Circadian patterns of ST elevation myocardial infarction in the new millennium

Circadian Variations and Associated Factors in Patients with Ischaemic Heart Disease

Circadian rhythms have been identified in cardiovascular diseases, and cardiovascular risk factors can modify the circadian rhythm. The purpose of this study was to describe the onset of ischaemic heart disease symptomatology in relation to the date and time, the day of the week of presentation, the season, AMI location and severity and the level of influence of individual patient characteristics in a retrospective cross-sectional study involving 244 ischaemic heart disease patients from the intensive care unit of La Ribera Hospital (Spain). The onset of pain was more frequent in the morning, the season with the highest frequency of ischaemic events was winter, and the lowest incidence was during weekends. Regarding the severity of ischaemic heart disease, the circadian rhythm variables of weekdays vs. weekends and seasons did not show a significant association. The length of hospital stay was associated with the onset of pain in the afternoon. The onset of pain at night was associated with the subendocardial location of the infarction. In conclusion, living in a Mediterranean country, the Spanish population showed a circadian pattern of AMI, where the onset of pain has an influence on AMI location and on the length of hospital stay and is the same in patients with different individual risk factors.

Influence of Intermittent Fasting During Ramadan on Circadian Variation of Symptom-Onset and Prehospital Time Delay in Acute ST-Segment Elevation Myocardial Infarction

Ramadan interferes with circadian rhythms mainly by disturbing the routine patterns of feeding and smoking. The objective of this study was to investigate the circadian pattern of ST elevation acute myocardial infarction (STEMI) during the month of Ramadan. We studied consecutive STEMI patients 1 month before and after Ramadan (non-Ramadan group-NRG) and during Ramadan (Ramadan group-RG). The RG group was also divided into two groups, based on whether they chose to fast: fasting (FG) and non-fasting group (NFG). The time of STEMI onset was compared. A total of 742 consecutive STEMI patients were classified into 4 groups by 6 h intervals according to time-of-day at symptom onset. No consistent circadian variation in the onset of STEMI was observed both between the RG (P = .938) and NRG (P = .766) or between the FG (P = .232) and NFG (P = .523). When analyzed for subgroups of the study sample, neither smoking nor diabetes showed circadian rhythm. There was a trend towards a delay from symptom onset to hospital presentation, particularly at evening hours in the RG compared with the control group. In conclusion, there was no significant difference in STEMI onset time, but the time from symptom onset to hospital admission was significantly delayed during Ramadan.

Molecular regulations of circadian rhythm and implications for physiology and diseases

The term “circadian rhythms” describes endogenous oscillations with ca. 24-h period associated with the earth’s daily rotation and light/dark cycle. Such rhythms reflect the existence of an intrinsic circadian clock that temporally orchestrates physiological processes to adapt the internal environment with the external cues. At the molecular level, the circadian clock consists of multiple sets of transcription factors resulting in autoregulatory transcription-translation feedback loops. Notably, in addition to their primary role as generator of circadian rhythm, the biological clock plays a key role in controlling physiological functions of almost all tissues and organs. It regulates several intracellular signaling pathways, ranging from cell proliferation, DNA damage repair and response, angiogenesis, metabolic and redox homeostasis, to inflammatory and immune response. In this review, we summarize findings showing the crosstalk between the circadian molecular clock and some key intracellular pathways, describing a scenario wherein their reciprocal regulation impinges upon several aspects of mammalian physiology. Moreover, based on evidence indicating that circadian rhythms can be challenged by environmental factors, social behaviors, as well as pre-existing pathological conditions, we discuss implications of circadian misalignment in human pathologies, such as cancer and inflammatory diseases. Accordingly, disruption of circadian rhythm has been reported to affect several physiological processes that are relevant to human diseases. Expanding our understanding of this field represents an intriguing and transversal medicine challenge in order to establish a circadian precision medicine.

Temporal variation in out-of-hospital cardiac arrest occurrence in individuals with or without diabetes

Objective

Out-of-hospital cardiac arrest (OHCA) occurrence has been shown to exhibit a circadian rhythm, following the circadian rhythm of acute myocardial infarction (AMI) occurrence. Diabetes mellitus (DM) is associated with changes in circadian rhythm. We aimed to compare the temporal variation of OHCA occurrence over the day and week between OHCA patients with DM and those without.

