Benefit of buspirone on chemoreflex and central apnoeas in heart failure: a randomized controlled crossover trial

Association of hypoxic burden metrics with cardiovascular outcomes in heart failure and sleep-disordered breathing

AIMS

Heart failure (HF) and sleep-disordered breathing (SDB) frequently coexist. We aimed to compare the prognostic value of different nocturnal hypoxic burden metrics in hospitalized HF patients.

METHODS AND RESULTS

HF patients underwent polygraphy screening for SDB in this prospective cohort. Hypoxic burden metrics assessed using pulse oximetry included time < 90% oxygen saturation (T90), proportion of total recording time < 90% oxygen saturation (TRT90), oxygen desaturation index (ODI), and mean oxygen saturation (meanSO2 ). The prespecified endpoints were the composite of cardiovascular death or admission for worsening HF. This study included 764 hospitalized HF patients, 16.5% and 36.6% of whom had obstructive and central sleep apnoea, respectively. With a median follow-up time of 2.2 years, endpoint events occurred in 410 (53.7%) patients. In univariate and multivariate analyses, T90, TRT90, and meanSO2 were substantially associated with the composite outcome, whereas ODI was not. After multivariate Cox model adjustment, patients with 5.0 ≤ T90 ≤ 52.0 min [hazard ratio (HR) 1.32, 95% confidence interval (CI): 1.02-1.71, P = 0.034] or T90 > 52.0 min (HR 1.56, 95% CI: 1.21-2.02, P = 0.001) had a greater risk of the composite outcome than those with T90 < 5.0 min. The TRT90 and T90 results were similar. Compared with meanSO2  > 95%, meanSO2  < 93% (HR 1.47, 95% CI: 1.16-1.88, P = 0.002) was correlated with adverse outcomes.

CONCLUSIONS

The hypoxic burden metrics T90, TRT90, and meanSO2 , but not ODI, were independent predictors of cardiovascular death or readmission for worsening HF. Indicators of duration and severity, not just the frequency of nocturnal hypoxaemia, should be valued and considered for intervention to improve outcomes in HF patients.

Associations between insomnia medications and risk of death by suicide

PURPOSE

Insomnia is a modifiable risk factor for suicide often treated with medications. However, little is known about the associations between insomnia medications and risk of death by suicide. The purpose of this study is to model the comparative risk of suicide by each insomnia medication compared to zolpidem, a sedative-hypnotic approved for insomnia.

METHODS

First prescription fills of medications commonly used to treat insomnia were identified in electronic medical records. Date and cause of death were identified in death certificates. Cox proportional hazards models were used to analyze time from insomnia prescription to suicide.

RESULTS

More than 2 million patients filled a new insomnia prescription between 2005 and 2015, and 518 of them died by suicide within 12 months. Compared to zolpidem, the tricyclic antidepressants (amitriptyline, doxepin) were associated with a 64% lower risk of suicide (HR 0.36 (95% CI 0.22-0.66) and the sedating antihistamines (hydroxyzine, diphenhydramine) a 40% lower risk of suicide (HR 0.60 (0.41-0.89)). In contrast, the tetracyclic antidepressant (mirtazapine) was associated with a 62% higher risk of suicide (HR 1.62 (95% CI 1.10-2.38) compared to zolpidem.

CONCLUSION

Insomnia is a modifiable risk factor for suicide, yet many medications used to treat insomnia have never been tested for the indication in clinical trials. To define efficacy in the prevention of suicide, trials are warranted.

Sleep and Breathing Conference highlights 2023: a summary by ERS Assembly 4

This paper presents some of the highlights of the Sleep and Breathing Conference 2023 https://bit.ly/46MxJml.

