Sleep apnea, heart failure, and pulmonary hypertension

The role of lncRNAs in intermittent hypoxia and sleep Apnea: A review of experimental and clinical evidence

In this narrative review, we present a comprehensive assessment on the putative roles of long non-coding RNAs (lncRNAs) in intermittent hypoxia (IH) and sleep apnea. Collectively, the evidence from cell culture, animal, and clinical research studies points to the functional involvement of lncRNAs in the pathogenesis, diagnosis, and potential treatment strategies for this highly prevalent disorder. Further research is clearly warranted to uncover the mechanistic pathways and to exploit the therapeutic potential of lncRNAs, thereby improving the management and outcomes of patients suffering from sleep apnea.

Role of TRPC3 in Right Ventricular Dilatation under Chronic Intermittent Hypoxia in 129/SvEv Mice

Patients with obstructive sleep apnea (OSA) exhibit a high prevalence of pulmonary hypertension and right ventricular (RV) hypertrophy. However, the exact molecule responsible for the pathogenesis remains unknown. Given the resistance to RV dilation observed in transient receptor potential canonical 3(Trpc3)^-/- mice during a pulmonary hypertension model induced by phenylephrine (PE), we hypothesized that TRPC3 also plays a role in chronic intermittent hypoxia (CIH) conditions, which lead to RV dilation and dysfunction. To test this, we established an OSA mouse model using 8- to 12-week-old 129/SvEv wild-type and Trpc3^-/- mice in a customized breeding chamber that simulated sleep and oxygen cycles. Functional parameters of the RV were evaluated through analysis of cardiac cine magnetic resonance images, while histopathological examinations were conducted on cardiomyocytes and pulmonary vessels. Following exposure to 4 weeks of CIH, Trpc3^-/- mice exhibited significant RV dysfunction, characterized by decreased ejection fraction, increased end-diastole RV wall thickness, and elevated expression of pathological cardiac markers. In addition, reactive oxygen species (ROS) signaling and the endothelin system were markedly increased solely in the hearts of CIH-exposed Trpc3^-/- mice. Notably, no significant differences in pulmonary vessel thickness or the endothelin system were observed in the lungs of wild-type (WT) and Trpc3^-/- mice subjected to 4 weeks of CIH. In conclusion, our findings suggest that TRPC3 serves as a regulator of RV resistance in response to pressure from the pulmonary vasculature, as evidenced by the high susceptibility to RV dilation in Trpc3^-/- mice without notable changes in pulmonary vasculature under CIH conditions.

International Consensus Statement on Obstructive Sleep Apnea

BACKGROUND

Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA).

METHODS

Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus.

RESULTS

The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated.

CONCLUSION

This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

The effect of CPAP therapy on heart rate variability in patients with obstructive sleep apnea

The aim of this study was to analyze the relationship between the initiation of CPAP therapy and HRV in patients with OSA. The study group consisted of 37 patients, aged 34-79 (mean 54.95 years) with OSA treated with CPAP. Two subgroups of patients were distinguished: less than severe (AHI < 30, n = 16) and severe OSA (AHI ≥ 30, n = 21). The second study was carried out around a month after the initiation of therapy. CPAP therapy caused the improvement in polysomnographic parameters, however, in most parameters in time and frequency analysis, there were no significant positive changes in parasympathetic tone. Moreover, in HRV time analysis, the reduced rMSSD and pNN50 parameters in the hours of night rest and rMSSD and SDSD during the 15-min N3 sleep period were noted. Especially, in the group with AHI ≥ 30, we observed significant decreases in rMSSD and pNN50 for the entire time. The changes were mainly for the night periods including the N3 sleep period, which is especially connected with sleep apnea (parameters: rMSSD, SDSD, and pNN50). In spectral analysis, the decrease in HF from the 15-min daily activity period and the N3 sleep period was observed. Inverse correlations were seen between the maximum, median, and mean positive airway pressure (PAP) and the change in rMSSD, SDNN, and SDSD, mainly during night hours and the N3 sleep period. Only in patients with AHI < 30 the increase in SDNN was observed in 15-min N3 sleep period. The beneficial increase in SDNN parameter from time analysis was observed only in one sleep period in less ill patients with OSA. The lack of significant changes was observed in the majority of the parameters of heart rate variability after initiation of CPAP therapy in a short observational time; however, the shift towards reduced HRV was observed in patients with AHI > 30, so the response to CPAP therapy may depends on the severity of the apnea. The results may suggest that a longer observational period is needed in such studies, and the problem is still not fully elucidated.

Disturbed Sleep is Not Good for the Heart: A Narrative Review

Sleep-related breathing disorders, including obstructive sleep apnea (OSA) and central sleep apnea (CSA), have a major impact on cardiovascular function. It has shown an association with hypertension, coronary artery disease, cardiac arrhythmias, sudden cardiac death, and congestive heart failure (CHF). This review focuses on highlighting the relationship between sleep apnea and CHF. We discuss the underlying pathophysiology, which involves the mechanical, neurohormonal, and inflammatory mechanisms; in addition, the similarities and differentiating clinical features of OSA in patients with CHF and without CHF. We have also discussed several treatment strategies, including weight loss, continuous positive airway pressure (CPAP), supplemental oxygen therapy, theophylline, acetazolamide, mandibular advancement device, and hypoglossal nerve stimulation (HGNS). We conclude that since there are several overlapping clinical features in patients with OSA with Heart Failure (HF) and without HF, early detection and treatment are crucial to decrease the risk of HF, coronary artery disease, and stroke.

