Effect of COVID-19 Pandemic Lockdown on Emergency Medical Service Utilisation, and Percutaneous Coronary Intervention Volume-An Australian Perspective.

BACKGROUND: Acute coronary syndrome (ACS) admissions and percutaneous coronary intervention (PCI) volume declined during periods of COVID-19 lockdown internationally in 2020. The effect of lockdown on emergency medical service (EMS) utilisation, and PCI volume during the initial phase of the pandemic in Australia has not been well described. METHOD: We analysed data from the Victorian Cardiac Outcomes Registry (VCOR), a state-wide PCI registry, linked with the Ambulance Victoria EMS registry. PCI volume, 30-day major adverse cardiovascular and cerebrovascular events (MACCE; composite of mortality, myocardial infarction, stent thrombosis, unplanned revascularisation, and stroke), and EMS utilisation were compared over four time periods: lockdown (26 Mar 2020-12 May 2020); pre-lockdown (26 Feb 2020-25 Mar 2020); post-lockdown (13 May 2020-10 Jul 2020); and the year prior (26 Mar 2019-12 May 2019). Interrupted time series analysis was performed to assess PCI trends within and between consecutive periods. RESULTS: The EMS utilisation for ACS during lockdown was higher compared with other periods: lockdown 39.4% vs pre-lockdown 29.7%; vs post-lockdown 33.6%; vs year prior 27.1%; all p<0.01. Median daily PCI cases were similar: 31 (IQR 10, 38) during lockdown; 39 (15, 49) pre-lockdown; 39.5 (11, 44) post-lockdown; and, 42 (10, 49) the year prior; all p>0.05. Median door-to-procedure time for ACS indication during lockdown was shorter at 3 hours (1.2, 20.6) vs pre-lockdown 3.9 (1.7, 21); vs post-lockdown 3.5 (1.5, 21.26); and, the year prior 3.5 (1.5, 23.7); all p<0.05. Lockdown period was associated with lower odds for 30-day MACCE compared to pre-lockdown (odds ratio [OR] 0.55 [0.33-0.93]; p=0.026); post-lockdown (OR 0.66; [0.40-1.06]; p=0.087); and the year prior (OR 0.55 [0.33-0.93]; p=0.026). CONCLUSIONS: Contrary to international trends, EMS utilisation for ACS increased during lockdown but PCI volumes remained similar throughout the initial stages of the pandemic in Victoria, with no observed adverse effect on 30-day MACCE during lockdown. These data suggest that the public health response in Victoria was not associated with poorer quality cardiovascular care in patients receiving PCI.

Sex Disparities in Resuscitation Quality Following Out of Hospital Cardiac Arrest.

BACKGROUND: Women are known to be disadvantaged compared with men in the early links of the Chain of Survival, receiving fewer bystander interventions. We aimed to describe sex-based disparities in emergency medical service resuscitation quality and processes of care for out-of-hospital cardiac arrest. METHODS AND RESULTS: We conducted a retrospective analysis of patients who were nontraumatic with out-of-hospital cardiac arrest aged ≥16 years where resuscitation was attempted between March 2019 and June 2023. We investigated 18 routinely captured performance metrics and performed adjusted logistic and quantile regression analyses to assess sex-based differences in these metrics. During the study period, 10 161 patients with out-of-hospital cardiac arrest met the eligibility criteria, of whom 3216 (32%) were women. There were no clinically relevant sex-based differences observed in regard to external cardiac compressions; however, women were 34% less likely to achieve a systolic blood pressure >100 mm Hg on arrival at the hospital (adjusted odds ratio [AOR], 0.66 [95% CI, 0.47-0.92]). Furthermore, women had a longer time to 12-lead ECG acquisition after return of spontaneous circulation (median adjusted difference, 1.00 minute [95% CI, 0.38-1.62]) and 33% reduced odds of being transported to a 24-hour percutaneous coronary intervention-capable facility (AOR, 0.67 [95% CI, 0.49-0.91]). Resuscitation was also terminated sooner for women compared with men (median adjusted difference, -4.82 minutes [95% CI, -6.77 to -2.87]). CONCLUSIONS: Although external cardiac compression quality did not vary by sex, significant sex-based disparities were seen in emergency medical services processes of care following out-of-hospital cardiac arrest. Further investigation is required to elucidate the underlying causes of these differences and examine their influence on patient outcomes.

