Diurnal, weekly and seasonal rhythm of out of hospital cardiac arrest in Sweden

Comparison of Circadian Variation for In-Hospital Versus Out-of-Hospital Sudden Cardiac Arrest Survivors

Several studies have reported circadian periodicity of sudden cardiac arrest (SCA). It remains unclear to what extent this circadian rhythm is influenced by variation in patients' activities. One way to elucidate this is to compare patients with out-of-hospital cardiac arrests (OHCAs) with those with in-hospital cardiac arrests (IHCAs). We therefore examined the presence of a circadian pattern of SCA in a large cohort of OHCA and IHCA survivors. A total of 1,433 consecutive survivors of SCA in the Pittsburgh area from 2002 to 2012 were included. Patient demographics, including clinical histories and details of SCA, were collected. The distribution of SCA throughout the day was tested for differences using the chi-square test. Of the 1,224 patients analyzed, 706 had IHCA and 518 OHCA. We observed a nadir of SCA in the nighttime hours between 12 a.m. and 6 a.m. in both IHCA and OHCA groups (p <0.001), although this pattern was more blunted in the IHCA group. Patients who had an SCA in the nighttime window had more co-morbidities (p = 0.01). The circadian pattern was noted to be absent in patients with higher co-morbidity burden in IHCA only. In conclusion, the typical pattern of nighttime nadir in SCA is observed in patients with both OHCA and IHCA but is blunted in the hospital and especially in sicker patients. This suggests a common mechanistic pathway of SCA transcending differences in physical activities of patients and a difference in how co-morbidities interact with the timing of SCA in the inpatient setting.

Machine learning model for predicting out-of-hospital cardiac arrests using meteorological and chronological data

OBJECTIVES

To evaluate a predictive model for robust estimation of daily out-of-hospital cardiac arrest (OHCA) incidence using a suite of machine learning (ML) approaches and high-resolution meteorological and chronological data.

METHODS

In this population-based study, we combined an OHCA nationwide registry and high-resolution meteorological and chronological datasets from Japan. We developed a model to predict daily OHCA incidence with a training dataset for 2005-2013 using the eXtreme Gradient Boosting algorithm. A dataset for 2014-2015 was used to test the predictive model. The main outcome was the accuracy of the predictive model for the number of daily OHCA events, based on mean absolute error (MAE) and mean absolute percentage error (MAPE). In general, a model with MAPE less than 10% is considered highly accurate.

RESULTS

Among the 1 299 784 OHCA cases, 661 052 OHCA cases of cardiac origin (525 374 cases in the training dataset on which fourfold cross-validation was performed and 135 678 cases in the testing dataset) were included in the analysis. Compared with the ML models using meteorological or chronological variables alone, the ML model with combined meteorological and chronological variables had the highest predictive accuracy in the training (MAE 1.314 and MAPE 7.007%) and testing datasets (MAE 1.547 and MAPE 7.788%). Sunday, Monday, holiday, winter, low ambient temperature and large interday or intraday temperature difference were more strongly associated with OHCA incidence than other the meteorological and chronological variables.

CONCLUSIONS

A ML predictive model using comprehensive daily meteorological and chronological data allows for highly precise estimates of OHCA incidence.

Circadian Rhythms in Sudden Cardiac Arrest: A Review

BACKGROUND

Sudden cardiac arrest (SCA) is a serious public health issue caused by the cessation of cardiac electrical and mechanical activity. Despite advances in pedestrian lifesaving technologies like defibrillators, the SCA mortality rate remains high, and survivors are at risk of suffering ischemic injury to various organs. Understanding the contributing factors for SCA is essential for improving morbidity and mortality. One factor capable of influencing SCA incidence and survival is the time of day at which SCA occurs.

OBJECTIVES

This review focused on the effect of time of day on SCA incidence, survival rate, and survival to discharge over the past 30 years and the role of age, sex, and SCA location in modulating the timing of SCA.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews criteria guided this review. Four databases (PubMed, Cochrane Libraries, Scopus, and Cumulative Index to Nursing and Allied Health Literature) were queried for research reports or articles addressing time of day and cardiac arrest, which were subsequently screened by the authors for inclusion in this analysis.

RESULTS

A total of 48 articles were included in the final analysis. This analysis showed a bimodal SCA distribution with a primary peak in the morning and a secondary peak in the afternoon; these peaks were dependent on age (older persons), sex (more frequent in males), and the location of occurrence (out-of-hospital cardiac arrest vs. in-hospital cardiac rest). Survival following SCA was lowest between midnight and 06:00 a.m.

DISCUSSION

The circadian rhythm likely plays an important role in the time-of-day-dependent pattern that is evident in both the incidence of and survival following SCA. There is a renewed call for nursing research to examine or address circadian rhythm as an element in studies involving older adults and activities affecting cardiovascular or respiratory parameters.

