REM-related bradyarrhythmia syndrome

Arrhythmia and Time of Day in Maintenance Hemodialysis: Secondary Analysis of the Monitoring in Dialysis Study

Rationale & Objective

The incidence of arrhythmia varies by time of day. How this affects individuals on maintenance dialysis is uncertain. Our objective was to quantify the relationship of arrhythmia with the time of day and timing of dialysis.

Study Design

Secondary analysis of the Monitoring in Dialysis study, a multicenter prospective cohort study.

Settings & Participants

Loop recorders were implanted for continuous cardiac monitoring in 66 participants on maintenance dialysis with a follow up of 6 months.

Exposure

Time of day based on 6-hour intervals.

Outcomes

Event rates of clinically significant arrhythmia.

Analytical Approach

Negative binomial mixed effects regression models for repeated measures were used to evaluate data from the Monitoring in Dialysis study for differences in diurnal patterns of clinically significant arrhythmia among those with end-stage kidney disease with heart failure and end-stage kidney disease alone. We additionally analyzed rates according to presence of heart failure, time of dialysis shift, and dialysis versus nondialysis day.

Results

Rates of clinically significant arrhythmia peaked between 12:00 AM and 5:59 AM and were more than 1.5-fold as frequent during this interval than the rest of the day. In contrast, variations in atrial fibrillation peaked between 6:00 AM and 11:59 AM, but variations across the day were qualitatively small. Clinically significant arrhythmia occurred at numerically higher rate in individuals with end-stage kidney disease and heart failure (5.9 events/mo; 95% CI, 1.3-26.8) than those without heart failure (4.0 events/mo; 95% CI, 0.9-17.9). Although differences in overall rate were not significant, their periodicity was significantly different (P < 0.001), with a peak between 12:00 AM and 6:00 AM with kidney failure alone and between 6:00 AM and 11:59 AM in those with heart failure. Although the overall clinically significant arrhythmia rate was similar in morning compared with evening dialysis shifts (P = 0.43), their periodicity differed with a peak between 12:00 AM and 5:59 AM in those with AM dialysis and a later peak between 6:00 AM and 11:59 AM in those with PM shifts.

Limitations

Post hoc analysis, unable to account for unmeasured confounders.

Conclusion

Clinically significant arrhythmias showed strong diurnal patterns with a maximal peak between 12:00 AM and 5:59 AM and noon. Although overall arrhythmia rates were similar, the peak rate occurred overnight in individuals without heart failure and during the morning in individuals with heart failure. Further exploration of the influence of circadian rhythm on arrhythmia in the setting of hemodialysis is needed.

Correlation Between Rapid Eye Movement Sleep Duration and Laryngopharyngeal Reflux in Patients with Obstructive Sleep Apnea

Objectives: The aim of this study was to investigate the correlation between rapid eye movement (REM) sleep duration and laryngopharyngeal reflux (LPR) in patients with obstructive sleep apnea (OSA). Methods: In all, 99 patients with OSA were enrolled in this study, and the correlation between REM sleep duration and the severity of LPR was analyzed after the polysomnography (PSG) and reflux symptom index (RSI) scores were completed. Subsequently, a multiple linear regression analysis was performed to further clarify the factors affecting LPR. Results: Partial correlation analysis showed that the REM sleep duration was positively correlated with the RSI scores (r = 0.236, P = .022) after controlling for apnea-hypopnea index (AHI), body mass index (BMI), lowest oxygen saturation (LSO2), age, and sex. The multiple linear regression analysis indicated that only REM sleep duration was a factor influencing LPR (t = 2.330, P = .022). Conclusions: Our study found a correlation between REM sleep duration and LPR in OSA patients. The shorter the REM sleep duration, the less severe the LPR symptoms.

Differences among young unwitnessed sudden cardiac death, according to time from last seen alive: Insights from a 15-year nationwide study

BACKGROUND

More than half of all sudden cardiac deaths (SCDs) are unwitnessed, but the composition of the unwitnessed SCD population is poorly described.

OBJECTIVE

The purpose of this study was to compare clinical and autopsy characteristics of young unwitnessed SCD subjects, based on the time from last contact to being found dead.

