Effects of acute changes in pulmonary wedge pressure on periodic breathing at rest in heart failure patients

Exercise oscillatory ventilation in patients with advanced heart failure with and without left ventricular assist device

BACKGROUND

Exercise oscillatory ventilation (EOV), indicating pathological fluctuations on pulmonary arterial pressure, is associated with mortality in patients with heart failure (HF). Whether left ventricular assist device (LVAD)-induced ventricular unloading can reverse EOV and may prevent short-term rehospitalization has not been investigated.

METHODS

We performed a retrospective single-center in- and outpatient analysis of patients with (n = 20, LVAD) and without (n = 27, HF) circulatory support and reduced ejection fraction (EF, 22.8 ± 7.9%). The association of cardiopulmonary exercise testing (CPET) variables and 3 months-rehospitalization (3MR) as a primary outcome was analyzed. Furthermore, CPET variables were compared regarding the presence of EOV (+/-).

RESULTS

Lower VO_2peak (11.6 ± 4.9 ml/kg/min vs. 14.4 ± 4.3 ml/kg/min, p = 0.039), lower increase of PETCO₂ (CI = 0.049-1.127; p = 0.068), and higher VE/VCO₂ (43.8 ± 9.5 vs. 38.3 ± 10.6; p = 0.069) were associated with 3MR. Flattening of O₂ pulse (CI = 0.139-2.379; p = 0.487) had no impact on 3MR. EOV was present in 59.5% (n = 28/47) of patients, without a significant difference between LVAD and HF patients (p = 0.959). Patients with HF/EOV+ demonstrated significantly lower VO_2peak compared with HF/EOV- (p = 0.039). LVAD/EOV+ displayed significantly lower EF (p = 0.004) and fewer aortic valve opening than LVAD/EOV- (p = 0.027).

CONCLUSIONS

Lower VO_2peak , but not EOV, was associated with 3MR. EOV occurred at a similar rate in LVAD and HF patients, which may illustrate insufficient unloading during exercise in chronic LVAD therapy and may contribute to the limited exercise capacity following LVAD implantation. Simultaneous CPET and right heart catheterization studies are needed to elucidate whether EOV may serve as a non-invasive predictor of insufficient LV unloading necessitating LVAD reprograming.

Impact of transcatheter edge-to-edge mitral valve repair on central sleep apnoea

Aims

Sleep-disordered breathing (SDB) and its subtype central sleep apnoea (CSA) are highly prevalent in patients with heart failure and associated with worse prognosis. Whereas pharmacological therapy of heart failure has been shown to ameliorate CSA, results from previous studies on the effect of mitral regurgitation therapy on SDB are contradicting. The aim of this study was to assess the impact of transcatheter edge-to-edge mitral valve repair (TEER) on prevalence and severity of CSA.

Methods and results

We enrolled 47 patients undergoing TEER for symptomatic mitral regurgitation in a prospective study. Secondary mitral regurgitation and left ventricular ejection fraction < 50% were present in 79% and 68% of patients, respectively. Respiratory polygraphy was performed before TEER in a compensated condition and four weeks after the procedure. 34 patients completed the follow-up. At baseline, 19 (56%) patients showed moderate-to-severe SDB, of whom 13 (68%) were classified as CSA. Both apnoea-hypopnoea index and percentage of recorded time spent in Cheyne-Stokes respiration strongly decreased from baseline to follow-up (median [IQR] 16 [7–30] vs. 7 [4–15] /h, p = 0.007; 6 [0–34] vs. 0 [0–8] %, p = 0.008). Median relative reduction of central apnoea index was 75% (p = 0.023), while obstructive apnoea index did not change significantly. Increase in stroke volume after TEER and high systolic pulmonary artery pressure at baseline predicted a > 50% reduction of both Apnoea-hypopnoea index and Cheyne-Stokes respiration.

Conclusion

TEER is associated with a significant short-term reduction of CSA and Cheyne-Stokes respiration in high-risk patients, strengthening its value as an effective treatment option for advanced heart failure.

Graphical abstract

Effects of β-blocker therapy on exercise oscillatory ventilation in reduced ejection fraction heart failure patients: A case series study

BACKGROUND

Exercise oscillatory ventilation (EOV) is an abnormal breathing pattern that occurs in ~20% of patients with heart failure (HF) and is associated with poor prognosis and exercise intolerance. β-blockers (βb) are prescribed for most HF patients; however, their effect on EOV remains unclear. We evaluated the effect of βb on EOV in HF patients with reduced ejection fraction (HFrEF).

METHODS

Fifteen patients diagnosed with HF, ejection fraction < 45%, aged from 18 to 65 years, were included before starting βb therapy. Patients underwent clinical evaluation, cardiopulmonary exercise testing, echocardiography, laboratory exams (norepinephrine levels, B type natriuretic peptide) at baseline and after βb therapy optimized for six months. Presence of exercise oscillatory breathing was determined by two experienced observers who were blinded to the moment of the test (pre or post).

