Stroke Centers Increase and Refine Use of Thrombectomy

LOS ANGELES—The use of endovascular thrombectomy to treat patients with acute ischemic stroke increased dramatically in the United States in 2015 after several trials documented the clinical benefit of the therapy. Furthermore, stroke centers are refining and reshaping delivery of the treatment in concert with administration of IV t-PA, which remains a key component in producing the best outcomes for patients with a proximal occlusion of a large cerebral artery. In addition, recent findings have emboldened stroke specialists to seriously consider simplifying the brain imaging that stroke patients receive prior to these treatments, a step that could further cut time to intervention, while also making thrombectomy more widely available.

Thrombectomy Use Surges

Researchers at the University of California, San Francisco, documented a surge in the use of thrombectomy in 2015. Using the University HealthSystem Consortium database, the investigators analyzed data on the treatment of 357,973 patients with acute ischemic stroke who were hospitalized at any one of 161 US academic medical centers between October 2009 and July 2015. They tracked the percentage of patients treated endovascularly during each calendar quarter of the study period. They presented their results at the International Stroke Conference 2016.

During 2009 to 2013, use of endovascular treatment rose gradually, from 1.5% of patients with stroke in 2009 to 3.1% during the fourth quarter of 2012. Then, following three reports of no benefit from endovascular treatment that were presented at the International Stroke Conference in February 2013—the IMS III, MR RESCUE, and SYNTHESIS trials—the endovascular rate dropped to 2.6% and remained steady through the third quarter of 2014. But when the positive endovascular results from the MR CLEAN study became public in the final week of 2014, endovascular use began to quickly rise again, and then increased further during the first quarter of 2015, when three additional positive trial results were reported at the stroke conference in February 2015. By the end of the second quarter of 2015, usage stood at 4.7%, representing a projected year-over-year increase of about 150% for all of 2015, compared with 2014, reported Anthony S. Kim, MD, Medical Director of the Stroke Center at the University of California, San Francisco, and his associates.

To put these percentages in perspective, experts estimate that roughly 10% to 15% of all patients with stroke qualify for thrombectomy.

Their data also showed that the percentage of hospitals in the database that performed endovascular therapies for stroke rose steadily from about 40% of centers in 2009 to nearly 60% by mid-2015.

“Endovascular therapy with newer-generation devices is increasingly part of standard treatment for acute ischemic stroke,” the researchers said. In addition, they cited a “new urgency to evaluate regional access to embolectomy nationally and to identify system-based solutions to improve this access in underserved areas.”

Dramatic Change

Several stroke experts added their own anecdotal view of thrombectomy’s rapidly expanding use for appropriate patients with acute ischemic stroke during 2015, and the need for continued effort to broaden its US availability.

“The number of thrombectomies fell off after the negative 2013 trials and stayed flat until a year ago, but then jumped up. It has been very dramatic,” said Wade S. Smith, MD, PhD, Director of Neurovascular Services at the University of California, San Francisco, and one of the authors of the study.

“Thrombectomy use tremendously increased since February 2015,” said Mark J. Alberts, MD, Professor of Neurology and Neurotherapeutics and Medical Director of the neurology service at the University of Texas Southwestern Medical Center in Dallas. Despite this growth, “the major challenge [today] is geography”—reaching patients in suburban and rural areas who are not as close to the primarily urban medical centers that offer the procedure.

“We now have about 100 certified comprehensive stroke centers in the US,” and by definition, comprehensive stroke centers have the capability of treating patients with endovascular thrombectomy, noted Jeffrey Saver, MD, Professor of Neurology and Director of the Stroke Unit at the University of California, Los Angeles.

“Certification of these centers did not begin until about two to three years ago. But we probably need 300 to 400 of these centers” to provide thrombectomy to most US stroke patients, he said. “A lot of additional hospitals are close to certification. I anticipate that over the next one to two years we will be in the neighborhood of having the number of centers we need,” Dr. Saver said.

