Cheyne-Stokes respiration in heart failure: cycle length is dependent on left ventricular ejection fraction

A mathematical model of Cheyne-Stokes or periodic breathing

Cheyne-Stokes Breathing is a periodic cycle of apnea followed by hyperventilation. A theory of this phenomenon is developed based on a minimal set of physiological assumptions. The rate of loss of CO2 from venous blood is proportional to the CO2 concentration in the lungs times the respiration rate; the respiration rate is a linear function of arterial CO2 concentration above a threshold, and zero below that threshold. A time delay between blood in lungs and respiratory response allows the system to go into oscillation. These assumptions lead to a single nonanalytic delay-differential equation containing only three parameters, which we call respiratory recovery coefficients, (α,β,γ). A detailed study of the solutions to this equation is presented here. For β below a first threshold, breathing becomes steady, and any disturbance recovers exponentially to the steady state (∼overdamped oscillator). Above the first threshold, breathing recovers to the steady state by decaying oscillations (∼underdamped oscillator). Above a second threshold, oscillations grow to reach a limit cycle, and when that cycle is sufficiently large, it represents the Cheyne-Stokes cycle of hyperventilation and apnea. Fourier analysis shows that the transition to growing oscillations is a forward or soft Hopf bifurcation. In the Cheyne-Stokes region (sufficiently large β), the equation predicts the shapes of the curves representing the time-dependence of arterial CO2 and the respiration rate. From these shapes, we infer the values of the respiratory recovery coefficients for several groups of patients. With additional approximations, we infer the values of other physiological parameters, including cardiac output, CO2 chemosensitivity, and volume of blood between lungs and detectors.

Management of central sleep apnoea: a review of non-hypercapnic causes

Central sleep apnoea (CSA) is characterised by recurrent episodes of airway cessation or reduction in the absence of respiratory effort. Although CSA is less common than obstructive sleep apnoea, it shares similar symptoms. CSA can be secondary to various medical conditions, high altitude and medication exposure. CSA can also emerge during obstructive sleep apnoea therapy. There are a range of treatment options and selecting the right therapy requires an understanding of the pathophysiology of CSA. This review explores the aetiology, pathophysiology and clinical management of non-hypercapnic CSA.

Interventional management of mitral regurgitation and sleep disordered breathing: "Catching two birds with one stone"

Sleep disordered breathing (SDB), mostly constituting of obstructive and central sleep apnea (OSA and CSA, respectively), is highly prevalent in the general population, and even more among patients with cardiovascular disease, heart failure (HF) and valvular heart disease, such as mitral regurgitation (MR). The coexistence of HF, MR and SDB is associated with worse cardiovascular outcomes and increased morbidity and mortality. Pulmonary congestion, as a result of MR, can exaggerate and worsen the clinical status and symptoms of SDB, while OSA and CSA, through various mechanisms that impair left ventricular dynamics, can promote left ventricular remodelling, mitral annulus dilatation and consequently MR. Regarding treatment, positive airway pressure devices used to ameliorate symptoms in SDB also seem to result in a reduction of MR severity, MR jet fraction and an improvement of left ventricular ejection fraction. However, surgical and transcatheter interventions for MR, and especially transcatheter edge to edge mitral valve repair (TEER), seem to also have a positive effect on SDB, by reducing OSA and CSA-related severity indexes and improving symptom control. The purpose of this review is to provide a comprehensive analysis of the common pathophysiology between SDB and MR, as well as to discuss the available evidence regarding the effect of SDB treatment on MR and the effect of mitral valve surgery or transcatheter repair on both OSA and CSA.

Relationships between Heart Chamber Morphology or Function and Respiratory Parameters in Patients with HFrEF and Various Types of Sleep-Disordered Breathing

Sleep-disordered breathing (SDB), i.e., central sleep apnea (CSA) and obstructive sleep apnea (OSA), affects the prognosis of patients with heart failure with reduced ejection fraction (HFrEF). The study assessed the relationships between heart chamber size or function and respiratory parameters in patients with HFrEF and various types of SDB. The 84 participants were patients aged 68.3 ± 8.4 years (80% men) with an average left ventricular ejection fraction (LVEF) of 25.5 ± 6.85% who qualified for cardioverter-defibrillator implantation with or without cardiac resynchronization therapy. SDB, defined by an apnea-hypopnea index (AHI) ≥ five events/hour, was diagnosed in 76 patients (90.5%); SDB was severe in 31 (36.9%), moderate in 26 (31.0%), and mild in 19 (22.6%). CSA was the most common type of SDB (64 patients, 76.2%). A direct proportional relationship existed only in the CSA group between LVEF or stroke volume (SV) and AHI (p = 0.02 and p = 0.07), and between LVEF or SV and the percentage of total sleep time spent with hemoglobin oxygen saturation < 90% (p = 0.06 and p = 0.07). In contrast, the OSA group was the only group in which right ventricle size showed a positive relationship with AHI (for basal linear dimension [RVD1] p = 0.06), mean duration of the respiratory event (for RVD1 p = 0.03, for proximal outflow diameter [RVOT proximal] p = 0.009), and maximum duration of respiratory event (for RVD1 p = 0.049, for RVOT proximal p = 0.006). We concluded that in HFrEF patients, SDB severity is related to LV systolic function and SV only in CSA, whereas RV size correlates primarily with apnea/hypopnea episode duration in OSA.

