Periodic breathing during incremental exercise predicts mortality in patients with chronic heart failure evaluated for cardiac transplantation

How to interpret a cardiorespiratory fitness assessment - Key measures that provide the best picture of health, disease status and prognosis

Graded exercise testing is a widely accepted tool for revealing cardiac ischemia and/or arrhythmias in clinical settings. Cardiopulmonary exercise testing (CPET) measures expired gases during a graded exercise test making it a versatile tool that helps reveal underlying physiologic abnormalities that are in many cases only present with exertion. It also characterizes one's health status and clinical trajectory, informs the therapeutic plan, evaluates the efficacy of therapy, and provides submaximal and maximal information that can be used to tailor an exercise intervention. Practitioners can also modify the mode and protocol to allow individuals of all ages, fitness levels, and most disease states to perform a CPET. When used to its full potential, CPET can be a key tool used to optimize care in primary and secondary prevention settings.

Exercise oscillatory ventilation: the past, present, and future

Exercise oscillatory ventilation (EOV) is a fascinating event that can be appreciated in the cardiopulmonary exercise test and is characterized by a cyclic fluctuation of minute ventilation, tidal volume, oxygen uptake, carbon dioxide production, and end-tidal pressure for oxygen and carbon dioxide. Its mechanisms stem from a dysregulation of the normal control feedback of ventilation involving one or more of its components, namely, chemoreflex delay, chemoreflex gain, plant delay, and plant gain. In this review, we intend to breakdown therapeutic targets according to pathophysiology and revise the prognostic value of exercise oscillatory ventilation in the setting of heart failure and other diagnoses.

Software development to standardize the clinical diagnosis of exercise oscillatory ventilation in heart failure

BACKGROUND

Exercise oscillatory ventilation (EOV) is characterized by periodic oscillations of minute ventilation during cardiopulmonary exercise testing (CPET). Despite its prognostic value in chronic heart failure (HF), its diagnosis is complex due to technical limitations. An easier and more accurate way of EOV identification can contribute to a better approach and clinical diagnosis. This study aims to describe a software development to standardize the EOV diagnosis from CPET's raw data in heart failure patients and test its reliability (intra- and inter-rater).

METHODS

The software was developed in the "drag-and-drop" G-language using LabVIEW®. Five EOV definitions (Ben-Dov, Corrà, Kremser, Leite, and Sun definitions), two alternative approaches, one smoothing technique, and some basic statistics were incorporated into the interface to visualize four charts of the ventilatory response. EOV identification was based on a set of criteria verified from the interaction between amplitude, cycle length, and oscillation time. Two raters analyzed the datasets. In addition, repeated measurements were verified after six months using about 25% of the initial data. Cohen's kappa coefficient (κ) was used to investigate the reliability.

RESULTS

Overall, 391 tests were analyzed in duplicate (inter-rater reliability) and 100 tests were randomized for new analysis (intra-rater reliability). High inter-rater (κ > 0.80) and intra-rater (κ > 0.80) reliability of the five EOV diagnoses were observed.

CONCLUSION

The present study proposes novel semi-automated software to detect EOV in HF, with high inter and intra-rater agreements. The software project and its tutorial are freely available for download.

Exercise oscillatory ventilation in patients with coexisting chronic obstructive pulmonary disease and heart failure: Clinical implications

BACKGROUND

Exercise oscillatory ventilation (EOV) is considered an important variable for predicting poor prognosis in patients with heart failure (HF) with reduced left ventricular ejection fraction (HFrEF). However, there are no studies evaluating EOV presence in the coexistence chronic obstructive pulmonary disease (COPD) and HFrEF.

AIMS

I) To compare the clinical characteristics of participants with coexisting HFrEF-COPD with and without EOV during cardiopulmonary exercise testing (CPET); and II) to identify the impact of EOV on mortality during follow-up for 35 months.

METHODS

50 stable HFrEF-COPD (EF<50%) participants underwent CPET and were followed for 35 months. The parametric Student's t-test, chi-square tests, linear regression model and Kaplan-Meier analysis were applied.

RESULTS

We identified 13 (26%) participants with EOV and 37 (74%) without EOV (N-EOV) during exercise. The EOV group had worse cardiac function (LVEF: 30 ± 6% vs. N-EOV 40 ± 9%, p = 0.007), worse pulmonary function (FEV1: 1.04 ± 0.7 L vs. N-EOV 1.88 ± 0.7 L, p = 0.007), a higher mortality rate [7 (54%) vs. N-EOV 8 (27%), p = 0.02], higher minute ventilation/carbon dioxide production (V̇˙E/ V̇˙ CO2) slope (42 ± 7 vs. N-EOV 36 ± 8, p = 0.04), reduced peak ventilation (L/min) (26.2 ± 16.7 vs. N-EOV 40.3 ± 16.4, p = 0.01) and peak oxygen uptake (mlO2 kg-1 min-1) (11.0 ± 4.0 vs. N-EOV 13.5 ± 3.4 ml●kg-1●min-1, p = 0.04) when compared with N-EOV group. We found that EOV group had a higher risk of mortality during follow-up (long-rank p = 0.001) than patients with N-EOV group.

CONCLUSION

The presence of EOV is associated with greater severity of coexisting HFrEF and COPD and a reduced prognosis. Assessment of EOV in participants with coexisting HFrEF-COPD, as a biomarker for both clinical status and prognosis may therefore be warranted.

