Circadian variation in sudden cardiac death: effects of age, sex, and initial cardiac rhythm

The Daily Patterns of Emergency Medical Events

This study examines population-level daily patterns of time-stamped emergency medical service (EMS) dispatches to establish their situational predictability. Using visualization, sinusoidal regression, and statistical tests to compare empirical cumulative distributions, we analyzed 311,848,450 emergency medical call records from the US National Emergency Medical Services Information System (NEMSIS) for years 2010 through 2022. The analysis revealed a robust daily pattern in the hourly distribution of distress calls across 33 major categories of medical emergency dispatch types. Sinusoidal regression coefficients for all types were statistically significant, mostly at the p < 0.0001 level. The coefficient of determination ( R 2 ) ranged from 0.84 and 0.99 for all models, with most falling in the 0.94 to 0.99 range. The common sinusoidal pattern, peaking in mid-afternoon, demonstrates that all major categories of medical emergency dispatch types appear to be influenced by an underlying daily rhythm that is aligned with daylight hours and common sleep/wake cycles. A comparison of results with previous landmark studies revealed new and contrasting EMS patterns for several long-established peak occurrence hours-specifically for chest pain, heart problems, stroke, convulsions and seizures, and sudden cardiac arrest/death. Upon closer examination, we also found that heart attacks, diagnosed by paramedics in the field via 12-lead cardiac monitoring, followed the identified common daily pattern of a mid-afternoon peak, departing from prior generally accepted morning tendencies. Extended analysis revealed that the normative pattern prevailed across the NEMSIS data when reorganized to consider monthly, seasonal, daylight-savings versus civil time, and pre-/post-COVID-19 periods. The predictable daily EMS patterns provide impetus for more research that links daily variation with causal risk and protective factors. Our methods are straightforward and presented with detail to provide accessible and replicable implementation for researchers and practitioners.

Post-mortem genetic testing in sudden cardiac death and genetic screening of relatives at risk: lessons learned from a Czech pilot multidisciplinary study

Sudden cardiac death (SCD) might have an inherited cardiac condition background. Genetic testing supports post-mortem diagnosis and screening of relatives at risk. Our aim is to determine the feasibility of a Czech national collaboration group and to establish the clinical importance of molecular autopsy and family screening. From 2016 to 2021, we have evaluated 100 unrelated SCD cases (71.0% males, age: 33.3 (12.8) years). Genetic testing was performed by next-generation sequencing utilizing a panel of 100 genes related to inherited cardiac/aortic conditions and/or whole exome sequencing. According to autopsy, cases were divided into cardiomyopathies, sudden arrhythmic death syndrome, sudden unexplained death syndrome, and sudden aortic death. We identified pathogenic/likely pathogenic variants following ACMG/AMP recommendations in 22/100 (22.0%) of cases. Since poor DNA quality, we have performed indirect DNA testing in affected relatives or in healthy parents reaching a diagnostic genetic yield of 11/24 (45.8%) and 1/10 (10.0%), respectively. Cardiological and genetic screening disclose 83/301 (27.6%) relatives at risk of SCD. Genetic testing in affected relatives as starting material leads to a high diagnostic yield offering a valuable alternative when suitable material is not available. This is the first multidisciplinary/multicenter molecular autopsy study in the Czech Republic which supports the establishment of this type of diagnostic tests. A central coordinator and proper communication among centers are crucial for the success of a collaboration at a national level.

The effect of bedtime versus morning dosing of antihypertensive drugs on the cardiovascular outcomes: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVE

Antihypertensive drugs are one of the most effective strategies to prevent disability and mortality; however, there have been contradictory findings about the best dosing time for antihypertensive drugs. Therefore, we aim to evaluate the effect of bedtime versus morning dosing of antihypertensive drugs on cardiovascular outcomes.

METHODS

We synthesized randomized controlled studies (RCTs) from the Web of Science, SCOPUS, EMBASE, PubMed, and CENTRAL until 13 October 2022. The risk ratio (RR) for dichotomous outcomes with the corresponding 95% confidence interval (CI) was used. The study protocol was registered in PROSPERO with ID: CRD42022368612.

