Long Article

Direct Aspiration for Thrombectomy in Ischemic Stroke Patients: Is it Viable?

Stroke is a leading cause of disability and ranks as the fifth cause of death in the U.S.1,2 Ischemic stroke, the most common type, is caused by occlusions in the vessels flowing to the brain and accounts for approximately 87 percent of all strokes.1,2 Despite the enormous human and economic toll of acute ischemic stroke (AIS), historically, little could be done to halt the devastating effects until 1995 when a pivotal clinical trial, conducted by the National Institute of Neurological Disorders and Stroke, demonstrated that treatment with intravenous recombinant tissue plasminogen activator (t-PA) given within three hours of the onset of an AIS improved clinical outcome at three months.3 4

While the introduction of t-PA shifted the paradigm in stroke treatment—with subsequent clinical trials further demonstrating the efficacy of tPA up to 4.5 hours—there continued to be a significant need to expand the therapeutic window beyond 4.5 hours, since only a small percentage of eligible ISA patients were actually receiving tPA, and, tPA also carried the risk of cerebral and systemic hemorrhage. 5

The Advent of Stent Retrieval Thrombectomy Plus tPA

Given the continuing unmet need for faster, more effective stroke treatment in conjunction with administration of tPA, several studies using mechanical thrombectomy were conducted to order to develop a safer therapeutic intervention that could remove clots more rapidly. By 2015, the landmark MR CLEAN study, which involved 500 patients with a proximal intracranial arterial occlusion, found that 32.6 percent of patients who had their clot removed within 6 hours after the onset of a large vessel occlusion (LVO), plus tPA, with a retrievable stent, or with aspiration or wire disruption, had substantially reduced disability and increased independence three months following the stroke.6 Stent retrievers for AIS perform two critical mechanisms of action: the immediate recanalization, or restoration, of blood flow, and the retrieval of the clot.7  Since the publication of the MR CLEAN findings, mechanical thrombectomy plus tPA has revolutionized stroke treatment and become the standard of care for LVO strokes, with stent-retrievers the preferred technique for the endovascular management of AIS.7,8  As stent-retriever techniques have continued to be refined, the next-generation of thrombectomy devices, particularly stent-retrievers with large-bore aspiration catheter systems, have become an alternative technique of thrombectomy via direct aspiration.8 While the direct aspiration first-pass technique (ADAPT has gained in popularity, there have been questions regarding the level of evidence in support of its use as a first line approach in AIS.9

Direct Aspiration Thrombectomy: Evidence of A Viable Alternative

In direct aspiration thrombectomy, the clot is removed via suction applied with a large bore distal access catheter at the face of the clot.8 If treatment fails, rescue treatment with stent retrieval is performed. 8 While stent retrieval thrombectomy has remained the first line approach in AIS treatment, over the past several years, a number of clinical trials and meta-analyses have been conducted with the goal of comparing the efficacy of the ADAPT direct aspiration technique to stent-retriever thrombectomy. Chief among these studies has been the Contact Aspiration vs Stent Retriever for Successful Revascularization (ASTER) study, which was initially designed as a “superiority” trial designed to study aspiration thrombectomy in comparison with stent retrievers.8

While the study failed to show neither superiority nor non-inferiority of direct aspiration to stent retrievers, subsequent trials did show that, while the aspiration could cause emboli in a subset of patients, direct aspiration also had a faster puncture-to-recanalization time with better cost-effectiveness over stent-retriever thrombectomy. 8 Subsequent clinical trials, as well as analyses of the ASTER study results, also provided support for the concept that aspiration and stent-retrievers performed comparably.8,10  

In a further test of this concept, the COMPASS (A Comparison of Direct Aspiration vs. Stent Retriever as a First Approach) trial, was designed as a “non-inferiority” study in order to examine the evidence for direct aspiration as a viable method for thrombectomy. The results of the study, published in the March 9, 2019 issue of Lancet found that found that “direct aspiration as first pass thrombectomy conferred non-inferior functional outcome at 90 days compared with stent retriever first line thrombectomy.”11 Thus, the study supports the use of direct aspiration as an alternative to stent retriever as first-line therapy for stroke thrombectomy.10

Based on the most recent evidence, it would now appear that both direct aspiration for first-line thrombectomy in ISA, as well as first-line stent retriever thrombectomy, are viable, evidence-based options for endovascular thrombectomy in the appropriate patients.10



  1. Stroke Facts, Centers for Disease Control and Prevention, 2017. https://www.cdc.gov/stroke/facts.htm  Accessed March 25, 2019.
  2. Heart disease and stroke statistics—2017 Update: A Report from the American Heart Association. Circulation, https://www.ncbi.nlm.nih.gov/pubmed/28122885 Accessed March 25, 2019.
  3. A Brief History of Acute Stroke Care. Aging, August, 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6128437/ Accessed March 25, 2019.
  4. Tissue Plasminogen Activator for Acute Ischemic Stroke. The National Institute of Neurological Disorders and Stroke rt-PA Stroke Study Group, JAMA, December, 1995. https://www.nejm.org/doi/10.1056/NEJM199512143332401?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dwww.ncbi.nlm.nih.gov. Accessed March 26, 2019.
  5. Stent-Retriever Thrombectomy after Intravenous t-PA vs. t-PA Alone in Stroke, NEJM, June, 2015. https://www.nejm.org/doi/10.1056/NEJMoa1415061?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dwww.ncbi.nlm.nih.gov. Accessed March 26, 2019.
  6. In Landmark Study, Intra-Arterial Treatment Found to Lead to Less Disability in Stroke Patients, Neurology Today: January 2015. https://journals.lww.com/neurotodayonline/Fulltext/2015/01220/In_Landmark_Study,_Intra_Arterial_Treatment_Found.1.aspx Accessed March 26, 2019. 
  7. Techniques for Endovascular Treatment of Acute Ischemic Stroke from Intra-Arterial Fibrinolytics to Stent-Retrievers, Stroke, American Heart Association, 2105. https://www.ahajournals.org/doi/pdf/10.1161/STROKEAHA.114.007935.  Accessed March 26, 2019. 
  8. The Aspirations of Direct Aspiration for Thrombectomy in Ischemic Stroke: A Critical Analysis, Journal of Stroke 2019. https://www.j-stroke.org/journal/view.php?number=259 Accessed March 25, 2019.
  9. A Direct Aspiration First-Pass Technique Vs Stent Retriever Thrombectomy In Emergent Large Vessel Intracranial Occlusions, Frontiers in Neurology, September 2018. https://www.ncbi.nlm.nih.gov/pubmed/28409731  Accessed March 27, 2019.    
  10. COMPASS Published: Experts See Level I Evidence in Support of Aspiration Thrombectomy for Stroke, TCTMD of the Cardiovascular Research Foundation, March 2019.  https://www.tctmd.com/news/compass-published-experts-see-level-i-evidence-support-aspiration-thrombectomy-stroke Accessed March 27, 2019.   
  11. Aspiration Thrombectomy for Stroke vs Stent Retriever Thrombectomy As First-Line Therapy for Stroke Thrombectomy, Abstract retrieved from PubMed, Lancet, March, 2019. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(19)30297-1/fulltext?rss=yes Accessed March 28, 2019.