Mechanical blood clot removal helps nearly half of stroke survivors to achieve good outcomes

Reviewed by Emily Henderson, B.Sc.Feb 11 2022

Mechanical removal of blood clots reduced post-stroke disability in nearly half of "all-comer" real-world stroke patients in an international study, according to preliminary late-breaking science presented today at the American Stroke Association's International Stroke Conference 2022. The conference is a world premier meeting for researchers and clinicians dedicated to the science of stroke and brain health being held in person in New Orleans and virtually, Feb. 9-11, 2022.

The most common type of stroke, an ischemic stroke, is caused by a blood clot in a blood vessel that blocks the flow of blood to the brain. Treatment usually involves clot-busting medications to dissolve the clot. For severe stroke within a large blood vessel, the treatment also may include a procedure to remove the clot – called mechanical thrombectomy or endovascular therapy – in which a tiny tube, or catheter, equipped with a special device on the end, is threaded through the blood vessel to grasp the clot and remove it.

Previous studies found that stroke patients who received mechanical clot removal had less disability after three months than those who did not. However, these studies were performed in carefully selected centers and employed strict clinical and imaging inclusion criteria, which decreases the generalizability of their findings.

To examine the effectiveness of blood-clot removal across a wide range of stroke patients seen in routine daily care (outside of a clinical trial), the Embotrap eXtraction & Clot EvaLuation & Lesion Evaluation for NeuroThrombectomy, or EXCELLENT trial, enrolled 1,000 adult ischemic stroke patients (average age 70, 52% female) at 36 sites worldwide, from September 2018 to March 2021. The sites were a mix of Thrombectomy-Capable and Comprehensive Stroke Centers. Patients were treated with a specific mechanical thrombectomy device called EmboTrap in an unlimited time frame.

Notably, the study was designed to collect real-world treatment and did not exclude patients based on pre-stroke independence level, severity of stroke, location of the occlusion, or time between onset of stroke and treatment, researchers said (as per current guidelines mechanical thrombectomy treatment can be used within 24 hours of symptom onset in select patients). In addition, the study analyzed the characteristics of the removed blood clots and how that impacted stroke recovery.

The study found that most of the patients required only one attempt to remove the blood clot. However, it is common to require multiple attempts to completely remove the clot. In nearly half of all patients, clot removal resulted in slight/minimal disability (able to look after own affairs without assistance or no worsening from their pre-stroke condition), as gauged by a standard scale measuring level of disability 90 days after stroke.

This study shows how much stroke thrombectomy has advanced. We saw a wide range of cases, including patients who, not too long ago, would not be considered good candidates for thrombectomy based on older age, pre-existing disability or large size of the stroke on presentation. Our findings in this study expand thrombectomy to be considered for more stroke patients."

Raul G. Nogueira, M.D., lead study author, director of the UPMC Stroke Institute and professor of neurology and neurosurgery at the University of Pittsburgh School of Medicine

The study also found blood clots that were rich in red blood cells and low in platelets resulted in less disability than blood clots composed of less red blood cells or those rich in red blood cells and high in platelet content.

Red blood cells contain the protein hemoglobin, which carries oxygen throughout the body. Fibrin is a protein, and platelets are cell fragments that help blood to clot, to help stop bleeding, however, in a stroke, clots block blood flow to the brain. Different proportions of these elements alter the blood clot consistency and its physical properties. This may facilitate or impair the clot removal procedure.

In this study, only 10% of patients whose clots had a higher composition of red blood cell count and a lower composition of platelets died within 90 days, compared to 24% of patients whose clots had a lower composition of red blood cells and platelets. Among patients with higher red blood cell content, 63% with lower platelet content had either slight or no disability, compared to 51% with higher platelet content.

"We knew that fibrin was associated with more difficult clot removal. However, this novel observation that platelets may modify clot properties is very intriguing," Nogueira said. "The results may have potential implications for technique and device selection when removing clots and the development of better blood-clot removal strategies."

Worldwide, stroke is the second-leading cause of death and a leading cause of long-term disability. Stroke is a medical emergency requiring immediate treatment, so it is important to recognize early signs and how to respond to them: Face drooping, Arm weakness, Speech difficulty, Time to call 9-1-1, remembered with the acronym F.A.S.T.