Identification of a morning out-of-hospital cardiac arrest cluster of high-incidence: towards a chrono-preventive care strategy

RATIONALE, AIMS, AND OBJECTIVES

The human body is regulated by intrinsic factors which follow a 24-hour biological clock. Implications of a circadian rhythm in the out-of-hospital cardiac arrest (OHCA) are studied but the literature is not consistent. The main objective of our study was to identify temporal cluster of high or low incidence of OHCA occurrence during a day.

METHODS

Multicentre comparative study based on the French national OHCA registry data between 2013 and 2017. After describing the population, the detection of significant temporal clusters of OHCA incidence was achieved using temporal scan statistics based on a Poisson model adjusted for age and gender. Then, comparisons between identified patients clusters and the rest of the population were performed.

RESULTS

During the study, 37 163 medical OHCA victims were included. The temporal scan revealed a significant 3-hour high incidence temporal cluster between 8:00 am and 10:59 am (Relative R = 1.76, P < .001). In the identified cluster, OHCA occurred more out of the home with fewer witnesses, and advanced life support was less attempted in the cluster. No difference was observed on the return of spontaneous circulation, survival at hospital admission, and survival 30 days after the OHCA or at hospital discharge.

CONCLUSIONS

We observed a three-hour morning high incidence peak of OHCA. This high incidence could be explained by different physiological changes in the morning. These changes are well known and the evidence of a morning peak of cardiovascular disease should enable medical teams to adapt care strategy and hospital organization.

Influence of summer tourist flows on occurrence of out-of-hospital cardiac arrest in an Italian tourist-intensive area

INTRODUCTION

The study aims to evaluate the seasonal variation of out-of hospital cardiac arrest (OHCA) in a tourist-intensive area.

METHODS

Data of all OHCA treated by the Emergency Medical Service of Lecce (LE-EMS), Italy, between 2013 and 2017, were retrospectively analyzed and complemented with information about tourist flows, in order to determine the influence of the seasonal variation of population on incidence and outcome.

RESULTS

Tourist arrivals were around 1,700,000 per year, mostly in summer, adding up to 803,161 residents. The occurrence of OHCA did not show a monthly variation when referring to the resident population (p = 0.90). When taking into account the tourist flows, a difference in occurrence of OHCA across months was found, with the highest rate of arrests in December and the lowest in August (10.3 vs 3.4 per 100,000 persons, p < 0.01). No difference was found in terms of EMS arrival time and event survival rate between summer and the rest of the year (13.6 vs 13.8 min, p = 0.55, and 4.4% vs 4.5%, p = 0.86, respectively).

CONCLUSION

In summer tourism areas, the occurrence of OHCA is unchanged throughout the year, while the actual population presents seasonal increases. Summer enhancement of provincial EMS may contribute to maintain the performance of emergency care.

Seasonality of ventricular fibrillation at first myocardial infarction and association with viral exposure

AIMS

To investigate seasonality and association of increased enterovirus and influenza activity in the community with ventricular fibrillation (VF) risk during first ST-elevation myocardial infarction (STEMI).

METHODS

This study comprised all consecutive patients with first STEMI (n = 4,659; aged 18-80 years) admitted to the invasive catheterization laboratory between 2010-2016, at Copenhagen University Hospital, Rigshospitalet, covering eastern Denmark (2.6 million inhabitants, 45% of the Danish population). Hospital admission, prescription, and vital status data were assessed using Danish nationwide registries. We utilized monthly/weekly surveillance data for enterovirus and influenza from the Danish National Microbiology Database (2010-2016) that receives copies of laboratory tests from all Danish departments of clinical microbiology.

RESULTS

Of the 4,659 consecutively enrolled STEMI patients, 581 (12%) had VF before primary percutaneous coronary intervention. In a subset (n = 807), we found that VF patients experienced more generalized fatigue and flu-like symptoms within 7 days before STEMI compared with the patients without VF (OR 3.39, 95% CI 1.76-6.54). During the study period, 2,704 individuals were diagnosed with enterovirus and 19,742 with influenza. No significant association between enterovirus and VF (OR 1.00, 95% CI 0.99-1.02), influenza and VF (OR 1.00, 95% CI 1.00-1.00), or week number and VF (p-value 0.94 for enterovirus and 0.89 for influenza) was found.

CONCLUSION

We found no clear seasonality of VF during first STEMI. Even though VF patients had experienced more generalized fatigue and flu-like symptoms within 7 days before STEMI compared with patients without VF, no relationship was found between enterovirus or influenza exposure and occurrence of VF.

Epidemiology and chronobiology of out-of-hospital cardiac arrest in a subpopulation of southern Poland: A two-year observation

BACKGROUND

Although recent studies indicate temporal variations in the incidence of out-of-hospital cardiac arrest (OHCA), the Polish experience in this research is scarce to date. We evaluated the epidemiology of OHCA and circadian, weekly and seasonal variations of OHCA frequency among the adult population of the Opole district, Poland.