Hypertrophic Cardiomyopathy: A Cardiovascular Challenge Becoming a Contemporary Treatable Disease

Hypertrophic cardiomyopathy is one of the most common genetic inherited diseases of myocardium, which is caused by mutation in genes encoding proteins for the cardiac sarcomere. It is the most frequent cause of sudden death in young people and trained athletes. All diagnostic methods, including heart catheterization, transthoracic and transesophageal echocardiography, magnetic resonance imaging, genetic counseling and tissue biopsy are required for risk and therapy stratification and should be individualized depending on phenotype and genotype. Current therapy has not been tested adequately. Beta-blockers and verapamil can cause hypotension which can make hypertrophic cardiomyopathy worse. Disopyramide has been inadequately studied, and mavacamten was only studied in small trials. More definitive trials are currently ongoing. Novel invasive and noninvasive diagnostics, medical therapies, interventional and surgical approaches tend to influence the natural history of the disease, favoring a better future for this patient population.

Influence of exertional oscillatory breathing and its temporal behavior in patients with heart failure and reduced ejection fraction

BACKGROUND

Exertional oscillatory breathing (EOV) represents an emerging prognostic marker in heart failure (HF) patients, however little is known about EOV meaning with respect to its disappearance/persistence during cardiopulmonary exercise test (CPET). The present single-center study evaluated EOV clinical and prognostic impact in a large cohort of reduced ejection fraction HF patients (HFrEF) and, contextually, if a specific EOV temporal behavior might be an addictive risk predictor.

METHODS AND RESULTS

Data from 1.866 HFrEF patients on optimized medical therapy were analysed. The primary cardiovascular (CV) study end-point was cardiovascular death, heart transplantation or LV assistance device (LVAD) implantation at 5-years. For completeness a secondary end-point of total mortality at 5- years was also explored. EOV presence was identified in 251 patients (13%): 142 characterized by EOV early cessation (Group A) and 109 by EOV persistence during the whole CPET (Group B). The entire EOV Group showed worse clinical and functional status than NoEOV Group (n = 1.615) and, within the EOV Group, Group B was characterized by a more severe HF. At CV survival analysis, EOV patients showed a poorer outcome than the NoEOV Group (events 27.1% versus 13.1%, p < 0.001) both unpolished and after matching for main confounders. Instead, no significant differences were found between EOV Group A and B with respect to CV outcome. Conversely the analysis for total mortality failed to be significant.

CONCLUSIONS

Our analysis, albeit retrospective, supports the inclusion of EOV into a CPET-centered clinical and prognostic evaluation of the HFrEF patients. EOV characterizes per se a more advanced HFrEF stage with an unfavorable CV outcome. However, the EOV persistence, albeit suggestive of a more severe HF, does not emerge as a further prognostic marker.

Beyond exercise oscillatory ventilations: the prognostic impact of loop gain in heart failure

Exercise oscillatory ventilation (EOV) is a strong prognostic marker in patients with heart failure (HF) and left ventricular (LV) dysfunction. This phenomenon can be explained through a single quantitative measurement of ventilatory instability, the loop gain. Therefore, we aimed to evaluate whether loop gain could be a better tool than subjective EOV evaluation to identify HF patients with a higher risk of major cardiovascular complications. This was a single-center retrospective study that included patients with left ventricular ejection fraction (LVEF) ≤ 50% consecutively referred for cardiopulmonary exercise testing (CPET) from 2016-2020. Loop gain was measured through computational evaluation of the minute ventilation graph. Of the 250 patients included, the 66 that presented EOV also had higher values of loop gain, when compared to patients without EOV. Those with both EOV and higher loop gain had more severe HF, with higher NT-proBNP and VE/VCO2 slope as well as lower peak VO2 and LVEF. On multivariable analysis, loop gain was strongly correlated with the composite endpoint of cardiovascular death, urgent heart transplantation, urgent left ventricular assist device implantation or HF hospitalization, even after correcting for peak VO2, LVEF, VE/VCO2 slope and NT-proBNP. Presence of EOV was not prognostically significant in this analysis. Loop gain is an objective parameter that quantifies ventilatory instability and showed to have a strong prognostic value in a cohort of patients with HF and LVEF ≤ 50%, outperforming the classification of EOV.

Excess ventilation and exertional dyspnoea in heart failure and pulmonary hypertension

Increased ventilation relative to metabolic demands, indicating alveolar hyperventilation and/or increased physiological dead space (excess ventilation), is a key cause of exertional dyspnoea. Excess ventilation has assumed a prominent role in the functional assessment of patients with heart failure (HF) with reduced (HFrEF) or preserved (HFpEF) ejection fraction, pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). We herein provide the key pieces of information to the caring physician to 1) gain unique insights into the seeds of patients' shortness of breath and 2) develop a rationale for therapeutically lessening excess ventilation to mitigate this distressing symptom. Reduced bulk oxygen transfer induced by cardiac output limitation and/or right ventricle-pulmonary arterial uncoupling increase neurochemical afferent stimulation and (largely chemo-) receptor sensitivity, leading to alveolar hyperventilation in HFrEF, PAH and small-vessel, distal CTEPH. As such, interventions geared to improve central haemodynamics and/or reduce chemosensitivity have been particularly effective in lessening their excess ventilation. In contrast, 1) high filling pressures in HFpEF and 2) impaired lung perfusion leading to ventilation/perfusion mismatch in proximal CTEPH conspire to increase physiological dead space. Accordingly, 1) decreasing pulmonary capillary pressures and 2) mechanically unclogging larger pulmonary vessels (pulmonary endarterectomy and balloon pulmonary angioplasty) have been associated with larger decrements in excess ventilation. Exercise training has a strong beneficial effect across diseases. Addressing some major unanswered questions on the link of excess ventilation with exertional dyspnoea under the modulating influence of pharmacological and nonpharmacological interventions might prove instrumental to alleviate the devastating consequences of these prevalent diseases.

