Building evidence
The published results of five recent endovascular stroke treatment trials have ushered in a new era in stroke therapy. For the first time, endovascular stroke therapy was shown to improve outcomes compared to standard therapy when used early (essentially within 6–8 hours of onset) in the setting of large vessel ischemic stroke. The trial results of MR CLEAN, ESCAPE, EXTEND IA, SWIFT PRIME and REVASCAT are unusual in their consistency and robust treatment effect. These trials were not limited to a few sites in any single country, nor did they use a single protocol. The devices and processes were robust enough to ring true through Europe, North America and Australia.
The SWIFT PRIME and ESCAPE trials pushed the envelope of the results that can be achieved if patient selection and streamlined interventions are optimized. CTA and/or CT perfusion imaging were used in the vast majority of these cases to select patients with intracranial ICA or M1 occlusions and a small core infarct or robust collaterals. The odds ratio (OR) for improvement at 90 days on the modified Rankin scale was 2.6 in ESCAPE and 2.8 in SWIFT PRIME. Absolute improvements over standard therapy in outcomes measuring functional independence at 90 days were 27 percent and 25 percent, respectively. EXTEND IA was a very small trial that looked at functional outcomes only as a secondary endpoint but it too was strongly positive (OR of 2.0).
The MR CLEAN and REVASCAT trials represent a more practical assessment of the likely treatment effect of the current devices when used with conventional imaging and a more varied patient mix. Noncontrast head CT and standard CTA were used but no rigorous perfusion imaging was employed to select patients. Patients with intracranial occlusions of the ICA, ACA (MR CLEAN only), MCA and any associated cervical carotid stenoses were treated. The ORs of improvement in outcome at 90 days on mRS were about 1.7 (the same as tPA demonstrated in the pivotal NINDS Stroke trials parts 1 and 2 published in 1995) and the absolute improvement in functional independence at 90 days was about 15 percent.
These results contrast starkly with the publication of three purportedly neutral studies of endovascular treatment just two years prior. Although IMS III, the most pertinent of the studies, did not find significant improvement with respect to its primary outcome measure, there were no safety issues identified and those patients with documented large vessel occlusion did significantly better with endovascular treatment than with IV tPA alone, even with prior generation devices and procedures. Stent-retrievers overwhelmingly outperformed the Merci devices in their FDA approval trials in terms of both patient outcomes and vessel recanalization but were not significantly used in IMS III. So while there was room for optimism regarding newer trials, the field was surprised by the rapidity and magnitude with which the tide turned.
Difficult delivery
As history has shown, delivering these therapies to all who need it will prove difficult. Twenty years ago there were no effective options for the treatment of acute stroke. Then the NINDS Stroke trial demonstrated improved outcomes for stroke patients treated within three hours of symptom onset using IV tPA. This led to FDA approval of IV tPA for the treatment of acute stroke. It would be a number of years before systems of care (and physician acceptance) caught up with the potential of IV tPA and significant increases in rate of treatments occurred.
There is now near universal interest by hospitals and hospital systems to provide stroke care similar to the recent trials and improve stroke outcomes to their patient populations. These systems already have a mindset of treating acute stroke in a rapid fashion, which will need to be tweaked but not reinvented. The real challenge of delivering stroke treatment in the mode of acute coronary interventions will be the organization of the manpower necessary to do so on weekends, nights and holidays.
The participating sites in the recent trials were for the most part not community hospitals and not new to endovascular stroke therapy. Making endovascular stroke intervention as accessible as acute coronary intervention will require large numbers of endovascular interventionists thus necessitating several specialties and, in some cases, differing hospital systems to cooperate. It will not be professionally or financially viable otherwise.
A golden opportunity …
Unlike cardiology, in which the case volumes and practice patterns allow multiple cardiologists to practice within modest-sized communities, the maladies amenable to endovascular treatment in the head, neck and spine are relatively few. The number of endovascular neurosurgeons, interventional neuroradiologists and interventional neurologists who are needed to treat all the aneurysms, fistulae and AVMs already exist. In truth, one of the yearly discussion topics at annual meeting of the Society of Neurointerventional Surgeons (SNIS) is whether and how to limit additional trainees so that sufficient case volumes exist to maintain minimum skills of existing practitioners.
Despite the abundance of interventional physicians to perform elective neurointerventional procedures, there are too few physicians available to treat hyper-emergent stroke patients. In reality, there is incredible competition for these cases. Hospitals occupying the same city block but in different health systems each want their own specialists. This makes sustainable, instantaneous endovascular stroke coverage difficult for most hospitals unless physician resources are used to best advantage (possibly combined and shared).
Large vessel ischemic strokes with imaging features suggestive of a small core infarct or robust collaterals are a relatively small subset of acute ischemic strokes. Simply stated, there are not enough patients who would benefit from endovascular stroke therapy for a single physician to make a career of endovascular stroke treatment. At the same time, it is unreasonable to expect a single physician to be able to provide this type of care around the clock, 365 days a year. At a bare minimum, it will likely require at least three physicians working together to provide a sustainable level of coverage in any geographical area.
…your opportunity
Interventional radiologists are on staff at nearly all hospitals and a substantial number are already involved in emergency stroke treatment. This is especially true in nonacademic hospitals and nonurban areas. Many of those not currently engaged in stroke treatment possess the expertise in both stroke neuroimaging and cervicocerebral vascular access to supplement the pool of physicians currently providing endovascular stroke treatment.
There is now near universal interest by hospitals and hospital systems to provide stroke care similar to the recent trials and improve stroke outcomes to their patient populations.
The efficacy of the current generation of stroke devices when used early in large vessel stroke should no longer be questioned. The methods and workforce used to deliver the care will be. In nearly all foreseeable models of delivering this treatment to patients there will be a need for additional manpower to deliver expert endovascular stroke care. Interventional radiologists have been and will be asked to participate in stroke call and SIR will provide quality instruction in the methods and techniques necessary to achieve excellent outcomes for stroke patients.
Prior to publication of IMS III, SIR and the IR community laid the groundwork by participating in development of training standards, multisociety quality guidelines and creating the CLOTS course with a comprehensive set of educational materials for physicians performing endovascular stroke therapy. The society is taking a leadership role in providing training to interventional radiologists committed to endovascular stroke therapy by establishing the Contemporary Endovascular Stroke Therapy (CEST) course as an educational track in conjunction with the SIR 2016 Annual Scientific Meeting (April 2–7, 2016, Vancouver, B.C.). This updated course will build on CLOTS to provide interventional radiologists with experience in endovascular therapy and cerebral angiography, the most current updates on endovascular stroke therapy with emphasis ranging from imaging and patient selection to endovascular treatment and patient management.
We encourage all SIR members to mark your calendars for this important course, and to take advantage of critical opportunity in our field.