RESULTS

Fifteen patients (1 female), aged 49.5 ± 2.5 years, with HFrEF, NYHA I-III enrolled in the study. The etiologies of the HFrEF were idiopathic (n = 8) and hypertensive (n = 7). LVEF increased after βb therapy from 25.9 ± 2.5% to 33 ± 2.6%, P = 0.02; peak VO₂ did not significantly change (21.8 ± 1.7 vs 24.7 ± 1.9, P = 0.4); VE/VCO₂ slope changed from 32.1 ± 10.6-27.5 ± 9.1, P = 0.03. Before βb initiation, nine patients (60%) had EOV, but only two (13%) did after optimized therapy. McNemar test was used to evaluate the significance of the association between the two moments (P = 0.02).

CONCLUSION

In patients with HF, medical therapy with βb can reverse EOV. This may explain why these patients experience symptom improvement after βb therapy.

Research Priorities for Patients with Heart Failure and Central Sleep Apnea. An Official American Thoracic Society Research Statement

Background: Central sleep apnea (CSA) is common among patients with heart failure and has been strongly linked to adverse outcomes. However, progress toward improving outcomes for such patients has been limited. The purpose of this official statement from the American Thoracic Society is to identify key areas to prioritize for future research regarding CSA in heart failure.

Methods: An international multidisciplinary group with expertise in sleep medicine, pulmonary medicine, heart failure, clinical research, and health outcomes was convened. The group met at the American Thoracic Society 2019 International Conference to determine research priority areas. A statement summarizing the findings of the group was subsequently authored using input from all members.

Results: The workgroup identified 11 specific research priorities in several key areas: 1) control of breathing and pathophysiology leading to CSA, 2) variability across individuals and over time, 3) techniques to examine CSA pathogenesis and outcomes, 4) impact of device and pharmacological treatment, and 5) implementing CSA treatment for all individuals

Conclusions: Advancing care for patients with CSA in the context of heart failure will require progress in the arenas of translational (basic through clinical), epidemiological, and patient-centered outcome research. Given the increasing prevalence of heart failure and its associated substantial burden to individuals, society, and the healthcare system, targeted research to improve knowledge of CSA pathogenesis and treatment is a priority.

Altered Hemodynamics and End-Organ Damage in Heart Failure: Impact on the Lung and Kidney

Heart failure is characterized by pathologic hemodynamic derangements, including elevated cardiac filling pressures ("backward" failure), which may or may not coexist with reduced cardiac output ("forward" failure). Even when normal during unstressed conditions such as rest, hemodynamics classically become abnormal during stressors such as exercise in patients with heart failure. This has important upstream and downstream effects on multiple organ systems, particularly with respect to the lungs and kidneys. Hemodynamic abnormalities in heart failure are affected by processes that extend well beyond the cardiac myocyte, including important roles for pericardial constraint, ventricular interaction, and altered venous capacity. Hemodynamic perturbations have widespread effects across multiple heart failure phenotypes, ranging from reduced to preserved ejection fraction, acute to chronic disease, and cardiogenic shock to preserved perfusion states. In the lung, hemodynamic derangements lead to the development of abnormalities in ventilatory control and efficiency, pulmonary congestion, capillary stress failure, and eventually pulmonary vascular disease. In the kidney, hemodynamic perturbations lead to sodium and water retention and worsening renal function. Improved understanding of the mechanisms by which altered hemodynamics in heart failure affect the lungs and kidneys is needed in order to design novel strategies to improve clinical outcomes.

Mitigation of Exercise Oscillatory Ventilation Score by Cardiac Resynchronization Therapy

BACKGROUND

Exercise oscillatory ventilation (EOV) is a consequence of ventilatory control system instability and is commonly observed in patients with advanced heart failure (HF); it is associated with adverse prognosis. The goal of this study was to evaluate the effects of cardiac resynchronization therapy (CRT) on oscillatory ventilation as quantified by a proposed EOV score.

METHODS AND RESULTS

Consecutive patients with HF (N = 35) who underwent clinically indicated CRT, cardiopulmonary exercise testing and carbon dioxide (CO₂) chemosensitivity by rebreathe before and 4-6 months after CRT were included in this post hoc analysis. With CRT, EOV scores improved in 22 patients (63%). In these patients, left ventricular ejection fraction, left atrial volume, brain natriuretic peptide concentration, and CO₂ chemosensitivity significantly improved after CRT (P < 0.05). Furthermore, minute ventilation per unit CO₂ production significantly decreased, and end-tidal CO₂ increased at rest and at peak exercise post-CRT. Multiple regression analysis showed only the change of CO₂ chemosensitivity to be significantly associated with the improvement of the EOV score (b = 0.64; F = 11.3; P = 0.004). In the group without EOV score improvement (n = 13), though left ventricular ejection fraction significantly increased with CRT (P = 0.015), no significant changes in ventilation or gas exchange were observed.

CONCLUSION

The EOV score was mitigated by CRT and was associated with decreased CO₂ chemosensitivity.

Pulmonary Limitations in Heart Failure

The heart and lungs are intimately linked. Hence, impaired function of one organ may lead to changes in the other. Accordingly, heart failure is associated with airway obstruction, loss of lung volume, impaired gas exchange, and abnormal ventilatory control. Cardiopulmonary exercise testing is an excellent tool for evaluation of gas exchange and ventilatory control. Indeed, many parameters routinely measured during cardiopulmonary exercise testing, including the level of minute ventilation per unit of carbon dioxide production and the presence of exercise oscillatory ventilation, have been found to be strongly associated with prognosis in patients with heart failure.

