Data support “careful” use of mechanical thrombectomy in non-top tier evidence criteria ELVO patients

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Investigators have found that with strict adherence to top tier evidence criteria, half of ischaemic stroke patients with emergent large vessel occlusion (ELVO) may not be considered for mechanical thrombectomy even though according to their data, there is no increased risk of symptomatic intracerebral haemorrhage (sICH) and higher mortality is largely linked to occlusions in the basilar artery and patients treated at an extended time window.

Rohini Bhole (Stroke Team, Methodist University Hospital, University of Tennessee Health Science Center, Memphis, Tennessee, USA) and others state in the Journal of NeuroInterventional Surgery that this study comes in response to the recent guidelines for endovascular management of ELVO which award top tier evidence to the selective criteria that was implemented in the five positive trials (MR CLEAN, EXTEND-IA, ESCAPE, SWIFT PRIME, REVASCAT) in favour of mechanical thrombectomy for the treatment of acute ischaemic stroke.

The study’s aim then, was to understand how guideline adherence would have impacted treatment numbers and outcomes in a cohort of patients from a comprehensive stroke centre. The investigators compared disability and functional outcomes in patients that underwent mechanical thrombectomy at one comprehensive stroke centre, according to whether these patients met the top tier criteria for endovascular treatment set forth in the new guidelines (2015 AHA/ASA focused update of the 2013 guidelines for the early management of patients with acute ischaemic stroke regarding endovascular treatment: a guideline for healthcare professionals from the American Heart Association/American Stroke Association, published in the journal Stroke).

The authors conducted a retrospective observational study of consecutive acute ischaemic stroke patients registered in their centre’s database that were treated with mechanical thrombectomy between January 2012 and June 2015. All cases were coded as either meeting or not meeting top tier evidence recommendations based on their conformance to the following criteria presented in the new guidelines: pre-stroke modified Rankin Scale (mRS) score 0–1; acute ischaemic stroke with receipt of IV t-PA within 4.5 hours of symptom onset; causative occlusion of the internal carotid artery of proximal (M1) middle cerebral artery (MCA); age 18 years or older; National Institute of Health Stroke Scale (NIHSS) score of ≥6; Alberta Stroke Program Early CT (ASPECT) score of ≥6 and; treatment that can be initiated (groin puncture) within six hours of symptom onset.

Further, “Prospectively collected outcome and process data were used in this retrospective cohort study as the following dependent variables: neurological improvement during hospitalisation (defined as the difference between pretreatment and discharge NIHSS scores); sICH, defined as per the SITS-MOST definition; serious haemorrhage (defined as life-threatening systemic haemorrhage requiring transfusion); time from groin puncture to recanalisation; post-recanalisation TICI grade; endovascular procedural complications; and 90-day mortality and mRS score.”

A total of 126 ELVO patients treated with mechanical thrombectomy were included in the analysis. Of them, 64 patients fulfilled top tier evidence criteria (mean age 64±15 years; 47% men; median pretreatment NIHSS score 16 (IQR 14­–18)), and 62 patients did not meet top tier evidence criteria (mean age 62±13 years; 52% men; median pretreatment NIHSS score 14 (IQR 7–18)). The authors state: “Charateristics not meeting top tier evidence for mechanical thrombectomy in the comparision group included six (10%) patients with a pretreatment NIHSS score of ˂6, 4 (6.5%) patients with an ASPECT score ˂6, 17 (27%) patients with a premorbid mRS score ≥2, 6 (10%) patients with M2 occlusions, 20 (32%) patients with posterior circulation occlusions, and 36 (58%) patients with symptom to groin puncture time >6 hours. Twenty-six (42%) patients had two or more characteristics removing them from the top tier evidence group.”

They report that IV t-PA was given to 92% of patients in the top tier group, versus 40% (p˂0.001) in the non-top tier group, primarily due to late arrival after symptom onset. Similarly, patients in the top tier group had shorter symptom onset to groin puncture times (234 min (IQR 177–291) vs. 381 min (IQR 268–454) p˂0.001), but the median door to puncture times between the two groups were not significantly different (151 min (IQR 115–190) vs. 149 min (IQR 115–237), p=0.628).

Further, they write that median ASPECT scores were also higher in patients meeting top tier criteria compared with those not meeting top tier criteria (10 (IQR 10–10) vs. 9 (IQR 8–10), p=0.001). Additionally, cases not meeting top tier evidence included 20 (32%) basilar artery occlusions, and of these, 11 (55%) died, while five (25%) achieved mRS ≤2 at the three-month follow-up.

Finally, the investigators report that rates for sICH were 8% in each group, and serious haemorrhage rates were similar at 8% in the top tier group, compared with 10% in the non-top tier group (p=0.731). Patients in the top tier group also achieved greater neurological improvement during hospitalisation (10 points (IQR 6–14)) compared with the patients in the non-top tier group (5 points (IQR 1–10); p=0.006) in initial univariate analyses. Mortality was significantly lower in the top tier evidence group at 26% compared with 45% in other cases (p=0.044), whereas favourable outcome (mRS ≤2) at three months was similar at 46% in the top tier evidence group versus 33% non-top tier evidence group (p=0.158).

They explain, “After adjusting for potential imbalances between the two groups, including baseline ASPECT score, IV t-PA pretreatment, intubation and time elapsed from symptom onset to groin puncture, associations between endovascular mechanical thrombectomy in top tier evidence cases and others did not reach statistical significance in multivariate analysis.”

Overall, the study showed that despite lacking top tier evidence for mechanical thrombectomy, “33% of cases treated outside these recommendations attained an mRS score of ≤2 by three months, and that nearly half of the mechanical thrombectomy cases would have been denied mechanical thrombectomy if top tier evidence criteria were upheld in clinical practice. Additionally, the data indicated no increased risk of sICH or serious haemorrhagic complications in the group that lacked top tier evidence for mechanical thrombectomy, demonstrating that a sizeable percentage of patients not meeting top tier criteria may still have a good outcome with mechanical thrombectomy.”

Finally, commenting on the devices used for mechanical thrombectomy, the authors add, “Despite guidelines endorsing stent retrievers as the technology of choice for thrombectomy, our data showed that in clinical practice, aspiration and a combination of technologies (aspiration and stent retrievers) played a greater role in the treatment of ELVO.”