The partial pressure of resting end-tidal carbon dioxide predicts major cardiac events in patients with systolic heart failure

Evaluation of the relationship between end-tidal carbon dioxide level and heart failure classification

OBJECTIVE

Heart failure is a disease with cardiac dysfunction, and its morbidity and mortality are associated with the degree of dysfunction. The New York Heart Association classifies the heart failure stages based on the severity of symptoms and physical activity. End-tidal carbon dioxide refers to the level of carbon dioxide that a person exhales with each breath. End-tidal carbon dioxide levels can be used in many clinical conditions such as heart failure, asthma, and chronic obstructive pulmonary disease. The aim of the study was to reveal the relationship between end-tidal carbon dioxide levels and the New York Heart Association classification of heart failure stages.

METHODS

This study was conducted at Kahramanmaraş Sütçü İmam University Faculty of Medicine Adult Emergency Department between 01/03/2019 and 01/09/2019. A total of 80 patients who presented to the emergency department with a history of heart failure or were diagnosed with heart failure during admission were grouped according to the New York Heart Association classification of heart failure stages. The laboratory parameters, ejection fraction values, and end-tidal carbon dioxide levels of the patients were measured and recorded in the study forms.

RESULTS

End-tidal carbon dioxide levels and ejection fraction values were found to be significantly lower in the stage 4 group compared to the other groups. Furthermore, pro-B-type natriuretic peptide (BNP) values were found to be significantly higher in stage 4 group compared to the other groups.

CONCLUSION

It was concluded that end-tidal carbon dioxide levels could be used together with pro-BNP and ejection fraction values in determining the severity of heart failure.

Cardiopulmonary Exercise Test in heart failure: A Sine qua non

A robust literature, over the last years, supports the indication of cardiopulmonary exercise testing (CPET) in patients with cardiovascular diseases. Understanding exercise physiology is a crucial component of the critical evaluation of exercise intolerance. Shortness of breath and exercise limitation is often treated with an improper focus, partly because the pathophysiology is not well understood in the frame of the diagnostic spectrum of each subspecialty. A vital field and research area have been cardiopulmonary exercise test in heart failure with preserved/reduced ejection fraction, evaluation of heart failure patients as candidates for LVAD-Implantation, as well as for LVAD-Explantation and ultimately for heart transplantation. All the CPET variables provide synergistic prognostic discrimination. However, Peak VO2 serves as the most critical parameter for risk stratification and prediction of survival rate.

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.

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.

Capnography in the Emergency Department: A Review of Uses, Waveforms, and Limitations

BACKGROUND

Capnography has many uses in the emergency department (ED) and critical care setting, most commonly cardiac arrest and procedural sedation.

OBJECTIVE OF THE REVIEW

This review evaluates several indications concerning capnography beyond cardiac arrest and procedural sedation in the ED, as well as limitations and specific waveforms.

DISCUSSION

Capnography includes the noninvasive measurement of CO₂, providing information on ventilation, perfusion, and metabolism in intubated and spontaneously breathing patients. Since the 1990s, capnography has been utilized extensively for cardiac arrest and procedural sedation. Qualitative capnography includes a colorimetric device, changing color on the amount of CO₂ present. Quantitative capnography provides a numeric value (end-tidal CO₂), and capnography most commonly includes a waveform as a function of time. Conditions in which capnography is informative include cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Patients with seizure, trauma, and respiratory conditions, such as pulmonary embolism and obstructive airway disease, can benefit from capnography, but further study is needed. Limitations include use of capnography in conditions with mixed pathophysiology, patients with low tidal volumes, and equipment malfunction. Capnography should be used in conjunction with clinical assessment.

CONCLUSIONS

Capnography demonstrates benefit in cardiac arrest, procedural sedation, mechanically ventilated patients, and patients with metabolic acidemia. Further study is required in patients with seizure, trauma, and respiratory conditions. It should only be used in conjunction with other patient factors and clinical assessment.

Low partial pressure of end-tidal carbon dioxide predicts left ventricular assist device implantation in patients with advanced chronic heart failure

BACKGROUND

This study aimed to clarify the prognostic impact of partial pressure of end-tidal carbon dioxide (PETCO₂) in patients with advanced chronic heart failure (HF).

