Risk Factors of Hypoperfusion on MRI of Ischemic Stroke Patients Within 7 Days of Onset

Abstract

Objective: Hypoperfusion is an important factor determining the prognosis of ischemic stroke patients. The present study aimed to investigate possible predictors of hypoperfusion on MRI of ischemic stroke patients within 7 days of stroke onset. Methods: Ischemic stroke patients, admitted to the comprehensive Stroke Center of Shanghai Fourth People's Hospital affiliated to Tongji University within 7 days of onset between January 2016 and June 2017, were recruited to the present study. Magnetic resonance imaging (MRI), including both diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI), was performed within 7 days of the symptom onset. Time to maximum of the residue function (T _max ) maps were automatically evaluated using the RAPID software. The volume of hypoperfusion was measured outside the infarct area based on ADC < 620 × 10^-6 mm²/s. The 90 d mRS score was assessed through either clinic visits or telephone calls. Multivariate step-wise analysis was used to assess the correlation between MR findings and clinical variables, including the demographic information, cardio-metabolic characteristics, and functional outcomes. Results: Among 635 patients admitted due to acute ischemic stroke within 7 days of onset, 241 met the inclusion criteria. Hypoperfusion volume of 38 ml was the best cut-off value for predicting poor prognosis of patients with cerebral infarction (90 d-mRS score ≥ 2). The incidences of MR perfusion T _max > 4-6 s maps with a volume of 0-38 mL or >38 mL were 51.9% (125/241) and 48.1% (116/241), respectively. Prior stroke and vascular stenosis (≥70%) were associated with MR hypoperfusion. Multivariate step-wise analysis showed that prior stroke and vascular stenosis (≥70%) were risk factors of T _max > 4-6 s maps, and the odds ratios (OR) were 3.418 (adjusted OR 95% CI: 1.537-7.600), and 2.265 (adjusted OR, 95% CI: 1.199-4.278), respectively. Conclusion: Our results suggest that prior stroke and vascular stenosis (≥70%) are strong predictors of hypoperfusion in patients with acute ischemic stroke within 7 days of stroke onset.

Keywords: correlation analysis; ischemic stroke; magnetic resonance imaging; risk factors; time to maximum of the residue function.

Figure 1

Flowchart of patient recruitment.

Figure 2

Diffusion and perfusion abnormalities of a patient treated with intravenous tPA. A 63-year-old male who presented with dysarthria and weakness in the right arm, hypertension for more than 3 years, vascular stenosis (≥70%), no previous ischemic stroke, MRI scan was completed 6 days after stroke onset. DWI, diffusion-weighted imaging; PWI, perfusion-weighted imaging; ADC, apparent diffusion coefficient; T_max, Time to maximum of the residue function. T_max color scale: 4 s < T_max ≤ 6 s (blue); 6 s < T_max ≤ 8 s (green); 8 s < T_max ≤ 10 s (yellow); 10 s < T_max (red). (A) DWI, lesion volume was 22 ml. (B) ADC, lesion volume was 9 ml. (C) PWI, lesion volumes according to T_max delay were as follows: T_max > 4 s, 132 ml; T_max > 4 s–ADC volume, 123 ml; T_max > 6 s, 22 ml; T_max > 6 s–ADC volume, 13 ml; T_max > 8 s, 4 ml; and T_max > 10 s, 3 ml.

Figure 3

Area under the ROC curve predicts hypoperfusion based on 90 d-mRS.