Aspiration Matches Stent Retriever for Stroke Reperfusion

February 23, 2017

HOUSTON, Texas — Aspiration of a clot was as effective as using stent retrievers in achieving successful reperfusion in patients with an ischemic stroke of the anterior circulation, a new trial shows.

Results of the ASTER trial were presented here at the opening session of the International Stroke Conference (ISC) 2017.

"Our results open the door for a new tool to remove the clot," Bertrand Lapergue, MD, Foch Hospital University Versailles Saint Quentin en Yvelines, Suresnes, France, concluded during his presentation.

Dr Lapergue noted that the gold standard for mechanical thrombectomy in ischemic stroke is the stent retriever, which has shown improvements in clinical outcomes vs tissue plasminogen activator alone now in at least five clinical trials.

Dr Bertrand Lapergue

An alternative technique is contact aspiration, in which a large-bore aspiration catheter is used to remove the blood clot via negative-pressure aspiration.

The ASTER trial is the first prospective, randomized, multicenter, controlled, open-label study with blinded outcome evaluation to compare the two approaches.

Commenting on the results for Medscape Medical News, American Heart Association/American Stroke Association spokesperson, Ralph Sacco, MD, University of Miami, Florida, said, "In the US right now the stent retriever is first line and used by most interventionists performing endovascular procedures for clot removal in ischemic stroke, because they have been proven in several major clinical outcome trials. Aspiration may be tried if a stent retriever is not successful.

"The ASTER trial shows for the first time in a head to head comparison that an aspiration device looks similar to the state-of-the-art stent retriever devices in ability to open up the vessel," he said. "This trial is intriguing, but the big question is, Should we change our practice based on a recanalization trial? Of course it would be better to have clinical outcomes too, but if recanalization is the same, I would bet clinical outcomes will be the same as we do have strong concordance on these.

"It is possible that this French trial is telling us that if you are good at using aspiration, then now we have some data that suggests it is as good as stent retrievers," Dr Sacco added. "However, I think most people in the US will want to wait for the US trial (COMPASS), which is underway comparing these two approaches. This is two thirds enrolled, so may be reported next year."

Michael Hill, MD, University of Calgary, Alberta, Canada, who led the ESCAPE trial of stent retrievers for mechanical thrombectomy in acute stroke, told Medscape Medical News that these new results from ASTER were "largely expected."

"We use aspiration in our center but usually go to stent retriever first," Dr Hill said. "I think that we remain concerned about two things with aspiration catheters: (1) distal embolization of fragments and (2) occlusion of collateral pathways through the anterior communicating artery with large-bore catheters."

He said this study will not change his practice.


The ASTER study was conducted in eight centers in France. For the study, 381 patients with a cerebral infarction in the anterior circulation and who were within 6 hours of symptom onset were randomly assigned to a stent retriever or aspiration with the Penumbra aspiration system as the initial approach to mechanical thrombectomy. If the initial approach failed after three attempts, then the other approach could be added as rescue therapy.

Key time metrics suggested that the aspiration strategy may be quicker from clot contact to restoring flow (13 minutes vs 23 minutes). "This could be important, as time is brain," Dr Lapergue said.

The primary endpoint was reperfusion rates: thrombolysis in cerebral infarction (TICI) 2b/3 flow. This was achieved in a similar number of patients in the two groups, as was the more impressive TICI-3 flow.

Table 1. Successful Reperfusion at the End of Endovascular Procedure

Endpoint Aspiration First (n = 192), n (%) Stent Retriever First (n = 189), n (%) P Value
TICI-2b/3 flow 164 (85.4) 157 (83.1) .53
TICI-3 flow 72 (37.5) 73 (38.6) .82
Use of adjunctive therapy 63 (32.8) 63 (32.8) .053


When only patients who achieved successful reperfusion using the initial strategy alone are considered, the results were similar.

Table 2. Successful Reperfusion After Frontline Strategy Alone

Endpoint Aspiration First (n = 192), n (%) Stent Retriever First (n = 189), n (%) P Value
TICI-2b/3 flow 121 (63.0) 128 (67.7) .33
TICI-3 flow 55 (28.6) 67 (35.4) .15


Safety endpoints also showed similar rates of complications in the two groups.

Table 3. Complications (Total Procedure)

Endpoint Aspiration First (n = 192), n (%) Stent Retriever First (n = 189), n (%) P Value
Embolization in a new territory 7 (3.6) 5 (2.6) .75
Arterial perforation 5 (2.6) 3 (1.6) .69
Arterial dissection 5 (2.6) 2 (1.1) .37
Vasospasm 5 (2.6) 12 (6.3) .08


Table 4. Complications (During Frontline Procedure Only)

Endpoint Aspiration First (n = 192), n (%) Stent Retriever First (n = 189), n (%) P Value
Embolization in a new territory 6 (3.1) 4 (2.1) .58
Arterial perforation 4 (2.1) 2 (1.1) .72
Arterial dissection 4 (2.1) 1 (0.5) .45
Vasospasm 5 (2.6) 12 (6.3) .08


Table 5. Safety Endpoints (Day 1)

Endpoint Aspiration First (n = 192), n (%) Stent Retriever First (n = 189), n (%) P Value
Symptomatic intracranial hemorrhage 10 (5.2) 12 (6.3) .63
Subarachnoid hemorrhage 13 (6.9) 13 (7.1)
Parenchymal hematoma (PH1) 17 (9.0) 19 (10.3)
Parenchymal hematoma (PH2) 7 (3.7) 14 (7.6)
New infarct 10 (5.3) 16 (8.5) .22


Subgroup analysis, clinical outcomes, and a cost-effectiveness analysis will be presented at the European Stroke Organisation Conference 2017 in May.

"There are times when it may be preferable to use aspiration — for example, a new cardiac embolism when the clot is still fresh and soft," Dr Sacco pointed out. "But often we don't know the cause of the blockage until we get there."

He added that race can also play a role in choosing with method to use. "African Americans, Hispanics, and Asians generally have more intracranial atherosclerosis — hardening of the arteries, which may cause stenosis — and in these cases, aspiration may not be enough. It may pull the clot out but the stent in the stent retriever also opens up the artery. So in these patients a stent retriever may be better. But in this trial — conducted in France — they thought the majority of their cases were embolic occlusions."

Dr Lapergue noted that both approaches are sometimes used together, and while this is a very effective strategy it is a costly one.

Commenting for Medscape Medical News, Bruce Ovbiagele, MD, professor and chief of neurology at Medical University of South Carolina, Charleston, and program chair of the ISC 2017, noted that quite a large proportion of patients (about one third) received both interventions in this study.

"It looks as though we might need both of these things," he said. "This trial does reflect the real world in that interventionists try one thing and if that doesn't work they move to another."

The ASTER study was funded by an unrestricted research grant from Penumbra. The sponsor was not involved in the study design or conduct, manuscript preparation, or manuscript review. Dr Lapergue reports no other disclosures apart from the research grant from Penumbra for this study.

International Stroke Conference (ISC) 2017. Abstract LB2. Presented February 22, 2017.

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