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.

Sensitivity and specificity of different exercise oscillatory ventilation definitions to predict 2-year major adverse cardiovascular outcomes in chronic heart failure patients

BACKGROUND

Exercise oscillatory ventilation (EOV) shows a four-fold greater risk of adverse events. This study aims to analyze the sensitivity and specificity of three EOV diagnostic definitions to predict adverse outcomes at a 2-year follow-up and to compare its EOV prevalence and relations with the patient's profile.

METHODS

Cardiopulmonary exercise tests from 233 heart failure patients were analyzed. Two blinded reviewers used a semiautomated software to identify EOV cases pattern according to the definitions of Ben-Dov, Corrà, and Leite. Data were grouped in EOV-positive or EOV-negative according to each definition. Baseline characteristics, EOV prevalence, relative risk, sensitivity, and specificity to predict 2-years of major adverse cardiovascular outcomes were analyzed.

RESULTS

The Corrà definition led to the best prediction of 2-year major cardiovascular adverse outcomes (HR 2.46 [1.16 to 5.25]; p = 0.019, AUC = 0.618; p = 0.007). EOV prevalence was 17.2%, 17.2%, and 9.4% applying Ben-Dov, Corrà, and Leite definition, respectively. The main clinical differences between EOV-positive and EOV-negative patients were: MECKI score and VE/VCO₂ slope (all definitions), and BNP levels (Ben-Dov and Leite). BNP levels were correlated with amplitude (rho = 0.255; p = 0.033) and cycle length (rho = 0.388; p = 0.002).

CONCLUSION

Corrà definition was the only one that exhibited the capacity to predict major adverse cardiovascular outcomes at a 2-year follow-up. Regardless of its definition, EOV was more often prevalent in patients with a greater MECKI score and VE/VCO₂ slope values.

Exercise Oscillatory Breathing in Heart Failure with reduced ejection fraction: clinical implication

AIM

I) to evaluate the impact of exertional oscillatory ventilation (EOV) in patients with heart failure (HF) with reduced left ventricular ejection fraction (HFrEF) during cardiopulmonary exercise testing (CPET) compared with patients without EOV (N-EOV); II) to identify the influence of EOV persistence (P-EOV) and EOV disappearance (D-EOV) during CPET on the outcomes of mortality and hospitalization in HFrEF patients; and III) to identify further predictors of mortality and hospitalization in patients with P-EOV.

METHODS AND RESULTS

315 stable HFrEF patients underwent CPET and were followed for 35 months. We identified 202 patients N-EOV and 113 patients with EOV. Patients with EOV presented more symptoms (NYHA III: 35% vs. N-EOV 20%, p < 0.05), worse cardiac function (LVEF: 28 ± 6 vs. N-EOV 39 ± 1, p < 0.05), higher minute ventilation/carbon dioxide production (V̇E/V̇CO2 slope: 41 ± 11 vs. N-EOV 37 ± 8, p < 0.05) and a higher rate of deaths (26% vs. N-EOV 6%, p < 0.05) and hospitalization (29% vs. N-EOV 9%, p < 0.05). P-EOV patients had more severe HFrEF (NYHA IV: 23% vs D-EOV: 9%, p < 0.05), had worse cardiac function (LVEF: 24 ± 5 vs. D-EOV: 34 ± 3, p < 0.05) and had lower peak oxygen consumption (V̇O2) (12.0 ± 3.0 vs D-EOV: 13.3 ± 3.0 mlO2.kg-1.min-1, p < 0.05). Among P-EOV, other independent predictors of mortality were V̇E/V̇CO2 slope ≥36 and V̇O2 peak ≤12 mlO2.kg-1.min-1; a V̇E/V̇CO2 slope≥34 was a significant predictor of hospitalization. Kaplan-Meier survival analysis showed that, HFrEF patients with P-EOV had a higher risk of mortality and higher risk of hospitalization (p < 0.05) than patients with D-EOV and N-EOV.

CONCLUSION

In HFrEF patients, EOV persistence during exercise had a strong prognostic role. In P-EOV patients V̇E/V̇CO2 ≥36 and V̇O2 peak ≤12 mlO2.kg-1.min-1, had a further additive negative prognostic role.

The Impact of Oxygen Pulse and Its Curve Patterns on Male Patients with Heart Failure, Chronic Obstructive Pulmonary Disease, and Healthy Controls-Ejection Fractions, Related Factors and Outcomes

Oxygen pulse (O2P) is a function of stroke volume and cellular oxygen extraction and O2P curve pattern (O2PCP) can provide continuous measurements of O2P. However, measurements of these two components are difficult during incremental maximum exercise. As cardiac function is evaluated using ejection fraction (EF) according to the guidelines and EF can be obtained using first-pass radionuclide ventriculography, the aim of this study was to investigate associations of O2P%predicted and O2PCP with EF in patients with heart failure with reduced or mildly reduced ejection fraction (HFrEF/HFmrEF) and chronic obstructive pulmonary disease (COPD), and also in normal controls. This was a prospective observational cross-sectional study. Correlations of resting left ventricular EF, dynamic right and left ventricular EFs and outcomes with O2P% and O2PCP across the three participant groups were analyzed. A total of 237 male subjects were screened and 90 were enrolled (27 with HFrEF/HFmrEF, 30 with COPD and 33 normal controls). O2P% and the proportions of the three types of O2PCP were similar across the three groups. O2P% reflected dynamic right and left ventricular EFs in the control and HFrEF/HFmrEF groups, but did not reflect resting left ventricular EF in all participants. O2PCP did not reflect resting or dynamic ventricular EFs in any of the subjects. A decrease in O2PCP was significantly related to nonfatal cardiac events in the HFrEF/HFmrEF group (log rank test, p = 0.01), whereas O2P% and O2PCP did not predict severe acute exacerbations of COPD. The findings of this study may clarify the utility of O2P and O2PCP, and may contribute to the currently used interpretation algorithm and the strategy for managing patients, especially those with HFrEF/HFmrEF. (Trial registration number NCT05189301.).

