Rationale and design of the SERVE-HF study: treatment of sleep-disordered breathing with predominant central sleep apnoea with adaptive servo-ventilation in patients with chronic heart failure

Baclofen-Associated Onset of Central Sleep Apnea in Alcohol Use Disorder: A Case Report

A 61-year-old patient with alcohol use disorder (AUD) was referred for suspicion of sleep apnea syndrome (SAS). He had incurred three road accidents attributed to sleepiness over the previous year, shortly after initiation of high-dose (100 mg b.i.d.) treatment with baclofen, a molecule increasingly used in the management of AUD. Polysomnography revealed a severe central SAS (CSAS) with an apnea-hypopnea index (AHI) of 81.6/h. Baclofen was suggested as a possible cause of the CSAS, and after its withdrawal, a second polysomnography was done, showing the disappearance of the central apneas and a shift to severe obstructive SAS (AHI 43.9/h), for which a positive airway pressure (CPAP) treatment was initiated. A third polysomnography was performed under CPAP after reintroduction of baclofen (50 mg b.i.d.) by the patient, showing reappearance of the CSAS (AHI 42.1/h). This case report illustrates the deleterious effect of baclofen on breathing physiology during sleep. Since it is typically prescribed off label at high doses to a population of patients potentially using other substances that inhibit the ventilatory drive, this possible adverse effect is a major concern. When considering the use of baclofen in patients with AUD, the potential for sleep-disordered breathing should be weighed and carefully monitored.

New developments in the use of positive airway pressure for obstructive sleep apnea

Obstructive sleep apnea (OSA) is a disorder which afflicts a large number of individuals around the world. OSA causes sleepiness and is a major cardiovascular risk factor. Since its inception in the early 1980's, continuous positive airway pressure (CPAP) has emerged as the major treatment of OSA, and it has been shown to improve sleepiness, hypertension, and a number of cardiovascular indices. Despite its successes, adherence with treatment remains a major limitation. Herein we will review the evidence behind the use of positive airway pressure (PAP) therapy, its various modes, and the methods employed to improve adherence. We will also discuss the future of PAP therapy in OSA and personalization of care.

Adaptive Servo-Ventilation for Central Sleep Apnea in Systolic Heart Failure

BACKGROUND

Central sleep apnea is associated with poor prognosis and death in patients with heart failure. Adaptive servo-ventilation is a therapy that uses a noninvasive ventilator to treat central sleep apnea by delivering servo-controlled inspiratory pressure support on top of expiratory positive airway pressure. We investigated the effects of adaptive servo-ventilation in patients who had heart failure with reduced ejection fraction and predominantly central sleep apnea.

METHODS

We randomly assigned 1325 patients with a left ventricular ejection fraction of 45% or less, an apnea-hypopnea index (AHI) of 15 or more events (occurrences of apnea or hypopnea) per hour, and a predominance of central events to receive guideline-based medical treatment with adaptive servo-ventilation or guideline-based medical treatment alone (control). The primary end point in the time-to-event analysis was the first event of death from any cause, lifesaving cardiovascular intervention (cardiac transplantation, implantation of a ventricular assist device, resuscitation after sudden cardiac arrest, or appropriate lifesaving shock), or unplanned hospitalization for worsening heart failure.

RESULTS

In the adaptive servo-ventilation group, the mean AHI at 12 months was 6.6 events per hour. The incidence of the primary end point did not differ significantly between the adaptive servo-ventilation group and the control group (54.1% and 50.8%, respectively; hazard ratio, 1.13; 95% confidence interval [CI], 0.97 to 1.31; P=0.10). All-cause mortality and cardiovascular mortality were significantly higher in the adaptive servo-ventilation group than in the control group (hazard ratio for death from any cause, 1.28; 95% CI, 1.06 to 1.55; P=0.01; and hazard ratio for cardiovascular death, 1.34; 95% CI, 1.09 to 1.65; P=0.006).

CONCLUSIONS

Adaptive servo-ventilation had no significant effect on the primary end point in patients who had heart failure with reduced ejection fraction and predominantly central sleep apnea, but all-cause and cardiovascular mortality were both increased with this therapy. (Funded by ResMed and others; SERVE-HF ClinicalTrials.gov number, NCT00733343.).

