OSA and Cardiac Arrhythmogenesis: Mechanistic Insights

Circular RNA Expression Profiles and Bioinformatic Analysis in Mouse Models of Obstructive Sleep Apnea-Induced Cardiac Injury: Novel Insights Into Pathogenesis

Circular RNAs (circRNAs) participate in the development of various kinds of diseases. However, the function and roles of circRNAs in obstructive sleep apnea (OSA)-induced cardiovascular disease remain poorly understood. Therefore, we sought to explore the circRNA expression profiles and predict their functions in OSA-induced cardiac injury with the use of bioinformatics analysis. The model of OSA was established in mouse treated by chronic intermittent hypoxia (CIH) exposure. Then, we screened the circRNA profile using circRNA microarray. By comparing circRNA expression in three matched pairs of CIH-treated cardiac tissues and controls, differentially expressed circRNAs were identified in the CIH groups. Comparison of the selected circRNAs expression levels was performed between qRT-PCR and microarray. Meanwhile, we employed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses to predict the functions of these selected circRNAs. Finally, we constructed a circRNA-miRNA-mRNA network based on the target prediction. It was found that a total of 124 circRNAs were differentially expressed in CIH-treated cardiac tissues (p ≤ 0.05, fold-change ≥ 1.5). Among them, 23 circRNAs were significantly down-regulated, and the other 101 were up-regulated. Then, ten circRNAs were randomly selected to validate the reliability of the microarray results by using qRT-PCR. Next, we conducted the GO and KEGG pathway analysis to explore the parental genes functions of differentially expressed circRNA. Finally, two significantly differentially expressed circRNAs (mmu_circRNA_014309 and mmu_circRNA_21856) were further selected to create a circRNA-miRNA-mRNA regulation network. Our study did first reveal that the differentially expressed circRNAs played a vital role in the pathogenesis of OSA-induced cardiac damage. Thus, our findings bring us closer to unraveling the pathophysiologic mechanisms and eliciting novel therapeutic targets for the treatment of OSA-associated cardiovascular diseases.

Ventrikuläre Arrhythmien bei obstruktiver und zentraler Schlafapnoe

Hintergrund

Ventrikuläre Arrhythmien treten mit einer hohen Prävalenz auf und sind mit einer hohen Morbidität und Mortalität assoziiert. Sowohl die obstruktive (OSA) als auch die zentrale (ZSA) Schlafapnoe können auf Grund ihrer Pathophysiologie zu vermehrten ventrikulären Arrhythmien beitragen.

Ziel

Dieser Artikel soll die komplexen Zusammenhänge und Erkenntnisse jüngster Forschungen bezüglich schlafbezogenen Atmungsstörungen (SBAS) und ventrikulärer Arrhythmien und deren Therapiemöglichkeiten beleuchten.

Material und Methoden

Es erfolgte eine Literaturrecherche basierend auf prospektiven, retrospektiven, klinischen und experimentellen Studien sowie Reviews, Metaanalysen und aktuellen Leitlinien, die seit 2014 in der Medline-Datenbank gelistet wurden.

Ergebnisse

Es besteht ein bidirektionaler Zusammenhang zwischen der SBAS und ventrikulären Arrhythmien. Intermittierende Hypoxie, oxidativer Stress, wiederkehrende Arousals, intrathorakale Druckschwankungen und kardiales Remodeling tragen im Rahmen der SBAS zu einer erhöhten ventrikulären Arrhythmieneigung bei. Der Schweregrad der OSA, gemessen mittels Apnoe-Hypopnoe-Index, ist mit der Prävalenz ventrikulärer Arrhythmien assoziiert. Ähnliche Ergebnisse liegen für Patienten mit ZSA und Herzinsuffizienz vor. Studien zu ventrikulären Arrhythmien bei ZSA-Patienten ohne Herzinsuffizienz fehlen. Eine Positivdrucktherapie (PAP) bei OSA- oder ZSA-Patienten führte in verschiedenen Studien zu einer reduzierten Anzahl an ventrikulären Arrhythmien. Dieser Zusammenhang konnte jedoch nicht in allen Studien bestätigt werden. Ventrikuläre Arrhythmien treten bei der OSA gehäuft nachts auf, bei der ZSA gleichmäßig über den Tag verteilt.

Diskussion

Bisherige Studien weisen einen Zusammenhang zwischen der OSA bzw. der ZSA und ventrikulären Arrhythmien trotz unterschiedlicher Pathophysiologie nach. Hinsichtlich des Effektes der PAP auf ventrikuläre Arrhythmien bei Patienten mit OSA und ZSA sind weitere Studien erforderlich.

Hypertension in Children with Obstructive Sleep Apnea Syndrome-Age, Weight Status, and Disease Severity

Older age, obesity, and obstructive sleep apnea syndrome (OSAS) are known to increase the risk of hypertension in adults. However, data for children are scarce. This study aimed to investigate the relationships between hypertension, age, weight status, and disease severity in 396 children with OSAS. The prevalence rates of hypertension, obesity, and severe OSAS (apnea-hypopnea index ≥10) were 27.0%, 28.0%, and 42.9%, respectively. Weight z-score and apnea-hypopnea index were independently correlated with systolic blood pressure z-score, and minimal blood oxygen saturation (SpO₂) was independently associated with diastolic blood pressure z-score. Overall, late childhood/adolescence (odds ratio (OR) = 1.72, 95% CI = 1.05–2.81), obesity (OR, 2.58, 95% CI = 1.58–4.22), and severe OSAS (OR = 2.38, 95% CI = 1.48–3.81) were independent predictors of pediatric hypertension. Furthermore, late childhood/adolescence (OR = 2.50, 95% CI = 1.10–5.71) and abnormal SpO₂ (mean SpO₂ < 95%; OR = 4.91, 95% CI = 1.81–13.27) independently predicted hypertension in obese children, and severe OSAS (OR = 2.28, 95% CI = 1.27–4.10) independently predicted hypertension in non-obese children. In conclusion, obesity, OSAS severity, and abnormal SpO₂ are potentially modifiable targets to improve hypertension while treating children with OSAS.

Obstructive Sleep Apnea and Cardiac Arrhythmias: A Contemporary Review

Obstructive sleep apnea (OSA) is a highly prevalent disorder with a growing incidence worldwide that closely mirrors the global obesity epidemic. OSA is associated with enormous healthcare costs in addition to significant morbidity and mortality. Much of the morbidity and mortality related to OSA can be attributed to an increased burden of cardiovascular disease, including cardiac rhythm disorders. Awareness of the relationship between OSA and rhythm disorders is variable among physicians, a fact that can influence patient care, since the presence of OSA can influence the incidence, prevalence, and successful treatment of multiple rhythm disorders. Herein, we provide a review of this topic that is intentionally broad in scope, covering the relationship between OSA and rhythm disorders from epidemiology and pathophysiology to diagnosis and management, with a particular focus on the recognition of undiagnosed OSA in the general clinical population and the intimate relationship between OSA and atrial fibrillation.