Outcomes of adult patients discharged at scene by emergency medical services.

BACKGROUND: The outcomes of patients who call an ambulance but are discharged at scene reflect the safety and quality of emergency medical service (EMS) care. While previous studies have examined the outcomes of patients discharged at scene, none have specifically focused on paramedic-initiated discharge. This study aims to describe the outcomes of adult patients discharged at scene by paramedics and identify factors associated with 72-hour outcomes. METHODS: This was a retrospective data linkage study on consecutive adult EMS patients discharged at scene by paramedics in Victoria, Australia, between 1 January 2015 and 30 June 2019. Multivariable logistic regression was used to investigate factors associated with EMS recontact, ED presentation, hospital admission and serious adverse events (death, cardiac arrest, category 1 triage or intensive care unit admission) within 72 hours of the initial emergency call. RESULTS: There were 375 758 cases of adults discharged at scene following EMS attendance, of which 222 571 (59.2%) were paramedic-initiated decisions. Of these, 6.8% recontacted EMS, 5.0% presented to ED, 2.4% were admitted to hospital and 0.3% had a serious adverse event in the following 72 hours. The odds of EMS recontact were increased in cases related to mental health (adjusted OR (AOR) 1.41 (95% CI 1.33 to 1.49)), among low-income government concession holders (AOR 1.61 (95% CI 1.55 to 1.67)) and in areas of low socioeconomic advantage (AOR 1.19 (95% CI 1.13 to 1.25)). The odds of hospital admission were increased in cases related to infection (AOR 3.14 (95% CI 2.80 to 3.52)) and pain (AOR 1.93 (95% CI 1.75 to 2.14)). The strongest driver of serious adverse events was an abnormal vital sign (AOR 4.81 (95% CI 3.87 to 5.98)). CONCLUSION: The occurrence of hospital admission and adverse events is rare in those discharged at scene, suggesting generally safe decision-making. However, increased attention to elderly, multimorbid patients or patients with infection and pain is recommended, as is further research examining the use of tools to aid paramedic recognition of potential for deterioration.

Artificial neural networks for ECG interpretation in acute coronary syndrome: A scoping review.

INTRODUCTION: The electrocardiogram (ECG) is a crucial diagnostic tool in the Emergency Department (ED) for assessing patients with Acute Coronary Syndrome (ACS). Despite its widespread use, the ECG has limitations, including low sensitivity of the STEMI criteria to detect Acute Coronary Occlusion (ACO) and poor inter-rater reliability. Emerging ECG features beyond the traditional STEMI criteria show promise in improving early ACO diagnosis, but complexity hinders widespread adoption. The potential integration of Artificial Neural Networks (ANN) holds promise for enhancing diagnostic accuracy and addressing reliability issues in ECG interpretation for ACO symptoms. METHODS: Ovid MEDLINE, CINAHL, EMBASE, Cochrane, PubMed and Scopus were searched from inception through to 8th of December 2023. A thorough search of the grey literature and reference lists of relevant articles was also performed to identify additional studies. Articles were included if they reported the use of ANN for ECG interpretation of Acute Coronary Syndrome in the Emergency Department patients. RESULTS: The search yielded a total of 244 articles. After removing duplicates and excluding non-relevant articles, 14 remained for analysis. There was significant heterogeneity in the types of ANN models used and the outcomes assessed, making direct comparisons challenging. Nevertheless, ANN appeared to demonstrate higher accuracy than physician interpreters for the evaluated outcomes and this proved independent of both specialty and years of experience. CONCLUSIONS: The interpretation of ECGs in patients with suspected ACS using ANN appears to be accurate and potentially superior when compared to human interpreters and computerised algorithms. This appears consistent across various ANN models and outcome variables. Future investigations should emphasise ANN interpretation of ECGs in patients with ACO, where rapid and accurate diagnosis can significantly benefit patients through timely access to reperfusion therapies.