Adaptive servo-ventilation therapy of central sleep apnoea and its effect on sleep quality

OBJECTIVES

Poor sleep quality is common in patients with chronic heart failure (CHF). This study tested the hypothesis that adaptive servo-ventilation (ASV) therapy in CHF patients whose central sleep apnoea (CSA) was not suppressed by continuous positive airway pressure (CPAP) (CPAP-non-responders) would improve sleep quality compared to CPAP-responders receiving ongoing CPAP therapy.

METHODS

Eighty-two patients with CHF (65 ± 9 years, left ventricular ejection fraction 35 ± 16 %) and CSA [apnoea-hypopnoea index (AHI) ≥15/h] were retrospectively studied. Within an average of 47 days, patients were reevaluated on CPAP therapy and stratified according to their suppression of CSA: 34 were CPAP-non-responders switched to ASV therapy the following day and 48 were CPAP-responders who continued on CPAP therapy. Polysomnographic parameters were assessed in the diagnostic night and on the last night of PAP therapy (CPAP or ASV) before the patient was discharged with the final pressure settings.

RESULTS

Compared with the CPAP group, the ASV group had significantly greater reductions from baseline in AHI (-37 ± 15/h vs -28 ± 18/h, p = 0.02), arousal index (-12.7 ± 13.6/h vs -6.8 ± 12.5/h, p = 0.04) and sleep stage N1 (-9 ± 14 % vs -2 ± 12 %, p = 0.03). In addition, the ASV group gained significantly more rapid eye movement (REM) sleep compared with the CPAP group (+5 ± 9 % vs +1 ± 9 %, p = 0.02).

CONCLUSIONS

CPAP therapy is effective in reducing AHI in a significant proportion of CHF patients with reduced ejection fraction and CSA. Treatment of CSA with ASV in CHF patients reduces sleep fragmentation and improves sleep structure to a significantly greater extent than changes seen in responders to CPAP therapy.

Heterogenous haemodynamic effects of adaptive servoventilation therapy in sleeping patients with heart failure and Cheyne-Stokes respiration compared to healthy volunteers

This study investigated the haemodynamic effects of adaptive servoventilation (ASV) in heart failure (HF) patients with Cheyne-Stokes respiration (CSR) versus healthy controls. Twenty-seven HF patients with CSR and 15 volunteers were ventilated for 1 h using a new ASV device (PaceWave™). Haemodynamics were continuously and non-invasively recorded at baseline, during ASV and after ventilation. Prior to the actual study, a small validation study was performed to validate non-invasive measurement of Stroke volume index (SVI). Non-invasive measurement of SVI showed a marginal overall difference of -0.03 ± 0.41 L/min/m(2) compared to the current gold standard (Thermodilution-based measurement). Stroke volume index (SVI) increased during ASV in HF patients (29.7 ± 5 to 30.4 ± 6 to 28.7 ± 5 mL/m(2), p < 0.05) and decreased slightly in volunteers (50.7 ± 12 to 48.6 ± 11 to 47.9 ± 12 mL/m(2)). Simultaneously, 1 h of ASV was associated with a trend towards an increase in parasympathetic nervous activity (PNA) in HF patients and a trend towards an increase in sympathetic nervous activity (SNA) in healthy volunteers. Blood pressure (BP) and total peripheral resistance response increased significantly in both groups, despite marked inter-individual variation. Effects were independent of vigilance. Predictors of increased SVI during ASV in HF patients included preserved right ventricular function, normal resting BP, non-ischaemic HF aetiology, mitral regurgitation and increased left ventricular filling pressures. This study confirms favourable haemodynamic effects of ASV in HF patients with CSR presenting with mitral regurgitation and/or increased left ventricular filling pressures, but also identified a number of new predictors. This might be mediated by a shift towards more parasympathetic nervous activity in those patients.

Heart failure: not a single organ disease but a multisystem syndrome

Heart failure is not simply a single organ disease; rather it is a complex multi-system clinical syndrome, with impairment of endocrine, haematological, musculoskeletal, renal, respiratory and vascular systems, which influence morbidity and mortality.

Prevalence and Impact of Sleep Disordered Breathing in Patients with Severe Aortic Stenosis

BACKGROUND

Unlike the well-established association between sleep disordered breathing (SDB) and chronic heart failure, the relationship between SDB and severe aortic stenosis (AS) is not well investigated. Given the increasing prevalence of AS, and the improving prognosis of high risk AS patients attributable to transcatheter aortic valve implantation (TAVI), the prevalence and impact of SDB needs to be better understood.