Severity of spleep apnea syndrome and life-threatening tachyarrhythmias in patients with implantable cardioverter defibrillator

BACKGROUND

Sleep apnea syndrome (SAS) has been reported to be associated with a higher incidence of ventricular arrhythmias. The aim of this study was twofold: (1) to investigate whether in SAS patients receiving an implantable cardioverter defibrillator (ICD) the severity of SAS was associated with the occurrence of ventricular arrhythmias; (2) to assess whether changes in nocturnal apnoic/hypopnoic episodes may favor the occurrence of life-threatening arrhythmias, that is, sustained ventricular tachycardia (VT)/fibrillation (VF), requiring ICD intervention.

METHODS

We enrolled 46 patients with documented SAS at polysomnography (apnea/hypopnea index [AHI] > 5) who also had a left ventricle ejection fraction (LVEF) < 35% and, according to primary prevention indications, implanted an ICD (Boston Scientific Incepta) able to daily monitor apnoic/hypopnoic episodes occurring during sleep. Patients were followed at 3-month intervals.

RESULTS

At a mean follow-up of 18 months, 21 episodes of sustained VT/FV requiring ICD intervention were documented in eight patients (17.4%). Baseline AHI was significantly higher in patients with compared to those without ICD intervention. ICD interventions, however, were not preceded by any worsening of apnoic/hypopnoic episodes. The respiratory disturbance index (RDI) of the week during the event, indeed, was not different from that recorded during the previous 2 weeks (25.4 ± 11, 25.6 ± 10 and 25.1 ± 10, respectively; p = .9).

CONCLUSIONS

In patients with SAS who received an ICD for primary prevention of sudden death, those with ICD interventions showed a more severe form of the disease at baseline. ICD interventions, however, were not preceded by any significant changes in SAS severity.

Microbiota Modulates Cardiac Transcriptional Responses to Intermittent Hypoxia and Hypercapnia

The microbiota plays a critical role in regulating organismal health and response to environmental stresses. Intermittent hypoxia and hypercapnia, a condition that represents the main hallmark of obstructive sleep apnea in humans, is known to induce significant alterations in the gut microbiome and metabolism, and promotes the progression of atherosclerosis in mouse models. To further understand the role of the microbiome in the cardiovascular response to intermittent hypoxia and hypercapnia, we developed a new rodent cage system that allows exposure of mice to controlled levels of O₂ and CO₂ under gnotobiotic conditions. Using this experimental setup, we determined the impact of the microbiome on the transcriptional response to intermittent hypoxia and hypercapnia in the left ventricle of the mouse heart. We identified significant changes in gene expression in both conventionally reared and germ-free mice. Following intermittent hypoxia and hypercapnia exposure, we detected 192 significant changes in conventionally reared mice (96 upregulated and 96 downregulated) and 161 significant changes (70 upregulated and 91 downregulated) in germ-free mice. Only 19 of these differentially expressed transcripts (∼10%) were common to conventionally reared and germ-free mice. Such distinct transcriptional responses imply that the host microbiota plays an important role in regulating the host transcriptional response to intermittent hypoxia and hypercapnia in the mouse heart.

Incidental electrocardiogram abnormalities in children undergoing polysomnography

STUDY OBJECTIVES

Monitoring electrocardiogram (ECG) is an integral component of pediatric polysomnography (PSG). There is limited data regarding arrhythmia and conduction disturbances in the pediatric population undergoing a PSG. In this work we present abnormal ECG findings during PSG in our sleep center.

METHODS

A retrospective chart review from children who underwent PSG read by a single Sleep Medicine physician in the last year was carried out. Findings in children without cardiac disease and with first or second degree atrioventricular block (AVB) were compared to those from children with premature ventricular contractions (PVC).

RESULTS

A total of 1,235 PSGs were included. Twenty-four children (9 girls and 15 boys) aged 2-17 years (median 9 years) were identified with arrhythmias or conduction disturbances (1.9%). Nineteen out of 24 of these children (79.2%) had obstructive apnea-hypopnea index (oAHI) > 1 event/h; this frequency was not significantly different from that found in the whole group of 1,235 children. No statistically significant difference was found between children with AVB or PVC. Seven out of nine children with AVB and seven out of 10 with PVC had oAHI > 1 event/h, while eight children with AVB out of nine and four out of 10 with PVC were males (Fisher exact test p=0.04). None of the children were found to have a structural or conduction abnormality when referred to cardiology.

CONCLUSIONS

Our study supports that ECG abnormalities are rare in PSGs of children and not associated with cardiac disease or sleep disorders but appear more commonly in males.

Obstructive Sleep Apnea and Cardiovascular Disease

Obstructive sleep apnea (OSA) presents as repetitive interruptions of ventilation >10 seconds during sleep as a result of upper airway obstruction resulting in increased respiratory effort. Intermittent hypoxia causes physiologic changes resulting in increased catecholamine production, increased total peripheral resistance, tachycardia, and increased venous return, leading to increased cardiac output, hypertension, tachyarrhythmias, left ventricular hypertrophy, and heart failure. OSA causes an abnormal dip on 24-hour ambulatory blood pressure monitoring. Definitive diagnosis is made by polysomnography. Continuous positive airway pressure (CPAP) remains the first-line treatment. Effective treatment using CPAP reduces blood pressure and is indispensable for proper management of atrial fibrillation.

Effect of Continuous Positive Airway Pressure on Arrhythmia in Atrial Fibrillation and Sleep Apnea: A Randomized Controlled Trial

RATIONALE

Sleep apnea (SA) is highly prevalent in patients with atrial fibrillation (AF), and both conditions are associated with adverse cardiovascular outcomes.

OBJECTIVES

To determine the effect of continuous positive airway pressure (CPAP) on AF burden.

METHODS

This open-label, parallel-group, randomized, controlled trial included patients with paroxysmal AF and moderate-to-severe SA (apnea-hypopnea index ≥15). Eligible patients were randomized (1:1) to 5 months' treatment with CPAP plus usual care (CPAP, n=55) or usual care alone (control, n=54) by a computerised system. Outcome assessment was blinded. The planned primary outcome was the difference between CPAP treatment and control in change of AF burden (% of time in AF), as measured by implantable loop recorder.

MEASUREMENTS AND MAIN RESULTS

A total of 579 patients with paroxysmal AF had respiratory polygraphy, of whom 244 (42.1%) had moderate-to-severe SA. Of these, 158 (64.8%) participated in the CPAP run-in period, of whom 40 (25.3%) patients did not tolerate the treatment. One-hundred-eight patients were available for the primary analysis. The mean time in AF decreased from 5.6% at baseline to 4.1% during the last three months of CPAP intervention and from 5.0% to 4.3% in the control group. The adjusted between-group difference at follow-up was -0.63 (95% confidence interval: -2.55 to 1.30) percentage points; P=0.52. Seven serious adverse events (13%) occurred in the CPAP group, and two (4%) occurred in the control group.