Assessment of Thoracic Blood Volume by Computerized Tomography in Patients With Heart Failure and Periodic Breathing

BACKGROUND

Periodic breathing (PB) is often observed in patients with HF at rest, with sleep and during exercise. However, mechanisms underlying abnormal ventilatory control are not entirely established.

METHODS

Eleven subjects with HF (10 males, age = 69 ± 12 y) and 12 age-matched control subjects (8 males, age = 65 ± 9 y) participated in the study. PB was defined as a peak in the 0.003-0.04 Hz frequency range of the flow signal during 6 minutes of awake resting breathing. Thoracic blood volumes (V_t, thorax; V_h, heart; V_p, pulmonary), mean transit times (MTTs), and extravascular lung water (EVLW) were quantified using computerized tomography.

RESULTS

PB was observed in 7 subjects with HF and was associated with worse functional status. The HF PB-present group had thoracic blood volumes nearly double those of control and HF PB-absent subjects (volumes reported as mL/m² body surface area, P values vs control: control = 813 ± 246, HF PB-absent = 822 ± 161 P = .981, HF PB-present = 1579 ± 548 P = .002). PB was associated with longer pulmonary MTT (control = 6.7 ± 1.2 s, HF PB-absent = 6.0 ± 0.8 s, HF PB-present = 8.4 ± 1.6 s; P = .033, HF PB-present vs HF PB-absent). EVLW was not elevated in the PB group.

CONCLUSIONS

Subjects with HF and PB at rest have greater centralization of blood volume.

Influence of Thoracic Fluid Compartments on Pulmonary Congestion in Chronic Heart Failure

INTRODUCTION

Pulmonary congestion is a common finding of heart failure (HF), but it remains unclear how pulmonary and heart blood volumes (V_p and V_h, respectively) and extravascular lung water (EVLW) change in stable HF and affect lung function.

METHODS

Fourteen patients with HF (age 68 ± 11 y, LVEF 33 ± 8%) and 12 control subjects (age 65 ± 9 y) were recruited. A pulmonary function test, thoracic computerized tomographic (CT) scan, and contrast perfusion scan were performed. From the thoracic scan, a histogram of CT attenuation of lung tissue was generated and skew, kurtosis, and full-width half-max (FWHM) calculated as surrogates of EVLW. Blood volumes were calculated from the transit time of the contrast through the great vessels of the heart.

RESULTS

Patients with HF had greater V_p and V_h (V_p 0.55 ± 0.21 L vs 0.41 ± 0.13 L; V_h 0.53 ± 0.33 L vs 0.40 ± 0.15 L) and EVLW (skew 3.2 ± 0.5 vs 3.7 ± 0.7; kurtosis 19.4 ± 6.6 vs 25.9 ± 9.4; FWHM 73 ± 13 HU vs 59 ± 9 HU). Spirometric measures were decreased in HF (percentage of predicted: forced vital capacity 86 ± 17% vs 104 ± 9%; forced expiratory volume in 1 second 83 ± 20% vs 105 ± 11%; maximal mid-expiratory flow 82 ± 42% vs 115 ± 43%). V_p was associated with decreased expiratory flows, and EVLW was associated with decreased lung volumes.

CONCLUSIONS

Congestion in stable patients with HF includes expanded V_p and V_h and increased EVLW associated with reductions in lung volumes and expiratory flows.

Sex differences in leptin modulate ventilation in heart failure

BACKGROUND

Leptin modulates ventilation and circulating levels are higher in normal women than men.

OBJECTIVES

The aim of this study was to compare exercise ventilation and gas exchange in men and women with heart failure (HF) and their relation to circulating leptin concentration.

METHODS

Consecutive HF patients were studied by cardiopulmonary exercise testing and assay of circulating leptin concentration.

RESULTS

Fifty-seven men and 20 women were similar with respect to age, BMI, NYHA class, left ventricular ejection fraction, and peak oxygen consumption (all p > 0.05). Leptin concentration was lower (10.3 ± 10 vs. 25.3 ± 16 ng/mL; p < 0.01) and peak exercise ventilatory efficiency (V_E/VCO₂) was higher (43 ± 10 vs. 36 ± 5; p < 0.01) in men. Leptin concentration was associated with peak exercise V_E/VCO₂ (b = -0.35; F = 5.6; p = 0.02).

CONCLUSION

Men have significantly lower circulating leptin concentration and increased ventilatory drive during exercise than women with comparable HF. In men with HF, lower leptin concentration may account for an increased ventilatory drive.

