Obstructive Sleep Apnea Syndrome Affects Left Ventricular Diastolic Function

DHECA score: A decision-making score to identify the need for CPAP treatment beyond the apnea-hypopnea index

PURPOSE

Obstructive sleep apnea (OSA) is a highly prevalent condition. Continuous positive airway pressure (CPAP) is the preferred treatment for a significant number of patients, but there is no established consensus among various guidelines or recommendations regarding its indication. This study reports on the level of agreement among an international Spanish-speaking group of OSA experts to create a consensus score that will facilitate the simple identification of CPAP indications for patients with OSA.

METHODS

Thirty-three sleep medicine specialists from various countries analyzed the criteria for CPAP indication in patients with OSA. The discussion was conducted virtually and asynchronously using the Delphi method. Four rounds of questions were carried out to score different aspects relating the severity of OSA to associated disorders that showed correction or improvement with CPAP use. The rounds of consultation concluded when consensus was reached on the score required for CPAP indication. Subsequently, an analysis was performed comparing the application of the score to usual clinical practice in two reference university hospitals.

RESULTS

This consensus study has led to the development of a simple and practical score for determining CPAP indication in patients with OSA. The score was tested and compared against real-world clinical practice in two reference university hospitals.

CONCLUSIONS

We believe that the developed score facilitates the easy identification of patients who should receive CPAP and standardizes criteria for comparing therapeutic outcomes across different patient series with this condition.

Circadian Biology in Obstructive Sleep Apnea-Associated Cardiovascular Disease

A dysregulated circadian system is independently associated with both Obstructive Sleep Apnea (OSA) and cardiovascular disease (CVD). OSA and CVD coexistence is often seen in patients with prolonged untreated OSA. However, the role of circadian dysregulation in their relationship is unclear. Half of the human genes, associated biological pathways, and physiological functions exhibit circadian rhythms, including blood pressure and heart rate regulation. Mechanisms related to circadian dysregulation and heart function are potentially involved in the coexistence of OSA and CVD. In this article, we provide a comprehensive overview of circadian dysregulation in OSA and associated CVD. We also discuss feasible animal models and new avenues for future research to understand their relationship. Oxygen-sensing pathways, inflammation, dysregulation of cardiovascular processes, oxidative stress, metabolic regulation, hormone signaling, and epigenetics are potential clock-regulated mechanisms connecting OSA and CVD.

Further insights into influence factors of hypertension in older patients with obstructive sleep apnea syndrome: a model based on multiple centers

OBJECTIVE

To construct a novel model or a scoring system to predict hypertension comorbidity in older patients with obstructive sleep apnea syndrome (OSAS).

METHODS

A total of 1290 older patients with OSAS from six tertiary hospitals in China were enrolled. The sample was randomly divided into a modeling set (80%) and validation set (20%) using a bootstrap method. Binary logistic regression analysis was used to identify influencing factors. According to the regression coefficients, a vivid nomogram was drawn, and an intuitive score was determined. The model and score were evaluated for discrimination and calibration. The Z-test was utilized to compare the predictive ability between the model and scoring system.

RESULTS

In the multivariate analysis, age, body mass index (BMI), apnea-hypopnea index (AHI), total bilirubin (TB), high-density lipoprotein cholesterol (HDL-C), and fasting blood glucose (FBG) were significant predictors of hypertension. The area under the receiver operating characteristic curve of the model in the modeling and validation sets was 0.714 and 0.662, respectively. The scoring system had predictive ability equivalent to that of the model. Moreover, the calibration curve showed that the risk predicted by the model and the score was in good agreement with the actual hypertension risk.

CONCLUSIONS

This accessible and practical correlation model and diagram can reliably identify older patients with OSAS at high risk of developing hypertension and facilitate solutions on modifying this risk most effectively.

The effect of continuous positive airway pressure therapy on atrial fibrillation in patients with obstructive sleep apnea

Obstructive sleep apnea (OSA) stands as an autonomous risk factor for a broad spectrum of cardiovascular diseases, particularly atrial fibrillation (AF), which is closely associated with heightened morbidity and mortality rates. The intricate pathophysiological pathways linking OSA to AF encompass chronic intermittent hypoxia, disruptions in the autonomic nervous system, inflammatory responses, and alterations in ion channel function. Continuous positive airway pressure (CPAP) therapy emerges as the frontline treatment for moderate to severe OSA, effectively alleviating symptomatic manifestations and potentially mitigating cardiovascular risks. However, the influence of CPAP on AF among OSA patients remains a subject of debate. Some investigations underscore its beneficial effects, including the reversal of atrial remodeling, enhanced atrial conduction, decreased AF incidence, and improved outcomes post-AF ablation in CPAP-treated individuals. Conversely, other studies reveal neutral or insignificant impacts. This review delves into the repercussions of CPAP therapy on AF in OSA patients, exploring potential explanations for the discrepancies observed across existing research endeavors. By consolidating current evidence and pinpointing areas ripe for further inquiry, this review aspires to inform clinical decision-making regarding the management of OSA-related AF.

Improvements of right ventricular function after intervention with CPAP in patients with obstructive sleep apnoea

BACKGROUND

Obstructive sleep apnoea (OSA) is present in 40-80% of patients with cardiovascular morbidity and is associated with adverse effects on cardiovascular health. Continuous positive airway pressure (CPAP) maintains airway patency during sleep and is hypothesised to improve cardiac function. In the present study, we report on the impact of 12 weeks of CPAP and improvements in echocardiographic parameters of the right ventricle (RV).

METHODS

Nineteen newly diagnosed patients with OSA and a respiratory disturbance index (RDI) greater than 10 were enrolled. Echocardiography was performed before treatment and with a follow-up assessment after 12 weeks of CPAP. Echocardiographic and Doppler measurements were made following the American Society for Echocardiography guidelines. The primary outcome was isovolumetric acceleration (IVA). Secondary outcomes include tricuspid annular plane systolic excursion (TAPSE), fractional area change (FAC), RV % strain, TEI index and RV dimension (RVD1).

RESULTS

There was significant improvement in isovolumetric acceleration of 0.5ms2 (P = 0.0012 (95% CI -0.72, -0.20)) and significant improvement of 2.05 mm in TAPSE (p = 0.0379 (95% CI -3.98 - -0.13). There was no significant difference in FAC, RV % strain, TEI index or RVD1 with twelve weeks of CPAP therapy.

CONCLUSION

The present study highlights significant improvement in TAPSE and IVA with 12 weeks of CPAP treatment and no significant improvement in FAC, RVD1 and RV % strain. These data indicate favourable characteristics on both load dependent and load independent markers of RV function with CPAP.

Treatment of OSA and its Impact on Cardiovascular Disease, Part 2: JACC State-of-the-Art Review

Many studies have shown an association of obstructive sleep apnea (OSA) with incident cardiovascular diseases, particularly when comorbid with insomnia, excessive sleepiness, obesity hypoventilation syndrome, and chronic obstructive pulmonary disease. Randomized controlled trials (RCTs) have demonstrated that treatment of OSA with positive airway pressure devices (CPAP) improves systemic hypertension, particularly in those with resistant hypertension who are adherent to CPAP. However, large RCTs have not shown long-term benefits of CPAP on hard cardiovascular outcomes, but post hoc analyses of these RCTs have demonstrated improved hard outcomes in those who use CPAP adequately. In theory, low CPAP adherence and patient selection may have contributed to neutral results in intention-to-treat analyses. Only by further research into clinical, translational, and basic underlying mechanisms is major progress likely to continue. This review highlights the various treatment approaches for sleep disorders, particularly OSA comorbid with various other disorders, the potential reasons for null results of RCTs treating OSA with CPAP, and suggested approaches for future trials.

Pde5 Inhibition Reduced Blood Pressure and Alleviated Target Organ Damage in Chronic Intermittent Hypoxia

ABSTRACT

The role of phosphodiesterase 5 (Pde5) in obstructive sleep apnea-induced damage remains unclear. Our study aimed to investigate the role of Pde5 in the chronic intermittent hypoxia (CIH) model. C57BL/6J wild-type (WT) mice (n = 48) and Pde5 knockout (Pde5 -/- ) mice (n = 24) were randomly assigned to CIH group and room air group. After 6 weeks, some WT mice (n = 24) in CIH group were given sildenafil or saline gavage for another 4 weeks. Blood pressure was regularly measured during the experiment. Echocardiography was used to estimate cardiac function. We collected organs from each group of mice and measured their physical indicators. Histochemical staining was used to explore the size of cardiomyocyte and fibrosis area of various organs. Cyclic guanosine monophosphate and malondialdehyde concentrations in serum were measured by ELISA assay. Compared with the RA-treated group, the 6-week CIH resulted in a significant increase in blood pressure, altered heart structure, and reduced serum cyclic guanosine monophosphate in WT mice. Pde5 -/- mice and sildenafil intragastric administration significantly reduced systolic blood pressure in CIH condition and attenuated the damage of target organs. In CIH model, we found that the cardiomyocyte size and fibrosis area of heart and kidney significantly reduced in Pde5 -/- groups. Besides, endogenous and exogenous inhibition of Pde5 reduced malondialdehyde level and inflammatory and oxidative stress markers expression in CIH condition. In this study, we found that Pde5 inhibition could reduce blood pressure and alleviate target organ damage in the CIH model, which may be mediated through the oxidative stress pathway.