Effects of hyperventilation length on muscle sympathetic nerve activity in healthy humans simulating periodic breathing

Background: Periodic breathing (PB) is a cyclical breathing pattern composed of alternating periods of hyperventilation (hyperpnea, HP) and central apnea (CA). Differences in PB phenotypes mainly reside in HP length. Given that respiration modulates muscle sympathetic nerve activity (MSNA), which decreases during HP and increases during CA, the net effects of PB on MSNA may critically depend on HP length.

Objectives: We hypothesized that PB with shorter periods of HP is associated with increased MSNA and decreased heart rate variability.

Methods: 10 healthy participants underwent microelectrode recordings of MSNA from the common peroneal nerve along with non-invasive recording of HRV, blood pressure and respiration. Following a 10-min period of tidal breathing, participants were asked to simulate PB for 3 min following a computed respiratory waveform that emulated two PB patterns, comprising a constant CA of 20 s duration and HP of two different lengths: short (20 s) vs long (40 s). Results: Compared to (3 min of) normal breathing, simulated PB with short HP resulted in a marked increase in mean and maximum MSNA amplitude (from 3.2 ± 0.8 to 3.4 ± 0.8 µV, p = 0.04; from 3.8 ± 0.9 to 4.3 ± 1.1 µV, p = 0.04, respectively). This was paralleled by an increase in LF/HF ratio of heart rate variability (from 0.9 ± 0.5 to 2.0 ± 1.3; p = 0.04). In contrast, MSNA response to simulated PB with long HP did not change as compared to normal breathing. Single CA events consistently resulted in markedly increased MSNA (all p &lt; 0.01) when compared to the preceding HPs, while periods of HP, regardless of duration, decreased MSNA (p &lt; 0.05) when compared to normal breathing.

Conclusion: Overall, the net effects of PB in healthy subjects over time on MSNA are dependent on the relative duration of HP: increased sympathetic outflow is seen during PB with a short but not with a long period of HP.

Cheyne-Stokes Breathing as a Predictive Indicator of Heart Failure in Patients With Obstructive Sleep Apnea; A Retrospective Case Control Study Using Continuous Positive Airway Pressure Remote Monitoring Data

Objective

We conducted a retrospective case control study to examine whether remote monitoring of Cheyne-Stokes breathing (CSB) was useful for predicting the onset of heart failure (HF) in patients with obstructive sleep apnea (OSA) on continuous positive airway pressure (CPAP).

Methods

Among patients with OSA treated at our hospital, 33 patients with HF that occurred between July 2014 and May 2021 [11 patients with acute HF (AHF); 22 patients with chronic HF (CHF) exacerbation] were included in the HF group. Of the 618 stable patients, 149 patients with a 30-days average CSB rate (CSB%) ≧1% were included in the non-HF control group. The chronologic change of CSB% were compared among the AHF, CHF and Control groups. Furthermore, of the 149 patients in the non-HF control group, 44 patients were matched for CSB%, body mass index, and sex in a ratio of 1:2 to 22 patients with CHF. The average cycle length (CL) of CSB was compared among three groups: CHF in stable period (CHF-stable group), CHF in exacerbation period (CHF-exacerbation group), and control group. In addition, according to the status of HF, receiver operating characteristic (ROC) curves were generated to determine the optimal cut-off points for variation of CSB% and CL.

Results

Chronological change in CSB% among the three groups was significantly different. Standard deviation of CSB% (SD CSB%) before onset HF was significantly higher in both the AHF and CHF groups than in the control group. The CL of CSB was significantly longer in the CHF group than in the control group and was longer during the exacerbation period than during the stable period. The optimal cut-off value of CL that could differentiate patients with and without the onset of HF was 68.9 s.

Conclusion

The HF group demonstrated greater CSB variations and longer CL than the non-HF control group. Furthermore, the CL was longer during the exacerbation period of HF even in the same patient. These results suggest that remote monitoring of CPAP device data for CSB variations and CL might allow early prediction of the onset and exacerbation of HF.

