The Capillary Index Score as a Marker of Viable Cerebral Tissue: Proof of Concept-The Capillary Index Score in the MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) Trial

Background and Purpose - The capillary index score (CIS) is based on the hypothesis that areas lacking capillary blush on pretreatment cerebral digital subtraction angiograms correspond to nonviable cerebral tissue. Methods - Pretreatment digital subtraction angiograms and post-treatment noncontrast enhanced computed tomographic scans from the MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands) trial were evaluated for areas lacking capillary blush and with tissue hypodensity, respectively. Because the superior and middle zones of the CIS correspond to the 7 cerebral cortex regions of the Alberta Stroke Program Early CT (ASPECT) score, capillary blush was scored in these 2 zones (0-2), called sub-CIS, and compared with the ASPECT score in these 7 regions (0-7), called hypodensity score. The presence and extent of hypodensity were compared between sub-CIS zones with contingency tables and nonparametric comparisons between groups, respectively. Results - On the basis of a sample size of 50 subjects, 100% with sub-CIS <2 had the presence of hypodensity (hypodensity score ≥1) versus 57% for sub-CIS=2 (P=0.004). The extent of hypodensity (numeric hypodensity score) was significantly lower for sub-CIS=2 than 0 or 1 (P=0.02). For 42 subjects with revascularization data, the presence and extent of hypodensity were significantly lower for sub-CIS=2 plus good revascularization than for other combinations of sub-CIS and revascularization (P=0.02 and 0.01, respectively). Conclusions - The absence of capillary blush on pretreatment digital subtraction angiogram seems to correspond to nonviable cerebral tissue. Successful revascularization reduces the chance of tissue hypodensity (infarction), when capillary blush is present. Clinical Trial Registration - URL: http://www.trialregister.nl. Unique identifier: NTR number 1804. URL: http://www.isrctn.com. Unique identifier: ISRCTN10888758.