Key Points:
- Prospective study assesses interplay between collateral grade, endovascular stroke therapy outcomes
- Higher collateral grade associated with better outcomes
High collateral grade is associated with multiple improved outcome measures among patients undergoing endovascular repair of acute cerebral ischemia, according to research published in the January 2016 issue of the Journal of NeuroInterventional Surgery. These findings suggest collateral grade may play a role in patient selection for endovascular therapy.
Sunil A. Sheth, MD, of the University of California, Los Angeles, (Los Angeles, CA), and colleagues prospectively collected demographic, clinical, laboratory, and radiographic data on 117 consecutive patients who received endovascular therapy for acute cerebral ischemia at a single tertiary referral center between September 2004 and August 2010.
Higher collateral grade on angiography at presentation, as assessed by the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology grading scheme, was associated with a trend toward better reperfusion after endovascular intervention (53% vs 41% TICI 2b/3; P = .12) as well as significant advantages with regards to a decreased rate of post-procedural hemorrhage, smaller infarct size at discharge, and higher modified Rankin Scale (mRS) score at discharge and 90 days (table 1)
Patients who were matched by vessel occlusion, age, and time of onset had smaller strokes on presentation as well as better functional and radiographic outcomes if they had superior collateral flow. On multivariate analysis, collateral grade 0-2 independently predicted an National Institutes of Health Stroke Scale (NIHSS) score ≥18 (adjusted OR 4.37; 95% CI 1.75-10.95).
An Earlier Era of Care But Still ‘Valid’
“The main reason we did not include patients after 2010 is that our treatment protocol changed, and we stopped doing complete diagnostic angiograms (with injection of the other carotid and vertebral artery) prior to thrombectomy,” Dr. Sheth explained in an email to WLNCMD. “After 2010, we started going straight for the clot. While this new approach lead to faster recanalizations, it also meant we no longer had complete imaging to make accurate assessments of collaterals.”
While Dr. Sheth acknowledged that tools and techniques evolved considerably after 2010, he does not think that is relevant to the findings. “The focus of our paper is not on recanalization rates/techniques, but on the physiology of collaterals in determining initial stroke severity and ultimate outcome,” he said. “As such, the conclusions about the influence of collaterals on NIHSS and infarct volume remain valid.”
Getting to the Root Cause
While it is known that patients with larger strokes do worse after treatment, even with full perfusion, the question is why certain patients have larger initial infarct volume to begin with, Dr. Seth observed. “From a physiological point of view, there are 3 main factors: the location of the occlusion (with a more proximal occlusion being worse), duration of the occlusion (the longer the worse), and the extent of the collaterals.”
The current study shows that, when patients are well-matched for other factors, “differences in collateral grade alone lead to differences in initial stroke severity and ultimate clinical outcome, Dr. Seth explained.
“I think many of the arguments against collaterals as causative of good outcomes draw the line between cause and effect differently,” he continued. “They draw the line after the measures of initial stroke severity. But this initial severity is not random. On the contrary, it's determined in large part by the collateral status.”
How best to select patients for endovascular therapy is still an “open” question in the field, he added. “Collaterals clearly play an important role: 4 of the 5 recent trials used some form of collateral imaging as a part of their selection criteria. Moving forward, these assessments are going to be primarily noninvasive (CTA, CT perfusion, and MRI perfusion), but the idea is the same.”
Source:
Sheth SA, Sanossian N, Hao Q, et al. Collateral flow as causative of good outcomes in endovascular stroke therapy. J NeuroInterv Surg. 2016;8:2-7.
Disclosures:
- Dr. Sheth reports no relevant conflicts of interest.
- The University of California has patent rights in retrieval devices for stroke.
