Friedrich B, Gawlitza M, Schob S, Hobohm C, Raviolo M, Hoffmann KT, and Lobsien D, Distance to Thrombus in Acute Middle Cerebral Artery Occlusion: A Predictor of Outcome After Intravenous Thrombolysis for Acute Ischemic Stroke. Stroke. 2015
It is well known to strokologists that patients with acute ischemic stroke from proximal occlusions tend to fare poorly as compared to those with distal occlusions. Several prospective and retrospective observational studies have confirmed this relationship. What has been lacking, however, is precision in the definition of “proximal occlusion,” as seen with the heterogeneity of definitions across trials and observational studies.
This interesting CTA-based imaging study sought to rigidly stratify occlusion location by distance from a single anatomical landmark: the middle of the “carotid T.” In a standardized fashion, the investigators looked back at CTA studies from 136 patients who received IV tPA and measured from the midpoint of the distal ICA to the proximal end of a clot and compared that distance to 7-day NIHSS and 90-day mRS. Overall, the main finding was the distance from the carotid T to the clot was an independent predictor of outcome, even when controlling for clot length. There was an exponential decline in likelihood of good outcome (mRS < or = 2) with distance to thrombus of <16mm. Short distance to thrombus also predicted long thrombus length as compared to more distal occlusions.
In addition to assisting in the definition of proximal occlusions with discrete measurements and a practical anatomical landmark for standardization, this investigation also suggests that perhaps we should pay more attention to clot location and length in our treatment trials and natural history studies, as evidence mounts that these data are quite relevant.