Applications and Performance of Machine Learning Algorithms in Emergency Medical Services: A Scoping Review.

OBJECTIVE: The aim of this study was to summarize the literature on the applications of machine learning (ML) and their performance in Emergency Medical Services (EMS). METHODS: Four relevant electronic databases were searched (from inception through January 2024) for all original studies that employed EMS-guided ML algorithms to enhance the clinical and operational performance of EMS. Two reviewers screened the retrieved studies and extracted relevant data from the included studies. The characteristics of included studies, employed ML algorithms, and their performance were quantitively described across primary domains and subdomains. RESULTS: This review included a total of 164 studies published from 2005 through 2024. Of those, 125 were clinical domain focused and 39 were operational. The characteristics of ML algorithms such as sample size, number and type of input features, and performance varied between and within domains and subdomains of applications. Clinical applications of ML algorithms involved triage or diagnosis classification (n = 62), treatment prediction (n = 12), or clinical outcome prediction (n = 50), mainly for out-of-hospital cardiac arrest/OHCA (n = 62), cardiovascular diseases/CVDs (n = 19), and trauma (n = 24). The performance of these ML algorithms varied, with a median area under the receiver operating characteristic curve (AUC) of 85.6%, accuracy of 88.1%, sensitivity of 86.05%, and specificity of 86.5%. Within the operational studies, the operational task of most ML algorithms was ambulance allocation (n = 21), followed by ambulance detection (n = 5), ambulance deployment (n = 5), route optimization (n = 5), and quality assurance (n = 3). The performance of all operational ML algorithms varied and had a median AUC of 96.1%, accuracy of 90.0%, sensitivity of 94.4%, and specificity of 87.7%. Generally, neural network and ensemble algorithms, to some degree, out-performed other ML algorithms. CONCLUSION: Triaging and managing different prehospital medical conditions and augmenting ambulance performance can be improved by ML algorithms. Future reports should focus on a specific clinical condition or operational task to improve the precision of the performance metrics of ML models.

Correction: Identifying areas of Australia with high out-of-hospital cardiac arrest incidence and low bystander cardiopulmonary resuscitation rates: A retrospective, observational study.

[This corrects the article DOI: 10.1371/journal.pone.0301176.].

Prevalence and Predictors of Emergency Medical Service Use in Patients Undergoing Primary Percutaneous Coronary Intervention for ST-Elevation Myocardial Infarction.

AIM: We aim to describe prevalence of Emergency Medical Service (EMS) use, investigate factors predictive of EMS use, and determine if EMS use predicts treatment delay and mortality in our ST-elevation myocardial infarction (STEMI) cohort. METHOD: We prospectively collected data on 5,602 patients presenting with STEMI for primary percutaneous coronary intervention (PCI) transported to PCI-capable hospitals in Victoria, Australia, from 2013-2018 who were entered into the Victorian Cardiac Outcomes Registry (VCOR). We linked this dataset to the Ambulance Victoria and National Death Index (NDI) datasets. We excluded late presentation, thrombolysed, and in-hospital STEMI, as well as patients presenting with cardiogenic shock and out-of-hospital cardiac arrest. RESULTS: In total, 74% of patients undergoing primary PCI for STEMI used EMS. Older age, female gender, higher socioeconomic status, and a history of prior ischaemic heart disease were independent predictors of using EMS. EMS use was associated with shorter adjusted door-to-balloon (53 vs 72 minutes, p<0.001) and symptom-to-balloon (183 vs 212 minutes, p<0.001) times. Mode of transport was not predictive of 30-day or 12-month mortality. CONCLUSIONS: EMS use in Victoria is relatively high compared with internationally reported data. EMS use reduces treatment delay. Predictors of EMS use in our cohort are consistent with those prevalent in prior literature. Understanding the patients who are less likely to use EMS might inform more targeted education campaigns in the future.