Methods

In two population-based OHCA registries (Amsterdam Resuscitation Studies [ARREST] 2010-2016, n = 4163, and Danish Cardiac Arrest Registry [DANCAR], 2010-2014, n = 12,734), adults (≥18y) with presumed cardiac cause of OHCA and available medical history were included. Single and double cosinor analysis was performed to model circadian variation of OHCA occurrence. Stratified analysis of circadian variation was performed in patients with AMI as immediate cause of OHCA.

Results

DM patients (22.8% in ARREST, 24.2% in DANCAR) were older and more frequently had cardiovascular risk factors or previous cardiovascular disease. Both cohorts showed 24 h-rhythmicity, with significant amplitudes in single and double cosinor functions (P-range < 0.001). In both registries, a morning peak (10:00-11:00) and an evening peak (20:00-21:00) was observed in both DM and non-DM patients. No septadian variation was observed in either DM or non-DM patients (P-range 0.13-84).

Conclusions

In these two population-based OHCA registries, we observed a similar circadian rhythm of OHCA occurrence in DM and non-DM patients.

Circadian disruption and human health

Circadian disruption is pervasive and can occur at multiple organizational levels, contributing to poor health outcomes at individual and population levels. Evidence points to a bidirectional relationship, in that circadian disruption increases disease severity and many diseases can disrupt circadian rhythms. Importantly, circadian disruption can increase the risk for the expression and development of neurologic, psychiatric, cardiometabolic, and immune disorders. Thus, harnessing the rich findings from preclinical and translational research in circadian biology to enhance health via circadian-based approaches represents a unique opportunity for personalized/precision medicine and overall societal well-being. In this Review, we discuss the implications of circadian disruption for human health using a bench-to-bedside approach. Evidence from preclinical and translational science is applied to a clinical and population-based approach. Given the broad implications of circadian regulation for human health, this Review focuses its discussion on selected examples in neurologic, psychiatric, metabolic, cardiovascular, allergic, and immunologic disorders that highlight the interrelatedness between circadian disruption and human disease and the potential of circadian-based interventions, such as bright light therapy and exogenous melatonin, as well as chronotherapy to improve and/or modify disease outcomes.

Circadian influence on inflammatory response during cardiovascular disease

Circadian rhythms follow a 24 h day and night cycle, regulate vital physiological processes, and are especially relevant to cardiovascular growth, renewal, repair, and remodeling. A recent flurry of clinical and experimental studies reveals a profound circadian influence on immune responses in cardiovascular disease. The first section of this review summarizes the importance of circadian rhythms for cardiovascular health and disease. The second section introduces the circadian nature of inflammatory responses. The third section combines these to elucidate a new role for the circadian system, influencing inflammation in heart disease, especially myocardial infarction. Particular focus is on circadian regulation of the NACHT, LRR, and PYD domains-containing protein 3 inflammasome, neutrophils, monocytes/macrophages, and T cells involved in cardiac repair. A role for biological sex is noted. The final section explores circadian influences on inflammation in other major cardiovascular conditions. Circadian regulation of inflammation has profound implications for benefitting the diagnosis, treatment, and prognosis of patients with cardiovascular disease.

Comparison of clinical outcomes in STEMI patients treated with primary PCI according to day-time of medical attention and its relationship with circadian pattern

OBJECTIVE

Relationship between STEMI time of presentation, its circadian pattern and cardiovascular outcomes is unclear. Our objective is to analyze clinical outcomes of STEMI according to time of presentation and circadian pattern.

METHODS

We analyzed data from patients treated within the regional STEMI Network from January 2010 to December 2015. On-hour group included patients treated between 8:00 h and 19:59 h on weekdays, the rest were catalogued as off-hour group. The primary endpoint was 1-year all-cause mortality. Secondary endpoints were 30-day all-cause mortality and in-hospital complications.

