Out-of-Hospital Cardiac Arrest in Greece: Epidemiology, Resuscitation Characteristics and Outcomes from the EuReCa-THREE Study

Authors: Nikolaidou O¹^a*, Aslanidis Th²^b, Nikolaou N ³^c,  Vangos G⁴^d

 

¹ MD, MSc- General Medicine- Prehospital Emergency Medicine,
² MD, PhD, Anesthesia-Critical Care-Prehospital Emergency Medicine, ORCID: 0000-0002-8325-8861
³ MD, PhD, Cardiology, ORCID: 0000-0002-2564-1707
⁴ EMT-Emergency Medical Technician

^a Mobile Medical Unit, National Center for Emergency Care (EKAB), Thessaloniki, Greece
^b Intensive Care Unit, “Agios Pavlos” General Hospital, Thessaloniki, Greece
^c Cardiology Department and ICU, “Konstantopouleio” General Hospital, Athens, Greece
^d Motorcycle Response Unit- Special Disaster Medical Unit, National Center for Emergency Care (EKAB), Thessaloniki, Greece

*Correspondence: Mavilli 33, PC 55535, Thessaloniki, Greece, e-mail: , Tel.: +0030644972494

ABSTRACT

The European Registry of Cardiac Arrest Study THREE (EuReCa-THREE) prospectively collected standardized out-of-hospital cardiac arrest (OHCA) data across participating European countries using the Utstein reporting framework. Participation in EuReCa-THREE provided an opportunity to describe OHCA characteristics and outcomes in Greece and to compare them with contemporary European data.

A registry-based observational study was conducted using the Greek EuReCa-THREE dataset collected between 1 September and 30 November 2022. The study was performed within the Emergency Medical Services (EMS) region of Thessaloniki, representing the Greek participation in EuReCa-THREE and covering a population of approximately 1.1 million. Cases were collected according to the EuReCa-THREE protocol through prospective registration supplemented by systematic review of EMS records to ensure case completeness. Demographic characteristics, arrest circumstances, resuscitation variables and outcomes were analysed. The primary outcome was any return of spontaneous circulation (ROSC).

A total of 302 confirmed OHCA cases were identified. Mean age was 72 years and 60.3% were male. Most arrests occurred at home (78.5%). Cardiopulmonary resuscitation (CPR) was attempted in 37.4% of cases, while EMS resuscitation was initiated or continued in 99 patients. ROSC was achieved in 31.3% of EMS-treated patients. Initial shockable rhythm was strongly associated with ROSC (63.6% vs 15.2%; OR 9.8, 95% CI 3.69–26.05; p<0.001). Hospital admission with ROSC or ongoing CPR occurred in 35.4% of EMS-treated patients; 19.2% arrived at hospital with ROSC and 16.2% under ongoing CPR. Hospital discharge survival was confirmed in 7.1% of EMS-treated patients; however, complete hospital follow-up was not available for all cases. More than one quarter of all cardiac arrests occurred in individuals aged 41–65 years (27.8%).

This first detailed Greek EuReCa-THREE analysis provides important information regarding OHCA epidemiology, resuscitation characteristics and outcomes in Greece. OHCA affected predominantly older individuals and occurred mainly at home, although a substantial proportion of cases involved individuals of working age. ROSC was achieved in approximately one third of EMS-treated patients, and initial shockable rhythm was the strongest factor associated with ROSC in this cohort. Continued efforts to strengthen community response, dispatcher-assisted CPR, public-access defibrillation and OHCA surveillance may contribute to improved OHCA outcomes in Greece.

 

INTRODUCTION

Out-of-hospital cardiac arrest (OHCA) remains one of the leading causes of death worldwide and represents a major public health challenge. Survival depends on timely recognition of cardiac arrest, early activation of Emergency Medical Services (EMS), prompt initiation of cardiopulmonary resuscitation (CPR), rapid defibrillation and high-quality advanced life support (ALS)^1-3. Despite substantial advances in resus citation science and post-resuscitation care, marked differences in OHCA incidence, management and outcomes continue to exist between countries and healthcare systems.

