NEW YORK (Reuters Health) – Endovascular therapy (EVT) may be effective for acute ischemic stroke caused by occlusion of the middle cerebral artery M2 segment, suggests a multicenter retrospective study.

“Now that EVT is the standard of care for patients with large vessel occlusions, efforts should focus on expanding the treatment indications, as in the subgroup we studied, refining patients selection methods for endovascular therapy, which we are evaluating in the SELECT trial, and reorganizing systems of care so more patients have access to this highly effective treatment,” Dr. Amrou Sarraj from McGovern Medical School at The University of Texas Health Science Center at Houston told Reuters Health by email.

At least five published randomized clinical trials have found EVT to be superior to best medical management for patients with acute ischemic strokes with large vessel occlusion in the anterior circulation, but most of these involved the proximal (M1) segment of the middle cerebral artery (MCA).

Dr. Sarraj and colleagues used pooled data from 10 participating academic U.S. stroke centers to evaluate the safety and treatment effect of EVT compared with best medical management in 522 patients with acute ischemic stroke with large vessel occlusions in the M2 segment of the anterior circulation.

More patients treated with EVT (62.8%) than with best medical management (35.4%) had good 90-day clinical outcomes (odds ratio, 3.1; p<0.001), the researchers report in JAMA Neurology, online September 12.

Younger age, lower admission NIH Stroke Scale score, higher Alberta Stroke Program Early Computed Tomographic Score (ASPECTS), shorter time from last known normal state to reperfusion, and successful reperfusion were independently associated with good outcomes in the EVT group.

The EVT group had higher rates of symptomatic intracranial hemorrhage (5.6% vs. 2.1%) and lower rates of asymptomatic intracranial hemorrhage (5.2% vs. 7.3%), but neither of these differences achieved statistical significance.

“Our study results come in agreement with prior data showing that younger patients (younger than 80) with small core infarct (less early ischemic changes on CT) upon arrival with moderate to severe strokes who get treated within the 5 to 6 hours’ mark would benefit best from the intervention,” Dr. Sarraj said. “Those patients were shown over and over again to have the greatest benefit from endovascular therapy.”

“The main message we hope this study will send is that in patients with disabling strokes due to more distal occlusions, specifically M2 occlusions, endovascular therapy is effective, probably superior to best medical management including IV thrombolytics with a treatment effect similar to those with proximal occlusions in which EVT is the standard of care,” he said.

“We hope that, pending higher level evidence from a randomized controlled trial that we envision, patients with M2 occlusions presenting with disabling neurological deficits should be heavily considered for endovascular therapy and probably treated with the intervention to give them their best chances of better outcomes,” Dr. Sarraj added.

“The most important limitation of the study is that we do not know what made the physicians decide whether to treat a patient medically or with endovascular therapy,” writes Dr. Jonathan M. Coutinho from Academic Medical Center in Amsterdam in a related editorial. “As a result, we cannot exclude the possibility that residual confounding variables biased the results.”

“Although we must always be careful with the interpretation of results from nonrandomized studies, the data clearly suggest that it is at least reasonable to consider mechanical thrombectomy in these patients,” he adds. “Whether this consideration applies to all M2 occlusions remains to be seen.”

“Most likely, the decision to perform mechanical thrombectomy in a patient with an M2 occlusion will remain one that must be carefully weighed in each case,” Dr. Coutinho concluded. “However, that decision certainly has become a little easier with the data from this study.”

Dr. Gerhard Schroth from the University of Bern, Switzerland, who has published several studies of EVT for acute stroke, told Reuters Health by email, “M2 is a big artery and its occlusion should be treated by interventional neuroradiology.”

“If the clinical symptoms are severe (e.g., NIHSS more than 5), it should be treated by thrombectomy – what we call endovascular image-guided microsurgical thrombectomy – without any restriction,” he said. “The interventional neuroradiologist has to make a risk-benefit calculation, based on the vascular anatomy, which he investigates by DSA (Digital Subtraction Angiography).”

“The risk to perform an intervention may be too high, e.g., if the patient is agitated and moves the head (indicating intubation and general anesthesia) or if there is a severe arteriosclerotic process, e.g., with ipsilateral high-grade carotid stenosis,” Dr. Schroth said. “However – again – these are no absolute contraindications – our high-volume stroke center (more the 1,500 acute strokes, more than 200 thrombectomies per year) would aspirate or perform stent-retriever thrombectomy if the symptoms are severe.”