On average, someone in the U.S. has a stroke every 40 seconds. Acute ischemic stroke remains one of the leading causes of death and disability in the U.S. and around the world. The American Heart Association (AHA) estimates that in 2016 there were 5.5 million deaths attributable to cerebrovascular disease worldwide — 2.7 million of those deaths were from ischemic stroke. May is National Stroke Awareness Month and provides the opportunity to remember patients who are survivors of this dreaded disease and highlight the physicians and researchers at the forefront of progress to improve care and outcomes in stroke.
Over the last five years, there have been significant advancements in the treatment of acute ischemic stroke secondary to large vessel occlusion (LVO). LVO is an especially disabling form of ischemic stroke because a large territory of brain tissue and function is typically affected. Five landmark clinical trials published in the New England Journal of Medicine in 2015 and 2016 (MR CLEAN, ESCAPE, EXTEND IA, SWIFT PRIME, and REVASCAT) all demonstrated overwhelming benefit for mechanical thrombectomy for LVO. In summary, the studies suggested that only three patients need to be treated with thrombectomy to improve the functional outcome of one patient (number needed to treat (NNT) of 3). This makes mechanical thrombectomy one of the most effective treatments not only in stroke but in all of medicine. The AHA quickly amended its guidelines to recommend thrombectomy for ischemic stroke patients. However, the recommendation was reserved for a select number of indications, including:
- occlusions of the internal carotid artery (ICA) and proximal middle cerebral artery (MCA) segments of the cerebrovascular tree;
- those who had received intravenous (IV) tissue plasminogen activator (TPA);
- those with good baseline functional status; and
- those being treated within 6 hours of symptom onset.
These were significant steps in the right direction; however, there are still many patients who fall outside these indications which might benefit from mechanical thrombectomy.
Since then, indications for thrombectomy have expanded. In 2019, two additional trials were published in the New England Journal of Medicine (DAWN and DEFUSE3) that demonstrated similar positive outcomes in select patients being treated up to 24 hours from symptom onset. Research to establish the role of thrombectomy in several other groups of patients is ongoing, including studies involving:
- pediatric patients;
- the elderly;
- more distal occlusions in the cerebrovascular tree;
- posterior circulation occlusions;
- patients with mild stroke symptoms despite evidence of large vessel occlusion; and
- other conditions.
There remains much to learn about this powerful treatment, and hopefully, the indications for mechanical thrombectomy will continue to expand.
Another active area of research is the improvement in stroke care delivery. Researchers are developing new systems to administer care for stroke patients as quickly and efficiently as possible. Emergency medical services (EMS) and stroke triage systems are being redesigned, often across hospital systems. In some cases, the stroke care team is coming to the patient rather than the patient to the team. In other cases, patients with a high likelihood of LVO bypass closer primary stroke centers and are brought to comprehensive stroke centers for thrombectomy. Artificial intelligence-based tools help identify and select patients earlier for these advanced therapies. New diagnostic tools are being developed that can be utilized by EMS providers in the field. Robotic mechanical thrombectomy and the potential of tele-mechanical thrombectomy are exciting advances on the horizon.
Finally, stroke, large vessel occlusions and mechanical thrombectomy have become an area of interest amid the COVID-19 pandemic. Evidence is emerging from epicenters of the crisis — like New York City — that patients, whether afflicted with COVID-19 or not, are seeking medical attention later in their stroke course due to fears regarding COVID-19. We expect many studies to be published in the ensuing months evaluating stroke and mechanical thrombectomy in COVID-19 patients. We are excited about what the future holds in cutting edge research to bring the best available care to stroke patients everywhere.
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Justin R. Mascitelli, MD
University of Texas Health Science Center at San Antonio
St. Luke’s Baptist Hospital
San Antonio, Texas
Clemens M. Schirmer, MD, PhD, FAANS, FAHA
Chair, AANS/CNS Communications and Public Relations Committee
Wilkes Barre, PA