Swedish Register Of Cardiopulmonary Resuscitation Research Articles

Survival in relation to number of defibrillation attempts in out-of-hospital cardiac arrest.

Out-of-hospital cardiac arrest (OHCA) with shockable pulseless ventricular tachycardia or fibrillation not responding to defibrillation is a medical challenge. Novel treatment strategies have emerged for so-called refractory ventricular fibrillation not responding to three or more defibrillations but the evidence for optimal timing for these strategies is sparse. The primary aim of this observational study was to assess survival in relation to total numbers of defibrillations in OHCA. This is a registry-based retrospective cohort study based on data reported by the emergency medical services to the Swedish Registry of Cardiopulmonary Resuscitation and the National Patient Registry. All OHCA patients aged 18 years or older with an initial shockable rhythm in Sweden from January 1, 2010 and December 31, 2020 were included. Exposure was total number of defibrillations, and primary outcome was survival to 30 days. Logistic regression was used to adjust for patient and resuscitation characteristics. Over the study period a total of 10,549 patients were included. Among them, 3,006 (28.5%) received only one shock, 1,665 (15.8%) two shocks, 1,336 (12.9%) three shocks, 1,064 (10.1%) four shocks and 3,478 (33.0%) five or more shocks. In the adjusted analysis an exponential decrease in the 30-day survival was found for each additional defibrillation. For patients receiving one, two, three and four defibrillations, the adjusted probability of survival was 42%, 36%, 30% and 25% respectively. In this registry-based retrospective cohort study, additional defibrillations were associated with a lower survival. This association persisted after adjustments for patient and resuscitation characteristics.

Prediction of neurologic outcome after out-of-hospital cardiac arrest: An interpretable approach with machine learning

Out-of-hospital cardiac arrest (OHCA) is a critical condition with low survival rates. In patients with a return of spontaneous circulation, brain injury is a leading cause of death.In this study, we propose an interpretable machine learning approach for predicting neurologic outcome after OHCA, using information available at the time of hospital admission. MethodsThe study population were 55 615 OHCA cases registered in the Swedish Cardiopulmonary Resuscitation Registry between 2010 and 2020. The dataset was split to training and validation sets (for model development) and test set (for evaluation of the final model). We used an XGBoost algorithm with stratified, repeated 10-fold cross-validation along with Optuna framework for hyperparameters tuning. The final model was trained on 10 features selected based on the importance scores and evaluated on the test set in terms of discrimination, calibration and bias-variance tradeoff. We used SHapley Additive exPlanations to address the ‘black-box’ model and align with eXplainable artificial intelligence. ResultsThe final model achieved: area under the receiver operating characteristic value 0.964 (95% confidence interval (CI) [0.960–0.968]), sensitivity 0.606 (95% CI [0.573–0.634]), specificity 0.975 (95% CI [0.972–0.978]), positive predictive value (PPV) 0.664 (95% CI [0.625–0.696]), negative predictive value (NPV) 0.969 (95% CI [0.966–0.972]), macro F1 0.803 (95% CI [0.788–0.816]), and showed a very good calibration. SHAP features with the highest impact on the model’s output were:’ROSC on arrival to hospital’, ‘Initial rhythm asystole’ and ‘Conscious on arrival to hospital’. ConclusionsThe XGBoost machine learning model with 10 features available at the time of hospital admission showed good performance for predicting neurologic outcome after OHCA, with no apparent signs of overfitting.

Aetiology and predictors of outcome in non-shockable in-hospital cardiac arrest: A retrospective cohort study from the Swedish Registry for Cardiopulmonary Resuscitation.