Contribution of Peripheral Chemoreceptors to Exercise Intolerance in Heart Failure

Peripheral chemoreceptors (PChRs), because of their strategic localization at the bifurcation of the common carotid artery and along the aortic arch, play an important protective role against hypoxia. Stimulation of PChRs evokes hyperventilation and hypertension to maintain adequate oxygenation of critical organs. A relationship between increased sensitivity of PChRs (hyperreflexia) and exercise intolerance (ExIn) in patients with heart failure (HF) has been previously reported. Moreover, some studies employing an acute blockade of PChRs (e.g., using oxygen or opioids) demonstrated improvement in exercise capacity, suggesting that hypertonicity is also involved in the development of ExIn in HF. Nonetheless, the precise mechanisms linking dysfunctional PChRs to ExIn remain unclear. From the clinical perspective, there are two main factors limiting exercise capacity in HF patients: subjective perception of dyspnoea and muscle fatigue. Both have many determinants that might be influenced by abnormal signalling from PChRs, including: exertional hyperventilation, oscillatory ventilation, ergoreceptor oversensitivity, and augmented sympathetic tone. The latter results in reduced muscle perfusion and altered muscle structure. In this review, we intend to present the milieu of abnormalities tied to malfunctioning PChRs and discuss their role in the complex relationships leading, ultimately, to ExIn.

ACUTE TRANSCRANIAL DIRECT CURRENT STIMULATION (tDCS) IMPROVES VENTILATORY VARIABILITY AND AUTONOMIC MODULATION IN RESISTANT HYPERTENSIVE PATIENTS

Here, we assessed the impact of one session of transcranial direct current stimulation (tDCS) or SHAM (20 min, each) on ventilatory responses to cardiopulmonary exercise test, central and peripheral blood pressure (BP), and autonomic modulation in resistant hypertensive (RHT) patients. RHT subjects (n = 13) were randomly submitted to SHAM and tDCS crossing sessions (1 week of "washout"). Patients and a technician who set the tDCS/Sham room up were both blind. After brain stimulation, patients were submitted to a cardiopulmonary exercise test to evaluate ventilatory and cardiovascular response to exercise. Hemodynamic (Finometer®, Beatscope), and autonomic variables were measured at baseline (before tDCS/Sham) and after incremental exercise. RESULTS: Our study shows that tDCS condition improved heart rate recovery, VO2 peak, and vagal modulation (after cardiopulmonary exercise test); attenuated the ventilatory variability response, central and peripheral blood pressure well as sympathetic modulation (after cardiopulmonary exercise test) in comparison with SHAM. These data suggest that acute tDCS sessions prevented oscillatory ventilation behavior during the cardiopulmonary exercise test and mitigated the increase of systolic blood pressure in RHT patients. After the exercise test, tDCS promotes better vagal reentry and improved autonomic modulation, possibly reducing central blood pressure and aortic augmentation index compared to SHAM. Brazilian Registry of Clinical Trials (ReBEC): https://ensaiosclinicos.gov.br/rg/RBR-8n7c9p.

Listing Criteria for Heart Transplant: Role of Cardiopulmonary Exercise Test and of Prognostic Scores

Patients with advanced heart failure (AdHF) have a reduced quality of life and poor prognosis. A heart transplant (HT) is an effective treatment for such patients. Still, because of a shortage of donor organs, the final decision to place a patient without contraindications on the HT waiting list is based on detailed risk-benefit analysis. Cardiopulmonary exercise tests (CPETs) play a pivotal role in guiding selection in patients with AdHF considered for an HT. Furthermore, several validated multivariable predicting scores obtained through various techniques, including the CPETs, are available and part of the decision-making process for HT listing.

Clinical Interpretation of Cardiopulmonary Exercise Testing: Current Pitfalls and Limitations

Several shortcomings on cardiopulmonary exercise testing (CPET) interpretation have shed a negative light on the test as a clinically useful tool. For instance, the reader should recognize patterns of dysfunction based on clusters of variables rather than relying on rigid interpretative algorithms. Correct display of key graphical data is of foremost relevance: prolixity and redundancy should be avoided. Submaximal dyspnea ratings should be plotted as a function of work rate (WR) and ventilatory demand. Increased work of breathing and/or obesity may normalize peak oxygen uptake (V̇O₂) despite a low peak WR. Among the determinants of V̇O₂, only heart rate is measured during non-invasive CPET. It follows that in the absence of findings suggestive of severe impairment in O₂ delivery, the boundaries between inactivity and early cardiovascular disease are blurred in individual subjects. A preserved breathing reserve should not be viewed as evidence that "the lungs" are not limiting the subject. In this context, measurements of dynamic inspiratory capacity are key to uncover abnormalities germane to exertional dyspnea. A low end-tidal partial pressure for carbon dioxide may indicate either increased "wasted" ventilation or alveolar hyperventilation; thus, direct measurements of arterial (or arterialized) PO₂ might be warranted. Differentiating a chaotic breathing pattern from the normal breath-by-breath noise might be complex if the plotted data are not adequately smoothed. A sober recognition of these limitations, associated with an interpretation report free from technicalities and convoluted terminology, is crucial to enhance the credibility of CPET in the eyes of the practicing physician.