METHODS AND RESULTS

In this study, 140 patients with severe AS underwent polygraphy prior to TAVI. Clinical and hemodynamic parameters were recorded. Patients were followed for 573±405 days. We found that 99/140 patients (71%) had SDB with a mean apnoea-hypopnoea-index of 24±17/h. SDB was mild in 27%, moderate in 23% and severe in 21% of patients. In addition, 35 patients (25%) had obstructive sleep apnoea (OSA), whereas 64 patients (46%) had central sleep apnoea (CSA). Patients with OSA had predominantly mild SDB (20/38 pts.), and patients with CSA mostly had severe SDB (24/29 pts.). The prevalence and distribution of OSA and CSA were independent of left ventricular function. Overall, 1 and 2 year survival rates (74% and 71%, resp.) did not differ significantly between patients without SDB or those with OSA and CSA (p=0.81).

CONCLUSIONS

SDB, with a preponderance of CSA, was found to be highly prevalent in patients with high-grade AS scheduled for TAVI. SDB prevalence was independent of left ventricular function. Mortality after TAVI was not influenced by the type or severity of SDB.

Cheyne-Stokes respiration during sleep: mechanisms and potential interventions

Cheyne-Stokes respiration is characterized by a typical waxing and waning pattern in breathing amplitude, interspersed with central apnoeas or hypopnoeas. This article reviews current knowledge regarding Cheyne-Stokes respiration with a particular emphasis on the mechanisms and latest methods of intervention.

Respiratory effects of adaptive servoventilation therapy in patients with heart failure and Cheyne-Stokes respiration compared to healthy volunteers

BACKGROUND

Nocturnal adaptive servoventilation (ASV) therapy is now frequently used to treat Cheyne-Stokes respiration (CSR), which is highly prevalent in patients with moderate-to-severe heart failure (HF) and characterized by periodical breathing (hyperventilation).

OBJECTIVES

This study analyzed and compared the acute effects of a novel ASV device on carbon dioxide pressure (pCO2) and oxygen saturation (SaO2) in HF patients with CSR and healthy volunteers. The influence of being asleep or awake on the ASV algorithm was also determined.

METHODS

All subjects underwent ASV (PaceWave™, ResMed) for 1 h. Transcutaneous pCO2 (PtcCO2) and SaO2 were assessed transcutaneously, while wakefulness was analyzed using EEG recordings. Assessments were made 30 min before and after ASV, and during 1 h of ASV.

RESULTS

Twenty HF patients (19 male; age 79 ± 12 years) and 15 volunteers (13 male, age 25 ± 4 years) were included. When awake, ASV was associated with a trend towards a decrease in PtcCO2 and an increase in SaO2 versus baseline in HF patients (34.4 ± 3.2 to 33.7 ± 3.8 mm Hg and 93.8 ± 2.6 to 94.9 ± 2.6%, respectively) and volunteers (39.5 ± 3.0 to 38.2 ± 3.8 mm Hg and 96.9 ± 1.3 to 97.8 ± 0.9%). While asleep during ASV, PtcCO2 increased to 36.3 ± 3.8 mm Hg and SaO2 decreased to 93.8 ± 2.6% in HF patients, with similar changes in volunteers (PtcCO2 41.7 ± 3.0 mm Hg, SaO2 97.1 ± 1.2). All comparisons were statistically significant (p ≤ 0.05, except the PtcCO2 decrease in both groups when awake).

CONCLUSIONS

ASV therapy might result in hyperventilation when subjects are awake, but while asleep, PtcCO2 increased to mid-normal values, effects that would be favorable in HF patients with CSR.