Non-shockable in-hospital cardiac arrest (IHCA) is a condition with diverse aetiology, predictive factors, and outcome. This study aimed to compare IHCA with initial asystole or pulseless electrical activity (PEA), focusing specifically on their aetiologies and the significance of predictive factors. Using the Swedish Registry of Cardiopulmonary Resuscitation, adult non-shockable IHCA cases from 2018 to 2022 (n = 5788) were analysed. Exposure was initial rhythm, while survival to hospital discharge was the primary outcome. A random forest model with 28 variables was used to generate permutation-based variable importance for outcome prediction. Overall, 60% of patients (n = 3486) were male and the median age was 75 years (IQR 67-81). The most frequent arrest location (46%) was on general wards. Comorbidities were present in 79% of cases and the most prevalent comorbidity was heart failure (33%). Initial rhythm was PEA in 47% (n = 2702) of patients, and asystole in 53% (n = 3086). The most frequent aetiologies in both PEA and asystole were cardiac ischemia (24% vs. 19%, absolute difference [AD]: 5.4%; 95% confidence interval [CI] 3.0% to 7.7%), and respiratory failure (14% vs. 13%, no significant difference). Survival was higher in asystole (24%) than in PEA (17%) (AD: 7.3%; 95% CI 5.2% to 9.4%). Cardiopulmonary resuscitation (CPR) durations were longer in PEA, 18 vs 15 min (AD 4.9 min, 95% CI 4.0-5.9 min). The duration of CPR was the single most important predictor of survival across all subgroup and sensitivity analyses. Aetiology ranked as the second most important predictor in most analyses, except in the asystole subgroup where responsiveness at cardiac arrest team arrival took precedence. In this nationwide registry study of non-shockable IHCA comparing asystole to PEA, cardiac ischemia and respiratory failure were the predominant aetiologies. Duration of CPR was the most important predictor of survival, followed by aetiology. Asystole was associated with higher survival compared to PEA, possibly due to shorter CPR durations and a larger proportion of reversible aetiologies.

Effects of pre-existing type 1 diabetes mellitus on survival outcome following out-of-hospital cardiac arrest: a registry-based observational study in Sweden

BackgroundIt has been estimated that 80% of cases of out-of-hospital cardiac arrest (OHCA) are due to cardiac causes. It is well-documented that diabetes is a risk factor for conditions associated...

Neurological function before and after an in-hospital cardiac arrest – A nationwide registry-based cohort study

BackgroundAccording to the Utstein Registry Template for in-hospital cardiac arrest (IHCA), a good neurological outcome is defined as either Cerebral Performance Category (CPC) 1–2 at discharge from hospital or unchanged CPC compared to baseline. However, the latter alternative has rarely been described in IHCA. This study aimed to examine CPC at admission to hospital, the occurrence of post-arrest neurological deterioration, and the factors associated with such deterioration. MethodsWe studied adult IHCA survivors registered in the Swedish Registry of Cardiopulmonary Resuscitation between 2007 and 2022. The CPC was assessed based on information from admission and discharge from hospital. The data were analyzed using descriptive statistics and significance tests. ResultsOne in ten IHCA had a CPC score > 1 at admission to hospital. Out of 7,677 IHCA who survived until hospital discharge and had full CPC data, 6,774 (88%) had preserved CPC, 150 (2%) had improved CPC, and 753 (10%) had deteriorated CPC. Among the factors significantly associated with deteriorated neurological function are IHCA in a general ward or intensive care unit, non-shockable rhythm, no ECG surveillance, and a higher proportion of intra-arrest and post-resuscitation treatments (all p-values < 0,05). ConclusionMost patients had preserved neurological function compared to admission. Factors associated with deteriorated neurological function are mainly concordant with established risk factors for adverse outcomes and are primarily intra-arrest and post-resuscitation, making deterioration hard to predict. Further, every tenth survivor was admitted with CPC more than 1, stressing the use of unchanged CPC as an outcome in IHCA.

