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Objective:
Dependent contrast layering sign (DCLS), layering of contrast agent in the dependent part of the central venous system is associated with compromised cardiac function and imminent cardiac arrest. Thus, prompt recognition of DCLS is important. However, there is no systemic research on the association of DCLS with cardiac arrest and mortality. Hence, we studied DCLS in various vascular structures and organs on CT and its clinical implications.

Materials and Methods:
This single center retrospective study 21 patients obtained by searching keywords 'layering/ pooling of contrast' or 'dependent layering of contrast' in contrast CT chest, abdomen and pelvis performed between January 2008 and January 2022. Two body imagers reviewed for DCLS and reflux in vascular structures and parenchyma of abdominal solid organs. Layering of contrast in venous structures near the injection site was regarded as residual contrast and excluded. The statistical significance of the radiologic findings in association with clinical data such as cardiac arrest, death during hospital stay, and shock index were analyzed.

Results:
Among the 21 patients, 6 (28.5%) had cardiac arrest within 24 hours, all of which occurred within 2 hours of CT. 3 of these 6 had cardiac arrest within 1 hour. Patients with DCLS in the right atrium experienced highest rate of cardiac arrest within 2 hours (80%, 4 of 5), followed by those with liver parenchyma involvement (71.4%, 5 of 7). Statistical analysis reveals that the occurrence of cardiac arrest within 2 hours is significantly higher in patients with DCLS in the right atrium (p=0.02, odds ratio = 21.6) and liver parenchyma (p=0.01, odds ratio = 24.8). 8 (38.1%) have died during the same hospital stay in which the CT scans were performed. Patients with DCLS in liver parenchyma demonstrate highest rate of in-hospital mortality (57.1%, 4 of 7), followed by involvement of other vessels (50%). The mean number of involved vessels or organs per patient was 3.3±2.4 (range 1-9). Patients who had cardiac arrest within 2 hours exhibit a higher mean (5.7±2.7) compared to those who did not experience cardiac arrest (2.7±2.0). The total number of involved structures (p=0.01) and the number of major structures (p=0.001) are significantly higher in patients with cardiac arrest within 2 hours. The mean shock index was 1.08±0.50 (range 0.5-2.6), with a shock index of 0.9 or higher observed in 66.6% (12 of 18) of patients. However, no statistically significant differences were observed in association with CT findings. Finally, the correlation coefficient between the total number of involved structures and the shock index did not attain statistical significance (p = 0.47).

Conclusion:
DCLS in the vessels and solid organs is associated with high rates of imminent cardiac arrest and mortality. DCLS in right atrium and liver parenchyma is significantly associated with cardiac arrest within 2 hours. It is more frequently connected with death during the hospital stay. Therefore, radiologists and even technologists need to recognize these findings to alert clinicians about the risk of cardiac arrest immediately.