Sleep-disordered Breathing in Heart Failure - Current State of the Art

Sleep-disordered breathing (SDB), either obstructive sleep apnoea (OSA) or central sleep apnoea (CSA)/Cheyne-Stokes respiration (CSR) and often a combination of the two, is highly prevalent in patients with heart failure (HF), is associated with reduced functional capacity and quality of life, and has a negative prognostic impact. European HF guidelines identify that sleep apnoea is of concern in patients with HF. Continuous positive airway pressure is the treatment of choice for OSA, and adaptive servoventilation (ASV) appears to be the most consistently effective therapy for CSA/CSR while also being able to treat concomitant obstructive events. There is a growing body of evidence that treating SDB in patients with HF, particularly using ASV for CSA/CSR, improves functional outcomes such as HF symptoms, cardiac function, cardiac disease markers, exercise tolerance and quality of life. However, conflicting results have been reported on 'hard' outcomes such as mortality and healthcare utilisation, and the influence of effectively treating SDB, including CSA/CSR, remains to be determined in randomised clinical trials. Two such trials (SERVE-HF and ADVENT-HF) in chronic stable HF and another in post-acute decompensated HF (CAT-HF) are currently underway.

Risk factors. Sleep apnoea, atrial fibrillation, and heart failure--quo vadis?

Strong associations exist between sleep disordered breathing (SDB) and both atrial fibrillation (AF) and heart failure (HF). Burgeoning epidemics of obesity, SDB, AF, and HF make these conditions priorities for health-care policymakers. Two observational studies now suggest outcome benefits from screening and treating for SDB in AF and HF.

Underdiagnosis of Obstructive Sleep Apnoea in Peripheral Arterial Disease

Background: Obstructive sleep apnoea (OSA) has interdependently been related to the onset and progression of a large portion of atherosclerotic cardiovascular disorders. In due consideration of OSA-mediated endothelial dysfunction, its impact on peripheral artery disease is conceivable, but undefined. Objectives: The aim of this study was to identify the prevalence of OSA in a lower extremity artery disease (LEAD) study population. Methods: A total of 91 patients receiving in- and outpatient treatment for LEAD were included in this prospectively conducted trial. In addition to an angiological examination, all patients underwent nocturnal screening for sleep-disordered breathing by use of SOMNOcheck micro® (SC micro) and - depending on the results obtained - polysomnography. Results: Patients were principally late middle-aged (69.3 ± 10.8 years), male (71.4%) and slightly overweight (BMI 26.8 ± 3.9). Overnight screening determined a sleep apnoea prevalence of 78.0%, of which 90.1% exhibited a predominantly obstructive genesis. The mean apnoea-hypopnoea index (AHI; events/h) and oxygen desaturation index (events/h) averaged 11.8 ± 13.4 and 8.9 ± 14.2, respectively. The individual AHI categories of non-pathological (<5), mild (5 to <15), moderate (15 to <30) and severe sleep apnoea (≥30) accounted for 22.0, 59.3, 13.2 and 5.5%, respectively. A distributive examination of AHI within LEAD severity groups evinced a significant association (p = 0.047). In cases of at least moderate sleep apnoea (AHI ≥15) polysomnography was performed (n = 17, 18.7% of the whole collective). Correlative analysis revealed a significant correlation between values obtained by SC micro recording and polysomnography, establishing the diagnostic accuracy of the screening results. Conclusions: OSA exhibits an important prevalence of 70.3% in LEAD patients with prior undiagnosed sleep-disordered breathing, indicating major OSA unawareness in this cardiovascular cohort. However, the impact of OSA treatment on LEAD propagation remains to be determined. © 2015 S. Karger AG, Basel.

Sleep disordered breathing and post-discharge mortality in patients with acute heart failure

BACKGROUND

Hospitalizations for heart failure are associated with a high post-discharge risk for mortality. Identification of modifiable predictors of post-discharge mortality during hospitalization may improve outcome. Sleep disordered breathing (SDB) is the most common co-morbidity in heart failure patients.

DESIGN, SETTING, AND PARTICIPANTS

Prospective cohort study of patients hospitalized with acute heart failure (AHF) in a single academic heart hospital. Between January 2007 and December 2010, all patients hospitalized with AHF who have left ventricular ejection fraction (LVEF) ≤ 45% and were not already diagnosed with SDB were the target population.

MAIN OUTCOMES AND MEASURES

Patients underwent in-hospital attended polygraphy testing for SDB and were followed for a median of 3 years post-discharge. Mortality was recorded using national and state vital statistics databases.

