Plasma brain natriuretic peptide in obstructive sleep apnea

Sympathetic overactivity and nocturnal diuresis in obstructive sleep apnea alter the response to hypertension therapy

BACKGROUND

Obstructive sleep apnea (OSA) is associated with high blood pressure that responds poorly to usual antihypertensive therapy.

METHODS AND RESULTS

Forty-one subjects with OSA had 25% higher plasma norepinephrine and 42% higher epinephrine measured every 2 h over 24 h than 20 control subjects. They also excreted more sodium during sleep. This suggested that that a sympatholytic would be a more successful antihypertensive than a diuretic. To test this hypothesis we treated a second group of 23 hypertensive apneics with placebo, 6 weeks of the sympatholytic guanfacine and 6 weeks of hydrochlorothiazide in a crossover study. Guanfacine lowered 24-hour blood pressure by 9.6/6.7 mmHg, more than the 5.4/2.9 mmHg effect of hydrochlorothiazide (P < 0.05). Nighttime systolic blood pressure dipping was poor at 6.6 ± 1.8%. Hydrochlorothiazide did not alter blood pressure dipping but guanfacine improved dipping to 9.1 ± 1.2%, a better result (P = 0.03) than from the diuretic. Central aortic pressure by pulse wave analysis was 120/84 mmHg on hydrochlorothiazide and 109/72 on guanfacine, (P < 0.05). Guanfacine, but not hydrochlorothiazide, improved baroreflex sensitivity, heart rate variability and flow mediated vascular dilation, suggesting that decreasing the elevated sympathetic nerve activity of obstructive sleep apnea returned vascular function toward normal.

CONCLUSIONS

OSA is the most common condition associated with antihypertensive treatment failure. It increased sympathetic nerve activity day and night. Drugs that block sympathetic nerve function are not among the 4 most commonly recommended classes of antihypertensives but diuretics are. Sympatholytic therapy was superior to diuretic treatment for hypertension associated with sleep apnea.

TRIAL REGISTRATION

NCT, NCT02699125, Registered 26 February 2016 - Retrospectively registered, https://clinicaltrials.gov/study/NCT02699125 .

A State-of-the-Art Review on Sleep Apnea Syndrome and Heart Failure

Heart failure (HF) affects many patients worldwide every year. It represents a leading cause of hospitalization and still, today, mortality remains high, albeit the progress in treatment strategies. Several factors contribute to the development and progression of HF. Among these, sleep apnea syndrome represents a common but still underestimated factor because its prevalence is substantially higher in patients with HF than in the general population and is related to a worse prognosis. This review summarizes the current knowledge about sleep apnea syndrome coexisting with HF in terms of morbidity and mortality to provide actual and future perspectives about the diagnosis, evaluation, and treatment of this association.

The role of 3D speckle tracking echocardiography in the diagnosis of obstructive sleep apnea and its severity

There is a consistent relationship between obstructive sleep apnea (OSA) and cardiovascular diseases. It is already recognized that OSA may influence the geometry and function of the right ventricle (RV). This has encouraged the development of echocardiographic evaluation for screening of OSA and its severity. Three-dimensional speckle tracking echocardiography (3D STE) is in assumption better, compared with 2D STE, because it overcomes the standard 2D echo limitations. Thus, the purpose of our study is to evaluate whether 3D STE measurements, could predict the positive diagnosis and severity of OSA. We enrolled 69 patients with OSA and 37 healthy volunteers who underwent a cardiorespiratory sleep study. 2DE was performed in all patients. RVEF and 3D RVGLS were measured by 3DSTE. NT pro BNP plasma level was also assessed in all participants. 3D RV GLS (- 13.5% vs. - 22.3%, p < 0.001) and 3D RVEF (31.9% vs. 50%, p < 0.001) were reduced in patients with OSA, compared with normal individuals. 3D Strain parameters showed better correlation to standard 2D variables, than 3D RVEF. Except for NT pro BNP (p = 0.059), all parameters served to distinguish between severe and mild-moderate cases of OSA. 3D STE may be a reliable and accurate method for predicting OSA. Consequently, 3D RV GLS is a good tool of assessing the RV global function in OSA, because it correlates well with other established measurements of RV systolic function. Furthermore, 3D RV GLS was a precise parameter in identifying severe cases of OSA, while NT pro BNP showed no association.

Silencing MR-1 Protects against Myocardial Injury Induced by Chronic Intermittent Hypoxia by Targeting Nrf2 through Antioxidant Stress and Anti-Inflammation Pathways

BACKGROUND

Patients with obstructive sleep apnea hypopnea syndrome (OSAHS) often have cardiac insufficiency mainly due to hypoxia/reperfusion injury caused by chronic intermittent hypoxia (CIH). Inflammation and oxidative stress are involved in the cardiovascular events of OSAHS patients. Studies have found that myofibrillation regulator-1 (MR-1) participates in the pathological process of OSAHS-induced myocardial injury, but the specific mechanism is still unclear.

METHODS

We used a CIH-induced rat model to simulate the process of OSAHS disease. Indices of myocardial injury, inflammation, and oxidative stress were detected using quantitative PCR and enzyme-linked immunosorbent assay (ELISA). After administration of adenoassociated viral vector (AAV) encoding silencing RNA against MR-1, we examined expression of the classic antioxidant stress pathway protein NF-E2-related factor 2 (Nrf2) using western blotting.

RESULTS

We found that levels of serum inflammatory factors tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-8 were increased, and we further observed disturbance of the oxidative stress system, in which the content of reactive oxygen species (ROS), superoxide dismutase (SOD), reduced glutathione (GSH), and malondialdehyde (MDA) was enhanced in CIH-induced rats. Subsequently, we detected that expression of Nrf2 and heme oxygenase-1 (HO-1) was slightly increased, while the expression of Kelch-like ECH-associated protein 1 (Keap-1) was significantly increased in the CIH model. Interestingly, after administration of silencing MR-1 AAV, the elevated levels of inflammatory factors were reduced, and the disordered oxidative stress system was corrected. Additionally, the expression of Nrf2 and HO-1 was distinctly increased, but the high expression of Keap-1 was decreased.

CONCLUSIONS

Our research results demonstrate that silencing MR-1 rescued the myocardium the injury from inflammatory and oxidative stress in CIH-induced rats by administration of the Nrf2 signaling pathway.

Endothelial dysfunction in obstructive sleep apnea patients

Purpose

Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for cardiovascular diseases. The aim of the study was to assess the influence of OSAS on endothelial dysfunction and thrombosis biomarkers and to evaluate the effect of treatment with continuous positive airway pressure (CPAP) on biomarker levels.