Associations between initial heart rhythm and self-reported health among cardiac arrest survivors − A nationwide registry study

BackgroundNon-shockable initial rhythm is a known risk factor for high mortality at cardiac arrest (CA). However, knowledge on its association with self-reported health in CA survivors is still incomplete. AimTo examine the associations between initial rhythm and self-reported health in CA survivors. MethodsThis nationwide study used data from the Swedish Register for Cardiopulmonary Resuscitation 3–6 months post CA. Health status was measured using EQ-5D-5L and psychological distress by the Hospital Anxiety and Depression Scale (HADS). Kruskal-Wallis test was used to examine differences in self-reported health between groups of different initial rhythms. To control for potential confounders, age, sex, place of CA, aetiology, witnessed status, time to CPR, time to defibrillation, and neurological function were included as covariates in multiple regression analyses for continuous and categorical outcomes. ResultsThe study included 1783 adult CA survivors. Overall, the CA survivors reported good health status and symptoms of anxiety or depression were uncommon (13.7% and 13.9% respectively). Survivors with PEA and asystole reported significantly more problems in all dimensions of health status (p = 0.037 to p < 0.001), anxiety (p = 0.034), and depression (p = 0.017) compared to VT/VF. Overall, these differences did not remain in the adjusted regression analyses. ConclusionsInitial rhythm is not associated with self-reported health when potential confounders are controlled. Initial rhythm seems to be an indicator of unfavourable factors causing the arrest, or factors related to characteristics and treatment. Therefore, initial rhythm may be used as a proxy for identifying patients at risk for poor outcomes such as worse health status and psychological distress.

Underlying reasons for sex difference in survival following out-of-hospital cardiac arrest: a mediation analysis.

Previous studies have indicated a poorer survival among women following out-of-hospital cardiac arrest (OHCA), but the mechanisms explaining this difference remain largely uncertain.This study aimed to assess the survival after OHCA among women and men and explore the role of potential mediators, such as resuscitation characteristics, prior comorbidity, and socioeconomic factors. This was a population-based cohort study including emergency medical service-treated OHCA reported to the Swedish Registry for Cardiopulmonary Resuscitation in 2010-2020, linked to nationwide Swedish healthcare registries. The relative risks (RR) of 30-day survival were compared among women and men, and a mediation analysis was performed to investigate the importance of potential mediators. Total of 43 226 OHCAs were included, of which 14 249 (33.0%) were women. Women were older and had a lower proportion of shockable initial rhythm. The crude 30-day survival among women was 6.2% compared to 10.7% for men [RR 0.58, 95% confidence interval (CI) = 0.54-0.62]. Stepwise adjustment for shockable initial rhythm attenuated the association to RR 0.85 (95% CI = 0.79-0.91). Further adjustments for age and resuscitation factors attenuated the survival difference to null (RR 0.98; 95% CI = 0.92-1.05). Mediation analysis showed that shockable initial rhythm explained ∼50% of the negative association of female sex on survival. Older age and lower disposable income were the second and third most important variables, respectively. Women have a lower crude 30-day survival following OHCA compared to men. The poor prognosis is largely explained by a lower proportion of shockable initial rhythm, older age at presentation, and lower income.

Prediction of survival in out-of-hospital cardiac arrest: the updated Swedish cardiac arrest risk score (SCARS) model.

Out-of-hospital cardiac arrest (OHCA) is a major health concern worldwide. Although one-third of all patients achieve a return of spontaneous circulation and may undergo a difficult period in the intensive care unit, only 1 in 10 survive. This study aims to improve our previously developed machine learning model for early prognostication of survival in OHCA. We studied all cases registered in the Swedish Cardiopulmonary Resuscitation Registry during 2010 and 2020 (n = 55 615). We compared the predictive performance of extreme gradient boosting (XGB), light gradient boosting machine (LightGBM), logistic regression, CatBoost, random forest, and TabNet. For each framework, we developed models that optimized (i) a weighted F1 score to penalize models that yielded more false negatives and (ii) a precision-recall area under the curve (PR AUC). LightGBM assigned higher importance values to a larger set of variables, while XGB made predictions using fewer predictors. The area under the curve receiver operating characteristic (AUC ROC) scores for LightGBM were 0.958 (optimized for weighted F1) and 0.961 (optimized for a PR AUC), while for XGB, the scores were 0.958 and 0.960, respectively. The calibration plots showed a subtle underestimation of survival for LightGBM, contrasting with a mild overestimation for XGB models. In the crucial range of 0-10% likelihood of survival, the XGB model, optimized with the PR AUC, emerged as a clinically safe model. We improved our previous prediction model by creating a parsimonious model with an AUC ROC at 0.96, with excellent calibration and no apparent risk of underestimating survival in the critical probability range (0-10%). The model is available at www.gocares.se.