RESULTS

A total of 8608 patients were included, 44.1% in the on-hour group and 55.9% in the off-hour group. We observed a shorter patient delay and longer system delay in the off-hour group compared to on-hour group with no difference in total ischemic time. At 30-day and 1-year follow-up there were no differences in adjusted all-cause mortality between groups [OR 0.91 (CI95%: 0.73-1.12; p = 0.35) and OR 0.99 (CI95%: 0.83-1.17; p = 0.87), respectively]. A circadian pattern was observed between 9:00 am and 12:30 pm, with no differences in 30-day and 1-year mortality between patients included in this time interval [OR 1.02 (IC95%: 0.81-1.30; p = 0.85) and OR 1.12 (IC95%: 0.92-1.36; p = 0.25) respectively].

CONCLUSIONS

Off-hour STEMI presentation was associated with a shorter patient delay and longer system delay without an increase in total ischemic time. The off-hour presentation was not related to an increase in 1-year all-cause mortality when compared to on-hour. A circadian pattern was found, without differences in 30-day and 1-year mortality.

Presentation Times of Myocardial Infarctions to the Emergency Department: Disappearance of the Morning Predominance

BACKGROUND

Previous studies show that myocardial infarctions (MIs) occur most frequently in the morning.

OBJECTIVES

We hypothesized that there no longer is a morning predominance of MI, and that the timing of ST-elevation myocardial infarction (STEMI) vs. non-ST-elevation myocardial infarction (NSTEMI) presentation differs.

METHODS

We reviewed MI, STEMI, and NSTEMI patients (2013-2017) from a multiple-hospital system, identified by diagnostic codes. Daily emergency department arrival times were categorized into variable time intervals for count and proportional analysis, then examined for differences.

RESULTS

There were 18,663 MI patients from 12 hospitals included in the analysis. Most MIs occurred between 12:00 pm and 5:59 pm (35.7%), and least between 12:00 am-5:59 am (16.3%). After subdividing all MIs into STEMIs and NSTEMIs, both groups continued to have the greatest presentation between 12:00 pm and 5:59 pm (33.1% and 36.0%, respectively). STEMIs (17.2%) and NSTEMIs (16.2%) were least frequent between 12:00 am and 5:59 am. We found the second most common presentation time for MIs was in the 6 pm-11:59 pm time period, which held true for both subtypes (MI 26.7%, STEMI 26.4%, NSTEMI 26.7%).

CONCLUSIONS

These data suggest a potential shift in the circadian pattern of MI, revealing an afternoon predominance for both STEMI and NSTEMI subtypes.

Circadian Rhythm of Deaths in a Cardiology Department: A Five-Year Analysis

BACKGROUND

Previous studies have described a circadian pattern of death from cardiovascular causes with a morning peak. Our aim is to describe the daytime oscillations in mortality in hospitalized patients with cardiovascular diseases.

METHODS

Our retrospective registry including all patients who died in the Cardiology Department, including the cardiac intensive care unit, Madrid, Spain.

RESULTS

From a total of 500 patients, time of death was registered in 373 (74.6%), which are the focus of our study; 354 (70.8%) died in the cardiac intensive care unit and 146 (29.2%) in the conventional ward. Mean age was 74.2 ± 13.1 years, and 239 (64.1%) were male. Cardiovascular causes were the leading cause of death (308 patients; 82.6%). Mortality followed a circadian biphasic pattern with a peak at dawn (00.00-05.59 a.m.: 104 patients [27.9%]) and in the afternoon (12.00-17.59 p.m.: 135 patients [36.2%]), irrespective of the cause of death. The peak of mortality occurred in the afternoon (12.00-17.59 p.m.) in the case of cardiovascular mortality (119 deaths [38.6%]) and in the evening (18.00-23.59 p.m.) for non-cardiovascular deaths (21 deaths [32.3%], p = 0.03). This pattern was present regardless from the place of death (conventional ward or cardiac intensive care unit) and also throughout the four seasons.

CONCLUSIONS

Mortality in hospitalized patients with cardiovascular diseases follows a circadian biphasic pattern.

Predictors of transportation delay in patients with suspected ST-elevation-myocardial infarction in the VIENNA-STEMI network

OBJECTIVE

The emergency medical service (EMS) provides rapid pre-hospital diagnosis and transportation in ST-elevation myocardial infarction (STEMI) systems of care. Aim of the study was to assess temporal and regional characteristics of EMS-related delays in a metropolitan STEMI network.

