Perfusion Improvement During Endovascular Rescue Therapy Is Associated With Less Time Outside the Autoregulatory Range

BACKGROUND: Endovascular rescue therapy (ERT) is used for refractory vasospasm after aneurysmal subarachnoid hemorrhage, but it is unknown whether angiographic perfusion improvement during ERT is associated with increased time within the individualized autoregulatory range after treatment. We tested whether reductions in angiographic mean transit time (MTT) during ERT were associated with greater postprocedural time within the near-infrared spectroscopy-derived autoregulatory range. METHODS: We performed a retrospective single-center cohort study of patients with aneurysmal subarachnoid hemorrhage who underwent ERT for anterior-circulation vasospasm and had continuous near-infrared spectroscopy monitoring. Cerebral autoregulation was assessed using the cerebral oximetry index to derive optimal mean arterial pressure (MAP Opt ) and the lower and upper limits of autoregulation. Angiographic MTT and time to maximum of the residue function were calculated from digital subtraction angiography. Mixed-effects models tested associations between angiographic perfusion measures, MAP Opt , and change in time within the autoregulatory range after ERT. RESULTS: In 99 observations from 29 patients, the relationship between verapamil dose and ΔMAP Opt depended on pre-ERT MAP Opt (MAP Opt, Before × verapamil interaction: β, −0.0442 [95% CI, −0.0722 to −0.0162]; P =0.0023), meaning the direction of change in MAP Opt differed across baseline autoregulatory states. In 94 baseline angiographic observations, higher pre-ERT MAP Opt was associated with shorter MTT (β, −0.01448 per mm Hg; P =0.011) and shorter time to maximum of the residue function (β, −0.00960 per mm Hg; P =0.0317). In 23 paired observations from 15 patients, each 1-second reduction in MTT during ERT was associated with a 12.9 percentage-point increase in post-ERT time within the autoregulatory range (95% CI, 4.5–21.3; P =0.0085); Δ time to maximum of the residue function was not significantly associated with this outcome. CONCLUSIONS: In this small, single-center cohort, larger intraprocedural reductions in angiographic MTT were associated with increased postprocedural time within the individualized autoregulatory range. These preliminary, hypothesis-generating findings identify angiographic MTT as a candidate physiological biomarker of ERT response that requires prospective validation.