Functional connectivity in resting-state networks relates to short-term global cognitive functioning in cardiac arrest survivors

Abstract

Long-term cognitive impairment is common in cardiac arrest survivors. Screening to identify patients at risk is recommended. Functional magnetic resonance brain imaging (fMRI) holds potential to contribute to prediction of cognitive outcomes. In this study, we investigated the possible value of early changes in resting-state networks for predicting short and long-term cognitive functioning of cardiac arrest survivors. We performed a prospective multicenter cohort study in cardiac arrest survivors in three Dutch hospitals. Resting-state fMRI scans were acquired within a month after cardiac arrest. We primarily focused on functional connectivity within the default-mode network (DMN) and salience network (SN), and additionally explored functional connectivity in seven other networks. Cognitive outcome was measured using the Montreal Cognitive Assessment (MoCA) during hospital admission and at 3 and 12 months, and by neuropsychological examination (NPE) at 12 months. We tested mixed effects models to evaluate the value of connectivity within the networks for predicting global cognitive outcomes at the three time points, and long-term cognitive outcomes in the memory, attention, and executive functioning domains. We included 80 patients (age 60 ± 11 years, 72 (90%) male). MoCA scores increased significantly between hospital admission and 3 months (ΔMoCA_hospital-3M = 2.89, p < 0.01), but not between 3 and 12 months (ΔMoCA_3M-12M = 0.38, p = 0.52). Connectivity within the DMN, SN, and dorsal attention network (DAN) was positively related to global cognitive functioning during hospital admission (β_DMN = 0.85, p = 0.03; β_SN = 1.48, p < 0.01; β_DAN = 0.96, p = 0.01), but not at 3 and 12 months. Network connectivity was also unrelated to long-term memory, attention, or executive functioning. Resting-state functional connectivity in the DMN, SN, and DAN measured in the first month after cardiac arrest is related to short-term global, but not long-term global or domain-specific cognitive performance of survivors. These results do not support the value of functional connectivity within these RSNs for prediction of long-term cognitive performance after cardiac arrest.

Keywords: cardiac arrest; cognition; functional MRI; functional connectivity; resting‐state networks.

FIGURE 1

(a) Overview of MoCA scores during hospital admission (red, left), 3 months (yellow, middle), and 12 months (blue, right) after cardiac arrest. (b) Overview of memory scores (dark blue, left), attention scores (blue, middle), and executive functioning scores (light blue, right) at 12 months after cardiac arrest. Violins show density of the cognitive scores. Asterisks indicate levels of significance (*p < 0.05, **p < 0.01), dashed lines indicate the thresholds for cognitive impairment (MoCA <26, NPE z‐score <−1.5). MoCA = Montreal Cognitive Assessment; NPE, neuropsychological examination.

FIGURE 2

Top panels: Spatial maps of the two resting‐state networks. Lower panels: Results of mixed effects regression models of connectivity strength within the default‐mode network (a) and salience network (b) with MoCA scores during hospital admission, 3 months, and 12 months after cardiac arrest. These results show a positive relation between connectivity strength in DMN or SN and MoCA score during hospital admission and, but not between connectivity strength and MoCA score at 3 and 12 months after cardiac arrest. Results are corrected for study site, conscious state during MRI, and time between cardiac arrest and MRI. DMN, default‐mode network; MoCA, Montreal Cognitive Assessment; SN, salience network.