The European Registry of Cardiac Arrest (EuReCa) was established by the European Resuscitation Council (ERC) to provide standardized OHCA data across Europe using the Utstein reporting framework^4–6. Previous registry phases, including EuReCa ONE and EuReCa TWO, demonstrated considerable variation in OHCA incidence, bystander response, EMS performance and survival across participating countries ^4,5. EuReCa THREE further expanded these efforts by prospectively collecting contemporary OHCA data and focusing on patient outcomes and EMS time intervals using a standardized European methodology⁶.

The EuReCa-THREE project provided an opportunity to describe OHCA characteristics and outcomes in Greece and to compare them with contemporary European data. During the study period, participation from the Thessaloniki EMS region represented the Greek contribution to the registry, covering a population of approximately 1.1 million. To our knowledge, this study represents the first detailed Greek analysis of EuReCa-THREE data, providing systematically collected information on OHCA epidemiology, resuscitation characteristics and outcomes in Greece.

The primary aim of this study was to describe the epidemiology, resuscitation characteristics and outcomes of OHCA cases recorded during the EuReCa-THREE study period in the Greek EMS region participating in the registry. The primary outcome was any return of spontaneous circulation (ROSC).

Secondary objectives included evaluation of factors associated with ROSC, including initial rhythm, witnessed status and bystander CPR, as well as exploratory analyses of workplace and EMS-witnessed cardiac arrests.

Materials and Methods

Study Design and Setting

This registry-based observational study was conducted according to the methodology and definitions of the EuReCa-THREE project. EuReCa-THREE was coordinated by the ERC and prospectively collected standardized OHCA data across participating European countries using the Utstein reporting framework^6-8.

The Greek contribution to EuReCa-THREE was provided through the Thessaloniki branch (EKAB-2) of the National Centre for Emergency Care (EKAB), covering a population of approximately 1.1 million. A dedicated permanent OHCA registry was not in place in Thessaloniki. For the purposes of the study, OHCA cases were identified from routinely maintained EMS dispatch and operational records, and the required variables were subsequently collected and processed according to standardized study procedures. The study period extended from 1 September 2022 to 30 November 2022, in accordance with the EuReCa-THREE protocol.

The participating EMS system operates a tiered response model that may include ambulances, rapid response vehicles, motorcycle responders and physician-staffed Mobile Medical Units (MMUs). Depending on resource availability and proximity to the incident, any of these units may be the first to arrive on scene. Advanced life support interventions are primarily provided by physician-staffed MMUs, although selected ALS interventions may also be initiated by specially trained EMS personnel assigned to these response units.

Case Identification and Data Collection

All patients sustaining a confirmed OHCA during the study period were eligible for inclusion. Cases were identified through multiple complementary sources, including EMS dispatch records, ambulance patient care records, physician-completed EuReCa case report forms and EMS operational databases.

Data collection followed the EuReCa-THREE study protocol, with prospective registration supplemented by systematic review of EMS records to ensure case completeness. Potential duplicate entries were identified and removed following review of patient demographics, incident location, date and time of arrest, and EMS documentation. For patients receiving ALS, additional information was obtained from standardized EuReCa forms completed by EMS physicians attending the incident. Supplementary information regarding hospital outcomes was sought from receiving hospitals and other available sources whenever feasible.

Definitions

Definitions and variable coding followed the EuReCa-THREE data dictionary and Utstein recommendations^6-8.
OHCA was defined as the cessation of cardiac mechanical activity occurring outside the hospital setting and confirmed by the absence of signs of circulation.
ROSC was defined according to Utstein recommendations as return of spontaneous circulation lasting more than 30 seconds without the need for chest compressions.
A witnessed cardiac arrest was defined as an arrest seen, heard or directly monitored by another person. Witness categories included bystander-witnessed and EMS-witnessed cardiac arrests.
Bystander CPR was defined as CPR initiated by a person who was not part of the organized emergency response system.