Upregulation of IL-8, osteonectin, and myonectin mRNAs by intermittent hypoxia via OCT1- and NRF2-mediated mechanisms in skeletal muscle cells

Sleep apnoea syndrome is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]) and is a risk factor for insulin resistance/Type 2 diabetes. The induction of insulin resistance in skeletal muscle is a key phenomenon to develop diabetes. However, the mechanisms linking IH stress and insulin resistance remain elusive. We exposed human RD and mouse C2C12 muscle cells to normoxia or IH and measured their mRNA levels by real-time RT-PCR. We found that IH significantly increased the mRNA and protein levels of muscle-derived insulin resistance-factors (myokines) such as IL-8, osteonectin (ON), and myonectin (MN) in muscle cells. We further analysed the IH-induced expression mechanisms of IL-8, ON, and MN genes in muscle cells. Deletion analyses of the human myokine promoter(s) revealed that the regions -152 to -151 in IL-8, -105 to -99 in ON, and - 3741 to -3738 in MN promoters were responsible for the activation by IH in RD cells. The promoters contain consensus transcription factor binding sequences for OCT1 in IL-8 and MN promoters, and for NRF2 in ON promoter, respectively. The introduction of siRNA for OCT1 abolished the IH-induced expression(s) of IL-8 and MN and siRNA for NRF2 abolished the IH-induced expression of ON.

Upregulation of Reg IV and Hgf mRNAs by Intermittent Hypoxia via Downregulation of microRNA-499 in Cardiomyocytes

Sleep apnea syndrome (SAS) is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia [IH]), and is a risk factor for cardiovascular disease (CVD) and insulin resistance/Type 2 diabetes. However, the mechanisms linking IH stress and CVD remain elusive. We exposed rat H9c2 and mouse P19.CL6 cardiomyocytes to experimental IH or normoxia for 24 h to analyze the mRNA expression of several cardiomyokines. We found that the mRNA levels of regenerating gene IV (Reg IV) and hepatocyte growth factor (Hgf) in H9c2 and P19.CL6 cardiomyocytes were significantly increased by IH, whereas the promoter activities of the genes were not increased. A target mRNA search of microRNA (miR)s revealed that rat and mouse mRNAs have a potential target sequence for miR-499. The miR-499 level of IH-treated cells was significantly decreased compared to normoxia-treated cells. MiR-499 mimic and non-specific control RNA (miR-499 mimic NC) were introduced into P19.CL6 cells, and the IH-induced upregulation of the genes was abolished by introduction of the miR-499 mimic, but not by the miR-499 mimic NC. These results indicate that IH stress downregulates the miR-499 in cardiomyocytes, resulting in increased levels of Reg IV and Hgf mRNAs, leading to the protection of cardiomyocytes in SAS patients.

Downregulation of the Cd38-Cyclic ADP-Ribose Signaling in Cardiomyocytes by Intermittent Hypoxia via Pten Upregulation

Sleep apnea syndrome (SAS) is characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia, IH), and it is a risk factor for cardiovascular disease (CVD) and insulin resistance/type 2 diabetes. However, the mechanisms linking IH stress and CVD remain elusive. We exposed rat H9c2 and mouse P19.CL6 cardiomyocytes to experimental IH or normoxia for 24 h to analyze the mRNA expression of the components of Cd38-cyclic ADP-ribose (cADPR) signaling. We found that the mRNA levels of cluster of differentiation 38 (Cd38), type 2 ryanodine receptor (Ryr2), and FK506-binding protein 12.6 (Fkbp12.6) in H9c2 and P19.CL6 cardiomyocytes were significantly decreased by IH, whereas the promoter activities of these genes were not decreased. By contrast, the expression of phosphatase and tensin homolog deleted from chromosome 10 (Pten) was upregulated in IH-treated cells. The small interfering RNA for Pten (siPten) and a non-specific control RNA were introduced into the H9c2 cells. The IH-induced downregulation of Cd38, Ryr2, and Fkbp12.6 was abolished by the introduction of the siPten, but not by the control RNA. These results indicate that IH stress upregulated the Pten in cardiomyocytes, resulting in the decreased mRNA levels of Cd38, Ryr2, and Fkbp12.6, leading to the inhibition of cardiomyocyte functions in SAS patients.

Anorexigenic Effects of Intermittent Hypoxia on the Gut-Brain Axis in Sleep Apnea Syndrome

Sleep apnea syndrome (SAS) is a breathing disorder characterized by recurrent episodes of upper-airway collapse, resulting in intermittent hypoxia (IH) during sleep. Experimental studies with animals and cellular models have indicated that IH leads to attenuation of glucose-induced insulin secretion from pancreatic β cells and to enhancement of insulin resistance in peripheral tissues and cells, such as the liver (hepatocytes), adipose tissue (adipocytes), and skeletal muscles (myocytes), both of which could lead to obesity. Although obesity is widely recognized as a major factor in SAS, it is controversial whether the development of SAS could contribute directly to obesity, and the effect of IH on the expression of appetite regulatory genes remains elusive. Appetite is regulated appropriately by both the hypothalamus and the gut as a gut-brain axis driven by differential neural and hormonal signals. In this review, we summarized the recent epidemiological findings on the relationship between SAS and feeding behavior and focused on the anorexigenic effects of IH on the gut-brain axis by the IH-induced up-regulation of proopiomelanocortin and cocaine- and amphetamine-regulated transcript in neuronal cells and the IH-induced up-regulation of peptide YY, glucagon-like peptide-1 and neurotensin in enteroendocrine cells and their molecular mechanisms.