RESULTS

During the study period, 1117 hospitalized AHF patients underwent successful sleep testing. Three hundred and forty-four patients (31%) had central sleep apnoea (CSA), 525(47%) patients had obstructive sleep apnoea (OSA), and 248 had no or minimal SDB (nmSDB). Of those, 1096 patients survived to discharge and were included in the mortality analysis. Central sleep apnoea was independently associated with mortality. The multivariable hazard ratio (HR) for time to death for CSA vs. nmSDB was 1.61 (95% CI: 1.1, 2.4, P = 0.02). Obstructive sleep apnoea was also independently associated with mortality with a multivariable HR vs. nmSDB of 1.53 (CI: 1.1, 2.2, P = 0.02). The Cox proportional hazards model adjusted for the following covariates: LVEF, age, BMI, sex, race, creatinine, diabetes, type of cardiomyopathy, coronary artery disease, chronic kidney disease, discharge systolic blood pressure <110, hypertension, discharge medications, initial length of stay, admission sodium, haemoglobin, and BUN.

CONCLUSIONS

This is the largest study to date to evaluate the effect of SDB on post-discharge mortality in patients with AHF. Newly diagnosed CSA and OSA during AHF hospitalization are independently associated with post-discharge mortality.

Mechanisms and clinical consequences of untreated central sleep apnea in heart failure

Central sleep apnea (CSA) is a highly prevalent, though often unrecognized, comorbidity in patients with heart failure (HF). Data from HF population studies suggest that it may present in 30% to 50% of HF patients. CSA is recognized as an important contributor to the progression of HF and to HF-related morbidity and mortality. Over the past 2 decades, an expanding body of research has begun to shed light on the pathophysiologic mechanisms of CSA. Armed with this growing knowledge base, the sleep, respiratory, and cardiovascular research communities have been working to identify ways to treat CSA in HF with the ultimate goal of improving patient quality of life and clinical outcomes. In this paper, we examine the current state of knowledge about the mechanisms of CSA in HF and review emerging therapies for this disorder.

Positive airway pressure therapy for heart failure

Heart failure (HF) is a life-threatening disease and is a growing public health concern. Despite recent advances in pharmacological management for HF, the morbidity and mortality from HF remain high. Therefore, non-pharmacological approaches for HF are being developed. However, most non-pharmacological approaches are invasive, have limited indication and are considered only for advanced HF. Accordingly, the development of less invasive, non-pharmacological approaches that improve outcomes for patients with HF is important. One such approach may include positive airway pressure (PAP) therapy. In this review, the role of PAP therapy applied through mask interfaces in the wide spectrum of HF care is discussed.

Performance of conventional and enhanced adaptive servoventilation (ASV) in heart failure patients with central sleep apnea who have adapted to conventional ASV

PURPOSE

Adaptive servo-ventilation (ASV) is a positive pressure ventilator support system to normalize ventilation in patients with Cheyne-Stokes respiration (CSR). The latest generation enhanced ASV device (PaceWave; ResMed) has a new feature--auto-adjustment of EPAP. This study tested the hypothesis that enhanced ASV with auto-adjustment of EPAP (PaceWave) is non-inferior to conventional ASV (AutoSetCS).

METHODS

This prospective, randomized, crossover, single-center study enrolled adult patients with stable heart failure (HF) and moderate-to-severe sleep-disordered breathing (SDB) who had been receiving conventional ASV therapy for at least 4 weeks. Patients received conventional ASV for one night and enhanced ASV on another night. Support settings for the two ASV devices were similar, with fixed expiratory positive airway pressure (EPAP) set to between 4 and 10 cm H2O and variable EPAP set to between 4 and 15 cm H2O. Full polysomnography was performed during ASV therapy on both nights. Endpoints were the number of nocturnal respiratory events and oxygen desaturations, and changes in blood pressure (BP).

RESULTS

Levels of EPAP were comparable during the use of enhanced and conventional ASV, but minimum and maximum inspiratory pressure support values were significantly higher with the PaceWave device. All measures of apnea and hypopnea, and oxygen saturation, were significantly improved during ASV therapy with either device. There were no significant changes in BP or heart rate.

CONCLUSIONS

Enhanced ASV is non-inferior to ASV with fixed EPAP in patients with chronic HF and CSR, with a trend towards better control of respiratory events.