Methods

NT-proBNP, sICAM-1, endothelin-1, von Willebrand factor, D-dimers, and thrombin-antithrombin complex (TAT) were measured in 50 patients diagnosed with moderate-to-severe OSAS. All patients underwent transthoracic echocardiography, and 38 months after the inclusion, 16 CPAP users and 22 non-CPAP users were reassessed.

Results

Sleep-related indices of apnea-hypopnea index (AHI) and mean SpO₂ were associated with higher sICAM-1 levels (AHI < 30: 7.3 ± 4.7 vs. AHI ≥ 30: 19.5 ± 19.4 mg/ml, p = 0.04; SpO₂ ≥ 90%: 11.9 ± 9.3 vs. SpO₂ < 90%: 23.6 ± 25.8, p = 0.04). sICAM-1 levels were significantly higher in obese patients, particularly with BMI ≥ 40. Plasma levels of TAT were significantly correlated with the increased right ventricular size (right ventricular diameter ≤ 37 mm: 0.86 ± 0.70 vs. > 37 mm: 1.96 ± 1.20 ng/ml, p = 0.04). Endothelin-1 levels were higher in patients with decreased right ventricular function (right ventricle TDI-derived S′ ≥ 12 cm/s: 11.5 ± 10.9 vs. < 12 cm/s: 26.0 ± 13.2 pg/ml, p = 0.04). An increase in NT-proBNP was related to impaired parameters of the right ventricular contractile function. There were no correlations between long-term CPAP therapy and the levels of biomarkers.

Conclusion

Severe OSAS influences endothelial damage as manifested by an increase in sICAM-1 levels. Changes in right ventricular structure and function, observed mainly in patients with higher TAT and endothelin-1 levels, are also manifested by an increase in NT-proBNP levels. Long-term CPAP treatment does not seem to influence biomarkers in patients with moderate-to-severe OSAS, which may help to explain the lack of influence of CPAP on cardiovascular risk reduction.

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.

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.

Hematological indices as simple, inexpensive and practical severity markers of obstructive sleep apnea syndrome: a meta-analysis

Background

Clinical detection of inflammatory markers is useful to assess the degree of nocturnal hypoxia and predict the presence of complications in obstructive sleep apnea syndrome (OSAS) patients. Nowadays, some researchers proposed that hematological parameters could be substituted for novel disease-specific biochemical markers (such as C-reactive protein) because they were comparatively cheap, simple and practical. But there was a contradiction whether the hematological parameters were positively correlated with the OSAS severity.

Methods

Medical databases were searched included PubMed, Web of Science, Scopus, Cochrane Library, Clinical Trial, Embase and Google Scholar (up to March 29, 2018). We used weighted mean differences (WMDs) with 95% confidence intervals (CIs) from random-effects model.

Results

Seventeen studies were included in this meta-analysis and results were presented by different hematological parameters. Pooled analysis showed that OSAS was associated with a high level of WBC (white blood cell, 11 studies, 2,206 subjects, WMD: 0.58; 95% CI: 0.31 to 0.85; P<0.0001), NLR (neutrophil-to-lymphocyte ratio, 5 studies, 1416 subjects, WMD: 0.46; 95% CI: 0.13 to 0.80; P=0.007), MPV (mean platelet volume, 8 studies, 1,854 subjects, WMD: 0.63; 95% CI: 0.29 to 0.98; P=0.0004), PDW (platelet distribution width, 6 studies, 1,911 subjects, WMD: 0.76; 95% CI: 0.47 to 1.06; P<0.00001), PLR (platelet-to-lymphocyte ratio, 3 studies, 998 subjects, WMD: 21.76; 95% CI: 8.54 to 34.99; P=0.001), RDW (red cell distribution width, 5 studies, 1,701 subjects, WMD: 0.31; 95% CI: 0.11 to 0.51; P=0.002) and HCT (hematocrit, 3 studies, 662 subjects, WMD: 1.58; 95% CI: 0.52 to 2.64; P=0.003). But OSAS was associated with a low level of LYM (lymphocyte, 5 studies, 1,285 subjects, WMD: -0.27; 95% CI: -0.49 to -0.06; P=0.01). There was a gradual rising trend from mild OSAS to severe OSAS existed in all subgroups.

Conclusions

Hematological indices are comparatively Simple, Inexpensive and Practical Severity Markers of OSAS including WBC, LYM, NLR, MPV, PDW, PLR, RDW and HCT.

Biomarkers in Sleep Apnea and Heart Failure

PURPOSE OF REVIEW

Sleep-disordered breathing (SDB) is highly prevalent in heart failure (HF) and may confer significant stress to the cardiovascular system and increases the risk for future cardiovascular events. The present review will provide updates on the current understanding of the relationship of SDB and common HF biomarkers and the effect of positive airway pressure therapy on these biomarkers, with particular emphasis in patients with coexisting SDB and HF.

RECENT FINDINGS

Prior studies have examined the relationship between HF biomarkers and SDB, and the effect of SDB treatment on these biomarkers, with less data available in the context of coexisting SDB and HF. Overall, however, the association of SDB and circulating biomarkers has been inconsistent. Further research is needed to elucidate the relationship between biomarkers and SDB in HF, to evaluate the clinical utility of biomarkers over standard methods in large, prospective studies and also to assess the impact of treatment of SDB on these biomarkers in HF via interventional studies.

The effect of surgical and non-surgical weight loss on N-terminal pro-B-type natriuretic peptide and its relation to obstructive sleep apnea and pulmonary function

Background

Obesity is a major risk factor for obstructive sleep apnea, impaired pulmonary function and heart failure, but obesity is also associated with paradoxically low levels of serum N-terminal pro-B-type natriuretic peptide (NT-proBNP). In subjects with severe obesity undergoing weight loss treatment, we assessed the associations between changes in severity of obstructive sleep apnea, pulmonary function and serum NT-proBNP levels.

Methods

One-year non-randomized controlled clinical trial. Participants, 69.6 % women, mean (SD) age 44.6 (10.8) years and body mass index (BMI) 45.1 (5.6) kg/m², underwent gastric bypass surgery (n = 76) or intensive lifestyle intervention (n = 63), resulting in 30 (8) % and 8 (9) % weight loss, respectively. The reference group included 30 normal weight, healthy, gender and age matched controls. Sleep recordings, arterial blood gases, pulmonary function and blood tests were assessed before and 1 year after the interventions.

