Clinical MRI interpretation for outcome prediction in cardiac arrest

Background In clinical practice, magnetic resonance imaging (MRI) is commonly used to assess the severity of a cardiac arrest patient's cerebral injury, utilizing treating neurologists' imaging interpretation. We sought to determine whether clinical interpretation of diffusion-weighted imaging (DWI) helps to determine poor outcome in comatose cardiac arrest patients. Methods We analyzed 80 consecutive MRIs from patients in coma following cardiac arrest. Each study was graded as "normal" or "abnormal restricted diffusion" in pre-specified brain regions by two blinded stroke neurologists. Poor outcome was defined as a modified Rankin Scale (mRS) score >4 at 3 months. Formal interpretations of neuroimaging by non-blinded neuroradiologists were compared with the blinded reviews by the stroke neurologists. Results DWI abnormalities were highly sensitive (98.5 %) but only modestly specific (46.2 %) for predicting poor neurological outcome. Inter-observer reliability was moderate (kappa = 0.49 ± 0.32), with 91 % agreement between study observers, and no significant differences in study observers' interpretations (p = 0.125). There were, however, significant differences between the study observers and the clinical neuroradiologists in identifying studies showing evidence of global hypoxic-ischemic injury (p = 0.001). Conclusions The qualitative evaluation of imaging abnormalities by stroke physicians in comatose cardiac arrest patients is a highly sensitive method of predicting poor outcome, but with limited specificity.