Maladaptive Pulmonary Vascular Responses to Chronic Sustained and Chronic Intermittent Hypoxia in Rat

Chronic sustained hypoxia (CSH), as found in individuals living at a high altitude or in patients suffering respiratory disorders, initiates physiological adaptations such as carotid body stimulation to maintain oxygen levels, but has deleterious effects such as pulmonary hypertension (PH). Obstructive sleep apnea (OSA), a respiratory disorder of increasing prevalence, is characterized by a situation of chronic intermittent hypoxia (CIH). OSA is associated with the development of systemic hypertension and cardiovascular pathologies, due to carotid body and sympathetic overactivation. There is growing evidence that CIH can also compromise the pulmonary circulation, causing pulmonary hypertension in OSA patients and animal models. The aim of this work was to compare hemodynamics, vascular contractility, and L-arginine-NO metabolism in two models of PH in rats, associated with CSH and CIH exposure. We demonstrate that whereas CSH and CIH cause several common effects such as an increased hematocrit, weight loss, and an increase in pulmonary artery pressure (PAP), compared to CIH, CSH seems to have more of an effect on the pulmonary circulation, whereas the effects of CIH are apparently more targeted on the systemic circulation. The results suggest that the endothelial dysfunction evident in pulmonary arteries with both hypoxia protocols are not due to an increase in methylated arginines in these arteries, although an increase in plasma SDMA could contribute to the apparent loss of basal NO-dependent vasodilation and, therefore, the increase in PAP that results from CIH.

A Prospective Study of CPAP Therapy in Relation to Cardiovascular Outcome in a Cohort of Romanian Obstructive Sleep Apnea Patients

Background: Despite efforts at treatment, obstructive sleep apnea (OSA) remains a major health problem, especially with increasing evidence showing an association with cardiovascular morbidity and mortality. The treatment of choice for OSA patients is Continuous Positive Airway Pressure (CPAP), which has been proven in randomized controlled trials to be an effective therapy for this condition. The impact of CPAP on the cardiovascular pathology associated with OSA remains, however, unclear. Although the effect of CPAP has been previously studied in relation to cardiovascular outcome, follow-up of the treatment impact on cardiovascular risk factors at one year of therapy is lacking in a Romanian population. Thus, we aimed to evaluate the one-year effect of CPAP therapy on lipid profile, inflammatory state, blood pressure and cardiac function, assessed by echocardiography, on a cohort of Romanian OSA patients. Methods: We enrolled 163 participants and recorded their baseline demographic and clinical characteristics with a follow-up after 12 months. Inflammatory and cardiovascular risk factors were assessed at baseline and follow up. Results: Our results show that CPAP therapy leads to attenuation of cardiovascular risk factors including echocardiographic parameters, while having no effect on inflammatory markers. Conclusion: Treatment of OSA with CPAP proved to have beneficial effects on some of the cardiovascular risk factors while others remained unchanged, raising new questions for research into the treatment and management of OSA patients.

Association between comorbid sleep apnoea-hypopnoea syndrome and prognosis of intensive care patients: a retrospective cohort study

OBJECTIVE

In this study, we investigated the association between comorbid sleep apnoea-hypopnoea syndrome (SAHS) and the prognosis of patients in an intensive care unit (ICU) to determine whether this relationship varies between different disease subgroups.

METHODS

We conducted a retrospective cohort study using publicly available information from the critical care database Medical Information Mart for Intensive Care III. Adults (≥18 years of age) who attended the ICU for the first time were enrolled. Demographic information and clinical data were obtained from each patient. The primary outcome was 30-day mortality after ICU admission, and the secondary outcomes were in-hospital and ICU mortality. Multivariate logistic regression and Cox regression analyses were used to examine the associations between SAHS comorbidities and the research outcomes. Propensity score matching was used to adjust for potential confounding variables.

RESULTS

Of the 32 989 patients enrolled, 1918 (5.81%) were diagnosed with SAHS as a comorbid condition. Patients with SAHS had a significantly lower 30-day mortality rate compared with those without SAHS (5.27% vs 13.65%, respectively; p<0.001). The frequency of chronic obstructive pulmonary disease, cerebral disease, cardiovascular disease, hypertension, diabetes mellitus and renal failure was significantly different between the two groups. Patients with SAHS demonstrated significantly longer survival compared with patients without SAHS. Multivariate Cox proportional hazards regression identified a significant relationship between SAHS and mortality within 30 days (adjusted HR=0.610, 95% CI 0.499 to 0.747, p<0.0001).

CONCLUSION

SAHS as a comorbid condition decreases the risk of 30-day mortality, in-hospital mortality and ICU mortality among ICU patients.

Validation of a new wearable device for type 3 sleep test without flowmeter

BACKGROUND

Ventilation monitoring during sleep is performed by sleep test instrumentation that is uncomfortable for the patients due to the presence of the flowmeter. The objective of this study was to evaluate if an innovative type 3 wearable system, the X10X and X10Y, is able to correctly detect events of apnea and hypopnea and to classify the severity of sleep apnea without the use of a flowmeter.

METHODS

40 patients with sleep disordered breathing were analyzed by continuous and simultaneous recording of X10X and X10Y and another certified type 3 system, SOMNOtouch, used for comparison. Evaluation was performed in terms of quality of respiratory signals (scores from 1, lowest, to 5, highest), duration and classification of apneas, as well as identification and duration of hypopneas.

RESULTS

580 periods were evaluated. Mean quality assigned score was 3.37±1.42 and 3.25±1.35 for X10X and X10Y and SOMNOtouch, respectively. The agreement between the two systems was evaluated with grades 4 and 5 in 383 out of 580 cases. A high correlation (r2 = 0.921; p<0.001) was found between the AHI indexes obtained from the two systems. X10X and X10Y devices were able to correctly classify 72.3% of the obstructive apneas, 81% of the central apneas, 61.3% of the hypopneas, and 64.6% of the mixed apneas when compared to SOMNOtouch device.

