Abstract TP156: A Novel and Logical Strategy for Prevention of Hyperperfusion Syndrome; Intentional Residual Stenosis After Carotid Artery Stenting of an Extremely High-Grade Stenosis

Abstract

Introduction: Hyperperfusion syndrome ( HPS ) probably occurs after carotid artery stenting ( CAS ) of an extremely high-grade carotid artery stenosis (ex-CS). However, it has not been established how to prevent HPS. Hypothesis: Intentional residual stenosis (iRS ) after CAS not followed by balloon dilatation (bD) can prevent HPS in patients with an ex-CS and spontaneously dilates thereafter. Methods: We included in our study patients with an ex-CS who underwent elective CAS not followed by bD for iRS from 2015 to 2018. We defined an ex-CS as a stenosis of more than NASCET 70% which caused delayed filling of contrast material in an internal carotid angiogram and reduced signal intensity (ratio of less than 0.9) of the ipsilateral middle cerebral artery (MCA) compared to the contralateral MCA on magnetic resonance angiograms (MRA), and defined a residual stenosis (rS) as angiographic stenosis of more than NASCET 30% or peak systolic velocity (PSV) of more than 80 cm/s by Doppler ultrasonography. We defined hyperperfusion phenomenon (HPP) as increase of cerebral blood flow in single photon emission computed tomography scans or cerebral metabolic rate of oxygen by measuring blood oxygen content. We evaluated patients’ baseline characteristics, rS just after CAS, incidence of HPS and HPP. Three months after CAS, they underwent conventional angiographic investigation. Results: During the study period, 26 CAS met our inclusive criteria. Their median carotid stenosis was NASCET 81.8%. Signal intensity ratio of MRA was 0.75. Median PSV before and just after CAS was 311.5 and 76.1 cm/s (p<0.0001). Just after CAS, median stent diameter stenosis was 33.3%. Seventeen patients (65.4%) had angiographic rS. Twelve patients (46.2%) had PSV of more than 80 cm/s. Ten patients had both. Comprehensively nineteen (73.1%) patients had significant rS. Among 26 patients with an ex-CS, no one experienced HPS, although comprehensively 15 patients (57.7%) presented asymptomatic HPP. Among 26 patients, 23 patients finished 3-month angiography and their stents significantly spontaneously dilated (p<0.0001). Conclusion: Intentional residual stenosis after CAS of an ex-CS probably prevented hyperperfusion syndrome and spontaneously dilated at 3 months after CAS.