Autonomic and respiratory consequences of altered chemoreflex function: clinical and therapeutic implications in cardiovascular diseases

The importance of chemoreflex function for cardiovascular health is increasingly recognized in clinical practice. The physiological function of the chemoreflex is to constantly adjust ventilation and circulatory control to match respiratory gases to metabolism. This is achieved in a highly integrated fashion with the baroreflex and the ergoreflex. The functionality of chemoreceptors is altered in cardiovascular diseases, causing unstable ventilation and apnoeas and promoting sympathovagal imbalance, and it is associated with arrhythmias and fatal cardiorespiratory events. In the last few years, opportunities to desensitize hyperactive chemoreceptors have emerged as potential options for treatment of hypertension and heart failure. This review summarizes up to date evidence of chemoreflex physiology/pathophysiology, highlighting the clinical significance of chemoreflex dysfunction, and lists the latest proof of concept studies based on modulation of the chemoreflex as a novel target in cardiovascular diseases.

Transvenous phrenic nerve stimulation for the treatment of central sleep apnea reduces episodic hypoxemic burden

STUDY OBJECTIVES

To determine the effect of transvenous phrenic nerve stimulation (TPNS) on the composition of the nocturnal hypoxemic burden in patients with CSA.

METHODS

We analysed oximetry data from baseline and follow-up overnight polysomnograms (PSG) in 134 CSA patients with implanted TPNS randomised (1:1) to neurostimulation (treatment group; TPNS on) or no stimulation (control group; TPNS off) from the remedē System Pivotal Trial. The hypoxemic burden was quantified using a battery of metrics, including the oxygen desaturation index (ODI), the relative sleep time spent below 90% SpO2 (T90) due to acute episodic desaturations (T90_desat) and due to non-specific and non-cyclic drifts of SpO2 (T90_non-specific). Mean change from baseline is provided.

RESULTS

TPNS titrated to reduce respiratory events significantly reduced the ODI in the treatment group by -15.85 h^-1 ± 1.99 compared to the control group, which increased 1.32 h^-1 ± 1.85 (p 〈0001) and shortened the relative T90 duration by -3.81 percentage points ± 1.23 vs. 0.49 percentage points ± 1.14 increase (p = 0.012). This shortening of T90 was primarily accomplished by reducing the brief cyclic desaturations (T90_desaturation: -4.32 percentage points ± 0.98 vs. 0.52 percentage points ± 0.91, p = 0.0004) while notable non-specific drifts in SpO₂ remained unchanged (T90_non-specific: 0.18 percentage points ± 0.62 vs. -0.13 percentage points ± 0.57, p = 0.72).

CONCLUSIONS

TPNS appears to significantly reduce the nocturnal hypoxemic burden due to sleep-disordered breathing, but a considerable nocturnal hypoxemic burden from other sources remains. Further investigations are warranted to identify the best strategy to reduce the nocturnal hypoxemic burden beyond preventing respiratory events.

Pharmacological treatment for central sleep apnoea in adults

BACKGROUND

The term central sleep apnoea (CSA) encompasses diverse clinical situations where a dysfunctional drive to breathe leads to recurrent respiratory events, namely apnoea (complete absence of ventilation) and hypopnoea sleep (insufficient ventilation) during sleep. Studies have demonstrated that CSA responds to some extent to pharmacological agents with distinct mechanisms, such as sleep stabilisation and respiratory stimulation. Some therapies for CSA are associated with improved quality of life, although the evidence on this association is uncertain. Moreover, treatment of CSA with non-invasive positive pressure ventilation is not always effective or safe and may result in a residual apnoea-hypopnoea index.

OBJECTIVES

To evaluate the benefits and harms of pharmacological treatment compared with active or inactive controls for central sleep apnoea in adults.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 30 August 2022.

SELECTION CRITERIA

We included parallel and cross-over randomised controlled trials (RCTs) that evaluated any type of pharmacological agent compared with active controls (e.g. other medications) or passive controls (e.g. placebo, no treatment or usual care) in adults with CSA as defined by the International Classification of Sleep Disorders 3rd Edition. We did not exclude studies based on the duration of intervention or follow-up. We excluded studies focusing on CSA due to periodic breathing at high altitudes.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were central apnoea-hypopnoea index (cAHI), cardiovascular mortality and serious adverse events. Our secondary outcomes were quality of sleep, quality of life, daytime sleepiness, AHI, all-cause mortality, time to life-saving cardiovascular intervention, and non-serious adverse events. We used GRADE to assess certainty of evidence for each outcome.