An Evolving Approach

In addition to expanding availability, the delivery of endovascular thrombectomy is evolving. A major trend is movement toward a parallel processing model in which patients with an acute clinical presentation of a stroke eligible for endovascular treatment simultaneously undergo CT angiography to confirm and localize the large-artery clot causing their stroke, receive IV t-PA, and undergo preparation for the endovascular access needed to remove the clot.

A pooled analysis of the recent positive endovascular thrombectomy trials that was presented at the conference “gives us a starting point to further improve the target metrics for imaging and puncture times,” Dr. Saver said. “We want to shorten door-to-needle times for t-PA and door-to-puncture times for thrombectomy, and the processes that need to be addressed for rapid delivery of both of these are very similar. We need for patients to only make a pit stop in the [emergency department], we need to have the catheterization team ready to go in the thrombectomy suite within 30 minutes, and we need to emphasize speed in access to the target clot rather than time-consuming diagnostic angiography.”

“We now face the issue of how to best integrate t-PA treatment and clot removal,” said Thomas A. Kent, MD, Professor of Neurology and Director of Stroke Research and Education at Baylor College of Medicine in Houston. “People are still trying to work that out. With parallel processing there is some overuse of resources. Some patients recover with t-PA alone and do not need thrombectomy,” he pointed out. “We are getting closer to the cardiology model of [myocardial infarction] treatment. It is now clear that there needs to be a simple, safe, and effective way to do both t-PA treatment and thrombectomy. We need to model ourselves on the cardiology experience.”

“If you can deal with the t-PA decision in the same room without moving patients from room to room, from a scanner to a catheterization suite, you can really shorten the time to treatment,” Dr. Smith explained. “This is identical to the model that cardiologists have developed. We should now consider taking stroke patients directly to the angiography room in addition to administering t-PA. We still need cross-sectional imaging, but the quality of the image from an angiography suite is probably sufficient to make a t-PA decision. So,<hl name="5"/> you can start t-PA while you are getting arterial access. The idea is simultaneous approaches to the patient, instead of serial.”

Efforts to establish the quickest route to endovascular thrombectomy have raised the question of whether t-PA remains necessary. The answer, at least for now, is that all signs indicate that giving t-PA helps and is worth delivering.

“The 2015 thrombectomy trials had big differences among them in the dosage of t-PA administered and in the percentage of patients who received t-PA. When 100% of patients received t-PA, they had the best outcomes,” Dr. Kent said. “There was a clear synergistic relationship between thrombectomy and t-PA. There has been a trend to think about sending patients straight to thrombectomy and skipping t-PA, but my colleagues and I think that we need to hold off on doing that. For now, if a patient is eligible to receive t-PA, they should get it and then quickly move to endovascular therapy. We are not yet ready to know it’s okay to go straight to endovascular treatment. In SWIFT-PRIME, it was pretty clear that the good outcomes were attributable to both [thrombectomy plus t-PA]. Treating patients with t-PA helps soften the clot to make it easier to remove, and improves flow through collateral arteries.”

Simpler Imaging to Save Time?

Although it’s not yet proven, another new wrinkle in working up patients with acute ischemic stroke for t-PA and thrombectomy treatment is the idea that simpler and more widely available CT imaging, especially CT angiography of cerebral arteries, may suffice for confirming and localizing the clot.

This concept received a significant boost at the International Stroke Conference in data reported from the Pragmatic Ischaemic Stroke Thrombectomy Evaluation (PISTE) trial, a study that compared treatment with t-PA alone with t-PA plus endovascular thrombectomy in 65 randomized patients who were treated at any of 11 UK centers. PISTE had a low enrollment level because the trial stopped prematurely in July 2015, after several completed trials had established the superiority of endovascular thrombectomy plus t-PA, thereby making it unethical to continue the randomized study.

This premature stoppage prevented PISTE from observing a statistically significant difference for its primary efficacy end point in favor of the combined treatment. The results did, however, show a nominal advantage to using thrombectomy plus t-PA over t-PA alone that was fully consistent with the other studies, said Keith W. Muir, MD, Professor of Neuroscience at the University of Glasgow.