Positionspapier „Schlafmedizin in der Kardiologie“, Update 2021

Es hat sich viel getan in der Welt der Schlafmedizin in der Kardiologie, weshalb eine vollwertige Überarbeitung des Positionspapiers „Schlafmedizin in der Kardiologie“ erforderlich wurde. In der aktuellen neuartigen Version finden sich nicht nur alle verfügbaren Studien, Literaturstellen und Updates zu Pathophysiologie, Diagnostik- und Therapieempfehlungen, sondern auch Ausblicke auf neue Entwicklungen und zukünftige Forschungserkenntnisse. Dieses überarbeitete Positionspapier gibt Empfehlungen für Diagnostik und Therapie von Patienten mit kardiovaskulären Erkrankungen mit schlafassoziierten Atmungsstörungen und erteilt darüber hinaus einen fundierten Überblick über verfügbare Therapien und Evidenzen, gibt aber ebenso Ratschläge wie mit Komorbiditäten umzugehen ist. Insbesondere enthält dieses überarbeitete Positionspapier aktualisierte Stellungnahmen zu schlafassoziierten Atmungsstörungen bei Patienten mit koronarer Herzerkrankung, Herzinsuffizienz, arterieller Hypertonie, aber auch für Patienten mit Vorhofflimmern. Darüber hinaus finden sich erstmals Empfehlungen zur Telemedizin als eigenes, neues Kapitel. Dieses Positionspapier bietet Kardiologen sowie Ärzten in der Behandlung von kardiovaskulären Patienten die Möglichkeit einer evidenzbasierten Behandlung der wachsend bedeutsamen und mit zunehmender Aufmerksamkeit behafteten Komorbidität schlafassoziierter Atmungsstörungen. Und nicht zuletzt besteht mit diesem neuen Positionspapier eine enge Verknüpfung mit dem neuen Curriculum Schlafmedizin der Deutschen Gesellschaft für Kardiologie, weshalb dieses Positionspapier eine Orientierung für die erworbenen Fähigkeiten des Curriculums im Umgang von kardiovaskulären Patienten mit schlafassoziierten Atmungsstörungen darstellt.

Prevalence of Sleep Disordered Breathing in Patients with Primary Mitral Regurgitation Undergoing Mitral Valve Surgery

BACKGROUND

Sleep disordered breathing (SDB) is a frequent comorbidity in cardiac disease patients. Nevertheless, the prevalence and relationship between SDB and severe primary mitral regurgitation (PMR) has not been well investigated to date.

METHODS

A cohort of 121 patients with significant PMR undergoing mitral valve surgery were prospectively enrolled and received a cardiorespiratory single night polygraphy screening using ApneaLink before surgery. Eighty-two of them underwent a follow-up examination including a follow-up single-night sleep study 3 months after surgery.

RESULTS

The mean age of patients was 65.3 ± 12.0 years. Sixty patients (49.6%) were female. The mean EuroSCORE II was 2.5 ± 2.4%. Initially, 91 (75.2%) patients presented with SDB, among whom 50.4% (46 patients, 38.0% of total cohort) were classified as moderate to severe. These patients tended to require significantly longer postoperative intensive care and mechanical ventilation. Among the 82 patients who completed follow-up exams, mitral valve surgery led to a significant reduction in relevant SDB (20.7%). The apnea-hypopnea index (from 11/h [4;18] to 4/h [3;14] (p = 0.04)), the oxygenation-desaturation index (from 8/h [3;18] to 5/h [3;12] (p = 0.008)) as well as the saturation time below 90% (from 32 min [13;86] to 18 min [5;36] (p = 0.005)), were all shown to be improved significantly.

CONCLUSION

The prevalence of SDB is very high in patients with severe primary mitral regurgitation and may contribute to postoperative complications and prolonged intensive care. A significantly reduced but still high prevalence of SDB was observed 3 months after mitral valve surgery, highlighting the bidirectional relationship between SDB and heart failure.

Low Prognostic Value of Novel Nocturnal Metrics in Patients With OSA and High Cardiovascular Event Risk: Post Hoc Analyses of the SAVE Study

BACKGROUND

Traditional methods for the quantification of OSA severity may not encapsulate potential relationships between hypoxemia in OSA and cardiovascular risk.

RESEARCH QUESTION

Do novel nocturnal oxygen saturation (Spo₂) metrics have prognostic value in patients with OSA and high cardiovascular event risk?

STUDY DESIGN AND METHODS

We conducted post hoc analyses of the Sleep Apnea Cardiovascular Endpoints (SAVE) trial. In 2687 individuals, Cox proportional hazards models that were stratified for treatment allocation were used to determine the associations between clinical characteristics, pulse oximetry-derived metrics that were designed to quantify sustained and episodic features of hypoxemia, and cardiovascular outcomes. Metrics included oxygen desaturation index, time <90% Spo₂, average Spo₂ for the entire recording (mean Spo₂), average Spo₂ during desaturation events (desaturation Spo₂), average baseline Spo₂ interpolated across episodic desaturation events (baseline Spo₂), episodic desaturation event duration and desaturation/resaturation-time ratio, and mean and SD of pulse rate.

RESULTS

Neither apnea-hypopnea index, oxygen desaturation index, nor any of the novel Spo₂ metrics were associated with the primary SAVE composite cardiovascular outcome. Mean and baseline Spo₂ were associated with heart failure (hazard ratio [HR], 0.81; 95% CI, 0.69-0.95; P = .009; and HR, 0.78; 95% CI, 0.67-0.90; P = .001, respectively) and myocardial infarction (HR, 0.86; 95% CI, 0.77-0.95; P = .003; and HR, 0.81; 95% CI, 0.73-0.90; P < .001, respectively). Desaturation duration and desaturation/resaturation time ratio, with established risk factors, predicted future heart failure (area under the curve, 0.86; 95% CI, 0.79-0.93).

INTERPRETATION

Apnea-hypopnea index and oxygen desaturation index were not associated with cardiovascular outcomes. In contrast, the pattern of oxygen desaturation was associated with heart failure and myocardial infarction. However, concomitant risk factors remained the predominant determinants for secondary cardiovascular events and thus deserve the most intensive management.