METHODS

The retrospective analysis of 815 OHCA cases with presumed cardiac etiology was made based on dispatch cards from the Emergency Medical Center in Opole registered during a 2 year period (2006-2007).

RESULTS

The incidence of OHCA in the studied population was 1.56/1000 inhabitants per year. Mean age of the group was 69.2 ± 14.2 years, with the majority of men (63%), younger than women (66.1 vs. 74 years, p = 0.0001). The OHCA occurrence increased with age reaching a peak between 71 and 75 years. The incidence of OHCA stayed at stable low levels between 22:00 and 4:59 and started to increase at 5:00, with trimodal peaks: 8:00-10:59, 14:00-15:59 and 18.00-21.59. The lowest number of OHCA occurred from 00:00 to 5:59, the highest from 6:00 to 11:59 (13% vs. 32.4%, p < 0.001). The day with the lowest occurrence of OHCA was Friday, the highest Saturday (10.9% vs. 16%, p = 0.01). Summer was the season of the lowest incidence of OHCA, while winter - the highest (22.6% vs. 26%, p = 0.04). These seasons were the warmest and the coldest one, respectively (average temperature 18.5°C vs. 0°C, p < 0.001).

CONCLUSIONS

Circadian and less marked, weekly variability in OHCA occurrence were confirmed. Existing seasonal differences may be affected by temperature. This is the first Polish analysis of a large subpopulation, which also includes seasonal temperature data.

Epidemiology and outcomes of anaphylaxis-associated out-of-hospital cardiac arrest

Background

Understanding the epidemiological characteristics of anaphylaxis-associated out-of-hospital cardiac arrest (OHCA) is the first step toward developing preventative strategies and optimizing care systems. We aimed to describe and compare epidemiological features and clinical outcomes among patients with anaphylaxis-associated OHCAs according to causative agent groups.

Methods

We identified emergency medical service (EMS)-treated anaphylaxis-associated OHCA patients from a nationwide OHCA registry between 2008 and 2015. We compared epidemiological characteristics and outcomes according to causal agents (a natural agents group and an iatrogenic agents group) and evaluated temporal variability in incidence. Multivariate logistic regression analysis was performed to compare survival to discharge between causative agent groups.

Results

During the study period (8 years), the total number of anaphylaxis-associated OHCAs was 233. A total of 224 eligible cases were included in the analysis. There were 192 patients (85.6%) in the natural agents group and 32 patients (14.3%) in the iatrogenic agents group. There was significant diurnal and seasonal variability in the frequency of anaphylaxis-associated OHCAs (p values<0.01 for both), with the highest incidences occurring during the day (7:01 am to 3 pm; 64.6%) and in summer (June to August, 48.7%). Compared with the natural agents group, the adjusted odds ratio (AOR) for survival to discharge in the iatrogenic agents group was statistically insignificant (AOR 3.61, 95% CI 0.86 to 15.06).

Conclusion

The incidence of anaphylaxis-associated OHCA is considerably low, and significant temporal variability, with a peak during the day and in summer, is evident. Anaphylaxis-associated OHCA is more common by natural agents than by iatrogenic agents, but no difference in the survival-to-discharge rate is evident.

The association between ambient temperature and out-of-hospital cardiac arrest in Guangzhou, China

Out-of-hospital cardiac arrest (OHCA) is becoming a considerable public health burden worldwide. The seasonal variation of OHCA has been observed, but the potential effects of ambient temperature on OHCA were rarely investigated. We, therefore, aimed to evaluate the association between ambient temperature and OHCA in Guangzhou, China. We collected daily emergency ambulance dispatches for OHCA from the Guangzhou Emergency Center from January 1, 2008 to December 31, 2012. We analyzed the associations using the time-series method. We applied the generalized linear model combined with the distributed lag non-linear model to estimate the potentially non-linear and lagged effects of temperature on OHCA. Time trends, day of the week, and air pollutants were controlled as covariates. We identified a total of 4369 cases of OHCD. The associations between daily mean temperature and OHCA were generally J-shaped. Both low and high temperatures could increase the risk of OHCA. The effects were strongest on the concurrent day (lag 0) and lasted for 6 or 7days. The cumulative risks of extreme cold (1st percentile of temperature) and extreme heat (99th percentile of temperature) over lags 0-21days were 3.75 (95% confidence interval [CI]: 1.63, 8.63) and 2.45 (95%CI: 1.15, 5.33), respectively, compared with the referent temperature (28°C)·This study suggested that both cold and hot temperatures could significantly increase the risk of OHCA in Guangzhou, China. Our results might have important public health implications for the prevention of OHCA.