METHODS

Forty-eight patients (mean age 43.1±11.9years, 32 males) with chronic HF (44 with non-ischemic and 4 with ischemic cardiomyopathy) were prospectively enrolled. Echocardiography, blood tests, pulmonary function testing, and PETCO₂ measurements were performed as noninvasive tests, whereas right heart catheterization and arterial blood gas analysis were conducted as invasive tests. The primary end point of this study was left ventricular assist device (LVAD) implantation or cardiac death.

RESULTS

Eighteen patients underwent LVAD implantation at the Interagency Registry for Mechanically Circulatory Support (INTERMACS) profile 3 during the follow-up period, and no patient died. PETCO₂ was significantly lower in a stepwise manner with New York Heart Association functional class (class I or II, 34.2±9.3mmHg vs. class III or IV, 27.7±2.5mmHg; p<0.001). Univariate and multivariate Cox proportional hazard models and time-dependent receiver operating characteristic curve analysis revealed that PETCO₂≤31mmHg is an independent noninvasive predictor of LVAD implantation. Univariable and multivariable linear regression analyses showed that pulmonary arterial pressure was independently and highly correlated with PETCO₂ (r²=-0.512, p<0.001).

CONCLUSIONS

Among various noninvasive clinical parameters investigated, PETCO₂ was the independent predictor of LVAD implantation at the INTERMACS profile 3 in patients with chronic HF. Pulmonary congestion may significantly contribute to decreases in PETCO₂ in patients with HF.

Skeletal Muscle Changes in Chronic Cardiac Disease and Failure

Peak exercise performance in healthy man is limited not only by pulmonary or skeletal muscle function but also by cardiac function. Thus, abnormalities in cardiac function will have a major impact on exercise performance. Many cardiac diseases affect exercise performance and indeed for some cardiac conditions such as atherosclerotic heart disease, exercise testing is frequently used not only to measure functional capacity but also to make a diagnosis of heart disease, evaluate the efficacy of treatment, and predict prognosis. Early in the course of cardiac diseases, exercise performance will be minimally affected but with disease progression impairment in exercise capacity will become apparent. Ejection fraction, that is, the percent of blood volume ejected with each cardiac cycle is often used as a measure of cardiac performance but frequently there is a dissociation between the ejection fraction and exercise capacity in patients with heart disease. How abnormalities in cardiac function impacts the muscles, vasculature, and lungs to impact exercise performance will here be reviewed. The focus of this work will be on patients with systolic heart failure as the incidence and prevalence of heart failure is reaching epidemic proportions and heart failure is the end result of many other chronic cardiac diseases. The prognostic role of exercise and benefits of exercise training will also be discussed.

Usefulness of decrease in oxygen uptake efficiency to identify gas exchange abnormality in patients with idiopathic pulmonary arterial hypertension

Background

Decline in oxygen uptake efficiency (OUE), especially during exercise, is found in patients with chronic heart failure. In this study we aimed to test the validity and usefulness of OUE in evaluating gas exchange abnormality of patients with idiopathic pulmonary arterial hypertension (IPAH).

Methods

We retrospectively investigated the cardiopulmonary exercise test (CPET) with gas exchange measurements in 32 patients with confirmed IPAH. All patients also had resting hemodynamic measurements and pulmonary function test (PFT). Sixteen healthy subjects, matched by age, sex, and body size were used as controls, also had CPET and PFT measurements.

Results

In IPAH patients, the magnitude of absolute and percentage of predicted (%pred) oxygen uptake efficiency slope (OUES) and oxygen uptake efficiency plateau (OUEP), as well as several other CPET parameters, were strikingly worse than healthy subjects (P<0.0001). Pattern of changes in OUE in patients is similar to that in controls, In IPAH patients, OUE values at rest, warming up, anaerobic threshold and peak exercise were all significantly lower than in normal (P<0.0001). OUEP%pred, better than OUES%pred, correlated significantly with New York Heart Association (NYHA) functional Class (r = −0.724, P<0.005), Total Pulmonary Vascular Resistance (TPVR) (r = −0.694, P<0.005), diffusing capacity for carbon monoxide (DL_CO) (r = 0.577, P<0.05), and the lowest ventilation versus CO₂ output ratio during exercise (LowestV˙E/V˙CO₂) (r = −0.902, P<0.0001). In addition, the coefficient of variation (COV) of OUEP was lower (20.9%) markedly than OUES (34.3%) (P<0.0001).

