAPT should be initiated on the same day as the procedure—specifically, aspirin should be given as soon as STEMI is diagnosed (even before catheterization), and a P2Y12 inhibitor loading dose should be administered before or at the time of PCI. 1, 2
Immediate Antiplatelet Therapy Protocol
Aspirin Administration
- Aspirin must be given immediately upon STEMI diagnosis, before the patient even reaches the catheterization laboratory 1
- The loading dose is 162-325 mg orally, or 250-500 mg intravenously if the patient cannot swallow 1
- This represents same-day administration, occurring hours before or during the procedure itself
P2Y12 Inhibitor Loading Dose
- The P2Y12 inhibitor loading dose should be administered before or at the time of PCI 1, 2
- For STEMI patients presenting within 12 hours of symptom onset, the loading dose is typically given at the time of diagnosis, though most receive it at the time of PCI 2
- Loading dose options include:
Critical Timing Considerations
The evidence strongly supports same-day initiation because cardiovascular events occur within hours of initial presentation 2. The 2021 ACC same-day discharge checklist explicitly confirms that the loading dose of P2Y12 inhibitor must be administered on the procedure day, as it requires verification that "loading dose of P2Y12 has been administered" before discharge 3.
Special Timing Nuances
- In NSTEMI patients, there was historical practice of waiting until coronary anatomy was established before giving the P2Y12 inhibitor loading dose 2
- However, for STEMI patients presenting within 12 hours (the typical primary PCI scenario), immediate administration at diagnosis is standard 2
- A small trial of 4,033 NSTEMI patients showed no clear benefit when prasugrel loading was given prior to diagnostic angiography versus at PCI time, but this does not apply to STEMI patients undergoing primary PCI 2
Maintenance Therapy Continuation
After the same-day loading doses, maintenance DAPT continues daily starting the same day:
- Aspirin 75-100 mg daily indefinitely 1
- P2Y12 inhibitor at maintenance dose (prasugrel 10 mg daily, ticagrelor 90 mg twice daily, or clopidogrel 75 mg daily) 1, 4
- DAPT duration is minimum 12 months for drug-eluting stents and 30 days for bare-metal stents 1, 5
Common Pitfall to Avoid
Do not delay P2Y12 inhibitor administration until "the next day"—this represents a critical error that increases risk of acute stent thrombosis and recurrent ischemic events 6, 7. The newer P2Y12 inhibitors (prasugrel and ticagrelor) achieve therapeutic effect within 30 minutes, making same-day administration essential for procedural success 7.
The pre-discharge checklist requirement to confirm P2Y12 loading dose administration and prescriptions for at least 30 days of maintenance therapy further reinforces that all antiplatelet therapy begins on the procedure day 3.