Impact of Obstructive Sleep Apnea and Sympathetic Nervous System on Cardiac Health: A Comprehensive Review

A prevalent condition linked to an elevated risk of cardiovascular disease is sleep apnea. This review examines the connections between cardiac risk, the sympathetic nervous system, and sleep apnea. The increased risk of hypertension, arrhythmias, myocardial infarction, and heart failure was highlighted in the pathophysiology of sleep apnea and its effect on sympathetic activation. It is also important to consider potential processes such as oxidative stress, inflammation, endothelial dysfunction, and autonomic imbalance that may relate sleep apnea-induced sympathetic activation to cardiac risk. With implications for creating innovative diagnostic and treatment approaches to lessen the cardiovascular effects of sleep apnea, the goal of this investigation is to improve the understanding of the intricate link between sympathetic activity, cardiac risk, and sleep apnea. This study aimed to clarify the complex relationship between cardiovascular health and sleep apnea by synthesizing the available research and highlighting the crucial role played by the sympathetic nervous system in moderating this relationship. Our thorough investigation may have important therapeutic ramifications that will direct the creation of focused therapies to enhance cardiovascular outcomes in sleep apnea sufferers.

The Effects of Obstructive Sleep Apnea on the Cardiovascular System: A Comprehensive Review

Obstructive sleep apnea (OSA) is an increasingly relevant cause of cardiovascular morbidity worldwide. Although the association between OSA and the cardiovascular system is well-known, the extent of its effects is still a topic of interest, including pathophysiologic mechanisms, cardiovascular sequelae, and OSA therapies and their effects. Commonly described mechanisms of cardiovascular etiologies revolve around sympathetic activation, inflammation, and intermittent hypoxia resulting from OSA. Ultimately, these effects lead to manifestations in the cardiovascular system, such as arrhythmias, hypertension, and heart failure, among others. The resulting sequelae of OSA may also have differential effects based on gender and age; several studies suggest female gender to have more susceptibility to cardiovascular mortality, as well as an increase in age. Furthermore, several therapies for OSA, both established and emerging, show a reduction in cardiovascular morbidity and may even reduce cardiovascular burden. Namely, the establishment of CPAP has led to improvement in hypertension and cardiac function in patients with heart failure and even reduced the progression of early stages of atherosclerosis. Effective management of OSA decreases abnormal neural sympathetic activity, which results in better rhythm control and blood pressure control, both in waking and sleep cycles. With newer therapies for OSA, its effects on the cardiovascular system may be significantly reduced or even reversed after long-term management. The vast extent of OSA on the cardiovascular system, as well as current and future therapeutic strategies, will be described in detail in this review.

Sleep Apnea and Heart Failure-Current State-of-The-Art

Sleep-disordered breathing (SDB), including obstructive and central sleep apnea, significantly exacerbates heart failure (HF) through adverse cardiovascular mechanisms. This review aims to synthesize existing literature to clarify the relationship between SDB and HF, focusing on the pathophysiological mechanisms, diagnostic challenges, and the effectiveness of treatment modalities like continuous positive airway pressure (CPAP) and adaptive servo-ventilation ASV. We analyzed peer-reviewed articles from 2003 to 2024 sourced from PubMed, EMBASE, Scopus, and Web of Science databases. The prevalence of SDB in HF patients is high, often underdiagnosed, and underappreciated. Management strategies, including CPAP and ASV, have been shown to mitigate symptoms and improve cardiac function. However, despite the availability of effective treatments, significant challenges in screening and diagnosis persist, affecting patient management and outcomes. DB significantly impacts HF prognosis. Enhanced screening strategies and broader utilization of therapeutic interventions like CPAP and ASV are essential to improve the management and outcomes of HF patients with concomitant SDB. Future research should focus on refining diagnostic and treatment protocols to optimize care for HF patients with SDB.

Relationship between obstructive sleep apnea and pulmonary hypertension: past, present and future

INTRODUCTION

Obstructive sleep apnea (OSA) is a widely prevalent condition with consequent multiple organ systems complications. There is consensus that OSA is associated with negative effects on pulmonary hemodynamics but whether it contributes to development of clinical pulmonary hypertension (PH) is unclear.

AREAS COVERED

In this review, we (1) highlight previous studies looking into the possible bidirectional association of OSA and PH, focusing on those that explore clinical prognostic implications, (2) explore potential pathophysiology, (3) discuss the new metrics in OSA, (4) describe endo-phenotyping of OSA, (5) recommend possible risk assessment and screening pathways.

EXPERT OPINION

Relying only on symptoms to consider a sleep study in PH patients is a missed opportunity to detect OSA, which, if present and not treated, can worsen outcomes. The potential prognostic role of sleep study metrics such as oxygen desaturation index (ODI), hypoxic burden (HB) and ventilatory burden (VB) in OSA should be studied in prospective trials to identify patients at risk for PH. AHI alone has not provided clarity. In those with PH, we should consider replacing ambulatory overnight pulse oximetry (OPO) with home sleep studies (HST). In PH patients, mild OSA should be sufficient to consider PAP therapy.

Effect of continuous positive pressure ventilation on left ventricular diastolic function E/A ratio in patients with obstructive sleep apnea: a meta-analysis

PURPOSE

Many studies have shown that obstructive sleep apnea (OSA) is related to reduced left ventricular diastolic function. Continuous positive airway pressure (CPAP) is generally recognized as the preferred therapy for OSA. Yet, the effect of CPAP on left ventricular diastolic function in patients with OSA is inconclusive. In order to assess the influence of CPAP on left ventricular diastolic function in patients with OSA, we performed this meta-analysis of clinical experiments.

METHODS

PubMed, Web of Science, OVID, Embase, and Cochrane Library from the establishment of the database to July 6, 2022, were searched for clinical trial data. Inclusion criteria for this meta-analysis were: (1) Patients in the experimental group were diagnosed with OSA by polysomnography; (2) CPAP treatment course ≥ 4 weeks; (3) baseline and follow-up data of the diastolic function parameter E/A ratio were reported in the literature. Exclusion criteria were: (1) Central sleep apnea (CSA); (2) comorbid organic heart diseases such as coronary heart disease; (3) age < 18 years old; (4) conference abstracts or duplicate publications.

RESULTS

After exclusions, 7 studies (2 RCTs and 5 prospective studies) with 473 subjects (225 in the treatment group and 248 in the matched control group) were included in the meta-analysis. Subgroup analysis indicated that after CPAP therapy, the left ventricular (LV) E/A ratio was significantly increased in patients with OSA (weighted mean difference (WMD) = 0.22, 95% CI =  - 0.06-0.38; P = 0.007). Sensitivity analyses showed that the combined results were not influenced by single studies. Publication bias was not significant (Egger's test, P = 0.813).

CONCLUSIONS

The results of this meta-analysis suggest that CPAP may improve the E/A ratio in patients with OSA patients. However, the small number of studies (n = 7) decreases confidence in the findings. Thus, carefully designed randomized controlled trials are needed to confirm the findings.

Cross-Sectional Relationship Between Atrial Conduction Delay and Arterial Stiffness in Patients with Obstructive Sleep Apnea

AIM

Prolonged P-wave duration (PWD), which indicates atrial conduction delay, is a potent precursor of atrial fibrillation (AF) that may be induced by obstructive sleep apnea (OSA). The cardio-ankle vascular index (CAVI), which is an arterial stiffness parameter, is elevated in patients with OSA; moreover, an increased CAVI is associated with atrial conduction delay through left atrium enlargement in association with left ventricular diastolic dysfunction. We aimed to examine the relationship between the CAVI and PWD in patients with OSA.

METHODS

We included patients with a sinus rhythm who underwent overnight polysomnography. We measured the PWD and CAVI on standard 12-lead electrocardiograms; further, we analyzed the relationship between PWD and CAVI.

RESULTS

We analyzed data from 300 participants (men, 89.0%; mean age, 52.3 ± 13.1 years; and body mass index, 26.2 ± 3.9 kg/m2). The mean PWD was 104.4 ± 10.4 ms while the mean CAVI was 7.5 ± 1.5. PWD was significantly correlated with CAVI (r = 0.478, p < 0.001); additionally, PWD and CAVI were directly associated with OSA severity (p = 0.002 and p = 0.002, respectively). Multivariate regression analysis revealed an independent significant correlation of PWD and CAVI with OSA severity.

CONCLUSION

In patients with OSA, an increase in arterial stiffness is associated with atrial conduction delay.

Usefulness of sleep apnea monitoring by pacemaker sensor in elderly patients with diastolic dysfunction

BACKGROUND

Automated detection of sleep apnea (SA) by pacemaker (PM) has been proposed and exhibited good agreement with polysomnography to detect severe SA. We aimed to evaluate the usefulness of SA monitoring algorithm in elderly patients with diastolic dysfunction.

METHODS

Consecutive patients referred to the Caen University Hospital for PM implantation between May 2016 and December 2018 presenting isolated diastolic dysfunction were eligible for the study. The respiratory disturbance index (RDI) measured by the PM, and the mean monthly RDI (RDIm), were compared to the apnea hypopnea index (AHI) assessed with portable monitor for severe SA diagnosis.