[Evaluation of respiratory parameters in patients with chronic obstructive lung disease during physical exercises]

AIM

To study the relationship between the indicators of dynamic capnography and pulse oximetry with the indicators of the 6-minute walk test (6MWT) in patients with chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS

67 patients of both sexes were examined: 45 patients with COPD (age 60.02.74 years) and 25 patients of the control group (age 47.603.46 years). The study of the functional capabilities of the patients respiratory system was carried out before, during and after the 6MWT on the equipment LifeSense LS1-9R capnograph-pulse oximeter (MedAir AB).

RESULTS AND DISCUSSION

In the comparison group, the parameters of dyspnea at rest were higher than the control group (p0.05), the spirometry indices were significantly lower (p0.05). Shortness of breath as a reason for stopping/slowing down the pace during the 6MWT was noted by patients of both groups (p0.05). When analyzing the PETCO2 trend graphs, periodic breathing (PВ) was revealed. In the group of patients with COPD, signs of PВ in the analysis of the PETCO2 trend were found in 80.95% (p0.05). Regression analysis of Cox proportional risks of mortality in patients with COPD revealed the prognostic value of the following parameters of a comprehensive assessment of the patient: body mass index (BMI), BODE index, dyspnea index on the mMRS scale, Borg, forced expiratory volume in 1 second (FEV1), index Tiffno, signs of PВ, distance 6MWT, signs of PВ and desaturation during 6MWT. At the same time, the total contribution of these indicators to the risk of a lethal event was assessed (p=0.003).

CONCLUSION

When analyzing the correlation dependence, it was revealed that the presence of PВ was a prognostically unfavorable sign in patients with COPD. Predictors of an unfavorable course of COPD were BMI (23.0 kg/m2), BODE index, dyspnea indices on the mMRS, Borg, FEV1 scales, Tiffnos index, signs of PH, distance 6MST, signs of PD and desaturation during 6MST (reliability of the model coefficient p=0.003) in terms of forecast.

Roles of periodic breathing and isocapnic buffering period during exercise in heart failure

In heart failure, exercise - induced periodic breathing and end tidal carbon dioxide pressure value during the isocapnic buffering period are two features identified at cardiopulmonary exercise testing strictly related to sympathetic activation. In the present review we analysed the physiology behind periodic breathing and the isocapnic buffering period and present the relevant prognostic value of both periodic breathing and the presence/absence of the identifiable isocapnic buffering period.

Residual Exertional Dyspnea in Cardiopulmonary Disease

In cardiopulmonary medicine, residual exertional dyspnea (RED) can be defined by the persistence of limiting breathlessness in a patient who is already under the best available therapy for the underlying heart and/or lung disease. RED is a challenge to the pulmonologist because the patient (and the referring physician) assumes that the "lung doctor" should invariably provide a successful plan to fight the symptom. After presenting a simplified framework to understand the neurobiological underpinnings of dyspnea in cardiorespiratory disease, I discuss the seeds of RED associated with 1) increased metabolic cost of work, 2) increased inspiratory constraints, 3) diaphragm dysfunction, 4) impaired right ventricle preload, 5) increased central and/or peripheral chemosensitivity, 6) increased physiological dead space, 7) increased pulmonary venous and/or high left ventricle filling pressures, 8) impaired chronotropic response to exertion, and 9) increased activation of the cortical-limbic circuits. I finalize by outlining the following two common coexistence of diseases in which these multiple mechanisms interact to produce severe RED: chronic obstructive pulmonary disease-heart failure with reduced ejection fraction and chronic pulmonary fibrosis-emphysema. RED exposes the important limitations of the current reductionist approach focused only on the (over)treatment of the poorly reversible cardiopulmonary disease(s). Conversely, recognizing the existence of RED sets the stage for a more holistic approach toward one of the most devastating symptoms known to man.

Ventilation Dispersion Index as an Objective Evaluation Tool of Exercise Oscillatory Ventilation in Patients With Heart Failure

BACKGROUND

Exercise oscillatory ventilation (EOV) is related to worse prognosis in patients with heart failure (HF). However, its determination is subjective and there is no standard measure to identify it. The aim of the study was to evaluate and characterize the EOV of patients with HF using the ventilation dispersion index (VDI).

METHODS AND RESULTS

Patients underwent cardiopulmonary exercise testing (CPX), EOV was assessed by 2 reviewers and the VDI was calculated. The receiver operator curve analysis was used to assess the ability of the VDI to predict EOV. Pearson's correlation test was performed to determine the relationship between VDI and CPX variables. Forty-three patients with HF underwent CPX and were divided into 2 groups: with a VDI of less than 0.601 and a VDI of 0.601 or greater. An area under the curve of 0.759 was observed in the receiver operator curve analysis between VDI and EOV (P = .008). The VDI showed a significant correlation with the ventilatory CPX variables. According to the cut-off point obtained on the receiver operator curve, patients with a VDI of 0.601 or greater had lower left ventricular ejection fraction and higher values of resting minute ventilation and peak minute ventilation.

CONCLUSIONS

The VDI proved to be a good predictor of EOV in patients with HF.

