Removing a clot blocking a medium- or small-sized artery in the brain via a mechanical thrombectomy procedure proved to be a safe treatment for ischaemic stroke but did not lessen disability more than the current ‘best medical treatment’ alone—including clot-busting medication, if indicated—according to study findings presented as preliminary late-breaking science at the International Stroke Conference (ISC; 5–7 February, Los Angeles, USA).
An estimated 20–40% of patients with ischaemic strokes have a clot blocking one of several medium- or small-sized arteries above the base of the brain—a distal/medium vessel occlusion (D/MeVO)—explained Marios Psychogios (University Hospital Basel, Basel, Switzerland), lead study author and co-principal investigator for the DISTAL trial.
“Given the high and rising prevalence of ischaemic strokes in ageing populations, stroke in medium/distal vessels represents a significant and growing health concern,” he said. “While these strokes were traditionally thought to have a favourable prognosis, findings from recent studies suggest that only half of people regain functional independence, underscoring the urgent need for more effective treatments.”
American Heart Association/American Stroke Association guidelines from 2019 on the early management of patients with acute ischaemic stroke recommend mechanical clot removal within 24 hours of symptom onset for selected patients with clots blocking large arteries. For clots blocking medium vessels, the guidelines note that, “although the benefits are uncertain, the use of mechanical thrombectomy with stent retrievers may be reasonable” for carefully selected ischaemic stroke patients within six hours of symptom onset.
Launched in 2021, the DISTAL trial investigated whether thrombectomy in addition to best medical therapy—often including intravenous clot-busting medications—was able to reduce disability compared to clot-busting treatment alone. The trial included 543 adult patients (44% women; average age, 75 years; 98% white) who entered one of 55 hospitals across Europe with disabling stroke symptoms. Imaging tests confirmed a medium/distal vessel blockage in all participants, with participants then being randomly selected to receive either only standard stroke care (n=272, of whom 66% received clot-busting drugs) or standard care/clot busters plus thrombectomy treatment to remove their clot (n=271).
The researchers found that roughly 63% of patients in the trial had no disability—as per the modified Rankin scale (mRS)—before their stroke, while average stroke severity at hospital admission was moderate, with a median score of six on the 42-point National Institutes of Health stroke scale (NIHSS). In addition, on imaging, occlusions were visualised mainly in the M2 (44%) or M3 (27%) segments of the middle cerebral artery, or in the P2 (14%) or P1 (6%) segments of the posterior cerebral artery.
The effectiveness of the treatment was measured via the patients’ disability and need for assistance in daily activities (mRS) 90 days post-stroke, with decisions about the exact devices and procedures used for thrombectomy being left to the treating physician. Ninety-day follow-up analysis of DISTAL revealed the following outcomes:
- There was no significant difference in disability between those receiving thrombectomy plus standard medical care and those receiving standard medical care alone
- There were similar rates of death for each group—15.5% for those receiving thrombectomy plus standard medical care versus 14% among those receiving standard medical care alone
- Rates of severe (symptomatic) brain bleeds were 5.9% for those receiving thrombectomy plus standard medical care versus 2.6% with standard medical care alone
“Endovascular therapy [thrombectomy] with the current techniques may not always provide extra benefits, so it could be worth reconsidering it as the standard treatment for medium/distal vessel blockages. However, it is a safe option that can still be considered for select people on a case-by-case basis,” commented DISTAL co-principal investigator Urs Fischer (University Hospital Bern, Bern, Switzerland).
The lack of added benefit with thrombectomy was confirmed when researchers analysed specific subsets of people, such as those who did not receive intravenous clot-busting medications and those who had more severe strokes.
“We were surprised at the overall outcome of the participants, which was worse than we anticipated based on retrospective data,” Psychogios stated.
The DISTAL researchers are currently conducting a detailed analysis on whether thrombectomy was more or less effective in different subgroups of patients, perhaps enabling them to identify characteristics that might be associated with a more positive outcome following the treatment.
In addition, because almost all participants in the study were white, the results may not be generalisable to other populations. Further possible limitations include the fact that, while the study’s design offered the benefit of looking at the real-world application of mechanical clot removal, it may have restricted the researchers’ ability to detect positive effects from it that would have been apparent in a more selective patient group. In addition—as stated in an American Heart Association press release—physicians who already believed that thrombectomy was a superior treatment could have treated patients with the procedure outside of the trial rather than “taking the chance” that their patients might be randomised to standard medical treatment alone.
“While the results of the DISTAL trial might seem discouraging, we see it as a wakeup call to continue investigating treatment options for medium or distal vessel occlusion patients, as outcomes appear to be more severe than expected and evidence-based effective treatment options are still lacking,” Psychogios added.