Pathogenesis of central and complex sleep apnoea

Central sleep apnoea (CSA) - the temporary absence or diminution of ventilatory effort during sleep - is seen in a variety of forms including periodic breathing in infancy and healthy adults at altitude and Cheyne-Stokes respiration in heart failure. In most circumstances, the cyclic absence of effort is paradoxically a consequence of hypersensitive ventilatory chemoreflex responses to oppose changes in airflow, that is elevated loop gain, leading to overshoot/undershoot ventilatory oscillations. Considerable evidence illustrates overlap between CSA and obstructive sleep apnoea (OSA), including elevated loop gain in patients with OSA and the presence of pharyngeal narrowing during central apnoeas. Indeed, treatment of OSA, whether via continuous positive airway pressure (CPAP), tracheostomy or oral appliances, can reveal CSA, an occurrence referred to as complex sleep apnoea. Factors influencing loop gain include increased chemosensitivity (increased controller gain), reduced damping of blood gas levels (increased plant gain) and increased lung to chemoreceptor circulatory delay. Sleep-wake transitions and pharyngeal dilator muscle responses effectively raise the controller gain and therefore also contribute to total loop gain and overall instability. In some circumstances, for example apnoea of infancy and central congenital hypoventilation syndrome, central apnoeas are the consequence of ventilatory depression and defective ventilatory responses, that is low loop gain. The efficacy of available treatments for CSA can be explained in terms of their effects on loop gain, for example CPAP improves lung volume (plant gain), stimulants reduce the alveolar-inspired PCO₂ difference and supplemental oxygen lowers chemosensitivity. Understanding the magnitude of loop gain and the mechanisms contributing to instability may facilitate personalized interventions for CSA.

Congestive Heart Failure and Central Sleep Apnea

Congestive heart failure (CHF) is among the most common causes of admission to hospitals in the United States, especially in those over age 65. Few data exist regarding the prevalence CHF of Cheyne-Stokes respiration (CSR) owing to congestive heart failure in the intensive care unit (ICU). Nevertheless, CSR is expected to be highly prevalent among those with CHF. Treatment should focus on the underlying mechanisms by which CHF increases loop gain and promotes unstable breathing. Few data are available to determine prevalence of CSR in the ICU, or how CSR might affect clinical management and weaning from mechanical ventilation.

Physiological Techniques and Pulmonary Hypertension - Left Heart Disease

Group 2 Pulmonary hypertension (PH) is associated with left heart disease (LHD;Group 2 PH) and is the most common form of PH. Group 2 PH represents an important subgroup of patients with LHD where the development of PH leads to a significant increase in morbidity and mortality. Early diagnosis may provide an opportunity to intervene and significantly delay progression. In addition to clinical suspicion, several approaches including hemodynamic assessment, exercise testing, and imaging techniques play an important role in better disease characterization and management. Here, we review the role of physiologic based hemodynamic and exercise assessments of Group 2 PH patients.

Congestive heart failure and central sleep apnea

Congestive heart failure (CHF) is among the most common causes of admission to hospitals in the United States, especially in those over age 65. Few data exist regarding the prevalence CHF of Cheyne-Stokes respiration (CSR) owing to congestive heart failure in the intensive care unit (ICU). Nevertheless, CSR is expected to be highly prevalent among those with CHF. Treatment should focus on the underlying mechanisms by which CHF increases loop gain and promotes unstable breathing. Few data are available to determine prevalence of CSR in the ICU, or how CSR might affect clinical management and weaning from mechanical ventilation.

Relief and Recurrence of Congestion During and After Hospitalization for Acute Heart Failure: Insights From Diuretic Optimization Strategy Evaluation in Acute Decompensated Heart Failure (DOSE-AHF) and Cardiorenal Rescue Study in Acute Decompensated Heart Failure (CARESS-HF)

BACKGROUND

Congestion is the most frequent cause for hospitalization in acute decompensated heart failure. Although decongestion is a major goal of acute therapy, it is unclear how the clinical components of congestion (eg, peripheral edema, orthopnea) contribute to outcomes after discharge or how well decongestion is maintained.

METHODS AND RESULTS

A post hoc analysis was performed of 496 patients enrolled in the Diuretic Optimization Strategy Evaluation in Acute Decompensated Heart Failure (DOSE-AHF) and Cardiorenal Rescue Study in Acute Decompensated Heart Failure (CARRESS-HF) trials during hospitalization with acute decompensated heart failure and clinical congestion. A simple orthodema congestion score was generated based on symptoms of orthopnea (≥2 pillows=2 points, <2 pillows=0 points) and peripheral edema (trace=0 points, moderate=1 point, severe=2 points) at baseline, discharge, and 60-day follow-up. Orthodema scores were classified as absent (score of 0), low-grade (score of 1-2), and high-grade (score of 3-4), and the association with death, rehospitalization, or unscheduled medical visits through 60 days was assessed. At baseline, 65% of patients had high-grade orthodema and 35% had low-grade orthodema. At discharge, 52% patients were free from orthodema at discharge (score=0) and these patients had lower 60-day rates of death, rehospitalization, or unscheduled visits (50%) compared with those with low-grade or high-grade orthodema (52% and 68%, respectively; P=0.038). Of the patients without orthodema at discharge, 27% relapsed to low-grade orthodema and 38% to high-grade orthodema at 60-day follow-up.

CONCLUSIONS

Increased severity of congestion by a simple orthodema assessment is associated with increased morbidity and mortality. Despite intent to relieve congestion, current therapy often fails to relieve orthodema during hospitalization or to prevent recurrence after discharge.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00608491, NCT00577135.