Early ICD implantation following out-of-hospital cardiac arrest: a retrospective cohort study from the Swedish Registry for Cardiopulmonary Resuscitation

BackgroundIt is unclear whether an implantable cardioverter-defibrillator (ICD) is generally beneficial in survivors of out-of-hospital cardiac arrest (OHCA).ObjectiveWe studied the association between ICD implantation prior to discharge and survival in...

Compliance with cardiopulmonary resuscitation guidelines in witnessed in-hospital cardiac arrest events and patient outcome on monitored versus non-monitored wards

BackgroundAdherence to cardiopulmonary resuscitation (CPR) guidelines in treatment of in-hospital cardiac arrest (IHCA) have been associated with favourable patient outcome. The aim of this study was to evaluate if compliance with initial CPR guidelines and patient outcome of witnessed IHCA events were associated with the place of arrest defined as monitored versus non-monitored ward. MethodsA total of 956 witnessed IHCA events in adult patients at six hospitals during 2018 to 2019, were extracted from the Swedish Registry of Cardiopulmonary Resuscitation. Initial CPR guidelines were: ≤1 min from collapse to alert of the rapid response team, ≤1 min from collapse to start of CPR, ≤3 min from collapse to defibrillation of shockable rhythm. ResultsThe odds of compliance with guidelines was higher on monitored wards vs non-monitored wards, even after adjustment for factors that could affect staffing and resources. The place of arrest was not a significant factor for sustained return of spontaneous circulation, survival at 30 days, or neurological status at discharge, when adjusting for clinically relevant confounders. Compliance with initial CPR guidelines remained a significant factor for survival to 30 days and favourable neurological outcome at discharge regardless of other confounders. ConclusionCompliance with initial CPR guidelines was higher in witnessed IHCA events on monitored wards than on non-monitored wards, which indicates that healthcare professionals in monitored wards are quicker to recognize a cardiac arrest and initiate treatment. When initial CPR guidelines are followed, the place of arrest does not influence patient outcome.

Incidence and case ascertainment of treated in-hospital cardiac arrest events in a national quality registry – A comparison of reported and non-reported events

BackgroundApproximately 2500 in-hospital cardiac arrest (IHCA) events are reported annually to the Swedish Registry of Cardiopulmonary Resuscitation (SRCR) with an estimated incidence of 1.7/1000 hospital admissions. The aim of this study was to evaluate the compliance in reporting IHCA events to the SRCR and to compare reported IHCA events with possible non-reported events, and to estimate IHCA incidence. MethodsFifteen diagnose codes, eight Classification of Care Measure codes, and two perioperative complication codes were used to find all treated IHCAs in 2018–2019 at six hospitals of varying sizes and resources. All identified IHCA events were cross-checked against the SRCR using personal identity numbers. All non-reported IHCA events were retrospectively reported and compared with the prospectively reported events. ResultsA total of 3638 hospital medical records were reviewed and 1109 IHCA events in 999 patients were identified, with 254 of the events not found in the SRCR. The case completeness was 77% (range 55–94%). IHCA incidence was 2.9/1000 hospital admissions and 12.4/1000 admissions to intensive care units. The retrospectively reported events were more often found on monitored wards, involved patients who were younger, had less comorbidity, were often found in shockable rhythm and more often achieved sustained spontaneous circulation, compared with in prospectively reported events. ConclusionIHCA case completeness in the SRCR was 77% and IHCA incidence was 2.9/1000 hospital admissions. The retrospectively reported IHCA events were found in monitored areas where the rapid response team was not alerted, which might have affected regular reporting procedures.

