Clinical paperAssociation between the extent of diffusion restriction on brain diffusion-weighted imaging and neurological outcomes after an out-of-hospital cardiac arrest
Introduction
A substantial proportion of patients who experienced out-of-hospital cardiac arrest (OHCA) die because of hypoxic-ischaemic brain injury. In these patients, the neurological prognosis should be evaluated when making decisions on care, including the continuation of critical care or the withdrawal of life-sustaining therapy.1
Among the modalities used for neurologic prognostication in patients with cardiac arrest, brain magnetic resonance imaging (MRI) interprets the degree of hypoxic-ischaemic brain injury.2, 3 Several studies have shown an association between unfavourable neurological outcomes and the burden of injury on fluid-attenuated inversion recovery (FLAIR) and diffusion MRI.2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 However, previous studies have small sample sizes, and the assessment methods used were not standardised. Furthermore, automated analysis methods such as apparent diffusion coefficient (ADC) metrics are difficult to directly apply to clinical practice due to the need for specific software and complex pre-processing of measurements in some software.4 If a standardised analysis method that can be easily used for obtaining measurements is developed, the clinical usefulness of brain MRI in evaluating the neurological prognosis of patients with OHCA could increase.
The Alberta Stroke Program Early Computed Tomography Score (ASPECTS) was used to rapidly screen the extent of early ischaemic changes on brain computed tomography (CT) scans of patients with stroke.15 This tool is a semi-quantitative method for measuring scores by dividing the territory of the middle cerebral artery.15 Considering that global hypoxic-ischaemic brain injury commonly occurs, the ASPECTS can be used to assess for the presence of injury from the middle cerebral artery to the territory of other cerebral arteries. Thus, estimating the volume of cytotoxic oedema observed on brain MRI may be possible. It may also be an alternative to standardisation because it is a simple modification of the existing method. Previous studies have used a modified ASPECTS version to screen the extent of ischaemic changes on brain CT scans and evaluate the neurological prognosis of patients with OHCA.16, 17, 18 However, this novel scoring method has not yet been used for acute brain MRI.
Thus, this study aimed to evaluate the association between the extent of diffusion restriction using modified ASPECTS on brain diffusion-weighted imaging (DWI) and neurological outcomes in patients who underwent targeted temperature management (TTM) after an OHCA.
Section snippets
Study design and population
This retrospective observational study used a prospectively maintained registry of patients admitted to the intensive care unit of Samsung Changwon Hospital for post-cardiac arrest care between January 2012 and September 2021. This registry enrolled patients who underwent TTM after an OHCA.
Participants
Patients aged >15 years who experienced OHCA and underwent TTM were included. Patients who did not undergo a brain MRI were excluded. In addition, considering the possibility of pseudo-normalisation, patients
Results
During the study period, 449 patients who underwent TTM after OHCA were enrolled in the hospital registry. Among them, 1 patient aged <15 years, 141 who did not undergo MRI, and 6 who underwent MRI 10 days after the ROSC were excluded. MRI was not performed for the following reasons: death prior to MRI (n = 97), early awakening (n = 27), refusal of examination (n = 15), discretion of the treating physician (n = 9), unstable vital signs (n = 5) and organ donation (n = 3). The remaining 301
Discussion
This study showed that the extent of diffusion restriction using a semi-quantitative scoring system for assessing the extent of ischaemic changes on brain DWI after an OHCA is associated with neurological outcomes at 6 months.
In this study, DWI showed clear diffusion restrictions due to hypoxic injury in the cerebral cortex and deep grey nuclei. The distribution of whole-brain DWI-ASPECTS according to the neurological outcomes at 6 months had an almost “U”-shaped appearance (Fig. 2). That is,
Conclusion
The DWI-ASPECTS showed a high degree of accuracy in predicting unfavourable neurological outcomes in patients with OHCA who underwent TTM. This finding requires external validation in other study settings.
CRediT authorship contribution statement
Jong Yoon Park: Methodology, Formal analysis. Yong Hwan Kim: Conceptualization, Data curation, Writing – original draft. Seong Jun Ahn: Writing – original draft. Jun Ho Lee: Investigation. Dong Woo Lee: Conceptualization, Methodology. Seong Youn Hwang: Supervision. Yun Gyu Song: Validation, Investigation, Project administration.
Conflicts of interest
None.
Acknowledgements
The authors thank Mi Hyeon Jin for providing statistical advice for this study.
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