METHODS

All unwitnessed SCD subjects aged 1-35 years in Denmark from 2000-2014 identified through a multisource approach were included. Time from last seen alive to being found dead was dichotomized to <1 hour or 1-24 hours. Clinical characteristics and autopsy results were compared, and predictors of autopsy were assessed by logistic regression.

RESULTS

Of 440 unwitnessed SCD subjects, 366 (83%) had not been seen alive within 1 hour of being found dead. Comorbidities differed between the groups, with more epilepsy (17% vs 5%) and psychiatric diseases (13% vs 7%) in the 24-hour group. Patients in the 24-hour group died more frequently during sleep (64% vs 23%), the autopsy rate was higher (75% vs 61%), and deaths were more often unexplained after autopsy (69% vs 53%). Having been seen within 1 hour of death independently decreased the chance of being autopsied (odds ratio 0.51; 95% confidence interval 0.27-1.00; P = .0497).

CONCLUSION

The majority of unwitnessed SCD subjects had not been seen alive within 1 hour of being found dead. Clinical- and autopsy-related characteristics differed between the 2 groups. Differences were mainly attributable to death-related circumstances and comorbidities. Excluding SCD cases not seen alive within 1 hour of being found dead would severely underestimate the burden of SCD.

Effects of age and sex on vasomotor activity and baroreflex sensitivity during the sleep-wake cycle

Cardiovascular function is related to age, sex, and state of consciousness. We hypothesized that cardiovagal baroreflex sensitivity (BRS) demonstrates different patterns in both sexes before and after 50 years of age and that these patterns are associated with patterned changes during the sleep-wake cycle. We recruited 67 healthy participants (aged 20-79 years; 41 women) and divided them into four age groups: 20-29, 30-49, 50-69, and 70-79 years. All the participants underwent polysomnography and blood pressure measurements. For each participant, we used the average of the arterial pressure variability, heart rate variability (HRV), and BRS parameters during the sleep-wake stages. BRS and HRV parameters were significantly negatively correlated with age. The BRS indexes were significantly lower in the participants aged ≥ 50 years than in those aged < 50 years, and these age-related declines were more apparent during non-rapid eye movement sleep than during wakefulness. Only BRS demonstrated a significantly negative correlation with age in participants ≥ 50 years old. Women exhibited a stronger association than men between BRS and age and an earlier decline in BRS. Changes in BRS varied with age, sex, and consciousness state, each demonstrating a specific pattern. The age of 50 years appeared to be a crucial turning point for sexual dimorphism in BRS. Baroreflex modulation of the cardiovascular system during sleep sensitively delineated the age- and sex-dependent BRS patterns, highlighting the clinical importance of our results. Our findings may aid in screening for neurocardiac abnormalities in apparently healthy individuals.

Raw and Wine Processed Schisandra chinensis Regulate NREM-Sleep and Alleviate Cardiovascular Dysfunction Associated with Insomnia by Modulating HPA Axis

Clinical studies have shown that insomnia and anxiety are usually accompanied by cardiovascular dysfunction. In traditional Chinese medicine, Schisandra chinensis (SC) and wine processed Schisandra chinensis (WSC) are mainly used for the treatment of dysphoria, palpitation and insomnia. However, little attention was paid to its mechanism. In this study, we monitored the effect of SC and WSC on the nervous system and cardiovascular system of free-moving rats in the real-time. Our results show that SC and WSC can alleviate cardiovascular dysfunction while promoting sleep, and we further explored their potential mechanisms. HPLC-QTOF-MS was used for the quality control of chemical components in SC and WSC. Data sciences international (DSI) physiological telemetry system was applied to collect the electroencephalogram (EEG), electrocardiogram (ECG) and other parameters of free-moving rats to understand the effects of long-term intake of SC and WSC on rats. The content of Cortisol (CORT), neurotransmitters and amino acids in rat pituitary and hypothalamus were analyzed by UPLC-MS to determine the activity of HPA axis. The expression of melatonin receptor MT1 was analyzed by immunofluorescence technique. Our results suggested that SC and WSC may play the role of promoting sleep by increasing the expression level of melatonin receptor MT1 in hypothalamus, and modulate the activity of HPA axis by regulating the levels of the related neurotransmitters and amino acid, so as to improve the abnormal cardiovascular system of rats. This study may provide theoretical support for explicating the advantages of SC and other phytomedicines in the treatment of insomnia.