Identifying areas of Australia with high out-of-hospital cardiac arrest incidence and low bystander cardiopulmonary resuscitation rates: A retrospective, observational study.

AIM: This study aims to explore regional variation and identify regions within Australia with high incidence of out-of-hospital cardiac arrest (OHCA) and low rates of bystander cardiopulmonary resuscitation (CPR). METHOD: Adult OHCAs of presumed medical aetiology occurring across Australia between 2017 and 2019 were mapped onto local government areas (LGA) using the location of arrest coordinates. Bayesian spatial models were applied to provide "smoothed" estimates of OHCA incidence and bystander CPR rates (for bystander-witnessed OHCAs) for each LGA. For each state and territory, high-risk LGAs were defined as those with an incidence rate greater than the state or territory's 75th percentile and a bystander CPR rate less than the state or territory's 25th percentile. RESULTS: A total of 62,579 OHCA cases attended by emergency medical services across 543 LGAs nationwide were included in the study. Nationally, the OHCA incidence rate across LGA ranged from 58.5 to 198.3 persons per 100,000, while bystander CPR rates ranged from 45% to 75%. We identified 60 high-risk LGAs, which were predominantly located in the state of New South Wales. Within each region, high-risk LGAs were typically located in regional and remote areas of the country, except for four metropolitan areas-two in Adelaide and two in Perth. CONCLUSIONS: We have identified high-risk LGAs, characterised by high incidence and low bystander CPR rates, which are predominantly in regional and remote areas of Australia. Strategies for reducing OHCA and improving bystander response may be best targeted at these regions.

Healthcare and economic cost burden of emergency medical services treated non-traumatic shock using a population-based cohort in Victoria, Australia.

OBJECTIVES: We aimed to assess the healthcare costs and impact on the economy at large arising from emergency medical services (EMS) treated non-traumatic shock. DESIGN: We conducted a population-based cohort study, where EMS-treated patients were individually linked to hospital-wide and state-wide administrative datasets. Direct healthcare costs (Australian dollars, AUD) were estimated for each element of care using a casemix funding method. The impact on productivity was assessed using a Markov state-transition model with a 3-year horizon. SETTING: Patients older than 18 years of age with shock not related to trauma who received care by EMS (1 January 2015-30 June 2019) in Victoria, Australia were included in the analysis. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome assessed was the total healthcare expenditure. Secondary outcomes included healthcare expenditure stratified by shock aetiology, years of life lived (YLL), productivity-adjusted life-years (PALYs) and productivity losses. RESULTS: A total of 21 334 patients (mean age 65.9 (±19.1) years, and 9641 (45.2%) females were treated by EMS with non-traumatic shock with an average healthcare-related cost of $A11 031 per episode of care and total cost of $A280 million. Annual costs remained stable throughout the study period, but average costs per episode of care increased (Ptrend=0.05). Among patients who survived to hospital, the average cost per episode of care was stratified by aetiology with cardiogenic shock costing $A24 382, $A21 254 for septic shock, $A19 915 for hypovolaemic shock and $A28 057 for obstructive shock. Modelling demonstrated that over a 3-year horizon the cohort lost 24 355 YLLs and 5059 PALYs. Lost human capital due to premature mortality led to productivity-related losses of $A374 million. When extrapolated to the entire Australian population, productivity losses approached $A1.5 billion ($A326 million annually). CONCLUSION: The direct healthcare costs and indirect loss of productivity among patients with non-traumatic shock are high. Targeted public health measures that seek to reduce the incidence of shock and improve systems of care are needed to reduce the financial burden of this syndrome.