Modulation of ventilatory reflex control by cardiac resynchronization therapy

BACKGROUND

Heart failure (HF) is characterized by heightened sensitivities of the CO2 chemoreflex and the ergoreflex which promote increased ventilatory drive manifested as increased minute ventilation per volume of expired CO2 (VE/VCO2). The aims of this study were to evaluate the effects of cardiac resynchronization therapy (CRT) on carbon dioxide (CO2) chemosensitivity and the arterial CO2 setpoint.

METHODS AND RESULTS

Consecutive HF patients (n = 35) who underwent clinically indicated CRT were investigated by means of cardiopulmonary exercise testing and CO2 chemosensitivity evaluation with the use of a rebreathe method before and 4-6 months after CRT. Pre- and post-CRT measures were compared with the use of either paired t test or Wilcoxon test. Decreased peak VE/VCO2 (44 ± 10 vs 40 ± 8; P < .01), CO2 chemosensitivity (2.2 ± 1.1 vs 1.7 ± 0.8 L min(-1) mm Hg(-1); P = .04), and increased peak end-tidal CO2 (29 ± 5 vs 31 ± 5 mm Hg; P < .01) were also observed after CRT. Multivariate analysis adjusted for age and sex showed the decrease of peak VE/VCO2 from before to after CRT to be most strongly associated with the increase of peak end-tidal CO2 (β = -0.84; F = 21.5; P < .0001).

CONCLUSIONS

Decrease of VE/VCO2 after CRT is associated with decreased CO2 chemosensitivity and increase of the arterial CO2 setpoint, which is consistent with decreased activation of both the CO2 chemoreflex and the ergoreflex.

Altered breathing syndrome in heart failure: newer insights and treatment options

In patients with heart failure (HF), altered breathing patterns, including periodic breathing, Cheyne-Stokes breathing, and oscillatory ventilation, are seen in several situations. Since all forms of altered breathing cause similar detrimental effects on clinical outcomes, they may be considered collectively as an "altered breathing syndrome." Altered breathing syndrome should be recognized as a comorbid condition of HF and as a potential therapeutic target. In this review, we discuss mechanisms and therapeutic options of altered breathing while sleeping, while awake at rest, and during exercise.

Influence of lung volume, fluid and capillary recruitment during positional changes and exercise on thoracic impedance in heart failure

It is unclear how dynamic changes in pulmonary-capillary blood volume (Vc), alveolar lung volume (derived from end-inspiratory lung volume, EILV) and interstitial fluid (ratio of alveolar capillary membrane conductance and pulmonary capillary blood volume, Dm/Vc) influence lung impedance (Z(T)). The purpose of this study was to investigate if positional change and exercise result in increased EILV, Vc and/or lung interstitial fluid, and if Z(T) tracks these variables.

METHODS

12 heart failure (HF) patients underwent measurements (Z(T), EILV, Vc/Dm) at rest in the upright and supine positions, during exercise and into recovery. Inspiratory capacity was obtained to provide consistent measures of EILV while assessing Z(T).

RESULTS

Z(T) increased with lung volume during slow vital capacity maneuvers (p<0.05). Positional change (upright→supine) resulted in an increased Z(T) (p<0.01), while Vc increased and EILV and Dm/Vc decreased (p<0.05). Moreover, during exercise Vc and EILV increased and Dm/Vc decreased (p<0.05), whereas, Z(T) did not change significantly (p>0.05).

CONCLUSION

Impedance appears sensitive to changes in lung volume and body position which appear to generally overwhelm small acute changes in lung fluid when assed dynamically at rest or during exercise.

Pathophysiology of human ventilatory control

We review the substantial recent progress made in understanding the underlying mechanisms controlling breathing and the applicability of these findings to selected human diseases. Emphasis is placed on the sites of central respiratory rhythm and pattern generation as well as newly described functions of the carotid chemoreceptors, the integrative nature of the central chemoreceptors, and the interaction between peripheral and central chemoreception. Recent findings that support critical contributions from cortical central command and muscle afferent feedback to exercise hyperpnoea are also reviewed. These basic principles, and the evidence supporting chemoreceptor and ventilatory control system plasticity during and following constant and intermittent hypoxaemia and stagnant hypoxia, are applied to: 1) the pathogenesis, consequences and treatment of obstructive sleep apnoea; and 2) exercise hyperpnoea and its control and limitations with ageing, chronic obstructive pulmonary disease and congestive heart failure.

Left atrial size, chemosensitivity, and central sleep apnea in heart failure

BACKGROUND

Central sleep apnea (CSA) is common among patients with heart failure (HF) and is promoted by elevated CO2 chemosensitivity. Left atrial size is a marker of the hemodynamic severity of HF. The aim of this study was to determine if left atrial size predicts chemosensitivity to CO2 and CSA in patients with HF.

METHODS

Patients with HF with left ventricular ejection fraction ≤ 35% underwent polysomnography for detection of CSA, echocardiography, and measurement of CO2 chemosensitivity. CSA was defined as an apnea-hypopnea index (AHI) ≥ 15/h with ≥ 50% central apneic events. The relation of clinical and echocardiographic parameters to chemosensitivity and CSA were evaluated by linear regression, estimation of ORs, and receiver operator characteristics.