Arrhythmia risk associated with sleep disordered breathing in chronic heart failure

The intersecting relationships of sleep disordered breathing (SDB), arrhythmogenic risk and chronic heart failure (HF) are complex and most likely multi-directional and synergistic. Autonomic dysfunction is a common pathophysiological feature of each of these entities. Intermittent hypoxia, hypercapnia, mechanical cardiac influences due to upper airway obstruction and rostral fluid shifts are SDB-specific mechanisms which may trigger, perpetuate and exacerbate HF and arrhythmogenesis. Specific pathophysiological mechanisms will vary according to the predominance of central as compared to obstructive sleep apnea. The risk of cardiac arrhythmias and HF attributable to SDB may be considerable given the high prevalence of SDB and its likely physiologic burden. The current review focuses on the data, which have accrued elucidating the specific contributory mechanisms of SDB in cardiac arrhythmias and HF, highlighting the clinical relevance and effects of standard SDB treatment on these outcomes, and describing the role of novel therapeutics.

Cardiac arrhythmias and sleep-disordered breathing in patients with heart failure

The relationship between heart failure (HF), sleep-disordered breathing and cardiac arrhythmias is complex and poorly understood. Whereas the frequency of predominantly obstructive sleep apnea in HF patients is low and similar or moderately higher to that observed in the general population, central sleep apnea (CSA) has been observed in approximately 50% of HF patients, depending on the methods used to detect CSA and patient selection. Despite this high prevalence, it is still unclear whether CSA is merely a marker or an independent risk factor for an adverse prognosis in HF patients and whether CSA is associated with an increased risk for supraventricular as well as ventricular arrhythmias in HF patients. The current review focuses on the relationship between CSA and atrial fibrillation as the most common atrial arrhythmia in HF patients, and on the relationship between CSA and ventricular tachycardia and ventricular fibrillation as the most frequent cause of sudden cardiac death in HF patients.

Severe central sleep apnea is associated with atrial fibrillation in patients with left ventricular systolic dysfunction

BACKGROUND

The results of previous studies investigating the association between atrial fibrillation (AF) and central sleep apnea (CSA) in patients with left ventricular (LV) systolic dysfunction are contradictory.

METHODS

We prospectively enrolled 267 patients in this cross-sectional study with LV ejection fractions ≤50%, who were screened for sleep disordered breathing using cardiorespiratory polysomnography after patients with predominantly obstructive sleep apnea or insufficient sleep studies had been excluded.

RESULTS

AF at study entry was found in 70 of 267 patients (26%). CSA with an apnea/hypopnea index (AHI) ≥15/hour was present in 116 patients (43%) and 67 patients (25%) had severe CSA with an AHI > 30/hour. Univariate analysis revealed a significant association between AF and severe CSA, age, male gender, arterial hypertension, left atrial diameter, brain natriuretic peptide, chronic kidney disease, New York Heart Association class, digitalis, and the lack of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers. Multivariate analysis revealed a significant association between AF and severe CSA (odds ratio [OR]: 5.21; 95% confidence interval [CI]: 1.67-16.27, P = 0.01), age (OR: 1.22 per 5-year increase; 95% CI: 1.05-1.40, P = 0.01), left atrial diameter (OR 1.61 per 5-mm increase; 95% CI: 1.22-2.01, P < 0.01), and digitalis (OR: 2.7; 95% CI: 1.26-5.79, P = 0.01).

CONCLUSIONS

AF is associated with severe CSA but not with moderate CSA in addition to age, use of digitalis, and left atrial size in patients with LV systolic dysfunction. Future studies evaluating the potential benefit of adaptive servo-ventilation therapy to prevent AF or to decrease the AF burden in heart failure patients should therefore focus on patients with severe central sleep apnea.

Sleep and breathing in congestive heart failure

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

Contemporary insights and novel treatment approaches to central sleep apnea syndrome in heart failure

OPINION STATEMENT

Central sleep apnea (CSA) is a common and under-diagnosed condition commonly associated with Cheyne-Stokes respiration. It is particularly prevalent in the heart failure population affecting up to 40 % of all patients with heart failure. The pathophysiology associated with CSA is based on the underlying effects of hypoventilation and hyperventilation, with neurologic dysregulation of respiratory control as the primary defect. However, therapeutic options are limited because of the prevailing perception that CSA is a consequence, rather than cause of morbidity and mortality. At present, the main focus remains treating the underlying problem (ie, intensifying heart failure therapeutics, decongestion), whereas additional suggestions of using acetazolamide, progesterone, nocturnal oxygen, and theophylline have not been validated with contemporary clinical trials. Positive pressure ventilation is currently the primary recommendation for all patients with sleep-disordered breathing (CSA included), and in some patients may effectively reduce the apnea-hypopnea index. However, significant research is ongoing to determine how to treat this complex patient population.