RESULTS

During the study period, 68 patients were recruited, aged of 80.4 ± 8.2 years. 63 patients underwent polygraphy with a portable monitor: 57 presented SA (83.8%), including 16 with severe SA (23.5%). Eight were treated with continuous positive airway pressure (CPAP). We found the RDI cutoff value of 22 events/h to predict severe SA, with 71.4% sensitivity and 65.2%, specificity. The RDIm cutoff value to detect severe SA was 19 events/h, with a sensitivity of 60% and a specificity of 66%. There was a significant reduction in RDI (p = 0.041), RDIm (p = 0.039) and AHI (p = 0.002) after CPAP. Supraventricular arrhythmias were frequent in all patients, regardless of SA severity, considering either episodes occurrence or total burden.

CONCLUSION

In a population of elderly patients with PM and diastolic dysfunction, the SA monitoring algorithm was able to detect severe SA, with good diagnostic performance values, but also to provide follow-up data for the patients treated with CPAP.

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.

When blood pressure refuses to budge: exploring the complexity of resistant hypertension

Resistant hypertension, defined as blood pressure that remains above goal despite using three or more antihypertensive medications, including a diuretic, affects a significant proportion of the hypertensive population and is associated with increased cardiovascular morbidity and mortality. Despite the availability of a wide range of pharmacological therapies, achieving optimal blood pressure control in patients with resistant hypertension remains a significant challenge. However, recent advances in the field have identified several promising treatment options, including spironolactone, mineralocorticoid receptor antagonists, and renal denervation. In addition, personalized management approaches based on genetic and other biomarkers may offer new opportunities to tailor therapy and improve outcomes. This review aims to provide an overview of the current state of knowledge regarding managing resistant hypertension, including the epidemiology, pathophysiology, and clinical implications of the condition, as well as the latest developments in therapeutic strategies and future prospects.

Echocardiographic analysis of dogs before and after surgical treatment of brachycephalic obstructive airway syndrome

Brachycephalic dogs with brachycephalic obstructive airway syndrome (BOAS) are a valuable animal model for obstructive sleep apnea (OSA) in humans. Clinical signs of upper airway obstruction improve after surgical treatment of BOAS, but the impact of surgery on morphology and function of the heart has not been studied. Therefore, we aimed to compare the echocardiographic variables of dogs before and after surgical treatment of BOAS. We included 18 client-owned dogs with BOAS (7 French Bulldogs, 6 Boston Terriers, and 5 Pugs) scheduled for surgical correction. We performed a complete echocardiographic examination before and 6 to 12 (median 9) months after surgery. Seven non-brachycephalic dogs were included in the control group. After surgery, BOAS patients had a significantly (p < 0.05) larger left atrium to aortic ratio (LA/Ao), left atrium in the long axis index, and thickness of the left ventricular posterior wall in diastole index. They also had a higher late diastolic annular velocity of the interventricular septum (Am) and increased global right ventricular strain and left ventricular global strain in the apical 4-chamber view, as well as a higher caudal vena cava collapsibility index (CVCCI). Before surgery, BOAS patients had a significantly lower CVCCI, Am, peak systolic annular velocity of the interventricular septum (Si), and early diastolic annular velocity of the interventricular septum (Ei) compared to non-brachycephalic dogs. After surgery, BOAS patients had a smaller right ventricular internal diameter at base index, right ventricular area in systole index, mitral annular plane systolic excursion index, and tricuspid annular plane systolic excursion index, as well as lower values of Am, Si, Ei, and late diastolic annular velocity of the interventricular septum, and a larger LA/Ao compared to non-brachycephalic dogs. Significant differences between BOAS patients and non-brachycephalic dogs indicate higher right heart pressures and decreased systolic and diastolic ventricular function in BOAS dogs, which is in accordance with the results of studies in OSA patients. In parallel with the marked clinical improvement, right heart pressures decreased, and right ventricular systolic and diastolic function improved after surgery.

Effect of continuous positive airway pressure on atrial remodeling and diastolic dysfunction of patients with obstructive sleep apnea and metabolic syndrome: a randomized study

OBJECTIVE

The aim of this study was to evaluate the role of obstructive sleep apnea (OSA) treatment on heart remodeling and diastolic dysfunction in patients with metabolic syndrome (MS).

METHODS

This study is a prespecified analysis of a randomized placebo-controlled trial that enrolled patients with a recent diagnosis of MS and moderate-to-severe OSA to undergo continuous positive airway pressure (CPAP) or nasal dilators (placebo) for 6 months. Patients were invited to perform a transthoracic echocardiogram by a single investigator blinded to treatment assignment.

RESULTS

A total of 99 (79% men; mean [SD], age: 48 [9] years; BMI: 33 [4] kg/m² ) completed the study. At follow-up, in the placebo group, patients had a significant increase in atrial diameter: from 39.5 (37.0-43.0) mm to 40.5 (39.0-44.8) mm (p = 0.003). CPAP prevented atrial enlargement: from 40.0 (38.0-44.0) to 40.0 (39.0-45.0) mm (p = 0.194). In patients with diastolic dysfunction at baseline, almost half had diastolic dysfunction reversibility with CPAP (in comparison with only two patients in the placebo group, p = 0.039). In the regression analysis, the chance of diastolic dysfunction reversibility by CPAP was 6.8-fold (95% CI: 1.48-50.26, p = 0.025) compared with placebo.

CONCLUSIONS

In patients with MS and OSA, 6 months of CPAP therapy prevented atrial remodeling and increased the chance of diastolic dysfunction reversibility.

Effects of continuous positive airway pressure therapy on left ventricular performance in patients with severe obstructive sleep apnea

We investigated myocardial performance concerning obstructive sleep apnea (OSA) severity and the benefits of continuous positive airway pressure (CPAP) therapy. In this randomized sham-controlled trial, 52 patients (mean age, 49 years; 92%, males; mean AHI, 59) with severe OSA were randomly assigned to receive either CPAP or sham treatment for 3 months. The severity of OSA was determined using the apnea/hypopnea index (AHI), oxygen desaturation index (ODI), percentage of sleep time below 90% oxygen saturation (T90), and average O₂ saturation during sleep (mean SpO₂). We compared the changes in myocardial work after 3 months of CPAP (n = 26) versus the sham group (n = 26) at rest and during an exercise stress test. Unlike AHI or ODI, indices of hypoxemia including T90 and mean SpO₂ were significantly correlated with global constructive work, as defined by work of left ventricle (LV) that contributes to LV ejection during systole (T90, β = 0.393, p = 0.012; mean SpO₂, β = 0.331, p = 0.048), and global wasted work (GWW), as defined by work of LV that does not contribute to LV ejection (T90, β = 0.363, p = 0.015; mean SpO₂, β =  - 0.370, p = 0.019). After 3 months, GWW decreased (80.0 ± 49.2 to 60.8 ± 26.3, p = 0.009) and global work efficiency increased (94.0 ± 4.5 to 95.7 ± 2.0, p = 0.008) in the CPAP group compared to those in the sham group. At the 3-month follow-up exercise stress echocardiography, worsening of GWW during exercise was significantly decreased in the CPAP group compared to that in the sham group (p = 0.045 at 50 W). Hypoxemia indices were closely associated with myocardial performance in patients with severe OSA. CPAP treatment for 3 months improved left ventricular myocardial performance by decreasing wasted work and increasing work efficacy compared to the sham treatment.

Echocardiographic parameters in French Bulldogs, Pugs and Boston Terriers with brachycephalic obstructive airways syndrome

BACKGROUND

In this prospective study, we hypothesized that dogs with signs of brachycephalic obstructive airway syndrome (BOAS) would show differences in left and right heart echocardiographic parameters compared with brachycephalic dogs without signs of BOAS and non-brachycephalic dogs.

RESULTS

We included 57 brachycephalic (30 French Bulldogs 15 Pugs, and 12 Boston Terriers) and 10 non-brachycephalic control dogs. Brachycephalic dogs had significantly higher ratios of the left atrium to aorta and mitral early wave velocity to early diastolic septal annular velocity; smaller left ventricular (LV) diastolic internal diameter index; and lower tricuspid annular plane systolic excursion index, late diastolic annular velocity of the LV free wall, peak systolic septal annular velocity, late diastolic septal annular velocitiy, and right ventricular global strain than non-brachycephalic dogs. French Bulldogs with signs of BOAS had a smaller diameter of the left atrium index and right ventricular systolic area index; higher caudal vena cava at inspiration index; and lower caudal vena cava collapsibility index, late diastolic annular velocity of the LV free wall, and peak systolic annular velocity of the interventricular septum than non-brachycephalic dogs.

CONCLUSIONS

The differences in echocardiographic parameters between brachycephalic and non-brachycephalic dogs, brachycephalic dogs with signs of BOAS and non-brachycephalic dogs, and brachycephalic dogs with and without signs of BOAS indicate higher right heart diastolic pressures affecting right heart function in brachycephalic dogs and those with signs of BOAS. Most changes in cardiac morphology and function can be attributed to anatomic changes in brachycephalic dogs alone and not to the symptomatic stage.

Obstructive sleep apnea, myocardial perfusion and myocardial blood flow: A study of older male twins

BACKGROUND

Obstructive sleep apnea (OSA) has been associated with incidence of cardiovascular disease and with nocturnal angina, but evidence of a link with coronary atherosclerosis and myocardial ischemia is limited and previous studies may have been affected by selection bias or unmeasured confounding factors.