Cardiopulmonary exercise testing may not predict appropriate implantable cardioverter defibrillator therapies in heart failure patients

Background: The prognostic value of cardiopulmonary exercise testing (CPET) variables for major cardiovascular events in patients with heart failure (HF) is widely established. However, the prognostic value of these variables as predictors of appropriate implantable cardioverter-defibrillator (ICD) therapies has not been sufficiently well addressed. This study aimed to evaluate CPET variables such as peak oxygen uptake (VO₂ peak), relationship between change in minute ventilation (VE) and carbon dioxide output (VCO₂) during incremental exercise (VE/VCO₂ slope) and exercise-related periodic breathing (EPB) as appropriate ICD therapy predictors in HF patients.Methods: We retrospectively assessed 61 HF patients who underwent CPET and had ICD implanted for primary prevention. Patients were followed for 767 ± 601 days. Primary outcome was appropriate ICD-delivered therapy, either anti-tachycardia pacing (ATP) or shock.Results: The sample consisted mostly of male patients (65.6%), with severe ventricular dysfunction (mean left ventricular ejection fraction (LVEF) 27 ± 6%). The primary outcome occurred in 20 patients (32%). There were no significant differences in VO₂ peak (17.7 ± 4.1 and 16.9 ± 4.5 mL/kg/min), VE/VCO₂ slope (39.7 ± 8.4 and 39.6 ± 10.2) or EPB prevalence (20% and 19.5%) in patients with or without appropriate ICD therapy. According to Cox regression analysis, none of the CPET variables were significant predictors of appropriate ICD therapy.Conclusions: In this cohort study of HF patients, CPET variables did not predict appropriate ICD therapies. Further studies with large number of patients are warranted to address this issue.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Heart, lungs, and muscle interplay in worsening activity-related breathlessness in advanced cardiopulmonary disease

PURPOSE OF REVIEW

Activity-related breathlessness is a key determinant of poor quality of life in patients with advanced cardiorespiratory disease. Accordingly, palliative care has assumed a prominent role in their care. The severity of breathlessness depends on a complex combination of negative cardiopulmonary interactions and increased afferent stimulation from systemic sources. We review recent data exposing the seeds and consequences of these abnormalities in combined heart failure and chronic obstructive pulmonary disease (COPD).

RECENT FINDINGS

The drive to breathe increases ('excessive breathing') secondary to an enlarged dead space and hypoxemia (largely COPD-related) and heightened afferent stimuli, for example, sympathetic overexcitation, muscle ergorreceptor activation, and anaerobic metabolism (largely heart failure-related). Increased ventilatory drive might not be fully translated into the expected lung-chest wall displacement because of the mechanical derangements brought by COPD ('inappropriate breathing'). The latter abnormalities, in turn, negatively affect the central hemodynamics which are already compromised by heart failure. Physical activity then decreases, worsening muscle atrophy and dysfunction.

SUMMARY

Beyond the imperative of optimal pharmacological treatment of each disease, strategies to lessen ventilation (e.g., walking aids, oxygen, opiates and anxiolytics, and cardiopulmonary rehabilitation) and improve mechanics (heliox, noninvasive ventilation, and inspiratory muscle training) might mitigate the burden of this devastating symptom in advanced heart failure-COPD.

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.

Exertional Periodic Breathing in Heart Failure: Mechanisms and Clinical Implications

Periodic breathing (PB) during exercise is a slow, prominent, consistent fluctuation in ventilation and derived parameters that may be persistent for the entire exercise or present only in the early phases of exercise. It is associated with a negative prognosis, particularly if concomitant with PB during sleep. Little is known about exercise-induced PB physiology, but hyperventilation is likely due to an increased sympathetic activity combined with an enhanced stimulation of intrapulmonary, chemoreceptors and metaboreceptors, low cardiac output leading to increased circulatory delay, and cerebrovascular reactivity to CO2, all with have a definite role.

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.

Exercise oscillatory ventilation and prognosis in heart failure patients with reduced and mid-range ejection fraction

AIMS

Exercise oscillatory ventilation (EOV) is a pivotal cardiopulmonary exercise test parameter for the prognostic evaluation of patients with chronic heart failure (HF). It has been described in patients with HF with reduced ejection fraction (<40%, HFrEF) and with HF with preserved ejection fraction (>50%, HFpEF), but no data are available for patients with HF with mid-range ejection fraction (40-49%, HFmrEF). The aim of the study was to evaluate the prognostic role of EOV in HFmrEF patients.

METHODS AND RESULTS

We analysed 1239 patients with HFmrEF and 4482 patients with HFrEF, enrolled in the MECKI score database, with a 2-year follow-up. The study endpoint was the composite of cardiovascular death, urgent heart transplant, and ventricular assist device implantation. We identified EOV in 968 cases (16% and 17% of cases in HFmrEF and HFrEF, respectively). HFrEF EOV+ patients were significantly older, and their parameters suggested a more severe HF than HFrEF EOV- patients. A similar behaviour was found in HFmrEF EOV+ vs. EOV- patients. Kaplan-Meier analysis, irrespective of ejection fraction, showed that EOV is associated with a worse survival, and that patients with HFrEF and HFmrEF EOV+ had a significantly worse outcome than the EOV- of the same ejection fraction groups. EOV-associated survival differences in HFmrEF patients started after 18 months of follow-up.

CONCLUSION

Exercise oscillatory ventilation has a similar prevalence and ominous prognostic value in both HFmrEF and HFrEF patients, indicating a group of patients in need of a more intensive follow-up and a more aggressive therapy. In HFmrEF, the survival curves between EOV+ and EOV- patients diverged only after 18 months.

Alterations of the respiratory system in heart failure

The review discusses mechanisms for the development of the pathology of the respiratory system in patients with CHF, such as various types of periodic respiration, pulmonary hypertension due to the pathology of the left chambers of the heart, and remodeling of the respiratory musculature. The role of chemo- and baroreceptors of the carotid zone, as well as the hyperactivation of the respiratory muscle metaboreflex in the development of the pathology of the respiratory system, and the mediated exacerbation of CHF are discussed.