Nighttime is associated with decreased survival and resuscitation efforts for out-of-hospital cardiac arrests: a prospective observational study

BACKGROUND

Whether temporal differences alter the clinical outcomes of patients with out-of-hospital cardiac arrest (OHCA) remains inconclusive. Furthermore, the relationship between time of day and resuscitation efforts is unknown.

METHODS

We studied adult OHCA patients in the Survey of Survivors after Out-of-Hospital Cardiac Arrest in the Kanto Region (SOS-KANTO) 2012 study from January 2012 to March 2013 in Japan. The primary variable was 1-month survival. The secondary outcome variables were prehospital and in-hospital resuscitation efforts by bystanders, emergency medical services personnel, and in-hospital healthcare providers. Daytime was defined as 0701 to 1500 h, evening was defined as 1501 to 2300 h, and night was defined as 2301 to 0700 h.

RESULTS

During the study period, 13,780 patients were included in the analysis. The patients with night OHCA had significantly lower 1-month survival compared to the patients with daytime OHCA (night vs. daytime, adjusted odds ratio (OR) 1.66; 95 % confidence interval (CI), 1.34-2.07; P < 0.0001). The nighttime OHCA patients had significantly shorter call-response intervals, bystander CPR, in-hospital intubation, and in-hospital blood gas analyses compared to the daytime and evening OHCA patients (call-response interval: OR 0.95 and 95 % CI 0.93-0.96; bystander CPR: OR 0.85 and 95 % CI 0.78-0.93; in-hospital intubation: OR 0.85 and 95 % CI 0.74-0.97; and in-hospital blood gas analysis: OR 0.86 and 95 % CI 0.75-0.98).

CONCLUSIONS

There was a significant temporal difference in 1-month survival after OHCA. The nighttime OHCA patients had significantly decreased resuscitation efforts by bystanders and in-hospital healthcare providers compared to those with evening and daytime OHCA.

Relationships of physiologically equivalent temperature and hospital admissions due to I30-I51 other forms of heart disease in Germany in 2009-2011

We aimed to understand relationships of the weather as biometeorological and hospital admissions due to other forms of heart disease by subtypes, which have been paid less attention, in a national setting in recent years. This is an ecological study. Ten percent of daily hospital admissions of the included hospitals (n = 1618) across Germany that were available between 1 January 2009 and 31 December 2011 (n = 5,235,600) were extracted from Statistisches Bundesamt, Germany. We identified I30-I51 other forms of heart disease by the International Classification of Diseases version 10 as the study outcomes. Daily weather data from 64 weather stations that have covered 13 German states, including air temperature, humidity, wind speed, cloud cover, radiation flux and vapour pressure, were obtained and generated into physiologically equivalent temperature (PET). Admissions due to other diseases of pericardium, nonrheumatic mitral valve disorders, nonrheumatic aortic valve disorders, cardiomyopathy, atrioventricular and left bundle-branch block, other conduction disorders, atrial fibrillation and flutter, and other cardiac arrhythmias peaked when PET was between 0 and 10 °C. Complications and ill-defined descriptions of heart disease admissions peaked at PET 0 °C. Cardiac arrest and heart failure admissions peaked when PET was between 0 and -10 °C while the rest did not vary significantly. A common drop of admissions was found when PET was above 10 °C. More medical resources could have been needed for heart health on days when PETs were <10 °C than on other days. Adaptation to such weather change for medical professionals and the general public would seem to be imperative.

Why and when citizens call for emergency help: an observational study of 211,193 medical emergency calls

BACKGROUND

A medical emergency call is citizens' access to pre-hospital emergency care and ambulance services. Emergency medical dispatchers are gatekeepers to provision of pre-hospital resources and possibly hospital admissions. We explored causes for access, emergency priority levels, and temporal variation within seasons, weekdays, and time of day for emergency calls to the emergency medical dispatch center in Copenhagen in a two-year study period (December 1(st), 2011 to November 30(th), 2013).

METHODS

Descriptive analysis was performed for causes for access and emergency priority levels. A Poisson regression model was used to calculate adjusted ratio estimates for the association between seasons, weekdays, and time of day overall and stratified by emergency priority levels.

RESULTS

We analyzed 211,193 emergency calls for temporal variation. Of those, 167,635 calls were eligible for analysis of causes and emergency priority level. "Unclear problem" was the most frequent category (19%). The five most common causes with known origin were categorized as "Wounds, fractures, minor injuries" (13%), "Chest pain/heart disease" (11%), "Accidents" (9%), "Intoxication, poisoning, drug overdose" (8%), and "Breathing difficulties" (7%). The highest emergency priority levels (Emergency priority level A and B) were assigned in 81% of calls. In the analysis of temporal variation, the total number of calls peaked at wintertime (26%), Saturdays (16%), and during daytime (39%).