Initial cardiac rhythm was classified as shockable or non-shockable according to the EuReCa-THREE data dictionary.

Outcomes

The primary outcome of the present Greek analysis was any return of spontaneous circulation (ROSC).
Secondary outcomes included hospital admission with ROSC or ongoing CPR, survival to hospital discharge, and 30-day survival when available.

Exploratory analyses were performed for clinically relevant subgroups, including workplace cardiac arrests and EMS-witnessed arrests, as well as for temporal patterns of OHCA occurrence.

EMS Time Intervals

EMS operational time points, including arrival on scene, departure from scene and arrival at the receiving hospital, were electronically recorded in the EMS dispatch system. For the present analysis, EMS response interval was defined as the time from receipt of the emergency call to arrival of the first EMS unit on scene. EMS-witnessed arrests were excluded from response interval analyses, in accordance with the EuReCa-THREE methodology.

Although additional EMS time intervals were available, the response interval was selected as the primary time metric for the present analysis. Other intervals may reflect a combination of clinical, operational and logistical factors and were therefore not examined as primary time-related outcomes.

Statistical Analysis

Continuous variables are presented as mean ± standard deviation (SD) or median with interquartile range (IQR), as appropriate according to data distribution. Categorical variables are presented as frequencies and percentages.

Descriptive analyses were performed for the entire OHCA cohort and separately for the subgroup of EMS-treated patients.

Associations between categorical variables and ROSC were evaluated using the Chi-square test or Fisher’s exact test when expected cell counts were small. Continuous variables were compared using the independent-samples t-test or Mann–Whitney U test, as appropriate.
Odds ratios (ORs) with corresponding 95% confidence intervals (95% CIs) were calculated where appropriate. Statistical significance was defined as a two-sided p-value <0.05.

Because of the limited number of outcome events and incomplete hospital follow-up for some transported patients, multivariable regression modelling was not performed. Analyses were therefore restricted to descriptive and univariable comparisons.

Ethical Considerations

Institutional approval for the Greek participation in EuReCa-THREE and the collection of the relevant data was obtained from the National Centre for Emergency Care (EKAB) prior to study initiation. All data were anonymized and handled in accordance with applicable national and European data protection regulations.

RESULTS

Study Population

During the EuReCa-THREE study period, 302 confirmed OHCA cases were identified within the participating EMS region of Thessaloniki, covering a population of approximately 1.1 million.

Male patients accounted for 60.3% of all cases. Most arrests occurred at home (78.5%). More than one quarter of all OHCAs occurred among individuals aged 41–65 years (27.8%), whereas the highest frequencies were observed among older age groups.

CPR was attempted in 37.4% of OHCA cases. Resuscitation was initiated or continued by EMS in 32.8% of cases, comprising the principal analytical cohort for subsequent outcome analyses. The difference reflects cases in which CPR had been initiated before EMS arrival but was not continued following EMS assessment. An overview of OHCA characteristics and outcomes is presented in Table 1.

The age distribution of all recorded OHCA cases is shown in Figure 1.

 

 

Resuscitation Characteristics

Within the EMS-treated cohort, shockable rhythm was present in 33.3% of patients, while non-shockable rhythms accounted for 66.7%.

Among EMS-treated arrests, 92.9% were bystander-witnessed, 5.1% were EMS-witnessed, and only 2.0% were unwitnessed.

Bystander CPR was documented in 46.5% of EMS-treated patients, with compression-only CPR representing the most frequently documented form (30.3%).

EMS resuscitation was initiated or continued in 38.5% of male patients compared with 24.2% of female patients.

Detailed demographic and resuscitation characteristics of all OHCA cases and the EMS-treated cohort are presented in Table 2.