CONCLUSION

The X10X and X10Y devices are able to provide a correct grading of sleep respiratory disorders without the need of a nasal cannula for respiratory flow measurement and can be considered as a type 3 sleep test device for screening tests.

Prevalence of heart failure and left ventricular dysfunction in China: the China Hypertension Survey, 2012-2015

BACKGROUND

Heart failure (HF) is a major health burden worldwide. However, there is no nationwide epidemiological data on HF in China after 2000. The aims of this study are (i) to determine the prevalence of left ventricular (LV) dysfunction and HF (with reduced, mid-range, and preserved ejection fraction) in a nationally representative Chinese population, and (ii) to investigate the treatment and control of hypertension in HF patients.

METHODS AND RESULTS

Data from the China Hypertension Survey (CHS) and 22 158 participants were eligible for analysis in this study. For each participant, a self-reported history of HF and any other cardiovascular diseases was acquired. Two-dimensional and Doppler echocardiography was used to assess LV dysfunction. Overall, 1.3% (estimated 13.7 million) of the Chinese adult population aged ≥35 years had HF, 1.4% of participants had LV systolic dysfunction (ejection fraction <50%), and 2.7% were graded as having 'moderate' or 'severe' LV diastolic dysfunction. The weighted prevalence of HF was similar between urban and rural residents (1.6% vs. 1.1%, P = 0.266), and between men and women (1.4% vs. 1.2%, P = 0.632). In addition, among HF patients with hypertension, 57.7% received antihypertensive medication, and 14.5% had their blood pressure controlled <140/90 mmHg.

CONCLUSIONS

In summary, there was an increase in the prevalence of HF, and LV dysfunction was very common in China. However, treatment and control of hypertension in participants with HF were low.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR-ECS-14004641.

The impact of continuous positive airway pressure on cardiac arrhythmias in patients with sleep apnea

Background

Obstructive sleep apnea (OSA) can lead to cardiac complications: brady and tachyarrhythmias and sudden cardiac death. Continuous positive airway pressure (CPAP) is the gold standard for the treatment of OSA. The present study aims to demonstrate the efficiency of CPAP in the treatment of cardiac arrhythmias in patients with OSA. The study also recorded the frequency of arrhythmias in patients with untreated OSA and assessed the association between the severity of OSA and the occurrence of arrhythmias.

Materials and Methods

This is a prospective cohort study. Ninety-three patients with OSA were included, aged 60 (58-64) years, with female/male sex ratio of 1:4. They were subjected simultaneously to home respiratory polygraphy examination and Holter electrocardiogram monitoring, in two different stages: at diagnosis and at the 3-month checkup after CPAP treatment. The presence of supraventricular and ventricular arrythmias was noted. Respiratory parameter values were also recorded.

Results

Statistically significant decrease in the occurrence of supraventricular (P < 0.001) and ventricular extrasystoles (P < 0.001), atrial fibrillation (AF) (P = 0.03), nonsustained ventricular tachycardia (NSVT) (P = 0.03), and sinus pauses (P < 0.001) was observed 3 months after treatment with CPAP, compared with baseline. The apnea-hypopnea index (AHI) was correlated with the ventricular extrasystoles (r = 0.273; P = 0.008). The ejection fraction of the left ventricle was inversely correlated with the episodes of NSVT (r = -0.425; P < 0.001). AF was associated with the longest apnea (r = 0.215; P = 0.04). Cardiac activity pauses were correlated with AHI (r = 0.320; P = 0.002), longest apnea (r = 0.345; P = 0.01), and oxygen desaturation index (r = 0.325; P = 0.04).

Conclusion

The prevalence of cardiac arrhythmias in patients with OSA was reduced after 3 months of CPAP therapy. Cardiac arrhythmias were correlated with the severity of OSA.

Reciprocal actions of constrictor prostanoids and superoxide in chronic hypoxia-induced pulmonary hypertension: roles of EETs

Epoxyeicosatrienoic acids (EETs) are synthesized from arachidonic acid by CYP/epoxygenase and metabolized by soluble epoxide hydrolase (sEH). Roles of EETs in hypoxia-induced pulmonary hypertension (HPH) remain elusive. The present study aimed to investigate the underlying mechanisms, by which EETs potentiate HPH. Experiments were conducted on sEH knockout (sEH-KO) and wild type (WT) mice after exposure to hypoxia (10% oxygen) for three weeks. In normal/normoxic conditions, WT and sEH-KO mice exhibited comparable pulmonary artery acceleration time (PAAT), ejection time (ET), PAAT/ET ratio, and velocity time integral (VTI), along with similar right ventricular systolic pressure (RVSP). Chronic hypoxia significantly reduced PAAT, ET, and VTI, coincided with an increase in RVSP; these impairments were more severe in sEH-KO than WT mice. Hypoxia elicited downregulation of sEH and upregulation of CYP2C9 accompanied with elevation of CYP-sourced superoxide, leading to enhanced pulmonary EETs in hypoxic mice with significantly higher levels in sEH-KO mice. Isometric tension of isolated pulmonary arteries was recorded. In addition to downregulation of eNOS-induced impairment of vasorelaxation to ACh, HPH mice displayed upregulation of thromboxane A₂ (TXA₂) receptor, paralleled with enhanced pulmonary vasocontraction to a TXA₂ analog (U46619) in an sEH-KO predominant manner. Inhibition of COX-1 or COX-2 significantly prevented the enhancement by ∼50% in both groups of vessels, and the remaining incremental components were eliminated by scavenging of superoxide with Tiron. In conclusion, hypoxia-driven increases in EETs, intensified COXs/TXA₂ signaling, great superoxide sourced from activated CYP2C9, and impaired NO bioavailability work in concert, to potentiate HPH development.

