Some patients with an acute large-vessel ischemic stroke who already show a large-core infarct at early imaging can still benefit from thrombectomy, especially if the procedure successfully restores some vessel patency, a new registry study shows.
More than one in five patients with a large-vessel ischemic stroke in the anterior circulation who presented with a large-core infarct and underwent mechanical thrombectomy achieved 90-day functional independence in the study with more than 2000 patients.
That outcome was nearly five times more likely for patients who had successful recanalization, even if they had presented in the late time window of 6 to 24 hours after symptom onset.
"It has been thought patients with a large-core infarct would be unlikely to benefit from thrombectomy because the damage to the brain has already been done," Sami Al Kasab, MD, assistant professor of neurology and neurosurgery at Medical University of South Carolina, Charleston, commented to theheart.org | Medscape Cardiology.
"But our results show that around one-fifth of these patients can achieve an excellent functional outcome — a modified Rankin Scale score [mRS] of 0 to 2 — with thrombectomy. That is quite an acceptable number and should not be disregarded," said Al Kasab, who is colead author on the study report, published December 8 in JAMA Network Open.
He explained that patients with a large-core infarct stroke have a higher risk for reperfusion hemorrhage after recanalization, and although this was seen in the current study, 22% of patients still achieved an excellent outcome.
"And if we look at a good functional outcome [mRS of 0 to 3], that was achieved by 36.6% of patients with a large-core infarct stroke who underwent thrombectomy," he noted.
The authors explain in the report that mechanical thrombectomy has been shown in clinical trials to be associated with improved functional outcomes for patients with acute ischemic stroke presenting with proximal, anterior-circulation large-vessel occlusion and salvageable brain tissue. As a result, thrombectomy has become the standard of care for these patients.
The amount of brain affected by the stroke can be calculated using the ASPECTS score, a 10-point scoring system based on the extent of early ischemic changes detected on the baseline noncontrasted CT scan in which a score of 10 indicates normal and 0 corresponds to ischemic changes in all of the included regions.
Patients with an ASPECTS score lower than 6 had been excluded from most thrombectomy clinical trials because, it was thought, they would be unlikely to benefit. Therefore, data about their outcomes remain scarce, and whether these patients could still benefit from thrombectomy was unknown, the researchers note.
Although patients with a large-core infarct at presentation are unlikely to benefit from reperfusion to the same degree as those with either a small-core infarct or no-core infarct, the infarct size threshold for futility remains unknown, they state.
Previous reports have suggested potential benefits associated with thrombectomy for patients with a low baseline ASPECTS score, but the results have been limited by small numbers.
The current study explored the safety and effectiveness of thrombectomy in a real-world cohort of patients with large-vessel occlusion and large-core infarct in both the early thrombectomy window (less than 6 hours from symptom onset) and an extended thrombectomy window (6 to 24 hours after symptom onset).
They compared the outcomes of thrombectomy for patients with low (2 - 5) and high (6 - 10) ASPECTS scores. They also assessed thrombectomy outcomes of patients with a low ASPECTS based on reperfusion status and treatment in the early versus the extended window, hypothesizing that both of these factors would modify the outcome associated with thrombectomy.
The retrospective analysis used data from the Stroke Thrombectomy and Aneurysm Registry (STAR) which combines databases of 28 thrombectomy-capable stroke centers in Asia, Europe, and the United States.
It involved 2345 patients who presented with an occlusion in the internal carotid artery or M1 segment of the middle cerebral artery from 2016 to 2020. Of these, 2132 patients (90.9%) had an ASPECTS of 6 or more, and the remaining 213 patients had an ASPECTS of 2 to 5.
After a follow-up of 90 days, results showed that — as expected — the rate of a favorable outcome (mRS score of 0 to 2) was higher for those with the higher ASPECTS scores, being achieved by 36.2% of those with an ASPECTS of 6 to 10 and by 22.1% of those with an ASPECTS of 2 to 5.
In the group with a low ASPECTS score, those in whom some patency was achieved were more likely to have a positive outcome. Of the 176 patients who had a successful recanalization, 45 (25.6%) achieved an mRS score of 0 to 2, compared with just 5.4% of those who did not have successful recanalization (P = .007).
"This emphasizes the importance of reperfusion and shows that patients in whom thrombectomy is successful have a much better chance of achieving a good outcome," Al Kasab commented.
There was no control group of patients not undergoing thrombectomy in this study; however, the researchers note that only 9% of patients with an ASPECTS score of 0 to 7 showed a favorable outcome in the control group of another thrombectomy study, MR CLEAN.
Whereas a low ASPECTS score and presenting in the extended window were both associated with worse 90-day outcomes after potential confounders were controlled for (odds ratios of 0.60 [P = .002] and 0.69 [P = .001], respectively), there was no significant interaction between the two findings (P = .64).
Among patients with a low ASPECTS undergoing thrombectomy, there was no significant difference in likelihood of a favorable outcome between those presenting in the early window and those presenting in the extended time window.
It was achieved in 30 of 123 (24.4%) of those in the early window and in 17 of 90 (18.9%) of those in the late window (P = .34). There was no significant difference in 90-day mortality between those two groups (37.4% and 26.7%, respectively; P = .10).
"These results suggest that patients with a larger infarct volume still benefit from thrombectomy even beyond 6 hours from symptom onset," Al Kasab said.
There are five clinical trials ongoing "to answer the question about the effectiveness of thrombectomy for patients with acute stroke and a low ASPECTS," write the authors. In the meantime, "our study presents real-world outcome observations from a large, multicenter registry in the absence of strong evidence for or against thrombectomy in this group of patients," they state.
"I would say that unless patients are being enrolled in one of these trials," Al Kasab said, "our results support consideration of thrombectomy for patients with a large-core infarct stroke."
Al Kasab reports no conflicts; disclosures for the other authors are in the report.
JAMA Network Open. Published online December 8, 2021. Full text
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