Results

NT-proBNP concentrations increased significantly more after surgery than after lifestyle intervention. The post intervention values in both groups were significantly higher than in a normal weight healthy reference group. In the whole study population changes (∆) in NT-proBNP correlated significantly with changes in both BMI (r = −0.213) and apnea hypopnea index (AHI, r = −0.354). ∆NT-proBNP was, independent of age, gender and ∆BMI, associated with ∆AHI (beta −0.216, p = 0.021). ∆AHI was, independent of ∆BMI, significantly associated with changes in pO₂ (beta −0.204), pCO₂ (beta 0.199), forced vital capacity (beta −0.168) and forced expiratory volume first second (beta −0.160).

Conclusions

Gastric bypass surgery was associated with a greater increase in NT-proBNP concentrations than non-surgical weight loss treatment. Reduced AHI was, independent of weight loss, associated with increased NT-proBNP levels and improved dynamic lung volumes and daytime blood gases.

Clinical Trial Registration ClinicalTrials.gov NCT00273104, retrospectively registered Jan 5, 2006 (study start Dec 2005)

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-016-2241-x) contains supplementary material, which is available to authorized users.

Dynamic cycling in atrial size and flow during obstructive apnoea

Objective

Obstructive sleep apnoea (OSA) is strongly associated with cardiovascular disease. However, acute cardiovascular effects of repetitive airway obstruction are poorly understood. While past research used a sustained Mueller manoeuver to simulate OSA we employed a series of gasping efforts to better simulate true obstructive apnoeas. This report describes acute changes in cardiac anatomy and flow related to sudden changes in intrathoracic pressure.

Methods and results

26 healthy, normal weight participants performed 5–6 gasping efforts (target intrathoracic pressure −40 mm Hg) while undergoing Doppler echocardiography. 14 participants had sufficient echocardiographic images to allow comparison of atrial areas during the manoeuver with baseline measurements. Mitral and tricuspid E-wave and A-wave velocities postmanoeuver were compared with baseline in all participants. Average atrial areas changed little during the manoeuver, but variance in both atrial areas was significantly greater than baseline. Further, an inverse relationship was noted with left atrial collapse and right atrial enlargement at onset of inspiratory effort. Significant inverse changes were noted in Doppler flow when comparing the first beat postmanoeuver (pMM1) with baseline. Mitral E-wave velocity increased 9.1 cm/s while tricuspid E-wave velocity decreased 7.0 cm/s; by the eighth beat postmanoeuver (pMM8) values were not different from baseline. Mitral and tricuspid A-wave velocities were not different from baseline at pMM1, but both were significantly higher by pMM8.

Conclusions

Repetitive obstructive apnoeas produce dynamic, inverse changes in atrial size and Doppler flow across the atrioventricular valves. These observations have important implications for understanding the pathophysiology of OSA.

Relaxin in Obstructive Sleep Apnea: Relationship with Blood Pressure and Inflammatory Mediators

BACKGROUND

Obstructive sleep apnea (OSA) is associated with nocturnal intermittent hypoxia, which may be responsible for increased circulating levels of vascular endothelial growth factor (VEGF) and inflammatory mediators, such as metalloproteinases (MMPs), and which contributes to the pathogenesis of systemic hypertension. Why some OSA patients remain normotensive is poorly understood. Relaxin-2, a pregnancy hormone, may sometimes circulate in men and could increase in hypoxic conditions. It exerts a vasodilatory activity and can modulate the release of molecules, such as MMPs and VEGF.

OBJECTIVES

The objective of this study was to explore if circulating relaxin-2 in male OSA subjects may be related to OSA severity, to circulating levels of MMPs, of their inhibitors (tissue inhibitors of metalloproteinases; TIMPs), and of VEGF, and if it may protect from hypertension.

PATIENTS AND METHODS

Fifty untreated male subjects with suspected OSA were recruited. After nocturnal polysomnography, a morning venous blood sample was withdrawn. Then, 24-hour ambulatory blood pressure (BP) monitoring was performed.

RESULTS

The respiratory disturbance index in the sample was 30.4 [interquartile range (IQR) 15.6-55.2]. Relaxin-2 was detectable in 20 subjects. These subjects did not differ in OSA severity or diurnal and nocturnal BP from subjects with undetectable relaxin-2, but they showed lower TIMP-1 (126.8 ± 29.1 vs. 156.9 ± 41.7 pg/ml, respectively; p = 0.007) and a marginally higher MMP-9/TIMP-1 molar ratio [0.58 (IQR 0.23-1.35) vs. 0.25 (IQR 0.15-0.56); p = 0.052].

CONCLUSIONS

Relaxin-2 in male subjects was not related to OSA severity, but it was associated with lower TIMP-1. As it was often undetectable, even when BP values were normal, it is unlikely that it plays a role as a major factor protecting from hypertension in OSA.

Plasma natriuretic peptides in children and adolescents with obstructive sleep apnea and their changes following intervention

OBJECTIVE

This study aimed to evaluate circulating natriuretic peptides (NP) concentration in obese and non-obese children and adolescents with and without obstructive sleep apnea (OSA), and their levels following OSA treatment.

METHODS

Subjects with habitual snoring and symptoms suggestive of OSA were recruited. They underwent physical examination and overnight polysomnography (PSG). OSA was diagnosed if obstructive apnea-hypopnea index (OAHI) was ≥1/h. Fasting serum atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were taken after overnight PSG. The subjects were divided into obese, non-obese, with and without OSA groups for comparisons.

RESULTS

One hundred fourteen children (77 were boys) with a median [interquartile range (IQR)] age of 10.8 (8.3-12.7) years (range: 2.4-11.8 years) were recruited. Sixty-eight subjects were found to have OSA. NP levels did not differ between subjects with and without OSA in both obese and non-obese groups. Stepwise multiple linear regressions revealed that body mass index (BMI) z-score was the only independent factor associated with NP concentrations. Fifteen children with moderate-to-severe OSA (OAHI >5/h) underwent treatment and there were no significant changes in both ANP and BNP levels after intervention.

CONCLUSION

Body mass index rather than OSA was the main determinant of NP levels in school-aged children and adolescents.

Association between obstructive sleep apnea and elevated levels of type B natriuretic peptide in a community-based sample of women

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is associated with an increased risk of cardiovascular disease. One contributory factor may be hemodynamic stress due to the negative intrathoracic pressure during each episode of apnea. Type B natriuretic peptide (BNP) is secreted by the cardiac ventricles in response to volume expansion and pressure load and the authors hypothesized that there would be an association between indices of OSA during the night and levels of BNP in the morning.