Impact of Simulated Hyperventilation and Periodic Breathing on Sympatho-Vagal Balance and Hemodynamics in Patients with and without Heart Failure

BACKGROUND

The effects of hyperventilation and hyperventilation in the context of periodic breathing (PB) on sympatho-vagal balance (SVB) and hemodynamics in conditions of decreased cardiac output and feedback resetting, such as heart failure (HF) or pulmonary arterial hypertension (PAH), are not completely understood.

OBJECTIVES

To investigate the effects of voluntary hyperventilation and simulated PB on hemodynamics and SVB in healthy subjects, in patients with systolic HF and reduced or mid-range ejection fraction (HFrEF and HFmrEF) and in patients with PAH.

METHODS

Study participants (n = 20 per group) underwent non-invasive recording of diastolic blood pressure, heart rate variability (HRV), baroreceptor-reflex sensitivity (BRS), total peripheral resistance index (TPRI) and cardiac index (CI). All measurements were performed at baseline, during voluntary hyperventilation and during simulated PB with different length of the hyperventilation phase.

RESULTS

In healthy subjects, voluntary hyperventilation led to a 50% decrease in the mean BRS slope and a 29% increase in CI compared to baseline values (p < 0.01 and p < 0.05). Simulated PB did not alter TPRI or CI and showed heterogeneous effects on BRS, but analysis of dPBV revealed decreased sympathetic drive in healthy volunteers depending on PB cycle length (p < 0.05). In HF patients, hyperventilation did not affect BRS and TPRI but increased the CI by 10% (p < 0.05). In HF patients, simulated PB left all of these parameters unaffected. In PAH patients, voluntary hyperventilation led to a 15% decrease in the high-frequency component of HRV (p < 0.05) and a 5% increase in CI (p < 0.05). Simulated PB exerted neutral effects on both SVB and hemodynamic parameters.

CONCLUSIONS

Voluntary hyperventilation was associated with sympathetic predominance and CI increase in healthy volunteers, but only with minor hemodynamic and SVB effects in patients with HF and PAH. Simulated PB had positive effects on SVB in healthy volunteers but neutral effects on SVB and hemodynamics in patients with HF or PAH.

Effects of optimized heart failure medication on central sleep apnea with Cheyne-Stokes respiration pattern in chronic heart failure with reduced left-ventricular ejection fraction

Central Sleep Apnea with Cheyne Stokes Respiration (CSA-CSR) is often diagnosed in patients with chronic heart failure (CHF). CSA-CSR displays a periodic breathing pattern with a typical waxing and waning breathing with central sleep apnea phases in between. Optimization of heart failure medication with Angiotensin receptor neprilysin inhibition (ARNi) can effect phenotypic traits of CSA-CSR indicating improvements of both, hemodynamic parameters and central chemosensitivity.

Cycle length identifies obstructive sleep apnea and central sleep apnea in heart failure with reduced ejection fraction

AIM

To clarify whether unmasking of central sleep apnea during continuous positive airway pressure (CPAP) initiation can be identified from initial diagnostic polysomnography (PSG) in patients with heart failure with reduced ejection fraction (HFREF) and obstructive sleep apnea (OSA) MATERIALS AND METHODS: Forty-three consecutive patients with obstructive sleep apnea and central sleep apnea (OSA/CSA) in HFREF were matched with 43 HFREF patients with OSA and successful CPAP initiation. Obstructive apneas during diagnostic PSG were then analyzed for cycle length (CL), ventilation length (VL), apnea length (AL), time to peak ventilation (TTPV), and circulatory delay (CD). We calculated duty ratio (DR) as the ratio of VL/CL and mathematic loop gain (LG).

RESULTS

While AL was similar, CL, VL, TTPV, CD, and DR was significantly longer in patients with OSA/CSA compared to those with OSA, and LG was significantly higher. Receiver operator curves identified optimal cutoff values of 50.2 s for CL (area under the curve (AUC) 0.85, 29.2 s for VL (AUC 0.92), 11.5 s for TTPV (AUC 0.82), 26.4 s for CD (AUC 0.79), and 3.96 (AUC 0.78)) respectively for LG to identify OSA/CSA.

CONCLUSION

OSA/CSA in HFREF can be identified by longer CL, VL, TTPV, and CD from obstructive events in initial diagnostic PSG. The underlying mechanisms seem to be the presence of an increased LG.

ResCSRF: Algorithm to Automatically Extract Cheyne-Stokes Respiration Features From Respiratory Signals

OBJECTIVE

Cheyne-Stokes respiration (CSR) related features are significantly associated with cardiac dysfunction. Scoring of these features is labor intensive and time-consuming. To automate the scoring process, an algorithm (ResCSRF) has been developed to extract these features from nocturnal measurement of respiratory signals.

METHODS

ResCSRF takes four signals (nasal flow, thorax, abdomen, and finger oxygen saturation) as input. It first detects CSR cycles and then calculates the respiratory features (cycle length, lung-to-periphery circulation time, and time to peak flow). It outputs nightly statistics (mean, median, standard deviation, and percentiles) of these features. It was developed and blindly tested on a group of 49 chronic heart failure patients undergoing overnight in-home unattended respiratory polygraphy recordings.