Association of Oscillatory Ventilation during Cardiopulmonary Test to Clinical and Functional Variables of Chronic Heart Failure Patients

Objective

The aim of this study is to characterize the presence of exercise oscillatory ventilation (EOV) and to relate it with other cardiopulmonary exercise test (CET) responses and clinical variables.

Methods

Forty-six male patients (age: 53.1±13.6 years old; left ventricular ejection fraction [LVEF]: 30±8%) with heart failure were recruited to perform a maximal CET and to correlate the CET responses with clinical variables. The EOV was obtained according to Leite et al. criteria and VE/VCO₂ > 34 and peak VO₂ < 14 ml/kg/min were used to assess patients' severity.

Results

The EOV was observed in 16 of 24 patients who performed the CET, as well as VE/VCO₂ > 34 and peak VO₂ < 14 ml/kg/min in 14 and 10 patients, respectively. There was no difference in clinical and CET variables of the patients who presented EOV in CET when compared to non-EOV patients. Also, there was no difference in CET and clinical variables when comparing patients who presented EOV and had a VE/VCO₂ slope > 34 to patients who just had one of these responses either.

Conclusion

The present study showed that there was an incidence of patients with EOV and lower peak VO₂ and higher VE/VCO₂ slope values, but they showed no difference on other prognostic variables. As well, there was no influence of the presence of EOV on other parameters of CET in this population, suggesting that this variable may be an independent marker of worst prognosis in HF patients.

Exercise Oscillatory Ventilation: Interreviewer Agreement and a Novel Determination

INTRODUCTION

Determination of exercise oscillatory ventilation (EOV) is subjective, and the interreviewer agreement has not been reported. The purposes of this study were, among patients with heart failure (HF), as follows: 1) to determine the interreviewer agreement for EOV and 2) to describe a novel, objective, and quantifiable measure of EOV.

METHODS

This was a secondary analysis of the HEART Camp: Promoting Adherence to Exercise in Patients with Heart Failure study. EOV was determined through a blinded review by six individuals on the basis of their interpretation of the EOV literature. Interreviewer agreement was assessed using Fleiss kappa (κ). Final determination of EOV was based on agreement by four of the six reviewers. A new measure (ventilation dispersion index; VDI) was calculated for each test, and its ability to predict EOV was assessed with the receiver operator characteristics curve.

RESULTS

Among 243 patients with HF (age, 60 ± 12 yr; 45% women), the interreviewer agreement for EOV was fair (κ = 0.303) with 10-s discrete data averages and significantly better, but only moderate (κ = 0.429) with 30-s rolling data averages. Prevalence rates of positive and indeterminate EOVs were 18% and 30% with the 10-s discrete averages and 14% and 13% with the 30-s rolling averages, respectively. VDI was strongly associated with EOV, with areas under the receiver operator characteristics curve of 0.852 to 0.890.

CONCLUSIONS

Interreviewer agreement for EOV in patients with HF is fair to moderate, which can negatively affect risk stratification. VDI has strong predictive validity with EOV; as such, it might be a useful measure of prognosis in patients with HF.

ECG derived Cheyne-Stokes respiration and periodic breathing are associated with cardiorespiratory arrest in intensive care unit patients

BACKGROUND

Cheyne-Stokes respiration and periodic breathing (CSRPB) have not been studied sufficiently in the intensive care unit setting (ICU).

OBJECTIVES

To determine whether CSRPB is associated with adverse outcomes in ICU patients.

METHODS

The ICU group was divided into quartiles by CSRPB (86 patients in quartile 1 had the least CSRPB and 85 patients in quartile 4 had the most CSRPB). Adverse outcomes (emergent intubation, cardiorespiratory arrest, inpatient mortality and the composite of all) were compared between patients with most CSRPB (quartile 4) and those with least CSRPB (quartile 1).

RESULTS

ICU patients in quartile 4 had a higher proportion of cardiorespiratory arrests (5% versus 0%, (p=.042), and more adverse events over all (19% versus 8%, p=.041) as compared to patients in quartile 1.

CONCLUSIONS

CSRPB can be measured in the ICU and it's severity is associated with adverse outcomes in critically ill patients.

The Role of Gas Exchange Variables in Cardiopulmonary Exercise Testing for Risk Stratification and Management of Heart Failure with Reduced Ejection Fraction

Heart failure with reduced ejection fraction (HFrEF) is common in the developed world and results in significant morbidity and mortality. Accurate risk assessment methods and prognostic variables are therefore needed to guide clinical decision making for medical therapy and surgical interventions with the ultimate goal of decreasing risk and improving health outcomes. The purpose of this review is to examine the role of cardiopulmonary exercise testing (CPET) and its most commonly used ventilatory gas exchange variables for the purpose of risk stratification and management of HFrEF. We evaluated five widely studied gas exchange variables from CPET in HFrEF patients based on nine previously used systematic criteria for biomarkers. This paper provides clinicians with a comprehensive and critical overview, class recommendations and evidence levels. Although some CPET variables met more criteria than others, evidence supporting the clinical assessment of variables beyond peak V̇O₂ is well-established. A multi-variable approach also including the V̇_E-V̇CO₂ slope and EOV is therefore recommended.

Analysis of Exercise-Induced Periodic Breathing Using an Autoregressive Model and the Hilbert-Huang Transform

Evaluation of exercise-induced periodic breathing (PB) in cardiopulmonary exercise testing (CPET) is one of important diagnostic evidences to judge the prognosis of chronic heart failure cases. In this study, we propose a method for the quantitative analysis of measured ventilation signals from an exercise test. We used an autoregressive (AR) model to filter the breath-by-breath measurements of ventilation from exercise tests. Then, the signals before reaching the most ventilation were decomposed into intrinsic mode functions (IMF) by using the Hilbert-Huang transform (HHT). An IMF represents a simple oscillatory pattern which catches a part of original ventilation signal in different frequency band. For each component of IMF, we computed the number of peaks as the feature of its oscillatory pattern denoted by Δ_i. In our experiment, 61 chronic heart failure patients with or without PB pattern were studied. The computed peaks of the third and fourth IMF components, Δ₃ and Δ₄, were statistically significant for the two groups (both p values < 0.02). In summary, our study shows a close link between the HHT analysis and level of intrinsic energy for pulmonary ventilation. The third and fourth IMF components are highly potential to indicate the prognosis of chronic heart failure.

