Relation between oscillatory ventilation at rest before cardiopulmonary exercise testing and prognosis in patients with left ventricular dysfunction

A Systematic Approach for the Interpretation of Cardiopulmonary Exercise Testing in Children with Focus on Cardiovascular Diseases

Cardiopulmonary exercise testing (CPET) is the clinical standard for children with congenital heart disease (CHD), heart failure (HF) being assessed for transplantation candidacy, and subjects with unexplained dyspnea on exertion. Heart, lung, skeletal muscle, peripheral vasculature, and cellular metabolism impairment frequently lead to circulatory, ventilatory, and gas exchange abnormalities during exercise. An integrated analysis of the multi-system response to exercise can be beneficial for differential diagnosis of exercise intolerance. The CPET combines standard graded cardiovascular stress testing with simultaneous ventilatory respired gas analysis. This review addresses the interpretation and clinical significance of CPET results with specific reference to cardiovascular diseases. The diagnostic values of commonly obtained CPET variables are discussed using an easy-to-use algorithm for physicians and trained nonphysician personnel in clinical practice.

Exercise oscillatory ventilation: Mechanisms and prognostic significance

Alteration in breathing patterns characterized by cyclic variation of ventilation during rest and during exercise has been recognized in patients with advanced heart failure (HF) for nearly two centuries. Periodic breathing (PB) during exercise is known as exercise oscillatory ventilation (EOV) and is characterized by the periods of hyperpnea and hypopnea without interposed apnea. EOV is a non-invasive parameter detected during submaximal cardiopulmonary exercise testing. Presence of EOV during exercise in HF patients indicates significant impairment in resting and exercise hemodynamic parameters. EOV is also an independent risk factor for poor prognosis in HF patients both with reduced and preserved ejection fraction irrespective of other gas exchange variables. Circulatory delay, increased chemosensitivity, pulmonary congestion and increased ergoreflex signaling have been proposed as the mechanisms underlying the generation of EOV in HF patients. There is no proven treatment of EOV but its reversal has been noted with phosphodiesterase inhibitors, exercise training and acetazolamide in relatively small studies. In this review, we discuss the mechanistic basis of PB during exercise and the clinical implications of recognizing PB patterns in patients with HF.

An overview of the applied definitions and diagnostic methods to assess exercise oscillatory ventilation--a systematic review

The variable "exercise oscillatory ventilation" (EOV), assessed during cardiopulmonary exercise test (CPET), recently became a fundamental prognostic parameter in patients with heart failure. In literature, various definitions are suggested, but an uniformly accepted description to identify EOV still lacks. We performed a systematic review of the literature in order to determine the different definitions and diagnostic techniques to assess EOV. A systematic search strategy was established and executed in seven databases (PubMed, Google Scholar, Cochrane Clinical Trials, Science Direct, Pedro, Web Of Science library and Medline (Ovid)) resulting in 605 citations after de-duplication. Full-text articles (n=124) were assessed for eligibility, resulting in 75 citations. The review accounted 17,440 patients of whom 4,638 subjects presented EOV. Seven studies described EOV in a non-heart failure population accounting 168 EOV subjects. The definitions could be categorized in nine subdivisions of which four (n=43) referred to an original description. The other subdivisions were combinations of the original definitions (n=11), quantifications (n=4), computational (n=3), vaguely described (n=8) or not defined (n=6). Symptom limited maximal exercise tests were conducted to assess EOV, however the modes, protocols, software and data sampling were divers. Heterogeneity in the numerous definitions to identify EOV and the vaguely described assessment methods are hindering the evolution to a standardized uniformly accepted definition and technique to identify this abnormal breathing pattern. Unity in definition and international adopted assessment is warranted to strengthen its validity as a prognostic marker and could promote communication. It may facilitate clinical trials on pathophysiology and origin of EOV.

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.

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.

