Background and purpose The angiography based Capillary Index Score (CIS) has recently emerged as a potential surrogate marker of cerebral perfusion before intra-arterial thrombolysis. We assessed the prevalence of a favorable CIS (f-CIS) and its relationship with clinical outcome in patients treated by mechanical thrombectomy (MT).

Methods Data from consecutive patients treated by MT from acute middle cerebral artery (MCA) occlusion were retrospectively analyzed. CIS was calculated from a pre-intervention cerebral angiogram. Association with favorable clinical outcome (modified Rankin Scale score ≤2) at 3 months was assessed in multivariate analysis.

Results 146 patients were included in the study. f-CIS was observed in 106/146 (72%) patients with an acceptable inter-rater agreement (κ=0.73, p<0.001). It was associated with a lower pretreatment National Institutes of Health Stroke Scale (NIHSS) score (p=0.014), an isolated M1/M2 occlusion without internal carotid occlusion (p=0.042), and an Alberta Stroke Program Early CT Score (ASPECTS) >4 (p=0.004). In binary regression, a favorable outcome was independently associated with f-CIS (OR (−95% CI, +95% CI)=3.8 (1.3 to 10.9), p=0.013), as well as NIHSS (p=0.007), ASPECTS (p=0.005), isolated M1/M2 occlusion (p=0.013), and age (p=0.032). The positive predictive value of f-CIS for a favorable outcome was 67%.

Conclusions f-CIS was strongly associated with a favorable outcome after MT of acute MCA occlusion. As an easy surrogate marker of cerebral perfusion, it may be a useful—albeit not sufficient—diagnostic test to select patients just before an MT or to manage them after recanalization.