SETTING

Community-based in Uppsala, Sweden.

PARTICIPANTS

There were 349 women who participated.

MEASUREMENTS AND RESULTS

Participants underwent full-night polysomnography and anthropometric measurements, and answered questionnaires about medical conditions and current medication. The morning after the polysomnography, blood samples were drawn for analysis of plasma BNP, C-reactive protein, creatinine, and hemoglobin. There was an increase in mean BNP as the severity of sleep apnea increased, increasing from a mean value of 8.5 ng/L among women with an apnea-hypopnea index (AHI) < 5 to 18.0 ng/L in women with an AHI ≥ 30. Elevated BNP levels (≥ 20 ng/L) were found in 29.8% of the women, whereas 70.2% had normal levels. The odds ratio was 2.2 for elevated BNP levels for women with an AHI of 5-14.9 in relation to women with an AHI < 5, 3.1 for women with an AHI of 15-29.9, and 4.6 for women with an AHI ≥ 30 after adjustment for age, body mass index, systolic blood pressure, antihypertensive drugs, and creatinine.

CONCLUSIONS

There is a dose-response relationship in women between the severity of sleep apnea during the night and the levels of BNP in the morning.

Obstructive sleep apnea in a Danish population of men and women aged 60-80 years with nocturia

INTRODUCTION AND HYPOTHESIS

The aim of the present study was in a case-control design to evaluate the association between nocturia and obstructive sleep apnea, in men and women who had nocturia ≥ 2 per night (nocturics) compared to those without nocturia (controls).

METHODS

Participants were randomly selected among respondents in a population study of 4000 elderly individuals. Nocturia was assessed using the validated Nocturia, Nocturnal Enuresis, and Sleep-interruption Questionnaire (NNES-Q). Nocturia (≥ 2 voids/night) or control (< 1 void/night) status was assessed by a 3-day frequency volume chart (FVC). Furthermore, all participants completed an overnight ambulatory polygraphic recording to identify obstructive sleep apnea (OSA).

RESULTS

Of 1111 eligible individuals, a total of 75 nocturics and 75 controls (13.5%) were included. Overall, the prevalence and severity of OSA among nocturics and controls was not significantly different. In a sub-analysis we found that 22 nocturics with OSA (69%) had nocturnal polyuria. This led to a significantly increased risk of having OSA (OR 2.8, 95% CI: 1.1-7.3, p < 0.05) when having nocturnal polyuria compared to other pathophysiological causes of nocturia (polyuria, low bladder capacity, a combination of nocturnal polyuria/low bladder capacity, and neither nocturnal polyuria/low bladder capacity).

CONCLUSIONS

Nocturia twice or more was not significantly associated with OSA. However, nocturics with nocturnal polyuria had a significantly higher risk of having OSA than nocturics with other pathophysiologies.

Relation of natriuretic peptide concentrations to central sleep apnea in patients with heart failure

BACKGROUND

Central sleep apnea (CSA) is frequent among patients with heart failure (HF) and associated with increased morbidity and mortality. Elevated cardiac filling pressures promote CSA and atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) secretion. We hypothesized that circulating natriuretic peptide concentrations predict CSA.

METHODS

Consecutive patients with HF (n = 44) with left ventricular ejection fraction (LVEF) ≤ 35% underwent polysomnography for detection of CSA. CSA was defined as an apnea-hypopnea index ≥ 15 with ≥ 50% central apneic events. The relation of natriuretic peptide concentrations to CSA was evaluated by estimation of ORs and receiver operator characteristics (ROCs).

RESULTS

Twenty-seven subjects (61%) had CSA, with men more frequently affected than women (73% vs 27%; OR, 7.1; P = .01); given that only three women had CSA, further analysis was restricted to men. Subjects with CSA had higher mean ANP (4,336 pg/mL vs 2,510 pg/mL, P = .03) and BNP concentrations (746 pg/mL vs 379 pg/mL, P = .05). ANP and BNP concentrations were significantly related to CSA (OR, 3.7 per 3,000 pg/mL, P = .03 and OR, 1.5 per 200 pg/mL, P = .04, respectively), whereas age, LVEF, and New York Heart Association functional class were not. Concentrations of ANP and BNP were predictive of CSA as ROC demonstrated areas under the curve of 0.75 and 0.73, respectively.

CONCLUSIONS

Risk of CSA is related to severity of HF. ANP and BNP concentrations performed similarly for detection of CSA; low concentrations appear associated with low risk for CSA in men.

Interactions between sleep disordered breathing and atrial fibrillation in patients with hypertrophic cardiomyopathy

The aim of this study was to investigate whether patients with hypertrophic cardiomyopathy (HC) and sleep disordered breathing (SDB) have a higher prevalence of atrial fibrillation (AF) compared to patients with HC without SDB. HC is associated with a high prevalence of AF that contributes to increased morbidity and mortality. SDB is strongly associated with a higher incidence, prevalence, and recurrence of AF in patients without HC. Whether this association also applies to patients with HC is not known. Overnight oximetry was prospectively performed on 91 consecutive patients with echocardiographically confirmed HC. The presence or absence of AF in this population was correlated with the oximetric findings. SDB was associated with a higher prevalence of AF (40% vs 11%, p = 0.005). In addition, SDB was accompanied by significantly increased left atrial volume index (58 +/- 19 vs 42 +/- 13 ml/m(2), p = 0.0002). Increasing severity of SDB was correlated with higher AF prevalence and with increase in left atrial volume index. These associations remained significant even after accounting for potential confounders in a multivariate analysis. In conclusion, these findings suggest that the presence and severity of SDB may influence left atrial volume index and the prevalence of AF in patients with HC. SDB may therefore be an important and potentially modifiable cause of morbidity and mortality in this population.