Central and Obstructive Apneas in Heart Failure With Reduced, Mid-Range and Preserved Ejection Fraction

Background: Although central apneas (CA) and obstructive apneas (OA) are highly prevalent in heart failure (HF), a comparison of apnea prevalence, predictors and clinical correlates in the whole HF spectrum, including HF with reduced ejection fraction (HFrEF), mid-range EF (HFmrEF) and preserved EF (HFpEF) has never been carried out so far.

Materials and methods: 700 HF patients were prospectively enrolled and then divided according to left ventricular EF (408 HFrEF, 117 HFmrEF, 175 HFpEF). All patients underwent a thorough evaluation including: 2D echocardiography; 24-h Holter-ECG monitoring; cardiopulmonary exercise testing; neuro-hormonal assessment and 24-h cardiorespiratory monitoring.

Results: In the whole population, prevalence of normal breathing (NB), CA and OA at daytime was 40, 51, and 9%, respectively, while at nighttime 15, 55, and 30%, respectively. When stratified according to left ventricular EF, CA prevalence decreased (daytime: 57 vs. 43 vs. 42%, p = 0.001; nighttime: 66 vs. 48 vs. 34%, p < 0.0001) from HFrEF to HFmrEF and HFpEF, while OA prevalence increased (daytime: 5 vs. 8 vs. 18%, p < 0.0001; nighttime 20 vs. 29 vs. 53%, p < 0.0001).

In HFrEF, male gender and body mass index (BMI) were independent predictors of both CA and OA at nighttime, while age, New York Heart Association functional class and diastolic dysfunction of daytime CA. In HFmrEF and HFpEF male gender and systolic pulmonary artery pressure were independent predictors of CA at daytime, while hypertension predicted nighttime OA in HFpEF patients; no predictor of nighttime CA was identified. When compared to patients with NB, those with CA had higher neuro-hormonal activation in all HF subgroups. Moreover, in the HFrEF subgroup, patients with CA were older, more comorbid and with greater hemodynamic impairment while, in the HFmrEF and HFpEF subgroups, they had higher left atrial volumes and more severe diastolic dysfunction, respectively. When compared to patients with NB, those with OA were older and more comorbid independently from background EF.

Conclusions: Across the whole spectrum of HF, CA prevalence increases and OA decreases as left ventricular systolic dysfunction progresses. Different predictors and specific clinical characteristics might help to identify patients at risk of developing CA or OA in different HF phenotypes.

Relationship of Atrial Fibrillation to Outcomes in Patients Hospitalized for Chronic Obstructive Pulmonary Disease Exacerbation

INTRODUCTION

Chronic Obstructive Pulmonary Disease (COPD) is a major cause of hospitalization and is associated with an increased incidence of atrial fibrillation (AF). The impact of AF on in-hospital outcomes, including mortality, in patients hospitalized for COPD exacerbation is not well elucidated.

METHODS

We used the National Inpatient Sample database to examine discharges with the primary diagnosis of COPD exacerbation and compared mortality, length of stay and costs in patients with AF compared to those without AF. The study adjusted the outcomes for known cardiovascular risk factors and confounders using logistic regression and propensity score matching analysis.

RESULTS

Among 1,377,795 discharges with COPD exacerbation, 16.6% had AF. Patients with AF were older and had more comorbidities. Mortality was higher (2.4%) in the AF group than in the no AF group (1%), p <0.001. After adjustment to age, sex and confounders, AF remained an independent predictor for mortality, OR:1.44 (95% CI 133 - 1.56, p <0.001), prolonged length of stay, OR:1.63 (95% CI 1.57 - 1.69, p <0.001) and increased cost, OR: 1.45 (95% CI: 1.40 - 1.49, p <0.001).

CONCLUSIONS

among patients with COPD exacerbation, AF was associated with increased mortality and higher resource utilization.

The epidemiology of obstructive sleep apnoea and cardiovascular disease

Obstructive sleep apnoea, the most common form of sleep-disordered breathing, is highly prevalent in patients with cardiovascular disease. The last 30 years has seen a plethora of large scale epidemiological studies investigating the relationship between sleep apnoea and cardiovascular outcomes. This review highlights the key epidemiological studies addressing the links between sleep apnoea and hypertension, cardiac arrhythmias, cerebrovascular disease, coronary artery disease, heart failure and pulmonary hypertension, with a particular focus on some of the most recent reports.

Cardiovascular outcomes of continuous positive airway pressure therapy for obstructive sleep apnea

Obstructive sleep apnea is a common disorder with increased risk for cardiovascular morbidity and mortality. The first choice of treatment of obstructive sleep apnea is continuous positive airway pressure, which reduces excessive daytime sleepiness and improves quality of life in sleep clinic cohorts. Nevertheless, the majority of patients with cardiovascular disease and concomitant obstructive sleep apnea do not report daytime sleepiness, and adherence to treatment is insufficient particularly in this group. The current article aims to give an updated overview of the impact of continuous positive airway pressure therapy on cardiovascular outcomes mainly based on the observational studies and the recent randomized controlled trials.

Nocturnal Hypoxemia, But Not Sleep Apnea, Is Associated With a Poor Prognosis in Patients With Pulmonary Arterial Hypertension

BACKGROUND

Sleep apnea (SA) can cause repeated nocturnal arterial oxygen desaturation and result in acute increase in pulmonary arterial pressure (PAP). The presence of SA is associated with a poor prognosis in patients with chronic left-sided heart failure, but little is known for patients with pulmonary arterial hypertension (PAH).