RESULTS

Five RCTs with 59 200 participants were included. Bedtime dosing was significantly associated with less incidence of myocardial infarction (MI) [RR: 0.80 with 95% CI (0.70-0.91), P = 0.0007] compared with morning dosing; however, there was no statistically significant difference between bedtime and morning dosing, regarding all-cause mortality [RR: 0.77 with 95% CI (0.51-1.16), P = 0.21], cardiovascular mortality [RR: 0.65 with 95% CI (0.35-1.21), P = 0.17], major adverse cardiac events (MACE) [RR: 0.79 with 95% CI (0.56-1.10), P = 0.16], heart failure [RR: 0.68 with 95% CI (0.42-1.09), P = 0.11], cerebrovascular accidents [RR: 0.80 with 95% CI (0.53-1.22), P = 0.30], coronary revascularization [RR: 0.79 with 95% CI (0.50-1.24), P = 0.30}, and angina [RR: 0.91 with 95% CI (0.55-1.50), P = 0.70].

CONCLUSION

Evidence about the comparative efficacy of bedtime versus morning dosing of antihypertensives is still uncertain. However, bedtime dosing significantly reduced MI, which warrants more robust RCTs to validate.

Circadian aspects of mortality in hospitalized patients: A retrospective observation from a large cohort

AIM

This study aimed to describe the circadian characteristics of hospitalized mortality in order to provide nursing guidance for preventing in-hospital mortality.

DESIGN

A retrospective analysis on inpatient information was implemented.

METHODS

Harmonic Analysis of Time Series was applied to quantify the periodic structure of the frequency of the occurrence of death.

RESULTS

A total of 3300 cases were included in the present study (male, 63.4% and median age 73 years), including 1540 (46.7%) ICU patients. Incidence of overall hospitalized death exhibited a circadian pattern, presenting peaks from 07:00 to 12:00 and 15:00 to 20:00 P.M., with 21.5% and 13.1% increase above the average at those peak points, respectively. Similarly, the incidence of sudden cardiac death (SCD) showed peaks between 06:00-12:00 and 15:00-20:00, with a 34.7% and 28.0% increase above the average at peak time, respectively. The distribution of death incidence revealed no statistical difference between SCD and non-SCD (p = 0.525).

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.

Proceedings of the Sleep and Epilepsy Workgroup: Section 2 Comorbidities: Sleep Related Comorbidities of Epilepsy

Epilepsy is a chronic disease with multiple, complex comorbidities. Bidirectional relationships exist among seizures, sleep, circadian rhythms, and diseases within and outside of the central nervous system. Seizures fragment sleep and can contribute to development of sleep disorders, which in turn leads to worse overall health and more seizures. Moreover, treatment options are often limited by interactions with anti-seizure medications. Advances in the fields of epilepsy and in sleep medicine have been made separately, and therefore treating patients with these comorbidities necessitates interdisciplinary approach. The focus of this section of the Sleep and Epilepsy Workgroup was to identify methods of collaboration and outline investigational, educational, and treatment priorities to mutually advance what we consider a combined field.

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.

Circadian Rhythms of Early Afterdepolarizations and Ventricular Arrhythmias in a Cardiomyocyte Model

Sudden cardiac arrest is a malfunction of the heart's electrical system, typically caused by ventricular arrhythmias, that can lead to sudden cardiac death (SCD) within minutes. Epidemiological studies have shown that SCD and ventricular arrhythmias are more likely to occur in the morning than in the evening, and laboratory studies indicate that these daily rhythms in adverse cardiovascular events are at least partially under the control of the endogenous circadian timekeeping system. However, the biophysical mechanisms linking molecular circadian clocks to cardiac arrhythmogenesis are not fully understood. Recent experiments have shown that L-type calcium channels exhibit circadian rhythms in both expression and function in guinea pig ventricular cardiomyocytes. We developed an electrophysiological model of these cells to simulate the effect of circadian variation in L-type calcium conductance. In our simulations, we found that there is a circadian pattern in the occurrence of early afterdepolarizations (EADs), which are abnormal depolarizations during the repolarization phase of a cardiac action potential that can trigger fatal ventricular arrhythmias. Specifically, the model produces EADs in the morning, but not at other times of day. We show that the model exhibits a codimension-2 Takens-Bogdanov bifurcation that serves as an organizing center for different types of EAD dynamics. We also simulated a two-dimensional spatial version of this model across a circadian cycle. We found that there is a circadian pattern in the breakup of spiral waves, which represents ventricular fibrillation in cardiac tissue. Specifically, the model produces spiral wave breakup in the morning, but not in the evening. Our computational study is the first, to our knowledge, to propose a link between circadian rhythms and EAD formation and suggests that the efficacy of drugs targeting EAD-mediated arrhythmias may depend on the time of day that they are administered.