MAIN RESULTS

We included four cross-over RCTs and one parallel RCT, involving a total of 68 participants. Mean age ranged from 66 to 71.3 years and most participants were men. Four trials recruited people with CSA associated with heart failure, and one study included people with primary CSA. Types of pharmacological agents were acetazolamide (carbonic anhydrase inhibitor), buspirone (anxiolytic), theophylline (methylxanthine derivative) and triazolam (hypnotic), which were given for between three days and one week. Only the study on buspirone reported a formal evaluation of adverse events. These events were rare and mild. No studies reported serious adverse events, quality of sleep, quality of life, all-cause mortality, or time to life-saving cardiovascular intervention. Carbonic anhydrase inhibitors versus inactive control Results were from two studies of acetazolamide versus placebo (n = 12) and acetazolamide versus no acetazolamide (n = 18) for CSA associated with heart failure. One study reported short-term outcomes and the other reported intermediate-term outcomes. We are uncertain whether carbonic anhydrase inhibitors compared to inactive control reduce cAHI in the short term (mean difference (MD) -26.00 events per hour, 95% CI -43.84 to -8.16; 1 study, 12 participants; very low certainty). Similarly, we are uncertain whether carbonic anhydrase inhibitors compared to inactive control reduce AHI in the short term (MD -23.00 events per hour, 95% CI -37.70 to 8.30; 1 study, 12 participants; very low certainty) or in the intermediate term (MD -6.98 events per hour, 95% CI -10.66 to -3.30; 1 study, 18 participants; very low certainty). The effect of carbonic anhydrase inhibitors on cardiovascular mortality in the intermediate term was also uncertain (odds ratio (OR) 0.21, 95% CI 0.02 to 2.48; 1 study, 18 participants; very low certainty). Anxiolytics versus inactive control Results were based on one study of buspirone versus placebo for CSA associated with heart failure (n = 16). The median difference between groups for cAHI was -5.00 events per hour (IQR -8.00 to -0.50), the median difference for AHI was -6.00 events per hour (IQR -8.80 to -1.80), and the median difference on the Epworth Sleepiness Scale for daytime sleepiness was 0 points (IQR -1.0 to 0.00). Methylxanthine derivatives versus inactive control Results were based on one study of theophylline versus placebo for CSA associated with heart failure (n = 15). We are uncertain whether methylxanthine derivatives compared to inactive control reduce cAHI (MD -20.00 events per hour, 95% CI -32.15 to -7.85; 15 participants; very low certainty) or AHI (MD -19.00 events per hour, 95% CI -30.27 to -7.73; 15 participants; very low certainty). Hypnotics versus inactive control Results were based on one trial of triazolam versus placebo for primary CSA (n = 5). Due to very serious methodological limitations and insufficient reporting of outcome measures, we were unable to draw any conclusions regarding the effects of this intervention.

AUTHORS' CONCLUSIONS

There is insufficient evidence to support the use of pharmacological therapy in the treatment of CSA. Although small studies have reported positive effects of certain agents for CSA associated with heart failure in reducing the number of respiratory events during sleep, we were unable to assess whether this reduction may impact the quality of life of people with CSA, owing to scarce reporting of important clinical outcomes such as sleep quality or subjective impression of daytime sleepiness. Furthermore, the trials mostly had short-term follow-up. There is a need for high-quality trials that evaluate longer-term effects of pharmacological interventions.