METHODS

Patient call-to-arrival of EMS at site (call-to-site), transportation time from site to hospital (site-to-door), call-to-door, patient's location, month, weekday, and hour of EMS activation were recorded in 4751 patients referred to a tertiary center with suspicion of STEMI.

RESULTS

Median call-to-site, site-to-door, and call-to-door times were 9 (7-12), 39 (31-48), and 49 (41-59) minutes, respectively. The shortest transportation times were noted between 08:00 and 16:00 and in general on Sundays. They were significantly prolonged between midnight and 04:00, whereby the longest difference did not exceed 4 min in median. Patient's site of call had a major impact on transportation times, which were shorter in Central and Western districts as compared to Southern and Eastern districts of Vienna (p < 0.001 between-group difference for call-to-site, site-to-door, and call-to-door). After multivariable adjustment, patient's site of call was an independent predictor of call-to-site delay (p < 0.001). Moreover, age and hour of EMS activation were the strongest predictors of call-to-site, site-to-door, and call-to-door delays (p < 0.05).

CONCLUSION

In our Viennese STEMI network, the strongest determinants of pre-hospital EMS-related transportation delays were patient's site of call, patient's age, and hour of EMS activation. Due to the significant but small median time delays, which are within the guideline-recommended time intervals, no impact on clinical outcome can be expected.

Circadian clock genes and circadian phenotypes in patients with myocardial infarction

PURPOSE

Human physiological activities and diseases are under the control of the circadian rhythm. There are strong epidemiological associations between disrupted circadian rhythms, sleep duration and diseases. Sleep disorders are associated with vascular outcomes, such as myocardial infarction (MI).

METHODS

We conducted an association study of genotype-phenotype interaction, to determine which circadian clock gene variants might be associated with the circadian phenotypes in patients with MI. In the present study, we analyzed the allele frequencies of 10 single nucleotide polymorphisms in four circadian clock genes in two independent samples: MI patients and controls. Chronotype was assessed using the Morningness - Eveningness Questionnaire (MEQ) and daytime sleepiness using the Epworth Sleepiness Scale (ESS).

RESULTS

Chronotype was associated with the ARNTL genetic variant rs12363415 in MI patients. The polymorphisms rs11932595 of the CLOCK gene and rs934945 of the PER2 gene were associated with daytime sleepiness in the patient group.

CONCLUSION

Our data suggest that genetic variations in some circadian clock genes might be related to circadian phenotype (i.e., chronotype and daytime sleepiness) in patients with myocardial infarction.

Circadian clock genes and myocardial infarction in patients with type 2 diabetes mellitus

Disruption of circadian clock may trigger the onset of diabetes mellitus and myocardial infarction. Type 2 diabetes mellitus (T2DM) is well-known risk factors for cardiovascular diseases and myocardial infarction. We performed a case-control study, where we explored the possible association between single nucleotide polymorphisms in three circadian rhythm genes (ARNTL, CLOCK, and PER2) and myocardial infarction in 657 patients with T2DM. The study group consisted of 231 patients with myocardial infarction and T2DM and a control group of 426 T2DM patients. We hypothesized that variations in the circadian rhythm genes in patients with T2DM could be an additional risk factor for myocardial infarction. The statistically significant difference was found in allelic (p = 1.1 × 10-5) and genotype distribution (p = 1.42 × 10-4) between two groups of the rs12363415 at the ARNTL gene locus. We provide evidence that genetic variability in the ARNTL gene might be associated with myocardial infarction in patients with T2DM.

Cultural factors and the circadian rhythm of ST elevation myocardial infarction in patients in a Mediterranean island

INTRODUCTION

The circadian rhythm of onset of myocardial infarction shows an increased risk during the morning hours. However, it is not clear whether habits, culture and sunshine hours differentiate circadian rhythm. The aim of this study was to investigate the influence of cultural factors on the circadian rhythm of acute myocardial infarction with ST segment elevation in a Mediterranean island.

METHOD

The study was a retrospective correlational survey. It included 123 patients with ST elevation myocardial infarction (mean age 60.7±12.6; 82% men). The 24 h of a day were divided into four six-hour periods of time for study purposes (00:01-06:00; 06:01-12:00; 12:01-18:00; and 18:01-24:00) and the chi-square test was used for the analysis.