Out-of-hospital cardiac arrest: Survival in children and young adults over 30 years, a nationwide registry-based cohort study

ObjectivesWe studied short-term (30-day) and long-term (up to ten-year) survival among children and young adults following out-of-hospital cardiac arrest (OHCA) in Sweden over the course of the past 30 years. We also studied the causes of OHCA in children and examined predictors of survival. SettingThis was a nationwide, registry-based cohort study, using the Swedish Registry of Cardiopulmonary Resuscitation. Our study comprised a cohort of 4,804 individuals aged 0 to 30 years who suffered OHCA between 1990 and 2020, in whom cardiopulmonary resuscitation (CPR) was initiated. We stratified the study cohort to distinct age groups and time periods. ResultsWe found an increase in 30-day survival from 7% to 20% over the span of 30 years. In those under 1 year of age, survival increased from 2% to 19%. Time to CPR decreased from 14 to 2 min. The 10-year survival was high among those who survived 30 days. The etiology of cardiac arrests exhibited significant variations across different age groups but remained relatively consistent over time. Causes linked to mental illness constituted a substantial percentage of these cases. Compared to the reference period (1990–1994), the odds of survival in 2015–2020 was 3.00 (95% CI: 1.43, 6.94; p = 0.006). ConclusionSurvival rate after OHCA in children and young adults has increased three-fold over the past 30 years. Still overall mortality is high underscoring the need for continued efforts to mitigate risk factors and optimize survival.

Characteristics, survival and neurological outcome in out-of-hospital cardiac arrest in young adults in Sweden: A nationwide study

AimThe aim of this study was to present a comprehensive overview of out-of-hospital cardiac arrests (OHCA) in young adults. MethodsThe data set analyzed included all cases of OHCA from 1990 to 2020 in the age-range 16–49 years in the Swedish Registry of Cardiopulmonary Resuscitation (SRCR). OHCA between 2010 and 2020 were analyzed in more detail. Clinical characteristics, survival, neurological outcomes, and long-time trends in survival were studied. Logistic regression was used to study 30-days survival, neurological outcomes and Utstein determinants of survival. ResultsTrends were assessed in 11,180 cases. The annual increase in 30-days survival during 1990–2020 was 5.9% with no decline in neurological function among survivors. Odds ratio (OR) for heart disease as the cause was 0.55 (95% CI 0.44 to 0.67) in 2017–2020 compared to 1990–1993. Corresponding ORs for overdoses and suicide attempts were 1.61 (95% CI 1.23–2.13) and 2.06 (95% CI 1.48–2.94), respectively. Exercise related OHCA was noted in roughly 5%. OR for bystander CPR in 2017–2020 vs 1990–1993 was 3.11 (95% CI 2.57 to 3.78); in 2020 88 % received bystander CPR. EMS response time increased from 6 to 10 minutes. ConclusionSurvival has increased 6% annually, resulting in a three-fold increase over 30 years, with stable neurological outcome. EMS response time increased with 66% but the majority now receive bystander CPR. Cardiac arrest due to overdoses and suicide attempts are increasing.