Induction of Day-Time Periodic Breathing is Associated With Augmented Reflex Response From Peripheral Chemoreceptors in Male Patients With Systolic Heart Failure

Spontaneous day-time periodic breathing (sPB) constitutes a common phenomenon in systolic heart failure (HF). However, it is unclear whether PB during wakefulness could be easily induced and what are the physiological and clinical correlates of patients with HF in whom PB induction is possible. Fifty male HF patients (age 60.8 ± 9.8 years, left ventricle ejection fraction 28.0 ± 7.4%) were prospectively screened and 46 enrolled. After exclusion of patients with sPB the remaining underwent trial of PB induction using mild hypoxia (stepwise addition of nitrogen gas to breathing mixture) which resulted in identification of inducible (iPB) in 51%. All patients underwent assessment of hypoxic ventilatory response (HVR) using transient hypoxia and of hypercapnic ventilatory response (HCVR) employing Read’s rebreathing method. The induction trial did not result in any adverse events and minimal SpO₂ during nitrogen administration was ∼85%. The iPB group (vs. non-inducible PB group, nPB) was characterized by greater HVR (0.90 ± 0.47 vs. 0.50 ± 0.26 L/min/%; p <0.05) but comparable HCVR (0.88 ± 0.54 vs. 0.67 ± 0.68 L/min/mmHg; p = NS) and by worse clinical and neurohormonal profile. Mean SpO₂ which induced first cycle of PB was 88.9 ± 3.7%, while in sPB mean SpO₂ preceding first spontaneous cycle of PB was 96.0 ± 2.5%. There was a reverse relationship between HVR and the relative variation of SpO₂ during induced PB (r = −0.49, p = 0.04). In summary, PB induction is feasible and safe in HF population using simple and standardized protocol employing incremental, mild hypoxia. Pathophysiology of iPB differs from sPB, as it relies mostly on overactive peripheral chemoreceptors. At the same time enhanced HVR might play a protective role against profound hypoxia during iPB.

Effects of Sacubitril-Valsartan on Clinical, Echocardiographic, and Polygraphic Parameters in Patients Affected by Heart Failure With Reduced Ejection Fraction and Sleep Apnea

Background

Heart failure with reduced ejection fraction (HFrEF) is a clinical condition frequently diagnosed in clinical practice. In patients affected by HFrEF, sleep apnea (SA) can be detected among the most frequent comorbidities. Sacubitril–valsartan (sac/val) association has been proven to be effective in reducing disease progression and all-cause mortality in HFrEF patients. Sac/val treatment can potentially attenuate SA development via several pathophysiologic mechanisms, including improvement of global hemodynamics, reduction of extracellular fluid overload, and decrease of sympathetic neural activity.

Methods

We recruited 132 patients affected by HFrEF and SA, already under treatment with continuous positive airway pressure (CPAP), which was discontinued 24 h before the scheduled study timepoints. Physical examination, echocardiography, nocturnal cardio-respiratory monitoring, and laboratory tests were performed in each patient at baseline and after a 6-month treatment with sac/val.

Results

After 6 months, sac/val induced statistically significant changes in clinical, hemodynamic, biohumoral (NT-proBNP, serum electrolytes, creatinine, and uric acid), and echocardiographic parameters. In particular, cardiac index (CI), both atrial and ventricular volumes and global longitudinal strain (GLS) improved. Moreover, polysomnography, carried out during a temporary CPAP interruption, revealed a significant reduction in global apnea-hypopnea index (AHI) value (p < 0.0001), central AHI (p < 0.0001), obstructive AHI (p < 0.0001), oxygen desaturation index (ODI) (p < 0.0001), and percentage time of saturation below 90% (TC90) (p < 0.0001). The changes of CI, estimated glomerular filtration rate (eGFR), NT-proBNP, and tricuspid annular plane excursion (TAPSE) contributed to 23.6, 7.6, 7.3, and 4.8% of AHI variability, respectively, and the whole model accounted for a 43.3% of AHI variation.

Conclusions

Our results suggest that treatment with sac/val is able to significantly improve the cardiorespiratory performance of patients with HFrEF and SA, integrating the positive impact of CPAP. Thus, both CPAP and sac/val therapy may synergistically contribute to lower the risks of both cardiac and pulmonary complications in HFrEF patients with SA.

Central Apneas Are More Detrimental in Female Than in Male Patients With Heart Failure

Background

Central apneas (CA) are a frequent comorbidity in patients with heart failure (HF) and are associated with worse prognosis. The clinical and prognostic relevance of CA in each sex is unknown.