RESULTS

The performance of ResCSRF was evaluated against manual expert scoring (ES) (consensus between two independent sleep scorers). In terms of percentage of CSR per recording, the mean difference [reproducibility coefficient (RPC)] between ResCSRF and ES was 0.5(6.4) and 0.5(8.1) for development and test set, respectively. The nightly statistics of CSR-related features output by ResCSRF showed high correlation with ES on the blind test set with the mean difference of less than 3 s and RPC of less than 7 s.

CONCLUSIONS

These results indicate that ResCSRF is capable of automating the scoring of CSR-related features and could potentially be implemented into a remote monitoring system to regularly monitor patients' cardiac function.

Ventilatory Cycle Measurements and Loop Gain in Central Apnea in Mining Drivers Exposed to Intermittent Altitude

STUDY OBJECTIVES

By measuring the apnea length, ventilatory phase, respiratory cycle length, and loop gain, we can further characterize the central apneas of high altitude (CAHA).

METHODS

Sixty-three drivers of all-terrain vehicles, working in a Peruvian mine located at 2,020 meters above sea level (MASL), were evaluated. A respiratory polygraph was performed in the first night they slept at high altitude. None of the subjects were exposed to oxygen during the test or acetazolamide in the preceding days of the test.

RESULTS

Sixty-three respiratory polygraphs were performed, and 59 were considered for analysis. Forty-six (78%) were normal, 6 (10%) had OSA, and 7 (12%) had CAHA. Key data from subjects include: residing altitude: 341 ± 828 MASL, Lake Louise scoring: 0.4 ± 0.8, Epworth score: 3.4 ± 2.7, apneahypopnea index: 35.7 ± 19.3, CA index: 13.4 ± 14.2, CA length: 14.4 ± 3.6 sec, ventilatory length: 13.5 ± 2.9 sec, cycle length: 26.5 ± 4.0 sec, ventilatory length/CA length ratio 0.9 ± 0.3 and circulatory delay 13.3 ± 2.9 sec. Duty ratio media [ventilatory duration/cycle duration] was 0.522 ± 0 0.128 [0.308-0.700] and loop gain was calculated from the duty ratio utilizing this formula: LG = 2π / [(2πDR-sin(2πDR)]. All subjects have a high loop gain media 2.415 ± 1.761 [1.175-6.260]. Multiple correlations were established with loop gain values, but the only significant correlation detected was between central apnea index and loop gain.

CONCLUSIONS

Twelve percent of the studied population had CAHA. Measurements of respiratory cycle in workers with CAHA are more similar to idiopathic central apneas rather than Hunter-Cheyne-Stokes respiration. Also, there was a high degree of correlation between severity of central apnea and the degree of loop gain. The abnormal breathing patterns in those subjects could affect the sleep quality and potentially increase the risk for work accidents.

CSA Is Not Beneficial Long Term in Heart Failure Patients with Reduced Ejection Fraction

Central sleep apnea (CSA) affects many patients, with heart failure and results in hypoxia and nor-epinephrine release and is associated with high morbidity and mortality. Recent trials in the treatment of CSA using positive airway pressure therapies have failed to demonstrate improvement in mortality and as a result, the compensatory nature of CSA has been questioned. The detrimental effects from CSA are clear. While there may be a short term compensatory effect, the long term effects cause chronic insult to the cardiovascular system indicating that CSA should be treated, but alternative treatment options need to be considered.

Association between polymorphisms of the HSPB7 gene and Cheyne-Stokes respiration with central sleep apnea in patients with dilated cardiomyopathy and congestive heart failure

BACKGROUND

CSR-CSA is frequent in patients with CHF. Dilated cardiomyopathy (DCM) is a structural heart disease with strong genetic background, yet one of the leading etiological causes of CHF. Studies have showed that the HSPB7 gene is associated with DCM.

OBJECTIVES

We aimed to explore the prevalence of polymorphisms of the HSPB7 gene in the Chinese Han population with CSR-CSA and CHF caused by DCM.

METHODS

A total of 503 unrelated subjects of the Chinese Han population, including 283 CHF patients caused by DCM and 220 healthy controls, were involved in the study. The CHF patients were classified as the CSA-CHF group and the non-CSA-CHF group according to the PSG parameters. The rs1739843 polymorphisms of the HSPB7 gene were identified by real-time quantitative polymerase chain reaction.

RESULTS

In the present study, 35.8% of CHF patients caused by DCM had CSR-CSA. Comparison demonstrated that the CSA-CHF group had significantly higher TT genotype and T allele frequencies in the rs1739843 single nucleotide polymorphism (SNP) of the HSPB7 gene. There were no significant differences among the CC genotype distribution of the CSA-CHF group and the non-CSA-CHF group or the control group.

CONCLUSIONS

The rs1739843 polymorphism of the HSPB7 gene might be involved in the pathogenesis of CSR-CSA and CHF subjects caused by DCM in the Chinese Han population. This finding was from a genetic search for the role of the HSPB7 gene in CSR-CSA of CHF patients caused by DCM.