Characteristics of sleep-disordered breathing in Japanese patients with type 2 diabetes mellitus

Sleep-disordered breathing (SDB), especially sleep apnea-hypopnea syndrome, is often observed in patients with type 2 diabetes mellitus; but there are only a few studies on SDB in Japanese diabetic subjects. We investigated the prevalence of SDB in diabetic patients; associations between severity of sleep apnea (SA) and clinical factors, visceral fat, and adiponectin; and associations between type of SA and clinical factors. In the present study, 40 Japanese diabetic patients underwent overnight cardiorespiratory monitoring, and night and morning measurements of serum adiponectin concentrations. Sleep apnea was detected in Japanese diabetic patients at a high prevalence (77.5%). The following variables were associated with SDB: age, body mass index, estimated visceral fat area, and nocturnal reduction in serum adiponectin concentrations. The prevalence of central sleep apnea (CSA, >or=5/h) was 32.3% among diabetic SDB patients. Diabetic SDB patients with CSA had higher hemoglobin, increased intima-media thickness, and higher plasma brain natriuretic peptide levels than those without CSA (<5/h). In conclusion, our study demonstrated a high prevalence of SDB in Japanese diabetic patients, which correlated with visceral fat area and adiponectin. A high frequency of CSA was noted in diabetic SDB patients, together with high hemoglobin, high brain natriuretic peptide, and increased intima-media thickness. The present results of prevalence of SDB may be relevant to the higher incidence of cardiovascular disease in diabetic patients, which need to be clarified in future studies.

Hypoxia, not the frequency of sleep apnea, induces acute hemodynamic stress in patients with chronic heart failure

OBJECTIVES

This study was conducted to evaluate whether brain (B-type) natriuretic peptide (BNP) changes during sleep are associated with the frequency and severity of apneic/hypopneic episodes, intermittent arousals, and hypoxia.

BACKGROUND

Sleep apnea is strongly associated with heart failure (HF) and could conceivably worsen HF through increased sympathetic activity, hemodynamic stress, hypoxemia, and oxidative stress. If apneic activity does cause acute stress in HF, it should increase BNP.

METHODS

Sixty-four HF patients with New York Heart Association functional class II and III HF and ejection fraction <40% underwent a baseline sleep study. Five patients with no sleep apnea and 12 with severe sleep apnea underwent repeat sleep studies, during which blood was collected every 20 min for the measurement of BNP. Patients with severe sleep apnea also underwent a third sleep study with frequent BNP measurements while they were administered oxygen. This provided 643 observations with which to relate apnea to BNP. The association of log BNP with each of 6 markers of apnea severity was evaluated with repeated measures regression models.

RESULTS

There was no relationship between BNP and the number of apneic/hypopneic episodes or the number of arousals. However, the burden of hypoxemia (the time spent with oxygen saturation <90%) significantly predicted BNP concentrations; each 10% increase in duration of hypoxemia increased BNP by 9.6% (95% confidence interval: 1.5% to 17.7%, p = 0.02).

CONCLUSIONS

Hypoxemia appears to be an important factor that underlies the impact of sleep abnormalities on hemodynamic stress in patients with HF. Prevention of hypoxia might be especially important for these patients.

[Usefulness of the N-terminal fraction of brain natriuretic peptide for deciding when to refer patients with sleep apnea-hypopnea syndrome to the cardiologist]

INTRODUCTION AND OBJECTIVE

When sleep apnea-hypopnea syndrome (SAHS) and cardiovascular disease occur concurrently, prognosis is affected. Echocardiography can detect structural cardiac abnormalities but using this technique in all patients would place a heavy burden on resources. The objective of this study was to investigate whether the N-terminal fraction of brain natriuretic peptide (NT-proBNP) can be used as a marker for silent heart disease.

PATIENTS AND METHODS

NT-proBNP concentration was measured in the 114 consecutive patients with SAHS who underwent echocardiography before starting treatment. Left and right ventricular systolic and diastolic function, as well as structural abnormalities, were studied. Correlations between NT-proBNP concentration and the abnormalities detected were investigated. A receiver operating characteristics (ROC) curve was plotted for NT-proBNP concentration and cardiac abnormalities.

RESULTS

Data for 98 patients were finally analyzed. NT-proBNP concentration was significantly correlated with ventricular septal thickness (r=0.63), posterior wall thickness (r=0.45), and left ventricular end-diastolic diameter (r=0.51) (P<.0001 for all correlations). The area under the ROC curve was significant (0.870; 95% confidence interval, 0.801-0.939; P<.0001). Assuming that specificity would be more useful for clinical practice, we calculated that NT-proBNP concentrations below 100 and 200 pg/mL could rule out structural abnormalities with a reliability of 90% and 100%, respectively.

CONCLUSIONS

NT-proBNP concentration was strongly correlated with echocardiographic abnormalities and so could be a useful tool for identifying patients who should be referred to the cardiologist.

Dynamic changes of left ventricular performance and left atrial volume induced by the mueller maneuver in healthy young adults and implications for obstructive sleep apnea, atrial fibrillation, and heart failure

Using the Mueller maneuver (MM) to simulate obstructive sleep apnea (OSA), our aim was to investigate acute changes in left-sided cardiac morphologic characteristics and function which might develop with apneas occurring during sleep. Strong evidence supports a relation between OSA and both atrial fibrillation and heart failure. However, acute effects of airway obstruction on cardiac structure and function have not been well defined. In addition, it is unclear how OSA might contribute to the development of atrial fibrillation and heart failure. Echocardiography was used in healthy young adults to measure various parameters of cardiac structure and function. Subjects were studied at baseline, during, and immediately after performance of the MM and after a 10-minute recovery. Continuous heart rate, blood pressure, and pulse oximetry measurements were made. During the MM, left atrial (LA) volume index markedly decreased. Left ventricular (LV) end-systolic dimension increased in association with a decrease in LV ejection fraction. On release of the maneuver, there was a compensatory increase in blood flow to the left side of the heart, with stroke volume, ejection fraction, and cardiac output exceeding baseline. After 10 minutes of recovery, all parameters returned to baseline. In conclusion, sudden imposition of severe negative intrathoracic pressure led to an abrupt decrease in LA volume and a decrease in LV systolic performance. These changes reflected an increase in LV afterload. Repeated swings in afterload burden and chamber volumes may have implications for the future development of atrial fibrillation and heart failure.

Natriuretic peptides in hormonal regulation of hypoxia responses

The possibility that natriuretic peptides' effects are important in hypoxia responses of vertebrates is reviewed. Both the transcription and release of natriuretic peptides are affected by oxygen tension. Furthermore, many of the effects observed in hypoxia, such as diuresis and a reduction of plasma volume, are also caused by treatment of the animal with natriuretic peptides. Also, several clinical observations about changes in natriuretic peptide levels in, e.g., sleep apnea and cyanotic congenital heart disease, are consistent with the idea that hypoxia is involved in the etiology of conditions, in which natriuretic peptide levels increase. Virtually all published information on the relationship between oxygen and natriuretic peptides is based on human studies. Because hypoxic conditions are more common in aquatic than terrestrial environments, future studies about the possible role of natriuretic peptides in hypoxia, as well as the role of hypoxia in the evolution of natriuretic peptides, including the different subtypes, should increasingly involve also aquatic organisms.

