Thrombectomy emerges as new treatment to remove clots and stop strokes
By Tony Craine
In April 2015, Mailis Toop fell ill during a college class and was rushed to University of Iowa Hospitals and Clinics. The 29-year-old woman had described unusual vision problems to her classmates before losing her ability to speak or control her limbs.
“When she arrived here, she was starting to deteriorate,” says UI neurointerventionist Santiago Ortega, MD. “After a few minutes, she was barely able to breathe on her own.”
A CT scan showed that Toop was having an acute ischemic stroke. A large clot had formed in a damaged blood vessel in her neck. The clot broke free and lodged in an artery on the back of her brain. Blood flow had stopped. The brain stem was faltering. Brain tissue began to die.
“When the brain dies, there’s no turning around,” Ortega says. “Whatever is lost is gone.”
Since 1996, the preferred treatment for ischemic stroke has been intravenous tissue plasminogen activator (tPA), a medication that dissolves clots to restore blood flow. But for some larger clots causing the most severe strokes—like the one Toop had—tPA just doesn’t work consistently. The unopened blockage can cause major brain damage and leave the patient bedridden, dependent on a ventilator, and near death.
Ortega recognized that quick action was necessary to spare Toop that potential outcome. He recommended a procedure called thrombectomy that had only recently been proven as an effective treatment for this kind of acute ischemic stroke. In a thrombectomy, a neurointerventionist—a physician who has received specialized training to perform procedures inside blood vessels in the brain—navigates a catheter through the arteries to remove the clot.
“There was no other choice for her,” Ortega says. “We rushed her into the OR and started the thrombectomy immediately.”
In 34 minutes, Ortega had cleared the blockage and repaired the damaged artery that was the source of the clot. Three days later, Toop was discharged from the hospital.
“We definitely felt like we saved a life,” Ortega says. “It was like a miracle.”
As a nationally recognized Comprehensive Stroke Center, UI Hospitals and Clinics is the only hospital in Iowa that offers neuroendovascular therapy for stroke. When Toop needed a thrombectomy, two neurointerventionists were on staff—Ortega and neurosurgeon David Hasan, MD (’06 R). They shared on-call duties around the clock to ensure that the procedure could be performed whenever necessary.
Two months later, in June 2015, the American Heart Association (AHA) released new guidelines for stroke care, giving the highest level of recommendation for thrombectomy as a treatment for patients with a clot that is blocking a large artery in the brain. The AHA called the procedure “the first new evidence in 20 years that a new treatment can help people having a stroke.”
The time was right for UI Hospitals and Clinics to expand its capabilities so that this type of advanced care would be available to as many Iowans as possible.
‘Time is brain’ treatment
The vice chair of the AHA writing group that issued the new stroke care guidelines is Colin P. Derdeyn, MD, an interventional neuroradiologist, past president of the Society of NeuroInterventional Surgery, and chair of the AHA’s Stroke Council. In December 2015, he joined the UI Carver College of Medicine as chair and department executive officer of radiology.
Derdeyn knows that a breakthrough therapy as promising as thrombectomy couldn’t have come to fruition without advances in processes, research, and technology that go back two decades.
“The first therapy that was ever shown to help somebody with a blocked artery in the brain—which is the vast majority of all strokes—was intravenous tPA,” Derdeyn says. “If you took 100 people off the street with strokes, about 30 percent of them would probably improve back to normal or near normal, just because of good luck or natural processes. If you give them all tPA, that goes up to about 40 percent. So it definitely helps.”
The improvement in outcomes was just one component of the success story that followed tPA’s approval by the Food and Drug Administration in 1996. Another was the profound change it helped to initiate in the speed of delivery of stroke care. For tPA to work, it needs to be administered within 4.5 hours of the onset of stroke symptoms.
“Over the last 20 years, the development of systems to make certain that patients are eligible to get tPA has really exploded,” Derdeyn says. “The University of Iowa, under the leadership of Drs. Harold Adams and Enrique Leira, has been at the forefront of making this process work for stroke patients throughout Iowa.”
Until the 1990s, stroke treatment was not always an emergency procedure, and often the treatment dealt with disabilities caused by stroke rather than the stroke itself.
But with the advent of tPA, outreach campaigns conducted by organizations such as the AHA began to stress the “time is brain” approach to stroke care, emphasizing the importance of early detection and expeditious delivery of the clot-busting drug. The Joint Commission developed a certification program to recognize Acute Stroke-Ready Hospitals, Primary Stroke Centers, and Comprehensive Stroke Centers.
The result was that professionals all along the path of urgent care—including first responders, community physicians, and emergency staff at community hospitals—had a framework for handling stroke cases with maximum efficiency.
At the same time, better imaging technology has enabled rapid and more precise diagnoses, while tele-stroke services extend the expertise of neurologists at Comprehensive Stroke Centers like UI Hospitals and Clinics to providers in remote locations.
Capturing, removing a clot
Physicians have been performing procedures inside the arteries of the brain for many years. Since the 1980s, radiological interventionists have been trained in neuroendovascular techniques, and endarterectomy—the removal of plaque from the carotid artery as a means of stroke prevention—has existed for decades. But before thrombectomy, no treatment for severe stroke could quickly reopen blood vessels in the hours immediately following onset.
“If you take 100 patients who have a large vessel occlusion and you don’t do anything, about 10 or 20 percent of them would make a good recovery on their own,” Derdeyn says. “If you get the blood vessel open within six hours of stroke onset, about 50 or 60 percent make a good recovery, like Mailis did. It’s enormously beneficial.”
Early devices for stroke intervention could reach clots but couldn’t always remove them, or they didn’t open the blood vessel thoroughly or quickly enough to make a difference. There was no scientific evidence to show that intervention resulted in better outcomes than medication.
