Effect of phrenic nerve stimulation on patients with central sleep apnea: A meta-analysis

Patients with central sleep apnea (CSA) have a lower quality of life and higher morbidity and mortality. Phrenic nerve stimulation (PNS) is a novel treatment for CSA that has been shown to be safe. However, the effects of PNS on sleep changes are still under debate. This meta-analysis was performed to evaluate the efficacy of PNS in patients with CSA. PubMed, Scopus, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL) and Web of Science databases were searched for relevant studies published. We performed random-effects meta-analyses of the changes in apnea-hypopnea index (AHI), central apnea index (CAI), Arousal Index, percent of sleep with O2 saturation <90% (T90), Epworth Sleepiness Scale (ESS) and sleep efficiency. Ten studies with a total of 580 subjects were analyzed. Overall meta-analysis showed AHI [SMD: -2.24, 95% confidence interval (CI): was -3.11 to -1.36(p＜0.00001)], CAI [SMD: -2.32, 95% CI: -3.17 to -1.47 (p＜0.00001)] and Arousal Index (p = 0.0002, SMD (95% CI) -1.79 (-2.74 to -0.85)) significantly reduced after PNS. No significant changes were observed in T90, ESS and sleep efficiency (p > 0.05). Meta-analysis of observational studies demonstrated AHI, CAI and Arousal Index had a decreasing trend between before and after PNS (all, p＜0.05). However, ESS and T90 did not change significantly after PNS (p > 0.05). Meta-analysis of RCTs showed that CSA patients had trends of a lower AHI (I2 = 0%), CAI (I2 = 74%), Arousal Index (I2 = 0%), T90 (I2 = 0%) and ESS (I2 = 0%) after PNS (all, p＜0.05). The use of PNS appears to be safe and feasible in patients with CSA. However, larger, independent RCTs are required to investigate the efficacy and long-term effect of PNS and more attention should be paid to T90 and ESS.

Phrenic nerve stimulation for the treatment of central sleep apnea in patients with heart failure

OBJECTIVE

Central sleep apnea (CSA) is associated with increased morbidity and mortality in patients with heart failure (HF). We aimed to explore the effectiveness of phrenic nerve stimulation (PNS) on CSA in patients with HF.

METHODS

This was a prospective and non-randomized study. The stimulation lead was inserted into the right brachiocephalic vein and attached to a proprietary neurostimulator. Monitoring was conducted during the implantation process, and all individuals underwent two-night polysomnography.

RESULTS

A total of nine subjects with HF and CSA were enrolled in our center. There was a significant decrease in the apnea-hypopnea index (41 ± 18 vs 29 ± 25, p = 0.02) and an increase in mean arterial oxygen saturation (SaO2) (93% ± 1% vs 95% ± 2%, p = 0.03) after PNS treatment. We did not observe any significant differences of oxygen desaturation index (ODI) and SaO2 < 90% (T90) following PNS. Unilateral phrenic nerve stimulation might also categorically improve the severity of sleep apnea.

CONCLUSION

In our non-randomized study, PNS may serve as a therapeutic approach for CSA in patients with HF.

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.

Abnormal Sleep-Related Breathing Related to Heart Failure

Sleep-disordered breathing (SDB) is highly prevalent in patients with heart failure (HF). Untreated obstructive sleep apnea (OSA) and central sleep apnea (CSA) in patients with HF are associated with worse outcomes. Detailed sleep history along with polysomnography (PSG) should be conducted if SDB is suspected in patients with HF. First line of treatment is the optimization of medical therapy for HF and if symptoms persist despite optimization of the treatment, positive airway pressure (PAP) therapy will be started to treat SDB. At present, there is limited evidence to prescribe any drugs for treating CSA in patients with HF. There is limited evidence for the efficacy of continuous positive airway pressure (CPAP) or adaptive servo-ventilation (ASV) in improving mortality in patients with heart failure with reduced ejection fraction (HFrEF). There is a need to perform well-designed studies to identify different phenotypes of CSA/OSA in patients with HF and to determine which phenotype responds to which therapy. Results of ongoing trials, ADVENT-HF, and LOFT-HF are eagerly awaited to shed more light on the management of CSA in patients with HF. Until then the management of SDB in patients with HF is limited due to the lack of evidence and guidance for treating SDB in patients with HF.