But what made the PISTE results especially notable was that the trial achieved this consistent outcome with a simpler imaging protocol for patients during their workup that used only CT angiography, thus avoiding the cerebral CT perfusion imaging or MRI used in several of the other trials, noted Dr. Muir.

“PISTE raises the question of how much imaging is necessary,” Dr. Kent commented.

“The PISTE results are exciting. A lot of us believe that all we need to know is that there is a blockage in a target vessel,” Dr. Smith said. “If we have that information, then we can identify a population of patients who will benefit from [thrombectomy]. CT angiography is simple and can easily fit into work flows.”

“PISTE used a very simple imaging system that makes thrombectomy even more applicable and generalizable to less resourced health systems,” Dr. Saver said. “Although the results from PISTE were not internally statistically significant because the trial ended early, the results were consistent with the external studies of thrombectomy, so it provides further evidence for benefit from thrombectomy.” And because the consistent results were achieved with simpler imaging, it suggests simpler imaging may be all that is needed.

“That’s a major question to wrestle with,” Dr. Saver suggested. “We need additional trials with a head-to-head comparison of simpler and more sophisticated imaging so we can tailor treatment to patients who would benefit from simpler and faster imaging.”

—Mitchel L. Zoler

LOS ANGELES—The use of endovascular thrombectomy to treat patients with acute ischemic stroke increased dramatically in the United States in 2015 after several trials documented the clinical benefit of the therapy. Furthermore, stroke centers are refining and reshaping delivery of the treatment in concert with administration of IV t-PA, which remains a key component in producing the best outcomes for patients with a proximal occlusion of a large cerebral artery. In addition, recent findings have emboldened stroke specialists to seriously consider simplifying the brain imaging that stroke patients receive prior to these treatments, a step that could further cut time to intervention, while also making thrombectomy more widely available.

Thrombectomy Use Surges

Researchers at the University of California, San Francisco, documented a surge in the use of thrombectomy in 2015. Using the University HealthSystem Consortium database, the investigators analyzed data on the treatment of 357,973 patients with acute ischemic stroke who were hospitalized at any one of 161 US academic medical centers between October 2009 and July 2015. They tracked the percentage of patients treated endovascularly during each calendar quarter of the study period. They presented their results at the International Stroke Conference 2016.

During 2009 to 2013, use of endovascular treatment rose gradually, from 1.5% of patients with stroke in 2009 to 3.1% during the fourth quarter of 2012. Then, following three reports of no benefit from endovascular treatment that were presented at the International Stroke Conference in February 2013—the IMS III, MR RESCUE, and SYNTHESIS trials—the endovascular rate dropped to 2.6% and remained steady through the third quarter of 2014. But when the positive endovascular results from the MR CLEAN study became public in the final week of 2014, endovascular use began to quickly rise again, and then increased further during the first quarter of 2015, when three additional positive trial results were reported at the stroke conference in February 2015. By the end of the second quarter of 2015, usage stood at 4.7%, representing a projected year-over-year increase of about 150% for all of 2015, compared with 2014, reported Anthony S. Kim, MD, Medical Director of the Stroke Center at the University of California, San Francisco, and his associates.

To put these percentages in perspective, experts estimate that roughly 10% to 15% of all patients with stroke qualify for thrombectomy.

Their data also showed that the percentage of hospitals in the database that performed endovascular therapies for stroke rose steadily from about 40% of centers in 2009 to nearly 60% by mid-2015.

“Endovascular therapy with newer-generation devices is increasingly part of standard treatment for acute ischemic stroke,” the researchers said. In addition, they cited a “new urgency to evaluate regional access to embolectomy nationally and to identify system-based solutions to improve this access in underserved areas.”

Dramatic Change

Several stroke experts added their own anecdotal view of thrombectomy’s rapidly expanding use for appropriate patients with acute ischemic stroke during 2015, and the need for continued effort to broaden its US availability.

