Diurnal changes and levels of fibrin generation are not altered by continuous positive airway pressure (CPAP) in obstructive sleep apnoea (OSA)

Association of Global Coagulation Profiles With Cardiovascular Risk Factors and Atherosclerosis: A Sex Disaggregated Analysis From the BioHEART-CT Study

Background

Although the association between dysregulated coagulation and atherosclerosis is well recognized, individual assays have been of minimal value in understanding disease susceptibility. Here we investigated the association of global coagulation profiles with coronary artery disease with consideration of sex differences.

Methods and Results

The study included patients from the BioHEART‐CT (The BioHEART Study: Assessing Patients With Suspected Cardiovascular Disease for New Disease Markers and Risk Factors) biobank who had computed tomography coronary angiograms scored for coronary artery calcium score (CACS) and Gensini score. The cohort included 206 adult patients who were referred for clinically indicated computed tomography coronary angiography and had a median of 2 major cardiac risk factors; 50% were women and the average age was 62.6 years (±9.9 years). The overall hemostatic potential (OHP) and calibrated automated thrombography generation assays were performed on platelet‐poor plasma. CACS and Gensini score in men were significantly correlated in bivariate analysis with measures from the OHP assay, and regression models predicting disease severity by CACS or Gensini score were improved by adding the OHP assay variables in men but not in women. The calibrated automated thrombography generation assay demonstrated a more hypercoagulable profile in women than in men. The OHP assay showed hypercoagulable profiles in women with hyperlipidemia and men with obesity.

Conclusions

The OHP assay identified hypercoagulable profiles associated with different risk factors for each sex and was associated with CACS and Gensini score severity in men, emphasizing the associations between increased fibrin generation and reduced fibrinolysis with cardiac risk factors and early atherosclerosis.

Registration Information

www.anzctr.org.au. Identifier: ACTRN12618001322224.

The role of sham continuous positive airway pressure as a placebo in controlled trials: Best Apnea Interventions for Research Trial

STUDY OBJECTIVES

The main objective of this study was to evaluate the role of sham continuous positive airway pressure (CPAP) compared to conservative medical therapy (CMT) as a control arm in the Best Apnea Interventions for Research (BestAIR) study by assessing differences in subjectively and objectively measured outcomes, adverse events, adherence, and retention rates.

METHODS

BestAIR is a clinical trial aimed to identify important design features for future randomized controlled trials of CPAP. Participants with obstructive sleep apnea were randomized to one of four groups; two control arms (CMT, sham-CPAP) and two active CPAP arms (with and without behavioral interventions). Blood pressure and health-related quality of life outcomes were assessed at baseline, 6 and 12 months. Study outcomes, retention, and adverse event rates were compared between the two control arms. Sham-CPAP adherence and self-efficacy were also compared to active-CPAP adherence (without behavioral intervention).

RESULTS

Our sample included 86 individuals in the control arms and 42 participants in the active-CPAP arm. There were no differences in longitudinal profiles in blood pressure, health-related quality of life outcomes, dropout rates, or adverse events in sham-CPAP group compared to CMT-only group (all ps > 0.05); standardized differences were generally small and with inconsistent directionality across measurements. When compared to active-CPAP, sham-CPAP was associated with 93 fewer minutes/night of usage over 12 months (p = 0.007) and lower outcome expectations (p < 0.05).

CONCLUSION

We observed no evidence of differences in objectively or subjectively measured outcomes with the use of sham-CPAP compared to CMT group. The lower adherence on sham-CPAP and poorer self-efficacy compared to active-CPAP may suggest differences in perceived benefit.

REGISTRATION

NCT01261390 Best Apnea Interventions for Research (BestAIR) www.clinicaltrials.gov.

Obstructive sleep apnoea and venous thromboembolism: pathophysiological links and clinical implications

Obstructive sleep apnoea (OSA) and pulmonary embolism (PE) remain major health issues worldwide. Data from pathophysiological studies suggest that both intermittent hypoxia and sleep fragmentation are associated with increased blood coagulability, endothelial dysfunction and venous stasis. There is growing evidence that OSA is potentially prevalent in and a risk factor for PE. Conversely, patients with acute PE have two to four times greater risk of moderate-to-severe OSA. The role of continuous positive airway pressure (CPAP) treatment in improving clinically meaningful outcomes in PE patients remains unclear, although some authors have suggested that CPAP could improve the hypercoagulability state and normalise circadian alterations in some of the coagulation molecules, as observed in patients with OSA. Emerging research highlights the complex interdependent relationships between OSA and PE, emphasising the need for rigorous, well-powered trials that address the impact of OSA and its treatment on the prevention and management of PE. Undoubtedly, these will require closer collaboration between the sleep medicine and clinical/venous thromboembolism communities.