Single centre experience of the application of self navigated 3D whole heart cardiovascular magnetic resonance for the assessment of cardiac anatomy in congenital heart disease

BACKGROUND

For free-breathing cardiovascular magnetic resonance (CMR), the self-navigation technique recently emerged, which is expected to deliver high-quality data with a high success rate. The purpose of this study was to test the hypothesis that self-navigated 3D-CMR enables the reliable assessment of cardiovascular anatomy in patients with congenital heart disease (CHD) and to define factors that affect image quality.

METHODS

CHD patients ≥2 years-old and referred for CMR for initial assessment or for a follow-up study were included to undergo a free-breathing self-navigated 3D CMR at 1.5T. Performance criteria were: correct description of cardiac segmental anatomy, overall image quality, coronary artery visibility, and reproducibility of great vessels diameter measurements. Factors associated with insufficient image quality were identified using multivariate logistic regression.

RESULTS

Self-navigated CMR was performed in 105 patients (55% male, 23 ± 12y). Correct segmental description was achieved in 93% and 96% for observer 1 and 2, respectively. Diagnostic quality was obtained in 90% of examinations, and it increased to 94% if contrast-enhanced. Left anterior descending, circumflex, and right coronary arteries were visualized in 93%, 87% and 98%, respectively. Younger age, higher heart rate, lower ejection fraction, and lack of contrast medium were independently associated with reduced image quality. However, a similar rate of diagnostic image quality was obtained in children and adults.

CONCLUSION

In patients with CHD, self-navigated free-breathing CMR provides high-resolution 3D visualization of the heart and great vessels with excellent robustness.

Cardiac or Other Implantable Electronic Devices and Sleep-disordered Breathing - Implications for Diagnosis and Therapy

Sleep-disordered breathing (SDB) is of growing interest in cardiology because SDB is a highly prevalent comorbidity in patients with a variety of cardiovascular diseases. The prevalence of SDB is particularly high in patients with cardiac dysrhythmias and/or heart failure. In this setting, many patients now have implantable cardiac devices, such as pacemakers, implantable cardioverter-defibrillators or implanted cardiac resynchronisation therapy devices (CRT). Treatment of SDB using implantable cardiac devices has been studied previously, with atrial pacing and CRT being shown not to bring about satisfactory results in SDB care. The latest generations of these devices have the capacity to determine transthoracic impedance, to detect and quantify breathing efforts and to identify SDB. The capability of implantable cardiac devices to detect SDB is of potential importance for patients with cardiovascular disease, allowing screening for SDB, monitoring of the course of SDB in relation to cardiac status, and documenting of the effects of treatment.

A novel therapeutic approach for the treatment of central sleep apnea: The remedē® system

Central sleep apnea (CSA) occurs primarily in cardiovascular patients and is associated with high morbidity and mortality. The disorder often is unrecognized due to the overlap of symptoms with those of the underlying cardiac disease. CSA can be easily diagnosed with a sleep study. Following optimization of all co-morbidities, the therapeutic approach available currently focuses on mask-based therapies which suffer from poor patient adherence. A new therapy, the remedē® System, has been developed; it utilizes a transvenous, fully implantable system providing phrenic nerve stimulation intended to restore a more normal breathing pattern. The therapy demonstrated promising results based on an initial chronic study and a randomized trial is underway to further evaluate safety and efficacy of this novel system in patients with CSA.

Sleep disordered breathing in group 1 pulmonary arterial hypertension

STUDY OBJECTIVES

To determine the prevalence and clinical predictors of sleep disordered breathing (SDB) and impact on outcomes in a cohort of patients with WHO group 1 pulmonary arterial hypertension (PAH).

METHODS

A retrospective, cross-sectional review of 52 consecutive subjects with known WHO group 1 PAH referred for assessment of possible SDB. Subjects had overnight polysomnography within 6 months of right heart catheterization performed as part of a routine clinical protocol.

RESULTS

SDB was present in 71% of the PAH patients: 56% had OSA and 44% CSA. Older age and subjective sleepiness as assessed by the Epworth Sleepiness Scale score > 10 were predictive of SDB. A high prevalence of OSA occurred in both male (50%) and female (60%) subjects. No differences in cardiopulmonary hemodynamics or survival between those with and without SDB were observed.

CONCLUSIONS

This high prevalence of SDB in the PAH population suggests that systematic screening and testing is important in this group. Further studies are necessary to determine the pathophysiological effect of SDB and potential impact of SDB treatment in this population.

CITATION

Minic M; Granton JT; Ryan CM. Sleep disordered breathing in group 1 pulmonary arterial hypertension.

Reliability and accuracy of sleep apnea scans in novel cardiac resynchronization therapy devices: an independent report of two cases

Pacemaker apnea scan algorithms are able to screen for sleep apnea. We investigated whether these systems were able to accurately detect sleep-disordered breathing (SDB) in two patients from an outpatient clinic. The first patient suffered from ischemic heart failure and severe central sleep apnea (CSA) and underwent adaptive servoventilation therapy (ASV). The second patient suffered from dilated cardiomyopathy and moderate obstructive sleep apnea (OSA). Pacemaker read-outs did not match polysomnography (PSG) recordings well and overestimated the apnea-hypopnea index. However, ASV therapy-induced SDB improvements were adequately recognized by the apnea scan of the Boston Scientific INVIVE® cardiac resynchronization therapy pacemaker. Detection of obstructive respiratory events using impedance-based technology may underestimate the number of events, as frustrane breathing efforts induce impedance changes without significant airflow. By contrast, in the second case, apnea scan overestimated the number of total events and of obstructive events, perhaps owing to a very sensitive but less specific hypopnea definition and detection within the diagnostic algorithm of the device. These two cases show that a pacemaker apnea scan is able to reflect SDB, but PSG precision is not met by far. The device scan revealed the decline of SDB through ASV therapy for CSA in one patient, but not for OSA in the second case. To achieve reliable monitoring of SDB, further technical developments and clinical studies are necessary.