CONCLUSION

The pattern of citizens' contact causes fell into four overall categories: unclear problems, medical problems, intoxication and accidents. The majority of calls were urgent. The magnitude of unclear problems represents a modifiable factor and highlights the potential for further improvement of supportive dispatch priority tools or educational interventions at dispatch centers. Temporal variation was identified within seasons, weekdays and time of day and reflects both system load and disease occurrence. Data on contact patterns could be utilized in a public health perspective, benchmarking of EMS systems, and ultimately development of best practice in the area of emergency medicine.

Relationship between seasonal weather changes, risk of dehydration, and incidence of severe bradyarrhythmias requiring urgent temporary transvenous cardiac pacing in an elderly population

There is little information on any seasonal variations or meteorological factors associated with symptomatic bradyarrhythmias requiring cardiac pacing. The aim of this single-center study was to investigate the seasonal distribution of the incidence of severe, life-threatening bradyarrhythmias requiring urgent temporary transvenous cardiac pacing in an elderly population. Consecutive patients who underwent urgent temporary transvenous cardiac pacing between 2007 and 2012 were enrolled. The baseline characteristics of the patients and some meteorological parameters, including the calculation the daily heat index (HI), were recorded. During the study period, 79 consecutive patients (mean age 82 ± 8 years, 41% male) underwent urgent temporary transvenous cardiac pacing, mainly for third-degree atrioventricular block (79%). The incidence of bradyarrhythmias was significantly higher in summer than in the other seasons (P < 0.001). Moreover, the highest incidence was observed in months with HI > 90 °F for >3 h per day for at least 10 days (P < 0.001). A direct correlation was found between the average monthly temperature and the monthly number of patients undergoing temporary cardiac pacing (r = 0.54, P < 0.001). Compared with other patients, those observed during the hottest months were significantly older and more frequently affected by chronic disabling neurological diseases (all P < 0.05). In addition, they more frequently showed biochemical indices of dehydration, renal function impairment and hyperkalemia (all P < 0.05). This study showed an increased incidence of severe bradyarrhythmias in an elderly population during the hottest months of the year. In these months, in subjects characterized by increased susceptibility to dehydration, the risk of developing bradyarrhythmias was increased significantly.

Weekly and holiday-related patterns of panic attacks in panic disorder: a population-based study

BACKGROUND

While chronobiological studies have reported seasonal variation in panic attacks (PA) episodes, information on the timing of PA by week-days may enable better understanding of the triggers of PA episodes and thereby provide pointers for suitable interventional approaches to minimize PA attacks. This study investigated weekly variation in potential PA admissions including associations with holidays using a population-based longitudinal, administrative claims-based dataset in an Asian population.

METHODS

This study used ambulatory care data from the "Longitudinal Health Insurance Database 2000. We identified 993 patients with panic disorder (PD), and they had 4228 emergency room (ER) admissions for potential PA in a 3-year period between 1 January 2009 and 31 December 2011. One-way analysis of variance (ANOVA) was used to examine associations between the potential PA admissions and holidays/weekend days/work-days of the week.

RESULTS

The daily mean number of potential PA admissions was 3.96 (standard deviation 2.05). One-way ANOVA showed significant differences in potential PA admissions by holiday and day of the week (p<0.001). Daily frequencies showed a trough on Wednesday-Thursday, followed by a sharp increase on Saturday and a peak on Sunday. Potential PA admissions were higher than the daily mean for the sample patients by 29.4% and 22.1%, respectively on Sundays and holidays. Furthermore, the weekly variations were similar for females and males, although females always had higher potential PA admissions on both weekdays and holidays than the males.

CONCLUSIONS

We found that potential PA admissions among persons with PD varied systematically by day of the week, with a significant peak on weekends and holidays.

Temporal differences in out-of-hospital cardiac arrest incidence and survival

BACKGROUND

Understanding temporal differences in the incidence and outcomes of out-of-hospital cardiac arrest (OHCA) has important implications for developing preventative strategies and optimizing systems for OHCA care.

METHODS AND RESULTS

We studied 18 588 OHCAs of presumed cardiac origin in patients aged ≥18 years who received resuscitative efforts by emergency medical services (EMS) and were enrolled in the Cardiac Arrest Registry to Enhance Survival (CARES) from October 1, 2005, to December 31, 2010. We evaluated temporal variability in OHCA incidence and survival to hospital discharge. There was significant variability in the frequency of OHCA by hour of the day (P<0.001), day of the week (P<0.001), and month of the year (P<0.001), with the highest incidence occurring during the daytime, from Friday to Monday, in December. Survival to hospital discharge was lowest for OHCA that occurred overnight (from 11:01 pm to 7 am; 7.1%) versus daytime (7:01 am to 3 pm; 10.8%) or evening (3:01 pm to 11 pm; 11.3%; P<0.001) and during the winter (8.8%) versus spring (11.1%), summer (11.0%), or fall (10.0%; P<0.001). There was no difference in survival to hospital discharge between OHCAs that occurred on weekends and weekdays (9.5% versus 10.4%, P=0.06). After multivariable adjustment for age, sex, race, witness status, layperson resuscitation, first monitored cardiac rhythm, and emergency medical services response time, compared with daytime and spring, survival to hospital discharge remained lowest for OHCA that occurred overnight (odds ratio, 0.81; 95% confidence interval, 0.70-0.95; P=0.008) and during the winter (odds ratio, 0.81; 95% confidence interval, 0.70-0.94; P=0.006), respectively.