Cheyne-stokes breathing and reduced ejection fraction

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Clinical usefulness of response profiles to rapidly incremental cardiopulmonary exercise testing

The advent of microprocessed "metabolic carts" and rapidly incremental protocols greatly expanded the clinical applications of cardiopulmonary exercise testing (CPET). The response normalcy to CPET is more commonly appreciated at discrete time points, for example, at the estimated lactate threshold and at peak exercise. Analysis of the response profiles of cardiopulmonary responses at submaximal exercise and recovery, however, might show abnormal physiologic functioning which would not be otherwise unraveled. Although this approach has long been advocated as a key element of the investigational strategy, it remains largely neglected in practice. The purpose of this paper, therefore, is to highlight the usefulness of selected submaximal metabolic, ventilatory, and cardiovascular variables in different clinical scenarios and patient populations. Special care is taken to physiologically justify their use to answer pertinent clinical questions and to the technical aspects that should be observed to improve responses' reproducibility and reliability. The most recent evidence in favor of (and against) these variables for diagnosis, impairment evaluation, and prognosis in systemic diseases is also critically discussed.

Clinical significance of awake oscillatory ventilation in patients with heart failure and effects of open-heart surgery

BACKGROUND

Although sleep apnea has recently become a concern in patients with congestive heart failure (CHF), some patients with CHF exhibit characteristic oscillatory ventilation (OV) even when they are awake. We investigated the clinical significance of OV in patients with CHF, and effects of open-heart surgery on the OV.

HYPOTHESIS

OV is an indicator of the severity of CHF, and this abnormal respiratory pattern improves with hemodynamic changes after open-heart surgery.

METHODS

According to respiratory pattern in the cardiopulmonary exercise testing (CPX) before cardiac surgery, 50 patients with CHF were divided into 14 patients of OV-positive (OV+) and 36 patients of OV-negative (OV-). Then, the several indices of CPX before surgery, 1 week and 6 months after surgery were compared between the 2 groups.

RESULTS

The peak VO2 before surgery was lower in OV+ patients than those in OV- patients (15.3 vs 18.8 m1/min/kg, p < 0.05). One week after surgery, anaerobic threshold (AT) and end-tidal C02 (ETC02) were lower in OV+ patients than those in OV- patients (AT: 9.5 vs 10,7 ml/min/kg, p < 0.05, ETCO2: 5.3 vs 5.6%, p < 0.05). However, 6 months after surgery, the statistical differences of these CPX parameters between the 2 groups were not found, and OV disappeared in 79% of OV+ patients.

CONCLUSIONS

These data suggest that OV is an indicator of the severity of CHF, and gradually improved with the open-heart surgery.

Exertional oscillatory ventilation during cardiopulmonary exercise test in Fontan patients with total cavopulmonary connection

Exertional oscillatory ventilation (EOV) has been noted during cardiopulmonary exercise testing (CPX) in patients with heart failure. EOV is a predictor of poor prognosis in adult patients with heart failure. The objective of this study was to clarify the incidence and influence of EOV in Fontan patients. Symptom-limited CPX was performed in 36 Fontan patients at 12.3 +/- 4.3 (6.5-24.4) years of age or 5.9 +/- 2.0 (3.0-11.2) years after total cavopulmonary connection (TCPC). Mean age at the time of TCPC was 6.3 +/- 3.3. All 36 TCPC patients were classified as New York Heart Association classification I or II. They also underwent cardiac catheterization subsequently. EOV was defined as cyclic fluctuations in minute ventilation at rest that persist during effort lasting >or=60% of the exercise duration, with an amplitude >or=15% of the average resting value. EOV was noted in 21 of 36 Fontan patients (58%) with good clinical status. Univariable analysis between Fontan patients with and those without EOV showed significant differences in age at TCPC (p < 0.05), age at CPX (p < 0.02), weight at CPX (p < 0.02), follow-up duration between TCPC and CPX (p < 0.04), ventricular morphology (p < 0.05), and metabolic equivalents (p < 0.05) and peak minute oxygen uptake (VO(2)) per body weight (p < 0.05). Multivariable analysis showed that EOV was significantly related to peak VO(2) per kilogram. In conclusion, EOV was frequently noted during exercise in Fontan patients with good clinical status. EOV during exercise seems to be related to higher peak VO(2) per kilogram and younger age at TCPC, which is a contrary result to those for adult patients with chronic heart failure. EOV is a remarkable phenomenon during exercise to compensate for impaired cardiopulmonary function in Fontan patients.