Cheyne-stokes breathing and reduced ejection fraction

BACKGROUND

The accuracy of Cheyne-Stokes breathing as a sign of left ventricular dysfunction and its overall prognostic significance are unknown.

METHODS

Between 2001 and 2006, the author examined 386 inpatients at a Department of Veterans Affairs Medical Center and compared the finding of Cheyne-Stokes breathing and its cycle length with the patients' echocardiographic ejection fraction (EF) and 5-year survival.

RESULTS

A total of 45 of 386 patients (11.7%) had Cheyne-Stokes breathing. Two variables were independently associated with Cheyne-Stokes breathing: reduced EF (P<.001) and age>80 years (P=.006). The presence of Cheyne-Stokes breathing increased the probability of a markedly reduced EF (ie, EF<40%; likelihood ratio, 5.3; 95% confidence interval, 3.1-9), especially in patients aged≤80 years (likelihood ratio, 7.8; 95% confidence interval, 3.9-15.5). The finding was present in 1 of 3 affected patients (sensitivity=34%). The correlation between cycle length and EF was poor (r=0.23, P=.14). The 5-year survival of patients with Cheyne-Stokes breathing (37.2%) was similar to that of patients without the finding (42.9%, P=.18, log-rank test).

CONCLUSIONS

In hospitalized patients, Cheyne-Stokes breathing increases the probability of left ventricular dysfunction. It is present in 1 of 3 patients with markedly reduced EF. When detected during physical examination, Cheyne-Stokes breathing does not indicate worse prognosis.

Rules for scoring respiratory events in sleep: update of the 2007 AASM Manual for the Scoring of Sleep and Associated Events. Deliberations of the Sleep Apnea Definitions Task Force of the American Academy of Sleep Medicine

The American Academy of Sleep Medicine (AASM) Sleep Apnea Definitions Task Force reviewed the current rules for scoring respiratory events in the 2007 AASM Manual for the Scoring and Sleep and Associated Events to determine if revision was indicated. The goals of the task force were (1) to clarify and simplify the current scoring rules, (2) to review evidence for new monitoring technologies relevant to the scoring rules, and (3) to strive for greater concordance between adult and pediatric rules. The task force reviewed the evidence cited by the AASM systematic review of the reliability and validity of scoring respiratory events published in 2007 and relevant studies that have appeared in the literature since that publication. Given the limitations of the published evidence, a consensus process was used to formulate the majority of the task force recommendations concerning revisions.The task force made recommendations concerning recommended and alternative sensors for the detection of apnea and hypopnea to be used during diagnostic and positive airway pressure (PAP) titration polysomnography. An alternative sensor is used if the recommended sensor fails or the signal is inaccurate. The PAP device flow signal is the recommended sensor for the detection of apnea, hypopnea, and respiratory effort related arousals (RERAs) during PAP titration studies. Appropriate filter settings for recording (display) of the nasal pressure signal to facilitate visualization of inspiratory flattening are also specified. The respiratory inductance plethysmography (RIP) signals to be used as alternative sensors for apnea and hypopnea detection are specified. The task force reached consensus on use of the same sensors for adult and pediatric patients except for the following: (1) the end-tidal PCO(2) signal can be used as an alternative sensor for apnea detection in children only, and (2) polyvinylidene fluoride (PVDF) belts can be used to monitor respiratory effort (thoracoabdominal belts) and as an alternative sensor for detection of apnea and hypopnea (PVDFsum) only in adults.The task force recommends the following changes to the 2007 respiratory scoring rules. Apnea in adults is scored when there is a drop in the peak signal excursion by ≥ 90% of pre-event baseline using an oronasal thermal sensor (diagnostic study), PAP device flow (titration study), or an alternative apnea sensor, for ≥ 10 seconds. Hypopnea in adults is scored when the peak signal excursions drop by ≥ 30% of pre-event baseline using nasal pressure (diagnostic study), PAP device flow (titration study), or an alternative sensor, for ≥ 10 seconds in association with either ≥ 3% arterial oxygen desaturation or an arousal. Scoring a hypopnea as either obstructive or central is now listed as optional, and the recommended scoring rules are presented. In children an apnea is scored when peak signal excursions drop by ≥ 90% of pre-event baseline using an oronasal thermal sensor (diagnostic study), PAP device flow (titration study), or an alternative sensor; and the event meets duration and respiratory effort criteria for an obstructive, mixed, or central apnea. A central apnea is scored in children when the event meets criteria for an apnea, there is an absence of inspiratory effort throughout the event, and at least one of the following is met: (1) the event is ≥ 20 seconds in duration, (2) the event is associated with an arousal or ≥ 3% oxygen desaturation, (3) (infants under 1 year of age only) the event is associated with a decrease in heart rate to less than 50 beats per minute for at least 5 seconds or less than 60 beats per minute for 15 seconds. A hypopnea is scored in children when the peak signal excursions drop is ≥ 30% of pre-event baseline using nasal pressure (diagnostic study), PAP device flow (titration study), or an alternative sensor, for ≥ the duration of 2 breaths in association with either ≥ 3% oxygen desaturation or an arousal. In children and adults, surrogates of the arterial PCO(2) are the end-tidal PCO(2) or transcutaneous PCO(2) (diagnostic study) or transcutaneous PCO(2) (titration study). For adults, sleep hypoventilation is scored when the arterial PCO(2) (or surrogate) is > 55 mm Hg for ≥ 10 minutes or there is an increase in the arterial PCO(2) (or surrogate) ≥ 10 mm Hg (in comparison to an awake supine value) to a value exceeding 50 mm Hg for ≥ 10 minutes. For pediatric patients hypoventilation is scored when the arterial PCO(2) (or surrogate) is > 50 mm Hg for > 25% of total sleep time. In adults Cheyne-Stokes breathing is scored when both of the following are met: (1) there are episodes of ≥ 3 consecutive central apneas and/or central hypopneas separated by a crescendo and decrescendo change in breathing amplitude with a cycle length of at least 40 seconds (typically 45 to 90 seconds), and (2) there are five or more central apneas and/or central hypopneas per hour associated with the crescendo/decrescendo breathing pattern recorded over a minimum of 2 hours of monitoring.

