VESS18 - Ipsilateral Middle Cerebral Artery Isolation: A Critical Predicting Factor for Post-operative Stroke after Transcarotid Artery Revascularization

Objectives: Transcarotid Artery Revascularization (TCAR) relies on the intracranial collateral pathways of the Circle of Willis (CoW) to perfuse the ipsilateral hemisphere during flow reversal. An ipsilateral isolated middle cerebral artery (iMCA) has been shown to be associated with an increased risk of post-operative ischemic stroke in asymptomatic patients undergoing TCAR. We hypothesize that iMCA decreases tolerance to flow reversal, increasing the risk of post-operative stroke in the isolated hemisphere following TCAR regardless of symptomatic status.

Methods: Clinical data and outcomes were prospectively collected through our multihospital single-institution Vascular Quality Initiative (VQI) from January 2019 to May 2025. All patients undergoing TCAR were included. Patients with inadequate imaging to appropriately assess the CoW were excluded. Ipsilateral MCA was defined as iMCA if there was an incomplete segment in both the anterior semicircle and the ipsilateral posterior semicircle. Primary outcome was an immediate neurologic event (INE), defined as any transient ischemic attack or stroke diagnosed within 24 hours of intervention.

Results: Analysis included 600 TCAR procedures (566 patients) performed for either severe asymptomatic (>70%) or symptomatic (>50%) carotid artery stenosis. Imaging analysis revealed an ipsilateral iMCA in 68 cases (11.3% of 600 cases, 12.0% of 566 patients). History of prior stroke was more prevalent in the iMCA group (57% vs 43% non-iMCA; p=0.038). Treated lesion lengths and degree of stenosis did not significantly differ between groups (Table I). Flow reversal times did not differ between groups (9.8 mins iMCA vs 10.6 mins non-iMCA; p=0.58) nor did incidence of perioperative hemodynamic lability (31% iMCA vs 27% non-iMCA; p=0.57). 8 patients (1.3%) suffered an INE: five cases in the iMCA group vs three in the non-iMCA group (7.4% vs 0.6%; p< 0.001) (Table II). iMCA was significantly associated with risk of INE on univariable logistic regression (odds ratio (OR), 14.0; 95% confidence interval (CI), 3.4-69.5; p< 0.001) and after inverse probability of treatment weighting (IPTW)(weighted OR, 9.8; 95% CI 3.8-35.2; p< 0.001).

Conclusions: In this retrospective, single-center study of 600 patients undergoing TCAR for carotid artery stenosis, iMCA significantly increases the risk of post-operative stroke, regardless of symptomatic status. Our results therefore suggest that comprehensive intracranial imaging should be considered on all patients to optimally assess the CoW anatomy prior to flow reversal. Reducing flow reversal time alone may not suffice in mitigating INE risk after TCAR in iMCA patients, and we thus recommend considering alternatives to flow reversal in this patient population.