CONCLUSIONS

In patients with paroxysmal AF and SA, treatment with CPAP did not result in a statistically significant reduction in the burden of AF. Clinical trial registration available at www.clinicaltrials.gov, ID: NCT02727192.

Effects of continuous positive airway pressure treatment in obstructive sleep apnea patients with atrial fibrillation: A meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA) is correlated with atrial fibrillation (AF). Over the past decade, there has been an increasing interest in the relationship between OSA with continuous positive airway pressure (CPAP) and progression or recurrence of AF.

METHODS

This investigation was an analysis of studies searched in the Cochrane Library, PubMed, EMBASE, EBSCO, OVID, and Web of Science databases from inception to July 2020 to evaluate the recurrence or progression of AF in CPAP users, CPAP nonusers, and patients without OSA.

RESULTS

Nine studies with 14,812 patients were recruited. CPAP therapy reduced the risk of AF recurrence or progression by 63% in a random-effects model (24.8% vs 40.5%, risk ratio [RR] = 0.70, 95% confidence interval [CI] = 0.57-0.85, P = .035). Compared with non-OSA patients, AF recurrence or progression was much higher in CPAP nonusers (40.6% vs 21.1%, RR = 1.70, 95% CI = 1.19-2.43, P = .000). However, AF recurrence or progression in the CPAP group was similar to that in the non-OSA group (24.0% vs 21.1%, RR = 1.13, 95% CI = 0.87-1.47, P = .001). Begg correlation test and Egger regression test revealed no publication bias in this analysis.

CONCLUSIONS

OSA is a salient factor in the progression or recurrence of AF. CPAP therapy for OSA may contribute to reduction of AF in patients for whom radiofrequency ablation or direct current cardioversion is not performed.

TRIAL REGISTRATION

The protocol for this meta-analysis was registered on PROSPERO with a registration No. CRD42019135229.

Sleep Apnea and Atrial Fibrillation: Role of the Cardiac Autonomic Nervous System

Sleep apnea is highly associated with atrial fibrillation (AF), and both diseases are highly prevalent in the United States. The mechanistic underpinnings that contribute to their association remain uncertain, but numerous possible mechanisms have been proposed, including dysfunction of the cardiac autonomic nervous system (ANS). Studies have reported that apnea induces hyperactivity of the ANS, leading to increases in AF susceptibility. This review compiles the latest evidence on the role of the ANS in sleep-apnea-induced AF.

2021 ISHNE/HRS/EHRA/APHRS collaborative statement on mHealth in Arrhythmia Management: Digital Medical Tools for Heart Rhythm Professionals: From the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society describes the current status of mobile health ("mHealth") technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self-management are novel aspects of mHealth. The promises of predictive analytics but also operational challenges in embedding mHealth into routine clinical care are explored.

2021 ISHNE/ HRS/ EHRA/ APHRS collaborative statement on mHealth in Arrhythmia Management: Digital Medical Tools for Heart Rhythm Professionals: From the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology/ Heart Rhythm Society/ European Heart Rhythm Association/ Asia Pacific Heart Rhythm Society describes the current status of mobile health ("mHealth") technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self-management are novel aspects of mHealth. The promises of predictive analytics but also operational challenges in embedding mHealth into routine clinical care are explored.

2021 ISHNE / HRS / EHRA / APHRS Collaborative Statement on mHealth in Arrhythmia Management: Digital Medical Tools for Heart Rhythm Professionals: From the International Society for Holter and Noninvasive Electrocardiology / Heart Rhythm Society / European Heart Rhythm Association / Asia Pacific Heart Rhythm Society

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology / Heart Rhythm Society / European Heart Rhythm Association / Asia Pacific Heart Rhythm Society describes the current status of mobile health ("mHealth") technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self-management are novel aspects of mHealth. The promises of predictive analytics but also operational challenges in embedding mHealth into routine clinical care are explored.

The Association of Sleep Apnea and Cardiorespiratory Fitness With Long-Term Major Cardiovascular Events

OBJECTIVE

To determine the risk of long-term major adverse cardiovascular events (MACE) when sleep-disordered breathing (SDB) and decreased cardiorespiratory fitness (CRF) co-occur.

METHODS

We included consecutive patients who underwent symptom-limited cardiopulmonary exercise tests between January 1, 2005, and January 1, 2010, followed by first-time diagnostic polysomnography within 6 months. Patients were stratified based on the presence of moderate-to-severe SDB (apnea/hypopnea index ≥15 per hour) and decreased CRF defined as <70% predicted peak oxygen consumption (VO₂). Long-term MACE was a composite outcome of myocardial infarction (MI), coronary artery bypass graft (CABG), percutaneous coronary intervention (PCI), stroke or transient ischemic attack (TIA), and death, assessed until May 21, 2018. Cox-proportional hazard models were adjusted for factors known to influence CRF and MACE.

RESULTS

Of 498 included patients (60±13 years, 28.1% female), 175 (35%) had MACE (MI=17, PCI=14, CABG=13, stroke=20, TIA=12, deaths=99) at a median follow-up of 8.7 years (interquartile range=6.5 to 10.3 years). After adjusting for age, sex, beta blockers, systemic hypertension, diabetes mellitus, coronary artery disease, cardiac arrhythmia, chronic obstructive pulmonary disease, smoking, and use of positive airway pressure (PAP), decreased CRF alone (hazard ratio [HR]=1.91, 95% confidence interval [CI], 1.15 to 3.18; P=.01), but not SDB alone (HR=1.26, 95% CI, 0.75 to 2.13, P=.39) was associated with increased risk of MACE. Those with SDB and decreased CRF had greater risk of MACE compared with patients with decreased CRF alone (HR=1.85; 95% CI, 1.21 to 2.84; P<.005) after accounting for these confounders. The risk of MACE was attenuated in those with reduced CRF alone after additionally adjusting for adequate adherence to PAP (HR=1.59; 95% CI, 0.77 to 3.31; P=.21).

CONCLUSION

The incidence of MACE, especially mortality, was high in this sample. Moderate-to-severe SDB with concurrent decreased CRF was associated with higher risk of MACE than decreased CRF alone. These results highlight the importance of possibly including CRF in the risk assessment of patients with SDB and, conversely, that of screening for SDB in patients with low peak VO₂.

Obstructive Sleep Apnea Syndrome as a Trigger of Cardiac Arrhythmias

PURPOSE OF REVIEW

Obstructive sleep apnea syndrome (OSAS) has a high prevalence in western countries. Many papers have been published with the purpose of demonstrating that OSAS acts as an arrhythmia trigger and is responsible for an increase in cardiovascular morbidity and mortality. The aim of this study was to review our knowledge on this topic.

RECENT FINDINGS

There is a lot of evidence demonstrating the relationship between OSAS and arrhythmias, but there remains a lack of an interventional randomized trial to demonstrate that by treating OSAS we can reduce arrhythmia burden. OSAS is a highly prevalent illness in western countries and is clearly related to an increase in cardiovascular mortality and morbidity. Cardiac arrhythmias are triggered by a repetitive hypoxemia, hypercapnia, acidosis, intrathoracic pressure fluctuations, reoxygenation, and arousals during apnea and hypopnea episodes. Early diagnosis and treatment of these patients can reduce further cardiovascular morbidity and mortality.

