Consequences of obstructive sleep apnoea syndrome on left ventricular geometry and diastolic function

Sleep apnea and sudden death in the non-cardiac population: A systematic review

INTRODUCTION

Obstructive sleep apnea (OSA) is one of the main risk factors for cardiovascular diseases and is associated with both morbidity and mortality. OSA has also been linked to arrhythmias and sudden death.

OBJECTIVE

To assess whether OSA increases the risk of sudden death in the non-cardiac population.

METHODS

This is a systematic review of the literature. The descriptors "sudden death" and "sleep apnea" and "tachyarrhythmias" and "sleep apnea" were searched in the PubMed/Medline and SciELO databases.

RESULTS

Thirteen articles that addressed the relationship between OSA and the development of tachyarrhythmias and/or sudden death with prevalence data, electrocardiographic findings, and a relationship with other comorbidities were selected. The airway obstruction observed in OSA triggers several systemic repercussions, e.g., changes in intrathoracic pressure, intermittent hypoxia, activation of the sympathetic nervous system and chemoreceptors, and release of catecholamines. These mechanisms would be implicated in the appearance of arrhythmogenic factors, which could result in sudden death.

CONCLUSION

There was a cause-effect relationship between OSA and cardiac arrhythmias. In view of the pathophysiology of OSA and its arrhythmogenic role, studies have shown a higher risk of sudden death in individuals who previously had heart disease. On the other hand, there is little evidence about the occurrence of sudden death in individuals with OSA and no heart disease, and OSA is not a risk factor for sudden death in this population.

Relationship between ODI and sleep structure of obstructive sleep apnea and cardiac remodeling

PURPOSE

The purpose of the study was to evaluate the quantitative relationship between Oxygen Desaturation Index (ODI) and sleep structure of obstructive sleep apnea (OSA) and cardiac remodeling.

METHODS

In this study, patients were enrolled from January 2015 to October 2022, and were divided into 3 groups according to AHI: patients with AHI < 15, patients with 15 ≤ AHI < 30, and 260 patients with AHI ≥ 30. Stratified linear regression was used to analyze independent risk factors for cardiac remodeling in OSA.

RESULTS

A total of 479 patients were enrolled. We found that compared with AHI < 15 group (n = 120), the group with AHI > 30 (n = 260) had increased left atrial anteroposterior diameter, left ventricular end-diastolic internal diameter, left ventricular posterior wall thickness, right ventricular anteroposterior diameter, and interventricular septal thickness (P < 0.05). The group with 15 ≤ AHI ≤ 30 (n = 99) had increased left atrial anteroposterior diameter (P < 0.05). Multivariate linear regression revealed that N2 sleep was an independent risk factor for left ventricular posterior wall thickness, with positive correlation (p < 0.05). N3 sleep was an independent risk factor for transverse right atrial diameter and right ventricular anteroposterior diameter, with negative correlation (P < 0.05). ODI was an independent risk factor for interventricular septal thickness, with positive correlation (P < 0.05). The arousal index was an independent risk factor for increased left atrial anteroposterior diameter, with positive correlation (P < 0.05).

CONCLUSIONS

Increased ODI is an independent risk factor for interventricular septal thickness, while decreased slow wave sleep is an independent risk factor for right heart remodeling in OSA.

Association of the TNF-α-308G>A gene polymorphism with left ventricular geometry and functional abnormalities in obstructive sleep apnea subjects

OBJECTIVE

Tumor necrosis factor-α (TNF-α) can induce left ventricular remodeling. In this study, we investigated whether the TNF-α-308G>A polymorphism is associated with left ventricular geometry (LVG) and left ventricular functional abnormalities in obstructive sleep apnea (OSA) subjects.

METHODS

Two hundred and seventy-eight subjects were enrolled. Echocardiography and genetic data were assessed in all patients. Geometric patterns of the left ventricle were determined from the relative wall thickness and left ventricular mass index (LVMI). Genetic analysis for the TNF-α-308G>A SNP rs1800629 was identified by Sanger sequencing. The correlations of the TNF-α-308G>A polymorphism with LVG and left ventricular function were analyzed by difference analysis and logistic regression.

RESULTS

The chi-square test showed that there were differences in genotype distributions among the four groups (p = 0.033), such that the frequency of GA+AA genotypes was significantly higher in the concentric hypertrophy group than in the normal geometry group (p < 0.05). Independent sample T tests showed that the GA+AA genotypes had higher IVST, LVPWT, LVMI, E/e' values, and lower e' values than those of the GG genotype (p < 0.05). Logistic regression analysis showed that the TNF-α-308G>A polymorphism was independently correlated with eccentric hypertrophy (OR = 2.456, p = 0.047) and concentric hypertrophy (OR = 2.456, p = 0.047).