“The number of thrombectomies fell off after the negative 2013 trials and stayed flat until a year ago, but then jumped up. It has been very dramatic,” said Wade S. Smith, MD, PhD, Director of Neurovascular Services at the University of California, San Francisco, and one of the authors of the study.

“Thrombectomy use tremendously increased since February 2015,” said Mark J. Alberts, MD, Professor of Neurology and Neurotherapeutics and Medical Director of the neurology service at the University of Texas Southwestern Medical Center in Dallas. Despite this growth, “the major challenge [today] is geography”—reaching patients in suburban and rural areas who are not as close to the primarily urban medical centers that offer the procedure.

“We now have about 100 certified comprehensive stroke centers in the US,” and by definition, comprehensive stroke centers have the capability of treating patients with endovascular thrombectomy, noted Jeffrey Saver, MD, Professor of Neurology and Director of the Stroke Unit at the University of California, Los Angeles.

“Certification of these centers did not begin until about two to three years ago. But we probably need 300 to 400 of these centers” to provide thrombectomy to most US stroke patients, he said. “A lot of additional hospitals are close to certification. I anticipate that over the next one to two years we will be in the neighborhood of having the number of centers we need,” Dr. Saver said.

An Evolving Approach

In addition to expanding availability, the delivery of endovascular thrombectomy is evolving. A major trend is movement toward a parallel processing model in which patients with an acute clinical presentation of a stroke eligible for endovascular treatment simultaneously undergo CT angiography to confirm and localize the large-artery clot causing their stroke, receive IV t-PA, and undergo preparation for the endovascular access needed to remove the clot.

A pooled analysis of the recent positive endovascular thrombectomy trials that was presented at the conference “gives us a starting point to further improve the target metrics for imaging and puncture times,” Dr. Saver said. “We want to shorten door-to-needle times for t-PA and door-to-puncture times for thrombectomy, and the processes that need to be addressed for rapid delivery of both of these are very similar. We need for patients to only make a pit stop in the [emergency department], we need to have the catheterization team ready to go in the thrombectomy suite within 30 minutes, and we need to emphasize speed in access to the target clot rather than time-consuming diagnostic angiography.”

“We now face the issue of how to best integrate t-PA treatment and clot removal,” said Thomas A. Kent, MD, Professor of Neurology and Director of Stroke Research and Education at Baylor College of Medicine in Houston. “People are still trying to work that out. With parallel processing there is some overuse of resources. Some patients recover with t-PA alone and do not need thrombectomy,” he pointed out. “We are getting closer to the cardiology model of [myocardial infarction] treatment. It is now clear that there needs to be a simple, safe, and effective way to do both t-PA treatment and thrombectomy. We need to model ourselves on the cardiology experience.”

“If you can deal with the t-PA decision in the same room without moving patients from room to room, from a scanner to a catheterization suite, you can really shorten the time to treatment,” Dr. Smith explained. “This is identical to the model that cardiologists have developed. We should now consider taking stroke patients directly to the angiography room in addition to administering t-PA. We still need cross-sectional imaging, but the quality of the image from an angiography suite is probably sufficient to make a t-PA decision. So,<hl name="5"/> you can start t-PA while you are getting arterial access. The idea is simultaneous approaches to the patient, instead of serial.”

Efforts to establish the quickest route to endovascular thrombectomy have raised the question of whether t-PA remains necessary. The answer, at least for now, is that all signs indicate that giving t-PA helps and is worth delivering.

“The 2015 thrombectomy trials had big differences among them in the dosage of t-PA administered and in the percentage of patients who received t-PA. When 100% of patients received t-PA, they had the best outcomes,” Dr. Kent said. “There was a clear synergistic relationship between thrombectomy and t-PA. There has been a trend to think about sending patients straight to thrombectomy and skipping t-PA, but my colleagues and I think that we need to hold off on doing that. For now, if a patient is eligible to receive t-PA, they should get it and then quickly move to endovascular therapy. We are not yet ready to know it’s okay to go straight to endovascular treatment. In SWIFT-PRIME, it was pretty clear that the good outcomes were attributable to both [thrombectomy plus t-PA]. Treating patients with t-PA helps soften the clot to make it easier to remove, and improves flow through collateral arteries.”