Autonomic Dysfunction and Neurohormonal Disorders in Atrial Fibrillation

Atrial fibrillation (AF) is the most commonly diagnosed arrhythmia and eludes an efficacious cure despite an increasing prevalence and a significant association with morbidity and mortality. In addition to an array of clinical sequelae, the origins and propagation of AF are multifactorial. In recent years, the contribution from the autonomic nervous system has been an area of particular interest. This review highlights the relevant physiology of autonomic and neurohormonal contributions to AF origin and maintenance, the current state of the literature on targeted therapies, and the path forward for clinical interventions.

2021 ISHNE/HRS/EHRA/APHRS Collaborative Statement on mHealth in Arrhythmia Management: Digital Medical Tools for Heart Rhythm Professionals: From the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society describes the current status of mobile health ("mHealth") technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self-management are novel aspects of mHealth. The promises of predictive analytics but also operational challenges in embedding mHealth into routine clinical care are explored.

2021 ISHNE/HRS/EHRA/APHRS Expert Collaborative Statement on mHealth in Arrhythmia Management: Digital Medical Tools for Heart Rhythm Professionals: From the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia-Pacific Heart Rhythm Society

This collaborative statement from the International Society for Holter and Noninvasive Electrocardiology/Heart Rhythm Society/European Heart Rhythm Association/Asia-Pacific Heart Rhythm Society describes the current status of mobile health technologies in arrhythmia management. The range of digital medical tools and heart rhythm disorders that they may be applied to and clinical decisions that may be enabled are discussed. The facilitation of comorbidity and lifestyle management (increasingly recognized to play a role in heart rhythm disorders) and patient self-management are novel aspects of mobile health. The promises of predictive analytics but also operational challenges in embedding mobile health into routine clinical care are explored.

Obstructive sleep apnea increases heart rhythm disorders and worsens subsequent outcomes in elderly patients with subacute myocardial infarction

OBJECTIVE

Obstructive sleep apnea (OSA) is a potential cardiovascular risk. We aimed to investigate the association of OSA with heart rhythm disorders and prognosis in elderly patients with new-onset acute myocardial infarction (AMI).

METHODS

We prospectively enrolled 252 AMI elderly patients (mean age, 68.5 ± 6.9 years) who were undergoing revascularization and completed a sleep study during their hospitalization. All subjects were categorized into non-OSA (apnea–hypopnea index (AHI) < 15, n = 130) and OSA (AHI ≥ 15, n = 122) groups based on the AHI. The changes in the autonomic nervous system, incidence of arrhythmia during nocturnal sleep, and major adverse cardiovascular and cerebrovascular events (MACCEs) were compared between the groups.

RESULTS

The mean AHI value in all AMI patients was 22.8 ± 10.9. OSA patients showed higher levels of body mass index and peak high-sensitivity C-reactive protein and lower levels of minimum nocturnal oxygen saturation (MinSaO₂), as well as greater proportion of multivessel coronary artery disease (all P < 0.05). The OSA group also showed significant increases in heart rate variability and heart rate turbulence onset (both P < 0.05) and higher incidence of arrhythmia (including sinus, atrial, and ventricular in origin). At a median follow-up of 6 months (mean 0.8–1.6 years), OSA (AHI ≥ 15) combined with hypoxia (MinSaO ₂ ≤ 80%) was independently associated with the incidence of MACCEs (hazard ratio [HR]: 4.536; 95% confidence interval [CI]: 1.461−14.084,P = 0.009) after adjusting for traditional risk factors.

CONCLUSIONS

OSA and OSA-induced hypoxia may correlate with the severity of myocardial infarction, increase the occurrence of heart rhythm disorders in elderly subacute MI patients, and worsen their short-term poor outcomes.

Histopathological substrate of the atrial myocardium in the progression of obstructive sleep apnoea-related atrial fibrillation

BACKGROUND

Obstructive sleep apnoea (OSA) is closely related to atrial fibrillation (AF), and OSA-induced atrial structural remodelling is the basis of AF maintenance. However, the process of atrial structural remodelling during the progression of acute OSA to chronic OSA is still unclear.

OBJECTIVE

To investigate changes in the atrial myocardium in acute sleep apnoea (6 h) and chronic sleep apnoea (12 weeks) by echocardiography, atrial myocardium morphology analysis, PAS staining, TUNEL staining, Masson's trichrome staining and analyses of ultrastructural changes.

METHODS

Eighteen adult beagle dogs under general anaesthesia were used to establish an OSA model. The animals were divided into the control group, acute OSA group and chronic OSA group, and there were six animals in each group. Cardiac ultrasounds of dogs from the three groups were examined. Left and right atrial muscle tissues were taken for HE staining, PAS staining, TUNEL staining, Masson's trichrome staining and transmission electron microscopy.

RESULTS

In the acute OSA model, the left atrial diameter of the dogs began to increase 3 h after ventilation, and this difference was more obvious at 6 h. The morphology of the myocardial cells did not change significantly, but mitochondrial swelling was observed in some atrial myocytes at 3 h. In the chronic OSA model, the left atrial diameter gradually increased, the volume of the right and left atria increased, the glycogen and collagen volume fractions and apoptosis ratio were significantly increased in atrial myocytes, mitochondria swelling and lengthening occurred in some atrial myocytes, the matrix became lighter, the mitochondrial ridge density decreased and the myofilament arrangement was disordered. The disc was distorted and not continuous, and there was some cardiomyocyte necrosis.

CONCLUSION

With the prolongation of apnoea, the atrium gradually enlarges, myocardial cells become disordered, glycogen aggregates, the number of necrotic cells increases, fibrosis worsens, mitochondrial abnormalities occur and the arrangement of the discs are disordered, providing a basis for the maintenance of AF.

Prognostic Impact of Obstructive Sleep Apnea in Patients Presenting with Acute Symptomatic Pulmonary Embolism

BACKGROUND

 In patients with pulmonary embolism (PE), there is a lack of comprehensive data on the prevalence and prognostic significance of pre-existing obstructive sleep apnea (OSA).

METHODS

 In this study of patients with PE from the Registro Informatizado de la Enfermedad TromboEmbólica (RIETE) registry, we assessed the prevalence of OSA, and the association between pre-existing OSA and the outcomes of all-cause mortality, PE-related mortality, recurrences, and major bleeding over 30 days after initiation of PE treatment. Additionally, we also examined rates of outcomes within 90 days and 1 year following the diagnosis of PE.