CLOCK-BMAL1 regulate the cardiac L-type calcium channel subunit CACNA1C through PI3K-Akt signaling pathway

The heterodimerized transcription factors CLOCK-BMAL1 regulate the cardiomyocyte circadian rhythms. The L-type calcium currents play important role in the cardiac electrogenesis and arrhythmogenesis. Whether and how the CLOCK-BMAL1 regulate the cardiac L-type calcium channels are yet to be determined. The functions of the L-type calcium channels were evaluated with patch clamping techniques. Recombinant adenoviruses of CLOCK and BMAL1 were used in the expression experiments. We reported that the expressions and functions of CACNA1C (the α-subunit of the L-type calcium channels) showed circadian rhythms, with the peak at zeitgeber time 3 (ZT3). The endocardial action potential durations 90 (APD90) were correspondingly longer at ZT3. The protein levels of the phosphorylated Akt at threonine 308 (pAkt T308) also showed circadian rhythms. Overexpressions of CLOCK-BMAL1 significantly reduced the levels of CACNA1C while increasing the levels of pAkt T308 and pik3r1. Furthermore, the inhibitory effects of CLOCK-BMAL1 on CACNA1C could be abolished by the Akt inhibitor MK2206 or the PDK1 inhibitor GSK2334470. Collectively, our findings suggested that the expressions of the cardiac CACNA1C were under the CLOCK-BMAL1 regulation, probably through the PI3K-Akt signal pathway.

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.

Presumed Regional Incidence Rate of Out-of-Hospital Cardiac Arrest in Korea

The regional incidence rates of out-of-hospital cardiac arrest (OHCA) were traditionally calculated with the residential population as the denominator. The aim of this study was to estimate the true incidence rate of OHCA and to investigate characteristics of regions with overestimated and underestimated OHCA incidence rates. We used the national OHCA database from 2006 to 2010. The nighttime residential and daytime transient populations were investigated from the 2010 Census. The daytime population was calculated by adding the daytime influx of population to, and subtracting the daytime outflow from, the nighttime residential population. Conventional age-standardized incidence rates (CASRs) and daytime corrected age-standardized incidence rates (DASRs) for OHCA per 100,000 person-years were calculated in each county. A total of 97,291 OHCAs were eligible. The age-standardized incidence rates of OHCAs per 100,000 person-years were 34.6 (95% CI: 34.3-35.0) in the daytime and 24.8 (95% CI: 24.5-25.1) in the nighttime among males, and 14.9 (95% CI: 14.7-15.1) in the daytime, and 10.4 (95% CI: 10.2-10.6) in the nighttime among females. The difference between the CASR and DASR ranged from 35.4 to -11.6 in males and from 6.1 to -1.0 in females. Through the Bland-Altman plot analysis, we found the difference between the CASR and DASR increased as the average CASR and DASR increased as well as with the larger daytime transient population. The conventional incidence rate was overestimated in counties with many OHCA cases and in metropolitan cities with large daytime population influx and nighttime outflow, while it was underestimated in residential counties around metropolitan cities.

Population-based incidence of sudden cardiac and unexpected death before and after the 2011 earthquake and tsunami in Iwate, northeast Japan

BACKGROUND

The aim of this study was to evaluate the temporal impact of the 2011 Japan earthquake and tsunami on the incidence of sudden cardiac and unexpected death (SCUD).

METHODS AND RESULTS

We surveyed the impact of the disaster on the incidence and clinical characteristics of SCUD in Iwate. To perform complete identification of SCUD for 8 weeks before and 40 weeks after the disaster, medical records and death certificates relevant to SCUD were surveyed in the study area. Compared with the previous year's rate, the incidence (per 10 000 person-year) of SCUD for the initial 4 weeks after the disaster (acute phase) was double (33.5 vs 18.9), and thereafter the rate returned to the previous level. Significant relationships were found between weekly numbers of SCUD and seismic activity (intensity, r=0.43; P<0.005: frequency, r=0.46; P<0.002). The standardized incidence ratio (SIR) of SCUD in the acute phase was significantly increased compared with that of previous years (1.71, 95% CI 1.33 to 2.16). Increased SIRs were predominantly found in female subjects (1.73, 95% CI 1.22 to 2.37), the elderly (1.73, 95% CI 1.29 to 2.27), and residents living in the tsunami-stricken area (1.83, 95% CI 1.33 to 2.46). In addition, SIRs for weekdays (1.71, 95% CI 1.28 to 2.24) and nights-mornings (2.09, 95% CI 1.48 to 2.86) were amplified.