CONCLUSIONS

There is significant temporal variability in the incidence of and survival after OHCA. The relative contribution of patient pathophysiology, likelihood of the OHCA being observed, and prehospital and hospital-based resuscitative factors deserves further exploration.

Ambulance demand: random events or predicable patterns?

BACKGROUND

Occupational, social and recreational routines follow temporal patterns, as does the onset of certain acute medical diseases and injuries. It is not known if the temporal nature of injury and disease transfers into patterns that can be observed in ambulance demand. This review examines eligible study findings that reported temporal (time of day, day of week and seasonal) patterns in ambulance demand.

METHODS

Electronic searches of Medline and Cumulative Index of Nursing and Allied Health Literature were conducted for papers published between 1980 and 2011. In addition, hand searching was conducted for unpublished government and ambulance service documents and reports for the same period.

RESULTS

38 studies examined temporal patterns in ambulance demand. Six studies reported trends in overall workload and 32 studies reported trends in a subset of ambulance demand, either as a specific case type or demographic group. Temporal patterns in overall demand were consistent between jurisdictions for time of day but varied for day of week and season. When analysed by case type, all jurisdictions reported similar time of day patterns, most jurisdictions had similar day of week patterns except for out-of-hospital cardiac arrest and similar seasonal patterns, except for trauma. Temporal patterns in case types were influenced by age and gender.

CONCLUSIONS

Temporal patterns are present in ambulance demand and importantly these populations are distinct from those found in hospital datasets suggesting that variation in ambulance demand should not be inferred from hospital data alone. Case types seem to have similar temporal patterns across jurisdictions; thus, research where demand is broken down into case types would be generalisable to many ambulance services. This type of research can lead to improvements in ambulance service deliverables.

Circadian, weekly, and seasonal mortality variations in out-of-hospital cardiac arrest in Japan: analysis from AMI-Kyoto Multicenter Risk Study database

BACKGROUND

Several studies have reported circadian, weekly, and seasonal variations in the rates of out-of-hospital cardiac arrest (OHCA). However, variations in the mortality of OHCA are not well known.

METHODS AND RESULTS

We investigated the 1396 consecutive cases of OHCA with cardiac etiology between October 2004 and September 2008. There were 2 peaks in the occurrence of OHCA in early morning and late evening. There was a weekly pattern with an increased incidence on Mondays. We found a significant seasonal variation in the frequency of events, with a maximum during winter. There was a trend of reduced mortality in warmest 3 months, especially among a subgroup of ventricular fibrillation/pulseless ventricular tachycardia with arrest witnessed.

CONCLUSION

The present analyses demonstrated circadian, weekly and seasonal variations in the occurrence, and a seasonal variation in mortality in OHCA. Changes in temperature might influence the severity of OHCA and change the rate of success of cardiopulmonary resuscitation.

Temporal variation of out-of-hospital cardiac arrests in an equatorial climate

OBJECTIVE

We aimed to determine whether there is a seasonal variation of out-of-hospital cardiac arrests (OHCA) in an equatorial climate, which does not experience seasonal environmental change.

METHODS

We conducted an observational prospective study looking at the occurrence of OHCA in Singapore. Included were all patients with OHCA presented to Emergency Departments across the country. We examined the monthly, daily, and hourly number of cases over a three-year period. Data was analyzed using analysis of variance (ANOVA).

RESULTS

From October, 1st 2001 to October, 14th 2004, 2428 patients were enrolled in the study. Mean age for cardiac arrests was 60.6 years with 68.0% male. Ethnic distribution was 69.5% Chinese, 15.0% Malay, 11.0% Indian, and 4.4% Others. There was no significant seasonal variation (spring/summer/fall/winter) of events (ANOVA P = 0.71), monthly variation (P = 0.88) or yearly variation (P = 0.26). We did find weekly peaks on Mondays and a circadian pattern with daily peaks from 9-10 am.

CONCLUSIONS

We did not find any discernable seasonal pattern of cardiac arrests. This contrasts with findings from temperate countries and suggests a climatic influence on cardiac arrest occurrence. We also found that sudden cardiac arrests follow a circadian pattern.

Out-of-hospital cardiac arrest frequency and survival: evidence for temporal variability

AIM

Some cardiac phenomena demonstrate temporal variability. We evaluated temporal variability in out-of-hospital cardiac arrest (OHCA) frequency and outcome.