Refining ambulance clinical response models: The impact on ambulance response and emergency department presentations.

OBJECTIVE: The ambulance service in Victoria, Australia implemented a revised clinical response model (CRM) in 2016 which was designed to increase the diversion of low-acuity Triple Zero (000) calls to secondary telephone triage and reduce emergency ambulance dispatches. The present study evaluates the influence of the revised CRM on emergency ambulance response times and ED presentations. METHODS: A retrospective study of emergency calls for ambulance between 1 January 2015 and 31 December 2018. Ambulance data were linked with ED presentations occurring up to 48 h after contact. Interrupted time series analyses were used to evaluate the impact of the revised CRM. RESULTS: A total of 2 365 529 calls were included. The proportion allocated a Code 1 (time-critical, lights/sirens) dispatch decreased from 56.6 to 41.0% after implementation of the revised CRM. The proportion of calls not receiving an emergency ambulance increased from 10.4 to 19.6%. Interrupted time series analyses demonstrated an improvement in Code 1 cases attended within 15 min (Key Performance Indicator). However, for patients with out-of-hospital cardiac arrest or requiring lights and sirens transport to hospital, there was no improvement in response time performance. By the end of the study period, there was also no difference in the proportion of callers presenting to ED when compared with the estimated proportion assuming the revised CRM had not been implemented. CONCLUSION: The revised CRM was associated with improved Code 1 response time performance. However, there was no improvement in response times for high acuity patients, and no change in the proportion of callers presenting to ED.

Temporal trends in the incidence and outcomes of shock-refractory ventricular fibrillation out-of-hospital cardiac arrest.

Aim: We aimed to describe trends in the incidence and outcomes of refractory ventricular fibrillation (RVF) compared to non-refractory ventricular fibrillation (non-RVF) in out-of-hospital cardiac arrest (OHCA). Methods: Between 2010 and 2019, we included all OHCA cases involving adults ≥ 16 years old with an initial shockable rhythm and who received an attempted resuscitation by Emergency Medical Services (EMS) or a bystander shock prior to EMS arrival in Victoria, Australia. Trends in incidence and survival outcomes over the study period were examined. Adjusted logistic regression analyses were conducted to examine factors associated with RVF, as well as the association of RVF on survival to hospital discharge. RVF refers to patients receiving three or more consecutive shocks without a return of spontaneous circulation (ROSC). Results: Of the 57,749 OHCA attended by EMS, 7,267 met the inclusion criteria. Of these, 4,168 (57.4%) were non-RVF and 3,099 (42.6%) were RVF. The incidence of RVF decreased significantly from 7.7 per 100,000 population in 2010 to 5.6 per 100,000 population in 2019 (p-trend = 0.01). Survival to hospital discharge increased significantly for both the RVF and non-RVF groups (26% vs 41% in 2010 to 31% vs 53% in 2019, p-trend = 0.004 for RVF; and p-trend = 0.01 for non-RVF). Compared to non-RVF, RVF was associated with reduced odds of survival to hospital discharge (Odds Ratio = 0.503 [95% confidence interval 0.448 - 0.565]). Factors associated with a lower likelihood of RVF and improved survival to hospital discharge included being witnessed to arrest by EMS, receiving bystander defibrillation and bystander cardiopulmonary resuscitation (CPR). Conclusion: The incidence of RVF is declining, and survival rates are improving. Early treatment of VF patients with bystander CPR and defibrillation is likely to reduce RVF incidence.

Using ambulance surveillance data to characterise blood-borne viral infection histories among patients presenting with acute alcohol and other drug-related harms.

