Liebeskind DS, Tomsick TA, Foster LD, Yeatts SD, Carrozzella J, Demchuk AM, et al. Collaterals at Angiography and Outcomes in the InterventionalManagement of Stroke (IMS) III Trial. Stroke. 2014
As many vascular neurologist are aware, the Interventional Management of Stroke (IMS) III Trial showed no benefit of endovascular therapy over IV thrombolysis alone in the treatment of moderate to severe acute ischemic stroke. However, the trial produced a goldmine of data that Liebeskind et al. capitalized on with this study. They Analyzed 276 conventional angiograms for the presence of collateral circulation to establish an association between the degree of collaterals in the endovascular arm before endovascular therapy and the likelihood of recanalization, reperfusion, and good clinical outcome at 90 days after randomization.
Their analysis revealed that collateral grade was strongly related to both recanalization of the occluded arterial segment (p=0.0016), downstream reperfusion (p<0.0001), and good clinical outcome (mRS≤2) at 90 days (p=0.0353). The authors conclude that the role of collaterals is an important consideration in the design of future endovascular trials.
Intuitively this makes sense. One expects that collateralization improves blood perfusion to brain tissue distal to its native arterial supply. Possibly because the collaterals help support a penumbra until recanalization is established. The fact that the IMS III showed no difference in outcome between IV tPA and endovascular therapy following IV tPA, and that collateral blood flow is associated with improved outcomes after an ischemic stroke, makes the argument that less resources should be spent on endovascular therapy, and more on inducing collateralization in high risk patients as part of primary, or even secondary stroke prevention. The authors of this study have access to a cohort of 276 patients with collateralization that follows a bell shaped curve. An attempt to understand why some patients have better collateralization than others is much cheaper, feasible, and generalizable to other diseases, such as coronary artery disease and peripheral artery disease, than repeating yet another expensive endovascular interventional trial.