Clinical Impact in Patients With Delayed Hospitalization in Patients With Out-of-hospital Cardiac Arrest
Conditions: Cardiac Arrest, Morality
Sponsor: Yonsei University

 
Call to Door Timing in Out-of-
hospital Cardiac Arrest 
 
 
Study Protocol 
 
 
Version No: 1.0.0 
Document Date: May 1, 2023 
NCT05724914 
 
 
 
 
 
 
 
 

 
 
Table of Contents 
 
1. Background ...................................................................... 3 
2. Methods ............................................................................ 4 
3. Statistical Analysis Plan .................................................. 5 
 
 
 
 
 

 
1. Background 
Out-of-hospital cardiac arrest (OHCA) remains a significant global health challenge, with 
survival rates showing modest improvement but still remaining low. The chain of survival, 
including early recognition, initiation of CPR, rapid defibrillation, and effective advanced life 
support, is crucial for improving survival rates in sudden cardiac arrest cases. Efforts to 
reduce emergency medical services (EMS) response times have been instrumental in 
enhancing survival rates during the pre-pandemic period.  
Recent studies have revealed that the coronavirus disease 2019 (COVID-19) pandemic has 
adversely affected EMS response times, potentially leading to delayed treatment for patients 
with OHCA. This has coincided with a sharp increase in OHCA mortality during the COVID-
19 pandemic era. However, there is a lack of data regarding the clinical implications of the 
time delay from first emergency call to hospital arrival on the prognosis of OHCA patients. 
Therefore, this study aims to investigate the impact of time from call to hospital arrival (CtD 
time) on clinical outcomes in patients experiencing OHCA. 
 
 
 

 
2. Methods 
2.1. Patients: Patients will be recruited from The Korea OHCA registry 
 
2.2. Time of recruitment: January 1, 2016 – December 31, 2021 
 
2.3. Inclusion criteria: Patients of out-of-hospital cardiac arrest were reported to The Korea 
OHCA Registry 
 
2.4. Exclusion criteria:  
- Non-cardiac origin (external cause including asphyxia, hanging, fall, drowning, traffic 
injury and drug overuse, respiratory, non-traumatic bleeding, malignancy, brain 
hemorrhage, other disease, unknown) 
- Under 18 years of age  
- Patients who did not receive any CPR  
- Missing data 
 
2.5. Sample size calculation 
Between 2016 and 2021, 182,508 patients have been included in the Korea OHCA registry. 
Of these about 28% have been non-cardiac origin, about 0.5% have been under 18 years of 
age, about 25% has been did not receive any CPR, and about 4% has been missing data. Thus 
we assume that about 42% i.e. 76,505 patients will fulfil the inclusion criteria without 
exclusion criteria  
 
2.6. Hypothesis 
1) The study hypothesizes that a delayed time interval between primary emergency call and 
hospital arrival (Call-to-door time[CtD]) is significantly associated with decreased survival 
rates and unfavorable neurological outcomes in OHCA patients. 
2) The COVID-19 pandemic has exacerbated the delays in CtD time, further hindering timely 
treatment and negatively impacting the survival rates and outcomes of OHCA patients. 
3) The study aims to meticulously explore and quantify the impact of various delayed factors 
on the prognosis of patients experiencing OHCA, to provide a more comprehensive 
understanding of their influence. 
 
 

 
3. Statistical Analysis Plan 
3.1.Data source 
The data for this study was sourced from the Korea OHCA Registry, a collaborative database 
established by the Korea Centers for Disease Control and Prevention and the central fire 
services under the Korean government leadership. 
 
3.2. Analysis objectives 
The primary objective of the analysis is to investigate the impact of call-to-door (CtD) time 
on the clinical outcomes of patients experiencing OHCA. The study aims to discern the 
influence of delayed hospital arrival on survival rates and neurological outcomes, considering 
the potential exacerbations brought about by the COVID-19 pandemic. 
 
3.3. Analysis sets 
The study included patients selected from OHCA patients enrolled between January 2016 and 
December 2021. Exclusions were made based on criteria such as non-cardiac origin of arrest, 
age below 18, absence of CPR, and missing data. 
 
3.4.Endpoints and covariates 
The primary outcome is death from any cause at hospital discharge. Secondary outcomes 
include death from any cause within 6 and 24 hours, and neurological outcomes assessed 
using the Glasgow-Pittsburgh Cerebral Performance Category values at hospital discharge. 
Covariates considered in the analysis include demographics and significant clinical variables 
such as age and sex. 
 
3.5.Handling of missing data 
Cases with missing data were excluded from the study as part of the pre-analysis data 
cleaning process. The study aimed to maintain the integrity and reliability of the analysis by 
ensuring that only complete and accurate data sets were utilized in the evaluation. 
 
3.6.Statistical procedures 
All data were presented by the mean with standard deviation for continuous variables and 
frequency with percentage for categorical variables. The independent two-sample t-test, chi-
squared or Fisher’s exact test were used to compared differences in continuous or categorical 

 
variables between the two groups. The Cox proportional hazards regression and logistic 
regression model were used to assess primary and secondary outcomes. The survival 
probability was estimated using Kaplan–Meier method, and the survival curves were 
compared between CtD time of <30 min and CtD time of ≥30 min groups by the log-rank 
test. Propensity-score matching and multivariable analyses were also utilized to adjust for 
confounding variables and assess the impact of CtD time on clinical outcomes. Landmark 
analysis also was conducted at 24 hours after hospital arrival. Data manipulation and 
statistical analyses were conducted using SAS version 9.3 (SAS Institute) and R software 
(version 4.1.1; R Foundation for Statistical Computing, Vienna, Austria). Statistical 
significance was set at P < 0.05. An independent statistician will conduct all statistical 
analyses to ensure objectivity and accuracy in the interpretation of the data.