RESULTS

A morning peak of symptoms onset of ST-elevation myocardial infarction was detected during the period 06:01-12:00 (p=0.044). In patients who were smokers, a bimodal pattern involving a morning (06:01-12:00) and an afternoon-to-night peak (18:01-24:00) (p=0.005) was detected. For patients with a history of hypertension, a morning peak of their symptoms was also detected (p=0.028). Different circadian variations were found between patients over the age of 60 years old and patients under the age of 60 years old (p=0.025).

CONCLUSIONS

Patients with ST elevation myocardial infarction seem to follow a circadian rhythm with a peak of onset of symptoms in the morning. In the smokers' subgroup, a different circadian pattern was found. The habit of smoking is likely to affect the circadian rhythm of the onset of ST elevation myocardial infarction in the Mediterranean area and culture.

Circadian onset and prognosis of myocardial infarction with non-obstructive coronary arteries (MINOCA)

Background

Many acute cardiovascular events such as myocardial infarction (MI) follow circadian rhythms. Myocardial infarction with non-obstructive coronary arteries (MINOCA) is a newly noticed entity with limited data on onset pattern and its impact on prognosis.

Material and methods

In this observational study of Swedish MINOCA patients registered in the SWEDEHEART registry between 2003–2013 and followed until December 2013 we identified 9,092 unique patients with MINOCA out of 199,163 MI admissions in total. Incidence rate ratios (IRR) were calculated for whole hours, parts of the day, weekdays, months, seasons and major holidays.

Results

The mean age was 65.5 years, 62.0% were women and 16.6% presented with STEMI. The risk for MINOCA proved to be most common in the morning (IRR = 1.70, 95% CI [1.63–1.84]) with a peak at 08.00 AM (IRR = 2.25, 95% CI [1.96–2.59]) and on Mondays (IRR = 1.28, 95% CI [1.18–1.38]). No altered risk was detected during the different seasons, the Christmas and New Year holidays or the Swedish Midsummer festivities. There was no association between time of onset of MINOCA and short- or long-term prognosis.

Conclusion

The onset of MINOCA shows a circadian and circaseptan variation with increased risk at early mornings and Mondays, similar to previous studies on all MI, suggesting stress related triggering. However, during holidays were traditional MI increase, we did not see any increase for MINOCA. No association was detected between time of onset and prognosis, indicating that the underlying pathological mechanisms of MINOCA and the quality of care are similar at different times of onset but triggering mechanism may be more active early mornings and Mondays.

Deficiency of Bmal1 disrupts the diurnal rhythm of haemostasis

BACKGROUND

Mice deficient in the circadian clock gene BMAL1 (Brain and Muscle ARNT-like protein-1) exhibit a hypercoagulable state and an enhanced arterial and venous thrombogenicity, which aggravates with age. We investigated the effect of BMAL1 deficiency in mice at a different age on the diurnal rhythm of factors involved in coagulation and fibrinolysis.

MATERIALS AND METHODS

Hepatic, cardiac and brain tissues were isolated from 10- and 25-weeks-old Bmal1-deficient (BMAL1-/-) and wild-type (BMAL1+/+) mice at ZT2 and at ZT14 to analyze the mRNA expression level of genes involved in coagulation and fibrinolysis.

RESULTS

Body weight and brain weight were significantly lower in all BMAL1-/- versus BMAL1+/+ mice. Bmal1 deficiency disturbed the diurnal rhythm of plasminogen activator inhibitor-1 (PAI-1) in liver and plasma, but not in cardiac or brain tissues. BMAL1+/+ livers showed diurnal fluctuations in factor (F)VII, FVII, protein S and anti-thrombin gene expression, which were not observed in BMAL1-/- tissues. Interestingly, tissue plasminogen activator (t-PA) expression was significantly upregulated in all BMAL1-/- versus BMAL1+/+ brains at both time points. Plasma t-PA-PAI-1 complex levels were however similar for all groups.

CONCLUSION

Bmal1 deficiency affected the biphasic rhythm of coagulation and fibrinolysis factors predominantly in the liver. In the brain, Bmal1-dependent control of t-PA gene expression was documented for the first time.

