Endovascular treatment trials underscore CT imaging’s value

Several late-breaking clinical trials at the 2015 American Stroke Association conference raised hope that device-based endovascular treatment improved outcomes in patients with ischemic stroke. For imagers, the results also raised questions about their role going forward.

Bijoy K. Menon, MD, MSc, of the Foothills Medical Institute in Calgary, Alberta, and colleagues revisited the trials MR CLEAN (Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands), ESCAPE (Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion With Emphasis on Minimizing CT to Recanalization Times), EXTEND-IA (Extending the Time for Thrombolysis in Emergency Neurological Deficits-Intra- Arterial) and SWIFT PRIME (Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment) in an article published in the June issue of Stroke. Some of the trials were featured at the 2015 stroke conference.

Each trial used CT angiography (CTA) in its patient selection to varying degrees, and each showed the efficacy of endovascular therapy compared with standard care. “These trials focused on efficiently integrating advanced CT imaging within the stroke workflow by developing and using imaging techniques that are quick, reliable, and available all hours of the day,” they observed.

That begged the questions: Should these tools be used in the general population, and if so, which ones and how to implement them into practice?

CTA identified patients with proximal anterior circulation occlusion in each of the studies. It provided high-resolution images that pinpointed thrombus location and size and helped the physician choose the proper tools and techniques.

It also can be used to assess the patient’s collateral status; in the case of ESCAPE, multiphase CTA (mCTA) was employed in most cases, which improved the accuracy of noncontrast CT when assessing the extent of early ischemic changes based on the Alberta Stroke Program Early CT Score. Noncontrast CT helps to rule out hemorrhage.

“With appropriate education and training in the use of mCTA along with a focus on speed, the major clinical benefit (absolute reduction in disability of 25%) in the ESCAPE trial may potentially be applicable to the broader population of ischemic stroke patients with proximal large vessel occlusion,” they wrote.

EXTEND-IA and SWIFT PRIME included CT perfusion, which has been criticized for potentially adding time to the process. The trials relied on automated software to create efficiencies and remove human variability. Menon et al supported the use of mCTA and CT perfusion but added that centers need to provide training in the techniques and interpretation of images.

The authors called for standardization in imaging quality and protocols, and pointed to equipment, scanner setup, patient factors, imaging processes and physician factors as potential weak links in CT quality. The various trials showed that quality assessment, education, training and automation could fix some of the problems.

“Going into the future, we collectively will need to decide whether we favor a more selective strategy (acknowledging that patients who may benefit may not get the treatment) or a more inclusive strategy that takes many more patients for endovascular treatment (leading to greater numbers of futile recanalization),” Menon et al proposed.