Determining the prevalence and predictors of sleep disordered breathing in patients with chronic heart failure: rationale and design of the SCHLA-HF registry

Background

The objective of the SCHLA-HF registry is to investigate the prevalence of sleep-disordered breathing (SDB) in patients with chronic heart failure with reduced left ventricular systolic function (HF-REF) and to determine predictors of SDB in such patients.

Methods

Cardiologists in private practices and in hospitals in Germany are asked to document patients with HF-REF into the prospective SCHLA-HF registry if they meet predefined inclusion and exclusion criteria. Screening was started in October 2007 and enrolment was completed at the end of May 2013. After enrolment in the registry, patients are screened for SDB. SDB screening is mainly undertaken using the validated 2-channel ApneaLink™ device (nasal flow and pulse oximetry; ResMed Ltd., Sydney, Australia). Patients with a significant number of apneas and hypopneas per hour recording time (AHI ≥15/h) and/or clinical symptoms suspicious of SDB will be referred to a cooperating sleep clinic for an attended in-lab polysomnography with certified scoring where the definite diagnosis and, if applicable, the differentiation between obstructive and central sleep apnea will be made. Suggested treatment will be documented.

Discussion

Registries play an important role in facilitating advances in the understanding and management of cardiovascular disease. The SCHLA-HF registry will provide consistent data on a large group of patients with HF-REF that will help to answer questions on the prevalence, risk factors, gender differences and stability of SDB in these patients by cross-sectional analyses. Further insight into the development of SDB will be gained by extension of the registry to include longitudinal data.

Complex sleep apnea

OPINION STATEMENT

Complex sleep apnea currently refers to the emergence and persistence of central apneas and hypopneas following the application of positive airway pressure therapy in patients with obstructive sleep apnea. However, this narrow definition is an "outcome" and does not capture the spectrum of pathological activation of the respiratory chemoreflex in sleep apnea. The International Classification of Sleep Disorders - 3rd edition recognizes the phenomenon of Treatment-Related Central Sleep Apnea, but the phenotype is usually evident prior to onset of therapy. The key polysomnographic characteristics of chemoreflex modulated and mediated sleep apnea are nonrapid eye movement (NREM) dominance of respiratory events, short (<30 seconds) or long (>60 seconds) cycle time with a self-similar metronomic timing, and spontaneous improvement during rapid eye movement (REM) sleep. Thus, the majority of chemoreflex effects go unrecognized due to the bias toward obstructive sleep apnea's current scoring criteria. Any treatment of apparently obstructive sleep apnea, including surgery and oral appliances, can expose chemoreflex-driven instabilities. As both sleep fragmentation and a narrow CO2 reserve or increased loop gain drive the disease, sedatives (to induce longer periods of stable NREM sleep and reduce the destabilizing effects of arousals in NREM sleep) and CO2-based stabilization approaches are logical. Adaptive ventilation reduces mean hyperventilation yet can induce ventilator-patient desynchrony, while enhanced expiratory rebreathing space (EERS, dead space during positive pressure therapy) and CO2 manipulation directly stabilize respiratory control by moving CO2 above the apnea threshold. Carbonic anhydrase inhibition can provide further adjunctive benefits. Novel pharmacological approaches may target mediators of carotid body hypoxic sensitization, such as the balance between gas neurotransmitters. In complex apnea patients, single mode therapy is unlikely to be successful, and the power of multi-modality therapy should be harnessed for optimal outcomes.

