J Korean Soc Emerg Med.  2021 Dec;32(6):493-508.

Right cardiac border to cardiac diameter (RB:CD) ratio, a simple radiological index associated with a good neurological outcome

• Choi H
• Chon SB
• Yoo SM
• Kim H

Abstract

Objective
The optimum chest compression point during cardiopulmonary resuscitation (CPR) associated with a good neurological outcome is unestablished. We aimed to suggest the association between the point and a simple index measured on anteroposterior chest radiography (chest_AP).
Methods
This retrospective, cross-sectional study included all adults with available chest_AP who arrived at a university hospital from January 2014 to June 2019 for non-traumatic out-of-hospital cardiac arrest (OHCA). Distances from the vertical midsternum to the farthest right and left cardiac borders were defined as RB and LB, respectively. Their sum provided cardiac diameter (CD). Assuming the universality of cardiac anatomy, the cardiac structure immediately beneath the midsternum was compressed most forcefully during CPR. The influencing outcome of CPR was determined using the RB:CD ratio. We investigated the association of RB:CD ratio with a good neurological outcome at discharge using multiple logistic regression analysis, adjusting for the core Utstein elements and comorbidities.
Results
Among 429 patients (63.2±14.5 years; 121 [28.2%] female), return of spontaneous circulation, survival-to-discharge and good neurological outcome at discharge were achieved in 259 (60.4%), 121 (28.2%) and 84 (19.6%) cases, respectively. The RB:CD ratio (0.279±0.072) was divided into semi-tertiles to enhance clinical usage: <0.25 (n=149, reference), 0.25-0.30 (n=119) and >0.30 (n=161). The second group was associated with good neurological outcome (odds ratio, 6.00 [95% confidence interval, 1.58-22.8], P=0.010).
Conclusion
An RB:CD ratio of 0.25-0.30 measured on chest_AP is associated with good neurological outcomes in OHCA victims receiving CPR.

Keyword

Cardiopulmonary resuscitation; Heart ventricles; Radiography; Thoracic; Treatment outcome