RESUMEN
BACKGROUND AND OBJECTIVES: Diffusion magnetic resonance imaging (MRI) can quantify extent of hypoxic-ischemic brain injury after cardiac arrest. Our objective was to determine the association between adult-derived threshold of apparent diffusion coefficient (ADC) <650x10-6mm2/s in >10% of brain tissue and unfavorable outcome after pediatric cardiac arrest. Since ADC decreases exponentially as a function of increasing age, we determined association 1) having >10% of brain tissue below a novel age-dependent ADC threshold, and 2) age-normalized whole brain mean ADC and unfavorable outcome. METHODS: Retrospective study of patients ≤18 years old who had cardiac arrest and a clinically obtained brain MRI within 7 days. Primary outcome was unfavorable neurologic status at hospital discharge based on Pediatric Cerebral Performance Category (PCPC) score. ADC images were extracted from three-direction diffusion imaging. We determined whether each patient had >10% of voxels with ADC below prespecified thresholds. We computed whole brain mean ADC for each patient. RESULTS: One-hundred-thirty-four patients were analyzed. Patients with ADC <650x10-6mm2/s in >10% of voxels had 15 times higher odds (95%CI 5, 65) of unfavorable outcome compared to patients with ADC <650x10-6mm2/s (AUROC 0.72 [95%CI 0.63, 0.80]). This ADC criteria had a sensitivity and specificity of 0.49 and 0.94, and positive and negative predictive values of 0.93 and 0.52 for unfavorable outcome. The age-dependent ADC threshold that yielded optimal sensitivity and specificity for unfavorable outcome was <300x10-6mm2/s below each patient's predicted whole brain mean ADC. The sensitivity, specificity, positive and negative predictive values for this ADC threshold were 0.53, 0.96, 0.96, and 0.54, respectively (OR: 26.4 [95%CI 7.5, 168.3]; AUROC 0.74 [95%CI 0.66, 0.83]). Lower age-normalized whole brain mean ADC was also associated with unfavorable outcome (OR 0.42 [0.24, 0.64], AUROC 0.76 [95%CI 0.66, 0.82]). DISCUSSION: Quantitative diffusion thresholds on MRI within 7 days after cardiac arrest were associated with unfavorable outcome in children. Age-independent ADC threshold was highly specific for predicting unfavorable outcome. However, specificity and sensitivity increased when using age-dependent ADC thresholds. Age-dependent ADC thresholds may improve prognostic accuracy and require further investigation in larger cohorts. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that quantitative diffusion-weighted imaging (DWI) within 7 days post-arrest can predict an unfavorable clinical outcome in children.