Transvenous Phrenic Nerve Stimulation for Central Sleep Apnea: Clinical and Billing Review

Central sleep apnea (CSA) frequently coexists with heart failure and atrial fibrillation and contributes to cardiovascular disease progression and mortality. A transvenous phrenic nerve stimulation (TPNS) system has been approved for the first time by the Food and Drug Administration for the treatment of CSA. This system, remedē® ZOLL Medical, Inc. is implanted during a minimally invasive outpatient procedure, and has shown a favorable safety and efficacy profile. Currently, patients' access to this therapy remains limited by the small number of specialized centers in the US and the absence of a standard coverage process by insurers. While a period of evaluation by insurers is expected for new therapies in their early stages, the impact on patients is particularly severe given the already limited treatment options for CSA. Implantation and management of this novel therapy requires the establishment of a specialized multidisciplinary program as part of a Sleep Medicine practice and support from health care systems and hospitals. Several centers in the US have been successful in building sustainable TPNS program offering this novel therapy to their patients by navigating the current reimbursement environment. In this article, we will review the background and efficacy data of TPNS and briefly address relevant aspects of the clinical activities involved in a TPNS program. The article will present the status of coverage and reimbursement for this novel therapy. We will also discuss the current approach to obtaining reimbursement from third party payors during this transitional period of evaluation by Medicare and other insurers.

Computational Modeling of an Endovascular Peripheral Nerve Interface

Implantable neuromodulation devices that interface with the peripheral nervous system are a promising approach to restore functions lost to nerve damage. Existing nerve stimulation electrodes require direct contact with the target nerve and are associated with mechanical nerve damage and fibrous tissue encapsulation. Endovascularly delivered electrode arrays may provide a less invasive solution. Using a hybrid tissue conductor-neuron model and computational simulations, this study demonstrates the feasibility of delivering electrical stimulation of a peripheral nerve from a blood vessel in the vicinity of the target and predicts that the stimulation intensity required strongly depends on nerve-vessel distance and relative orientation, which are important factors to consider when screening candidate blood vessels for electrode implantation.

Evolving Cardiac Electrical Therapies for Advanced Heart Failure Patients

Symptomatic heart failure (HF) patients despite optimal medical therapy and advances such as invasive hemodynamic monitoring remain challenging to manage. While cardiac resynchronization therapy remains a highly effective therapy for a subset of HF patients with wide QRS, a majority of symptomatic HF patients are poor candidates for such. Recently, cardiac contractility modulation, neuromodulation based on carotid baroreceptor stimulation, and phrenic nerve stimulation have been approved by the US Food and Drug Administration and are emerging as therapeutic options for symptomatic HF patients. This state-of-the-art review examines the role of these evolving electrical therapies in advanced HF.

All You Need Is Sleep: the Effects of Sleep Apnea and Treatment Benefits in the Heart Failure Patient

PURPOSE OF REVIEW

Recognition and treatment of sleep apnea is an important but easily overlooked aspect of care in the heart failure patient. This review summarizes the data behind the recommendations in current practice guidelines and highlights recent developments in treatment options.

RECENT FINDINGS

Neuromodulation using hypoglossal nerve stimulation has been increasingly used for treatment of OSA; however, it has not been studied in the heart failure population. Alternatively, phrenic nerve stimulation for treatment of CSA is effective for heart failure patients, and cardiac resynchronization therapy can be effective in improving CSA in pacing-induced cardiomyopathy. In patients suspected to have sleep apnea, polysomnography is recommended to better understand the prognosis and treatment options. Positive airway pressure is the standard treatment for sleep apnea; however, neurostimulation can be especially effective in those with predominantly central events. Understanding the pathophysiology of sleep apnea can guide further management decisions.

