What duration of dual antiplatelet therapy do you use for secondary prevention of ischemic stroke due to intracranial atherosclerotic disease?

It is a fair question that we don't have a solid evidence-based answer for. I agree that the SAMMPRIS trial was driven by events within the first 30 days, although this was primarily driven by procedure-related events in the stented group.

We do know that intracranial athero (ICAS) risk of stroke recurrence remains as high as 12% in the first year (SAMMPRIS; Sangha et al., PMID 28679857; and Liu et al., PMID 26330567) which generally drives me to be aggressive with dual antiplatelet therapy and on the side of the 90 days treatment.

While there exists lower-quality evidence, a subgroup analysis of CHANCE delved into those participants from the original study who underwent MRA imaging. This analysis distinguished individuals with intracranial ...

This is an area of uncertainty and the NIH-funded CAPTIVA study will test different durations (including beyond 90 days) and different regimens (NCT05047172).

In the meantime, 90 days of DAPT are reasonable but one can't be dogmatic about it.

The duration of DAPT in 3 weeks, in general, comes from POINT analysis where risk-benefit appears to become null after 3 weeks, though much of the ischemic risk and reduction of the risk with DAPT is in the first week (Johnston et al., PMID 31238700). In intracranial atherosclerosis, the highest risk of stroke recurrence is in the first month, but it is hard to say where the true risk-benefit lies.

My clear-cut answer would be to adopt the SAMMPRIS protocol of 90 days.

Caveat: 90 days is acceptable if there is less risk of complication (i.e., hemorrhage). Otherwise, there needs to be a risk/benefit discussion in patients who are deemed high risk (known CAA, uncontrolled hypertension, etc.). Other courses of action could involve shortening the length of DAPT (no studies to suggest length) or foregoing DAPT altogether.

I prefer tailoring the treatment for each patient, based on their stroke risk factors, vasculopathy, compliance with healthcare, frequency of doctor visits, and potential bleeding risks or complications. While 30 to 90 days is acceptable for most patients, some may require extended treatment durations.

The latest guidelines from ASA: 2021 Guideline for the Prevention of Stroke in Patients With Stroke and Transient Ischemic Attack; Kleindorfer et al., PMID 34024117 (figure 6, page e428).

Dual antiplatelets for high-risk patients for 90 days.

Longer is better than shorter, although the hemorrhagic complication rate might be higher in the former.

I usually do 90 days of DAPT for intracranial athero.