OBJECTIVE: Preventable transmission of blood-borne viruses (BBV), including human immunodeficiency virus (HIV), hepatitis C virus (HCV) and hepatitis B virus (HBV), continue in at-risk populations, including people who use alcohol and drugs (AODs). To our knowledge, no studies have explored the use of ambulance data for surveillance of AOD harms in patients with BBV infections. METHODS: We used electronic patient care records from the National Ambulance Surveillance System for people who were attended by an ambulance in Victoria, Australia between July 2015 and July 2016 for AOD-related harms, and with identified history of a BBV infection. Descriptive and geospatial analyses explored the epidemiological and psychosocial characteristics of patients for these attendances. RESULTS: The present study included 1832 patients with a history of a BBV infection who required an ambulance for AOD-related harms. Amphetamines were reported in 24.7% of attendances where the patient identified HIV history, and heroin was reported more often for patients with viral hepatitis history (HCV: 19.2%; HBV: 12.7%). Higher proportions of attendances with a viral hepatitis history were observed in patients from the most socially disadvantaged areas. Geospatial analyses revealed higher concentrations of AOD attendances with a BBV history occurring in metropolitan Melbourne. CONCLUSIONS: Our study describes the utility of ambulance data to identify a sub-population of patients with a BBV history and complex medical and social characteristics. Repeat attendances of BBV history patients to paramedics could present an opportunity for ongoing surveillance using ambulance data and possible paramedic intervention, with potential linkage to appropriate BBV services.

Adolescent Suicidal Behaviors During the COVID-19 Pandemic in Australia: Analysis of Acute Harms Assessed via Ambulance Data.

PURPOSE: This study investigated changes in suicidal ideation, attempts, and nonsuicidal self-injury (NSSI)-related ambulance attendances among adolescents during the COVID-19 pandemic. METHODS: An interrupted time series analysis using data from the National Ambulance Surveillance System, a globally unique mental health and suicide surveillance system. Patients aged 12-17 years from the state of Victoria, Australia who were attended by ambulance for suicide attempts, suicide ideation, and NSSI between January 2016 and October 2021 were included. Monthly ambulance attendances during the pre-COVID period (January 2016-March 2020) were compared to those in the peak period of COVID-19 (April 2020-October 2021). RESULTS: There were 20,125 ambulance attendances for suicide ideation, suicide attempt, and NSSI in adolescents over the study period. During the pre-COVID period, the number of suicide ideation, attempts, and NSSI attendances was increasing by 1.1% per month (incidence rate ratio [IRR]:1.011; 95% confidence interval [1.009-1.013], p < .001). There was no change in the rate of all suicide ideation, attempt, and NSSI for all adolescents during the period of COVID-19. However, when disaggregated by gender, there was a 0.7% increase in the monthly rate of attendances for females (IRR: 1.007 [1.001-1.013], p = .029), and a 3.0% decrease for males (IRR: 0.970 [0.964-0.975], p < .001). DISCUSSION: Adolescent female suicide ideation, attempt, and NSSI attendances increased during the COVID-19 period, compared with males in the same time period. These findings suggest tailored intervention strategies may be needed to address the increasing trends of self-harm among young people.

Sex disparities in bystander defibrillation for out-of-hospital cardiac arrest.

Background: Previous studies have suggested that females experiencing out-of-hospital cardiac arrest (OHCA) receive lower rates of both bystander cardiopulmonary resuscitation (CPR) and defibrillation compared to males. Whether this disparity has improved over time is unknown. Methods: A state-wide OHCA registry in Victoria, Australia collected data over twenty years (2002-2021) regarding rates of bystander interventions in OHCA. Characteristics and outcomes of each OHCA were compared with logistic regression according to sex and time (defined in two-year periods). Results: 32,502 OHCAs were included (69.7% male). Both bystander CPR and defibrillation rates increased for females over time (p < 0.0001). There was no sex disparity in receipt of bystander CPR after adjustment for baseline differences. Females were less likely than males to receive bystander defibrillation, with sex disparity increasing from 2010 onwards (adjOR 0.26 (95%CI 0.09-0.80) in 2020-21 for females compared to males). Conclusion: Initiatives to increase bystander CPR and defibrillation have resulted in higher overall rates of bystander interventions in the last two decades and no significant sex differences in provision of bystander CPR. However, females receive less bystander defibrillation than males, and sex disparity is increasing. Strategies to promote bystander defibrillation in females experiencing OHCA with a shockable rhythm should be a priority.