CONCLUSIONS

The present results suggest that the magnitude of a disaster, related stress, and population aging may cause a temporary increase in the incidence of SCUD with amplification of ordinary weekly and circadian variations.

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.

Both morning and evening dosing of nebivolol reduces trough mean blood pressure surge in hypertensive patients

The morning blood pressure surge (MBPS) has been shown to be an independent predictor of cardiovascular events. There is insufficient evidence on the effect of nebivolol, a vasodilating β1-receptor blocker, on the MBPS when given in the morning or the evening. This is a prospective, randomized, double-blind, crossover study designed to test morning vs. evening dosing of nebivolol in nondiabetic, hypertensive patients. Patients received nebivolol 5 mg/day (force-titrated to 10 mg/day after 1 week) in the morning or evening and corresponding placebos. Patients underwent ambulatory BP monitoring at baseline and after each treatment phase. Forty-two patients were randomized, of whom 38 completed both study periods. Both morning and evening dosed nebivolol significantly lowered daytime, nighttime, and 24-hour BP after 3 weeks of treatment. Evening (but not morning) dosing significantly reduced prewaking systolic BP from baseline (8.64 ± 26.46 mm Hg, P = .048). Nebivolol given in the morning or the evening significantly reduces 24-hour BP parameters. Evening dosed nebivolol may confer some advantage over morning dosing in reducing prewaking systolic BP.

Sudden cardiac death: epidemiology, circadian variation, and triggers

Sudden cardiac death (SCD) remains a major health issue accounting for over 5% of annual mortality in the Western world. There are several causes of SCD, most commonly, coronary artery disease. Although identifying the prodrome of SCD has attracted considerable interest, a large proportion of patients die before any medical contact is established. SCD onset seems to follow a circadian pattern, most likely because of exposure to endogenous and exogenous triggers. The aim of the present report is to review the current knowledge of epidemiology, patterns of onset, and triggers of SCD and present directions for future research with a focus on coronary artery disease.

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.

Differential effects of waking from non-rapid eye movement versus rapid eye movement sleep on cardiovascular activity

The occurrence of cardiovascular events increases in the morning, and while the mechanism responsible is yet to be determined, possible contributors include surges in sympathetic activity and concurrent rises in blood pressure (BP). This study tested the hypothesis that the increase in sympathetic dominance and the surge in BP were greater when waking spontaneously from Stage 2 sleep compared with waking from rapid eye movement (REM) sleep. Twenty healthy young adults had overnight polysomnography, including electrocardiogram measurements. Spectral analysis of heart rate variability (HRV) was conducted on 2-min blocks of stable data selected from the last 30 min of sleep and during 30 min of resting wakefulness (supine) immediately following sleep. Outputs included absolute low frequency (LF) and high frequency (HF) power, the LF/HF ratio, heart rate (HR) and BP. To investigate the effect of waking from Stage 2 or REM sleep on HRV and BP responses, two-way analyses of variance (anovas) (Stage 2 versus REM) with repeated measures (sleep versus morning wakefulness) were performed. It was found that waking from Stage 2 sleep was associated with significant increases in HR (P = 0.002) and BP (P < 0.001), as well as a tendency towards an increase in the LF/HF ratio (P = 0.08), whereas measurements during REM sleep and subsequent wakefulness were similar (P > 0.05). The greater increase in BP and HR when waking from Stage 2 sleep compared with REM sleep suggests that in vulnerable populations, waking from Stage 2 sleep could be an adjunct risk factor of cardiovascular events during the morning period.

The influence of age on heart rate variability during morning wakefulness

OBJECTIVE

Early morning wakefulness is associated with a peak in cardiac events. The influence of ageing on cardiac regulation during this time is unknown. This cross-sectional study of healthy men and women (n = 40, 20-30 and >60 years) investigated the effect of age on heart rate variability (HRV) during morning versus evening wakefulness and sleep.