METHODS AND RESULTS

We enrolled 151 patients with PAH (44±16 years old, male/female=37/114). They were all in the Nice Classification group 1 (idiopathic PAH/associated PAH=52/48%, mean PAP of 46±16 mmHg). They underwent right-heart catheterization and a sleep study with simplified polysomnography. Averaged percutaneous oxygen saturation (SpO2) during sleep was measured and an apnea-hypopnea index >5 was defined as SA. SA was noted in 58 patients (obstructive SA/central SA: 29/29). Over an average follow-up of 1,170±763 days, 32 patients died. By Kaplan-Meier analysis, there was no significant difference in deaths of patients with and without SA (χ2=2.82, P=0.093). On the other hand, the mortality in patients with lower averaged SpO2 was significantly higher than in those with higher averaged SpO2 (χ2=14.7, P<0.001) and that was the only independent variable related to death in multivariate Cox proportional hazards analysis.

CONCLUSIONS

SA in patients with PAH was not associated with worse prognosis, unlike left ventricular heart failure, but nocturnal hypoxemia was related to poor prognosis.

Effects of continuous positive airway pressure in patients at high risk of obstructive sleep apnea during propofol sedation after spinal anesthesia

In patients with obstructive sleep apnea, short-term use of a continuous positive airway pressure mask improves oxygenation, decreases the apnea-hypopnea index, and reduces hemodynamic instability. In this study, we investigated the effects of use of a continuous positive airway pressure mask in patients at high risk of obstructive sleep apnea during propofol sedation after spinal anesthesia. Forty patients who underwent propofol sedation after spinal anesthesia for transurethral bladder or prostate resection with a STOP-Bang score of 3 or more were enrolled in this study. Patients were randomly divided into two groups: a simple oxygen mask group (n = 20) and a continuous positive airway pressure mask group (n = 20). After spinal anesthesia, propofol was injected at a target concentration of 1.3 mcg/ml via a target concentration control injector. ApneaLink™ was applied to all patients. Patients in the simple oxygen mask group were administered oxygen at a rate of 6 L/min through a simple facial mask. Patients in the CPAP mask group were connected to a pressurizer, and oxygen (6 L/min, 5-15 cm H₂O) was administered. Blood pressure, heart rate, respiratory rate, and oxygen saturation were recorded preoperatively, after spinal anesthesia, and every 5 min after the injection of propofol to observe hemodynamic changes. Apnea-hypopnea index was estimated using ApneaLink™. There were no significant differences in hemodynamic changes between the two groups. Apnea-hypopnea index was significantly reduced in the continuous positive airway pressure mask group compared to the simple facial mask group. Application of a continuous positive airway pressure mask in a patient at high risk of obstructive sleep apnea can lower the incidence of obstructive sleep apnea during sedation without a significant effect on hemodynamic stability.

Predictors of Sleep Apnea in the Canadian Population

Older age, obesity, hypertension, snoring, and excessive daytime sleepiness have been associated with sleep apnea. The objective of this study was to determine the prevalence (crude and adjusted), as well as the risk factors, of sleep apnea in the adult Canadian population. Data from the 2009 Sleep Apnea Rapid Response (SARR) questionnaire were used to identify the risk factors, and all sleep-related questions in the SARR questionnaire were used. The outcome variable of interest was health professional-diagnosed sleep apnea. Covariates of interest were demographic variables, population characteristics, respiratory and cardiovascular diseases, and enabling resources. The multiple logistic regression model adjusted for the clustering effect was used to analyze the data. Sleep apnea was diagnosed in 858,913 adults (3.4% of the population), and more men (65.4%) than women (34.6%) were diagnosed with sleep apnea. Multivariable logistic regression analysis indicated that age (45 and older), loud snoring, sudden awakening with gasping/choking (rare/sometimes and once or more a week), and nodding off/falling asleep in driving in the past 12 months were significantly associated with diagnosed sleep apnea. Predictive probability demonstrated that in overweight and obese persons, ≥15 minutes of daily exercise significantly decreased the risk of diagnosed sleep apnea. The conclusion of this study is that in the Canadian population, sleep apnea is associated with older age, loud snoring, and sleeping problems. The protective effect of exercise warrants further investigation.

Obstructive sleep apnea as an independent predictor of postoperative delirium and pain: protocol for an observational study of a surgical cohort

Introduction: Postoperative delirium and pain are common complications in adults, and are difficult both to prevent and treat. Obstructive sleep apnea (OSA) is prevalent in surgical patients, and has been suggested to be a risk factor for postoperative delirium and pain. OSA also might impact pain perception, and alter pain medication requirements. This protocol describes an observational study, with the primary aim of testing whether OSA is an independent predictor of postoperative complications, focusing on (i) postoperative incident delirium and (ii) acute postoperative pain severity. We secondarily hypothesize that compliance with prescribed treatment for OSA (typically continuous positive airway pressure or CPAP) might decrease the risk of delirium and the severity of pain. Methods and analysis: We will include data from patients who have been enrolled into three prospective studies: ENGAGES, PODCAST, and SATISFY-SOS. All participants underwent general anesthesia for a non-neurosurgical inpatient operation, and had a postoperative hospital stay of at least one day at Barnes Jewish Hospital in St. Louis, Missouri, from February 2013 to May 2018.  Patients included in this study have been assessed for postoperative delirium and pain severity as part of the parent studies. In the current study, determination of delirium diagnosis will be based on the Confusion Assessment Method, and the Visual Analogue Pain Scale will be used for pain severity. Data on OSA diagnosis, OSA risk and compliance with treatment will be obtained from the preoperative assessment record. Other variables that are candidate risk factors for delirium and pain will also be extracted from this record. We will use logistic regression to test whether OSA independently predicts postoperative delirium and linear regression to assess OSAs relationship to acute pain severity. We will conduct secondary analyses with subgroups to explore whether these relationships are modified by compliance with OSA treatment.