RESULTS

Of 46 subjects without OSA who had complete data for analysis, 25 had CSA. The only parameter that significantly correlated with chemosensitivity was left atrial volume index (LAVI) (r = 0.40, P < .01). LAVI was greater in those with CSA than those without CSA (59.2 mL/m2 vs 36.4 mL/m2, P < .001) and significantly correlated with log-transformed AHI (r = 0.46, P = .001). LAVI was the best predictor of CSA (area under the curve = 0.83). A LAVI ≤ 33 mL/m2 was associated with 22% risk for CSA, while LAVI ≥ 53 mL/m2 was associated with 92% risk for CSA.

CONCLUSIONS

Increased LAVI is associated with heightened CO2 chemosensitivity and greater frequency of CSA. LAVI may be useful to guide referral for polysomnography for detection of CSA in patients with HF.

Effects of atrioventricular and interventricular delays on gas exchange during exercise in patients with heart failure

BACKGROUND

Cardiac resynchronization therapy (CRT) has been an important treatment for heart failure. However, it is controversial as to whether an individualized approach to altering AV and VV timing intervals would improve outcomes. Changes in respiratory patterns and gas exchange are dynamic and may be influenced by timing delays. Light exercise enhances the heart and lung interactions. Thus, in this study we investigated changes in non-invasive gas exchange by altering AV and VV timing intervals during light exercise.

METHODS

Patients (n = 20, age 66 ± 9 years) performed two walking tests post-implantation. The protocol evaluated AV delays (100, 120, 140, 160 and 180 milliseconds), followed by VV delays (0, -20 and -40 milliseconds) while gas exchange was assessed.

RESULTS

There was no consistent group pattern of change in gas exchange variables across AV and VV delays (p > 0.05). However, there were modest changes in these variables on an individual basis with variations in VE/VCO2 averaging 10%; O2 pulse 11% and PETCO2 5% across AV delays, and 4%, 8% and 2%, respectively, across VV delays. Delays that resulted in the most improved gas exchange differed from nominal in 17 of 20 subjects.

CONCLUSION

Gas exchange measures can be improved by optimization of AV and VV delays and thus could be used to individualize the approach to CRT optimization.

Quantifying oscillatory ventilation during exercise in patients with heart failure

BACKGROUND

This study examined the validity of a novel software application to quantify measures of periodic breathing rest (PB) and oscillatory ventilation during exercise (EOV) in heart failure patients (HF).

METHODS

Eleven male HF patients (age=53±8yrs, ejection fraction=17±4, New York Heart Association Class=III(7)/IV(4)) were recruited. Ventilation and gas exchange were collected breath-by-breath. Amplitude and period of oscillations in ventilation (V˙E), tidal volume (VT), end-tidal carbon dioxide [Formula: see text] , and oxygen consumption [Formula: see text] were measured manually (MAN) and using novel software which included a peak detection algorithm (PK), sine wave fitting algorithm (SINE), and Fourier analysis (FOUR).

RESULTS

During PB, there were no differences between MAN and PK for amplitude of V˙E, VT, [Formula: see text] , or [Formula: see text] . Similarly, there were no differences between MAN and SINE for amplitude of V˙E or VT although [Formula: see text] and [Formula: see text] were lower with SINE (p<0.05). In contrast, the PK demonstrated significantly shorter periods for V˙E, VT, [Formula: see text] , and [Formula: see text] compared to MAN (p<0.05) whereas there were no differences in periods of oscillations between MAN and SINE or FOUR for all variables. During EOV, there were no differences between MAN and PK for amplitude of V˙E, VT, [Formula: see text] , and [Formula: see text] . SINE demonstrated significantly lower amplitudes for VT, [Formula: see text] , and [Formula: see text] (p<0.05) although V˙E was not different. PK demonstrated shorter periods for all variables (p<0.05) whereas there were no differences between MAN and SINE or FOUR for all variables.

CONCLUSION

These data suggest PK consistently captures amplitudes while underestimating period. In contrast, SINE and FOUR consistently capture period although SINE underestimates amplitude. Thus, an optimal algorithm for the quantification of PB and/or EOV in patients with HF might combine multiple analysis methods.

Use of noninvasive gas exchange to track pulmonary vascular responses to exercise in heart failure

We determined whether a non-invasive gas exchange based estimate of pulmonary vascular (PV) capacitance [PV_CAP = stroke volume (SV) × pulmonary arterial pressure (Ppa)] (GX_CAP) tracked the PV response to exercise in heart-failure (HF) patients. Pulmonary wedge pressure (Ppw), Ppa, PV resistance (PVR), and gas exchange were measured simultaneously during cycle exercise in 42 HF patients undergoing right-heart catheterization. During exercise, P_ETCO₂ and V_E/VCO₂ were related to each other (r = −0.93, P < 0.01) and similarly related to mean Ppa (mPpa) (r = −0.39 and 0.36; P < 0.05); P_ETCO₂ was subsequently used as a metric of mPpa. Oxygen pulse (O₂ pulse) tracked the SV response to exercise (r = 0.91, P < 0.01). Thus, GX_CAP was calculated as O₂ pulse × P_ETCO₂. During exercise, invasively determined PV_CAP and non-invasive GX_CAP were related (r = 0.86, P < 0.01), and GX_CAP correlated with mPpa and PVR (r = −0.46 and −0.54; P < 0.01). In conclusion, noninvasive gas exchange measures may represent a simple way to track the PV response to exercise in HF.