Prognostic ability of resting periodic breathing and ventilatory variation in closely matched patients with heart failure

PURPOSE

Periodic breathing (PB), characterized by waxing and waning oscillations of ventilation, has been reported in some patients with heart failure. Although PB is usually assessed in sleeping patients, PB has also been observed in awake patients. We tested the hypothesis that PB in awake, resting patients with heart failure predicts mortality.

METHODS

Resting gas exchange data were collected in consecutive, awake patients with heart failure referred for possible cardiac transplantation. Periodic breathing was defined as oscillations of resting ventilation, that is, 30% or more during 2 consecutive cycles. Each PB patient was matched to a comparison patient by age, gender, heart failure etiology, peak oxygen consumption, peak respiratory exchange ratio, and ventilatory efficiency slope.

RESULTS

Forty-four of 355 patients met the criteria for PB and were matched to 44 comparison patients. During an average follow-up of 4.9 +/- 0.1 years, 30 patients with PB (68%) versus 23 comparisons (52%) died or were transplanted urgently (P = NS). However, among the 88 PB patients and comparisons, ventilatory variation was an independent predictor of mortality by Cox regression analysis (P = .004). Resting ventilatory variation increased the explained variation in mortality by 44%, from 16% to 23%, in a mortality model that included ventilatory efficiency slope, peak oxygen consumption, left ventricular ejection fraction, systolic blood pressure, sex, age, heart rate, and etiology.

CONCLUSION

Resting ventilatory variation independently and powerfully predicted mortality in this cohort of patients with heart failure.

Exercise oscillatory breathing and increased ventilation to carbon dioxide production slope in heart failure: an unfavorable combination with high prognostic value

BACKGROUND

Increased slope of exercise ventilation to carbon dioxide production (VE/VCO2) is an established prognosticator in patients with heart failure. Recently, the occurrence of exercise oscillatory breathing (EOB) has emerged as an additional strong indicator of survival.

OBJECTIVE

The aim of this study is to define the respective prognostic significance of these variables and whether excess risk may be identified when either respiratory disorder is present.

METHODS

In 288 stable chronic HF patients (average left ventricular ejection fraction, 33 +/- 13%) who underwent cardiopulmonary exercise testing, the prognostic relevance of VE/VCO2 slope, EOB, and peak VO2 was evaluated by multivariate Cox regression.

RESULTS

During a mean interval of 28 +/- 13 months, 62 patients died of cardiac reasons. Thirty-five percent presented with EOB. Among patients exhibiting EOB, 54% had an elevated VE/VCO2 slope. The optimal threshold value for the VE/VCO2 slope identified by receiver operating characteristic analysis was < 36.2 or > or = 36.2 (sensitivity, 77%; specificity, 64%; P < .001). Univariate predictors of death included low left ventricular ejection fraction, low peak VO2, high VE/VCO2 slope, and EOB presence. Multivariate analysis selected EOB as the strongest predictor (chi2, 46.5; P < .001). The VE/VCO2 slope (threshold, < 36.2 or > or = 36.2) was the only other exercise test variable retained in the regression (residual chi2, 5.9; P = .02). The hazard ratio for subjects with EOB and a VE/VCO2 slope > or = 36.2 was 11.4 (95% confidence interval, 4.9-26.5; P < .001).

CONCLUSION

These findings identify EOB as a strong survival predictor even more powerful than VE/VCO2 slope. Exercise oscillatory breathing presence does not necessarily imply an elevated VE/VCO2 slope, but combination of either both yields to a burden of risk remarkably high.

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

BACKGROUND

Patients with heart failure (HF) display a number of breathing abnormalities including periodic breathing (PB) at rest. Although the mechanism(s) contributing to PB remain unclear, we examined whether changes in pulmonary wedge pressure (PWP) and pulmonary vascular resistance (PVR) alter PB in patients with established HF.