Central sleep apnea and atrial fibrillation: A review on pathophysiological mechanisms and therapeutic implications

Precipitating factors and chronic diseases associated with atrial fibrillation (AF) are detailed in the literature. Emerging evidence over the last several decades suggests a potential causal relationship between central sleep apnea (CSA) and AF. Mechanisms including apnea-induced hypoxia with intermittent arousal, fluctuating levels of carbon dioxide, enhanced sympathetic/neurohormonal activation and oxidative stress causing inflammation have been implicated as etiologic causes of AF within this subpopulation. CSA affects the efficacy of pharmacologic and catheter-based antiarrhythmic treatments, which is why treating CSA prior to these interventions may lead to lower rates of AF. Subsequently, a reduction in the AF burden with transvenous phrenic nerve stimulation (TPNS) has become a topic of interest. The present review describes the relationship between these conditions, pathophysiologic mechanisms implicating the role of CSA in development of AF, and emerging therapeutic interventions.

Central Sleep Apnea in Patients with Heart Failure-How to Screen, How to Treat

PURPOSE OF REVIEW

Central sleep apnea occurs in up to 50% of heart failure patients and worsens outcomes. Established therapies are limited by minimal supporting evidence, poor patient adherence, and potentially adverse cardiovascular effects. However, transvenous phrenic nerve stimulation, by contracting the diaphragm, restores normal breathing throughout sleep and has been shown to be safe and effective. This review discusses the mechanisms, screening, diagnosis, and therapeutic approaches to CSA in patients with HF.

RECENT FINDINGS

In a prospective, multicenter randomized Pivotal Trial (NCT01816776) of transvenous phrenic nerve stimulation with the remedē System, significantly more treated patients had a ≥ 50% reduction in apnea-hypopnea index compared with controls, with a 41 percentage point difference between group difference at 6 months (p < 0.0001). All hierarchically tested sleep, quality of life, and daytime sleepiness endpoints were significantly improved in treated patients. Freedom from serious related adverse events at 12 months was 91%. Benefits are sustained to 36 months. Transvenous phrenic nerve stimulation improves quality of life in patients with heart failure and central sleep apnea. Controlled trials evaluating the impact of this therapy on mortality/heart failure hospitalizations and "real world" experience are needed to confirm safety and effectiveness.

Meta-analysis of Usefulness of Phrenic Nerve Stimulation in Central Sleep Apnea

Transvenous neurostimulation of the phrenic nerve (PNS) is a potentially improved and unique approach to the treatment of central sleep apnea (CSA). There have been multiple studies with limited individuals evaluating the efficacy of PNS. Our aim was to review and pool those studies to better understand whether phrenic nerve stimulation is efficacious in the treatment of CSA. The initial search on Pubmed retrieved a total of 97 articles and after screening all articles, only 5 could be included in our quantitative analysis. Pooling of data from 5 studies with a total of 204 patients demonstrated a reduction of mean apnea hypopnea index with PNS compared to controls by -26.7 events/hour with 95% confidence interval and P value of [CI (-31.99, -21.46), I² 85, p 0.00]. The mean difference in central apnea index was -22.47 [CI (-25.19, -19.76), I² 0, p 0.00]. The mean reduction in the oxygen desaturation index of 4% or more demonstrated a decrease in PNS group by -24.16 events/hour [(CI -26.20, -22.12), I² 0, p 0.00] compared with controls. PNS resulted in mean reduction in arousal index of -13.77 [CI (-16.15, -11.40), I² 0, p 0.00]. The mean change in percent of time spent in rapid eye movement sleep demonstrated a nonsignificant increase in PNS group by 1.01 % [CI (-5.67, 7.86), I²93, p 0.75]. In conclusion, PNS therapy for treating CSA demonstrated positive outcomes but larger randomized studies are needed to evaluate the safety and clinical outcomes.