METHODS

Prospective cohort study (the Resuscitation Outcomes Consortium) of all OHCA of presumed cardiac cause who were treated by emergency medical services within 9 US and Canadian sites between 12/1/2005 and 02/28/2007. In each site, Emergency Medical System records were collected and analyzed. Outcomes were individually verified by trained data abstractors.

RESULTS

There were 9667 included patients. Median age was 68 (IQR 24) years, 66.7% were male and 8.3% survived to hospital discharge. The frequency of cardiac arrest varied significantly across time blocks (p<0.001). Compared to the 0001-0600 hourly time block, the odds ratios and 95% CIs for the occurrence of OHCA were 2.02 (1.90, 2.15) in the 0601-1200 block, 2.01 (1.89, 2.15) in the 1201-1800 block, and 1.73 (1.62, 1.85) in the 1801-2400 block. The frequency of all OHCA varied significantly by day of week (p=0.03) and month of year (p<0.001) with the highest frequencies on Saturday and during December. Survival to hospital discharge was lowest when the OHCA occurred during the 0001-0600 time block (7.3%) and highest during the 1201-1800 time block (9.6%). Survival was highest for OHCAs occurring on Mondays (10.0%) and lowest for those on Wednesdays (6.8%) (p=0.02).

CONCLUSION

There is temporal variability in OHCA frequency and outcome. Underlying patient, EMS system and environmental factors need to be explored to offer further insight into these observed patterns.

Rationale, development and implementation of the Resuscitation Outcomes Consortium Epistry-Cardiac Arrest

OBJECTIVE

To describe the development, design and consequent scientific implications of the Resuscitation Outcomes Consortium (ROC) population-based registry; ROC Epistry-Cardiac Arrest.

METHODS

The ROC Epistry--Cardiac Arrest is designed as a prospective population-based registry of all Emergency Medical Services (EMSs)-attended 9-1-1 calls for patients with out-of-hospital cardiac arrest occurring in the geographical area described by the eight US and three Canadian regions. The dataset was derived by an North American interdisciplinary steering committee. Enrolled cases include individuals of all ages who experience cardiac arrest outside the hospital, with evaluation by organized EMS personnel and: (a) attempts at external defibrillation (by lay responders or emergency personnel), or chest compressions by organized EMS personnel; (b) were pulseless but did not receive attempts to defibrillate or CPR by EMS personnel. Selected data items are categorized as mandatory or optional and undergo revisions approximately every 12 months. Where possible all definitions are referenced to existing literature. Where a common definition did not exist one was developed. Optional items include standardized CPR process data elements. It is anticipated the ROC Epistry--Cardiac Arrest will enroll between approximately 9000 and 13,500 treated all rhythm arrests and 4000 and 5000 ventricular fibrillation arrests annually and approximately 8000 EMS-attended but untreated arrests.

CONCLUSION

We describe the rationale, development, design and future implications of the ROC Epistry--Cardiac Arrest. This paper will serve as the reference for subsequent ROC manuscripts and for the common data elements captured in both ROC Epistry--Cardiac Arrest and the ROC trials.

A web-based Utstein style registry system of in-hospital cardiopulmonary resuscitation in Taiwan

PURPOSE OF THE STUDY

The Web-Based Registry System on In-hospital Resuscitation (WRSIR) is the first prospective, web-based, multi-site, and Utstein-based reporting system in Taiwan. This study was conducted to evaluate the feasibility of the system in one of the participating hospitals and identify prognostic factors associated with survival.

MATERIAL AND METHODS

The WRSIR is an on-line registry system coded with the active server page (ASP) programming method. Information was gathered and entered on-line by trained staff using spreadsheets that could be automatically created according to the updated Utstein in-hospital template. Through the implementation of the system, in a tertiary teaching hospital we evaluated all adults with in-hospital cardiac arrest receiving cardiopulmonary resuscitation between 1 October 2004 and 30 September 2005. The main outcome measures were return of spontaneous circulation (ROSC), survival to hospital discharge, and cerebral performance category score at the time of discharge. Logistic regression analysis was performed to determine independent predictors of survival.

RESULTS

A total of 330 cases experienced in-hospital resuscitation. ROSC occurred in 233 cases (71%) and 61 patients (18%) survived to hospital discharge. Thirty-five patients (58%) had a good neurological outcome with the cerebral performance category (CPC) score of 1 or 2 among survivors. The major predictor of ROSC was initial rhythm of VT/VF (adjusted OR 0.36, 95% CI 0.16-0.78).

CONCLUSION

This study examined the feasibility of a web-based registry system on in-hospital resuscitation using the Utstein style in an oriental country. It provides a comprehensive and standardised method for on-line registry of data collection, allowing individual hospitals to track each case for quality improvement. A further nationwide registry will enforce the possibility of data analysis and future perspective research of in-hospital resuscitation.