Two key technological advances changed the landscape. One was the development of a stent-like device called a stentriever, which is a small, collapsible wire cage that can be expanded at the site of the clot to capture it more securely than previous devices could.
The second advance was the improvement of catheters to provide more suction during a procedure. A stentriever procedure requires suction to temporarily reverse blood flow, preventing the clot from being washed out of the stentriever. Derdeyn says new, large-bore catheters have such effective suction that they can actually be used on their own to draw out a clot, without the need for a stentriever.
In late 2014 and early 2015, the results of multiple clinical trials tipped the balance. When used along with tPA, these new clot-grabbing devices were shown to be more effective than tPA alone.
“Those trials came back extremely positive for intervention,” Derdeyn says. “We thought these devices worked well before, but now we had hard evidence that they’re dramatically effective. That was really the sea change in the field.”
Deploying the stentriever
Thrombectomy doesn’t work with every incident of stroke, however. On average, the UI team performs the procedure roughly four to seven times a month. Cases are chosen conservatively, using the latest imaging modalities.
“If the CT or the MRI shows that there is already a lot of brain damage, then we decide not to do it,” says UI neurointerventionist Edgar Samaniego, MD. “Even if we can successfully reopen the blood vessel, it’s not going to change the outcome.”
To begin a thrombectomy, a catheter is inserted into the femoral artery and navigated over a steerable wire through the body and into the vasculature of the brain. The interventionist watches the catheter’s real-time progress on a video monitor.
“We’re using fluoroscopy, which means it’s done using X-rays,” Samaniego says. “We use contrast dye so we can see where the artery is and where the catheter is going.”
In a procedure using a stentriever, the interventionist moves the catheter into the brain and then advances a smaller catheter, called a microcatheter, through the larger, guiding catheter, and into the clot.
“First we need to cross the clot with the wire, which will guide the microcatheter into place,” Samaniego says.
The wire is then withdrawn and replaced by the stentriever, which is advanced within the microcatheter until it is positioned in the occluded, or blocked, section of the brain vessel. The microcatheter is then pulled out of the clot while the stentriever remains in place. As the microcatheter retreats, the stentriever begins to expand, slowly enmeshing itself in the clot around it.
“We let it rest for a little bit,” Samaniego says. “As it expands, it’s going to grab most of the clot.”
The stentriever is then pulled back toward the main catheter. Suction from the main catheter inverts the blood flow to the brain temporarily.
“The blood flow is always going to push the clot more distally into brain vessels,” Samaniego says. “So we’re pulling, pulling, pulling, while suctioning blood away from the brain.”
The stentriever and the clot within it are pulled back through the catheter and out of the body. Another injection of contrast dye shows how much of the clot has been removed. The interventionist may need to go through this process several times to completely restore normal blood flow to the brain.
As in any mechanical procedure, there are risks, Samaniego says. The wire could perforate the brain artery and cause internal bleeding. “But we’re talking about people with major stroke,” he says. “Without attempting this procedure, about 80 percent die or are severely disabled for life. If you put all of that in the balance, most families will opt for the procedure because of how much it increases the chances of a patient having a good outcome.”
A good outcome means the patient will be independent again, either upon discharge or after some rehabilitation. In Toop’s case, that meant walking out of the hospital a few days after a severe, life-threatening stroke. A month later, she was back in school, studying to be a medical assistant. She graduated earlier this year and now works at UI Hospitals and Clinics. In her free time, she runs 5K and 10K races for fun.
“I feel fine,” she says, “like it never happened.”
UI team unique in offering latest stroke therapy
By Tony Craine
After a barrage of new evidence emerged in 2015, neuroendovascular intervention was lauded as the first major advance in stroke treatment in 20 years. Soon after, University of Iowa Hospitals and Clinics moved to bolster its Neuroendovascular Service with additional talent, rededicating its mission.
Physicians with neuroendovascular training specialize in “navigating catheters into the vessels of the brain for many different purposes,” says Colin P. Derdeyn, MD, who leads the service. “We have a large number of tools we can use through these catheters to open blockages, like in ischemic stroke, and also to block flow to things that can cause bleeding in the brain, like brain aneurysms or other malformations.”
The service now boasts six fellowship-trained neurointerventionists who represent four departments—Derdeyn and Minako Hayakawa, MD, radiology; Santiago Ortega, MD, and Edgar Samaniego, MD, neurology; David Hasan, MD (’06 R), neurosurgery; and James Rossen, MD, cardiology.
“We have a uniquely large and integrated neuroendovascular program,” Derdeyn says. “The six of us rotate, share coverage on call, and participate in regular case conferences. Our diverse backgrounds give us many complementary skills and perspectives on the diseases we treat.
“All of this adds up to a great opportunity to move forward in terms of better clinical care and advancing research and education,” says Derdeyn, adding that the UI offers a training program for neurointerventionists.
Among the challenges the team will tackle, process improvement is a top priority. That includes building on existing processes that have developed as intervention techniques and technology have improved.
“Since 2014, the UI has worked hard on developing an acute endovascular protocol and infrastructure to expedite the assessment and treatment of patients,” Ortega says. “Many people have been involved in this process, including EMS personnel, ER physicians and nurses, radiology techs, neurologists, anesthesiologists, OR nurses, and neurointerventionists. As a result, we can treat the majority of patients within 60 minutes of arriving at the hospital.”
The goal is to make sure the service—the only one of its kind in Iowa— is ready to serve people from all over the state in a timely manner.
“Outcomes are so time-dependent,” Derdeyn says. “The faster you get the blood vessel open, the more likely you have a better outcome.”
Watch a video to see how a stentriever clears a blockage to restore blood flow to the brain.