Aging Disrupts Normal Time-of-Day Variation in Cardiac Electrophysiology

BACKGROUND

Cardiac gene expression and arrhythmia occurrence have time-of-day variation; however, daily changes in cardiac electrophysiology, arrhythmia susceptibility, and Ca²⁺ handling have not been characterized. Furthermore, how these patterns change with age is unknown.

METHODS

Hearts were isolated during the light (zeitgeber time [ZT] 4 and ZT9) and dark cycle (ZT14 and ZT21) from adult (12-18 weeks) male mice. Hearts from aged (18-20 months) male mice were isolated at ZT4 and ZT14. All hearts were Langendorff-perfused for optical mapping with voltage- and Ca²⁺-sensitive dyes (n=4-7/group). Cardiac gene and protein expression were assessed with real-time polymerase chain reaction (n=4-6/group) and Western blot (n=3-4/group).

RESULTS

Adult hearts had the shortest action potential duration (APD) and Ca²⁺ transient duration (CaTD) at ZT14 (APD₈₀: ZT4: 45.4±4.1 ms; ZT9: 45.1±8.6 ms; ZT14: 34.7±4.2 ms; ZT21: 49.2±7.6 ms, P<0.05 versus ZT4 and ZT21; and CaTD₈₀: ZT4: 70.1±3.3 ms; ZT9: 72.7±2.7 ms; ZT14: 64.3±3.3 ms; ZT21: 74.4±1.2 ms, P<0.05 versus other time points). The pacing frequency at which CaT alternans emerged was faster, and average CaT alternans magnitude was significantly reduced at ZT14 compared with the other time points. There was a trend for decreased spontaneous premature ventricular complexes and pacing-induced ventricular arrhythmias at ZT14, and the hearts at ZT14 had diminished responses to isoproterenol compared with ZT4 (ZT4: 49.5.0±5.6% versus ZT14: 22.7±9.5% decrease in APD, P<0.01). In contrast, aged hearts exhibited no difference between ZT14 and ZT4 in nearly every parameter assessed (except APD₈₀: ZT4: 39.7±1.9 ms versus ZT14: 33.8±3.1 ms, P<0.01). Gene expression of KCNA5 (potassium voltage-gated channel subfamily A member 5; encoding Kv1.5) was increased, whereas gene expression of ADRB1 (encoding β1-adrenergic receptors) was decreased at ZT14 versus ZT4 in adult hearts. No time-of-day changes in expression or phosphorylation of Ca²⁺ handling proteins (SERCA2 [sarco/endoplasmic reticulum Ca²⁺-ATPase], RyR2 [ryanodine receptor 2], and PLB [phospholamban]) was found in ex vivo perfused adult isolated hearts.

CONCLUSIONS

Isolated adult hearts have strong time-of-day variation in cardiac electrophysiology, Ca²⁺ handling, and adrenergic responsiveness, which is disrupted with age.

Association of Short Sleep Duration and Atrial Fibrillation

BACKGROUND

Short sleep may be a risk factor for atrial fibrillation. However, previous investigations have been limited by lack of objective sleep measurement and small sample size. We sought to determine the association between objectively measured sleep duration and atrial fibrillation.

METHODS

All 31,079 adult patients undergoing diagnostic polysomnography from 1999 to 2015 at multiple sites within a large hospital network were identified from electronic medical records. Prevalent atrial fibrillation was identified by continuous ECG during polysomnography. Incident atrial fibrillation was identified by diagnostic codes and 12-lead ECGs. Logistic regression and Cox proportional hazards modeling were used to examine the association of sleep duration and atrial fibrillation prevalence and incidence, respectively, adjusting for age, sex, BMI, hypertension, coronary artery disease, cerebrovascular disease, peripheral vascular disease, heart failure, and sleep apnea severity.

