Acute stroke imaging selection for mechanical thrombectomy in the extended time window: is it time to go back to basics? A review of current evidence

Abstract

Treatment with endovascular therapy in the extended time window for acute ischaemic stroke with large vessel occlusion involves stringent selection criteria based on the two landmark studies DAWN and DEFUSE3. Current protocols typically include the requirement of advanced perfusion imaging which may exclude a substantial proportion of patients from receiving a potentially effective therapy. Efforts to offer endovascular reperfusion therapies to all appropriate candidates may be facilitated by the use of simplified imaging selection paradigms with widely available basic imaging techniques, such as non-contrast CT and CT angiography. Currently available evidence from our literature review suggests that patients meeting simplified imaging selection criteria may benefit as much as those patients selected using advanced imaging techniques (CT perfusion or MRI) from endovascular therapy in the extended time window. A comprehensive understanding of the role of imaging in patient selection is critical to optimising access to endovascular therapy in the extended time window and improving outcomes in acute stroke. This article provides an overview on current developments and future directions in this emerging area.

Comparison between collateral status and DEFUSE 3 or DAWN criteria in patient selection for endovascular thrombectomy within 6−24 hours after stroke: a protocol for meta-analysis

“…5 6 Moreover, patients with LVO in the extended time window can potentially benefit from EVT selected by simpler imaging triage. [7][8][9][10][11] Collateral vasculature status is important to compensate blood flow to the ischaemic area when the principal supplying arteries are occluded. 12 Good collaterals are related to limited ischaemic core and favourable clinical outcomes.…”

“…However, CTP is not available in many stroke centres, and the rigorous selection criteria are more likely to exclude patients who may benefit from EVT beyond 6 hours after stroke 5 6. Moreover, patients with LVO in the extended time window can potentially benefit from EVT selected by simpler imaging triage 7–11…”

Potential Approach to Quantifying the Volume of the Ischemic Core in Truncated Computed Tomography Perfusion Scans: A Preliminary Study

“…4 Computed tomography perfusion can measure the time-dependent changes in the density of the brain tissue using the flow of the contrast agents through the cerebral tissue. 5 Based on the time-density curve, several hemodynamic parameters, such as cerebral blood flow (CBF), cerebral blood volume (CBV), and time to maximum (T max ), can be generated to evaluate tissue microcirculation. The application of thresholds to different hemodynamic parameters has enabled the estimation of IC.…”

“…The application of thresholds to different hemodynamic parameters has enabled the estimation of IC. 5 An absolute CBVof <2 mL/100 g was used to define IC previously; however, a relative CBF of <30% of that in the normal hemisphere is more commonly used in the era of automated perfusion analysis software. 6 The contrast bolus characteristics, particularly the duration of contrast administration, play a crucial role in the adequate cerebral saturation of the iodinated contrast into the brain tissue during CTP.…”

“…In contrast, CT perfusion (CTP) can provide an objective and quantitative assessment of the volume of the IC 4 . Computed tomography perfusion can measure the time-dependent changes in the density of the brain tissue using the flow of the contrast agents through the cerebral tissue 5 . Based on the time-density curve, several hemodynamic parameters, such as cerebral blood flow (CBF), cerebral blood volume (CBV), and time to maximum (T max ), can be generated to evaluate tissue microcirculation.…”