Early ICD implantation and survival after out-of-hospital cardiac arrest

Abstract Background It is unclear whether an implantable cardioverter-defibrillator (ICD) is generally beneficial in survivors of out-of-hospital cardiac arrest (OHCA) of cardiac etiology. Aim We studied the association between ICD implantation and survival in patients with cardiac etiology or initial shockable rhythm in OHCA, using the Swedish Registry for Cardiopulmonary Resuscitation (SRCR). Methods All cases in the SRCR during 2010 to 2020 with cardiac etiology or initial shockable rhythm who were discharged alive included. We examined the association between ICD and survival using propensity score. Propensity scores (919 candidate predictors before feature selection) were estimated using gradient boosting, Bayesian additive regression trees, neural networks, extreme gradient boosting and logistic regression. Cox regression was used to model survival. The primary outcome was death or recurrent cardiac arrest. Results The 90-days event rate was 25% in the ICD group, compared with 52% in those without ICD. With regards to the average treatment effect (ATE) the overall hazard ratio 0.38 (95% CI 0.26-0.56) for ICD vs. no ICD. The overall average treatment effect on those treated (ATT) was 0.31 (95% CI 0.22-0.44). In the 15 subgroup analyses, every point estimate were below 1, with the most pronounced association noted in those with a history of acute myocardial infarction (HR 0.07 [95% CI 0.02-0.32]). All ATE and ATE estimates were aligned. Conclusions Mortality in survivors of OHCA occurs early after discharge, and prompt implantation of an ICD is associated with 62% lower probability of death and recurrent cardiac arrest overall.

Exploring underlying reasons for the difference in sex-specific survival following out-of-hospital cardiac arrest - a mediation analysis

Abstract Background Previous studies have indicated a poorer survival among women following out-of-hospital cardiac arrest (OHCA), but the mechanisms explaining this difference remains largely uncertain. This study aimed to assess the survival after OHCA among women men and explore the role of potential mediators, such as resuscitation characteristics, prior comorbidity, and socioeconomic factors. Methods This was a population-based cohort study including all emergency medical service-treated OHCA reported to the Swedish Registry for Cardiopulmonary Resuscitation in 2010-2020, linked to nationwide Swedish healthcare registries. The relative risks (RR) of 30-day survival were compared among women (exposure) and men (comparison) using modified Poisson regression and third variable effect analysis to investigate the importance of potential mediators in a stepwise approach. Results A total of 43,226 OHCAs were included, of which 14,249 (33.0%) were women. The crude 30-day survival among women was 6.2% compared to 10.6% for men (RR 0.58, 95% CI=0.54-0.62). Stepwise adjustment for shockable initial rhythm attenuated the association to RR 0.85 (95% CI=0.80-0.92), and further adjustments for age and resuscitation factors (witness status, emergency medical service response time, and location) attenuated the survival difference between sexes to null (RR 0.98; 95% CI=0.92-1.05). Third variable effect analysis showed that shockable initial rhythm explained approximately 50% of the negative association of female sex on survival. Older age and lower disposable income were the second and third most important variables. Previously known comorbidities explained only a very small portion of the sex difference in survival. Conclusion Women have a lower 30-day survival following OHCA compared to men. The poor prognosis is largely explained by the absence of shockable initial rhythm, older age at presentation and lower disposable income.Results from regression analyses

Abstract 412: Targeted Temperature Management for Patients With Out of Hospital Cardiac Arrest: A Comparison of the TTM2 Trial Population With Real World Data

Introduction: The TTM2 trial demonstrated no improvement of the functional status in survivors of Out-of-Hospital Cardiac Arrest (OHCA). However, the external validitiy of the trial remains to be investigated. Aim: We aimed to compare the patient population of the TTM2 trial to the real world data. Methods: We obtained the data from multiple national registries including Cardiac Arrest Registry to Enhance Survival (CARES), the Australasian Resuscitation Outcomes Consortium (Aus-ROC), the Danish Cardiac Arrest Registry (DCAR), and the Swedish Cardiopulmonary Resuscitation Registry (SCRR). We pooled the data from these registries and compared them to the data from the TTM2 trial. Results: We identified a total of 262,482 encounters from all the databases and 1,861 encounters from the TTM2 trial. The average age was comparable between both groups (64 years), females gender (registries 35% vs trial 20%), arrest event happened at the place of residence (registries 72% vs trial 53%), Bystander-witnessed arrest (registries 57% vs trial 91%), Bystander-performed CPR (registries 38% vs trial 80%), initial shockable rhythm (registries 25% vs trial 74%), non-shockable rhythm (registries 75% vs trial 26%). Conclusion: Large discrepancies were identified between the data from the TTM2 and the pooled data obtained from multiple registries. This needs to be further investigated.