METHODS

We performed overnight polysomnography in 178 older male twins. The Apnea/Hypopnea Index (AHI) was calculated to assess OSA from the overnight sleep evaluation. AHI ≥15 was used as indicator of moderate/severe OSA. The following day, twins underwent myocardial perfusion imaging with [82Rb]-chloride positron emission tomography. Quantitative and semiquantitative measures of myocardial perfusion and absolute myocardial blood flow were obtained.

RESULTS

The mean age was 68 years and 40% of the sample had an AHI≥15, which indicates moderate to severe OSA. Abnormal myocardial perfusion, both with stress and at rest, was more common in twins with elevated AHI. After adjusting for clinical, lifestyle and behavioral factors, and previous history of cardiovascular disease, twins with AHI ≥15 had 3.6 higher odds (95% CI, 1.5-8.9) of an abnormal total severity score, defined as a score ≥100, and for each 5-point increment in AHI, the odds of abnormality increased by 20% (95% CI, 7%-34%). Twin pairs where both twins had OSA exhibited the greatest risk. There were no differences in measures of ischemia and absolute myocardial blood flow and flow reserve by AHI status.

CONCLUSIONS

OSA is associated with myocardial perfusion abnormalities that suggest prior subclinical myocardial scarring or infarction. Early environmental factors that affect both twins equally may play a role and should be further explored.

Screening for Obstructive Sleep Apnea in Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force

IMPORTANCE

Obstructive sleep apnea (OSA) is associated with adverse health outcomes.

OBJECTIVE

To review the evidence on screening for OSA in asymptomatic adults or those with unrecognized OSA symptoms to inform the US Preventive Services Task Force.

DATA SOURCES

PubMed/MEDLINE, Cochrane Library, Embase, and trial registries through August 23, 2021; surveillance through September 23, 2022.

STUDY SELECTION

English-language studies of screening test accuracy, randomized clinical trials (RCTs) of screening or treatment of OSA reporting health outcomes or harms, and systematic reviews of treatment reporting changes in blood pressure and apnea-hypopnea index (AHI) scores.

DATA EXTRACTION AND SYNTHESIS

Dual review of abstracts, full-text articles, and study quality. Meta-analysis of intervention trials.

MAIN OUTCOMES AND MEASURES

Test accuracy, excessive daytime sleepiness, sleep-related and general health-related quality of life (QOL), and harms.

RESULTS

Eighty-six studies were included (N = 11 051). No study directly compared screening with no screening. Screening accuracy of the Multivariable Apnea Prediction score followed by unattended home sleep testing for detecting severe OSA syndrome (AHI ≥30 and Epworth Sleepiness Scale [ESS] score &gt;10) measured as the area under the curve in 2 studies (n = 702) was 0.80 (95% CI, 0.78 to 0.82) and 0.83 (95% CI, 0.77 to 0.90). Five studies assessing the accuracy of other screening tools were heterogeneous and results were inconsistent. Compared with inactive control, positive airway pressure was associated with a significant improvement in ESS score from baseline (pooled mean difference, -2.33 [95% CI, -2.75 to -1.90]; 47 trials; n = 7024), sleep-related QOL (standardized mean difference, 0.30 [95% CI, 0.19 to 0.42]; 17 trials; n = 3083), and general health-related QOL measured by the 36-Item Short Form Health Survey (SF-36) mental health component summary score change (pooled mean difference, 2.20 [95% CI, 0.95 to 3.44]; 15 trials; n = 2345) and SF-36 physical health component summary score change (pooled mean difference, 1.53 [95% CI, 0.29 to 2.77]; 13 trials; n = 2031). Use of mandibular advancement devices was also associated with a significantly larger ESS score change compared with controls (pooled mean difference, -1.67 [95% CI, 2.09 to -1.25]; 10 trials; n = 1540). Reporting of other health outcomes was sparse; no included trial found significant benefit associated with treatment on mortality, cardiovascular events, or motor vehicle crashes. In 3 systematic reviews, positive airway pressure was significantly associated with reduced blood pressure; however, the difference was relatively small (2-3 mm Hg).

CONCLUSIONS AND RELEVANCE

The accuracy and clinical utility of OSA screening tools that could be used in primary care settings were uncertain. Positive airway pressure and mandibular advancement devices reduced ESS score. Trials of positive airway pressure found modest improvement in sleep-related and general health-related QOL but have not established whether treatment reduces mortality or improves most other health outcomes.

Changes in Left Heart Geometry, Function, and Blood Serum Biomarkers in Patients with Obstructive Sleep Apnea after Treatment with Continuous Positive Airway Pressure

Background: Cardiovascular remodeling is essential in patients with obstructive sleep apnea (OSA), and continuous positive airway pressure (CPAP) therapy could improve these processes. Two-dimensional (2D) speckle-tracking (ST) echocardiography is a useful method for subclinical biventricular dysfunction diagnosis and thus might help as an earlier treatment for OSA patients. It is still not clear which blood serum biomarkers could be used to assess CPAP treatment efficacy. Objectives: To evaluate left heart geometry, function, deformation parameters, and blood serum biomarker (galectin-3, sST2, endothelin-1) levels in patients with OSA, as well as to assess changes after short-term CPAP treatment. Materials and Methods: Thirty-four patients diagnosed with moderate or severe OSA, as well as thirteen patients as a control group, were included in the study. All the subjects were obese (body mass index (BMI) > 30 kg/m2). Transthoracic 2D ST echocardiography was performed before and after 3 months of treatment with CPAP; for the control group, at baseline only. Peripheral blood samples for the testing of biomarkers were collected at the time of study enrolment before the initiation of CPAP therapy and after 3 months of CPAP treatment (blood samples were taken just for OSA group patients). Results: The left ventricle (LV) end-diastolic diameter and volume, as well as LV ejection fraction (EF), did not differ between groups, but an increased LV end-systolic volume and a reduced LV global longitudinal strain (GLS) were found in the OSA group patients (p = 0.015 and p = 0.035, respectively). Indexed by height, higher LV MMi in OSA patients (p = 0.007) and a higher prevalence of LV diastolic dysfunction (p = 0.023) were found in this group of patients. Although left atrium (LA) volume did not differ between groups, OSA group patients had significantly lower LA reservoir strain (p < 0.001). Conventional RV longitudinal and global function parameters (S′, fractional area change (FAC)) did not differ between groups; however, RV GLS was reduced in OSA patients (p = 0.026). OSA patients had a significantly higher right atrium (RA) diameter and mean pulmonary artery pressure (PAP) (p < 0.05). Galectin-3 and sST2 concentrations significantly decreased after 3 months of CPAP treatment. Conclusions: OSA is associated with the left heart remodeling process—increased LV myocardial mass index, LV diastolic dysfunction, reduced LV and RV longitudinal strain, and reduced LA reservoir function. A short-term, 3-months CPAP treatment improves LV global longitudinal strain and LA reservoir function and positively affects blood serum biomarkers. This new indexing system for LV myocardial mass by height helps to identify myocardial structural changes in obese patients with OSA.

Obstructive Sleep Apnea and Cardiovascular Diseases: Sad Realities and Untold Truths regarding Care of Patients in 2022

Obstructive sleep apnea (OSA) is one of the most common and serious sleep-related breathing disorders with a high prevalence among patients with cardiovascular (CV) diseases. Despite its widespread presence, OSA remains severely undiagnosed and untreated. CV mortality and morbidity are significantly increased in the presence of OSA as it is associated with an increased risk of resistant hypertension, heart failure, arrhythmias, and coronary artery disease. Evaluation and treatment of OSA should focus on recognizing patients at risk of developing OSA. The use of screening questionnaires should be routine, but a formal polysomnography sleep study is fundamental in establishing and classifying OSA. Recognition of OSA patients will allow for the institution of appropriate therapy that should alleviate OSA-related symptoms with the intent of decreasing adverse CV risk. In this review, we focus on the impact OSA has on CV disease and evaluate contemporary OSA treatments. Our goal is to heighten awareness among CV practitioners.

Obstructive sleep apnoea and left ventricular diastolic dysfunction among first responders to the 9/11 World Trade Center terrorist attack: a cross-sectional study

OBJECTIVES

Obstructive sleep apnoea (OSA) is often linked to cardiovascular disease. A limited number of studies have reported an association between OSA and left ventricular diastolic dysfunction (LVDD). However, prior studies were performed on small patient populations. Studies have shown a high prevalence of OSA among first responders to the 9/11 World Trade Center (WTC) terrorist attack. We investigated the relationship between OSA and LVDD in a large population of WTC responders.

DESIGN

Cross-sectional study.

SETTING

One-time screening programme as part of the WTC-CHEST Study (NCT10466218), performed at a quaternary medical centre in New York City, from November 2011 to June 2014.

PARTICIPANTS

A total of 1007 participants with mean age of 51 years of mostly non-Hispanic white men were evaluated. Patients from the WTC Health Program-Clinical Center of Excellence, who were over the age of 39 years, were eligible to participate.