Effect of nasal continuous positive airway pressure in men on global left ventricular myocardial performance in patients with obstructive sleep apnea syndrome

The influence of obstructive sleep apnea syndrome (OSAS) on left ventricular function remains controversial. We examined the influence of OSAS on global left ventricular function using the myocardial performance index (Tei index) and plasma brain natriuretic peptide (BNP) level and investigated the effect of nasal continuous positive airway pressure (nCPAP) on these parameters. We obtained echocardiographic indexes including the Tei index and BNP concentrations from 27 patients with OSAS whose mean apnea-hypopnea index was 42.2+/-21.5 events/hour and who were undergoing nCPAP and from 22 control subjects. We defined global left ventricular dysfunction (GLVD) as a Tei index >or=0.50 and high BNP as >or=20 pg/ml. Compared with controls, the Tei index of patients with OSAS was significantly increased (p <0.01) and prevalence of GLVD was high (19%, p<0.05). The correlation between the Tei index and apnea-hypopnea index was significant (r=0.447, p<0.05). Although BNP levels were higher in patients with OSAS than in controls, the difference did not reach significance. BNP level was high in 37% of patients with OSAS and in only 9% of controls (p<0.05). The Tei index of patients with OSAS was significantly decreased after 1 month and 3 months of nCPAP (p<0.01), and prevalence of GLVD significantly decreased from 19% to 4% (p<0.05). In contrast, BNP significantly decreased at 3 months after nCPAP (p<0.05). In conclusion, patients with moderate to severe OSAS frequently have impaired global left ventricular myocardial performance, which can be reversed at the early stage after starting nCPAP.

Sleep disordered breathing in chronic heart failure

Heart failure is a growing problem, placing an increasing burden on public health resources and continuing to exert a high toll in mortality and morbidity. Sleep disordered breathing (SDB) is also a major public health problem and is associated with an increased risk of fatal and non-fatal cardiovascular events. Current evidence suggests SDB, particularly central SDB, is more prevalent in patients with chronic heart failure (CHF) than in the general population, but is under-diagnosed as SDB symptoms are less prevalent in CHF. This is further hampered by the absence of a simple and accurate screening tool and limited access to sleep facilities to diagnose SDB in the large numbers of patients with CHF. The presence of SDB in patients with CHF imposes increased haemodynamic burdens and results in autonomic abnormalities. Central SDB is an independent marker of worse prognosis, and evidence is increasing that obstructive SDB is also associated with higher mortality in patients with CHF. Optimal treatment of central SDB in these patients remains uncertain. While evidence of efficacy of positive pressure ventilation is stronger in obstructive SDB, improvement in survival for patients with both CHF and SDB awaits definitive trials. This paper summarizes our current understanding of the pathophysiology of SDB in CHF, and the cardiovascular consequences, and reviews the evidence for the beneficial effects of treatment of SDB in patients with CHF.

Obstructive sleep apnea, cardiovascular disease, and pulmonary hypertension

With the growing epidemic of obesity in an aging population, obstructive sleep apnea (OSA) is increasingly encountered in clinical practice. Given the acute cardiopulmonary stressors consequent to repetitive upper airway collapse, as well as evidence for cardiovascular homeostatic dysregulation in subjects with sleep apnea, there is ample biologic plausibility that OSA imparts increased cardiovascular risk, independent of comorbid disease. Indeed, observational studies have suggested strong associations with multiple disorders, such as systemic hypertension, heart failure, cardiac arrhythmias, and pulmonary hypertension. Further data in the form of longitudinal cohort studies and randomized controlled trials are accruing to add to the body of evidence. This review examines pathophysiologic mechanisms and explores current concepts regarding the impact of OSA and its treatment on selected clinical disease states.

NT-proBNP is not elevated in patients with obstructive sleep apnoea

BACKGROUND

N-terminal pro-brain natriuretic peptide (NT-ProBNP) has emerged as an important marker of cardiac stress and may reflect the severity of underlying cardiac dysfunction, which is thought to be associated with obstructive sleep apnoea syndrome (OSAS).

METHODS

This study evaluated the plasma concentration of NT-ProBNP in 60 consecutive patients (median age 55.7 years, median body mass index (BMI) 31.8) who were referred to a sleep laboratory with a suspicion of OSAS. Each subject underwent measurement of morning NT-ProBNP plasma levels, polysomnography and echocardiography. Patients were treated with nasal continuous or bilevel positive airway pressure ventilation (nCPAP/BIPAP) or without mechanical respiratory support, depending on clinical symptoms and results of polysomnography. Three months after treatment of OSAS 28 of the patients were reassessed for re-evaluation of NT-ProBNP and polysomnography.

RESULTS

Low or high levels of NT-proBNP were not associated with AHI and other sleep related indices (p>0.3). There was no correlation between NT-proBNP and AHI or other sleep related indices. In multiple regression analysis, NT-proBNP was significantly correlated with left ventricular ejection fraction, creatinine clearance and the presence of systemic arterial hypertension but not with AHI.

CONCLUSIONS

Our results show by a robust multiple regression analysis, that NT-pro BNP is not associated with OSAS and NT-pro BNP cannot be used as a sensitive marker for underlying cardiovascular abnormalities in patients with OSAS.

N-terminal pro-B-type natriuretic peptide and functional capacity in patients with obstructive sleep apnea