METHODS

Stable electrocardiogram data during each wake period and sleep stage was analysed using power spectral analysis. HRV measurements were assessed using two (young, older) by two (male, female) ANOVAs with repeated measures on wake/sleep stage.

RESULTS

Young adults experienced increased low-frequency power and low-frequency/high-frequency ratios during morning wakefulness versus slow wave sleep (p < 0.01). Older adults did not show any variation in any HRV variables across wake and sleep stages. All effects were independent of gender.

INTERPRETATION

Older adults did not experience increased sympathetic dominance during morning wakefulness; thus in the older population, fluctuations in autonomic control, indicated by HRV measurements, are unlikely to account for increased occurrence of cardiac events at this time.

Sex differences in cardiac sympathovagal balance and vagal tone during nocturnal sleep

OBJECTIVE

To analyze sex differences in nocturnal vagal tone and cardiac sympathovagal balance during sleep in healthy men and women.

METHODS

In two groups of healthy, non-obese adults (15 men and 14 women), sleep was polygraphically recorded and heart rate variability was assessed during an awake period prior to sleep and during sleep. Vagal tone was estimated by the high-frequency (HF) power component of heart rate variability, and sympathovagal balance was indexed by the ratio of low-frequency (LF) power to HF power.

RESULTS

As compared to women, men showed decreases in vagal tone and increases in sympathovagal balance. During rapid eye movement (REM) sleep, a withdrawal of vagal tone occurred with an increase in sympathetic dominance. Men showed a greater increase of sympathovagal balance during REM sleep than women. Secondary analyses covarying for differences in reproductive hormone levels, physical activity, and sleep measures did not alter the results.

CONCLUSIONS

The marked increase in cardiac sympathetic drive during REM sleep in men has implications for understanding sex differences in the risk of cardiovascular events. Additionally, these data offer a pathway to explain the peak in cardiac arrhythmias and sudden cardiac death seen more often in the morning hours.

Circadian variation in cardiovascular emergencies among the elderly

Clarification of the cyclic pattern of emergency events is useful for identifying risk factors for emergency events. We attempted to characterize the circadian variation in emergency calls for the elderly (aged 65 years or older) because the use of emergency transportation by elderly patients is increasing rapidly. The study targeted mainly patients with cardiovascular disease. Additionally, the study analyzed circadian variability in the occurrence of cardiopulmonary arrest (CPA) and heat stroke. Data for this study were obtained from computerized records of ambulance transport from 1997 to 2003 (a total of 874,495 transported patients) managed by the Emergency Medical Division of the Yokohama Fire Bureau. A partial Fourier model was used to analyze circadian patterns of emergency calls for each disease category and determine the peak time of occurrence of disease events. A prominent peak of cardiovascular disease and CPA in the morning was observed among elderly patients, whereas amplitudes of the morning and evening peaks were almost the same among younger patients. Heat stroke among elderly patients occurred frequently from 10:00 AM to 3:00 PM, and the occurrence peaked around noon. The increase in cardiovascular disease events and CPA during the morning among elderly patients may be due to a natural fluctuation in blood pressure. A morning increase in hemoconcentration induced by dehydration during the night is thought to be another cause of the frequent occurrence of cardiovascular disease, CPA, and heat stroke events in the morning hours. In conclusion, there was a prominent peak in the morning in the occurrence of emergency events such as cardiovascular disease, CPA, and heat stroke events among the elderly.

Resuscitation in the hospital: circadian variation of cardiopulmonary arrest

PURPOSE

Over 25 reports have found outpatient frequency of sudden cardiac death peaks between 6 am and noon; few studies, with inconsistent results, have examined circadian variation of death in hospitalized patients. This study assesses circadian variation in cardiopulmonary arrest of in-hospital patients across patient, hospital, and event variables and its effect on survival to discharge.

METHODS

A retrospective, single institution registry included all admissions to the Medical Center of Central Georgia in which resuscitation was attempted between January 1987 and December 2000. The registry included 4692 admissions; only the first attempt was reported. Analyses of 1-, 2-, 4-, and 8-hour intervals were performed; 1- and 4-hour intervals are presented.

RESULTS

Significant circadian variation was found at 1 hour (P=.01), but not at 4-hour intervals. Significant circadian variation was found for initial rhythms that were perfusing (P=.03) and asystole (P=.01). A significantly higher percentage of unwitnessed events were found as asystole during the overnight hours (P=.002). Using simple logistic regression, time in 4-hour intervals and rhythm were each significantly related to patient survival until hospital discharge (P=.003 and P <.0001). In multivariate analysis, only rhythm remained significant.