Methods and Results

Consecutive outpatients with HF with either reduced or mildly reduced left ventricular ejection fraction (n=550, age 65±12 years, left ventricular ejection fraction 32%±9%, 21% women) underwent a 24‐hour ambulatory polygraphy to evaluate CA burden and were followed up for the composite end point of cardiac death, appropriate implantable cardioverter‐defibrillator shock, or first HF hospitalization. Compared with men, women were younger, had higher left ventricular ejection fraction, had lower prevalence of ischemic etiology and of atrial fibrillation, and showed lower apnea‐hypopnea index (expressed as median [interquartile range]) at daytime (3 [0–9] versus 10 [3–20] events/hour) and nighttime (10 [3–21] versus 23 [11–36] events/hour) (all P<0.001), despite similar neurohormonal activation and HF therapy. Increased chemoreflex sensitivity to either hypoxia or hypercapnia (evaluated in 356 patients, 65%, by a rebreathing test) was less frequent in women (P<0.001), but chemoreflex sensitivity to hypercapnia was a predictor of apnea‐hypopnea index in both sexes. At adjusted survival analysis, daytime apnea‐hypopnea index ≥15 events/hour (hazard ratio [HR], 2.70; 95% CI, 1.06–7.34; P=0.037), nighttime apnea‐hypopnea index ≥15 events/hour (HR, 2.84; 95% CI, 1.28–6.32; P=0.010), and nighttime CA index ≥10 events/hour (HR, 5.01; 95% CI, 1.88–13.4; P=0.001) were independent predictors of the primary end point in women but not in men (all P>0.05), also after matching women and men for possible confounders.

Conclusions

In chronic HF, CA are associated with a greater risk of adverse events in women than in men.

Central sleep apnea

Central apnea syndrome is a disorder with protean manifestations and concomitant conditions. It can occur as a distinct clinical entity or as part of another clinical syndrome. The pathogenesis of central sleep apnea (CSA) varies depending on the clinical condition. Sleep-related withdrawal of the ventilatory drive to breathe is the common denominator among all cases of central apnea, whereas hypocapnia is the final common pathway leading to apnea in the majority of central apnea. Medical conditions most closely associated with CSA include heart failure, stroke, spinal cord injury, and opioid use, among others. Nocturnal polysomnography is the standard diagnostic method, including measurement of sleep and respiration. The latter includes detection of flow, measurement of oxyhemoglobin saturation and detection of respiratory effort. Management strategy incorporates clinical presentation, associated conditions, and the polysomnographic findings in an individualized manner. The pathophysiologic heterogeneity may explain the protean clinical manifestations and the lack of a single effective therapy for all patients. While research has enhanced our understanding of the pathogenesis of central apnea, treatment options are extrapolated from treatment of obstructive sleep apnea. Co-morbid conditions and concomitant obstructive sleep apnea influence therapeutic approach significantly. Therapeutic options include positive pressure therapy, pharmacologic therapy, and supplemental Oxygen. Continuous positive airway pressure (CPAP) is the initial standard of care, although the utility of other modes of positive pressure therapy, as well as pharmacotherapy and device-based therapies, are currently being investigated.

Speckle tracking echocardiography in heart failure development and progression in patients with apneas

Obstructive (OA) and central apneas (CA) are highly prevalent breathing disorders that have a negative impact on cardiac structure and function; while OA promote the development of progressive cardiac alterations that can eventually lead to heart failure (HF), CA are more prevalent once HF ensues. Therefore, the early identification of the deleterious effects of apneas on cardiac function, and the possibility to detect an initial cardiac dysfunction in patients with apneas become relevant. Speckle tracking echocardiography (STE) imaging has become increasingly recognized as a method for the early detection of diastolic and systolic dysfunction, by the evaluation of left atrial and left and right ventricular global longitudinal strain, respectively. A growing body of evidence is available on the alterations of STE in OA, while very little is known with regard to CA. In this review, we discuss the current knowledge and gap of evidence concerning apnea-related STE alterations in the development and progression of HF.