Pacing therapies for sleep apnea and cardiovascular outcomes: A systematic review

PURPOSE

Phrenic and hypoglossal nerve pacing therapies have shown benefit in sleep apnea. We sought to analyze the role of pacing therapies in sleep apnea and their impact on heart failure.

METHODS

A comprehensive literature search in PubMed and Google Scholar from inception to August 5, 2019, was performed. A meta-analysis was performed using fixed effects model to calculate mean difference (MD) with 95% confidence interval (CI).

RESULTS

Six studies were eligible and included 626 patients, of whom 334 were in the control arm and 393 were in the experimental arm. Phrenic nerve pacing (MD - 23.20 events/h, 95% CI - 27.96 to - 18.44, p < 0.00001) and hypoglossal nerve pacing (MD - 20.24 events/h, 95% CI - 23.22 to - 17.27, p < 0.00001) were associated with improvements in apnea-hypopnea index (AHI). Phrenic nerve pacing was associated with a trend towards improvements in left ventricular ejection fraction (MD 3.95%, 95% CI - 0.04 to 7.94, p = 0.05). Hypoglossal and phrenic nerve pacing were associated with improvements in the quality of life as assessed by improvements in Epworth sleepiness scale (MD 3.71 points, 95% CI 2.89 to 4.54, p < 0.00001).

CONCLUSIONS

Our analysis suggests that phrenic and hypoglossal nerve pacing improves AHI and quality of life with a trend towards improvement in left ventricular ejection fraction, especially in central sleep apnea. Complications were high but future refinement in technology will likely improve clinical outcomes and minimize complications.

Sleep Apnea and Heart

Scientific investigations in the past few decades have supported the important role of sleep in various domains of health. Sleep apnea is a highly prevalent yet underdiagnosed sleep disorder representing a valid cardiovascular risk factor, particularly for hypertension. While several studies have demonstrated the benefits of sleep apnea treatment on subclinical cardiovascular measures, there is a paucity of studies proving reduction of cardiovascular events and mortality. Sufficient and high-quality sleep is also important in the maintenance of cardiovascular health. Future investigations should focus on improving identification of patients at greatest risk of adverse cardiovascular s sequalae of sleep apnea and testing the therapeutic benefit of sleep apnea treatment in this vulnerable group.

Phrenic Nerve Stimulation for the Treatment of Central Sleep Apnea: A Pooled Cohort Analysis

STUDY OBJECTIVES

Early evidence with transvenous phrenic nerve stimulation (PNS) demonstrates improved disease severity and quality of life (QOL) in patients with central sleep apnea (CSA). The goal of this analysis is to evaluate the complete prospective experience with PNS in order to better characterize its efficacy and safety, including in patients with concomitant heart failure (HF).

METHODS

Using pooled individual data from the pilot (n = 57) and pivotal (n = 151) studies of the remedē System in patients with predominant moderate to severe CSA, we evaluated 12-month safety and 6- and 12-month effectiveness based on polysomnography data, QOL, and cardiac function.

RESULTS

Among 208 combined patients (June 2010 to May 2015), a remedē device implant was successful in 197 patients (95%), 50/57 pilot study patients (88%) and 147/151 pivotal trial patients (97%). The pooled cohort included patients with CSA of various etiologies, and 141 (68%) had concomitant HF. PNS reduced apnea-hypopnea index (AHI) at 6 months by a median of -22.6 episodes/h (25th and 75th percentile; -38.6 and -8.4, respectively) (median 58% reduction from baseline, P < .001). Improvement in sleep variables was maintained through 12 months of follow-up. In patients with HF and ejection fraction ≤ 45%, PNS was associated with improvement in systolic function from 27.0% (23.3, 36.0) to 31.1% (24.0, 41.5) at 12 months (P = .003). In the entire cohort, improvement in QOL was concordant with amelioration of sleep measures.

CONCLUSIONS

Transvenous PNS significantly improves CSA severity, sleep quality, ventricular function, and QOL regardless of HF status. Improvements, which are independent of patient compliance, are sustained at 1 year and are associated with acceptable safety.