CONCLUSIONS

Circadian variation of cardiopulmonary arrest in this hospital has several temporal versions and is related to survival. Late night variation in witnessed events and rhythm suggests a delay between onset of clinical death and discovery, which contributes to poorer outcomes.

Temporal distribution of deaths in cancer patients during the day in different settings

BACKGROUND

All living organisms perform their functions normally according to circadian rhythms. Certain diseases, such as ischemic heart disease and asthma, produce symptoms that are distributed during the day in a nonrandom fashion. Chronomodulated therapy with some regimens of chemotherapy and other drugs produce better results than traditional schedules. Even death is not evenly distributed during the day. Significant differences in the time of death through the day could influence the work planning and care activities.

OBJECTIVE

To determine whether timing of death from a population of cancer patients admitted at our Oncology Institute varied during the day and according to different settings: at home (H), at the palliative care unit (PCU), and at other services (OS) of the hospital. Comparing the timing of deaths from different settings can give some clues about the possible existence of a circadian rhythm and the influence of external circumstances in the time of death of cancer patients.

DESIGN

We conducted a retrospective study of the records of time of death at the different settings.

RESULTS

The study involved 772 patients from the PCU and 997 from OS who died between May 25, 1996, and May 24, 2000, and 347 patients who died at H between April 1, 1999, and December 31, 2001. A statistically significant difference was found in the distribution of time of death in patients at the PCU (p <.001), but not at OS or at H. There were two peaks between 08:00 and 10:00 and between 00:00 and 02:00, and one trough between 04:00 and 08:00. This suggests that a temporal variation occurs in the time of death of cancer patients dying in the PCU, but not in other settings.

CONCLUSIONS

The clinical relevance of the results obtained in this study would depend on the amplitude of the eventual variation detected in the number of deaths during the day. Therefore, although there was a statistically significant variation at the time of death during the day, its amplitude is not high enough to make it clinically significant. The differences observed among the various settings suggest that, even if circadian rhythms exist at the time of death in cancer patients, external factors can overcome these rhythms.

Circadian variation in ventricular tachycardia and atrial fibrillation in a medical-cardiological ICU

OBJECTIVE

To assess the diurnal distribution of ventricular tachycardia (VT) and atrial fibrillation (AF) in critically ill patients.

DESIGN AND SETTING

Prospective observational study (episode-based design) in an eight-bed medical/cardiological ICU at a university hospital that also admits postoperative patients.

PATIENTS

98 consecutive patients with AF ( n=55) or ventricular tachycardia ( n=43).

MEASUREMENTS AND RESULTS

There were a total of 218 arrhythmia episodes (83 AF, 136 VT). The time of arrhythmia onset was not evenly distributed. Circadian variation in VT but not AF onset was well represented by a sine wave function. Both VT and AF fibrillation showed a trough during the night. The distribution of VT and AF episodes did not differ significantly with or without analgosedation.

CONCLUSIONS

In critically ill patients the onset of VT and AF over 24-h is nonuniformly distributed. In VT this circadian pattern of occurrence is well modeled by a sine wave function peaking between noon and 2 p.m. The circadian pattern is less clear for AF. The circadian variation is seen irrespective of the presence of absence of analgosedation for both arrhythmias.

Circadian variation of cardiac K+ channel gene expression

BACKGROUND

Many cardiac arrhythmias have their own characteristic circadian variations. Because the expression of many genes, including clock genes, is regulated variably during a day, circadian variations of ion channel gene expression, if any, could contribute to the fluctuating alterations of cardiac electrophysiological characteristics and subsequent arrhythmogenesis.

METHODS AND RESULTS

To examine whether cardiac K+ channel gene expression shows a circadian rhythm, we analyzed the mRNA levels of 8 Kv and 6 Kir channels in rat hearts every 3 hours throughout 1 day. Among these channels, Kv1.5 and Kv4.2 genes showed significant circadian variations in their transcripts: approximately 2-fold increase of Kv1.5 mRNA from trough at Zeitgeber time (ZT) 6 to peak at ZT18 and a completely reverse pattern in Kv4.2 mRNA ( approximately 2-fold increase from trough at ZT18 to peak at ZT6). Actually, along with the variations in the immunoreactive proteins, the density of the transient outward and steady-state currents in isolated myocytes and the responses of atrial and ventricular refractoriness to 4-aminopyridine in isolated-perfused hearts showed differences between ZT6 and ZT18, a circadian pattern comparable to that of Kv1.5 and Kv4.2 gene expression. Reversal of light stimulation almost inverted these circadian rhythms, although pharmacological autonomic blockade only partially attenuated the rhythm of Kv1.5 but not of Kv4.2 transcripts.