RESULTS

We identified 404 cases of prevalent atrial fibrillation among 30,061 individuals (mean age ± SD, 51.0 ± 14.5 years; 51.6% women) undergoing polysomnography. After adjustment, each 1-h reduction in sleep duration was associated with a 1.17-fold (95% CI, 1.11-1.30) increased risk of prevalent atrial fibrillation. Among 27,589 patients without atrial fibrillation at baseline, we identified 1,820 cases of incident atrial fibrillation over 4.6 years median follow-up. After adjustment, each 1-h reduction in sleep duration was associated with a 1.09-fold (95% CI, 1.05-1.13) increased risk for incident atrial fibrillation.

CONCLUSIONS

Short sleep duration is independently associated with prevalent and incident atrial fibrillation. Further research is needed to determine whether interventions to extend sleep can lower atrial fibrillation risk.

Coxsackie B2 Virus Infection Causing Multiorgan Failure and Cardiogenic Shock in a 42-Year-Old Man

Infections from coxsackie B2 viruses often cause viral myocarditis and, only rarely, multisystem organ impairment. We present the unusual case of a 42-year-old man in whom coxsackie B2 virus infection caused multiorgan infection, necessitating distal pancreatectomy, splenectomy, renal dialysis, and venoarterial extracorporeal membrane oxygenation with mechanical ventilation. In addition, the patient had a rapid-eye-movement sleep-related conduction abnormality that caused frequent sinus pauses of longer than 10 s, presumably due to myocarditis from the coxsackievirus infection. He recovered after permanent pacemaker placement and was discharged from the hospital. We discuss our aggressive supportive care and the few other reports of multiorgan impairment from coxsackieviruses.

Circadian rhythm of cardiac electrophysiology, arrhythmogenesis, and the underlying mechanisms

Cardiac arrhythmias are a leading cause of cardiovascular death. It has long been accepted that life-threatening cardiac arrhythmias (ventricular tachycardia, ventricular fibrillation, and sudden cardiac death) are more likely to occur in the morning after waking. It is perhaps less well recognized that there is a circadian rhythm in cardiac pacemaking and other electrophysiological properties of the heart. In addition, there is a circadian rhythm in other arrhythmias, for example, bradyarrhythmias and supraventricular arrhythmias. Two mechanisms may underlie this finding: (1) a central circadian clock in the suprachiasmatic nucleus in the hypothalamus may directly affect the electrophysiology of the heart and arrhythmogenesis via various neurohumoral factors, particularly the autonomic nervous system; or (2) a local circadian clock in the heart itself (albeit under the control of the central clock) may drive a circadian rhythm in the expression of ion channels in the heart, which in turn varies arrhythmic substrate. This review summarizes the current understanding of the circadian rhythm in cardiac electrophysiology, arrhythmogenesis, and the underlying molecular mechanisms.

A rare case of REM sleep-related bradyarrhythmia syndrome with concomitant severe hypertension: a case report and a review of literature

Introduction

Rapid eye movement (REM) sleep-related bradyarrhythmia syndrome is characterized by pathological asystoles during the REM sleep phase. It is a rare rhythm disorder, being reported only few times in the literature. Due to non-specific symptoms, REM sleep-related bradyarrhythmia might be often underdiagnosed. Other cardiac diseases associated with pathological sinus arrests must be excluded to establish the correct diagnosis of and appropriate therapy for REM sleep-related bradyarrhythmia. We report a case of this syndrome followed by hypertension and diastolic heart failure.

The case

A 49-year-old male with severe hypertension presented for a cardiologist's consultation. His main complaints were palpitations, fatigue, dyspnoea, and snoring. Polysomnography test revealed a normal sleep structure with episodes of bradycardia and increased parasympathetic activity during phasic events of REM sleep. Heart rate variability Poincare plot analysis demonstrated similar results. REM sleep-related bradyarrhythmia syndrome was diagnosed and patient was treated with dual chamber heart pacemaker implantation.

Discussion

Various components of the autonomic nervous system influence the development of REM sleep-related bradyarrhythmia syndrome. The main factor is likely an increased vagal tone during the phasic REM sleep with the absence of normal compensatory sympathetic activity. Concomitant hypertension in REM sleep-related bradyarrhythmia syndrome is caused by a paradoxically abnormal control of the autonomic nervous system and can be explained through the acetylcholine metabolism pathway. Best suited diagnostic and treatment options for REM sleep-related bradyarrhythmia syndrome are discussed.