Simpler Imaging to Save Time?

Although it’s not yet proven, another new wrinkle in working up patients with acute ischemic stroke for t-PA and thrombectomy treatment is the idea that simpler and more widely available CT imaging, especially CT angiography of cerebral arteries, may suffice for confirming and localizing the clot.

This concept received a significant boost at the International Stroke Conference in data reported from the Pragmatic Ischaemic Stroke Thrombectomy Evaluation (PISTE) trial, a study that compared treatment with t-PA alone with t-PA plus endovascular thrombectomy in 65 randomized patients who were treated at any of 11 UK centers. PISTE had a low enrollment level because the trial stopped prematurely in July 2015, after several completed trials had established the superiority of endovascular thrombectomy plus t-PA, thereby making it unethical to continue the randomized study.

This premature stoppage prevented PISTE from observing a statistically significant difference for its primary efficacy end point in favor of the combined treatment. The results did, however, show a nominal advantage to using thrombectomy plus t-PA over t-PA alone that was fully consistent with the other studies, said Keith W. Muir, MD, Professor of Neuroscience at the University of Glasgow.

But what made the PISTE results especially notable was that the trial achieved this consistent outcome with a simpler imaging protocol for patients during their workup that used only CT angiography, thus avoiding the cerebral CT perfusion imaging or MRI used in several of the other trials, noted Dr. Muir.

“PISTE raises the question of how much imaging is necessary,” Dr. Kent commented.

“The PISTE results are exciting. A lot of us believe that all we need to know is that there is a blockage in a target vessel,” Dr. Smith said. “If we have that information, then we can identify a population of patients who will benefit from [thrombectomy]. CT angiography is simple and can easily fit into work flows.”

“PISTE used a very simple imaging system that makes thrombectomy even more applicable and generalizable to less resourced health systems,” Dr. Saver said. “Although the results from PISTE were not internally statistically significant because the trial ended early, the results were consistent with the external studies of thrombectomy, so it provides further evidence for benefit from thrombectomy.” And because the consistent results were achieved with simpler imaging, it suggests simpler imaging may be all that is needed.

“That’s a major question to wrestle with,” Dr. Saver suggested. “We need additional trials with a head-to-head comparison of simpler and more sophisticated imaging so we can tailor treatment to patients who would benefit from simpler and faster imaging.”

—Mitchel L. Zoler

LOS ANGELES—The use of endovascular thrombectomy to treat patients with acute ischemic stroke increased dramatically in the United States in 2015 after several trials documented the clinical benefit of the therapy. Furthermore, stroke centers are refining and reshaping delivery of the treatment in concert with administration of IV t-PA, which remains a key component in producing the best outcomes for patients with a proximal occlusion of a large cerebral artery. In addition, recent findings have emboldened stroke specialists to seriously consider simplifying the brain imaging that stroke patients receive prior to these treatments, a step that could further cut time to intervention, while also making thrombectomy more widely available.

Thrombectomy Use Surges

Researchers at the University of California, San Francisco, documented a surge in the use of thrombectomy in 2015. Using the University HealthSystem Consortium database, the investigators analyzed data on the treatment of 357,973 patients with acute ischemic stroke who were hospitalized at any one of 161 US academic medical centers between October 2009 and July 2015. They tracked the percentage of patients treated endovascularly during each calendar quarter of the study period. They presented their results at the International Stroke Conference 2016.

