a mismatch between the severity of the clinical decit and the infarct volume, which was dened according to the following cri­teria: those in group A were 80years of age or older, had a score of 10 or higher on the NIHSS (scores range from 0 to 42, with higher scores indicating a more severe decit), and had an infarct volume of less than 21 ml. The participants in group B were younger than 80years of age, had a score of 10 or higher on the NIHSS, and had an infarct volume of less than 31ml. Those in group C were younger than 80years of age, had a score of 20 or higher on the NIHSS, and had an infarct volume of 31 to less than 51ml. Infarct volume was assessed with the use of DW-MRI or CTP and was measured with the use of automated software (RAPID, iSchemaView). Patients were randomly assigned to thrombectomy plus standard care (the thrombectomy group) or to standard care alone (the control group) [60].

The development of better equipment and improved devices for EVT resulted in improved rates of successful reperfusion, consis­tent with the post-2015 trials era. More recently, there has been a shift toward producing improved techniques and devices, improved imaging, and formulating better treatment and triage algorithms.

Multiple studies, including a meta-analysis, demonstrated the stratication of the increasingly improved reperfusion rates achieved by EVT; they elucidated that rst-pass reperfusion, com­pared to reperfusion achieved after a rst failed attempt, resulted in improved functional outcomes. These successful initial attempts have been termed rst-pass effect (FPE) [62].

In the aforementioned meta-analysis, which was composed of 21 studies and 2747 patients, FPE patients had lower mortality rates than patients who did not have FPE.Moreover, further strat­ication endorsed that complete reperfusion with a single pass (FPE-mTICI 3) was associated with better 3-month outcomes compared with FPE-mTICI 2B (mRS 0–2, 66 vs. 46%; OR, 0.46; 95% CI, 0.037–0.57), better mortality rates (8% vs. 14%), and less intracranial hemorrhage (22% vs. 31%). This connection established between recanalization rates, FPE and clinical out­come, established a new threshold, FPE-mTICI 2B or even FPE­mTICI 2c-3, which is gaining wide acceptance as a new benchmark for evaluating thrombectomy devices. This can be attributed to the latest trials, in which devices achieve >90% reperfusion rates, and there is very little differentiating them [16–18].

has substantially improved. However, randomized controlled trials demonstrating a correlation between these new technologies and an improvement in recanalization, functional outcomes, and reduced complications when compared with existing stent retriev­ers have yet to be performed. Moreover, performance comparison has been limited mainly to historical cohorts and results achieved by landmark past studies.

of the device, titled “Analysis of Revascularization in Ischemic Stroke with EmboTrap (ARISE II).” This study enrolled 227 patients. The mTICI 2b reperfusion rate within three passes was

Another third-generation stent retriever is the three- dimensional (3D) revascularization device (Penumbra Alameda, CA, USA). A multicenter, randomized controlled trial with 198 enrolled patients was conducted to evaluate the safety and efcacy of this device in combination with an intermediate catheter. Of the 198 recruited patients, 98 underwent thrombectomy with the 3D stent retriever in conjunction with an intermediate catheter and achieved mTICI 2b-3 reperfusion in 81.9% of the patients, signicantly higher than the comparison arm, where direct aspiration alone with an intermediate catheter achieved only mTICI 2b-3 reperfusion rate of 69.8% in 100 patients [64].

Initially, a proprietary aspiration pump was used to generate a continuous negative suction of up to 20mm Hg with the separator moved back and forth to clear the ingested clot. Later on, the forced aspiration thrombectomy (FAST) technique was used as a secondary procedure when revascularization failed with the PS separator. Manual aspiration with a 20/50cc syringe was done through the reperfusion catheter without the separator, resulting in an improved rate of recanalization in comparison to the original PS technique.

further in the cerebral vasculature tree in a safe manner. Prior sci­entic examination has similarly established the powerful rela­tionship of ID to pressure loss and ow rate in small vessels. To take advantage of this principle, three new larger bore 0.071- to

when compared with static aspiration. This may be attributed to the initial clot softening from dynamic compression or to dynamic friction being less than the static friction that occurs when the thrombus is stuck at the tip of the catheter. This concept was tested and conrmed in a different study using various types of catheters with different inner diameters (0.054–0.088 in). In this study, the use of cyclic aspiration (18–29 inHg, 0.5Hz) resulted in better clot ingestion into the aspiration catheter and effectively reduced the rate of distal emboli.

After the failure of the ASTER trial, the similar reperfusion rates between modalities led a North American group to change track and conduct a noninferiority trial in 15 North American sites. The goal was to once again compare the efcacy between large-bore direct aspiration and stent retrievers. Titled COMPASS, this trial featured 270 patients without a large early infarct core (ASPECTS>6) and who presented within 6 hours of onset. Ultimately, 134 received direct aspiration as rst-line treatment and 136 received stent retriever use as rst-line treatment. Direct aspiration achieved 52% good functional outcomes at 3months, which was comparable with the 50% achieved by rst-line stent retriever use and reached noninferiority in the analysis (p=0.0014). This trial was the landmark trial to provide level 1 evidence in support of direct aspiration. Moreover, the authors stated that even in the event of failure of direct aspiration, the large-bore catheter was still at the clot face and that a stent retriever could be quickly deployed over the thrombus. This led to a signicantly shorter procedural duration in the initial direct

aspiration arm when compared with stent retriever use. An addi­tional benet noted was the cost-effectiveness of aspiration cath­eters.

Considering this new evidence, the 2019 AHA/ASA updated the guidelines for stroke management assigned to ADAPT a level of I B-R (moderate quality of evidence) [4]. In addition, the SNIS Standards and Guidelines Committee [5] conrmed MT guide­lines for posterior circulation stroke.

An exchange method or coaxial advancement technique is used to place the GC.The tip is usually parked at the ICA bulb or V1/V2 segments [50]. Generally, CGCs such as Neuron or Envoy are better suited in the posterior circulation, while DACs require a triaxial system and are of use in more distal occlusions or tortuous vessels. Both DAC and CGC are brought as close to the occlusion as possible to reduce the retrieval corridor and thrombus disper­sion. The efciency of aspiration, however, is reduced due to their narrower lumens.