METHODS

We studied 12 male patients with HF (age, 50 +/- 11 years; ejection fraction, 18.3 +/- 3.8 %; New York Heart Association class, 3.2 +/- 0.4), with PB at rest, who are undergoing right heart catheterization with infusion of nitroprusside.

RESULTS

At baseline, patients with HF displayed minute ventilation (V(E)) oscillations with amplitude of 5.5 +/- 2.7 L/min (57 +/- 34% of the average V(E)) and cycle length of 61 +/- 18 seconds. Cardiac index (CI), PVR, and mean PWP averaged 2.0 +/- 0.4 L min(-1) m(-2), 281.9 +/- 214.9 dyne/s per cm(-5), and 28.3 +/- 5.4 mm Hg, respectively. During nitroprusside infusion, CI increased to 3.1 +/- 0.6 L min(-1) m(-2), PVR decreased to 163.9 +/- 85.2 dyne/s per cm(-5), and PWP fell to 10.0 +/- 4.2 mm Hg. Nitroprusside reduced the amplitude (2.6 +/- 2.4 L/min, 23 +/- 21% of average V(E); P < .01) and cycle length (41.4 +/- 28.8 seconds; P < .01) of V(E) oscillations while abolishing oscillations in 3 patients. Although average V(E) and PaCO2 remained unchanged, there was a significant increase in the ratio of tidal volume to inspiratory time (V(T)/T(I); P < .01), suggesting an increase in ventilatory drive. The change in the amplitude of V(E) oscillations was positively correlated with the change in PWP (r = 0.75; P < .01), negatively correlated with the change in PVR (r = 0.63; P < .05), and not correlated with the change in CI.

CONCLUSIONS

These data suggest that PWP (left atrial pressure) may play a direct role in the PB observed in HF at rest.

Interferon-gamma inhibits STAT6 signal transduction and gene expression in human airway epithelial cells

The activating and inhibitory cytokine signals that act upon epithelial cells in the human lung are critically important for controlling the production of inflammatory mediators from those cells in the context of allergic disease. The cytokines interleukin (IL)-4 and IL-13, derived from T helper (Th)-2 cells and other cell types, are potent inducers of epithelial cell expression of a host of inflammatory molecules, including the chemokines eotaxin-1, -2 and -3. Intracellular signal transduction in response to IL-4/IL-13 occurs largely through activation of signal transducer and activator of transcription 6 (STAT6). Interferon (IFN)-gamma, a Th1-type cytokine, has opposing effects to IL-4/IL-13 in various cell types, including T cells, B-cells, endothelium, and epithelium. In this study, we demonstrate that IL-4-induced STAT6 activation was inhibited profoundly by 24 h pretreatment with IFN-gamma in human primary airway epithelial cell cultures. Using Western blotting, we showed that the levels of both cytoplasmic and nuclear-localized phospho-STAT6 were reduced by IFN-gamma pretreatment, and this effect was dependent on the concentration of IFN-gamma and time of exposure to IFN-gamma. The functional activity of STAT6 was also completely inhibited by IFN-gamma: IL-4-induced luciferase activity from a STAT6-driven reporter construct was suppressed, as was IL-4-induced expression of messenger RNA (mRNA) and protein for eotaxin-3, a STAT6-dependent gene implicated in allergic inflammation. We found that mRNA for suppressor of cytokine signaling (SOCS)-1 and (SOCS)-3, known inhibitors of IL-4 signaling, and IL-13 receptor alpha2, a potential inhibitor of IL-4 signaling, were both strongly induced by IFN-gamma pretreatment. IFN-gamma also increased the rate of decay of IL-4-induced eotaxin-3 mRNA. We conclude that there are multiple mechanisms by which IFN-gamma regulates IL-4- and STAT6-dependent signaling and gene expression in airway epithelial cells. These observations have important implications for the regulation of epithelial cell activation by the balance of Th1/Th2-type cytokines in the airways in allergic disease.