The obstructive sleep apnea syndrome (OSAS) is associated with cardiovascular abnormalities including left ventricular hypertrophy, left ventricular diastolic dysfunction, and endothelial dysfunction. The present study evaluated whether N-terminal pro-B-type natriuretic peptide (NT-proBNP) and peak oxygen consumption (peak VO(2)), both integral markers of cardiovascular function, are related to OSAS severity. In addition, we tested whether NT-proBNP levels depend on body composition in OSAS patients, similar to what has been reported in patients without OSAS. Eighty-nine patients with untreated OSAS underwent NT-proBNP measurement, dual X-ray absorptiometry, and cardiopulmonary exercise testing. In a representative subgroup (n = 32), transthoracic echocardiography was performed. The severity of OSAS was classified based on apnea-hypopnea index (AHI) values as mild (AHI 5-15 h(-1)), moderate (AHI 15-30 h(-1)), and severe (AHI >30 h(-1)). OSAS was mild in 19 (21%), moderate in 21 (24%), and severe in 49 (55%) patients. NT-proBNP levels did not differ among patients with mild [30 (10-57)], moderate [37 (14-55)], and severe [24 (13-49) pg/ml; p = 0.8] OSAS and were not related to body mass index (r = 0.07; p = 0.5), percent lean body mass (r = -0.17; p = 0.1), and percent fat mass (r = 0.18; p = 0.1). Percent predicted peak VO(2) was on average normal and did not differ among patients with mild (115 +/- 26), moderate (112 +/- 23), and severe OSAS (106 +/- 29%; p = 0.4). Body weight-indexed peak VO(2) did not differ among patients with mild (31.9 +/- 10.3), moderate (32.1 +/- 7.9), and severe OSAS (30.0 +/- 9.9 ml kg(-1) min(-1); p = 0.6) either. Lower NT-proBNP (beta = -0.2; p = 0.02) was independently but weakly associated with higher body weight-indexed peak VO(2). In the echocardiography subgroup, NT-proBNP was not significantly related to left ventricular mass index (r = 0.26; p = 0.2). In conclusion, NT-proBNP and peak VO(2) are not related to OSAS severity, and NT-proBNP poorly reflects left ventricular hypertrophy in OSAS. The lack of a relationship between NT-proBNP and OSAS severity is not due to a significant influence of body composition on NT-proBNP. There is an association between higher NT-proBNP and lower peak VO(2), indicating that NT-proBNP is a marker of cardiorespiratory fitness in patients with OSAS. However, the association is too weak to be clinically useful.

[Sleep apnea syndrome and heart failure]

More than half of all patients with stable heart failure are affected by sleep apnea syndrome. The mechanism of apnea may be either obstructive, by collapse of the upper airways, or central with nocturnal Cheyne-Stokes respiration. Changes in intrathoracic pressure, awakening and hypoxemia all lead to an increase in left ventricular afterload and to sympathetic activation, which can aggravate heart failure and prognosis. Treatment with positive pressure ventilation improves symptoms as well as cardiac function and prognosis. Sleep respiratory disorders are underdiagnosed and undertreated in patients with stable heart failure. To improve management of sleep apnea, patients with stable heart failure should be screened with small outpatient oximeters.

N-terminal pro-brain natriuretic peptide for detection of cardiovascular stress in patients with obstructive sleep apnea syndrome

Patients with obstructive sleep apnea syndrome (OSAS) have an elevated incidence of cardiovascular events that may be related to an increased ventricular load and hypoxemia caused by apneas and hypopneas. N-terminal pro-brain natriuretic peptide (NTproBNP) appears to be an excellent marker of myocardial stretch and could serve as an indicator of subclinical cardiac stress, thereby identifying a patient population at risk for cardiac effects from OSAS. Adult patients presenting with suspected OSAS and scheduled for nocturnal polysomnography were recruited. Patients with heart or renal failure or severe lung disease were excluded. NTproBNP was measured the evening before and the morning after sleep. Blood pressure (BP) was monitored intermittently throughout the night. Fifteen male and 15 female subjects with a mean +/- SD body mass index of 38.2 +/- 9.8 were studied. Mean Apnea-Hypopnea Index (AHI) was 38.4 +/- 26, with 17 subjects having severe OSAS (AHI > 30). No subject had a significant rise in BP. NTproBNP values overnight decreased in 19 patients and rose in 11 (mean change 3.8 +/- 33 pg mL(-1)), but only one patient had an abnormal morning value. Three patients had an abnormal NTproBNP value prior to sleep, but their levels decreased with sleep. No correlations were detected between the evening baseline or postsleep NTproBNP levels and OSAS. Monitoring pre- and postsleep NTproBNP levels revealed no association with the occurrence or degree of OSAS, making it unlikely that NTproBNP could serve as a marker of cardiac stress in OSAS patients with stable BP and without overt heart failure.

Overnight Change in Brain Natriuretic Peptide Levels in Children With Sleep-Disordered Breathing

STUDY OBJECTIVES

Obstructive sleep-disordered breathing is accompanied by episodic increases in left ventricle afterload due to large negative swings in intrathoracic pressure and repetitive surges in arterial pressure. Brain natriuretic peptide (BNP) is released by ventricular myocytes in response to pressure and volume overload. It was hypothesized that in children with snoring, overnight change in BNP levels is correlated with severity of disturbance in respiration.

DESIGN

Evening and morning plasma levels of BNP were measured in children with snoring referred for polysomnography.

SETTING

A sleep disorders laboratory in a university hospital.

PARTICIPANTS

Twenty-two children with apnea-hypopnea index (AHI) > or = 5/h (mean +/- SD age, 6.4 +/- 2.5 years), 60 children with AHI < 5/h (mean age, 7 +/- 2.9 years), and 27 control subjects without snoring (mean age, 7.8 +/- 3.7 years) were recruited.

MEASUREMENTS AND RESULTS

Overnight change in BNP (log-transformed ratio of morning-to-evening levels) was larger in children with AHI > or = 5/h, compared to those with AHI < 5/h or to control subjects (0.1 +/- 0.19 vs 0.01 +/- 0.14 vs - 0.06 +/- 0.18; p < 0.05). Children with AHI > or = 5/h had an odds ratio of 4.33 (95% confidence interval, 1.34 to 14) for change in peptide levels > 0.15 relatively to subjects with AHI < 5/h. AHI and oxygen saturation of hemoglobin nadir were significant predictors of overnight change in peptide levels.

CONCLUSIONS

In children with snoring, overnight increase in BNP levels is correlated with severity of disturbance in respiration during sleep, which may indicate presence of nocturnal cardiac strain.

Does obstructive sleep apnea increase hematocrit?

This study assessed the relationship between hematocrit levels and severity of obstructive sleep apnea (OSA) and examined how this relationship was affected by the degree of hypoxia as well as by possible confounding factors. Two-hundred sixty three subjects (189 men and 74 women) underwent nocturnal polysomnography with oximetry and had measurements of hematocrit, hemoglobin, white blood cell count, body mass index (BMI), blood pressure (BP), and 24-h urine norepinephrine (NE). Patients with severe OSA [respiratory disturbance index (RDI) >30] had significantly higher hematocrit values than patients with mild to moderate OSA or nonapneic controls (p < 0.01). However, only one patient had a hematocrit in the range of clinical polycythemia. Hematocrit levels were significantly correlated with BMI, BP, urinary NE, RDI, percent of time spent at oxygen saturation <90%, and with mean oxygen saturation. Multiple linear regression analysis revealed that mean oxygen saturation, RDI, and percent of time spent at oxygen saturation <90% were significant predictors of hematocrit level, even after controlling for gender, ethnicity, 24-h urine NE, BMI, and BP (p < 0.05). The severity of OSA is significantly associated with increased hematocrit, even after controlling for possible confounding variables. However, nocturnal hypoxemia in OSA does not usually lead to clinical polycythemia.