Conclusions

Patients with REM sleep-related bradyarrhythmia syndrome often present with indistinct symptoms. Polysomnography is an essential diagnostic test for the differential diagnosis of various nocturnal arrhythmias and sleep disorders. Severe hypertension is a common complication of sleep disorders and requires appropriate treatment of the underlying condition. An implantation of a heart pacemaker is the first-choice treatment for patients with REM sleep-related bradyarrhythmia syndrome.

Sleep related bradyarrhythmic events and heart rate variability in apparently healthy individuals

OBJECTIVE

It is thought that abnormal cardiac impulses of the autonomic nervous system during sleep are responsible for sleep-related bradyarrhythmias. Despite a proposed common etiopathogenesis and having common name of "sleep-related bradyarrhythmias," precise importance of sinoatrial or atrioventricular (AV) node involvement remains elusive. This study aimed to determine whether there is a difference in sleeprelated bradyarrhythmias from the point of view of heart rate variability (HRV).

METHODS

Patients were evaluated using 24-hour Holter electrocardiogram monitor. After careful medical evaluation, apparently healthy individuals with sleep-related sinus pauses ≥2 seconds on at least 1 occasion or those in whom Mobitz type I AV block occurred were included. Frequency and time domain analyses were conducted for daytime, nighttime, and 24-hour period.

RESULTS

Total of 37 patients with sinus pause(s), 40 patients with Mobitz type I AV block(s), and 40 healthy controls were included. On HRV analyses, all time and frequency domain parameters were better in sinus pause group for daytime, nighttime, and 24-hour average (p<0.05 for all). Results of heart rate-corrected HRV analyses still showed significantly better total power (TP) and very low frequency (VLF) in the sinus pause group compared with AV block group (TP: 7.1x10-3 vs. 5.4x10-3, p=0.011; VLF: 4.9x10-3 vs. 3.7x10-3, p=0.007).

CONCLUSION

Despite proposed common autonomic mechanisms, sleep-related sinus pause cases demonstrated better HRV profile in comparison with Mobitz type I AV block.

Screening and managing obstructive sleep apnoea in nocturnal heart block patients: an observational study

Background

Nocturnal heart block often occurs in patients with obstructive sleep apnoea (OSA). It is more likely to be undiagnosed in heart block patients who are ignorant of the symptoms of sleep disorder. Berlin Questionnaire (BQ) is a highly reliable way to discover the risk factors of OSA, whereas the validity in sleep-related heart block patients is uncertain. We performed an observational study to address these issues and confirmed the potential protective effect of continuous positive airway pressure (CPAP).

Methods

Patients who were previously diagnosed with nocturnal heart block with R-R pauses exceeding 2 seconds were retrospective screened from the ECG centre of Zhongshan hospital. These recruited participants completed Berlin Questionnaire and underwent polysomnography synchronously with 24-hour Holter monitoring. A cross-sectional analysis was performed to confirm the association between nocturnal arrhythmia and OSA, as well as to assess the diagnostic accuracy of the BQ. Subsequently, subjects diagnosed with OSA (apnoea-hypopnoea index > 5) underwent 3 consecutive days of CPAP therapy. On the third day, patients repeated 24-hour Holter monitoring within the institution of CPAP.

Results

The symptoms of disruptive snoring and hypersomnolence in 72 enrolled patients were more related to the occurrence of nocturnal heart block (r = 0.306, 0.226, respectively, p = 0.015, 0.019) than syncope (r = 0.134, p = 0.282) and palpitations (r = 0.106, p = 0.119), which were prominent trait of our study population. The sensitivity, specificity, positive and negative predictive value of the BQ at a cut-off point of 5 of AHI for detecting OSA in heart block patients was 81.0 %, 44.4 %, 91.07 % and 25 %. Nocturnal heart block does not appear to occur exclusively in severe sleep apnoea. The frequent occurrence of arrhythmias in prominent oxygen desaturation supports the correlation between them. CPAP therapy resulted in significant decrease in the average number of episodes of heart block, from 148.58 ± 379.44 to 16.07 ± 58.52 (p < 0.05), same to the change of the longest RR pausing time (from 4.38 ± 2.95 s to 0.57 ± 1.05 s, p = 0.169) in 51 patients. The optimal therapy pressure to make the observed arrhythmia disappeared is 12 cm H₂O.