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

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

Repercusiones cardiovasculares del síndrome de apnea-hipopnea obstructiva del sueño (SAHOS)

En la población de sujetos con síndrome de apnea-hipopnea obstructiva del sueño se describen entidades clínicas cardiovasculares asociadas con esta entidad y que afectan su curso y pronóstico. Dentro de estas se encuentran hipertensión arterial, arritmias, enfermedad coronaria, insuficiencia cardíaca, hipertensión pulmonar y tromboembolismo venoso. Del mismo modo, se describen los mecanismos fisiopatológicos de estas asociaciones, su prevalencia e impacto. Dado que afectan el curso de la enfermedad y, por tanto, la severidad de la misma, estas entidades juegan un papel muy importante en la toma de decisiones al momento de ofrecer el mejor manejo en cada caso, el cual debe ser abordado de forma multidisciplinaria.

The Overall Hemostatic Potential (OHP) Assay

The principle of the overall hemostatic potential (OHP) assay is the generation of a fibrin time curve by optical density readings, which represent the balance between fibrin generation, triggered by thrombin or tissue factor, and fibrinolysis, triggered by tissue plasminogen activator (tPA). OHP measures the integrated effect of procoagulant, anticoagulant, and fibrinolytic factors, and OHP assay parameters provide a means of quantifying both the coagulation and fibrinolytic potential of platelet poor plasma. In particular, the OHP assay can be used to evaluate hypercoagulable states and abnormalities of fibrinolysis which are not well defined by assays which are routinely available in the coagulation laboratory. OHP is a technically simple assay, with potential for application in the routine laboratory at minimal cost.

Altered clot microstructure detected in obstructive sleep apnoea hypopnoea syndrome

Abnormal clot microstructure plays a pivotal role in the pathophysiology of thromboembolic diseases. Assessing the viscoelastic properties of clot microstructure using novel parameters, Time to Gel Point (T_GP), Fractal Dimension (d_f) and clot elasticity (G׳_GP) could explain the increased cardiovascular and thromboembolic events in patients with Obstructive Sleep Apnoea Hypopnea Syndrome (OSAHS). We wanted to compare T_GP, d_f, and G׳_GP and their diurnal variation in OSAHS and symptomatic comparators. thirty six patients attending a sleep disturbed breathing clinic with symptoms of OSAHS were recruited. T_GP, d_f and G׳_GP were measured alongside standard coagulation screening, thrombin generation assays, and platelet aggregometry at 16:00 h and immediately after an in-patient sleep study at 07:30 h. OSAHS group had significantly lower afternoon d_f than comparators (1.705±0.033 vs. 1.731±0.031, p<0.05). d_f showed diurnal variation and only in the OSAHS group, being significantly lower in the afternoon than morning (p<0.05). Diurnal changes in d_f correlated with 4% DR, even after controlling for BMI (r=0.37, p=0.02). The lower d_f in the afternoon in OSAHS suggests a partial compensatory change that may make up for other pro-clotting abnormalities/hypertension during the night. The change to the thrombotic tendency in the afternoon is biggest in severe OSAHS. d_f Shows promise as a new microstructural indicator for abnormal haemostasis in OSAHS.

Three-year changes of prothrombotic factors in a cohort of South Africans with a high clinical suspicion of obstructive sleep apnea

A hypercoagulable state might be one important mechanism linking obstructive sleep apnea (OSA) with incident myocardial infarction and stroke. However, previous studies on prothrombotic factors in OSA are not uniform and cross-sectional. We longitudinally studied prothrombotic factors in relation to OSA risk, adjusting for baseline levels of prothrombotic factors, demographics, metabolic parameters, aspirin use, and life style factors. The Berlin Questionnaire and/or neck circumference were used to define high OSA risk in 329 South African teachers (48.0% male, 44.6% black) at baseline and at three-year follow-up. Von Willebrand factor (VWF), fibrinogen, D-dimer, plasminogen activator inhibitor-1, clot lysis time (CLT), and soluble urokinase-type plasminogen activator receptor (suPAR) were measured in plasma. At baseline 35.7% of participants had a high risk of OSA. At follow-up, persistently high OSA risk, persistently low OSA risk, OSA risk remission, and new-onset OSA risk were present in 26.1%, 53.2%, 9.4%, and 11.3% of participants, respectively. New-onset OSA risk was associated with a significant and longitudinal increase in VWF, fibrinogen, CLT, and suPAR relative to persistently low OSA risk; in VWF, fibrinogen, and suPAR relative to remitted OSA risk; and in VWF relative to persistently high OSA risk. Persistently high OSA risk was associated with an increase in CLT and suPAR relative to persistently low OSA risk and in D-dimer relative to remitted OSA risk. Remitted OSA risk was associated with D-dimer decrease relative to persistently low OSA risk. In OSA, hypercoagulability is a dynamic process with a most prominent three-year increase in individuals with new-onset OSA risk.