[Sleep-disordered breathing and cardiac arrhythmias]

Sleep-disordered breathing (SDB) is an important comorbidity in patients with cardiac arrhythmias. Previous studies confirmed associations between supraventricular and ventricular arrhythmias and SDB. In heart failure patients, SDB was also found independently associated with a shorter event-free survival to the occurrence of malignant ventricular arrhythmias requiring appropriate cardioverter-defibrillator therapy. In obstructive sleep apnea, repetitive hypoxemia, mechanical stress (wall tension), arousals from sleep, and activation of the sympathetic nervous system promote cardiac arrhythmias. Pathophysiological concepts for the link between Cheyne-Stokes respiration and malignant arrhythmias are not fully understood and require further research. In addition, large-scale, randomized, controlled trials are awaited to prove whether adequate treatment of SDB is associated with a risk reduction for the occurrence of arrhythmias, in general, and malignant ventricular arrhythmias, in particular, in these patients.

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.

Adaptive servoventilation improves cardiac function and respiratory stability

Cheyne–Stokes respiration (CSR) in patients with chronic heart failure (CHF) is of major prognostic impact and expresses respiratory instability. Other parameters are daytime pCO₂, VE/VCO₂-slope during exercise, exertional oscillatory ventilation (EOV), and increased sensitivity of central CO₂ receptors. Adaptive servoventilation (ASV) was introduced to specifically treat CSR in CHF. Aim of this study was to investigate ASV effects on CSR, cardiac function, and respiratory stability. A total of 105 patients with CHF (NYHA ≥ II, left ventricular ejection fraction (EF) ≤ 40%) and CSR (apnoea–hypopnoea index ≥ 15/h) met inclusion criteria. According to adherence to ASV treatment (follow-up of 6.7 ± 3.2 months) this group was divided into controls (rejection of ASV treatment or usage <50% of nights possible and/or <4 h/night; n = 59) and ASV (n = 56) adhered patients. In the ASV group, ventilator therapy was able to effectively treat CSR. In contrast to controls, NYHA class, EF, oxygen uptake, 6-min walking distance, and NT-proBNP improved significantly. Moreover, exclusively in these patients pCO₂, VE/VCO₂-slope during exercise, EOV, and central CO₂ receptor sensitivity improved. In CHF patients with CSR, ASV might be able to improve parameters of SDB, cardiac function, and respiratory stability.

Oligomer-mediated modulation of hTERT alternative splicing induces telomerase inhibition and cell growth decline in human prostate cancer cells

The expression of telomerase in human cells is strictly controlled by multiple mechanisms including transcription and alternative splicing of telomerase reverse transcriptase (hTERT). In this study, we demonstrated the possibility of modulating the hTERT splicing pattern in DU145 human prostate carcinoma cells through the use of 2'-O-methyl-RNA phosphorothioate oligonucleotides targeting the splicing site located between intron 5 and exon 6 in the hTERT pre-mRNA. An 18-h oligonucleotide exposure induced a decrease in the full-length hTERT transcript and a concomitant increase in the alternatively spliced transcripts, which resulted in significant inhibition of telomerase catalytic activity. Moreover, exposure to the R7 oligomer (which induced the most pronounced modulation of the hTERT splicing pattern and the greatest telomerase inhibition) caused a marked reduction in DU145 cell growth and the induction of apoptosis starting 2 days after treatment. Such data support the concept that down-regulation of hTERT expression can cause short-term effects on tumour cell growth, which are telomere-shortening independent.