 

 

EMS Response Interval

The mean EMS response interval was 9.2 ± 3.7 minutes, with 26.6% of EMS-treated patients reached within 7 minutes. EMS-witnessed arrests were excluded from response interval analyses. Mean response interval was 9.1 ± 3.2 minutes among patients achieving ROSC and 9.3 ± 4.0 minutes among those without ROSC (p=0.793). Among patients with confirmed survival-to-hospital-discharge status and available response interval data, survivors had a shorter mean response interval than non-survivors (7.0 ± 4.6 vs 10.6 ± 4.2 minutes, respectively), although this difference did not reach statistical significance (p=0.072).

Factors associated with ROSC

ROSC was achieved in 31.3% of EMS-treated patients. Initial cardiac rhythm was strongly associated with ROSC. Detailed results are presented in Table 3 and Figure 2. ROSC was achieved in 63.6% of patients presenting with a shockable rhythm compared with 15.2% of those presenting with a non-shockable rhythm (OR 9.8, 95% CI 3.69–26.05; p<0.001).

 

ROSC occurred in 31.5% of bystander-witnessed arrests and in 40.0% of EMS-witnessed arrests, whereas no ROSC was observed among unwitnessed arrests (p=0.580).

Bystander CPR was documented in 46.5% of EMS-treated patients and in 62.2% of cases with available CPR information. Compression-only CPR was the most frequently documented form. ROSC occurred in 37.0% of patients receiving bystander CPR compared with 28.6% of those without bystander CPR (p=0.460). Factors associated with ROSC are summarized in Figure 2.

Temporal Distribution

Time of OHCA occurrence was available for 250 cases and was used for descriptive analysis of temporal patterns only. The highest proportion of OHCAs occurred during the morning period between 06:00 and 11:59, accounting for 37.2% of recorded events. A similar temporal pattern was observed among EMS-treated patients, with 37.1% of arrests occurring during the same period.

Table 4 presents the distribution of OHCA occurrence according to time of day. OHCA occurrence was broadly similar between weekdays and weekends after adjustment for the number of calendar days. Overall, 71.2% of arrests occurred on weekdays and 28.8% during weekends; however, the mean daily incidence was comparable between the two periods.

The temporal distribution of OHCA occurrence is illustrated in Figure 3.

 

 

 

Exploratory Subgroup Analyses

            EMS-Witnessed Cardiac Arrest

EMS-witnessed OHCA represented 5.1% of EMS-treated arrests, with ROSC achieved in 40.0% of these patients.

            Workplace Cardiac Arrest

Workplace OHCA accounted for 5.0% of all recorded arrests. Patients experiencing workplace OHCA were younger than the overall OHCA population (mean age 54.2 years) and were predominantly male (93.3%). Nearly half of workplace arrests were witnessed (46.7%). Among EMS-treated workplace arrests, a shockable initial rhythm was documented in 50.0% of cases and ROSC was achieved in 33.3%.

            Hospital Outcomes

Among EMS-treated patients, hospital admission with ROSC or ongoing CPR occurred in 35.4%, while confirmed survival to hospital discharge was 7.1%. Hospital outcome data were available for 71.4% of patients admitted to hospital; complete follow-up could not be obtained for all admitted patients.

DISCUSSION

This study represents the first detailed analysis of Greek participation in the EuReCa-THREE registry and provides contemporary data on OHCA epidemiology, resuscitation characteristics and outcomes within a large EMS region covering approximately 1.1 million inhabitants.

Several important findings emerged from this analysis. First, the overall demographic profile of OHCA in Greece was broadly comparable to that reported in other European registries, with a predominance of male patients and a high proportion of arrests occurring at home. Second, ROSC was achieved in approximately one-third of EMS-treated patients, while confirmed survival to hospital discharge remained relatively low. Third, initial shockable rhythm showed the strongest association with ROSC in this cohort. Fourth, more than one quarter of all cardiac arrests occurred in individuals aged 41–65 years, indicating that OHCA frequently affects adults of potentially working age. Finally, exploratory analyses identified potentially relevant subgroups, including workplace arrests and EMS-witnessed arrests.