CONCLUSION

In OSA patients, the TNF-α-308G>A polymorphism was linked to LVG and abnormal left ventricular diastolic function, suggesting that the TNF-α-308G>A polymorphism may have an important influence on LVG alterations.

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.

Serum uric acid is related to left ventricular geometry and function in patients with obstructive sleep apnea

INTRODUCTION

Serum uric acid (SUA) is an oxidative stress-related biomarker of cardiovascular risk. We sought to discover whether or not SUA was related to left ventricular geometry (LVG) and function among individuals with obstructive sleep apnea (OSA).

METHODS

Patients with OSA and healthy controls were assessed for clinical features, echocardiography, polysomnography, and blood biochemical data. Patients with OSA were divided into four groups: normal geometry (NG), concentric remodeling (CR), eccentric hypertrophy (EH), and concentric hypertrophy (CH). Correlations of SUA with left ventricular (LV) structure and function were examined through Pearson correlation analysis. The risk variables of LVG were investigated using a multivariate logistic regression model.

RESULTS

Compared to controls, patients with OSA had greater SUA levels. The eccentric hypertrophy (EH) and concentric hypertrophy (CH) groups showed substantially greater SUA levels than the normal geometry (NG) and concentric remodeling (CR) groups (p < 0.05). SUA correlated positively with left ventricular mass index (LVMI) and relative wall thickness (RWT) but negatively with the E/A ratio, according to the Pearson correlation analysis. SUA independently affected EH (OR = 1.021, 95%CI = 1.015-1.028, p < 0.001) and CH (OR = 1.034, 95%CI = 1.025-1.043, p < 0.001) in patients with OSA by the multivariate logistic regression model.

CONCLUSIONS

Patients with OSA had elevated levels of SUA, which were seen to be closely linked with abnormal LVG and function. The findings suggest that SUA may raise the risk of LV structural and functional impairment in patients with OSA.

Association of continuous positive airway pressure therapy on cardiac hypertrophy in patients with sleep apnea comorbid with type 2 diabetes mellitus

Previous reports indicated the therapeutic effect of chronic continuous positive airway pressure (CPAP) therapy on cardiac hypertrophy due to sleep apnea syndrome. However, little is known for cases involving diabetic complications. This retrospective observational study examined the effects of CPAP therapy on left ventricular hypertrophy (LVH) in patients with obstructive sleep apnea syndrome (OSAS) and type 2 diabetes mellitus (T2DM). For all cases, the observation period was 3 years from the time when the patient was introduced to CPAP therapy. Overall, 123 patients were divided into a good CPAP group (CPAP ≥4 h/day, n = 63) and non-adherence group (CPAP <4 h/day, n = 60). The mean CPAP usage times were 5.58 ± 1.23 and 1.03 ± 1.17 h/day in the good CPAP and non-adherence groups, respectively. Regression tendencies of the thickness of the left ventricular posterior (-0.30 ± 1.19 mm) and interventricular septal walls (-0.48 ± 1.22 mm) were observed in the good CPAP group. Hypertrophic tendencies of the left ventricular posterior wall (+0.59 ± 1.44 mm) and interventricular septal wall thickness (+0.59 ± 1.43) were observed in the non-adherence group. Left ventricular posterior wall thickness (coefficient: -0.254, p = 0.0376) and interventricular septal wall thickness (coefficient: -0.426, p = 0.0006) were more likely to be greater in the non-adherence group than in the good CPAP group. Patients in the non-adherence group with an apnea hypopnea index ≥30 had increased left ventricular posterior wall thickness (coefficient: -0.263, p = 0.0673) and interventricular septal wall thickness (coefficient: -0.450, p = 0.0011). In conclusion, appropriate CPAP therapy is an effective treatment for LVH in patients with T2DM and OSAS, especially for severe cases.

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.

Mandibular advancement device treatment and reverse left ventricular hypertrophic remodeling in patients with obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is associated with cardiovascular comorbidities such as left ventricular (LV) hypertrophy. Whether OSA is an independent etiological factor for this hypertrophic remodeling is yet unknown. Continuous positive airway pressure partially reverses this hypertrophy, but data regarding the effect of mandibular advancement devices on LV remodeling are scarce. The aim of this prospective trial is to evaluate the effect of mandibular advancement device therapy on LV geometry and function in patients with OSA.

METHODS

At baseline and 6-month follow-up, participants underwent a home sleep apnea test, 24-hour ambulatory blood pressure monitoring and a 2-dimensional Doppler and tissue Doppler echocardiography.

