Prachi Mehndiratta, MD

Lutsep HL, Barnwell SL, Larsen DT, Lynn MJ, Hong M, Turan TN, et al. Outcome in Patients Previously on Antithrombotic Therapy in the SAMMPRIS Trial: Subgroup Analysis. Stroke. 2015

Here is more on stenting and angioplasty for intracranial artery stenosis in patients already on antithrombotic therapy. The authors conducted a subgroup analysis of the SAMMPRIS population (Stenting vs. Aggressive Medical Therapy for Intracranial Arterial Stenosis) to identify those who were and were not receiving antithrombotic therapy (AT) at the time of the qualifying event that led to randomization into the trial. Patients were included in the antithrombotic therapy group whether they were on single or multiple antiplatelet agents or anticoagulants at the time of the qualifying event and irrespective of the duration of treatment. The primary endpoint consisted of stroke and death within 30 days after enrollment or within 30 days after a revascularization procedure during follow-up, and ischemic stroke in the territory of the qualifying artery beyond 30 days after enrollment.

Baseline characteristics were compared using Fisher’s exact test, independent group t-test or Wilcoxon rank sum test. Times to event curves for the primary endpoint were plotted using the logrank test separately for patients on and off AT at the time of the qualifying event. A total of 284/451 patients (63%) had their intial event on antithrombotic therapy. These patients were mostly taking one or more antiplatelet agents at the time of the event, 22.5% were on dual antiplatelet therapy and 4.2% were on anticoagulant therapy. The AT group differed from the non AT group with regards to baseline risk factors- a greater prevalence of lipid disorders, coronary artery disease, prior stroke, old infarcts on imaging, verterbral or basilar artery stenosis was seen in this group. Of 284 patients taking AT, 140 were randomized to aggressive medical management (AMM) and 144 to angioplasty and stenting (AS). The 2 year rates of primary endpoints were 15.6% in the AMM group and 21.6% in the AS group (p = 0.043). Of those on dual antiplatelet therapy prior to randomization these rates were not significantly different between the two groups – AMM and AS. The 2 year rates of primary endpoint did not differ significantly amongst those not on prior AT. Antithrombotic use at the time of the qualifying event was not related to the primary endpoint in either group.

Does this subgroup analysis change anything for the stroke practitioners? Not really. The study was stopped early and underpowered and hence all the subgroup analyses whether prespecified or not will not be able to tell us anything conclusively. We continue to use aggressive medical management over angioplasty and stenting in our patients with large vessel intracranial artery stenosis since the frequency of primary end points was much lower in this group. Being on antithrombotic therapy prior to randomization in the absence of other risk factor control did not seem to affect the primary end point risk. The bottom line is that we should continue aggressive medical management.