Introduction: Venous transit delay (VTD), a marker of poor venous outflow, has been successfully measured on CTP using time-to-maximum (Tmax) maps and is associated with unfavorable outcomes in patients with acute ischemic stroke (AIS) caused by large vessel occlusion (LVO). Mean transit time (MTT) is a perfusion parameter that encompasses both arterial input and venous outflow allowing for a more robust representation of cerebral arteriovenous transit time compared to Tmax which is heavily arterially weighted. In this study, using a Bayesian framework, we aimed to compare the association of VTD calculated from MTT and arterial delay (Tmax equivalent in Bayesian) with poor clinical outcomes after reperfusion in AIS-LVO patients. Methods: This retrospective study included AIS-LVO patients with baseline CTP and follow-up MRI from two comprehensive stroke centers. CTPs were processed with the Bayesian method using an FDA approved software (Olea Medical) to generate MTT and arterial delay (AD) maps. VTD was measured in the transverse sinus on both the ischemic and normal side and the posterior superior sagittal sinus (SSS) in each patient. Two outcome measures were included: Infarct growth (poor: ≥ 10 mL) and functional outcome defined by 90-day modified Rankin Scale score (mRS) (poor: ≥3). Results: A total of 80 patients were included (51% infarct growth ≥10 mL, 34% 90-day mRS≥3). MTT-derived VTD from the transvers sinus ipsilateral to the ischemic hemisphere was significantly longer in patients with substantial infarct growth (p=0.0007) and poor functional outcome (p=0.001). Similarly, MTT-derived VTD from the SSS was significantly longer in patients with substantial infarct growth (p=0.003) and poor functional outcome (p=0.012). However, AD-derived VTDs from the transverse sinus nor SSS were not significantly different (p>0.05) for either outcome measure. The difference between VTDs measured on MTT and AD (ΔVTD MTT -VTD AD ) was significantly higher in patients with substantial infarct growth (p<0.0001 for transverse sinus and p=0.0002 for SSS) and poor functional outcomes (p=0.0002 for transverse sinus and p=0.0307 for SSS). Conclusion: MTT-derived VTD measured in the transverse sinus and SSS was significantly different between patients with poor and favorable outcomes, which was not reflected on arterially weighted AD maps. This signifies the potential for MTT to be superior for VTD measurements and prediction of outcomes in AIS patients.
Halber et al. (Thu,) studied this question.