CONCLUSIONS

Among all the cardiac K+ channels, Kv1.5 and 4.2 channels are unique in showing characteristic circadian patterns in their gene expression, with Kv1.5 increase during the dark period partially dependent on beta-adrenergic activities and Kv4.2 increase during the light period independent of the autonomic nervous function.

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

AIM

To describe the diurnal, weekly and seasonal rhythm among patients suffering from out of hospital cardiac arrest in Sweden.

METHODS

All patients in Sweden between 1990 and 1999 participating in a National Registry covering 65% of all patients suffering from out of hospital cardiac arrest where cardiopulmonary resuscitation (CPR) was attempted. Only patients with a cardiac arrest of a cardiac aetiology and aged > 18 years were included in the survey.

RESULTS

10,868 patients fulfilled inclusion criteria. In terms of the diurnal rhythm, there was a progressive increase in the development of cardiac arrest from 06:00 h, reaching a peak at about 10:00 h. Thereafter, there was a progressive decline until 05:00 h. The diurnal rhythm was more marked among patients aged > 65 years and among patients in whom the arrest occurred outside home. There was a weekly rhythm with an increased incidence of cardiac arrest on Mondays. This was particularly evident among patients aged < 66 years and among men. A cardiac arrest occurred most frequently in January and December. This was particularly observed in the large cities.

CONCLUSION

We found that out of hospital cardiac arrest of a cardiac etiology has a diurnal, weekly and seasonal rhythm occurring most frequently in the morning hours, on Mondays and in December and January. Age, sex and place of arrest influence these rhythms.

Circadian pattern of emergency calls: implications for ED organization

A circadian variation has been shown in the onset of acute medical diseases and we postulate that there is a circadian variation in emergency calls. We reviewed the 20,858 emergency calls addressed to the Emergency Coordinating Unit of the Hospital of Ferrara, Italy, from January 1 to December 31, 1998. Precise determination of the time of calls was available from the recordings. Total calls and subgroups by different diseases were categorized into 24 one-hour increments and analyzed for circadian rhythmicity by applying a partial Fourier series. A circadian variation was found for all subgroups, except for alcoholic intoxication. There was a peak frequency of calls in the morning hours for cardiologic, respiratory, and neurologic disease. There was a peak frequency of calls in the afternoon for trauma, neoplastic diseases, and acute poisoning. Organization of quantity and quality of Emergency Department (ED) staff should take into account the increased demand of specific facilities during certain hours of the day.

Outcomes of out-of-hospital cardiac arrest patients in Perth, Western Australia, 1996-1999

STUDY OBJECTIVE

To describe the epidemiology and survival from out-of-hospital cardiac arrest.

DESIGN

Longitudinal follow-up study from the time of paramedic attendance to 12 months later.

SETTING

Perth, Western Australia (WA), a metropolitan capital city with an adult population of approximately one million people.

METHOD

The St John Ambulance Australia (WA Ambulance Service Incorporated) cardiac arrest database was linked to the WA hospital morbidity and mortality data using probabilistic matching.

INCIDENCE

Of 3730 cardiorespiratory arrests in 1996-1999, the age standardised rate of arrests of presumed cardiac origin, where resuscitation was attempted (n=1293) was 32.9 per 100000 person-years and 7.1 per 100000 person-years for bystander-witnessed VF/VT arrests.

SURVIVAL

Survival to 28 days was 6.8% following all bystander-witnessed cardiac arrests; 10.6% following bystander-witnessed VF/VT arrests and 33% for paramedic-witnessed cardiac arrests. Logistic regression analysis showed an inverse association between ambulance response time interval and survival following all bystander-witnessed cardiac arrests (and VF/VT arrests). ONE YEAR SURVIVAL: 89% of bystander-witnessed cardiac arrest survivors and 92% of paramedic-witnessed cardiac arrests were still alive at 1 year post-arrest.

