Factors influencing infarct growth including collateral status assessed using computed tomography in acute stroke patients with large artery occlusion

Abstract

In major ischemic stroke caused by a large artery occlusion, neuronal loss varies considerably across individuals without revascularization. This study aims to identify which patient characteristics are most highly associated with this variability. Demographic and clinical information were retrospectively collected on a registry of 878 patients. Imaging biomarkers including Alberta Stroke Program Early CT score, noncontrast head computed tomography infarct volume, perfusion computed tomography infarct core and penumbra, occlusion site, collateral score, and recanalization status were evaluated on the baseline and early follow-up computed tomography images. Infarct growth rates were calculated by dividing infarct volumes by the time elapsed between the computed tomography scan and the symptom onset. Collateral score was graded into four levels (0, 1, 2, and 3) in comparison with the normal side. Correlation of perfusion computed tomography and noncontrast head computed tomography infarct volumes and infarct growth rates were estimated with the nonparametric Spearman's rank correlation. Conditional inference trees were used to identify the clinical and imaging biomarkers that were most highly associated with the infarct growth rate and modified Rankin Scale at 90 days. Two hundred and thirty-two patients met the inclusion criteria for this study. The median infarct growth rates for perfusion computed tomography and noncontrast head computed tomography were 11.2 and 6.2 ml/log(min) in logarithmic model, and 18.9 and 10.4 ml/h in linear model, respectively. Noncontrast head computed tomography and perfusion computed tomography infarct volumes and infarct growth rates were significantly correlated (rho=0.53; P < 0.001). Collateral status was the strongest predictor for infarct growth rates. For collateral=0, the perfusion computed tomography and noncontrast head computed tomography infarct growth rate were 31.56 and 16.86 ml/log(min), respectively. Patients who had collateral >0 and penumbra volumes>92 ml had the lowest predicted perfusion computed tomography infarct growth rates (6.61 ml/log(min)). Collateral status was closely related to the diversity of infarct growth rates, poor collaterals were associated with a faster infarct growth rates and vice versa.

Keywords: Ischemic stroke; collateral; computed tomography; perfusion imaging.

Figure 1.

(a) Correlation of PCT infarct volume and time since symptom onset demonstrated that infarct volumes are higher in patients who seek treatment within 3 h and decrease sharply with longer onset times. (b, c) Logarithmic relationship of IGRs for both PCT and NCT, using the infarcts volumes observed on PCT and NCT. (d) NCT and PCT infarct volumes and IGRs were significantly correlated.

Figure 2.

(a) Boxplot showing median and IQR of PCT IGR for each collateral status. (b, c) Clinical and imaging biomarkers predictive of PCT and NCT IGRs.

Figure 3.

Different IGRs in two patients. Patient 1: 81-year-old male patient. Time from symptom onset was 1.25 h. ASPECT score was 5 with left ICA and M1, M2 occlusion, and collateral score was 1. PCT showed a large area infarction which was 198.73 ml with penumbra 92.65 ml. The PCT IGR was 159 ml/h and 105.99 ml/log(min). Patient 2: 71-year-old male patient. Time from symptom onset was 14 h. ASPECT score was 9 with left ICA and M1 occlusion, and collateral score was 3. PCT showed a small infarct volume, which was 7.5 ml with penumbra 107.7 ml. The PCT IGR was 0.54 ml/h and 2.56 ml/log(min).

Figure 4.

Clinical and imaging parameters predictive of patient outcome at three months (mRS>2) in all patients (a), recanalized (b), and not recanalized patients (c).