Hypocapnia Induced by Hyperventilation with Indocyanine Green Kinetics Detects the Effect of Staged Carotid Angioplasty to Avoid Hyperperfusion in Patients with Impaired Cerebral Hemodynamic Reserve.

Cerebral hyperperfusion syndrome (CHS) is a serious complication following carotid artery stenting (CAS). Staged angioplasty (AP) could potentially prevent CHS and hyperperfusion phenomenon (HPP) after revascularization. However, methods for measuring the effects of staged AP on cerebral hemodynamic reserve have not been established. Here, we evaluated whether indocyanine green kinetics and near-infrared spectroscopy (ICG-NIRS) with hypocapnia induced by hyperventilation can detect the effects of staged AP on hemodynamic reserve to prevent CHS after CAS. Participants comprised 44 patients at high risk of CHS, whose ipsilateral cerebrovascular reactivity (CVR) was impaired on preoperative single photon emission computed tomography (SPECT). Patients were divided into a staged AP group (n=13) and a regular CAS group (n=31). In the staged AP group, stenting was performed 3 weeks after staged AP. In the regular CAS group, 16 cases (52%) showed HPP, and five (16%) presented with CHS after CAS, while no HPP or CHS occurred in the staged AP group (p=0.001). Changes in blood flow index (BFI) and time to peak (TTP) ratio during hypocapnia calculated from ICG-NIRS indicated a significant linear relationship with preprocedural CVR on SPECT (r=-0.710, 0.632, respectively; p<0.0001 each). BFI and TTP ratios during hypocapnia were significantly improved after staged AP (p<0.001 each). Furthermore, significant linear correlations were observed between BFI and TTP ratio during hypocapnia and postoperative asymmetry index AI (r=0.405, -0.475, respectively; p<0.01 each). Hypocapnia induced by hyperventilation under ICG-NIRS appears useful for detecting the effects of staged AP on hemodynamic reserve in patients at high risk of CHS.