Endovascular treatment of Stroke: Historical Perspective

Abstract

Effective acute ischemic stroke therapy hinges on rapid restoration of blood flow to
the ischemic tissue. Since the National Institute of Neurological Diseases and Stroke r-tPA
study,1 intravenous fibrinolytic therapy in appropriately selected patients has been the primary
method used to open the vessels and improve neurological outcome from stroke. The intravenous administration allowed for widespread dissemination of the technique, since therapy
could be started very rapidly after the diagnosis is made. However, successful treatment with
r-tPA requires careful patient selection and adherence to strict inclusion and exclusion criteria.
As a result, there is a significant number of patients who could not receive the therapy. Even
though significantly better than placebo for most stroke patients, some still suffered a poor
outcome in spite of therapy. This raised the question whether there could be a way to directly
apply the fibrinolytic agent to the occlusive thrombus with catheter-based techniques in an effort to more effectively treat large vessel occlusions. Intra-arterial thrombolysis was reported
helpful in restoring flow in relatively small series of patients, especially situations like basilar
thrombosis, with a dire natural history.2 However, only one study, the PROACT study showed
a positive impact on neurological outcome compared to placebo.3
Results of this study were often used to justify endovascular treatment of patients ineligible or unresponsive to intravenous
r-tPA but intra-arterial administration of the fibrinolytic was often unsuccessful restoring flow
in the occluded vessel, and not infrequently was associated with hemorrhagic transformation
of the stroke. The endovascular armamentarium increased in the early years of the 21st century
with the development of the MERCI device (Stryker, Fremont, CA, USA), a cork-screw-like
device designed to mechanically retrieve thrombus.4,5 This resulted in a higher success rate in
opening occluded vessels compared to pharmacological methods and could be used in patients
in whom r-tPA is contraindicated. In the years that followed, additional mechanical thrombectomy devices were introduced including stent-like retrievers like the Solitaire (ev3-Medtronic,
Irvine, CA, USA), and the Trevo (Stryker, Fremont, CA, USA), and the Penumbra aspiration
system (Penumbra, San Leandro, CA, USA) which all appeared to be far more effective than
Merci in opening occluded vessels. The IMS III study sought to provide evidence of the effectiveness of endovascular techniques plus intravenous r-tPA versus intravenous r-tPA alone, but
it enrolled patients when these newer devices were just becoming available. Most endovascular
patients were only treated with intra-arterial r-tPA and, not surprisingly, the study showed no
benefit in outcome.6 This prompted some to predict the death of endovascular stroke therapy.
A short time later, results of well-designed studies beginning with the MR CLEAN study7
appeared in rapid succession showing significantly improved outcome with endovascular treatment of large vessel occlusions using the modern stent-like retrievers.8-11 Within a short period
of time, endovascular therapy went from being on the verge of extinction to being an integral
part of comprehensive stroke care. The future will no doubt see investigations refining patient
selection criteria, evaluating the role of advanced imaging techniques, evolving and improving
the devices and techniques and improving infrastructure to allow all appropriate patients have
access to these devices and the trained physicians that can use them safely and effectively.