Design and implementation of resuscitation research: special challenges and potential solutions

Evaluation of the effectiveness of resuscitation interventions is challenging. We describe these challenges, which include design, enrolment and analysis issues. Randomized trials establish if interventions work in predefined populations. "Efficacy" trials determine whether interventions work under ideal conditions. "Effectiveness" trials determine whether interventions work under usual practice conditions. These trials represent a trade-off between internal validity versus external validity. Randomized trials use random allocation of participants to interventions to produce study groups that are similar with respect to known and unknown risk factors, reduce bias in the allocation of participants, and assure that statistical tests have valid significance levels. In the emergency setting, there is a risk that treatment offered to control patients will be contaminated by providers' experiences of applying the intervention to patients receiving the experimental intervention. Frequently there is not time to obtain consent from a patient in an emergency setting. Exception from consent can be applied if certain conditions are met. Enrolment in a research study must be initiated quickly in an emergency setting or the patient will die or become disabled. In any trial, data can be used to explore different aspects of response to treatment: multiple treatments, subgroups, events; and interim analyses. We propose solutions to these challenges to help potential investigators through the myriad of difficulties in initiating trials in a complex environment. Design of simple trials that have adequate power enhances their external validity. Allocating groups of episodes to interventions by randomizing by clusters, rather than by individual patients reduces provider noncompliance. Waiver from consent for emergency research and use of novel technologies could facilitate enrolment despite time constraints. Rigorous statistical methods can be used to analyze multiple data without an excessive increase in the chance of a false-positive result.

Resuscitation by primary care doctors

BACKGROUND

Sudden cardiac arrest is a common mechanism of premature death in the community. Resuscitation is often possible, but no large study of resuscitation by doctors who practice there has been published.

METHODS

General practitioners (GPs) equipped with defibrillators reported 555 patients with cardiac arrest in whom they attempted resuscitation.

FINDINGS

Average age was 65.4, 75% male. Most arrests (49%) occurred at the patient's home but some (18%) occurred at or near the doctors' surgeries. Heart disease was responsible for 88% of the arrests: in these cases resuscitation to leave hospital alive was frequently successful (148 of 436 attempts, 34%). Success was rare (one of 59, <2%) when the arrest was due to non-cardiac disease. Resuscitation was most common when the first monitored rhythm was shockable (VF/VT) and defibrillated promptly: 144 out of 351 (41%) patients surviving. VF/VT was most common with early rhythm monitoring, particularly when the doctor was present (63% survival), or nearby (54%). When VF/VT complicated AMI, 72% of those defibrillated within 1min of onset survived. With delayed attendance, the frequency of VF/VT fell and asystole or Pulseless Electrical Activity (PEA) became more common. Survival after resuscitation was rare for patients presenting with these rhythms: five of 202 (2.5%). No such patient survived unless the rhythm could be converted to VF/VT with drugs or basic life support and subsequently shocked.

CONCLUSION

Primary care doctors equipped with defibrillators attend patients with cardiac arrest under circumstances in which resuscitation is frequently successful. This presents a unique opportunity to reduce mortality from sudden cardiac arrest.

Seasonal variation of mortality in the Antiarrhythmics Versus Implantable Defibrillators (AVID) study registry

OBJECTIVES

We postulated that the pattern of death would be nonrandom with respect to temporal variables.

BACKGROUND

Previous studies have demonstrated increased sudden death is associated with periods of relative stress, and overall mortality is associated with temporal variables.

METHODS

In the Antiarrhythmics Versus Implantable Defibrillators (AVID) registry, vital status was obtained for 4,450 patients (who had a recent episode of sustained ventricular arrhythmias or unexplained syncope and inducible ventricular tachycardia) through the National Death Index Service as of December 31, 1997 (follow-up 25.5 +/- 13.7 months).

RESULTS

Mortality was not associated with the day of the week or with holidays but was associated with season (P = .033). Seasonal variation was present both in northern and southern sites. Mortality was higher during the winter months compared to the remaining months (111.2% in winter vs 96.5% in other months, P = .036). In addition, increased mortality was associated with a high-risk season variable defined (prior to evaluation of treatment arm associations) as spring in the north and winter in the south (P < .001). The hazard ratio for death associated with this "high-risk season" measured 1.25 (P = .001) compared to the other seasons in each region. A test of interaction between "high-risk" season and implantable cardioverter-defibrillator (ICD) status suggested that the group with ICDs experienced reduced mortality during the "high-risk season" compared to the group without ICDs (P = .047).

CONCLUSIONS

Mortality was higher in the winter months and in the respective regional "high-risk" seasons. Furthermore, seasonal variation in mortality may have been due to variation in sudden arrhythmic death, and associated increases in mortality were reduced by ICD therapy.