A possible role for systemic hypoxia in the reactive component of pulmonary hypertension in heart failure

BACKGROUND

The mechanisms underlying the reactive component of pulmonary hypertension (PH) in heart failure (HF) are unclear. We examined whether resting systemic oxygen levels are related to pulmonary hemodynamics in HF.

METHODS AND RESULTS

Thirty-nine HF patients underwent right heart catheterization. Subsequently, patients were classified as having: 1) no PH (n = 12); 2) passive PH (n = 10); or 3) reactive PH (n = 17). Blood was drawn from the radial and pulmonary arteries for the determination of PaO(2), SaO(2), PvO(2), SvO(2), and vasoactive neurohormones. PaO(2) and PvO(2) were lower in reactive PH versus no PH and passive PH patients (65.3 ± 8.6 vs 78.3 ± 11.4 mm Hg and 74.5 ± 14.0 mm Hg; 29.2 ± 4.1 vs 36.2 ± 2.8 mm Hg and 33.4 ± 2.3 mm Hg; P < .05). SaO(2) and SvO(2) were lower in reactive PH versus no PH patients (93 ± 3% vs 96 ± 3%; 51 ± 11% vs 68 ± 4%; P < .05), but not different versus passive PH patients. The transpulmonary pressure gradient (TPG) was inversely related to PaO(2), PvO(2), SaO(2), and SvO(2) in the reactive PH patients only (r ≤ -0.557; P < .05). Similarly, plasma endothelin-1 correlated with PaO(2), PvO(2), SvO(2) (r ≤ -0.495), and TPG (r = 0.662; P < .05) in reactive PH patients only.

CONCLUSIONS

Systemic hypoxia may play a role in the reactive component of PH in HF, potentially via a hypoxia-induced increase in endothelial release of the vasoconstrictor endothelin-1.

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.

Influence of cardiomegaly on disordered breathing during exercise in chronic heart failure

AIMS

Heart failure (HF) patients breathe with a rapid shallow pattern during exercise. This study examined the relationship between cardiac size and tachypnoeic breathing in HF patients during exercise.

METHODS AND RESULTS

Thirty-seven HF patients [age = 55 ± 13 years, ejection fraction (EF) = 27 ± 10%, New York Heart Association (NYHA) class = 2.3 ± 1.2] and 42 controls (CTL) (age = 56 ± 14 years, EF = 63 ± 8%) were recruited. Participants underwent maximal exercise testing, pulmonary function testing, and chest radiography for calculation of total thoracic cavity volume (TTCV), diaphragm, heart, and lung volumes. Heart failure patients were divided into two groups: Group A = cardiac volume < median (n = 18) and Group B = cardiac volume ≥ median of the HF patients (n = 19). There was no difference between groups for TTCV (CTL = 8203 ± 1489 vs. Group A = 8694 ± 1249 vs. Group B = 8195 ± 1823 cm(3)). Cardiac volume was different between groups for both absolute (CTL = 630 ± 181 vs. Group A = 894 ± 186 vs. Group B = 1401 ± 382 cm(3), P< 0.001 for all comparisons) and %TTCV (CTL = 8 ± 2 vs. Group A = 10 ± 1 vs. Group A = 18 ± 5%, P< 0.001 for all comparisons). Similarly, total lung volume as a %TTCV was significantly different among the groups (CTL = 70 ± 4 vs. Group A = 65 ± 5 vs. Group A = 58 ± 7%, P< 0.01 for all comparisons). In HF patients, there was a trend (P = 0.10) towards an independent association between cardiac size and tidal volume (V(T)) at 75% of VO(2) peak whereas this relationship was statistically significant at VO(2) peak (P = 0.02) as patients with larger cardiac size had reduced V(T).

CONCLUSION

This study demonstrates the close relationship between cardiac size and breathing pattern during exercise in HF patients. These results suggest cardiac size may pose a significant constraint on the lungs during exercise and may contribute to tachypnoeic breathing.

Pulmonary hypertension with left-sided heart disease

Pulmonary hypertension (PH) with left-sided heart disease is defined, according to the latest Venice classification, as a Group 2 PH, which includes left-sided ventricular or atrial disease, and left-sided valvular diseases. These conditions are all associated with increased left ventricular filling pressure. Although PH with left-sided heart disease is a common entity, and long-term follow-up trials have provided firm recognition that development of left-sided PH carries a poor outcome, available data on incidence, pathophysiology, and therapy are sparse. Mitral stenosis was reported as the most frequent cause of PH several decades ago, but PH with left-sided heart disease is now usually caused by systemic hypertension and ischemic heart disease. In patients with these conditions, PH develops as a consequence of impaired left ventricular relaxation and distensibility. Chronic sustained elevation of cardiogenic blood pressure in pulmonary capillaries leads to a cascade of untoward retrograde anatomical and functional effects that represent specific targets for therapeutic intervention. The pathophysiological and clinical importance of the hemodynamic consequences of left-sided heart disease, starting with lung capillary injury and leading to right ventricular overload and failure, are discussed in this Review, focusing on PH as an evolving contributor to heart failure that may be amenable to novel interventions.

