By Bob Marshall, Chief Editor, Med Device Online
What happens when a major ischemic stroke is misdiagnosed as minor at the initial point of care by an emergency medical professional in the field? The clock starts ticking as the patient is taken to a primary care center (a regular hospital). The medical team at the hospital will evaluate the type of stroke and the areas of the brain affected to determine the most appropriate course of treatment (tick, tick, tick…).
The medical team will seek to rule out other possible causes of the patient’s symptoms, such as a brain tumor or a drug reaction (tick, tick, tick…). Various tools may be used to determine the patient’s condition, including a physical examination, blood tests, computerized tomography (CT) scan, and magnetic resonance imaging (MRI), among others (tick, tick, tick...).
If the diagnosis is a minor neurovascular occlusion, doctors will seek to quickly restore blood flow to the affected area(s) of the brain using systemic thrombolytic agents. The gold standard clot-busting drug, tissue plasminogen activator (tPA), also known as alteplase, typically is effective if given within three hours of the onset of symptoms. Quick treatment not only improves the chance of survival, but also may reduce complications.
But, some blood clots are resistant to enzymatic degradation, so tPA may not be effective on these (typically larger) occlusions. If that is the case, a thrombectomy capable hospital is required (tick, tick, tick…). The patient must be transported to a center with advanced imaging capabilities, as well as medical professionals skilled in neurovascular surgery and mechanical thrombectomy. So, doctors at the comprehensive stroke care center prepare to intervene and await the patient’s arrival (tick, tick, tick…).
Finally, this patient is in the correct place for the mechanical thrombectomy treatment they need. But wait — how much time has passed since the onset of symptoms? The 2015 American Heart Association/American Stroke Association (AHA/ASA) guidelines for early management of patients with acute ischemic stroke stipulated that patients were eligible for endovascular therapy with a stent retriever (mechanical thrombectomy) within six hours of stroke onset. What if it had been longer than six hours? Following these guidelines meant that some stroke patients would progress until all the brain tissue surrounding the affected arteries was dead, leaving them to struggle through the rehabilitation process, and likely have a life marked by significant disability.
But all of this has changed in 2018. The AHA/ASA issued new guidelines in January for the management of acute stroke. The updated guidelines allow for patients to receive mechanical endovascular thrombectomy up to 24 hours after a stroke. Additionally, the FDA in February expanded the indication for Stryker’s Trevo stent retriever as a front-line treatment for patients experiencing acute ischemic stroke up to 24 hours from symptom onset. This expansion of the treatment window has the potential to reduce disability and improve quality of life for tens of thousands of additional stroke patients each year.
I discussed Trevo’s expanded indication with Mark O’Brien, VP/GM of Global Commercialization, and John Allison, VP Regulatory & Clinical Affairs, both with Stryker's Neurovascular division. Allison provided some background on the stroke space and the evolution of the Trevo device.
“The stroke space, specifically for medical devices, is still very fertile. About a year and a half ago we got the first clinical indication for… our Trevo stent retriever. Prior to it, we had a thrombectomy indication,” Allison said. “That indication was more tool-like, similar to tools used in surgery. The approval of Trevo with a clinical indication was not just about pulling that clot out any more; it was based on an improvement in the patient’s neuro presentation. Patients were assessed by a neurologist pre- and post-procedure to determine the amount of improvement they’d had. So, a year and a half ago we had the first device approved for a clinical improvement in the patient as a result of the treatment. That speaks to how immature this space is.”
I asked O’Brien about the expense and effort of a trial to blaze the trail for a new device indication, which opens the door for others to follow. Is it really worth it?
“That’s important to us, as we’ve tried to be a pioneer in the space. Our customers appreciate the fact that we are opening up new areas to treat patients,” O’Brien explained. “We are committed to answering scientific questions, not always for commercial reasons, but sometimes just to move the space forward, even though it may make it easier for some of our competitors to follow. We will strive to answer scientific questions and then battle for market share in the labs, the way we traditionally do. This space seems to value that and respond to it. To us, it’s a real advantage to be the first to market.”
We have all come to understand that time is very critical in the initial treatment of stroke patients, but how important is this expansion of the treatment window to 24 hours? How big is the market for a device with this expanded indication?
“This area has been underserved, because there has been the belief that patients can only be served in the zero-to-six- or zero-to-eight-hour timeframes. This is going to open the door up for a lot more treatment,” Allison responded. “There are numbers out there, including Europe and the U.S., indicating anywhere from 42 to 59 percent of ischemic stroke patients have large vessel occlusions — meaning they have a large clot upon arriving at the hospital. So, roughly 50 percent of the current stroke patient population could benefit from this larger treatment time window. That is a huge opportunity.”