Comprehensive Assessment of Arterial, Tissue, and Venous Collaterals for Evaluating the Infarct Growth Rate: The Multimodal Collateral Score.

BACKGROUND

Collaterals are crucial factors that influence the infarct growth rate (IGR). We aimed to determine whether a comprehensive multimodal collateral score (MCS), incorporating collateral assessment at the arterial, tissue, and venous levels, is associated with functional independence and provides incremental prognostic value over individual IGR metrics.

METHODS

Arterial collaterals were assessed using multiphase CT-angiography (mCTA), ranging from 0 to 5; tissue-level collaterals were evaluated on CT-perfusion by the hypoperfusion intensity ratio (HIR), ranging from 0 to 1; and venous outflow was measured on mCTA with the comprehensive venous outflow (CVO) score, ranging from 0 to 8. These metrics were used to develop the multimodal collateral score (MCS), which encompasses good mCTA collaterals (score 4-5), HIR (< 0.4), and CVO (range 4-8). The MCS ranges from 0 to 3, where 0 indicates no favorable collaterals, 1 means only one good collateral metric among the used ones, 2 signifies just two favorable collateral metrics differently combined among the used ones, and 3 represents the sum of all good collateral metrics. Multivariable logistic and ordinal regression analyses identified clinical and radiological factors independently associated with clinical outcomes (modified Rankin scale 0-2 at 90 days, ordinal mRS at 90 days).

RESULTS

Overall, 615 acute ischemic stroke patients treated with thrombectomy within 24 h from symptom onset between January 2017 and December 2023 were included: the median age was 77 [IQR = 67-84], 320 (52%) were females, and 307 (50%) achieved functional independence. The MCS grades of 2 (aOR 2.92 [95% CI = 1.70-5.03]) and 3 (aOR 5.35 [95% CI = 3.03-9.44]) were independently associated with functional independence. The MCS was also independently associated with 90-day ordinal mRS (adjusted common odds ratio [acOR] 1.73 [95% CI = 1.51-2.01] per 1-point increase). The AUC of the MCS for predicting functional independence was 0.71 (95% CI = 0.66-0.75), which was superior to the other IGR metrics (p < 0.001).

CONCLUSION

MCS was a strong, independent predictor of favorable functional outcomes and demonstrated significantly superior prognostic performance compared with individual IGR metrics.