Comparison with European Data

The demographic characteristics observed in the present study were broadly consistent with those reported in the EuReCa-THREE registry. Most cardiac arrests occurred in private residences and affected predominantly older individuals^5,6. Similar patterns have been reported throughout Europe and likely reflect the increasing prevalence of cardiovascular disease and multimorbidity with advancing age ^1,6,7.

Men were more frequently represented in the EMS-treated cohort than women. This pattern is consistent with previous OHCA registry studies, in which men generally constitute the majority of resuscitated patients^9,10. Differences in OHCA characteristics between men and women may contribute to this pattern. Patient sex is not a criterion for the initiation or continuation of EMS resuscitation.Among EMS-treated patients, witnessed arrests and shockable initial rhythms were more frequent in the present study than in EuReCa-THREE⁶. However, neither witness status nor initial rhythm, in itself, constituted a criterion for initiating or continuing EMS resuscitation; such decisions were based on the overall clinical assessment and circumstances of the arrest.

The proportion of EMS-treated patients achieving ROSC was comparable to that reported by several European EMS systems. Nevertheless, direct comparisons between countries should be interpreted cautiously because of differences in EMS organization, inclusion criteria, dispatch systems, first-responder systems, AED availability and hospital follow-up procedures^6.

Initial Rhythm and ROSC

Initial shockable rhythm was strongly associated with ROSC and represented the most important resuscitation-related finding of this study. Patients presenting with a shockable rhythm were substantially more likely to achieve ROSC than those presenting with non-shockable rhythms. This finding is consistent with the established pathophysiology of OHCA and emphasizes the importance of early rhythm recognition and rapid defibrillation^3,11.

In the overall OHCA cohort (N=302), the relatively low proportion of shockable initial rhythms may reflect delayed recognition, delayed EMS activation, unwitnessed arrests, non-cardiac causes of arrest, or the high proportion of events occurring at home among older patients. These findings further support the need for public education, early recognition of cardiac arrest and wider access to defibrillation^1,11.

EMS Response Interval

The mean EMS response interval among EMS-treated patients in the present cohort was 9.2 minutes, compared with 12.2 minutes in the international EuReCa-THREE study, while the proportion of patients reached within 7 minutes was similar (26.6% vs 25%, respectively)⁶. Response interval did not differ meaningfully according to ROSC in the present cohort. In contrast, among patients with available survival-to-hospital-discharge data, survivors showed a numerically shorter response interval than non-survivors, although this difference was not statistically significant.This observation is consistent with the recognized importance of timely EMS response⁶. However, resuscitation outcome is influenced by multiple factors, and the incomplete availability of hospital outcome data precludes conclusions regarding an independent effect of response interval on survival.

Witnessed Arrest and Bystander Response

Most EMS-treated arrests were witnessed by bystanders. However, neither witness status nor bystander CPR was significantly associated with ROSC in this cohort. Among the documented forms of bystander CPR, the highest ROSC proportion was observed with compression-only CPR. Interpretation of these findings is limited by the lack of detailed information on the timing and quality of bystander CPR as well as by variability in bystander training and pre-arrest patient characteristics. Dispatcher-assisted CPR instructions were provided following telephone assessment by trained EMS personnel, although a standardized scripted protocol was not used. These factors may have influenced the observed associations with ROSC. Regardless of the findings in the present cohort, early recognition, prompt bystander CPR and rapid access to automated external defibrillation (AED) remain central components of the chain of survival ^2,17.

EMS-Witnessed Cardiac Arrest

EMS-witnessed arrests represented a distinct subgroup, with a numerically higher ROSC proportion than bystander-witnessed arrests. This observation is consistent with the clinical expectation that EMS-witnessed arrests may benefit from immediate recognition, rapid rhythm assessment and prompt initiation of advanced resuscitation measures. However, EMS-witnessed arrest should not be considered uniformly favourable, as outcome remains strongly influenced by the underlying cause of arrest, initial rhythm and pre-arrest clinical condition¹⁶.

