Light Transmission Aggregometry Versus VerifyNow for Antiplatelet Monitoring in Flow Diversion: A Retrospective...

Background: Over the past two decades, the widespread use of flow diversion stents (FDS) has significantly expanded treatment options for patients with intracranial aneurysms (IA). However, FDS implementation requires antiplatelet therapy (APT), the optimal regimen for which remains undefined. This study aimed to evaluate light transmission aggregometry (LTA) as a routine tool for monitoring antiplatelet therapy during flow diversion to examine whether an LTA-based residual-reactivity cut-off is associated with thromboembolic complications and to assess the agreement between LTA and VerifyNow (VN) P2Y12 reaction units (PRU), rather than to establish definitive safety thresholds. Methods: A retrospective analysis was conducted across two expert centers on 771 patients. Based on selection criteria, 203 IA patients who underwent FDS implantation between 2019 and 2023 with LTA-guided APT (clopidogrel plus aspirin) were included; LTA was used for monitoring in all 203 patients, and a subset of 84 patients additionally underwent VerifyNow testing for method comparison. The primary outcome was clinically significant thromboembolic complications (TECs) leading to a reduction in quality of life by ≥1 point on the modified Rankin scale (mRS). The secondary outcome was intracranial hemorrhage. Results: Among the 203 patients (203 FDS implantations), dual aggregometry control (LTA + VN) was performed in 84 cases. At the 12-month follow-up, complete or near-complete aneurysm occlusion was radiologically confirmed in 83.7% of patients. A favorable functional outcome (mRS ≤ 2) at 12 months was observed in 97.5% of cases. Thromboembolic complications occurred in 7 patients (3.4%) and hemorrhagic complications in 4 (2.0%). On receiver operating characteristic (ROC) analysis, the control-LTA cut-off of 44% showed only weak, statistically non-significant discrimination for thromboembolic events (area under the curve, AUC 0.700, 95% confidence interval, CI 0.479-0.920; p = 0.073). In the 84 patients tested with both assays, LTA and VerifyNow PRU correlated only moderately (Spearman's ρ = 0.51; Pearson's r = 0.53) and showed wide Bland-Altman limits of agreement, indicating that the two methods are not clinically interchangeable. Conclusions: Routine platelet-function aggregometry may be a useful tool for monitoring APT during flow diversion. In this retrospective cohort, lower residual platelet reactivity on LTA was associated with fewer thromboembolic and hemorrhagic events; however, given the small number of outcome events (n = 7) and an LTA cut-off whose discriminative ability did not reach statistical significance, this association is exploratory and hypothesis-generating rather than an established safety threshold. LTA and VerifyNow PRU were not clinically interchangeable, so no VerifyNow cut-off is proposed. Prospective, adequately powered studies with outcomes stratified directly by each assay are required to define and validate clinically applicable thresholds.