RESULTS

Sixty-three patients (age: 49 ± 11 years; body mass index: 27.0 ± 3.4 kg/m²; baseline apnea-hypopnea index home sleep apnea test: 11.7 [8.2; 24.9] events/h) completed the 6-month follow-up visit. Overall, blood pressure values and parameters of LV function were within normal ranges at baseline and did not change under mandibular advancement device therapy. In contrast, the interventricular septum thickness was at the upper limits of normal at baseline and showed a significant decrease at 6-month follow-up (11.1 ± 2.1 mm vs 10.6 ± 2.0 mm, P = .03). This significant improvement is only found in responders but not in nonresponders. There was no correlation between the decrease of interventricular septum thickness and the change in blood pressure.

CONCLUSIONS

In mildly obese, normotensive patients with OSA we observed significant reverse hypertrophic remodeling after 6 months of successful mandibular advancement device therapy, with maintained normotensive systemic blood pressure. This suggests that OSA is an independent factor in the pathophysiology of LV hypertrophy in these patients.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Name: Evaluation of the Cardiovascular Effects of the MAS in the Treatment of Obstructive Sleep Apnea; URL: https://clinicaltrials.gov/ct2/show/NCT02320877; Identifier: NCT02320877.

CITATION

Dieltjens M, Vanderveken OM, Shivalkar B, et al. Mandibular advancement device treatment and reverse left ventricular hypertrophic remodeling in patients with obstructive sleep apnea. J Clin Sleep Med. 2022;18(3):903-909.

Predictive echocardiographic factors of severe obstructive sleep apnea

Introduction

obstructive sleep apnea (OSA) is a common chronic pulmonary disease, characterized by repetitive collapse of the upper respiratory airways, leading to oxygen desaturation. This condition is recognized to be associated with cardiovascular disease. Several studies have shown the effects of OSA on both geometry and cardiac function, with conflicting results. We aimed to investigate the relationship between echocardiographic abnormalities and the severity of OSA.

Methods

this is a cross-sectional single center study including patients, without any cardiovascular or pulmonary comorbidities, with polygraphy proven OSA. All participants underwent a detailed transthoracic echocardiography (TTE).

Results

a total of 93 patients were included in the study, with 62.2% (n=56) females. According to the apnea hypopnea index (AHI), patients were divided into two groups: mild to moderate OSA (5≤ AHI< 30/H) and severe OSA (AHI≥ 30/H). There were no differences in baseline characteristics between the two groups. The assessment of echocardiographic parameters demonstrated that severe OSA have a higher left ventricular end-systolic (LVES) (47.6±7.2 VS 46.2±4.7), left ventricular end-diastolic (LVED) (31.3±6.2 VS 28.9±4.5) diameters and interventricular septum (IVS) thickness (12.7±2.4 VS11.7±2.5) diameters rather than mild to moderate OSA without a significant difference between the two groups. Furthermore, severe OSA patients had lower mean value of left ventricular ejection fraction (LVEF) and fractional shortening (FS) equal to 62.1±9.7 and 32.5±6.3 respectively. The difference between the two groups was not statistically significant. However, a significant association was shown between severity of OSA and left ventricular (LV) diastolic dysfunction, right ventricular internal diameter (RVID) and systolic pulmonary artery pressure (sPAP), with p=0.05, p=0.05 and p= 0.03 respectively. The RVID was also independently associated to the severity of the OSA (aOR 1.33, 95%CI: 0.99-1.79; p=0.05).

Conclusion

using bidimensional echocardiography showed a relationship between severe OSA and right ventricular parameters (diastolic dysfunction and RVID) and sPAP.

The impact of left ventricular geometry on left atrium phasic function in obstructive sleep apnea syndrome: a multimodal echocardiography investigation

BACKGROUND

Left ventricular geometry and left atrium (LA) enlargement are risk factors for cardiovascular disease. However, reports on the relationship between left ventricular geometry and LA volume yielded contradictory findings, and LA phasic function remains unclear. Hence, this study aimed to investigate the influence of left ventricular geometry on LA volume and phasic function in patients with obstructive sleep apnea syndrome (OSAS) via a multimodal echocardiographic approach.

METHODS

In this cross-sectional study, 221 patients with OSAS (age 20-68 years, mean age 45.27 ± 12.50 years) underwent clinical evaluation, polysomnography, and multimodal echocardiographic examination with two-dimensional echocardiography (2DE), two-dimensional speckle-tracking echocardiography (2D-STE) and three-dimensional echocardiography (3DE). Based on conventional classification of left ventricular geometry, patients with OSAS were divided into four groups: normal geometry (NG), concentric remodeling (CR), concentric hypertrophy (CH), and eccentric hypertrophy (EH).