Epidemiology of Sleep-Disordered Breathing and Heart Failure: What Drives What

PURPOSE OF REVIEW

The bidirectional relationships that have been demonstrated between heart failure (HF) and central sleep apnea (CSA) demand further exploration with respect to the implications that each condition has for the other. This review discusses the body of literature that has accumulated on these relationships and how CSA and its potential treatment may affect outcomes in patients with CSA.

RECENT FINDINGS

Obstructive sleep apnea (OSA) can exacerbate hypertension, type 2 diabetes, obesity, and atherosclerosis, which are known predicates of HF. Conversely, patients with HF more frequently exhibit OSA partly due to respiratory control system instability. These same mechanisms are responsible for the frequent association of HF with CSA with or without a Hunter-Cheyne-Stokes breathing (HCSB) pattern. Just as is the case with OSA, patients with HF complicated by CSA exhibit more severe cardiac dysfunction leading to increased mortality; the increase in severity of HF can in turn worsen the degree of sleep disordered breathing (SDB). Thus, a bidirectional relationship exists between HF and both phenotypes of SDB; moreover, an individual patient may exhibit a combination of these phenotypes. Both types of SDB remain significantly underdiagnosed in patients with HF and hence undertreated. Appropriate screening for, and treatment of, OSA is clearly a significant factor in the comprehensive management of HF, while the relevance of CSA remains controversial. Given the unexpected results of the Treatment of Sleep-Disordered Breathing with Predominant Central Sleep Apnea by Adaptive Servo Ventilation in Patients with Heart Failure trial, it is now of paramount importance that additional analysis of these data be expeditiously reported. It is also critical that ongoing and proposed prospective studies of this issue proceed without delay.

Sleep Apnea: Types, Mechanisms, and Clinical Cardiovascular Consequences

Sleep apnea is highly prevalent in patients with cardiovascular disease. These disordered breathing events are associated with a profile of perturbations that include intermittent hypoxia, oxidative stress, sympathetic activation, and endothelial dysfunction, all of which are critical mediators of cardiovascular disease. Evidence supports a causal association of sleep apnea with the incidence and morbidity of hypertension, coronary heart disease, arrhythmia, heart failure, and stroke. Several discoveries in the pathogenesis, along with developments in the treatment of sleep apnea, have accumulated in recent years. In this review, we discuss the mechanisms of sleep apnea, the evidence that addresses the links between sleep apnea and cardiovascular disease, and research that has addressed the effect of sleep apnea treatment on cardiovascular disease and clinical endpoints. Finally, we review the recent development in sleep apnea treatment options, with special consideration of treating patients with heart disease. Future directions for selective areas are suggested.

Chronic intermittent hypoxia induces cardiac inflammation and dysfunction in a rat obstructive sleep apnea model

Chronic intermittent hypoxia is considered to play an important role in cardiovascular pathogenesis during the development of obstructive sleep apnea (OSA). We used a well-described OSA rat model induced with simultaneous intermittent hypoxia. Male Sprague Dawley rats were individually placed into plexiglass chambers with air pressure and components were electronically controlled. The rats were exposed to intermittent hypoxia 8 hours daily for 5 weeks. The changes of cardiac structure and function were examined by ultrasound. The cardiac pathology, apoptosis, and fibrosis were analyzed by H&E staining, TUNNEL assay, and picosirius staining, respectively. The expression of inflammation and fibrosis marker genes was analyzed by quantitative real-time PCR and Western blot. Chronic intermittent hypoxia/low pressure resulted in significant increase of left ventricular internal diameters (LVIDs), end-systolic volume (ESV), end-diastolic volume (EDV), and blood lactate level and marked reduction in ejection fraction and fractional shortening. Chronic intermittent hypoxia increased TUNNEL-positive myocytes, disrupted normal arrangement of cardiac fibers, and increased Sirius stained collagen fibers. The expression levels of hypoxia induced factor (HIF)-1α, NF-kB, IL-6, and matrix metallopeptidase 2 (MMP-2) were significantly increased in the heart of rats exposed to chronic intermittent hypoxia. In conclusion, the left ventricular function was adversely affected by chronic intermittent hypoxia, which is associated with increased expression of HIF-1α and NF-kB signaling molecules and development of cardiac inflammation, apoptosis and fibrosis.

Role of Oxidative Stress in the Neurocognitive Dysfunction of Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) is characterized by chronic nocturnal intermittent hypoxia and sleep fragmentations. Neurocognitive dysfunction, a significant and extraordinary complication of OSAS, influences patients' career, family, and social life and reduces quality of life to some extent. Previous researches revealed that repetitive hypoxia and reoxygenation caused mitochondria and endoplasmic reticulum dysfunction, overactivated NADPH oxidase, xanthine oxidase, and uncoupling nitric oxide synthase, induced an imbalance between prooxidants and antioxidants, and then got rise to a series of oxidative stress (OS) responses, such as protein oxidation, lipid peroxidation, and DNA oxidation along with inflammatory reaction. OS in brain could trigger neuron injury especially in the hippocampus and cerebral cortex regions. Those two regions are fairly susceptible to hypoxia and oxidative stress production which could consequently result in cognitive dysfunction. Apart from continuous positive airway pressure (CPAP), antioxidant may be a promising therapeutic method to improve partially reversible neurocognitive function. Understanding the role that OS played in the cognitive deficits is crucial for future research and therapeutic strategy development. In this paper, recent important literature concerning the relationship between oxidative stress and cognitive impairment in OSAS will be summarized and the results can provide a rewarding overview for future breakthrough in this field.