Conclusions

In patients with IPAH, OUES and OUEP are both significantly lower than the healthy subjects. OUEP is a better physiological parameter than OUES in evaluating the gas exchange abnormality of patients with IPAH.

Development of a composite model derived from cardiopulmonary exercise tests to predict mortality risk in patients with mild-to-moderate heart failure

OBJECTIVE

Cardiopulmonary exercise testing (CPET) is used to predict outcome in patients with mild-to-moderate heart failure (HF). Single CPET-derived variables are often used, but we wanted to see if a composite score achieved better predictive power.

METHODS

Retrospective analysis of patient records at the department of cardiology, Castle Hill Hospital, Kingston-upon-Hull. 387 patients (median (25th-75th percentile)) (age 65 (56-72) years; 79% men; LVEF 34 (31-37) %) were included. Patients underwent a symptom-limited, maximal CPET on a treadmill. During a median follow-up of 8.6±2.1 years in survivors, 107 patients died. Survival models were built and validated using a hybrid approach between the bootstrap and Cox regression. Nine CPET-derived variables were included. Z-score defined each variable's predictive strength. Model coefficients were converted to a risk score.

RESULTS

Four CPET-related variables were independent predictors of all-cause mortality in the survival model: the presence of exertional oscillatory ventilation (EOV), increasing slope of the relation between ventilation and carbon dioxide production (VE/VCO2 slope), decreasing oxygen uptake efficiency slope (OUES), and an increase in the lowest ventilatory equivalent for carbon dioxide (VEqCO2 nadir). Individual predictors of mortality ranged from 0.60 to 0.71 using Harrell's C-statistic, but the optimal combination of EOV+VE/VCO2 slope+OUES+VEqCO2 nadir reached 0.75. The Hull CPET risk score had a significantly higher area under the curve (0.78) when compared to the HF Survival Score (AUC=0.70; p<0.001).

CONCLUSIONS

A composite risk score using variables from CPET out-performs the traditional single variable approach in predicting outcome in patients with mild-to-moderate HF.

Respiratory drive and breathing pattern abnormalities are related to exercise intolerance in chronic heart failure patients

BACKGROUND

Patients with chronic heart failure (CHF) are characterized by exercise intolerance and ventilatory abnormalities that are related to poor prognosis. We hypothesized that CHF patients have increased respiratory drive and abnormal breathing pattern during exercise in relation to disease severity.

MATERIALS AND METHODS

The study population consisted of 219 stable CHF patients and 30 healthy control subjects. All subjects underwent a symptom-limited cardiopulmonary exercise testing (CPET), pulmonary function tests, measurement of the maximal inspiratory pressure (PImax) and respiratory drive (P0.1). Measurements included peak oxygen uptake ( [Formula: see text] peak, ml/kg/min). Respiratory drive was measured by mouth occlusion pressure P0.1 and P0.1/PImax ratio at rest, and by mean inspiratory flow (VT/TI) at rest and during exercise. CHF patients were divided into 3 groups according to [Formula: see text] peak (Group A: >20, Group B: 20-16 and Group C: <16ml/kg/min).

RESULTS

CHF patients presented higher P0.1/PImax (4.1±3.6 vs 3.0±1.5, p=0.007) and VT/TI at rest (0.48±0.14 vs 0.41±0.10, L/s respectively, p=0.004) and lower VT/TI at peak exercise (2.17±0.66 vs 2.56±0.73, L/s, p=0.009) compared to controls. P0.1/PImax was higher in CHF Group C vs B vs A (4.9±2.9 vs 3.6±1.8 vs 3.1±1.8, respectively, p<0.001), while VT/TI at peak exercise was lower (1.71±0.43 vs 2.15±0.52 vs 2.65±0.64, L/s, respectively, p<0.001).

CONCLUSIONS

CHF patients present increased respiratory drive at rest and abnormal breathing pattern during exercise in relation to CHF severity.

Do optimal prognostic thresholds in continuous physiological variables really exist? Analysis of origin of apparent thresholds, with systematic review for peak oxygen consumption, ejection fraction and BNP

Background

Clinicians are sometimes advised to make decisions using thresholds in measured variables, derived from prognostic studies.