In-hospital cardiac arrest due to sepsis – Aetiologies and outcomes in a Swedish cohort study

ObjectivesAwareness of causes of cardiac arrest is essential to prevent them. A recent review found that almost every sixth in-hospital cardiac arrest is caused by infection. Few studies have explored how infections cause cardiac arrest. AimTo describe the features, mechanisms and outcome of sepsis-related cardiac arrests. Material and methodsAll patients ≥18 years who suffered a cardiac arrest at Karolinska University Hospital between 2007 and 2022 with sepsis as the primary cause were included. Data were collected the Swedish Registry for Cardiopulmonary Resuscitation and medical records. The primary outcome was survival to discharge. ResultsOut of 2,327 in-hospital cardiac arrests, 5% (n = 123) suffered it due to sepsis, and 17% (21) survived to hospital discharge. Two thirds of patients were admitted to the hospital due to sepsis and suffered their cardiac arrest after a median of four days. About half (n = 59) had deranged vital signs before the event. Most were witnessed in general wards. In all, 47% (n = 58) had asystole and 24% (n = 30) as the first heart rhythm. The respiratory tract was the most common source of infection. Most patients were undergoing antibiotic therapy and one third had a positive microbiological culture with mixed gram-positive bacteria or Escherichia coli in the urine. ConclusionOur results suggest that sepsis is an uncommon and not increasing cause of in-hospital cardiac arrest and its outcome is in line with other non-shockable cardiac arrests. Deranged respiratory and/or circulatory vital signs precede the event.

Comorbidities prior to out-of-hospital cardiac arrest and diagnoses at discharge among survivors

BackgroundOut-of-hospital cardiac arrest (OHCA) has a dismal prognosis with overall survival around 10%. Previous studies have shown conflicting results regarding the prevalence and significance of comorbidities in OHCA, as well...

233 Coverage and validity of the Swedish Registry of Cardiopulmonary Resuscitation of in-hospital cardiac arrest

233 Coverage and validity of the Swedish Registry of Cardiopulmonary Resuscitation of in-hospital cardiac arrest

Short-Term Ambient Air Pollution Exposure and Risk of Out-of-Hospital Cardiac Arrest in Sweden: A Nationwide Case-Crossover Study.

Background Air pollution is one of the main risk factors for cardiovascular disease globally, but its association with out-of-hospital cardiac arrest at low air pollution levels is unclear. This nationwide study in Sweden aims to investigate if air pollution is associated with a higher risk of out-of-hospital cardiac arrest in an area with relatively low air pollution levels. Methods and Results This study was a nationwide time-stratified case-crossover study investigating the association between short-term air pollution exposures and out-of-hospital cardiac arrest using data from the SRCR (Swedish Registry for Cardiopulmonary Resuscitation) between 2009 and 2019. Daily air pollution levels were estimated in 1×1-km grids for all of Sweden using a satellite-based machine learning model. The association between daily air pollutant levels and out-of-hospital cardiac arrest was quantified using conditional logistic regression adjusted for daily air temperature. Particulate matter <2.5 μm exposure was associated with a higher risk of out-of-hospital cardiac arrest among a total of 29 604 cases. In a multipollutant model, the association was most pronounced for intermediate daily lags, with an increased relative risk of 6.2% (95% CI, 1.0-11.8) per 10 μg/m3 increase of particulate matter <2.5 μm 4 days before the event. A similar pattern of association was observed for particulate matter <10 μm. No clear association was observed for O3 and NO2. Conclusions Short-term exposure to air pollution was associated with higher risk of out-of-hospital cardiac arrest. The findings add to the evidence of an adverse effect of particulate matter on out-of-hospital cardiac arrest, even at very low levels below current regulatory standards.