During 2009 to 2013, use of endovascular treatment rose gradually, from 1.5% of patients with stroke in 2009 to 3.1% during the fourth quarter of 2012. Then, following three reports of no benefit from endovascular treatment that were presented at the International Stroke Conference in February 2013—the IMS III, MR RESCUE, and SYNTHESIS trials—the endovascular rate dropped to 2.6% and remained steady through the third quarter of 2014. But when the positive endovascular results from the MR CLEAN study became public in the final week of 2014, endovascular use began to quickly rise again, and then increased further during the first quarter of 2015, when three additional positive trial results were reported at the stroke conference in February 2015. By the end of the second quarter of 2015, usage stood at 4.7%, representing a projected year-over-year increase of about 150% for all of 2015, compared with 2014, reported Anthony S. Kim, MD, Medical Director of the Stroke Center at the University of California, San Francisco, and his associates.

To put these percentages in perspective, experts estimate that roughly 10% to 15% of all patients with stroke qualify for thrombectomy.

Their data also showed that the percentage of hospitals in the database that performed endovascular therapies for stroke rose steadily from about 40% of centers in 2009 to nearly 60% by mid-2015.

“Endovascular therapy with newer-generation devices is increasingly part of standard treatment for acute ischemic stroke,” the researchers said. In addition, they cited a “new urgency to evaluate regional access to embolectomy nationally and to identify system-based solutions to improve this access in underserved areas.”

Dramatic Change

Several stroke experts added their own anecdotal view of thrombectomy’s rapidly expanding use for appropriate patients with acute ischemic stroke during 2015, and the need for continued effort to broaden its US availability.

“The number of thrombectomies fell off after the negative 2013 trials and stayed flat until a year ago, but then jumped up. It has been very dramatic,” said Wade S. Smith, MD, PhD, Director of Neurovascular Services at the University of California, San Francisco, and one of the authors of the study.

“Thrombectomy use tremendously increased since February 2015,” said Mark J. Alberts, MD, Professor of Neurology and Neurotherapeutics and Medical Director of the neurology service at the University of Texas Southwestern Medical Center in Dallas. Despite this growth, “the major challenge [today] is geography”—reaching patients in suburban and rural areas who are not as close to the primarily urban medical centers that offer the procedure.

“We now have about 100 certified comprehensive stroke centers in the US,” and by definition, comprehensive stroke centers have the capability of treating patients with endovascular thrombectomy, noted Jeffrey Saver, MD, Professor of Neurology and Director of the Stroke Unit at the University of California, Los Angeles.

“Certification of these centers did not begin until about two to three years ago. But we probably need 300 to 400 of these centers” to provide thrombectomy to most US stroke patients, he said. “A lot of additional hospitals are close to certification. I anticipate that over the next one to two years we will be in the neighborhood of having the number of centers we need,” Dr. Saver said.

An Evolving Approach

In addition to expanding availability, the delivery of endovascular thrombectomy is evolving. A major trend is movement toward a parallel processing model in which patients with an acute clinical presentation of a stroke eligible for endovascular treatment simultaneously undergo CT angiography to confirm and localize the large-artery clot causing their stroke, receive IV t-PA, and undergo preparation for the endovascular access needed to remove the clot.

A pooled analysis of the recent positive endovascular thrombectomy trials that was presented at the conference “gives us a starting point to further improve the target metrics for imaging and puncture times,” Dr. Saver said. “We want to shorten door-to-needle times for t-PA and door-to-puncture times for thrombectomy, and the processes that need to be addressed for rapid delivery of both of these are very similar. We need for patients to only make a pit stop in the [emergency department], we need to have the catheterization team ready to go in the thrombectomy suite within 30 minutes, and we need to emphasize speed in access to the target clot rather than time-consuming diagnostic angiography.”

“We now face the issue of how to best integrate t-PA treatment and clot removal,” said Thomas A. Kent, MD, Professor of Neurology and Director of Stroke Research and Education at Baylor College of Medicine in Houston. “People are still trying to work that out. With parallel processing there is some overuse of resources. Some patients recover with t-PA alone and do not need thrombectomy,” he pointed out. “We are getting closer to the cardiology model of [myocardial infarction] treatment. It is now clear that there needs to be a simple, safe, and effective way to do both t-PA treatment and thrombectomy. We need to model ourselves on the cardiology experience.”