Sleep – the yet underappreciated player in cardiovascular diseases: A clinical review from the German Cardiac Society Working Group on Sleep Disordered Breathing

Patients with a wide variety of cardiovascular diseases, including arterial and pulmonary hypertension, arrhythmia, coronary artery disease and heart failure, are more likely to report impaired sleep with reduced sleep duration and quality, and also, sometimes, sleep interruptions because of paroxysmal nocturnal dyspnoea or arrhythmias. Overall, objective short sleep and bad sleep quality (non-restorative sleep) and subjective long sleep duration are clearly associated with major cardiovascular diseases and fatal cardiovascular outcomes. Sleep apnoea, either obstructive or central in origin, represents the most prevalent, but only one, of many sleep-related disorders in cardiovascular patients. However, observations suggest a bidirectional relationship between sleep and cardiovascular diseases that may go beyond what can be explained based on concomitant sleep-related disorders as confounding factors. This makes sleep itself a modifiable treatment target. Therefore, this article reviews the available literature on the association of sleep with cardiovascular diseases, and discusses potential pathophysiological mechanisms. In addition, important limitations of the current assessment, quantification and interpretation of sleep in patients with cardiovascular disease, along with a discussion of suitable study designs to address future research questions and clinical implications are highlighted. There are only a few randomised controlled interventional outcome trials in this field, and some of the largest studies have failed to demonstrate improved survival with treatment (with worse outcomes in some cases). In contrast, some recent pilot studies have shown a benefit of treatment in selected patients with underlying cardiovascular diseases.

Unilateral phrenic nerve stimulation in the therapeutical algorithm of central sleep apnoea in heart failure

PURPOSE OF REVIEW

Central sleep apnoea (CSA) is highly prevalent in patients with heart failure and substantially impairs survival. If optimal cardiac treatment fails, alternative therapeutical options, including positive airway pressure (PAP) therapies, drugs or application of oxygen and carbon dioxide are considered to suppress CSA which interfere with the complex underlying pathophysiology. Most recently, unilateral phrenic nerve stimulation (PNS) has been studied in these patients. Therefore, there is an urgent need to critically evaluate efficacy, potential harm and positioning of PNS in current treatment algorithms.

RECENT FINDINGS

Data from case series and limited randomized controlled trials demonstrate the feasibility of the invasive approach and acceptable peri-interventional adverse events. PNS reduces CSA by 50%, a figure comparable with continuous PAP or oxygen. However, PNS cannot improve any comorbid upper airways obstruction. A number of fatalities due to malignant cardiac arrhythmias or other cardiac events have been reported, although the association with the therapy is unclear.

SUMMARY

PNS offers an additional option to the therapeutical portfolio. Intervention-related adverse events and noninvasive alternatives need clear discussion with the patient. The excess mortality in the SERVE-HF study has mainly been attributed to sudden cardiac death. Therefore, previous cardiac fatalities under PNS urge close observation in future studies as long-term data are missing.

[Transvenous neurostimulation in central sleep apnea associated with heart failure]

Sleep-related breathing disorders can be classified as either obstructive (OSA) or central sleep apnea (CSA). Whereas there is substantial knowledge about the pathophysiology and sound recommendations for the diagnosis and treatment of OSA, the origin of CSA is still incompletely understood, patient identification is difficult and the necessity for specific treatment is under debate. CSA often accompanies heart failure and is associated with an adverse prognosis. Optimized heart failure treatment reduces CSA and is thus the cornerstone of CSA treatment. In contrast to OSA, noninvasive ventilation does not lead to prognostic improvement in CSA and ASV ventilation may even lead to an increase in mortality. Transvenous neurostimuation of the phrenic nerve is currently under clinical investigation as a new therapeutic modality for CSA. Early results demonstrate positive effects on sleep parameters and quality of life without any evidence for a negative impact on mortality. However, these results await confirmation in larger studies before this new approach can be advocated for routine clinical use.