Genetic variations in circadian rhythm genes and susceptibility for myocardial infarction

Disruption of endogenous circadian rhythms has been shown to increase the risk of developing myocardial infarction (MI), suggesting that circadian genes might play a role in determining disease susceptibility. We conducted a case-control study on 200 patients hospitalized due to MI and 200 healthy controls, investigating the association between MI and single nucleotide polymorphisms (SNPs) in four circadian genes (ARNTL, CLOCK, CRY2, and PER2). The variants of all four genes were chosen based on their previously reported association with cardiovascular risk factors, which have a major influence on the occurrence of myocardial infarction. Statistically significant differences, assessed through Chi-square analysis, were found in genotype distribution between cases and controls of the PER2 gene rs35333999 (p=0.024) and the CRY2 gene rs2292912 (p=0.028); the corresponding unadjusted odds ratios, also significant, were respectively OR=0.49 (95% CI 0.26-0.91) and OR=0.32 (95% CI 0.11-0.89). Our data suggest that genetic variability in the CRY2 and PER2 genes might be associated with myocardial infarction.

"Summer Shift": A Potential Effect of Sunshine on the Time Onset of ST-Elevation Acute Myocardial Infarction

Background

ST‐elevation acute myocardial infarction (STEMI) represents one of the leading causes of death. The time of STEMI onset has a circadian rhythm with a peak during diurnal hours, and the occurrence of STEMI follows a seasonal pattern with a salient peak of cases in the winter months and a marked reduction of cases in the summer months. Scholars investigated the reason behind the winter peak, suggesting that environmental and climatic factors concur in STEMI pathogenesis, but no studies have investigated whether the circadian rhythm is modified with the seasonal pattern, in particular during the summer reduction in STEMI occurrence.

Methods and Results

Here, we provide a multiethnic and multination epidemiological study (from both hemispheres at different latitudes, n=2270 cases) that investigates whether the circadian variation of STEMI onset is altered in the summer season. The main finding is that the difference between numbers of diurnal (6:00 to 18:00) and nocturnal (18:00 to 6:00) STEMI is markedly decreased in the summer season, and this is a prodrome of a complex mechanism according to which the circadian rhythm of STEMI time onset seems season dependent.

Conclusions

The “summer shift” of STEMI to the nocturnal interval is consistent across different populations, and the sunshine duration (a measure related to cloudiness and solar irradiance) underpins this season‐dependent circadian perturbation. Vitamin D, which in our results seems correlated with this summer shift, is also primarily regulated by the sunshine duration, and future studies should investigate their joint role in the mechanisms of STEMI etiogenesis.

Circadian Periodicity of Ischemic Heart Disease: A Systematic Review of the Literature

The authors performed a MEDLINE search to identify reports, published during the last 20 years, focused on circadian variation of acute myocardial infarction (AMI), and prevalence and the ratios between the number of events per hour during the morning and the other hours of the day were calculated. Despite the optimization of interventional and medical therapy of AMI since the first reports of circadian patterns in AMI occurrence, it was found that such a pattern still exists and that AMI happens most frequently in the morning hours.

Acute gastrointestinal bleeding cases presenting to the emergency department are associated with age, sex and seasonal and circadian factors

BACKGROUND

Gastrointestinal bleeding (GIB) is one of the most common emergencies in gastroenterology. The aim of this study was to investigate the association between the incidence of GIB and seasonal, circadian and meteorological patterns in the emergency department (ED) of a tertiary hospital.

PATIENTS AND METHODS

From January 2007 until December 2012, we retrospectively evaluated patients presenting to the ED with respect to the number and location of GIB, season, time of day and weather.

RESULTS

Of 45 458 patients, 578 (1.3%) presented with a GIB. Of these, 62.5% were men compared with 54.7% of all patients in the ED (χ, P=0.0002). Patients with GIB were on average 4.4 years older than those without GIB (95% confidence interval 2.76-5.98, t-test, P<0.001). In addition, 304 (52.6%) patients had upper GIB and 138 (23.9%) had lower GIB. In total, 136 (23.5%) patients required no endoscopy because of initial laboratory and circulatory stability. In univariate analysis, meteorological parameters, including air temperature, cloud cover, relative humidity, vapour pressure, amount of precipitation, sunshine duration and snow height, were each associated with an increased risk of acute GIB (all P-values<0.05). In the 6-year study period, patients with GIB presented to the ED mainly during the winter months. Independent predictors of GIB on multivariate logistic regression were older age, male sex, season and daytime, all P less than 0.005. Emergency admissions during the night were associated with a 54 and 35% higher risk of GIB compared with daytime (8 a.m. to 4 p.m., P=0.0002) and late evening hours (4 p.m. to midnight, P=0.0142), respectively.