RESULTS

Evaluation of those without OSA diagnosis showed no significant association with LVDD when comparing those screened (Berlin Questionnaire) as OSA high risk versus OSA low risk (p=0.101). Among those diagnosed with LVDD, there was a significant association when comparing those with and without patient-reported OSA (OR 1.50, 95% CI 1.13 to 2.00, p=0.005), but the significance was not maintained after adjusting for pertinent variables (OR 1.3, 0.94 to 1.75, p=0.119). Notably, comparing those with OSA diagnosis and those low risk of OSA, the OR for LVDD was significant (1.69, 1.24 to 2.31, p=0.001), and after adjusting for waist-hip ratio, diabetes and coronary artery calcium score percentile, the relationship remained significant (OR 1.45, 1.03 to 2.04, p=0.032).

CONCLUSION

The strong association of OSA with LVDD in this population may inform future guidelines to recommend screening for LVDD in high-risk asymptomatic patients with OSA.

Effect of positive airway pressure on cardiac troponins in patients with sleep-disordered breathing: A meta-analysis

Background

Cardiac troponins are highly sensitive and specific biomarkers for cardiac injury. Previous studies evaluating the effect of positive airway pressure (PAP) on cardiac troponins in patients with sleep‐disordered breathing (SDB) have yielded conflicting results. The meta‐analysis was performed to examine the effect of PAP on cardiac troponins in SDB patients.

Methods

PubMed, Web of Science, and EMBASE before September 2021 on original English language studies were searched. The data on cardiac troponins in both baseline and post‐PAP treatment were extracted from all studies. The data on the change of cardiac troponins in both PAP and control group were extracted from randomized controlled trials. Standardized mean difference (SMD) was used to synthesize quantitative results.

Results

A total of 11 studies were included. PAP treatment was not associated with a significant change in cardiac troponin T between the baseline and post‐PAP treatment (SMD = −0.163, 95% confidence interval [CI] = −0.652 to 0.326, z = 0.65, p = .514). The pooled estimate of SMD of cardiac troponin I between the pre‐ and post‐PAP treatment was 0.287, and the 95% CI was −0.586 to 1.160 (z = 0.64, p = .519). The pooled SMD of change of cardiac troponin T between the PAP group and control group was −0.473 (95% CI = −1.198 to 0.252, z = 1.28, p = .201).

Conclusions

This meta‐analysis revealed that PAP treatment was not associated with any change of cardiac troponin in SDB patients.

Obstructive sleep apnea

Obstructive sleep apnea (OSA) is a disease that results from loss of upper airway muscle tone leading to upper airway collapse during sleep in anatomically susceptible persons, leading to recurrent periods of hypoventilation, hypoxia, and arousals from sleep. Significant clinical consequences of the disorder cover a wide spectrum and include daytime hypersomnolence, neurocognitive dysfunction, cardiovascular disease, metabolic dysfunction, respiratory failure, and pulmonary hypertension. With escalating rates of obesity a major risk factor for OSA, the public health burden from OSA and its sequalae are expected to increase, as well. In this chapter, we review the mechanisms responsible for the development of OSA and associated neurocognitive and cardiometabolic comorbidities. Emphasis is placed on the neural control of the striated muscles that control the pharyngeal passages, especially regulation of hypoglossal motoneuron activity throughout the sleep/wake cycle, the neurocognitive complications of OSA, and the therapeutic options available to treat OSA including recent pharmacotherapeutic developments.

Sleep Apnoea and Heart Failure

Heart Failure (HF) and Sleep-Disordered-Breathing (SDB) are two common conditions that frequently overlap and have been studied extensively in the past three decades. Obstructive Sleep Apnea (OSA) may result in myocardial damage, due to intermittent hypoxia increased sympathetic activity and transmural pressures, low-grade vascular inflammation and oxidative stress. On the other hand, central sleep apnoea and Cheyne-Stokes respiration (CSA-CSR) occurs in HF, irrespective of ejection fraction either reduced (HFrEF), preserved (HFpEF) or mildly reduced (HFmrEF). The pathophysiology of CSA-CSR relies on several mechanisms leading to hyperventilation, breathing cessation and periodic breathing. Pharyngeal collapse may result at least in part from fluid accumulation in the neck, owing to daytime fluid retention and overnight rostral fluid shift from the legs. Although both OSA and CSA-CSR occur in HF, the symptoms are less suggestive than in typical (non-HF related) OSA. Overnight monitoring is mandatory for a proper diagnosis, with accurate measurement and scoring of central and obstructive events, since the management will be different depending on whether the sleep apnea in HF is predominantly OSA or CSA-CSR. SDB in HF are associated with worse prognosis, including higher mortality than in patients with HF but without SDB. However, there is currently no evidence that treating SDB improves clinically important outcomes in patients with HF, such as cardiovascular morbidity and mortality.

Treatment of Sleep Apnea with Positive Airway Pressure and Its Association with Diastolic Dysfunction: A Systematic Review and Meta-Analysis

BACKGROUND

This meta-analysis assessed the effect of long-term (>6 weeks) noninvasive positive airway pressure (PAP) on diastolic function in patients with obstructive sleep apnea (OSA).

METHODS

We searched the databases for randomized clinical trials including Ovid MEDLINE, Ovid Embase Scopus, Web of Science, Google Scholar, and EBSCO CINAHL from inception up to December 20, 2019. The search was not restricted to time, publication status, or language. Two independent investigators screened the studies and extracted the data, in duplicate. Risk of bias was assessed using Cochrane collaboration tools.

RESULTS

A total of 2,753 abstracts were resulted from literature search. A total of 9 randomized clinical trials assessing the effect of long-term (>6 weeks) PAP on diastolic function in patients with OSA including 833 participants were included. The following echo parameters were found in treated patients: a decrease in deceleration time (-39.49 ms CI [-57.24, -21.74]; p = 0.000), isovolumic relaxation time (-9.32 ms CI [-17.08, -1.57]; p = 0.02), and the ratio of early mitral inflow velocity to mitral annular early diastolic velocity (-1.38 CI [-2.6, -0.16]; p = 0.03). However, changes in left-atrial volume index and the ratio of early to late mitral inflow velocities were not statistically different. The risk of bias was mild to moderate among the studies.

CONCLUSION

Our results suggest that chronic treatment of moderate to severe OSA with noninvasive PAP is associated with improvement in echocardiographic findings of diastolic dysfunction.

Obstructive sleep apnea increases the risk of cardiovascular damage: a systematic review and meta-analysis of imaging studies

BACKGROUND

We aimed to perform a systematic review and meta-analysis of the association between obstructive sleep apnea (OSA) and cardiac as well as coronary impairment evaluated using imaging modalities. Finding of this study will provide more robust evidence regarding OSA-induced cardiovascular damage.

METHODS

We systematically searched through PubMed, EMBASE, and Cochrane library databases for relevant literatures on the association between OSA and cardiovascular damage evaluated using imaging modalities, and manually searched the references of selected articles for additional relevant articles. For each clinical parameter relevant to the meta-analysis, we first evaluated the methodological heterogeneity of the relevant studies and thereafter pooled the data together using fixed effect or random effect model. The difference in the relevant indices of cardiovascular damage between OSA patients and controls was evaluated using the standardized mean difference.

RESULTS

Of the 82 articles included in the final systematic analysis, 20 studies explored the association between OSA and coronary atherosclerosis. OSA patients had higher rate of coronary atherosclerosis assessed by coronary artery calcification score and plaque volume. Moreover, the severity of OSA and coronary atherosclerosis displayed a positive correlation. The rest of the studies (n = 62) evaluated cardiac alterations in OSA patients. According to the inclusion and exclusion criteria, 46 studies yielding 3082 OSA patients and 1774 controls were pooled for the meta-analysis. For left cardiac structure and function, OSA patients exhibited significantly wider left atrial diameter; higher left atrium volume index; wider left ventricular end-systolic diameter, left ventricular end-diastolic diameter, and left ventricular mass; higher left ventricular mass index; wider interventricular septum diameter and posterior wall diameter; and higher left ventricular myocardial performance index (all p < 0.05). In addition, compared with controls, left ventricular ejection fraction was significantly decreased in OSA patients (p = 0.001). For right cardiac structure and function, OSA patients displayed a significant increase in right ventricular diameter and right ventricular myocardial performance index (both p < 0.001). Finally, compared with controls, OSA patients displayed significant decrease in tricuspid annular plane systolic excursion and RV fractional area change (p = 0.001).

CONCLUSION

Overall, this systematic review and meta-analysis provides imaging evidence in support that OSA patients are at a higher risk of developing coronary atherosclerosis and display cardiac remodeling and dysfunction.

Obstructive sleep apnoea syndrome and left ventricular hypertrophy: a meta-analysis of echocardiographic studies

AIM

We investigated the association between obstructive sleep apnoea (OSA) and subclinical cardiac organ damage through a meta-analysis of echocardiographic studies that provided data on left ventricular hypertrophy (LVH), assessed as a categorical or continuous variable.

DESIGN

The PubMed, OVID-MEDLINE, and Cochrane library databases were systematically analyzed to search English-language articles published from 1 January 2000 to 15 August 2019. Studies were detected by using the following terms: 'obstructive sleep apnea', 'sleep quality', 'sleep disordered breathing', 'cardiac damage', 'left ventricular mass', 'left ventricular hypertrophy', and 'echocardiography'.