RESULTS

 Of 4,153 patients diagnosed with PE, 241 (5.8%; 95% confidence interval [CI]: 5.1-6.6%) had pre-existing OSA. Overall, 166 (4.0%; 95% CI: 3.4-4.6%) died during the first 30 days of follow-up. In multivariable analysis, the OSA syndrome was not a significant predictor of death from any cause (odds ratio [OR]: 1.5; 95% CI: 0.8-2.9; p = 0.19). However, patients with pre-existing OSA had an increased PE-specific mortality (adjusted OR: 3.0; 95% CI: 1.3-6.8; p = 0.01) compared with those without OSA. OSA was not significantly associated with 30-day recurrent venous thromboembolism (adjusted OR: 0.6; 95% CI: 0.1-4.7; p = 0.65) or major bleeds (adjusted OR: 1.0; 95% CI: 0.4-2.2; p = 1.0). Findings were similar at 90-day and 1-year follow-ups.

CONCLUSION

 In patients presenting with PE, pre-existing OSA is relatively infrequent. Patients with OSA were at increased risk of PE-related mortality when compared with those without OSA.

The Role of Vitamin C in Two Distinct Physiological States: Physical Activity and Sleep

This paper is a literature overview of the complex relationship between vitamin C and two opposing physiological states, physical activity and sleep. The evidence suggests a clinically important bidirectional association between these two phenomena mediated by different physiological mechanisms. With this in mind, and knowing that both states share a connection with oxidative stress, we discuss the existing body of evidence to answer the question of whether vitamin C supplementation can be beneficial in the context of sleep health and key aspects of physical activity, such as performance, metabolic changes, and antioxidant function. We analyze the effect of ascorbic acid on the main sleep components, sleep duration and quality, focusing on the most common disorders: insomnia, obstructive sleep apnea, and restless legs syndrome. Deeper understanding of those interactions has implications for both public health and clinical practice.

Longer apneas and hypopneas are associated with greater ultra-short-term HRV in obstructive sleep apnea

Low long-term heart rate variability (HRV), often observed in obstructive sleep apnea (OSA) patients, is a known risk factor for cardiovascular diseases. However, it is unclear how the type or duration of individual respiratory events modulate ultra-short-term HRV and beat-to-beat intervals (RR intervals). We aimed to examine the sex-specific changes in RR interval and ultra-short-term HRV during and after apneas and hypopneas of various durations. Electrocardiography signals, recorded as a part of clinical polysomnography, of 758 patients (396 men) with suspected OSA were analysed retrospectively. Average RR intervals and time-domain HRV parameters were determined during the respiratory event and the 15-s period immediately after the event. Parameters were analysed in three pooled sex-specific subgroups based on the respiratory event duration (10-20 s, 20-30 s, and > 30 s) separately for apneas and hypopneas. We observed that RR intervals shortened after the respiratory events and the magnitude of these changes increased in both sexes as the respiratory event duration increased. Furthermore, ultra-short-term HRV generally increased as the respiratory event duration increased. Apneas caused higher ultra-short-term HRV and a stronger decrease in RR interval compared to hypopneas. In conclusion, the respiratory event type and duration modulate ultra-short-term HRV and RR intervals. Considering HRV and the respiratory event characteristics in the diagnosis of OSA could be useful when assessing the cardiac consequences of OSA in a more detailed manner.

Cardiac arrhythmias in poorly performing Standardbred and Norwegian-Swedish Coldblooded trotters undergoing high-speed treadmill testing

The significance of cardiac arrhythmias and their possible association with upper airway obstruction are frequently considered in the clinical investigation of poor performance. The specific aims of this retrospective study of a group of poorly performing Standardbred and Norwegian-Swedish Coldblooded trotters were to: (1) describe the overall frequency and frequency distributions of arrhythmias; (2) describe arrhythmia characteristics including percent prematurity, relative recovery cycle lengths and QRS morphology; (3) describe variability of normal RR intervals; and (4) explore possible associations between upper airway abnormalities and arrhythmia categories during peak exercise and recovery. The records of 103 trotters presented to the Norwegian University of Life Sciences for high-speed treadmill testing were reviewed. The occurrence of at least one arrhythmic event was high (77-78%) when considering all exercise periods and 6-10% prematurity criteria. Triplets, salvos, and/or paroxysmal tachyarrhythmias occurred in 8% of horses during peak exercise. Complex ventricular arrhythmias occurred in 15% of horses in the first 2 min of recovery. Evaluation of QRS morphology and return cycle lengths demonstrated areas of overlap in characteristics typically attributed to either supraventricular or ventricular arrhythmias. There was no association between airway diagnosis and arrhythmias during any exercise period. The maximum average HR during peak exercise was an excellent predicter for complex ventricular arrhythmias during recovery. Because perfect categorization of arrhythmias is not possible, future studies should report descriptive arrhythmia information. Prospective studies that evaluate various degrees of upper airway obstruction and the effect on known initiators of arrhythmogenesis are needed.

Coronary heart disease and atrial fibrillation: a vicious cycle

The population suffering from coronary heart disease (CHD) complicated by atrial fibrillation (AF) is rising rapidly. A strong correlation between the two diseases has been reported, and the many common risk factors they share may play prominent roles in their development. In addition, CHD can directly promote the progression of AF by affecting reentry formation, focal ectopic activity, and neural remodeling. At the same time, AF also affects CHD through three aspects: 1) atherosclerosis, 2) the mismatch of blood supply and oxygen consumption, and 3) thrombosis. In conclusion, CHD and AF can aggravate each other and seem to form a vicious cycle. For patients with CHD complicated by AF, principal studies and guidelines have focused on antithrombotic treatment and rhythm control, which are paramount for these patients. Of note, our review sheds light on the strategies to break the cycle of the two diseases, which may be fundamental to treat these patients and optimize the benefit.

Hypercapnia and hyperlactatemia were positively associated with higher-grade arrhythmias during peak exercise in horses during poor performance evaluation on a high-speed treadmill

Cardiac arrhythmias are common in horses during exercise, especially immediately post-exercise. The objectives of this study were to: (1) describe the frequency and type of cardiac arrhythmias detected in horses during incremental high-speed treadmill exercise testing (ITET); (2) determine if arterial blood gas (ABG) changes at peak and immediately post-exercise were associated with arrhythmias; and (3) determine whether upper or lower airway disease was associated with exercising cardiac arrhythmias. Horses (n = 368) presenting for an ITET underwent resting and exercising upper airway endoscopy, resting, exercising and post-exercise electrocardiography, resting and post-exercise echocardiography and exercising ABG. Arrhythmias were graded by the most severe arrhythmia present. Grade 1 arrhythmias were defined as one or two atrial (APCs) or ventricular premature complexes (VPCs), or one APC and one VPC, detected in 6.9% at peak and 16% at 0-2 min post exercise.. Grade 2 arrhythmias were >2 APCs or VPCs, or both, detected in 5.8% at peak and 16.6% at 0-2 min post exercise. Grade 3 included complex arrhythmias (couplets, triplets, R on T, multiform complexes or paroxysmal atrial or ventricular tachycardia), detected in 4.4% at peak and 7.3% at 0-2 min post exercise. Both partial pressure of arterial CO₂ (PaCO₂; P = 0.008) and lactate (P = 0.031) were significantly associated with arrhythmias occurring at peak exercise, but not immediately post-exercise. As PaCO₂ and lactate increased, arrhythmia severity increased. Blood pH was significantly associated with grades 2 and 3 arrhythmias at 0-2 min post ITET (OR = 0.0002; P < 0.001). There was no significant association between grades 2 and 3 cardiac arrhythmias, inflammatory airway disease (IAD), or exercise-induced pulmonary hemorrhage (EIPH). When adjusted for lactate concentration (P = 0.06), higher PaCO₂ concentrations in horses with and without exercising upper respiratory tract (URT) obstruction were associated with higher likelihood of grades 2 and 3 arrhythmias (P < 0.01). This study demonstrated that at peak exercise, with severe hypercapnia and hyperlactatemia, there was increased risk for grades 2 or 3 cardiac arrhythmias and, as the PaCO₂ and lactate values increased further, the severity of those arrhythmias increased.

