IMS III results show need for vascular imaging in future trials

Vascular imaging should be mandated in future endovascular trials to identify proximal occlusions, according to a study published online June 5 by Radiology.

During the Interventional Management of Stroke (IMS) III trial, the combination of intravenous tissue-plasminogen activator (tPA) with endovascular therapies was tested to try to improve revesacularization and clinical outcomes compared with intravenous tPA alone in patients with moderate to severe acute ischemic stroke. While the overall results were neutral, the subgroup of subjects whose baseline CT angiography or MRI was performed could offer insight into which subgroups of patients with moderate or severe acute ischemic stroke could benefit from endovascular therapy versus intravenous tPA alone.

Lead author Andrew M. Demchuk, MD, of the University of Calgary, and colleagues analyzed the baseline CT angiography and MR angiography information with the IMS III trial as a predictor of the imaging end point of 24-hour recanalization and 90-day modified Rankin Scale (mRS) score for the two treatment groups.

Of the study’s 656 participants, 306 underwent baseline CT angiography or MR angiography. Within that group, 282 had arterial occlusions. At baseline CT angiography, proximal occlusions showed no difference in primary outcomes, with 41.3 percent endovascular and 38 percent intravenous tPA. The 24-hour recanalization rate, however, was higher for endovascular treatment compared with intravenous tPA, at 84.3 percent versus 56 percent, respectively.

Exploratory subgroup analysis for any occlusion at baseline CT angiography didn’t show significant differences between endovascular and intravenous tPA arms for primary outcome, though ordinal shift analysis of full mRS distribution revealed a trend toward a more favorable outcome. Cartoid T- or L-type and tandem ICA and M1 occlusions exhibited greater recanalization and a trend toward better outcome with endovascular treatment.

“The large differential recanalization and clinical treatment effects with endovascular treatment in tandem ICA and M1 occlusions or terminal ICA occlusions is the most important finding and implies that in future clinical trials, investigators should pay particular attention to this subgroup and perhaps even stratify enrollment on the basis of the presence of a carotid T- or L-type or tandem ICA and M1 occlusion,” wrote Demchuk and colleagues.

The authors suggest that future endovascular and thrombolytic trial design include baseline vascular imaging and focus on enrollment of patients with evidence of intracranial occlusion, especially involving the internal carotid artery.