RESULTS

Meta-analysis included 5550 patients with OSA and 2329 non-OSA controls from 39 studies. The prevalence of LVH in the pooled OSA population was 45% (CI 35--55%). Meta-analysis of studies comparing the prevalence of LVH in participants with OSA and controls showed that OSA was associated with an increased risk of LVH (OR = 1.70, CI 1.44-2.00, P < 0.001). LV mass was significantly increased in patients with severe OSA as compared with controls (SMD 0.46 ± 0.08, CI 0.29-0.62, P < 0.001) or with mild OSA. This was not the case for studies comparing patients with unselected or predominantly mild OSA and controls (0.33 ± 0.17, CI -0.01 to 0.67, P = 0.057).

CONCLUSION

The present meta-analysis expands previous information on the relationship between OSA and echocardiographic LVH, so far based on individual studies. The overall evidence strongly suggests that the likelihood of LVH increases with the severity of OSA, thus exhibiting a continuous relationship.

Continuous positive airway pressure improves blood pressure and serum cardiovascular biomarkers in obstructive sleep apnoea and hypertension

RATIONALE

The impact of treatment for obstructive sleep apnoea (OSA) on reduction of cardiovascular risk is unclear. This study aimed to examine the effect of continuous positive airway pressure (CPAP) on ambulatory blood pressure (BP) and subclinical myocardial injury in subjects with OSA and hypertension.

METHODS

Subjects with hypertension requiring at least three anti-hypertensive medications and moderate-severe OSA were enrolled. Eligible subjects were randomized (1:1) to receive either CPAP treatment or control (no CPAP) for eight weeks. Changes in ambulatory BP and serum biomarkers were compared. Stratified analysis according to circadian BP pattern was performed.

MAIN RESULTS

Ninety two subjects (75% men; age, 51±8 years; apnoea-hypopnoea index 40±8 events·h^-1, taking average of 3.4 anti-hypertensive drugs [range 3-6]) were randomised. The group on CPAP treatment, compared to the control group, demonstrated significant reduction in 24-h systolic BP (-4.4 mmHg, 95% CI -8.7 to -0.1, p=0.046), 24-h diastolic BP (-2.9 mmHg, 95% CI -5.5 to -0.2, p=0.032), daytime systolic BP (-5.4 mmHg, -9.7 to -1.0, p=0.016) and daytime diastolic BP (-3.4 mmHg, 95% CI -6.1 to -0.8, p=0.012). CPAP treatment was associated with significant BP lowering only in non-dippers, but not in dippers. Serum troponin I (mean difference -1.74 pg·mL^-1, 95% CI -2.97 to -0.5, p=0.006) and brain natriuretic peptide (-9.1 pg·mL^-1, 95% CI -17.6 to -0.6, p=0.036) were significantly reduced in CPAP compared to control group.

CONCLUSION

In a cohort with OSA and multiple cardiovascular risk factors including difficult-to-control hypertension, short-term CPAP treatment improved ambulatory BP and alleviated subclinical myocardial injury and strain.

Undiagnosed sleep apnoea in cardiac rehabilitation: Age-dependent effect on diastolic function in coronary artery disease patients with preserved ejection fraction

BACKGROUND

Focusing on detection of sleep apnoea early in the cardiac rehabilitation process may improve the recovery process and reduce recurrence of cardiovascular events. Patients who continue to be undiagnosed may experience a significantly worse outcome during their cardiac rehabilitation and recovery. Diastolic dysfunction has both diagnostic and prognostic importance in the management of coronary artery disease. We hypothesise that undiagnosed/untreated sleep apnoea in middle-aged coronary artery disease patients with preserved left ventricular ejection fraction changes the pattern of diastolic filling close to that in elderly patients without sleep apnoea.

METHODS AND RESULTS

This cross-sectional study included the 450 coronary artery disease patients with undiagnosed sleep apnoea who had left ventricular ejection fraction ⩾50% and were referred consecutively to the Clinic of Cardiovascular Rehabilitation within two weeks after treatment for acute coronary syndrome. Polysomnographic and echocardiographic measurements were analysed. Mild to severe sleep apnoea was defined as the apnoea-hypopnea index ⩾5. Age was dichotomised into under the age of 60 years and age 60 years or over. Up to 35% of coronary artery disease patients were likely to have undiagnosed sleep apnoea. There was a statistically significant interaction between the effect of sleep apnoea and age group on diastolic function defined as the ratio peak flow velocity in early diastole/peak flow velocity in atrial contraction ratio (p=0.036). This ratio was significantly (p=0.029) lower in the mild-severe sleep apnoea group (0.97, 95% confidence interval 0.88-1.06) than in the non-sleep apnoea group (1.09, 95% confidence interval 1.03-1.15) among middle aged (<60 years) coronary artery disease patients. Therefore, filling patterns in the middle aged (<60 years) patients with sleep apnoea resemble those observed in the elderly (⩾60 years) patients without sleep apnoea. The effect of sleep apnoea on left ventricular filling pattern in elderly was not observed.

CONCLUSIONS

Age modifies the effect of sleep apnoea on cardiovascular outcomes. The findings that undiagnosed sleep apnoea impairs diastolic function in a middle-aged coronary artery disease patient underscore the importance of early diagnosis and treatment of sleep apnoea. It is recommended to train and educate cardiac rehabilitation staff on the importance of sleep disorders in this population.

Effect of Obstructive Sleep Apnea and Positive Airway Pressure Therapy on Cardiac Remodeling as Assessed by Cardiac Biomarker and Magnetic Resonance Imaging in Nonobese and Obese Adults

It is unknown whether obesity modifies the effect of obstructive sleep apnea (OSA) and positive airway pressure (PAP) therapy on cardiac remodeling and NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels. We compared NT-proBNP and cardiac magnetic resonance imaging in adults without OSA (n=56) and nonobese (n=73; body mass index <30 kg/m²) and obese (n=136; body mass index ≥30 kg/m²) adults with OSA. We also investigated these traits in nonobese (n=45) and obese (n=78) participants with OSA adherent to 4 months of PAP treatment. At baseline, left ventricular mass to end-diastolic volume ratio, a measure of left ventricular concentricity, was greater in both nonobese and obese participants with OSA compared with those without OSA. Participants with OSA and obesity exhibited reduced phasic right atrial function. No significant differences in baseline NT-proBNP were observed across groups. The effect of PAP treatment on NT-proBNP and left atrial volume index was significantly modified by obesity. In nonobese participants, PAP therapy was associated with a decrease in NT-proBNP (P<0.0001) without a change in left atrial volume index, whereas in obese participants, PAP was associated with an increase in left atrial volume index (P=0.006) without a change in NT-proBNP. OSA was associated with left ventricular concentric remodeling independent of obesity and right atrial dysfunction in participants who were obese. PAP treatment was associated with reduced NT-proBNP in nonobese participants with OSA, but left atrial enlargement in obese participants with OSA, suggesting that PAP-induced reduction in BNP release (which is known to occur during obstructive apnea episodes) may lead to volume retention in obese participants with OSA. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01578031.

A novel mouse model of obstructive sleep apnea by bulking agent-induced tongue enlargement results in left ventricular contractile dysfunction

AIMS

Obstructive sleep apnea (OSA) is a widespread disease with high global socio-economic impact. However, detailed pathomechanisms are still unclear, partly because current animal models of OSA do not simulate spontaneous airway obstruction. We tested whether polytetrafluoroethylene (PTFE) injection into the tongue induces spontaneous obstructive apneas.

METHODS AND RESULTS

PTFE (100 μl) was injected into the tongue of 31 male C57BL/6 mice and 28 mice were used as control. Spontaneous apneas and inspiratory flow limitations were recorded by whole-body plethysmography and mRNA expression of the hypoxia marker KDM6A was quantified by qPCR. Left ventricular function was assessed by echocardiography and ventricular CaMKII expression was measured by Western blotting. After PTFE injection, mice showed features of OSA such as significantly increased tongue diameters that were associated with significantly and sustained increased frequencies of inspiratory flow limitations and apneas. Decreased KDM6A mRNA levels indicated chronic hypoxemia. 8 weeks after surgery, PTFE-treated mice showed a significantly reduced left ventricular ejection fraction. Moreover, the severity of diastolic dysfunction (measured as E/e') correlated significantly with the frequency of apneas. Accordingly, CaMKII expression was significantly increased in PTFE mice and correlated significantly with the frequency of apneas.

CONCLUSIONS

We describe here the first mouse model of spontaneous inspiratory flow limitations, obstructive apneas, and hypoxia by tongue enlargement due to PTFE injection. These mice develop systolic and diastolic dysfunction and increased CaMKII expression. This mouse model offers great opportunities to investigate the effects of obstructive apneas.

Sleep apnea prediction in acute ischemic stroke (SLAPS score): a derivation study

BACKGROUND

Despite its high prevalence and negative impact, sleep-disordered breathing (SDB) remain commonly underdiagnosed and undertreated in stroke subjects. Multiple stroke comorbidities and risk factors, including obesity, hypertension, diabetes mellitus, ischemic heart disease, atrial fibrillation, and heart failure (H.F.) have been associated with SDB. This study aimed to examine associations of clinical and demographic characteristics with moderate-to-severe SDB (msSDB) in stroke patients and to develop a predictive score.

METHODS

Consecutive patients with ischemic stroke were enrolled in an open, prospective study. SDB was assessed using standard polysomnography. Clinical and demographic characteristics, as well as findings from echocardiography, entered the analysis. Multivariate logistic regression models were used to examine the associations with msSDB. Based on the results, an original score to predict msSDB was proposed and tested.