Nocturnal Arrhythmias and Heart-Rate Swings in Patients With Obstructive Sleep Apnea Syndrome Treated With Beta Blockers

Background

The higher cardiovascular variability and the increased prevalence of arrhythmias in patients with obstructive sleep apneas may contribute to their higher rate of fatal events during sleep. In this regard, the use of beta blockers (BB) is debated because they may induce bradyarrhythmias and alter the pattern of heart rate changes induced by apneas. Thus, the aim of our study is to quantify peri‐apneic heart‐rate swings and prevalence of nocturnal bradyarrhythmias in BB‐treated and BB‐naïve patients with obstructive sleep apnea.

Methods and Results

Our real‐life, retrospective, cohort study analyzed data from patients with obstructive sleep apnea after a basal cardiorespiratory polysomnography. Among 228 eligible participants, we enrolled 78 BB‐treated and 88 BB‐naïve patients excluding those treated with antiarrhythmic drugs or pacemakers, or with uninterpretable ECG traces during polysomnography. In each patient, type and frequency of arrhythmias were identified and peri‐apneic changes of RR intervals were evaluated for each apnea. BB‐treated patients were older and with more comorbidities than BB‐naïve patients, but had similar obstructive sleep apnea severity, similar frequency of arrhythmic episodes, and similar prevalence of bradyarrhythmias. Apnea‐induced heart‐rate swings, unadjusted for age, showed lower RR interval changes in BB‐treated (133.5±63.8 ms) than BB‐naïve patients (171.3±87.7 ms, P=0.01), lower RR interval increases during apneas (58.5±28.5 versus 74.6±40.2 ms, P=0.01), and lower RR interval decreases after apneas (75.0±42.4 versus 96.7±55.5 ms, P<0.05).

Conclusions

BB appear to be safe in patients with obstructive sleep apnea because they are not associated with worse episodes of nocturnal bradyarrhythmias and even seem protective in terms of apnea‐induced changes of heart rate.

Continuous positive airway pressure effectively ameliorates arrhythmias in patients with obstructive sleep apnea-hypopnea via counteracting the inflammation

INTRODUCTION

This work is aimed at evaluating the therapeutic effect of continuous positive airway pressure (CPAP) in treatment of patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) combined with arrhythmias as well as clarifying the possible mechanism underpinning such an intervention.

METHODS

Through exclusions, a total of 108 OSAHS patients combined with arrhythmias were enrolled from June 2017 to June 2019 with full clinical information in this work. A computerized permuted block design with varying block stratification and size according to age, sex, AHI and type of arrhythmia was used to randomize 108 patients to CPAP versus sham CPAP for a period of 12-week. All were subjected to unchanged pharmacological anti-arrhythmia therapy combined with CPAP. Before and after CPAP treatment, the improvement of various arrhythmias was compared between the CPAP group and the sham-CPAP group. The levels of CRP, IL-6 and TNF-ɑ were measured simultaneously.

RESULTS

During follow-up, the mean (±SD) CPAP pressure used in the CPAP group was 12.3 (±3.1) cm H2O. The use of CPAP and sham CPAP was on average of 5.2 ± 0.56 and 5.1 ± 0.63 h/night, respectively. After 12 weeks of CPAP therapy, the AHI was significantly decreased and the lowest blood oxygen saturation was notably elevated in the CPAP group compared to the sham-CPAP group, P < 0.05. The CPAP therapy, compared with the sham-CPAP group, significantly reduced the incidence of all types of arrhythmia in patients with OSAHS. The level of the c-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) was significantly lower in the CPAP group than in the sham-CPAP group (P < 0.05). Pearson correlation analysis showed that the reduction in the incidence of total arrhythmias was positively correlated with the decrease of CRP, IL-6 and TNF-ɑ levels, respectively.

CONCLUSION

Findings from this work suggest that proper use of CPAP significantly benefits to OSAHS patients combined with arrhythmias, possibly via counteracting the inflammation.

Exercise-associated rhythm disturbances in poorly performing Thoroughbreds: risk factors and association with racing performance

BACKGROUND

Exercise-associated cardiac rhythm disturbances are common, but there is a lack of evidence-based criteria on which to distinguish clinically relevant rhythm disturbances from those that are not.

OBJECTIVES

To describe and characterise rhythm disturbances during clinical exercise testing; to explore potential risk factors for these rhythm disturbances and to determine whether they influenced future racing.

STUDY DESIGN

Retrospective cohort using a convenience sample.

METHODS

Medical records were reviewed from two clinical services to identify horses with poor performance and/or respiratory noise with both exercise endoscopy and electrocardiography results. Respiratory and ECG findings recorded by the attending clinicians were described, and for polymorphic ventricular rhythms (n = 12), a consensus team agreed the final rhythm characterisation. Several statistical models analysing risk factors were built and racing records were reviewed to compare horses with and without rhythm disturbance.

RESULTS

Of 245 racehorses, 87 (35.5%) had no ectopic/re-entrant rhythms, 110 (44.9%) had isolated premature depolarisations during sinus rhythm and 48 (19.6%) horses had complex tachydysrrythmias. Rhythm disturbances were detected during warm-up in 20 horses (8.2%); during gallop in 61 horses (24.9%) and during recovery in 124 horses (50.6%). Most complex rhythm events occurred during recovery, but there was one horse with a single couplet during gallop and another with a triplet during gallop. Fifteen horses (one with frequent isolated premature depolarisations and 14 complex rhythms) were considered by clinicians to be potentially contributing to poor performance. Treadmill exercise tests, the presence of exercise-associated upper respiratory tract obstructions and National Hunt racehorses were associated with rhythm disturbances. The proportion of horses racing again after diagnosis (82%) was similar in all groups and univariable analysis revealed no significant associations between subsequent racing and the presence of any ectopic/re-entrant rhythm, or the various sub-groups based on phase of exercise in which this was detected.

MAIN LIMITATIONS

Reliance on retrospective data collection from medical records with no control group. Exercise ECGs were collected using only 1 or 2 leads. Variables examined as risk factors could be considered to be inter-related and our sub-groups were small.