CONCLUSION

Presentation of patients with acute GIB in the ED is age and sex specific and shows seasonal and circadian differences in distribution, with an increased incidence in winter months and during night-time. This should be considered when determining possible emergency endoscopic interventions and the availability of emergency endoscopy services.

Chronobiology of Takotsubo Syndrome and Myocardial Infarction: Analogies and Differences

Several pathophysiologic factors, not harmful if taken alone, are capable of triggering unfavorable events when presenting together within the same temporal window (chronorisk), and the occurrence of many cardiovascular events is not evenly distributed in time. Both acute myocardial infarction and takotsubo syndrome seem to exhibit a temporal preference in their onset, characterized by variations according to time of day, day of the week, and month of the year, although with both analogies and differences.

Bromocriptine-QR therapy for the management of type 2 diabetes mellitus: developmental basis and therapeutic profile summary

An extended series of studies indicate that endogenous phase shifts in circadian neuronal input signaling to the biological clock system centered within the hypothalamic suprachiasmatic nucleus (SCN) facilitates shifts in metabolic status. In particular, a diminution of the circadian peak in dopaminergic input to the peri-SCN facilitates the onset of fattening, insulin resistance and glucose intolerance while reversal of low circadian peak dopaminergic activity to the peri-SCN via direct timed dopamine administration to this area normalizes the obese, insulin resistant, glucose intolerant state in high fat fed animals. Systemic circadian-timed daily administration of a potent dopamine D2 receptor agonist, bromocriptine, to increase diminished circadian peak dopaminergic hypothalamic activity across a wide variety of animal models of metabolic syndrome and type 2 diabetes mellitus (T2DM) results in improvements in the obese, insulin resistant, glucose intolerant condition by improving hypothalamic fuel sensing and reducing insulin resistance, elevated sympathetic tone, and leptin resistance. A circadian-timed (within 2 hours of waking in the morning) once daily administration of a quick release formulation of bromocriptine (bromocriptine-QR) has been approved for the treatment of T2DM by the U.S. Food and Drug Administration. Clinical studies with such bromocriptine-QR therapy (1.6 to 4.8 mg/day) indicate that it improves glycemic control by reducing postprandial glucose levels without raising plasma insulin. Across studies of various T2DM populations, bromocriptine-QR has been demonstrated to reduce HbA1c by -0.5 to -1.7. The drug has a good safety profile with transient mild to moderate nausea, headache and dizziness as the most frequent adverse events noted with the medication. In a large randomized clinical study of T2DM subjects, bromocriptine-QR exposure was associated with a 42% hazard ratio reduction of a pre-specified adverse cardiovascular endpoint including myocardial infarction, stroke, hospitalization for congestive heart failure, revascularization surgery, or unstable angina. Bromocriptine-QR represents a novel method of treating T2DM that may have benefits for cardiovascular disease as well.

Prevention of cardiovascular events with antiplatelet treatment: does time of intake matter for aspirin and ADP receptor blockers?

Long-term evidence supports a clustering of cardiovascular events in the early morning. Several studies have shown that platelet hyper-reactivity to various stimuli is also present at this period of the day. However, the idea of treatment strategies reflecting the circadian variation in platelet reactivity has been largely neglected so far, and this is true despite the huge number of patients being treated with these drugs. Some pharmacodynamic data suggest that early-morning platelet hyper-reactivity may be overcome by shifting aspirin intake to the bedtime. However, there is lack of evidence whether shifting the time of intake or splitting the daily dose of P2Y12-inhibitors with a regular QD dosing (clopidogrel or prasugrel) to the evening would be effective to overcome platelet hyper-reactivity or to suppress the excess of cardiovascular events observed during morning hours. Further research is warranted to clarify whether such a simple and costless effort like dose shifting or splitting may be beneficial to prevent cardiovascular events.