RESULTS

Based on 2DE and 3DE, the LA volumes and indices gradually increased from NG to CH. Additionally, 2DE and 3DE LA maximum volume index (LAVImax) were higher in patients with CH and EH than in patients with NG and CR (P < 0.05). The reservoir function, estimated by LA total emptying fraction (LA TotEF) was lower in patients with CH than in patients with NG in 2DE and 3DE (both, P < 0.05). Also, LA conduit function, evaluated by LA passive emptying fraction (LA PassEF) was lower in patients with CH than in patients with NG and CR, and in patients with EH than in those with NG in 2DE and 3DE (all, P < 0.05). The LA booster pump function, evaluated by LA active emptying fraction (LA ActEF) showed no statistically significant difference in 2DE; however, it was greater in patients with CH than in those with NG in 3DE. Similar results were obtained by 2D-STE, and CH was significantly associated with LA strain during systole (LAS-S, β = - 0.546, 95%CI: - 6.371-(- 3.444); P < 0.001), early diastole (LAS-E, β = - 0.636, 95%CI: - 9.532-(- 5.710); P < 0.001), and late diastole (LAS-A, β = - 0.450, 95%CI: 1.518-3.909; P < 0.001) in multiple linear regression.

CONCLUSIONS

The LA phasic function changed with left ventricular geometry via multimodal echocardiography. CH had the most notable negative effect on the maximum volume and phasic function of the LA.

Obstructive sleep apnoea, intermittent hypoxia and heart failure with a preserved ejection fraction

Obstructive sleep apnoea (OSA) is recognised to be a potent risk factor for hypertension, coronary heart disease, strokes and heart failure with a reduced ejection fraction. However, the association between OSA and heart failure with a preserved ejection fraction (HFpEF) is less well recognised. Both conditions are very common globally.It appears that there are many similarities between the pathological effects of OSA and other known aetiologies of HFpEF and its postulated pathophysiology. Intermittent hypoxia induced by OSA leads to widespread stimulation of the sympathetic nervous system, renin-angiotensin-aldosterone system and more importantly a systemic inflammatory state associated with oxidative stress. This is similar to the consequences of hypertension, diabetes, obesity and ageing that are the common precursors to HFpEF. The final common pathway is probably via the development of myocardial fibrosis and structural changes in collagen and myocardial titin that cause myocardial stiffening. Thus, considering the pathophysiology of OSA and HFpEF, OSA is likely to be a significant risk factor for HFpEF and further trials of preventive treatment should be considered.

Risk of Obstructive Sleep Apnea and Echocardiographic Parameters

BACKGROUND

Obstructive sleep apnea (OSA) is a chronic progressive disorder with high mortality and morbidity rate, associated with cardiovascular diseases (CVD), especially heart failure (HF). The pathophysiological changes related to OSA can directly affect the diastolic function of the left ventricle.

OBJECTIVES

To assess the association of the risk of OSA, evaluated by the Berlin Questionnaire (BQ), and echocardiographic (ECHO) parameters related to diastolic dysfunction in individuals without HF assisted in primary care.

METHODS

A cross-sectional study that included 354 individuals (51% women) aged 45 years or older. All individuals selected were submitted to an evaluation that included the following procedures: consultation, filling out the BQ, clinical examination, laboratory examination and transthoracic Doppler echocardiography (TDE). Continuous data are presented as medians and interquartile intervals, and categoric variables in absolute and relative frequencies. The variables associated with risk of OSA and at the 0.05 level integrated the gamma regression models with a log link function. A value of p < 0.05 was considered an indicator of statistical significance. Exclusion criteria were presence of HF, to fill out the BQ and patients with hypertension and obesity not classified as high risk for OSA by other criteria. All individuals were evaluated on a single day with the following procedures: medical appointment, BQ, laboratory tests and ECHO.

RESULTS

Of the 354 individuals assessed, 63% were classified as having high risk for OSA. The patients with high risk for OSA present significantly abnormal diastolic function parameters. High risk for OSA confirmed positive and statistically significant association, after adjustments, with indicators of diastolic function, such as indexed left atrium volume LAV-i (p = 0.02); E'/A' (p < 0.01), A (p = 0.02), E/A (p < 0.01).

CONCLUSION

Our data show that patients at high risk for OSA present worsened diastolic function parameters measured by TDE.

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).

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.

