Abstract 1900: Collateral Circulation and Hemodynamics of Severe Intracranial Atherosclerosis: Angiography and Clinical Correlates at Baseline in the SAMMPRIS Trial

Abstract

Background: Severe intracranial atherosclerosis, in excess of 70% luminal stenosis, is an established cause of recurrent stroke. Collateral circulation and the hemodynamic effects of such stenoses, however, may further delineate such risk. We conducted angiographic analyses in the SAMMPRIS trial to correlate the degree of collaterals and hemodynamic effects of such stenoses with baseline clinical and imaging characteristics of enrolled subjects. Methods: Baseline angiography of SAMMPRIS subjects was submitted for blinded review to grade collaterals with the ASITN/SIR scale and antegrade flow across the lesion with TICI. Hemodynamic effect was defined as any flow reduction (a partial TICI score). The association of these angiographic scores (dichotomized as none/partial versus complete collaterals and partial versus complete TICI) and baseline demographic, clinical and imaging variables were evaluated using chi-square tests for percentages and independent group t-tests for means. Results: 424/451 subjects enrolled in SAMMPRIS had baseline angiography available for review, with adequate information to score collaterals in 376 cases. Complete collaterals were noted in 117 (31%). Hemodynamic effects (partial TICI scores) were noted in only 188 (50%) of these lesions, which were all in excess of 70% luminal stenosis. Mean lesion length (n=184, from stenting arm) did not differ between the two categories of either collaterals or hemodynamic impairment. Mean percent stenosis was higher for patients with complete collaterals (none/partial, mean 73.7%; complete, 77.4%; p<0.001) and hemodynamic impairment was more common (p<0.001). More robust collaterals (complete versus none/partial) were associated with patients who at baseline were younger (mean age 58.0 versus 61.5 years; p=0.009), had higher serum HDL (40.0 versus 37.7 mg /dL, p=0.035), participated in moderate exercise (43.1 versus 27.9%, p=0.004) and did not smoke (79.5 versus 69.4%, p=0.042). Previously reported associations with collateral circulation (diabetes, statins, presence of infarction on CT or MRI) were inapparent. These relationships of collaterals with hemodynamic impairment and other baseline variables were established across all anatomical distributions of intracranial stenosis. Conclusions: Severe intracranial atherosclerotic lesions are not always associated with hemodynamic effects. Collateral circulation may also frequently compensate for severe stenosis, with more robust collaterals in younger and healthier individuals.