High D-dimer levels after stopping anticoagulants in pulmonary embolism with sleep apnoea

Obstructive sleep apnoea is a risk factor for pulmonary embolism. Elevated D-dimer levels and other biomarkers are associated with recurrent pulmonary embolism. The objectives were to compare the frequency of elevated D-dimer levels (>500 ng·mL−1) and further coagulation biomarkers after oral anticoagulation withdrawal in pulmonary embolism patients, with and without obstructive sleep apnoea, including two control groups without pulmonary embolism.

We performed home respiratory polygraphy. We also measured basic biochemical profile and haemogram, and coagulation biomarkers (D-dimer, prothrombin fragment 1+2, thrombin-antithrombin complex, plasminogen activator inhibitor 1, and soluble P-selectin).

64 (74.4%) of the pulmonary embolism cases and 41 (46.11%) of the controls without pulmonary embolism had obstructive sleep apnoea. Plasmatic D-dimer was higher in PE patients with OSA than in those without obstructive sleep apnoea. D-dimer levels were significantly correlated with apnoea–hypopnoea index, and nocturnal hypoxia. There were more patients with high D-dimer after stopping anticoagulants in those with pulmonary embolism and obstructive sleep apnoea compared with PE without obstructive sleep apnoea (35.4% versus 19.0%, p=0.003). Apnoea–hypopnoea index was independently associated with high D-dimer.

Pulmonary embolism patients with obstructive sleep apnoea had higher rates of elevated D-dimer levels after anticoagulation discontinuation for pulmonary embolism than in patients without obstructive sleep apnoea and, therefore, higher procoagulant state that might increase the risk of pulmonary embolism recurrence.

Clinical effectiveness and cost-effectiveness results from the randomised controlled Trial of Oral Mandibular Advancement Devices for Obstructive sleep apnoea-hypopnoea (TOMADO) and long-term economic analysis of oral devices and continuous positive airway pressure

BACKGROUND

Obstructive sleep apnoea-hypopnoea (OSAH) causes excessive daytime sleepiness (EDS), impairs quality of life (QoL) and increases cardiovascular disease and road traffic accident risks. Continuous positive airway pressure (CPAP) treatment is clinically effective but undermined by intolerance, and its cost-effectiveness is borderline in milder cases. Mandibular advancement devices (MADs) are another option, but evidence is lacking regarding their clinical effectiveness and cost-effectiveness in milder disease.

OBJECTIVES

(1) Conduct a randomised controlled trial (RCT) examining the clinical effectiveness and cost-effectiveness of MADs against no treatment in mild to moderate OSAH. (2) Update systematic reviews and an existing health economic decision model with data from the Trial of Oral Mandibular Advancement Devices for Obstructive sleep apnoea-hypopnoea (TOMADO) and newly published results to better inform long-term clinical effectiveness and cost-effectiveness of MADs and CPAP in mild to moderate OSAH.

TOMADO

A crossover RCT comparing clinical effectiveness and cost-effectiveness of three MADs: self-moulded [SleepPro 1™ (SP1); Meditas Ltd, Winchester, UK]; semibespoke [SleepPro 2™ (SP2); Meditas Ltd, Winchester, UK]; and fully bespoke [bespoke MAD (bMAD); NHS Oral-Maxillofacial Laboratory, Addenbrooke's Hospital, Cambridge, UK] against no treatment, in 90 adults with mild to moderate OSAH. All devices improved primary outcome [apnoea-hypopnoea index (AHI)] compared with no treatment: relative risk 0.74 [95% confidence interval (CI) 0.62 to 0.89] for SP1; relative risk 0.67 (95% CI 0.59 to 0.76) for SP2; and relative risk 0.64 (95% CI 0.55 to 0.76) for bMAD (p < 0.001). Differences between MADs were not significant. Sleepiness [as measured by the Epworth Sleepiness Scale (ESS)] was scored 1.51 [95% CI 0.73 to 2.29 (SP1)] to 2.37 [95% CI 1.53 to 3.22 (bMAD)] lower than no treatment (p < 0.001), with SP2 and bMAD significantly better than SP1. All MADs improved disease-specific QoL. Compliance was lower for SP1, which was unpopular at trial exit. At 4 weeks, all devices were cost-effective at £20,000/quality-adjusted life-year (QALY), with SP2 the best value below £39,800/QALY.

META-ANALYSIS

A MEDLINE, EMBASE and Science Citation Index search updating two existing systematic reviews (one from November 2006 and the other from June 2008) to August 2013 identified 77 RCTs in adult OSAH patients comparing MAD with conservative management (CM), MADs with CPAP or CPAP with CM. MADs and CPAP significantly improved AHI [MAD -9.3/hour (p < 0.001); CPAP -25.4/hour (p < 0.001)]. Effect difference between CPAP and MADs was 7.0/hour (p < 0.001), favouring CPAP. No trials compared CPAP with MADs in mild OSAH. MAD and CPAP reduced the ESS score similarly [MAD 1.6 (p < 0.001); CPAP 1.6 (p < 0.001)].

