Karen Hwang is back at work as a chiropractor after undergoing endovascular treatment at Sunnybrook.
A groundbreaking clot-removal procedure is saving the lives of stroke victims who were previously hard to treat
When Karen Hwang turned 40 last fall, she and her best friend, who was also turning 40, decided to celebrate their birthdays by travelling to Athens to run a marathon. Less than two weeks after the avid runner returned home, she collapsed in the shower of her Markham, Ont., home on a Friday evening. Karen's family called 911, and Karen was rushed to a nearby hospital.
At first, the doctors assumed that Karen had slipped and struck her head. "Given my age and history, there was no reason to suspect a stroke," she says. "I was perfectly healthy, with no family history of stroke."
An initial CT scan showed nothing, and her only obvious injury was a badly bruised shin. When Karen regained consciousness the next day, she seemed perfectly fine. But on Sunday morning, a nurse became suspicious when she tried to assist Karen to the bathroom and noticed her right leg and arm were bent, and that she was unable to straighten them. At that point, Karen discovered she could no longer walk.
My symptoms were bilateral, so I had a lot of weakness on my right side and numbness on my left side, including my mouth and tongue. Luckily, it didn't affect my speech. I had also lost some of the vision in my left eye," says Karen.
A second CT scan followed that morning, and this time revealed a blood clot lodged in the basilar artery, a major artery that channels blood and oxygen to a number of arteries that branch out into the brain. Karen had an ischemic stroke, a stroke that is the result of a blood clot.
It was Sunday afternoon, and she was rushed to Sunnybrook. When the call came, Dr. David Gladstone, medical director of the Regional Stroke Prevention Clinic, made the diagnosis, co-ordinated her treatment plan and mobilized the Code Stroke team – Karen would undergo emergency surgery to try to remove the clot.
The kind of clot Karen had is challenging to dissolve or manually remove at the best of times, but many hours had already passed since she collapsed. Survival and recovery after an ischemic stroke depend heavily on how quickly the clot can be removed. Typically, the prognosis would be bleak, including a vegetative state and, possibly, even death. But Sunnybrook doctors had an ace up their sleeve – a clot-retrieval procedure known as endovascular treatment (ET).
ET is a minimally invasive procedure that involves the expeditious removal of a blood clot, thereby restoring normal blood flow to the brain. "First we perform a CAT scan to see how much of the brain is savable, locate the blood clot and decide if we can get up to it and examine collateral blood flow [blood flow in the area surrounding the clot] using advanced imaging," explains Dr. Rick Swartz, medical director of the stroke program at Sunnybrook, who's been leading studies of the technique at Sunnybrook. "Then we put a wire in through the groin and move up into the brain, where we put it into the clot and deploy a stent, which meshes with the clot, then retrieves it."
Researchers at Sunnybrook have been working hard with collaborators around the world to troubleshoot and fine-tune ET techniques, which have been in studies for almost two decades. What has developed is a solution that may drastically change the prognosis for patients with ischemic strokes. An ischemic stroke is caused by a blood clot that cuts off blood flow to some part of the brain. Ischemic strokes make up about 85 per cent of stroke cases.
The ET procedure is being hailed as the most significant breakthrough in stroke treatment in 20 years, since it can greatly reduce disability and risk of death.
Sunnybrook was one of 22 sites worldwide participating in a clinical trial that involved 316 ischemic stroke patients who were randomly assigned to either standard care (a clot-busting drug called tPA, short for tissue plasminogen activator) or standard care, plus the clot-retrieval process. Results, published in The New England Journal of Medicine in March 2015, showed that 55 per cent of patients had a positive outcome, compared with 30 per cent for those receiving standard care. Death outcomes were cut in half, from 20 per cent to 10 per cent. In fact, the trial was ended early due to the overwhelming success rate shown in results, says Dr. Swartz, one of the study's co-authors.
An ischemic stroke can be treated with tPA to dissolve clots, but some challenges arise, says Dr. Swartz. A key issue is that tPA needs to be administered to a patient within about 4.5 hours of having a stroke. So people need to quickly recognize stroke symptoms and call 911 right away, but that doesn't always happen. People who take blood thinners aren't eligible for tPA, since the drug is a blood thinner, so it would increase the bleeding risk.
Another potential issue is that tPA may not completely remove large blood clots, so surgeons may still need to manually remove what's left of a partially dissolved clot. Many patients in the clinical trial received both tPA and ET. "tPA works quite well for some patients," says Dr. Swartz. "For this trial, we were looking at the most severe strokes that affect the big blood vessel branches that go into the brain," he says. "These tend to have larger, longer clots, so tPA may dissolve half of the clot, but if the other half is still blocking blood flow, you haven't addressed anything until you get rid of all of it." That's where the ET procedure comes in – to mechanically remove clots that are less responsive to tPA.
ET has a longer window of opportunity than tPA – generally up to six hours and sometimes even longer – but only if the damage hasn't already been done. So people cannot delay getting to the hospital, warns Dr. Swartz: "It means that now people have even more reason to get to the hospital quickly – we have more options for the worst strokes." ET can certainly be an option for patients who aren't candidates for tPA or for whom the clot-busting drug hasn't been completely successful.
Dr. Victor Yang, a neurosurgeon at Sunnybrook who performs the clot-removal procedure and has developed processes to make ET as efficient as possible, says that other options are still available for stroke patients who aren't candidates for ET, but for those who are eligible, the decision is clear. "There are emergency devices available, but this is older technology. The other alternative uses catheter tubes to disrupt and suction the broken-up clot," he says. "It's tedious to use, and it takes a longer time with unpredictable results; the success rate is only about 30 per cent," adds Dr. Yang.
As for ET's breakthrough in stroke treatments, it's not just about the technique, but also about teamwork, says Dr. Yang. "Technology is just one piece. Stroke treatment is now what we call a 'team sport.' If you have the technology, but it takes hours to assemble a team, the technology will be of no benefit to the patient," he says.
Dr. Swartz emphasizes speed as one key factor that has made ET a real game-changer for stroke treatment. "We've built our system to be faster in responding to stroke patients," says Dr. Swartz. "Candidates for ET can be identified and treated as quickly as possible, thanks to advanced imaging technology. Another factor is that the latest-
generation devices, known as stent retrievers, are much faster, safer and more effective."
Meanwhile, Dr. Yang has also been designing and developing an app that provides a communication tool for all key members involved. Michael Lu, a process improvement engineer working with the stroke team, wrote the app software. Initially, Lu tracked the team's response time from the stroke event to when the patient shows up in the ER to when they have an intervention. Now the app keeps an automatic "score board" for the team.
For Karen Hwang, the convergence of technological innovation with the interdisciplinary collaboration and resourcefulness of Sunnybrook's team has made a life-saving – and brain-saving – difference.
"If it weren't for what doctors Yang, Howard and Gladstone did, and the speed at which they did it, I would not be here today," says Karen. "My recovery has been remarkable, knowing the consequences of the type of stroke I had."
Karen is now back to work part-time as a chiropractor, steadily regaining her indispensable fine motor skills, including the use of her right hand. She's also slowly working up to running again, and she is planning to participate in a five-kilometre run this fall. "I still feel like I have a long way to go, but things just keep improving each day."
This content was produced by The Globe and Mail's advertising department, in consultation with Sunnybrook. The Globe's editorial department was not involved in its creation.