Sleep apnoea and the heart

Sleep apnoea is associated with significant daytime functioning impairment and marked cardiovascular morbidities, leading to a significant increase in mortality. Sympathetic activation, oxidative stress and systemic inflammation have been shown to be the main intermediary mechanisms associated with sleep apnoea and intermittent hypoxia. There are now convincing data regarding the association between hypertension, arrhythmias, coronary heart disease, heart failure, increased cardiovascular mortality and sleep apnoea. This has been evidenced in sleep apnoea patients and is supported by experimental data obtained in intermittent hypoxia. Whether treating sleep apnoea enables chronic cardiovascular consequences to be reversed is not fully established as regard coronary heart disease, arrhythmias and heart failure. In this late condition, complex bidirectional relationships occur, with obstructive sleep apnoea being a risk factor for heart failure whilst central sleep apnoea mainly appears as a consequence of heart failure. It remains to be established in adequately designed studies, i.e. large randomised controlled trials, whether treating sleep apnoea can improve heart failure morbidity and mortality.

Sleep-disordered breathing in patients undergoing transfemoral aortic valve implantation for severe aortic stenosis

BACKGROUND

We examined the prevalence of sleep-disordered breathing (SDB) in patients with severe aortic valve stenosis (AS) and the impact of transfemoral aortic valve implantation (TAVI) on SDB.

METHODS

79 patients underwent cardiorespiratory polygraphy (PG) before TAVI (CoreValve™), 62 of them a second PG after the procedure.

RESULTS

Forty-nine (62 %) patients had obstructive sleep apnea (OSA), 25 (32 %) central sleep apnea (CSA), and 5 (6 %) presented without significant SDB (apnea-hypopnea index (AHI) < 5/h). Among the 62 patients evaluated before and after TAVI, 36 (58 %) had OSA, 22 (36 %) CSA, and 4 patients (7 %) no SDB. AHI was significantly higher in CSA patients than in OSA patients (34.5 ± 18.3 vs. 18.0 ± 12.6/h, p < 0.001). Successful TAVI had a significant impact on CSA but not on OSA: CSA patients with optimal TAVI results experienced a significant reduction in central respiratory events (AHI 39.6 ± 19.6-23.1 ± 16.0/h, p = 0.035), while no changes were detected in OSA patients (AHI 18.8 ± 13.0-20.25 ± 13.4/h, p = 0.376). In contrast, in patients who developed at least moderate periprosthetic aortic regurgitation (AR > I), CSA increased significantly (AHI 26.3 ± 13.2-39.2 ± 18.4/h, p = 0.036), whereas no acute change was seen in patients with OSA (AHI 10.5 ± 7.8-12.5 ± 5.0/h, p = 0.5).

CONCLUSION

OSA and CSA are prevalent in more than 90 % of patients undergoing TAVI for severe aortic valve stenosis. Successful TAVI had no significant impact on OSA but improved CSA. In case of an acute change from pressure overload (aortic stenosis) to acute volume overload (aortic regurgitation after TAVI), central, but not obstructive, sleep apnea deteriorated.

Symptoms of sleep apnoea in chronic heart failure--results from a prospective cohort study in 1,500 patients

BACKGROUND

In patients with chronic heart failure, sleep-disordered breathing (SDB) is a common co-morbidity worsening prognosis. The aim of this study was to investigate whether assessment of specific symptoms can elucidate presence of SDB in these patients.

METHODS

A prospective questionnaire scoring investigation on possible symptoms of sleep apnoea (nocturia, fatigue, daytime sleepiness, snoring, nocturnal sweating, witnessed apnoea's, nap) was conducted in 1,506 consecutive patients with stable chronic heart failure (LVEF ≤45%, NYHA ≥2). Afterwards, polysomnography or polygraphy, capillary blood gas analysis, echocardiography, and cardiopulmonary exercise testing were performed.

RESULTS

Adjusted for all significant covariates, snoring (p < 0.01) was the only symptom independently associated with OSA, while witnessed apnoeas (p = 0.02) and fatigue (p = 0.03) independently predicted for CSR. As additional parameters, higher BMI (threshold 26.6; p < 0.01) and higher pCO(2) (threshold 37.6 mmHg; p < 0.01) were independently associated with OSA and male gender (p < 0.001) and lower pCO(2) (threshold 35.0 mmHg; p < 0.001) with CSA. Cumulative questionnaire score results did not sufficiently (OSA--sensitivity 0.40, specificity 0.74; CSA--sensitivity 0.57, specificity 0.59) predict SDB.

CONCLUSION

Although in chronic heart failure patients with either OSA or CSA specific symptoms are apparent, combining clinical data, demographic data, and capillary blood gas analysis results appears favourable to determine the presence of SDB.