Histological, Ultrastructural, and Physiological Evaluation of a Rat Model of Obstructive Sleep Apnea Syndrome

BACKGROUND Patients with obstructive sleep apnea syndrome (OSAS) are at an increased risk of cardiovascular disease. The aims of this study were to develop a rat model of OSAS and to validate the use of the model by investigating respiratory and cardiovascular physiological parameters and morphological changes by light microscopy and electron microscopy. MATERIAL AND METHODS Sixty 3-month-old Sprague-Dawley rats were assigned to the model group (n=30) and the control group (n=30). The rats in the OSAS model group were injected with 0.1 ml sodium hyaluronate solution into the upper respiratory tract at the junction between the hard and soft palate. After one month, the model and normal rats were compared using tests of respiratory and cardiac function, and histology and electron microscopy of the lung and cardiac tissue. RESULTS In the rat model of OSAS, airway obstruction resulted in the collapse of the upper airway. Tests of respiratory function showed that the oxygen partial pressure, oxygen concentration, and oxygen saturation in the model group were significantly lower when compared with the control group. In the model group, histology of the heart showed cardiac myocyte disarray, and electron microscopy showed vacuolar degeneration and mitochondrial abnormalities. The rat model of upper airway occlusion showed pulmonary and cardiac changes that have been described in OSAS. CONCLUSIONS A rat model of upper airway occlusion resulted in physiological and morphological changes in the lung and heart due to hypoxia, and may be used for future studies on OSAS.

Left ventricular diastolic dysfunction in patients with obesity hypoventilation syndrome

Background

Obesity hypoventilation syndrome (OHS) can be complicated by several cardiovascular conditions. We assessed the prevalence and factors associated with left ventricular diastolic dysfunction (LVDD) in patients with OHS.

Methods

In this prospective observational study, all consecutive OHS patients referred to the sleep disorders clinic between January 2002 to December 2016 were included (n=113). Demographic data, echocardiography, sleep parameters, arterial blood gases (ABGs), and lung functions were recorded.

Results

Of 113 patients with OHS who participated, 76 patients (67%) had LVDD. More than two-thirds had grade 1 LVDD. Median body mass index (BMI) was 42.8 kg/m². Median PaCO₂ was 55.8 mmHg. Median apnea hypopnea index (AHI) was 52 (25-38.5). Eighty-four (75.7%) patients were hypertensive, and 60 (54.1%) were diabetic. To minimize the effect of fluctuations in intrathoracic pressure during the obstructive respiratory events on the cardiac function, 38 OHS patients with mild to moderate OSA (AHI <30) were identified. Twenty-seven (71%) had LVDD. When compared to OHS patients without LVDD, patients with LVDD had higher BMI (47.4±6.5 versus 41.5±4.5, P=0.009). Hypertension was more common in OHS patients with LVDD than without LVDD (89.3% versus 54.5%, P=0.03). Correlation analysis revealed that hypertension (r=-0.37, P=0.016) had significant correlations with LVDD.

Conclusions

Diastolic left ventricular dysfunction is prevalent among OHS patients even in the absence of severe OSA. Hypertension and obesity were significantly more common in patients with LVDD. Assessment of diastolic dysfunction should be included in the initial evaluation of OHS patients to encourage the early institution of therapy.

Effects of continuous positive airway pressure therapy on left ventricular diastolic function: a randomised, sham-controlled clinical trial

Continuous positive airway pressure (CPAP) therapy may decrease left ventricular (LV) loads and improve myocardial oxygenation. In this study, we investigated the effect of CPAP on LV diastolic function compared with sham treatment in patients with severe obstructive sleep apnoea (OSA).

This 3-month prospective single-centre randomised sham-controlled trial analysed 52 patients with severe OSA. Patients were randomly assigned (1:1) to receive either CPAP or sham treatment for 3 months. The main investigator and patients were masked to the trial randomisation. The primary end-point was change of early diastolic mitral annular (e′) velocity over the 3-month period. Secondary end-points were pulse wave velocity (PWV), 24-h ambulatory blood pressure (BP) and variables of ventricular-vascular coupling at 3 months.

After 3 months of follow-up, CPAP treatment significantly increased the e′ velocity, and was greater than the sham treatment (0.65±1.70 versus −0.61±1.85 cm·s−1, p=0.014). The PWV, 24-h mean diastolic BP, night-time diastolic BP, arterial elastance index and ventricular-vascular coupling index after 3 months of follow-up decreased significantly in the CPAP group.

In patients with severe OSA, CPAP treatment for 3 months improved LV diastolic function more than sham treatment, and was accompanied by improvements in arterial stiffness and ventricular-vascular coupling.