Mapping dependencies of BOLD signal change to end-tidal CO2: linear and nonlinear modeling, and effect of physiological noise correction

BACKGROUND

Disentangling physiological noise and signal of interest is a major issue when evaluating BOLD-signal changes in response to breath holding. Currently-adopted approaches for retrospective noise correction are general-purpose, and have non-negligible effects in studies on hypercapnic challenges.

NEW METHOD

We provide a novel approach to the analysis of specific and non-specific BOLD-signal changes related to end-tidal CO₂ (P_ETCO₂) in breath-hold fMRI studies. Multiple-order nonlinear predictors for P_ETCO₂ model a region-dependent nonlinear input-output relationship hypothesized in literature and possibly playing a crucial role in disentangling noise. We explore Retrospective Image-based Correction (RETROICOR) effects on the estimated BOLD response, applying our analysis both with and without RETROICOR and analyzing the linear and non-linear correlation between P_ETCO₂ and RETROICOR regressors.

RESULTS

The RETROICOR model of noise related to respiratory activity correlated with P_ETCO₂ both linearly and non-linearly. The correction affected the shape of the estimated BOLD response to hypercapnia but allowed to discard spurious activity in ventricles and white matter. Activation clusters were best detected using non-linear components in the BOLD response model.

COMPARISON WITH EXISTING METHOD

We evaluated the side-effects of standard physiological noise correction procedure, tailoring our analysis on challenging understudied brainstem and subcortical regions. Our novel approach allowed to characterize delays and non-linearities in BOLD response.

CONCLUSIONS

RETROICOR successfully avoided false positives, still broadly affecting the estimated non-linear BOLD responses. Non-linearities in the model better explained CO₂-related BOLD signal fluctuations. The necessity to modify the standard procedure for physiological-noise correction in breath-hold studies was addressed, stating its crucial importance.

Breath-hold task induces temporal heterogeneity in electroencephalographic regional field power in healthy subjects

We demonstrated that changes in CO₂ values cause oscillations in the cortical activity in δ-and α-bands. The analysis of the regional field power (RFP) showed evidence that different cortical areas respond with different time delays to CO₂ challenges. An opposite behavior was found for the end-tidal O₂. We suppose that the different cortical time delays likely expresse specific ascending pathways to the cortex, generated by chemoreceptor nuclei in the brain stem. Although the brain stem is in charge of the automatic control of ventilation, the cortex is involved in the voluntary control of breathing but also receives inputs from the brain stem, which influences the perception of breathing, the arousal state and sleep architecture in conditions of hypoxia/hypercapnia. We evaluated in 11 healthy subjects the effects of breath hold (BH; 30 s of apneas and 30 s of normal breathing) and BH-related CO₂/O₂ changes on electroencephalogram (EEG) global field power (GFP) and RFP in nine different areas (3 rostrocaudal sections: anterior, central, and posterior; and 3 sagittal sections: left, middle, and right) in the δ- and α-bands by cross correlation analysis. No significant differences were observed in GFP or RFP when comparing free breathing (FB) with the BH task. Within the BH task, the shift from apnea to normal ventilation was accompanied by an increase in the δ-power and a decrease in the α-power. The end-tidal pressure of CO₂ ([Formula: see text]) was positively correlated with the δ-band and negatively with the α- band with a positive time shift, whereas an opposite behavior was found for the end-tidal pressure of O₂ ([Formula: see text]). Notably, the time shift between [Formula: see text] / [Formula: see text] signals and cortical activity at RFP was heterogenous and seemed to follow a hierarchical activation, with the δ-band responding earlier than the α-band. Overall, these findings suggest that the effect of BH on the cortex may follow specific ascending pathways from the brain stem and be related to chemoreflex stimulation.NEW & NOTEWORTHY We demonstrated that the end tidal CO₂ oscillation causes oscillations of delta and alpha bands. The analysis of the regional field power showed that different cortical areas respond with different time delays to CO₂ challenges. An opposite behavior was found for the end-tidal O₂. We can suppose that the different cortical time delay response likely expresses specific ascending pathways to the cortex generated by chemoreceptor nuclei in the brainstem.