"The most critical feature is to treat the patients as soon as possible when they arrive in the emergency department, perhaps within 90 minutes. I think that’s the best chance for recovery. We are nowhere near what’s being done in cardiology, where there are door-to-balloon times of an hour. We need to do that in stroke. Since we’re dealing with an organ that’s more sensitive than the heart to ischemia, we probably need to be even faster than what’s being done in cardiology. There is definitely room for improvement in our systems, perhaps by having the endovascular team stay in the hospital. Expense will be the limitation," according to Dr. Silver, director of the stroke center at Brown University, Providence, R.I.
ISM III investigator and interventional neuroradiologist Dr. Thomas A. Tomsick said in an interview that the study results won’t change his own clinical practice.
"ISM III is by no means the final word on combined therapy. In Cincinnati tomorrow, if a patient with a large NIH Stroke Severity score shows up and we’re treating him with IV TPA at 2 hours from stroke onset, we’re not going to do a CT angiogram to evaluate that patient. He’s going to the cath lab for angiography to see if there’s a clot suitable for endovascular therapy," said Dr. Tomsick, professor of radiology at the University of Cincinnati.
Five different endovascular device therapies were utilized in IMS III. As new devices reached clinical practice, their use was allowed by investigators in order to keep the randomized trial clinically relevant. But recruitment for the study was slow because so many clinicians were already convinced by anecdotal experience that combined therapy is better. So the endovascular therapies used most frequently in IMS III aren’t the ones widely used in clinical practice today. Major new randomized trials are now getting underway comparing combined therapy using state-of-the-art, more effective stent clot retriever devices to intravenous TPA alone, he added.
In the New England Journal of Medicine report, the authors noted that "the use of randomization in ongoing and future stroke trials, rather than the treatment of eligible patients with endovascular therapy outside any trial, and minimization of the time to treatment will be essential for assessing the potential benefit of endovascular therapy for acute ischemic stroke."
No matter how future trials of combined therapy turn out, endovascular therapy is not going away, Dr. Broderick observed.
"It’s a very good tool. The reason why is there are patients who can’t get TPA. For example, roughly 5% of patients who undergo coronary artery bypass surgery have a stroke. If you have somebody with a big stroke 2 days after having their chest cracked, you can’t use TPA. In that case, those endovascular devices are the way we can get up in there and get rid of the clot," he explained.
In an editorial accompanying the report in the New England Journal of Medicine (doi:10.1056/NEJMe1215730), Dr. Marc I. Chimowitz declared that the clinical implication of IMS III is that endovascular therapy remains unproven and IV-tPA should continue to be the first-line treatment for patients with acute ischemic stroke within 4.5 hours after stroke onset.
While new clinical trials featuring more effective IV clot busters, such as tenecteplase, and next-generation endovascular devices are urgently needed in an effort to improve stroke outcomes, patient recruitment is likely to continue to be a challenge in the current environment. This could be overcome if Medicare were to place a moratorium on reimbursement for endovascular therapy of acute ischemic stroke except as part of a randomized trial, according to Dr. Chimowitz, professor of neurology at the Medical University of South Carolina, Charleston.
The study was supported with grants from NIH and the National Institute of Neurological Disorders and Stroke; and by Genentech (which supplied the TPA); and EKOS, Concentric Medical, and Cordis Neurovascular (which supplied catheters); and Actilyse (alteplase) manufacturer Boehringer Ingelheim (which, along with Genentech and EKOS, provided support for investigator meetings). Dr. Broderick disclosed consulting fees from PhotoThera. Of the 28 other authors, disclosures for 14 were listed and included having received consulting fees, grant support, and/or lecture fees from a variety of device and pharmaceutical companies that include Genentech. Dr. Chimowitz, Dr. Silver, and Dr. Tomsick reported having no financial conflicts.
* This story was updated February 8, 2013.