Management of Sleep Apnea in Heart Failure

Sleep-disordered breathing (SDB) is highly prevalent in heart failure (HF). The presence of SDB in patients with HF appears to be associated with increased risk of cardiovascular morbidity and mortality. In this article, we describe the types, pathophysiology, and consequences of SDB and discuss ways in which SDB can be diagnosed. We also lay emphasis on the recent randomized controlled trials that have had a major impact on how SDB is managed and highlight the complex relationship between SDB and outcomes.

Sustained 12 Month Benefit of Phrenic Nerve Stimulation for Central Sleep Apnea

Transvenous phrenic nerve stimulation improved sleep metrics and quality of life after 6 months versus control in the remedē System Pivotal Trial. This analysis explored the effectiveness of phrenic nerve stimulation in patients with central sleep apnea after 12 months of therapy. Reproducibility of treatment effect was assessed in the former control group in whom the implanted device was initially inactive for the sixth month and subsequently activated when the randomized control assessments were complete. Patients with moderate-to-severe central sleep apnea implanted with the remedē System were randomized to therapy activation at 1 month (treatment) or after 6 months (control). Sleep indices were assessed from baseline to 12 months in the treatment group and from 6 to 12 months in former controls. In the treatment group, a ≥50% reduction in apnea-hypopnea index occurred in 60% of patients at 6 months (95% confidence interval [CI] 47% to 64%) and 67% (95% CI 53% to 78%) at 12 months. After 6 months of therapy, 55% of former controls (95% CI 43% to 67%) achieved ≥50%reduction in apnea-hypopnea index. Patient Global Assessment was markedly ormoderately improved at 6 and 12 months in 60% of treatment patients.Improvements persisted at 12 months. A serious adverse event within 12 months occurred in 13 patients (9%). Phrenic nerve stimulation produced sustained improvements in sleep indices and quality of life to at least 12 months in patients with central sleep apnea. The similar improvement of former controls after 6 months of active therapy confirms benefits are reproducible and reliable.

Management of Sleep Disordered Breathing in Patients with Heart Failure

PURPOSE OF REVIEW

This paper reviews treatment options for sleep disordered breathing (SDB) in patients with heart failure. We sought to identify therapies for SDB with the best evidence for long-term use in patients with heart failure and to minimize uncertainties in clinical practice by examining frequently discussed questions: what is the role of continuous positive airway pressure (CPAP) in patients with heart failure? Is adaptive servo-ventilation (ASV) safe in patients with heart failure? To what extent is SDB a modifiable risk factor?

RECENT FINDINGS

Consistent evidence has demonstrated that the development of SDB in patients with heart failure is a poor prognostic indicator and a risk factor for cardiovascular mortality. However, despite numerous available interventions for obstructive sleep apnea and central sleep apnea, it remains unclear what effect these therapies have on patients with heart failure. To date, all major randomized clinical trials have failed to demonstrate a survival benefit with SDB therapy and one major study investigating the use of adaptive servo-ventilation demonstrated harm. Significant questions persist regarding the management of SDB in patients with heart failure. Until appropriately powered trials identify a treatment modality that increases cardiovascular survival in patients with SDB and heart failure, a patient's heart failure management should remain the priority of medical care.

Transvenous phrenic nerve stimulation, a novel therapeutic approach for central sleep apnea

Central sleep apnea (CSA) is common in heart failure (HF) patients. Traditional treatment of CSA, including continuous positive airway pressure (CPAP), adaptive servo ventilation (ASV), oxygen therapy, and CO₂ inhalation, has respective limitations. Transvenous phrenic nerve stimulation (PNS), a novel therapeutic approach for CSA, was proved to be effective and safe. The remedē^® system and related transvenous PNS methods was approved by FDA in 2017, for treating moderate to severe CSA.