Periodic Breathing during Incremental Exercise

Periodic breathing during incremental cardiopulmonary exercise testing is a regularly recurring waxing and waning of tidal volume due to oscillations in central respiratory drive. Periodic breathing is a sign of respiratory control system instability, which may occur at rest or during exercise. The possible mechanisms responsible for exertional periodic breathing might be related to any instability of the ventilatory regulation caused by: (1) increased circulatory delay (i.e., circulation time from the lung to the brain and chemoreceptors due to reduced cardiac index leading to delay in information transfer), (2) increase in controller gain (i.e., increased central and peripheral chemoreceptor sensitivity to arterial partial pressure of oxygen and of carbon dioxide), or (3) reduction in system damping (i.e., baroreflex impairment). Periodic breathing during exercise is observed in several cardiovascular disease populations, but it is a particularly frequent phenomenon in heart failure due to systolic dysfunction. The detection of exertional periodic breathing is linked to outcome and heralds worse prognosis in heart failure, independently of the criteria adopted for its definition. In small heart failure cohorts, exertional periodic breathing has been abolished with several dedicated interventions, but results have not yet been confirmed. Accordingly, further studies are needed to define the role of visceral feedbacks in determining periodic breathing during exercise as well as to look for specific tools for preventing/treating its occurrence in heart failure.

Minute-Ventilation Variability during Cardiopulmonary Exercise Test is Higher in Sedentary Men Than in Athletes

BACKGROUND

The occurrence of minute-ventilation oscillations during exercise, named periodic breathing, exhibits important prognostic information in heart failure. Considering that exercise training could influence the fluctuation of ventilatory components during exercise, we hypothesized that ventilatory variability during exercise would be greater in sedentary men than athletes.

OBJECTIVE

To compare time-domain variability of ventilatory components of sedentary healthy men and athletes during a progressive maximal exercise test, evaluating their relationship to other variables usually obtained during a cardiopulmonary exercise test.

METHODS

Analysis of time-domain variability (SD/n and RMSSD/n) of minute-ventilation (Ve), respiratory rate (RR) and tidal volume (Vt) during a maximal cardiopulmonary exercise test of 9 athletes and 9 sedentary men was performed. Data was compared by two-tailed Student T test and Pearson´s correlations test.

RESULTS

Sedentary men exhibited greater Vt (SD/n: 1.6 ± 0.3 vs. 0.9 ± 0.3 mL/breaths; p < 0.001) and Ve (SD/n: 97.5 ± 23.1 vs. 71.6 ± 4.8 mL/min x breaths; p = 0.038) variabilities than athletes. VE/VCO2 correlated to Vt variability (RMSSD/n) in both groups.

CONCLUSIONS

Time-domain variability of Vt and Ve during exercise is greater in sedentary than athletes, with a positive relationship between VE/VCO2 pointing to a possible influence of ventilation-perfusion ratio on ventilatory variability during exercise in healthy volunteers.

Prognostic Significance of Central Apneas Throughout a 24-Hour Period in Patients With Heart Failure

BACKGROUND

Large trials using noninvasive mechanical ventilation to treat central apnea (CA) occurring at night ("sleep apnea") in patients with systolic heart failure (HF) have failed to improve prognosis. The prevalence and prognostic value of CA during daytime and over an entire 24-h period are not well described.

OBJECTIVES

This study evaluated the occurrence and prognostic significance of nighttime, daytime, and 24-h CA episodes in a large cohort of patients with systolic HF.

METHODS

Consecutive patients receiving guideline-recommended treatment for HF (n = 525; left ventricular ejection fraction [LVEF] of 33 ± 9%; 66 ± 12 years of age; 77% males) underwent prospective evaluation, including 24-h respiratory recording, and were followed-up using cardiac mortality as an endpoint.

RESULTS

The 24-h prevalence of predominant CAs (apnea/hypopnea index [AHI] ≥5 events/h, with CA of >50%) was 64.8% (nighttime: 69.1%; daytime: 57.0%), whereas the prevalence of predominant obstructive apneas (OA) was 12.8% (AHI ≥5 events/h with OAs >50%; nighttime: 14.7%; daytime: 5.9%). Episodes of CA were associated with neurohormonal activation, ventricular arrhythmic burden, and systolic/diastolic dysfunction (all p < 0.05). During a median 34-month follow-up (interquartile range [IQR]: 17 to 36 months), 50 cardiac deaths occurred. Nighttime, daytime, and 24-h moderate-to-severe CAs were associated with increased cardiac mortality (AHI of </≥15 events/h; log-rank: 6.6, 8.7, and 5.3, respectively; all p < 0.05; central apnea index [CAI] of </≥10 events/h; log-rank 8.9, 11.2, and 10.9, respectively; all p < 0.001). Age, B-type natriuretic peptide level, renal dysfunction, 24-h AHI, CAI, and time with oxygen saturation of <90% were independent predictors of outcome.

CONCLUSIONS

In systolic HF patients, CAs occurred throughout a 24-h period and were associated with a neurohormonal activation, ventricular arrhythmic burden, and worse prognosis.