Conclusion

Concerning high prevalence of OSA in heart block patients, BQ provided an economical and efficient screening method for OSA. For better management, CPAP therapy is feasible to prevent heart blocks avoiding unnecessary concomitant pacemaker implantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-016-0333-8) contains supplementary material, which is available to authorized users.

Rare Case of Rapidly Worsening REM Sleep Induced Bradycardia

Sinoatrial arrest also known as sinus pause occurs when sinoatrial node of the heart transiently ceases to generate the electrical impulse necessary for the myocardium to contract. It may last from 2.0 seconds to several minutes. Etiologies of sinoatrial arrest can be complex and heterogeneous. During rapid eye movement (REM) sleep, sinus arrests unrelated to apnea or hypopnea are very rare and only a few cases have been reported. Here we report a case of 36-year-old male with no significant past medical history who presented to our hospital after a syncopal episode at night. Physical examination showed no cardiac or neurological abnormalities and initial EKG and neuroimaging were normal. Overnight telemonitor recorded several episodes of bradyarrhythmia with sinus arrest that progressively lengthened over time. Sleep study was done which confirmed that sinus arrests occurred more during REM sleep and are unrelated to apnea or hypopnea. Electrophysiology studies showed sinus nodal dysfunction with no junctional escape, subsequently a dual chamber pacemaker placed for rapidly worsening case of REM sleep induced bradycardia.

Selective atrial vagal denervation guided by spectral mapping to treat advanced atrioventricular block

AIMS

Asymptomatic nocturnal long ventricular pauses are usually detected accidentally and it has been suggested that they may lead to sudden death. Identification of predisposing factors could prevent cardiovascular events.

METHODS AND RESULTS

We report the case of a patient with frequent asymptomatic nocturnal ventricular pauses of 3-11 s, characteristic of a vagally mediated atrioventricular (AV) block. Echocardiography, treadmill test, thyroid function test levels, and polysomnogram were normal. In an attempt to reduce the risk, it was decided that an atrial vagal denervation induced by radiofrequency (RF) ablation (cardioneuroablation) could be useful. Spectral mapping was used to localize endocardial vagal innervation in the right and left aspects of the inter-atrial septum, responsible for the sinus node and AV node modulation, and RF pulses were applied in those sites only. After finishing the procedure, significant changes were observed in the heart rate (66-90 b.p.m.), atrial-His interval (115-74 ms), Wenckebach cycle length (820-570 ms), and sinus node recovery time (1100-760 ms). Follow-up Holter recording demonstrated that the number of ventricular pauses had reduced from 438 to 0. Heart rate and time domain characteristics were compatible with vagal denervation.

CONCLUSION

Ablation of the endocardial vagal innervation sites seems to be safe and efficient in reducing the frequency and the length of the ventricular pauses. It was possible by identifying certain spectral components of the atrial electrogram, resulting in a conservative approach.

Sleep-disordered breathing increases the risk of arrhythmias

Sleep-disordered breathing (SDB) has been consistently associated with increased risk for cardiovascular diseases, including arrhythmias. The purpose of this review is to elucidate the several pathophysiologic pathways such as repetitive hypoxia and reoxygenation, increased oxidative stress, inflammation and sympathetic activation that may underlie the increased incidence of arrhythmias in SDB patients. We discuss in particular the incidence of ventricular arrhythmias, atrial fibrillation and bradyarrhythmias in SDB patients. In addition, we discuss the electrocardiographic alteration such as ST-T changes during apneic events and QT dispersion induced by SDB that may trigger complex ventricular arrhythmias and sudden cardiac death. Finally, we consider also the therapeutic interventions such as continuous positive airways pressure therapy, a standard treatment for SDB, that may reduce the incidence and recurrence of supraventricular and ventricular arrhythmias in patients with SDB.

Ventricular standstill: An uncommon electrophysiological abnormality caused by profound vagal tone

CONTEXT

Ventricular standstill (VS) is an uncommon electrophysiological phenomenon and usually manifests as syncope. Rarely has a case been reported where the patient has been totally asymptomatic, and it has resolved spontaneously.