Impact of socioeconomic status on presentation, care quality and outcomes of patients attended by emergency medical services for dyspnoea: a population-based cohort study.

BACKGROUND: Low socioeconomic status (SES) has been linked to poor outcomes in many conditions. It is unknown whether these disparities extend to individuals presenting with dyspnoea. We aimed to evaluate the relationship between SES and incidence, care quality and outcomes among patients attended by emergency medical services (EMS) for dyspnoea. METHODS: This population-based cohort study included consecutive patients attended by EMS for dyspnoea between 1 January 2015 and 30 June 2019 in Victoria, Australia. Data were obtained from individually linked ambulance, hospital and mortality datasets. Patients were stratified into SES quintiles using a composite census-derived index. RESULTS: A total of 262 412 patients were included. There was a stepwise increase in the age-adjusted incidence of EMS attendance for dyspnoea with increasing socioeconomic disadvantage (lowest SES quintile 2269 versus highest quintile 889 per 100 000 person years, ptrend<0.001). Patients of lower SES were younger and more comorbid, more likely to be from regional Victoria or of Aboriginal or Torres Strait Islander heritage and had higher rates of respiratory distress. Despite this, lower SES groups were less frequently assigned a high acuity EMS transport or emergency department (ED) triage category and less frequently transported to tertiary centres or hospitals with intensive care unit facilities. In multivariable models, lower SES was independently associated with lower acuity EMS and ED triage, ED length of stay>4 hours and increased 30-day EMS reattendance and mortality. CONCLUSION: Lower SES was associated with a higher incidence of EMS attendances for dyspnoea and disparities in several metrics of care and clinical outcomes.

Association of socioeconomic status in the incidence, quality-of-care metrics, and outcomes for patients with cardiogenic shock in a pre-hospital setting.

AIMS: The relationship between lower socioeconomic status (SES) and poor cardiovascular outcomes is well described; however, there exists a paucity of data exploring this association in cardiogenic shock (CS). This study aimed to investigate whether any disparities exist between SES and the incidence, quality of care or outcomes of CS patients attended by emergency medical services (EMS). METHODS AND RESULTS: This population-based cohort study included consecutive patients transported by EMS with CS between 1 January 2015 and 30 June 2019 in Victoria, Australia. Data were collected from individually linked ambulance, hospital, and mortality datasets. Patients were stratified into SES quintiles using national census data produced by the Australian Bureau of Statistics.A total of 2628 patients were attended by EMS for CS. The age-standardized incidence of CS amongst all patients was 11.8 [95% confidence interval (95% CI), 11.4-12.3] per 100 000 person-years, with a stepwise increase from the highest to lowest SES quintile (lowest quintile 17.0 vs. highest quintile 9.7 per 100 000 person-years, P-trend < 0.001). Patients in lower SES quintiles were less likely to attend metropolitan hospitals and more likely to be received by inner regional and remote centres without revascularization capabilities. A greater proportion of the lower SES groups presented with CS due to non-ST elevation myocardial infarction (NSTEMI) or unstable angina pectoris (UAP), and overall were less likely to undergo coronary angiography. Multivariable analysis demonstrated an increased 30-day all-cause mortality rate in the lowest three SES quintiles when compared with the highest quintile. CONCLUSION: This population-based study demonstrated discrepancies between SES status in the incidence, care metrics, and mortality rates of patients presenting to EMS with CS. These findings outline the challenges in equitable healthcare delivery within this cohort.