Workplace Cardiac Arrest

An exploratory analysis of workplace OHCA revealed a predominantly male population with a substantially lower mean age than the overall OHCA cohort.

Approximately half of workplace arrests were witnessed. Among EMS-treated workplace arrests, shockable rhythm was present in 50.0% of cases and ROSC was achieved in 33.3%.

These findings highlight workplace OHCA as a distinct setting, particularly because it affects comparatively younger individuals.

The occurrence of witnessed arrests and shockable initial rhythms also underscores the potential importance of an effective early response in the workplace. Wider availability of AEDs, together with CPR training and preparedness among employees, may provide important opportunities to strengthen the response to cardiac arrest in this setting^12,13.

Temporal Pattern of OHCA

An additional observation was the predominance of cardiac arrests during the morning hours. More than one third of recorded OHCAs occurred between 06:00 and 11:59. This finding is consistent with previous studies demonstrating a circadian pattern of OHCA occurrence, with a predominance of events during the morning hours^14,15.

The observed morning peak may have practical implications for EMS resource planning and public awareness initiatives.

Hospital Outcomes and Follow-up

Hospital admission with ROSC or ongoing CPR occurred in 35.4% of EMS-treated patients, while confirmed survival to hospital discharge was 7.1%.

The combined admission outcome is clinically relevant, as patients may be transported either with sustained ROSC or under ongoing CPR when continued resuscitation, hospital-based interventions or specific clinical circumstances warrant transport.

Hospital outcome data were not available for all admitted patients, reflecting the challenges of post-resuscitation follow-up across multiple receiving hospitals and data sources.

Accordingly, the reported survival to hospital discharge represents confirmed survival based on available follow-up rather than a complete estimate of survival in the cohort.

Strengths and Limitations

The principal strength of this study is the use of standardized EuReCa-THREE methodology and Utstein definitions, enabling comparison with other European registry data^7,8. In addition, case identification was strengthened by systematic review of EMS dispatch records, ambulance documentation, physician-completed forms and operational databases, while EMS operational time points were electronically recorded within the dispatch system.

Several limitations should be acknowledged. The study represents a single EMS region rather than nationwide coverage. Although the Thessaloniki EMS region covers approximately 1.1 million inhabitants and represented the Greek contribution to EuReCa-THREE, findings may not be fully generalizable to all parts of Greece.

Hospital follow-up was incomplete for some admitted patients; therefore, survival to hospital discharge reflects confirmed outcomes based on available follow-up rather than complete ascertainment across the cohort. Subgroup analyses, particularly those involving workplace and EMS-witnessed arrests, were exploratory and should be interpreted accordingly.

Conclusions

This first detailed Greek EuReCa-THREE analysis provides important information on OHCA epidemiology, resuscitation characteristics and outcomes in Greece. OHCA predominantly affected older individuals and occurred mainly at home, although more than one quarter of cases involved individuals aged 41–65 years. ROSC was achieved in approximately one third of EMS-treated patients, and initial shockable rhythm was the strongest factor associated with ROSC in this cohort.

These findings reinforce the importance of early recognition, effective bystander response, dispatcher-assisted CPR, rapid access to defibrillation and systematic OHCA surveillance. Expansion of CPR training, wider AED availability, including in workplaces, and the development of a national OHCA registry may represent important priorities for strengthening the response to OHCA and improving outcomes in Greece.

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Additional materials: No

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Acknowledgements: No

Authors’ contributions: AT: Conceptualization, literature review, data analysis, manuscript preparation, NO, NN, NG: Data collection, literature review. All authors read and approved the final manuscript.

Funding: Not applicable

Availability of supporting data: Not applicable

Competing interests: The authors declared no competing interests.

Received: August 2026, Accepted:  August 2026, Published: September 2026.

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Citation: Nikolaidou O, Aslanidis Th, Nikolaou N, Vangos G: Intensive care unit activity: Brief review of surgical emergencies in emergency department in a secondary urban hospital: focus on the years after COVID-19. Greek e j Perioper Med. 2026;25(b):2-17.

 

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