Influence of the Cardiomyocyte Circadian Clock on Cardiac Physiology and Pathophysiology

Cardiac function and dysfunction exhibit striking time-of-day-dependent oscillations. Disturbances in both daily rhythms and sleep are associated with increased risk of heart disease, adverse cardiovascular events, and worsening outcomes. For example, the importance of maintaining normal daily rhythms is highlighted by epidemiologic observations that night shift workers present with increased incidence of cardiovascular disease. Rhythmicity in cardiac processes is mediated by a complex interaction between extracardiac (e.g., behaviors and associated neural and humoral fluctuations) and intracardiac influences. Over the course of the day, the intrinsic properties of the myocardium vary at the levels of gene and protein expression, metabolism, responsiveness to extracellular stimuli/stresses, and ion homeostasis, all of which affect contractility (e.g., heart rate and force generation). Over the past decade, the circadian clock within the cardiomyocyte has emerged as an essential mechanism responsible for modulating the intrinsic properties of the heart. Moreover, the critical role of this mechanism is underscored by reports that disruption, through genetic manipulation, results in development of cardiac disease and premature mortality in mice. These findings, in combination with reports that numerous cardiovascular risk factors (e.g., diet, diabetes, aging) distinctly affect the clock in the heart, have led to the hypothesis that aberrant regulation of this mechanism contributes to the etiology of cardiac dysfunction and disease. Here, we provide a comprehensive review on current knowledge regarding known roles of the heart clock and discuss the potential for using these insights for the future development of innovative strategies for the treatment of cardiovascular disease.

Altered Daytime Fluctuation Pattern of Plasminogen Activator Inhibitor 1 in Type 2 Diabetes Patients with Coronary Artery Disease: A Strong Association with Persistently Elevated Plasma Insulin, Increased Insulin Resistance, and Abdominal Obesity

This study was aimed at investigating daily fluctuation of PAI-1 levels in relation to insulin resistance (IR) and daily profile of plasma insulin and glucose levels in 26 type 2 diabetic (T2D) patients with coronary artery disease (CAD) (group A), 10 T2D patients without CAD (group B), 12 nondiabetics with CAD (group C), and 12 healthy controls (group D). The percentage of PAI-1 decrease was lower in group A versus group B (4.4 ± 2.7 versus 35.0 ± 5.4%; P < 0.05) and in C versus D (14.0 ± 5.8 versus 44.7 ± 3.1%; P < 0.001). HOMA-IR was higher in group A versus group B (P < 0.05) and in C versus D (P < 0.01). Simultaneously, AUCs of PAI-1 and insulin were higher in group A versus group B (P < 0.05) and in C versus D (P < 0.01), while AUC of glucose did not differ between groups. In multiple regression analysis waist-to-hip ratio and AUC of insulin were independent determinants of decrease in PAI-1. The altered diurnal fluctuation of PAI-1, especially in T2D with CAD, might be strongly influenced by a prolonged exposure to hyperinsulinemia in the settings of increased IR and abdominal obesity, facilitating altogether an accelerated atherosclerosis.

Circadian influences on myocardial infarction

Components of circadian rhythm maintenance, or "clock genes," are endogenous entrainable oscillations of about 24 h that regulate biological processes and are found in the suprachaismatic nucleus (SCN) and many peripheral tissues, including the heart. They are influenced by external cues, or Zeitgebers, such as light and heat, and can influence such diverse phenomena as cytokine expression immune cells, metabolic activity of cardiac myocytes, and vasodilator regulation by vascular endothelial cells. While it is known that the central master clock in the SCN synchronizes peripheral physiologic rhythms, the mechanisms by which the information is transmitted are complex and may include hormonal, metabolic, and neuronal inputs. Whether circadian patterns are causally related to the observed periodicity of events, or whether they are simply epi-phenomena is not well established, but a few studies suggest that the circadian effects likely are real in their impact on myocardial infarct incidence. Cycle disturbances may be harbingers of predisposition and subsequent response to acute and chronic cardiac injury, and identifying the complex interactions of circadian rhythms and myocardial infarction may provide insights into possible preventative and therapeutic strategies for susceptible populations.