Richard Jackson, MD
Now that endovascular thrombectomy has been shown to be beneficial in large vessel occlusions, there is a question of distribution of resources and triage of patients. Yoo et al. recognized this need and began to look at a possible imaging biomarker for response to IV-tPA.
They began with a retrospective analysis of a CT-based thrombus cohort of 214 patients from three university hospitals between 2006 and 2009. Mean thrombus volume was found to be 129mm3 and density 53.5 HU with a median time to tPA of 52 minutes. Of the 214 patients, 162 (76%) failed to re-canalize, which was defined as TICI grade 1-2a. Using statistical analysis, the upper range of the calculated reference range was 181.9 mm3 thrombus volume, and, therefore, a cut-off volume of 200mm3 was determined to be optimal to predict non-recanalization.
A prospective validation cohort of 78 patients with similar thrombus and IV-tPA time characteristics were analyzed. None of the patients with a thrombus volume greater than 200mm3 re-canalized with a PPV of 100 and NPV of 23. Volume was found to have a higher sensitivity and accuracy than length, and density was not significant in contrast to previous studies.
This finding is hypothesis-generating, and an imaging biomarker could be a useful adjunct for decision-making in the future if validated. Possible limitations include difficulty in calculating volume due to the requirement for CTA with MIP alongside non-contrast head CT.