CONCLUSIONS

This study confirms a high prevalence of cardiac rhythm disturbances, including complex ectopic/re-entrant rhythms, in poorly performing racehorses. Detection of rhythm disturbances may vary with exercise test conditions and exercise-associated upper respiratory tract obstructions increase the risk of rhythm disturbances.

Correlation between apnea-hypopnea index and Tp-Te interval, Tp-Te/QT, and Tp-Te/QTc ratios in obstructive sleep apnea

Background

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder associated with important cardiovascular complications including ventricular arrhythmias. Tp‐Te interval, Tp‐Te/QT, and Tp‐Te/QTc ratios are repolarization indices representing ventricular arrhythmogenic potential. These parameters are associated with ventricular arrhythmias and sudden cardiac death. The aim of this study was to investigate the correlation between apnea–hypopnea index and Tp‐Te, Tp‐Te/QT, and Tp‐Te/QTc in OSA.

Methods

We screened a total of 280 patients who underwent overnight polysomnography (PSG) between the years 2012–2017 at our institution. Patients were assigned into four groups based on severity of apnea–hypopnea index: 70 with apnea–hypopnea index (AHI) <5 (control group), 71 with 5 ≤ AHI < 15, 63 with 15 ≤ AHI < 30, and 76 with AHI ≥ 30. Tp‐Te, Tp‐Te/QT, and Tp‐Te/QTc were measured.

Results

Compared to control group, repolarization parameters were significantly prolonged in other groups (Tp‐Te interval: 68.3 ± 6.8, 71.8 ± 6.3, 79.1 ± 5.5, and 85.1 ± 6.4 ms, p < .001; Tp‐Te/QT ratio: 167.5 ± 12.7, 181.7 ± 13.0, 202.2 ± 10.0 and 219.4 ± 13.5, p < .001; Tp‐Te/QTc ratio: 151.1 ± 16.6, 167.6 ± 16.6, 193.7 ± 14.4, and 225.5 ± 17.0, p < .001). There was a significant trend toward higher Tp‐Te, Tp‐Te/QT, and Tp‐Te/QTc across higher AHI categories. In a univariate regression analysis, body mass index, smoking status, Tp‐Te, and Tp‐Te/QTc were significantly associated with the severity of AHI in OSA. Tp‐Te (OR 1.629, 95% CI 1.393–1.906, p < .001), Tp‐Te/QTc (OR 1,333 95% CI 1.247–1.424, p < .001), and smoking status (OR 5.771, 95% CI 1.025–32.479, p = .047) were found to be significant independent predictors of severity of AHI in a multivariate analysis, after adjusting for other risk parameters.

Conclusions

Our study showed that Tp‐Te, Tp‐Te/QT, and Tp‐Te/QTc were prolonged in patients with OSA. There was significant correlation between apnea–hypopnea index and these parameters.

Sleep-Dependent Directional Interactions of the Central Nervous System-Cardiorespiratory Network

OBJECTIVE

We investigated the nature of interactions between the central nervous system (CNS) and the cardiorespiratory system during sleep.

METHODS

Overnight polysomnography recordings were obtained from 33 healthy individuals. The relative spectral powers of five frequency bands, three ECG morphological features and respiratory rate were obtained from six EEG channels, ECG, and oronasal airflow, respectively. The synchronous feature series were interpolated to 1 Hz to retain the high time-resolution required to detect rapid physiological variations. CNS-cardiorespiratory interaction networks were built for each EEG channel and a directionality analysis was conducted using multivariate transfer entropy. Finally, the difference in interaction between Deep, Light, and REM sleep (DS, LS, and REM) was studied.

RESULTS

Bidirectional interactions existed in central-cardiorespiratory networks, and the dominant direction was from the cardiorespiratory system to the brain during all sleep stages. Sleep stages had evident influence on these interactions, with the strength of information transfer from heart rate and respiration rate to the brain gradually increasing with the sequence of REM, LS, and DS. Furthermore, the occipital lobe appeared to receive the most input from the cardiorespiratory system during LS. Finally, different ECG morphological features were found to be involved with various central-cardiac and cardiac-respiratory interactions.

CONCLUSION

These findings reveal detailed information regarding CNS-cardiorespiratory interactions during sleep and provide new insights into understanding of sleep control mechanisms.

SIGNIFICANCE

Our approach may facilitate the investigation of the pathological cardiorespiratory complications of sleep disorders.

Association between Respiratory Sleep Indices and Cardiovascular Disease in Sleep Apnea-A Community-Based Study in Cyprus

Obstructive sleep apnea (OSA) is a chronic and prevalent disorder, strongly associated with cardiovascular disease (CVD). The apnea-hypopnea index (AHI), or respiratory event index (REI), and the oxygen desaturation index (ODI) are the clinical metrics of sleep apnea in terms of diagnosis and severity. However, AHI, or REI, does not quantify OSA-related hypoxemia and poorly predicts the consequences of sleep apnea in cardiometabolic diseases. Moreover, it is unclear whether ODI correlates with CVD in OSA. Our study aimed to examine the possible associations between respiratory sleep indices and CVD in OSA, in a non-clinic-based population in Cyprus. We screened 344 subjects of a stratified, total sample of 4118 eligible responders. All participants were adults (age 18+), residing in Cyprus. Each patient answered with a detailed clinical history in terms of CVD. A type III sleep test was performed on 282 subjects (81.97%). OSA (REI ≥ 15) was diagnosed in 92 patients (32.62%, Group A). REI < 15 was observed in the remaining 190 subjects (67.37%, Group B). In OSA group A, 40 individuals (43%) reported hypertension, 17 (18.5%) arrhythmias, 10 (11%) heart failure, 9 (9.8%) ischemic heart disease and 2 (2%) previous stroke, versus 46 (24%), 21 (11%), 7 (3.7%), 12 (6.3%) and 6 (3%), in Group B, respectively. Hypertension correlated with REI (p = 0.001), ODI (p = 0.003) and mean SaO₂ (p < 0.001). Arrhythmias correlated with mean SaO₂ (p = 0.001) and time spent under 90% oxygen saturation (p = 0.040). Heart failure correlated with REI (p = 0.043), especially in the supine position (0.036). No statistically significant correlations were observed between ischemic heart disease or stroke and REI, ODI and mean SaO₂. The pathogenesis underlying CVD in OSA is variable. According to our data, hypertension correlated with REI, ODI and mean SaO₂. Arrhythmias correlated only with hypoxemia (mean SaO₂), whereas heart failure correlated only with REI, especially in the supine position.