An update on cardiovascular effects of obstructive sleep apnoea syndrome

Obstructive sleep apnoea syndrome is an important health problem which may cause or worsen systemic diseases. Chronic intermittent hypoxia during repetitive airflow cessations may cause endothelial dysfunction. Sleep apnoea is also shown to be associated with hypercoagulability which may be due to decreased nitric oxide levels and impaired vasodilatation. Endothelial dysfunction, increased systemic inflammation, sympathetic nervous system activation, increased oxidative stress and dysglycaemia may all contribute to cardiovascular processes such as hypertension, arrhythmia, stroke, heart failure and coronary artery disease in patients with obstructive sleep apnoea. Treatment approaches in patients with obstructive sleep apnoea mainly focus on maintaining upper airway patency either with positive airway pressure devices or upper airway appliances. Strategies involving positive airway pressure therapy are associated with decreased morbidity and mortality. Obstructive sleep apnoea should be suspected as an underlying mechanism in patients with cardiovascular disease and warrants appropriate treatment.

Echocardiographic findings and plasma endothelin-1 levels in obese patients with and without obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) and obesity are increasingly prevalent worldwide. Both promote endothelial dysfunction contributing to systemic and pulmonary hypertension over time. Endothelin-1 (ET-1) plays a pivotal role in the development of pulmonary hypertension (PH). The aim of the present study was to assess the association between plasma ET-1 and echocardiographic findings in obese individuals with and without OSA, as well as in non-obese patients with OSA.

METHODS

Ninety-seven subjects (56 males) were enrolled in the study. All subjects underwent the following tests: venous endothelin-1 levels, pulmonary function testing, and arterial blood gas analysis. All patients except controls underwent transthoracic echocardiography and portable testing for sleep-disordered breathing.

RESULTS

Plasma ET-1 levels were significantly higher in obese patients, both with and without OSA (respectively, n = 30 (mean value, 268.06 ± 49.56 pg/ml) and n = 32 (mean value, 263.12 ± 65.26 pg/ml)), compared with non-obese patients with OSA or to healthy controls (respectively, n = 20 (mean value, 149.8 ± 23.09 pg/ml) and n = 15 (mean value, 152.3 ± 27.64 pg/ml); p < 0.0001). Pulmonary artery pressure (PAPs) in obese patients with OSA were significantly higher than in obese patients without OSA (p < 0.0001), while there was no statistical difference between PAPs of obese patients without OSA, compared with the group of non-obese OSA patients. Plasma ET-1 levels significantly correlated with systolic PAPs in obese patients both with and without OSA (respectively, n = 30, r = 0.385, p = 0.03567; n = 32, r = 0.3497, p = 0.0497).

CONCLUSIONS

Our study suggests that endothelin levels are more strongly associated with weight than the presence of sleep-disordered breathing, but pulmonary artery hypertension is associated with both weight and OSA.

Day-case adenotonsillectomy for sleep apnoea in children?

OBJECTIVES

Many clinicians are concerned about possible airway or respiratory complications following adenotonsillectomy for sleep related breathing disorder (SRBD), and routinely admit such patients for overnight monitoring. However, published guidelines suggest this is unnecessary in some cases. This study firstly aimed to establish current UK practice, and secondly to investigate whether children with mild/moderate SRBD experience respiratory problems during the first post-operative night.

METHODS

To establish current UK practice, we carried out a telephone survey asking if the procedure was carried out as a day-case, and admission criteria. For the second aim, a prospective study of children admitted following adenotonsillectomy for mild/moderate SRBD was carried out to investigate occurrence of respiratory complications on first post-operative night.

RESULTS

Forty-two UK ENT doctors responded to the telephone survey, 50% routinely admitted patients having adenotonsillectomy for SRBD. Discharge criteria included stable observations and eating and drinking (14 hospitals), no bleeding (1), stable oxygen saturations (1) and age above 5 years (1); four had no specific criteria. Of 51 children admitted following adenotonsillectomy for mild/moderate SRBD, 11 (21.6%) experienced oxygen desaturations overnight. Of these, nine were under 4 years old, and two older children had asthma. Irrespective of comorbidities, 9/27 (33.2%) children under 4 years old experienced desaturations. The only children aged more than 4 years that had desaturations were ones that had additional comorbidities.

CONCLUSION

Half of surveyed doctors admit all children following surgery for SRBD. The number of admissions could be reduced, because same-day discharge for otherwise-healthy children over 4 years old having adenotonsillectomy for mild/moderate SRBD appears to be safe.

Sleep, death, and the heart

Obstructive and central sleep apnea have been associated with increased risk of adverse cardiovascular events and mortality. Sympathetic dysregulation occurring as a result of the respiratory disturbance is thought to play a role in this increased risk. Sleep apnea increases the risk of arrhythmias, myocardial ischemia/infarction, stroke, and heart failure, all of which may increase mortality risk. A higher incidence of nocturnal arrhythmias, cardiac ischemia, and sudden death has been noted in subjects with sleep-disordered breathing (SDB). In this review, the association between SDB and each of these conditions is discussed, as well as the potential mechanisms underlying these risks and the effects of treatment of SDB. Particular emphasis is placed on the relationship between SDB and nocturnal atrial and ventricular arrhythmias, myocardial ischemia/infarction and sudden death.

Sleep and breathing in congestive heart failure

Heart failure (HF) is one of the most prevalent and costly diseases in the United States. Sleep apnea is now recognized as a common, yet underdiagnosed, comorbidity of HF. This article discusses the unique qualities that sleep apnea has when it occurs in HF and explains the underlying pathophysiology that illuminates why sleep apnea and HF frequently occur together. The authors provide an overview of the treatment options for sleep apnea in HF and discuss the relative efficacies of these treatments.