RESULTS

120 patients with acute ischemic stroke (mean age: 64.0 ± 12.2 years, median NIHSS: 4) were included. Body-mass index (BMI), wake-up stroke onset (WUS), and diastolic dysfunction were independently associated with msSDB. A score allocating 1 point for BMI≥25 kg/m² and <30 kg/m², 2 points for BMI≥30 kg/m², 1 point for WUS and 1 point for diastolic dysfunction resulted in an area under the curve of 0.81 (95% CI 0.71-0.90, p<0.001), sensitivity 82.9%, specificity 71.9% to identify stroke patients with msSDB.

CONCLUSIONS

BMI, WUS, and diastolic dysfunction were associated with msSDB. A simple score might help to identify acute stroke patients with msSDB, who are usual candidates for positive airway pressure therapy.

Evaluation of right ventricular performance and impact of continuous positive airway pressure therapy in patients with obstructive sleep apnea living at high altitude

Obstructive sleep apnea syndrome (OSAS) can lead to alterations in right ventricular (RV) performance and pulmonary vascular haemodynamics. Additionally, altitude-related hypoxia is associated with pulmonary vasoconstriction, and the effect of high-altitude on the pulmonary circulation in OSAS patients can be further altered. We sought to assess alterations in RV morphology and function in OSAS patients living at high altitude by way of 2-dimensional speckle tracking echocardiography (2D-STE), real-time 3- dimensional echocardiography (RT-3DE) and cardiac biomarkers. We also evaluate the impact of continuous positive airway pressure (CPAP) treatment on RV performance. Seventy-one patients with newly diagnosed OSAS and thirty-one controls were included in this study. All individuals were assessed for cardiac biomarkers as well as underwent 2D-STE and RT-3DE. Forty-five OSAS patients underwent CPAP therapy for at least 24 weeks and were studied before and after CPAP treatment. RT-3DE was used to measure RV volume, and calculate RV 3D ejection fraction (3D RVEF). Peak systolic strain was determined. Cardiac biomarkers, including C-reactive protein (CRP), N-terminal pro-B-type natriuretic peptide, and cardiac troponin T were also measured. Right atrium volume index, RV volume, RV volume index, systolic pulmonary artery pressure (sPAP), pulmonary vascular resistance (PVR) and level of serum CRP were significantly higher in OSAS group, while OSAS patients showed lower 3D RVEF and RV longitudinal strains. Compared to the patients with sPAP < 40 mmHg, RV longitudinal strains in patients with sPAP ≥ 40 mmHg were lower. Both RV global longitudinal strain and sPAP were associated with apnea–hypopnea index. Patients treated with 6 months of CPAP therapy had significant improvement in RV geometry and performance. RV structural abnormalities and RV function impairments were observed in OSAS patients living at moderate high altitude compared to control highlanders. The reversibility of these changes after application of CPAP were further confirmed.

Impact of obstructive sleep apnea on left ventricular mass index in men with coronary artery disease

STUDY OBJECTIVES

Left ventricular hypertrophy (LVH) is associated with augmented risk for mortality in patients with coronary artery disease (CAD). These patients often have obstructive sleep apnea (OSA). We aimed to evaluate the relationship between OSA and the left ventricular mass index (LVMI) in men with CAD.

METHODS

Consecutive patients with CAD were recruited and underwent overnight portable monitoring for the assessment of OSA. LVMI was ascertained using high-resolution echocardiography. Univariate and multivariate regression analyses were conducted to explore the associations between the OSA parameters and the LVMI levels.

RESULTS

Of the 1,053 examined male patients with CAD, 425 (40.4%) had moderate-to-severe OSA (respiratory event index ≥ 15 events/h). The prevalence of LVH (LVMI > 125 g/m²) was 36.0% (n = 379). The mean LVMI values increased with increasing OSA severity (P < .001). Patients with respiratory event index ≥ 30 events/h had 2.30 (95% confidence interval 1.50-3.54, P < .001) times increased risk of LVH than those without OSA (respiratory event index < 5 events/h) independent of confounders. The minimum oxygen saturation levels were the strongest factor correlated with LVMI (β = -0.299, P = .004) of several OSA indices. Patients with minimum oxygen saturation < 70% had an adjusted odds ratio of 3.62 (95% confidence interval 1.81-7.25, P < .001) for LVH development compared with those with minimum oxygen saturation ≥ 90%.

CONCLUSIONS

OSA severity was associated with a higher likelihood of LVH in men with CAD, which is partially related to severe nocturnal intermittent hypoxemia. Aggressive effort at managing OSA among patients with CAD may further reduce the cardiovascular risk.

Impact of sleep apnoea-hypopnoea syndrome on diabetic neuropathy. A systematic review

INTRODUCTION

Diabetes mellitus and sleep apnoea-hypopnoea syndrome appear to be related, but it is not well defined whether there is an increased risk of peripheral neuropathy in patients with both diseases. For this reason, we conducted a systematic review.

METHODS

Bibliographic search in 3 electronic databases using a predefined strategy and the PRISMA methodology. Only original studies (any type of design) published from 2000 onwards in English, French, Portuguese or Spanish were included. A study quality scale was established.

RESULTS

Twelve articles were selected, of which six studied type 2 diabetic patients. The overall prevalence of sleep apnoea-hypopnoea syndrome was 43.7% (1,559/3,564 patients). Diabetic neuropathy was more frequent in patients with sleep apnoea-hypopnoea syndrome in nine studies, although significantly only in four (60% vs 27%, P<.001; 64.5% vs 36%, P=.03; 37% vs 23.4%, P<.02; 66.6% vs 0%, P=.007). In one study, diabetic neuropathy was more frequent in patients without sleep apnoea-hypopnoea syndrome (although not statistically significant) and in 2 no comparison was made between patients with/without sleep apnoea/hypopnoea syndrome.

CONCLUSIONS

The observed results suggest a relationship between diabetes mellitus and sleep apnoea-hypopnoea syndrome in the occurrence of diabetic neuropathy.

Locomotive Syndrome is a Risk Factor for the Dropout of Continuous Positive Airway Pressure Treatment in Patients with Obstructive Sleep Apnea Syndrome

Objective: The purpose of this study was to investigate the risk factors linked to patient dropout from continuous positive airway pressure (CPAP) therapy for the treatment of obstructive sleep apnea syndrome (OSAS). Methods: This study included 1191 patients with OSAS at baseline assessment, who were followed for 3 years. We evaluated clinical parameters, indicators related to OSAS treatment, exercise habits and the presence of locomotive syndrome (LS). LS was evaluated by a ‘loco-check’, as established by the Japanese Orthopedic Association. The OSAS patients were categorized at baseline as belonging to an ‘LS group’ or a ‘non-LS group’, and clinical parameters were compared. Results: Eighty-six patients (7.2%) dropped out of CPAP therapy during the 3 year follow-up period. The dropout rate of the LS group was significantly higher than that of the non-LS group. Using a Cox-proportional hazard model, the LS, old age and poor compliance were determined to be significant risk factors for dropping out of CPAP therapy. The hazard ratios (95% CI) of LS, elderly people and poor CPAP compliance were 2.11 (1.31–3.48), 1.80 (1.11–2.94) and 1.61 (1.04–2.47), respectively. Conclusion: LS may be the critical risk factor for dropping out of CPAP therapy among patients with OSAS.

Echocardiographic Changes with Positive Airway Pressure Therapy in Obesity Hypoventilation Syndrome. Long-Term Pickwick Randomized Controlled Clinical Trial

Rationale: Obesity hypoventilation syndrome (OHS) has been associated with cardiac dysfunction. However, randomized trials assessing the impact of long-term noninvasive ventilation (NIV) or continuous positive airway pressure (CPAP) on cardiac structure and function assessed by echocardiography are lacking.Objectives: In a prespecified secondary analysis of the largest multicenter randomized controlled trial of OHS (Pickwick Project; N = 221 patients with OHS and coexistent severe obstructive sleep apnea), we compared the effectiveness of three years of NIV and CPAP on structural and functional echocardiographic changes.Methods: At baseline and annually during three sequential years, patients underwent transthoracic two-dimensional and Doppler echocardiography. Echocardiographers at each site were blinded to the treatment allocation. Statistical analysis was performed using a linear mixed-effects model with a treatment group and repeated measures interaction to determine the differential effect between CPAP and NIV.Measurements and Main Results: A total of 196 patients were analyzed: 102 were treated with CPAP and 94 were treated with NIV. Systolic pulmonary artery pressure decreased from 40.5 ± 1.47 mm Hg at baseline to 35.3 ± 1.33 mm Hg at three years with CPAP, and from 41.5 ± 1.56 mm Hg to 35.5 ± 1.42 with NIV (P < 0.0001 for longitudinal intragroup changes for both treatment arms). However, there were no significant differences between groups. NIV and CPAP therapies similarly improved left ventricular diastolic dysfunction and reduced left atrial diameter. Both NIV and CPAP improved respiratory function and dyspnea.Conclusions: In patients with OHS who have concomitant severe obstructive sleep apnea, long-term treatment with NIV and CPAP led to similar degrees of improvement in pulmonary hypertension and left ventricular diastolic dysfunction.Clinical trial registered with www.clinicaltrials.gov (NCT01405976).

