64F presented with chest pain, consistent with non-ST elevation myocardial infarction with preserved systolic function. At invasive angiogram, right coronary artery was successfully stented with a drug eluting stent. On hospital discharge, she was given Aspirin, Ticagrelor as dual anti-platelet agents. How long should the dual antiplatelet therapy be continued for?
The duration of dual antiplatelet therapy after stenting has been quite a confusing topic, with various changes throughout the years. In most cases, it should be individualised based on coronary anatomy and stenting complexity, context of intervention, as well as bleeding risk.
Here is the summary, with some gross generalisation:
1. Post-PCI for stable chronic angina (i.e. not an MI)
a. Aspirin + Clopidogrel (6m) for most
b. Aspirin + Clopidogrel (12m) for complex stenting (i.e. guided by interventionists)
2. Post-PCI for myocardial infarction
a. Aspirin + Ticagrelor (12m) for most
b. Aspirin + Clopidogrel (12m) for contraindications to Ticagrelor, including high bleeding risk
c. Aspirin + Ticagrelor (12m) followed by Aspirin + Clopidogrel (further 18m) for those without bleeding by 12m
Point 2c is the new change in clinical practice. Evidence of extending dual antiplatelet therapy beyond 12 months came from the DAPT and PEGASUS-TIMI 54 trials.
The DAPT trial compared in almost 10000 patients, 18 months of dual antiplatelet therapy with aspirin alone in stented patients who had received dual antiplatelet therapy for 12 months without major complication. Non-ST elevation acute coronary syndrome accounted for 32% of the patients.
- Stent thrombosis (0.4% vs. 1.4%) and major adverse cardiovascular and cerebrovascular events (a composite of death from any cause, MI, or stroke; 4.3% vs. 5.9%) were lower with continued dual antiplatelet therapy.
- Moderate or severe GUSTO bleeding (2.5% vs. 1.6%) was higher with continued dual antiplatelet therapy (2.5 versus 1.6 percent, p = 0.001).
- In DAPT trial, those with MI benefited more than those without MI.
PEGASUS-TIMI 54 randomly assigned 21,162 patients with prior MI (41% NSTEMI) one to three years earlier to one of two doses (90 or 60 mg) of ticagrelor or placebo, on top of usual aspirin.
- The primary efficacy end point (a composite of cardiovascular death, MI, or stroke) was less in the ticagrelor group (7.8% vs. 9.0%)
- The primary safety end point of TIMI major bleeding was higher in the ticagrelor groups (2.6%/2.3% vs. 1.1%)
The conclusion for the two trials is that extension of dual antiplatelet does reduce cardiovascular events, in the expense of increased bleeding.
Back to the scenario
In the case above, we would normally give Ticagrelor for 12 months, which is the duration of funding post acute coronary syndrome stenting. In selected patients with low bleeding risk, and if they have not had bleeding complications at the 12 month mark, we should strongly consider continuing dual antiplatelet therapy for another 18 months. In New Zealand, it would require changing Ticagrelor to Clopidogrel due to funding issues.