CONCLUSION

The trends in occurrence and survival following out-of-hospital cardiac arrest in Perth, WA, are similar to those found elsewhere. There is an opportunity to strengthen the chain of survival by reducing the response time interval and increasing the use of bystander cardiopulmonary resuscitation (CPR). First-responder programs and public access defibrillation will need to be considered in the light of local demographics, location and the epidemiologic features of out-of-hospital cardiac arrest.

Effect of quinapril or metoprolol on circadian sympathetic and parasympathetic modulation after acute myocardial infarction

Abnormal autonomic nervous system impairment in patients with acute myocardial infarction (AMI) has a circadian pattern with the greatest manifestation in the morning hours; it probably plays an important role in the pathogenesis of cardiac arrhythmias and acute ischemic syndromes. Angiotensin-converting enzyme inhibitors improve autonomic function in patients with AMI, but the circadian pattern of this effect has not been studied. Heart rate variability-normalized frequency domain indexes were assessed 5 days (baseline) after the onset of uncomplicated AMI and 30 days after therapy with quinapril (n = 30), metoprolol (n = 30), or placebo (n = 30) with a solid-state digital Holter monitor. Normal subjects (n = 30) were used as controls. Quinapril increased parasympathetic and decreased sympathetic modulation, and improved sympathovagal interactions manifested by an increase in normalized high-frequency power (HFP), and a decrease in normalized low-frequency power (LFP), and their ratio (LFP/HFP) during the entire 24-hour period (p<0.001), with maximal effect on the ratio (p<0.0001) between 02.00 to 04.00 A.M., 08.00 to 11.00 A.M., and 19.00 to 22.00 P.M. (delta% ratio -30%, -32%, and -26%, respectively). Metoprolol increased HFP and decreased LFP and the LFP/HFP ratio mainly between 08.00 A.M. to 12.00 noon, and 19.00 to 22.00 P.M. (delta% ratio -21%, and -12% respectively, p<0.001). Heart rate variability indexes in the placebo group and controls remained unchanged 30 days after the baseline study. In conclusion, quinapril increased parasympathetic, and decreased sympathetic and partially restored sympathovagal interaction in patients with uncomplicated AMI during the entire 24-hour period, with peak effect in the early and late morning and evening hours. Metoprolol had a similar effect during the late morning and evening hours, but at a lower level. These effects may prove beneficial in reducing cardiac arrhythmias and acute ischemic syndromes in past-AMI patients.

Circadian variation of malignant ventricular arrhythmias in patients with ischemic and nonischemic heart disease after cardioverter defibrillator implantation. European 7219 Jewel Investigators

OBJECTIVES

The purpose of this study was to examine the circadian variation of ventricular arrhythmias detected by an implantable cardioverter defibrillator in patients with and without ischemic heart disease.

BACKGROUND

Previous studies have shown a circadian variation of ventricular arrhythmias, sudden death and myocardial infarction with a peak occurrence in the morning hours. The circadian pattern, which is similar for both arrhythmic and ischemic events, suggests that ischemia may play a critical role in the genesis of ventricular arrhythmias and sudden death. We hypothesized that, if ischemia plays an important role in the triggering of ventricular arrhythmias, the circadian pattern should be different in patients with ischemic heart disease compared with patients with nonischemic heart disease.

METHODS

The circadian variation of ventricular arrhythmias recorded by an implantable cardioverter defibrillator was studied in 310 patients during a mean follow-up of 181 +/- 163 days. Two hundred four patients had a history of ischemic heart disease and 106 patients had nonischemic heart disease. The times of the episodes of ventricular arrhythmias were retrieved from the data log of each device during follow-up, and the circadian pattern was compared between the two groups.

RESULTS

During follow-up, 1,061 episodes of ventricular arrhythmias were recorded by the device in the 310 patients. Six hundred eighty-two episodes occurred in the group of patients with ischemic heart disease and 379 occurred in the nonischemic heart disease group. The circadian variation of the episodes showed a typical pattern with a morning and afternoon peak in both groups of patients with ischemic and nonischemic heart disease, but there was no significant difference between the two groups.

CONCLUSIONS

The circadian rhythm of ventricular arrhythmias in patients with ischemic heart disease is similar to patients with nonischemic heart disease, suggesting that the trigger mechanisms of the initiation of ventricular tachyarrhythmias may be similar, irrespective of the underlying heart disease.