Obstructive sleep apnoea treatment and blood pressure: which phenotypes predict a response? A systematic review and meta-analysis

The treatment for obstructive sleep apnoea (OSA) with continuous positive airway pressure (CPAP) or mandibular advancement devices (MADs) is associated with blood pressure (BP) reduction; however, the overall effect is modest. The aim of this systematic review and meta-analysis of randomised controlled trials (RCTs) comparing the effect of such treatments on BP was to identify subgroups of patients who respond best to treatment.The article search was performed in three different databases with specific search terms and selection criteria. From 2289 articles, we included 68 RCTs that compared CPAP or MADs with either passive or active treatment. When all the studies were pooled together, CPAP and MADs were associated with a mean BP reduction of -2.09 (95% CI -2.78- -1.40) mmHg for systolic BP and -1.92 (95% CI -2.40- -1.43) mmHg for diastolic BP and -1.27 (95% CI -2.34- -0.20) mmHg for systolic BP and -1.11 (95% CI -1.82- -0.41) mmHg for diastolic BP, respectively. The subgroups of patients who showed a greater response were those aged <60 years (systolic BP -2.93 mmHg), with uncontrolled BP at baseline (systolic BP -4.14 mmHg) and with severe oxygen desaturations (minimum arterial oxygen saturation measured by pulse oximetry <77%) at baseline (24-h systolic BP -7.57 mmHg).Although this meta-analysis shows that the expected reduction of BP by CPAP/MADs is modest, it identifies specific characteristics that may predict a pronounced benefit from CPAP in terms of BP control. These findings should be interpreted with caution; however, they are particularly important in identifying potential phenotypes associated with BP reduction in patients treated for OSA.

Association Between Sleep Disordered Breathing and Left Ventricular Function: A Cross-Sectional Analysis of the ECHO-SOL Ancillary Study

BACKGROUND

Prior studies have found that sleep-disordered breathing (SDB) is common among those with left ventricular (LV) dysfunction and heart failure. Few epidemiological studies have examined this association, especially in US Hispanic/Latinos, who may be at elevated risk of SDB and heart failure.

METHODS

We examined associations between SDB and LV diastolic and systolic function using data from 1506 adults aged 18 to 64 years in the Hispanic Community Health Study/Study of Latinos ECHO-SOL Ancillary Study (2011-2014). Home sleep testing was used to measure the apnea-hypopnea index, a measure of SDB severity. Echocardiography was performed a median of 2.1 years later to quantify LV diastolic function, systolic function, and structure. Multivariable linear regression was used to model the association between apnea-hypopnea index and echocardiographic measures while accounting for the complex survey design, demographics, body mass, and time between sleep and echocardiographic measurements.

RESULTS

Each 10-unit increase in apnea-hypopnea index was associated with 0.2 (95% CI, 0.1-0.3) lower E', 0.3 (0.1-0.5) greater E/E' ratio, and 1.07-fold (1.03-1.11) higher prevalence of diastolic dysfunction as well as 1.3 (0.3-2.4) g/m2 greater LV mass index. These associations persisted after adjustment for hypertension and diabetes mellitus. In contrast, no association was identified between SDB severity and subclinical markers of LV systolic function.

CONCLUSIONS

Greater SDB severity was associated with LV hypertrophy and subclinical markers of LV diastolic dysfunction. These findings suggest SDB in Hispanic/Latino men and women may contribute to the burden of heart failure in this population.

Diastolic dysfunction in men with severe obstructive sleep apnea syndrome but without cardiovascular or oxidative stress-related comorbidities

Background:

We aimed to evaluate whether the severity of obstructive sleep apnea syndrome (OSAS) per se affects the prevalence of left ventricular (LV) diastolic dysfunction in patients without comorbidities.

Methods:

A total of 42 patients with first-diagnosed severe OSAS [apnea–hypopnea index (AHI) > 30] and 25 controls (AHI < 5), having been referred for snoring to the Sleep Laboratory Department of our tertiary Hospital, were enrolled in the study. Inclusion criteria were absence of any cardiovascular or oxidative stress-related comorbidities, and age between 20 and 70 years. Clinical, laboratory, echocardiographic, and polysomnographic data were recorded prospectively. Diastolic dysfunction diagnosis and grading was based on 2016 ASE/EACVI recommendations.

Results:

Severe OSAS was associated with significantly increased prevalence and degree of diastolic dysfunction (26/42; 61.9%) compared with controls (7/25; 28%) (p = 0.007). AHI ⩾ 55 (dichotomous value of severe OSAS subset) was also characterized by greater prevalence and degree of diastolic dysfunction compared with 30 < AHI < 55 patients (p = 0.015). In the severe OSAS subset, age >45 years-old, height <1.745 m, body-mass index (BMI) >27.76 kg m⁻², OSAS severity (AHI > 57.35), oxidative stress (overnight reduction of reduced to oxidized glutathione ratio < 18.44%), and BMI/height ratio > 16.155 kg m⁻³ (an index describing ‘dense’, short-heavy patients) presented significant diagnostic utility in identifying diastolic dysfunction in ROC-curve analysis (0.697 ⩾ AUC ⩾ 0.855, 0.001 ⩽ p ⩽ 0.018). In binary logistic regression model, advanced age (OR 1.23, 95% CI 1.025–1.477; p = 0.026) and AHI (OR 1.123, 95% CI 1.007–1.253; p = 0.036) showed independent association with diastolic dysfunction in severe OSAS.

Conclusions:

The present prospective study may suggest that severe OSAS is significantly associated with LV diastolic dysfunction; OSAS clinical severity exerts a positive influence on (and possibly constitutes an independent risk factor of) LV diastolic dysfunction.

The reviews of this paper are available via the supplementary material section.

Subclinical impairment of dynamic left ventricular systolic and diastolic function in patients with obstructive sleep apnea and preserved left ventricular ejection fraction

BACKGROUND

Hypoxia affects myocardial oxygen supply resulting in subclinical cardiac dysfunction in obstructive sleep apnea (OSA) patients, with cardiovascular complications being associated with increased oxidative burst (OB). The aims of our study were to assess left ventricular (LV) dynamic myocardial deformation and diastolic reserve at rest and upon exercise, along with OB determination in this patients subset.

METHODS

Conventional echocardiography, Doppler myocardial imaging and LV 2D speckle tracking echocardiography were performed in 55 OSA patients with preserved LV ejection fraction (EF) and 35 age and sex-comparable healthy controls. Peripheral OB levels were evaluated by flow cytometry.

RESULTS

Despite comparable LVEF, LV global longitudinal strain (GLS) was significantly reduced in OSA at rest (- 13.4 ± 3.8 vs - 18.4 ± 3.3 in controls, P <  0.001) and at peak exercise (- 15.8 ± 2.6 vs - 23.4 ± 4.3, P <  0.001). Systolic pulmonary artery pressure (sPAP) and E/E' ratios increase during effort were higher in OSA than in controls (ΔsPAP 44.3% ± 6.4 vs 32.3% ± 5.5, P <  0.0001, and ΔE/E' 87.5% ± 3.5 vs 25.4% ± 3.3, P <  0.0001, respectively). The best correlate of E/E' at peak stress was peak exertion capacity (r = - 0.50, P <  0.001). OB was also increased in OSA patients (P = 0.001) but, unlike OSA severity, was not associated with LV diastolic dysfunction.

CONCLUSIONS

Evaluation of diastolic function and myocardial deformation during exercise is feasible through stress echocardiography. OSA patients with preserved LVEF show subclinical LV systolic dysfunction, impaired LV systolic and diastolic reserve, reduced exercise tolerance, and increased peripheral levels of OB. Therapy aimed at increasing LV diastolic function reserve might improve the quality of life and exercise tolerability in OSA patients.

Obstructive sleep apnea and cardiac mechanics: how strain could help us?

Obstructive sleep apnea (OSA) syndrome is the most common sleep-breathing disorder, which is associated with increase cardiovascular morbidity and mortality. OSA increases risk of resistant arterial hypertension, coronary artery disease, heart failure, pulmonary hypertension, and stroke. Studies showed the significant relationship between OSA and cardiac remodeling. The majority of investigations were focused on the left ventricle and its hypertrophy and function. Fewer studies investigated right ventricular structure and function revealing deteriorated diastolic and systolic function. Data regarding left and right ventricular mechanics in OSA patients are scarce and controversial. The results of the studies that were focused on the influence of continuous positive airway pressure and weight reduction on cardiac remodeling revealed favorable effect on left and right ventricular structure and function. Recently published analyses confirmed positive effect of treatment on cardiac mechanics. Deterioration of left and right ventricular mechanics occurs before functional and structural cardiac impairments in the cascade of cardiac remodeling and therefore the assessment of left and right ventricular strain may represent a cornerstone in detection of subtle cardiac changes that develop significantly before other, often irreversible, alterations. Considering the fact that left and right ventricular strains have important predictive value in wide range of cardiovascular diseases, one should consider the evaluation of left and right ventricular strains in the routine echocardiographic assessment at all stages of disease-from diagnosis, during follow-up and evaluation of therapeutic effects. The main aim of this review is to provide the current overview of cardiac mechanics in OSA patients before and after (during) therapy, as well as mechanisms that could be responsible for cardiac changes.