The autonomic nervous system as a therapeutic target in heart failure: a scientific position statement from the Translational Research Committee of the Heart Failure Association of the European Society of Cardiology

Despite improvements in medical therapy and device-based treatment, heart failure (HF) continues to impose enormous burdens on patients and health care systems worldwide. Alterations in autonomic nervous system (ANS) activity contribute to cardiac disease progression, and the recent development of invasive techniques and electrical stimulation devices has opened new avenues for specific targeting of the sympathetic and parasympathetic branches of the ANS. The Heart Failure Association of the European Society of Cardiology recently organized an expert workshop which brought together clinicians, trialists and basic scientists to discuss the ANS as a therapeutic target in HF. The questions addressed were: (i) What are the abnormalities of ANS in HF patients? (ii) What methods are available to measure autonomic dysfunction? (iii) What therapeutic interventions are available to target the ANS in patients with HF, and what are their specific strengths and weaknesses? (iv) What have we learned from previous ANS trials? (v) How should we proceed in the future?

How to take arms against central apneas in heart failure

Introduction Despite being a risk mediator in several observational studies, central apneas are currently orphan of treatment in heart failure. After the neutral effects on survival of two randomized controlled trials (RCTs) based on the use of positive airway pressure (the CANPAP and SERVE-HF trials), two alternative hypotheses have been formulated: 1) Periodic breathing/Cheyne-Stokes respiration (PB/CSR) in HF is protective. Indeed, the Naughton's hypothesis assumes that hyperventilation leads to increased cardiac output, lung volume, oxygen storage and reduced muscle sympathetic nerve activity, while central apnea to respiratory muscle rest and hypoxia-induced erythropoiesis. 2) The use of positive airway pressure is just a wrong treatment for PB/CSR. If this is the case, the search for novel potential alternative treatment approaches is mandatory in HF. Areas covered This review will focus on the crucial issue of whether PB/CSR should be treated or not in HF, first by outlining the ideal design of pathophysiological studies to test the Naughton's hypothesis and second by summarizing the treatment strategies so far proposed for PB/CSR in HF and identifying the most promising options to be tested in future RCTs. Expert commentary It is likely that PB/CSR may be compensatory in some cases, but after a certain threshold (to be defined) it becomes maladaptive with negative prognostic meaning in HF. The development of a pathophysiologically based treatment targeting feedback resetting and neurohormonal activation underlying PB/CSR is likely to be the best option to obtain survival benefits in HF.

Adaptive servo-ventilation therapy reduces hospitalization rate in patients with severe heart failure

INTRODUCTION

Adaptive servo-ventilation (ASV) therapy is a recently developed non-pharmacological therapy that has been reported to improve cardiac function and survival in patients with severe congestive heart failure (CHF). However, a recent large randomized study suggested that ASV does not improve survival in patients with reduced ejection fraction. It remains unclear whether ASV treatment can reduce the hospitalization rate of CHF patients. We thus examined the frequency of hospital admission before and after initiation of ASV therapy in patients with CHF.

METHODS AND RESULTS

Hospitalization frequencies during the 12months before and 12months after initiation of ASV therapy (24 consecutive months) were retrospectively compared in 44 consecutive patients with severe CHF. The admission frequency decreased from 1.9±1.4 admissions in the 12months before ASV to 1.1±1.6 admissions in the 12months after ASV initiation (P<0.001). The decrease tended to be greater in those patients with more frequent hospitalizations before ASV initiation.

CONCLUSION

ASV therapy reduces hospital admissions in patients with severe CHF who are receiving maximum medical treatment.

Comorbidities in Heart Failure

Comorbidities frequently accompany chronic heart failure (HF), contributing to increased morbidity and mortality, and an impaired quality of life. We describe the prevalence of several high-impact comorbidities in chronic HF patients and their impact on morbidity and mortality. Furthermore, we try to explain the underlying pathophysiological processes and the complex interaction between chronic HF and specific comorbidities. Although common risk factors are likely to contribute, it is reasonable to believe that factors associated with HF might cause other comorbidities and vice versa. Potential factors are inflammation, neurohormonal activation, and hemodynamic changes.