Influence of locomotor muscle metaboreceptor stimulation on the ventilatory response to exercise in heart failure

BACKGROUND

Whether locomotor muscle afferent neural activity contributes to exercise hyperpnea and symptoms of dyspnea in heart failure (HF) is controversial. We examined the influence of metaboreceptor stimulation on ventilation with and without maintaining end-exercise end-tidal CO(2) levels.

METHODS AND RESULTS

Eleven patients with HF aged 51+/-5 years (ejection fraction, 32+/-3%; New York Heart Association class, 1.6+/-0.2) and 11 age- and gender-matched healthy control participants aged 43+/-3 years were studied. Participants underwent 3 steady-state cycling sessions at 60% of peak oxygen consumption for 4 minutes. The first exercise session was a baseline control trial. Bilateral thigh tourniquets were inflated to suprasystolic pressure at end exercise for 2 minutes during 2 of the trials (regional circulatory occlusion) with the addition of inspired CO(2) to maintain end-exercise partial pressure of end-tidal CO(2) during 1 trial (regional circulatory occlusion+CO(2)). Minute ventilation was measured continuously throughout each trial. At 2 minutes postexercise during the baseline control trial in patients with HF, minute ventilation was 54% of end exercise, whereas the control group averaged 41% (P=0.11). During regional circulatory occlusion in patients with HF, minute ventilation was 60% of end exercise; however, the control group averaged 35% (P<0.001). During regional circulatory occlusion+CO(2), the minute ventilation of patients with HF averaged 67% of end exercise, whereas the control group averaged 44% (P<0.001).

CONCLUSIONS

These data suggest that increased afferent neural activity from the large locomotor muscles associated with metabolites generated during exercise contribute to the augmented ventilatory response to exercise in patients with HF.

Nitroprusside in decompensated heart failure: what should a clinician really know?

Sodium nitroprusside is an older intravenous vasodilator appropriate for acute hospital treatment of patients with congestive heart failure. It is a balanced arterial and venous vasodilator with a very short half-life, facilitating rapid titration. In general, it improves hemodynamic and clinical status by reducing systemic vascular resistance, left ventricular filling pressure, and increasing cardiac output. This review summarizes recently published literature and recent data regarding the use of this intravenous vasodilator in decompensated heart failure patients.

Exercise oscillatory breathing in diastolic heart failure: prevalence and prognostic insights

AIMS

Exercise intolerance occurs in both systolic and diastolic heart failure (HF). Exercise oscillatory breathing (EOB) is a powerful predictor of survival in patients with systolic HF. In diastolic HF, EOB prevalence and prognostic impact are unknown.

METHODS AND RESULTS

A total of 556 HF patients (405 with systolic HF and 151 with diastolic HF) underwent cardiopulmonary exercise testing (CPET). Diastolic HF was defined as signs and symptoms of HF, a left ventricular ejection fraction > or =50%, and a Doppler early (E) mitral to early mitral annulus ratio (E') > or =8. CPET responses, EOB prevalence and its ability to predict cardiac-related events were examined. EOB prevalence in systolic and diastolic HF was similar (35 vs. 31%). Compared with the patients without EOB, patients with EOB and either systolic or diastolic HF had a higher New York Heart Association class, lower peak VO(2) and higher E/E' ratio (all P < 0.01). Univariate Cox regression analysis demonstrated that peak VO(2), VE/VCO(2) slope and EOB all were significant predictors of cardiac events in both systolic and diastolic HF. Multivariable analysis revealed that EOB was retained as a prognostic marker in systolic HF and was the strongest predictor of cardiac events in diastolic HF.

CONCLUSION

EOB occurrence is similar in diastolic and systolic HF and provides relevant clues for the identification of diastolic HF patients at increased risk of adverse events.

Recurrent acute pulmonary oedema after aortic and mitral valve surgery due to trachea malacia and obstructive sleep apnoea syndrome

In this report we describe a patient with recurrent episodes of acute pulmonary oedema after aortic and mitral valve surgery. The first episode of pulmonary oedema was caused by mitral valve dysfunction. The second episode of pulmonary oedema was not clearly associated with a mitral valve problem, but reoperation was performed in the absence of another explanation. After the third episode of acute pulmonary oedema occurred, the diagnosis of obstructive sleep apnoea syndrome (OSAS) was considered and confirmed. After starting treatment with continuous positive airway pressure (CPAP) during his sleep the patient had no further episodes of acute respiratory failure. Our case demonstrates that acute pulmonary oedema after cardiothoracic surgery can be caused or at least be precipitated by OSAS and should be suspected in patients with unexplained episodes of (recurrent) pulmonary oedema. (Neth Heart J 2008;16:310-2.).