Background: CT angiography (CTA) has become the predominant mode of imaging selection prior to endovascular stroke therapy. The added value of CTA collaterals beyond ASPECTS and validation with digital subtraction angiography (DSA) remain unaddressed. We determined the impact and validity of CTA collateral grade with DSA in the multicenter TREVO and TREVO 2 trials.
Methods: Pooled analyses of the TREVO and TREVO 2 CTA dataset prior to endovascular therapy were conducted. CTA collaterals were scored (0-20) with the regional leptomeningeal collateral score (rLMC) and directly compared with the ASITN/SIR (0-4) collateral grade. Statistical analyses included descriptive statistics and Spearman correlation analysis among CTA, DSA collaterals and ASPECTS. Logistic regression analysis was used to model 90-day good outcome and revascularization success.
Results: CTA and DSA collaterals were compared in 116 subjects with anterior circulation occlusions. ASPECTS was median 8 (range 3-10; 49% 0-7 versus 51% 8-10), with CTA collaterals on rLMC score of median 16 (range 4-20) and DSA collaterals median 2 (range 1-4; 13% grade 1, 50% grade 2, 26% grade 3 and 11% grade 4). ASPECTS exhibited only moderate correlation with collaterals at CTA (ρ=0.35, p<0.001) and DSA (ρ=0.41, p<0.001). Similarly, only moderate correlation was noted between CTA collaterals and DSA (ρ=0.43, p<0.001). Baseline ASPECTS better predicted (OR 1.50 95%CI [1.08-2.09], p=0.017) good clinical outcome (90-day mRS 0-2) compared to CTA collaterals (OR 1.10 95%CI [1.00-1.22], p=0.058), whereas DSA collaterals were most predictive (OR 1.99 95%CI [1.20-3.29], p=0.008). Multivariate logistic regression revealed DSA collateral grade 3 or greater as paramount for achieving good outcomes (OR 3.00 95%CI [1.31-6.89], p=0.01).
Conclusions: Single-phase CTA collateral scoring prior to endovascular therapy provides marginal value beyond ASPECTS and limited correlation with the extent of collaterals on DSA. CTA of collaterals may perform differently at very high ASPECTS or with further development of imaging acquisition or post-processing techniques.