CASE REPORT

We report a case of complete VS and high-degree atrioventricular (AV) block in a 50-year-old female, who was admitted for nausea, vomiting, and chest pain. The patient never had a syncopal episode, even though she was in VS for more than 10 s.

CONCLUSION

Such degree of conduction abnormality without any syncope has not been reported so far. Her electrophysiological abnormality was attributed to profound vagotonic effect and was treated with a permanent pacemaker.

Function and modulation of premotor brainstem parasympathetic cardiac neurons that control heart rate by hypoxia-, sleep-, and sleep-related diseases including obstructive sleep apnea

Parasympathetic cardiac vagal neurons (CVNs) in the brainstem dominate the control of heart rate. Previous work has determined that these neurons are inherently silent, and their activity is largely determined by synaptic inputs to CVNs that include four major types of synapses that release glutamate, GABA, glycine, or serotonin. Whereas prior reviews have focused on glutamatergic, GABAergic and glycinergic pathways, and the receptors in CVNs activated by these neurotransmitters, this review focuses on the alterations in CVN activity with hypoxia-, sleep-, and sleep-related cardiovascular diseases including obstructive sleep apnea.

Circadian variation of heart rate variability across sleep stages

STUDY OBJECTIVES

Nocturnal cardiovascular events are more frequent at the beginning and end of the night. It was proposed that this pattern reflects the nocturnal distribution of sleep and sleep stages. Using heart rate variability (HRV), we recently showed an interaction between the circadian system and vigilance states on the regulation of cardiac rhythmicity. Here, we further investigate this interaction in order to clarify the specific effects of sleep stages on the regulation of the heart.

DESIGN

Participants underwent a 72-h ultradian sleep-wake cycle procedure in time isolation consisting of alternating 60-min wake episodes in dim light and 60-min nap opportunities in total darkness.

SETTING

Time isolation suite.

PATIENTS OR PARTICIPANTS

Fifteen healthy young participants; two were subsequently excluded.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

The current study revealed that sleep onset and progression to deeper sleep stages was associated with a shift toward greater parasympathetic modulation, whereas rapid eye movement (REM) sleep was associated with a shift toward greater sympathetic modulation. We found a circadian rhythm of heart rate (HR) and high-frequency power during wakefulness and all non-REM sleep stages. A significant circadian rhythm of HR and sympathovagal balance of the heart was also observed during REM sleep. During slow wave sleep, maximal parasympathetic modulation was observed at ∼02:00, whereas during REM sleep, maximal sympathetic modulation occurred in the early morning.

CONCLUSION

The circadian and sleep stage-specific effects on heart rate variability are clinically relevant and contribute to the understanding of the degree of cardiovascular vulnerability during sleep.

Rem sleep brady-arrhythmias: an indication to pacemaker implantation?

OBJECTIVES

Important adjustments in the autonomic nervous system occur during sleep. Bradycardia, due to increased vagal tone, and hypotension, caused by reduction of sympathetic activity, may occur during non rapid eye movement (REM) sleep (NREM). Increased sympathetic activity, causing increased heart rate, is conversely a feature of phasic REM sleep. During REM sleep, sinus arrests and atrioventricular (AV) blocks unrelated to apnea or hypopnea have been described. These arrhythmias are very rare and only a few cases have been reported in the literature.

PATIENTS/METHODS

Following an ECG performed for other reasons, two patients with no history of sleep complaints nor symptoms of heart failure or heart attack were referred to our center for nocturnal brady-arrhythmias.

RESULTS

24h ECG Holter recorded several episodes of brady-arrhythmia with sinus arrest in the first patients and brady-arrhythmias with complete AV block in the second patient. In both patients, episodes of brady-arrhythmia were prevalent in the second part of the night. Nocturnal polysomnography (PSG) demonstrated that episodes occurred only during REM sleep, particularly during phasic events. Treatment with pacemaker was considered only for the patient with complete AV blocks.

CONCLUSIONS

These types of brady-arrhythmias are usually detected accidentally due to their lack of symptoms. It has been suggested that in some patients they may lead to sudden unexpected death. Thus, the identification of predisposing factors is mandatory in order to prevent potentially dangerous arrhythmic events.