LONG-TERM COST-EFFECTIVENESS

An existing model assessed lifetime cost-utility of MAD and CPAP in mild to moderate OSAH, using the revised meta-analysis to update input values. The TOMADO provided utility estimates, mapping ESS score to European Quality of Life-5 Dimensions three-level version for device cost-utility. Using SP2 as the standard device, MADs produced higher mean costs and mean QALYs than CM [incremental cost-effectiveness ratio (ICER) £6687/QALY]. From a willingness to pay (WTP) of £15,367/QALY, CPAP is cost-effective, although the likelihood of MADs (p = 0.48) and CPAP (p = 0.49) being cost-effective is very similar. Both were better than CM, but there was much uncertainty in the choice between CPAP and MAD (at a WTP £20,000/QALY, the probability of being the most cost-effective was 47% for MAD and 52% for CPAP). When SP2 lifespan increased to 18 months, the ICER for CPAP compared with MAD became £44,066. The ICER for SP1 compared with CM was £1552, and for bMAD compared with CM the ICER was £13,836. The ICER for CPAP compared with SP1 was £89,182, but CPAP produced lower mean costs and higher mean QALYs than bMAD. Differential compliance rates for CPAP reduces cost-effectiveness so MADs become less costly and more clinically effective with CPAP compliance 90% of SP2.

CONCLUSIONS

Mandibular advancement devices are clinically effective and cost-effective in mild to moderate OSAH. A semi-bespoke MAD is the appropriate first choice in most patients in the short term. Future work should explore whether or not adjustable MADs give additional clinical and cost benefits. Further data on longer-term cardiovascular risk and its risk factors would reduce uncertainty in the health economic model and improve precision of effectiveness estimates.

TRIAL REGISTRATION

This trial is registered as ISRCTN02309506.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 18, No. 67. See the NIHR Journals Library website for further project information.

Sleep apnea and venous thromboembolism. A systematic review

Recent evidence suggests that obstructive sleep apnea is a significant and independent risk factor for a number of cardiovascular disorders. Since the association between obstructive sleep apnea and cardiovascular disease is mediated by endothelial dysfunction, hypercoagulability and platelet abnormalities, we sought to investigate whether sleep apnea may also be considered a risk factor for venous thromboembolism (VTE). We carried out an electronic search in Medline and Scopus using the keywords "apnea" OR "apnoea" AND "venous thromboembolism" OR "deep vein thrombosis" OR "pulmonary embolism" in "Title/Abstract/Keywords", with no language or date restriction. Fifteen studies (8 case-control, 4 retrospective observational, 2 prospective case-control and 1 prospective observational) were finally selected for this systematic review. In all studies except one (14/15; 93 %), obstructive sleep apnea was found to be an independent risk factor for VTE, either deep-vein thrombosis (DVT) or pulmonary embolism (PE). In the two prospective case-control studies the risk of DVT or PE was found to be two- to three-fold higher in patients with obstructive sleep apnea than in those without. In conclusion, the current epidemiological evidence supports the hypothesis that obstructive sleep apnea may be an independent risk factor for VTE.

Impact of obstructive sleep apnea treatment by continuous positive airway pressure on cardiometabolic biomarkers: a systematic review from sham CPAP randomized controlled trials

Reducing cardiometabolic risk may represent an important target for effective obstructive sleep apnea (OSA) treatment. The impact of continuous positive airway pressure (CPAP), the first line therapy of OSA, on metabolic or inflammatory markers is still debated. A systematic literature search using several databases was performed. We provide a systematic analysis of randomized studies comparing therapeutic versus sham CPAP intervention and also include studies using a CPAP withdrawal design. We addressed the impact of CPAP on the following cardiometabolic biomarkers: 1) plasma and urine catecholamines and their metabolites that reflect sympathetic activity; 2) insulin resistance and lipid metabolism biomarkers; 3) oxidative stress, systemic and vascular inflammation biomarkers; 4) liver enzymes highlighting the association between OSA and nonalcoholic fatty liver disease (NAFLD); 5) coagulation biomarkers. The impact of CPAP on sympathetic activity is robust across studies and occurs rapidly. In contrast to sympathetic activity, the well-designed studies included in this review failed to demonstrate that CPAP alters metabolic or inflammatory markers in OSA. CPAP did not change glucose, lipids, insulin resistance levels or the ratio of patients with metabolic syndrome. In unselected OSA patients, it is not realistic to expect a clinically relevant decrease in cardiometabolic biomarkers with CPAP therapy.