The relationship of obstructive sleep apnea and cardiovascular diseases from the perspective of evidence-based medicine. Part 1

The results of prospective studies, meta-analyzes and systematic reviews on the associations of obstructive sleep apnea (OSA) with various cardiovascular diseases (CVD) were analyzed. Currently, the mechanisms related to high prevalence of breathing-related sleep disorders among population of economically developed countries are clear, and an increase in the number of OSA patients has been shown. The relationship between OSA and CVD has been widely confirmed in large cohort studies. The first review part discusses the relationship of hypertension (HTN) and various heart arrhythmias (atrial fibrillation (AF), bradyarrhythmias, premature ventricular contraction, sudden death during sleep) with breathing-related sleep disorders. These groups of cardiovascular disorders currently show the most proven relationship with sleep apnea. In addition to cross-sectional studies indicating the high prevalence of OSA in patients with HTN and AF, some observational studies indicate an increase in the number of patients with HTN and paroxysmal AF with history of untreated sleep apnea. An analysis of the current issues of OSA phenotypes (in particular, REM-related OSA in hypertensive patients) as the most unfavorable cardiovascular factors is carried out.

Curcumin prevents chronic intermittent hypoxia-induced myocardial injury

Background:

Chronic intermittent hypoxia (IH), the hallmark feature of obstructive sleep apnoea syndrome, contributes to infarct size enhancement after myocardial ischemia–reperfusion (I/R). Curcumin (Curc), the natural pigment of Curcuma longa, has been demonstrated to be beneficial in the context of myocardial injury. In this study, we assessed the effects of Curc on the maladaptive cardiac response to IH, and particularly on IH-induced hypoxia inducible factor-1 (HIF-1) expression, oxidative stress, inflammation, endoplasmic reticulum (ER) stress and apoptosis.

Methods:

Swiss/SV129 mice were exposed to normoxia or IH (21–5% FiO₂, 60 s cycles, 8 h per day, for 21 days) and treated orally with Curc (100 mg kg⁻¹ day⁻¹, oral gavage) or its vehicle. Mice were then either euthanised for heart sampling in order to perform biochemical and histological analysis, or subjected to an in vivo ischemia-reperfusion protocol in order to measure infarct size.

Results:

IH increased nuclear HIF-1α expression and superoxide anion (O₂^.–) production as well as nuclear factor kappa B (NF-kB) p65, glucose-regulated protein (Grp78) and C/EBP homologous protein (CHOP) expression. IH also induced apoptosis and increased infarct size after I/R . The IH-induced HIF-1 activation, oxidative stress, inflammation, ER stress and apoptosis were abolished by chronic Curc treatment. Curc also significantly decreased infarct size only in mice exposed to IH.

Conclusion:

Curc prevents IH-induced myocardial cell death signalling. Curc might be used as a combined therapy with continuous positive airway pressure in sleep apnoea patients with high cardiovascular risk.

Attenuation of intermittent hypoxia-induced apoptosis and fibrosis in pulmonary tissues via suppression of ER stress activation

Background

Obstructive sleep apnea (OSA) is associated with pulmonary fibrosis and endothelial apoptosis in pulmonary tissues. Chronic intermittent hypoxia (IH) is considered to be the primary player in OSA, but the mechanisms underlying its effect on pulmonary tissues are unknown. Endoplasmic reticulum (ER) stress induced by IH treatment plays an important role in accelerating the process of fibrosis and induction of apoptosis.

Methods

Mice were placed in IH chambers for 4 weeks with an oscillating oxygen (O₂) concentration between 5 and 21%, cycling every 90s for 8 h daily. Mice were randomly divided into four groups: control group (normal oxygen), tauroursodeoxycholic acid (TUDCA) group (normal oxygen intraperitoneally injected with TUDCA), IH group and IH + TUDCA group. After 4 weeks, the proteins in three branch signaling pathways of ER stress, including protein kinase RNA (PKR)-like/Pancreatic ER kinase (PERK), activating transcription factor 6 (ATF-6) and inositol-requiring enzyme 1 (IRE-1), were evaluated. The cleaved caspase-3, caspase-12 and TUNNEL staining was assessed. Furthermore, the expression of transforming growth factor-β1 (TGF-β1) and thrombospondin-1(TSP-1), two extracellular matrix proteins that play critical role in fibrosis, were examined. Finally, Masson’s trichrome staining was performed to detect the expression of collagen.

Results

After 4 weeks of IH treatment, the expressions of two ER stress markers, glucose regulated protein-78 (Grp78) and transcription factor C/EBP homologous protein (CHOP) were increased which was prevented by administration of the ER stress attenuator, TUDCA. The expressions of PERK, but not those of ATF-6 and IRE-1, were increased. The effects of IH were accompanied by an increased number of apoptotic cells and increased expressions of cleaved caspase-3 and caspase-12 in pulmonary tissues. In addition, histological examination suggested the presence of fibrosis after chronic IH treatment, indicated by increased expression of collagen, which was associated with the up-regulation of TGF-β1 and TSP-1 that are known to promote fibrosis. Similarly, TUDCA could reduce the extent of fibrotic area and the expression levels of these proteins.

Conclusions

It reveals the roles of ER stress, especially the PERK pathway, in IH induced apoptosis and fibrosis in pulmonary tissues that might underlie the pulmonary complications observed in OSA.

Cardiac Afferent Denervation Abolishes Ganglionated Plexi and Sympathetic Responses to Apnea: Implications for Atrial Fibrillation

Background The autonomic nervous system response to apnea and its mechanistic connection to atrial fibrillation (AF) are unclear. We hypothesize that sensory neurons within the ganglionated plexi (GP) play a role. We aimed to delineate the autonomic response to apnea and to test the effects of ablation of cardiac sensory neurons with resiniferatoxin (RTX), a neurotoxic TRPV1 (transient receptor potential vanilloid 1) agonist. Methods Sixteen dogs were anesthetized and ventilated. Apnea was induced by stopping ventilation until oxygen saturations decreased to 80%. Nerve recordings from bilateral vagal nerves, left stellate ganglion, and anterior right GP were obtained before and during apnea, before and after RTX injection in the anterior right GP (protocol 1, n=7). Atrial effective refractory period and AF inducibility on single extrastimulation were assessed before and during apnea, and before and after intrapericardial RTX administration (protocol 2, n=9). GPs underwent immunohistochemical staining for TRPV1. Results Apnea increased anterior right GP activity, followed by clustered crescendo vagal bursts synchronized with heart rate and blood pressure oscillations. On further oxygen desaturation, a tonic increase in stellate ganglion activity and blood pressure ensued. Apnea-induced effective refractory period shortening from 110.20±31.3 ms to 90.6±29.1 ms ( P<0.001), and AF induction in 9/9 dogs versus 0/9 at baseline. After RTX administration, increases in GP and stellate ganglion activity and blood pressure during apnea were abolished, effective refractory period increased to 126.7±26.9 ms ( P=0.0001), and AF was not induced. Vagal bursts remained unchanged. GP cells showed cytoplasmic microvacuolization and apoptosis. Conclusions Apnea increases GP activity, followed by vagal bursts and tonic stellate ganglion firing. RTX decreases sympathetic and GP nerve activity, abolishes apnea's electrophysiological response, and AF inducibility. Sensory neurons play a role in apnea-induced AF.