“If you can deal with the t-PA decision in the same room without moving patients from room to room, from a scanner to a catheterization suite, you can really shorten the time to treatment,” Dr. Smith explained. “This is identical to the model that cardiologists have developed. We should now consider taking stroke patients directly to the angiography room in addition to administering t-PA. We still need cross-sectional imaging, but the quality of the image from an angiography suite is probably sufficient to make a t-PA decision. So,<hl name="5"/> you can start t-PA while you are getting arterial access. The idea is simultaneous approaches to the patient, instead of serial.”

Efforts to establish the quickest route to endovascular thrombectomy have raised the question of whether t-PA remains necessary. The answer, at least for now, is that all signs indicate that giving t-PA helps and is worth delivering.

“The 2015 thrombectomy trials had big differences among them in the dosage of t-PA administered and in the percentage of patients who received t-PA. When 100% of patients received t-PA, they had the best outcomes,” Dr. Kent said. “There was a clear synergistic relationship between thrombectomy and t-PA. There has been a trend to think about sending patients straight to thrombectomy and skipping t-PA, but my colleagues and I think that we need to hold off on doing that. For now, if a patient is eligible to receive t-PA, they should get it and then quickly move to endovascular therapy. We are not yet ready to know it’s okay to go straight to endovascular treatment. In SWIFT-PRIME, it was pretty clear that the good outcomes were attributable to both [thrombectomy plus t-PA]. Treating patients with t-PA helps soften the clot to make it easier to remove, and improves flow through collateral arteries.”

Simpler Imaging to Save Time?

Although it’s not yet proven, another new wrinkle in working up patients with acute ischemic stroke for t-PA and thrombectomy treatment is the idea that simpler and more widely available CT imaging, especially CT angiography of cerebral arteries, may suffice for confirming and localizing the clot.

This concept received a significant boost at the International Stroke Conference in data reported from the Pragmatic Ischaemic Stroke Thrombectomy Evaluation (PISTE) trial, a study that compared treatment with t-PA alone with t-PA plus endovascular thrombectomy in 65 randomized patients who were treated at any of 11 UK centers. PISTE had a low enrollment level because the trial stopped prematurely in July 2015, after several completed trials had established the superiority of endovascular thrombectomy plus t-PA, thereby making it unethical to continue the randomized study.

This premature stoppage prevented PISTE from observing a statistically significant difference for its primary efficacy end point in favor of the combined treatment. The results did, however, show a nominal advantage to using thrombectomy plus t-PA over t-PA alone that was fully consistent with the other studies, said Keith W. Muir, MD, Professor of Neuroscience at the University of Glasgow.

But what made the PISTE results especially notable was that the trial achieved this consistent outcome with a simpler imaging protocol for patients during their workup that used only CT angiography, thus avoiding the cerebral CT perfusion imaging or MRI used in several of the other trials, noted Dr. Muir.

“PISTE raises the question of how much imaging is necessary,” Dr. Kent commented.

“The PISTE results are exciting. A lot of us believe that all we need to know is that there is a blockage in a target vessel,” Dr. Smith said. “If we have that information, then we can identify a population of patients who will benefit from [thrombectomy]. CT angiography is simple and can easily fit into work flows.”

“PISTE used a very simple imaging system that makes thrombectomy even more applicable and generalizable to less resourced health systems,” Dr. Saver said. “Although the results from PISTE were not internally statistically significant because the trial ended early, the results were consistent with the external studies of thrombectomy, so it provides further evidence for benefit from thrombectomy.” And because the consistent results were achieved with simpler imaging, it suggests simpler imaging may be all that is needed.

“That’s a major question to wrestle with,” Dr. Saver suggested. “We need additional trials with a head-to-head comparison of simpler and more sophisticated imaging so we can tailor treatment to patients who would benefit from simpler and faster imaging.”

—Mitchel L. Zoler