Inflammatory aspects of sleep apnea and their cardiovascular consequences

Obstructive sleep apnea (OSA) is a common medical condition that occurs in a considerable percentage of the population. Substantial evidence shows that patients with OSA have an increased incidence of hypertension compared with individuals without OSA, and that OSA is a risk factor for the development of hypertension. It is established that OSA may be implicated in stroke and transient ischemic attacks. OSA is associated with coronary heart disease, heart failure, and cardiac arrhythmias. Pulmonary hypertension may be associated with OSA, especially in patients with pre-existing pulmonary disease. Although the exact cause that links OSA with cardiovascular disease is unknown, there is evidence that OSA is associated with a group of proinflammatory and prothrombotic factors that have been identified as important in the development of atherosclerosis. OSA is associated with increased daytime and nocturnal sympathetic activity. Autonomic abnormalities seen in patients with OSA include increased resting heart rate, decreased R-R interval variability, and increased blood pressure variability. Both atherosclerosis and OSA are associated with endothelial dysfunction, increased C-reactive protein, interleukin 6, fibrinogen, plasminogen activator inhibitor, and reduced fibrinolytic activity. OSA has been associated with enhanced platelet activity and aggregation. Leukocyte adhesion and accumulation on endothelial cells are common in both OSA and atherosclerosis. Clinicians should be aware that OSA may be a risk factor for the development of cardiovascular disease.

NT-pro-BNP in obstructive sleep apnea syndrome is decreased by nasal continuous positive airway pressure

OBJECTIVE

The aim of this study was to evaluate the impact of obstructive sleep apnea syndrome (OSAS) on B-type natriuretic peptide (BNP) and to determine the effect of nasal continuous positive airway pressure (nCPAP) treatment on BNP levels.

BACKGROUND

Increased sympathetic activity, repetitive rises in blood pressure, and apnea-induced wall stress may contribute as a trigger to release BNP in OSAS. However, there is uncertainty about whether OSAS affects BNP and whether application of nasal continuous positive airway pressure (nCPAP) ventilation affects release of BNP.

PATIENTS AND METHODS

A prospective study in 69 consecutive patients with suspected sleep disordered breathing referred to our sleep laboratory was conducted. OSAS was confirmed in 26 normotensive and 34 hypertensive patients and ruled out in nine normotensive patients (controls) by polysomnography (PSG).

RESULTS

Baseline N-terminal fragment of BNP prohormone (NT-pro-BNP) did not differ significantly between OSAS patients (hypertensive: mean +/-SEM 60.8+/-9.9 pg/ml, normotensive: 43.2+/-6.8 pg/ml) and controls (36.5+/-8.5 pg/ml). Application of CPAP resulted in a significant decrease of NT-pro-BNP in hypertensive (60.8+/-9.9 pg/ml to 47.6+/-7.4 pg/ml, p=0.023) and normotensive OSAS (43.2+/-6.8 pg/ml to 29.6+/-5.3 pg/ml, p=0.0002). In contrast, controls showed no significant differences in NT-pro-BNP after a second PSG (36.5+/-8.5 pg/ml to 40.7+/-12.3 pg/ml, p=0.597).

CONCLUSIONS

Normotensive and hypertensive OSAS was not associated with a significant elevation of NT-pro-BNP. Application of nCPAP decreased NT-pro-BNP levels significantly in normotensive and, in particular, hypertensive OSAS. These findings may provide further evidence of the potential for nCPAP to improve cardiovascular comorbidity and co-mortality in OSAS and sleep disordered breathing, in general.

Heart failure and sleep apnoea: to sleep perchance to dream

Heart failure and sleep apnoea are major health problems with an increasingly recognized association; evidence suggests that sleep apnoea may play a role in the progression of heart failure. However, confounding factors such as obesity, hypertension and coronary heart disease make this relationship uncertain and an independent correlation remains unproven. Diagnosis of sleep apnoea is suboptimal, as it is often asymptomatic and polysomnography is expensive and time-consuming. A simple and reliable screening protocol is required. All heart failure patients should be considered to be at high risk of sleep apnoea, as this association might be linked to adverse outcome. Continuous positive airway pressure has shown some beneficial effects, but long-term outcome and improvement in survival remains to be demonstrated. Despite recent advances in the understanding of the complex relationship between heart failure and sleep apnoea, there are a number of areas requiring further investigation, which may have important implications for the management and prognosis of a significant number of patients.

B-type natriuretic peptide: Issues for the intensivist and pulmonologist

OBJECTIVE

B-type natriuretic peptide (BNP) and N-terminal pro-BNP (NT-proBNP), although promising as biomarkers for heart failure, are affected by multiple confounders. The purpose of this article is to review the literature on the utility of BNP and NT-proBNP as biomarkers, with a focus on their role in critical illness and pulmonary diseases.

DATA SOURCE

Published articles on BNP and NT-proBNP.

DATA ANALYSIS

Multiple disorders in the intensive care unit cause elevated BNP and NT-proBNP levels, including cardiac diseases, shock, pulmonary hypertension, acute respiratory distress syndrome, acute pulmonary embolism, chronic obstructive pulmonary disease, renal failure, and other conditions.

CONCLUSIONS

Intensivists and pulmonologists should understand that BNP and NT-proBNP levels might be raised to different degrees not only in heart failure but also in critical illness and various pulmonary diseases; in these situations, BNP and NT-proBNP may also serve as markers of severity and prognosis.

Obstructive Sleep Apnoea, Congestive Heart Failure and Cardiovascular Disease

Sleep disordered breathing is a common condition within the general community. Mostly this is represented by obstructive sleep apnoea (OSA), a condition characterized by repetitive occlusions of the upper airway due to retro-positioning of the tongue and pharyngeal collapse during sleep. This article covers the key evidence relating OSA to both causation and progression of congestive heart failure and cardiovascular disease including hypertension. The results of recent studies are summarized, and the authors conclude that whilst progress has been made, there remain many gaps in our knowledge in relation to the contribution to the burden of cardiac disease produced by associated conditions such as OSA. Larger studies with important primary endpoints will be required to demonstrate the merit of screening and treating this disorder.