Objectives

We studied why there are conflicting apparently-optimal prognostic thresholds, for example in exercise peak oxygen uptake (pVO₂), ejection fraction (EF), and Brain Natriuretic Peptide (BNP) in heart failure (HF).

Data Sources and Eligibility Criteria

Studies testing pVO₂, EF or BNP prognostic thresholds in heart failure, published between 1990 and 2010, listed on Pubmed.

Methods

First, we examined studies testing pVO₂, EF or BNP prognostic thresholds. Second, we created repeated simulations of 1500 patients to identify whether an apparently-optimal prognostic threshold indicates step change in risk.

Results

33 studies (8946 patients) tested a pVO₂ threshold. 18 found it prognostically significant: the actual reported threshold ranged widely (10–18 ml/kg/min) but was overwhelmingly controlled by the individual study population's mean pVO₂ (r = 0.86, p<0.00001). In contrast, the 15 negative publications were testing thresholds 199% further from their means (p = 0.0001). Likewise, of 35 EF studies (10220 patients), the thresholds in the 22 positive reports were strongly determined by study means (r = 0.90, p<0.0001). Similarly, in the 19 positives of 20 BNP studies (9725 patients): r = 0.86 (p<0.0001).

Second, survival simulations always discovered a “most significant” threshold, even when there was definitely no step change in mortality. With linear increase in risk, the apparently-optimal threshold was always near the sample mean (r = 0.99, p<0.001).

Limitations

This study cannot report the best threshold for any of these variables; instead it explains how common clinical research procedures routinely produce false thresholds.

Key Findings

First, shifting (and/or disappearance) of an apparently-optimal prognostic threshold is strongly determined by studies' average pVO₂, EF or BNP. Second, apparently-optimal thresholds always appear, even with no step in prognosis.

Conclusions

Emphatic therapeutic guidance based on thresholds from observational studies may be ill-founded. We should not assume that optimal thresholds, or any thresholds, exist.

Prognostic value of resting pulmonary function in heart failure

BACKGROUND

The heart and lungs are intimately linked anatomically and physiologically, and, as a result, heart failure (HF) patients often develop changes in pulmonary function. This study examined the prognostic value of resting pulmonary function (PF) in HF.

METHODS AND RESULTS

In all, 134 HF patients (enrolled from January 1, 1999 Through December 31, 2005; ejection fraction (EF) = 29% ± 11%; mean age = 55 ± 12 years; 65% male) were followed for 67 ± 34 months with death/transplant confirmed via the Social Security Index and Mayo Clinic registry. PF included forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), diffusing capacity of the lungs for carbon monoxide (DLCO), and alveolar volume (VA). Patients were divided in tertiles according to PF with survival analysis via log-rank Mantel-Cox test with chi-square analysis. Groups for FVC included (1) >96%, (2) 96% to 81%, and (3) <81% predicted (chi-square = 18.9, P < 0.001). Bonferroni correction for multiple comparisons (BC) suggested differences between groups 1 and 3 (P < 0.001) and 2 and 3 (P = 0.008). Groups for FEV1 included (1) >94%, (2) 94% to 77%, and (3) <77% predicted (chi-square = 17.3, P <0.001). BC suggested differences between groups 1 and 3 (P <0.001). Groups for DLCO included (1) >90%, (2) 90% to 75%, and (3) <75% predicted (chi-square = 11.9, P = 0.003). BC suggested differences between groups 1 and 3 (P < 0.001). Groups for VA included (1) >97%, (2) 97% to 87%, and (3) <87% predicted (Chi-square = 8.5, P = 0.01). BC suggested differences between groups 1 and 2 (P = 0.014) and 1 and 3 (P = 0.003).

CONCLUSIONS

In a well-defined cohort of HF patients, resting measures of PF are predictive of all-cause mortality.

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.

Prognostic value of capnography during rest and exercise in patients with heart failure

New variables obtained from cardiopulmonary exercise testing (CPX) have received attention in recent years, in particular the partial pressure of end-tidal carbon dioxide (P(ET) CO(2) ). The purpose of this study was to therefore comprehensively assess the ability of resting and exercise P(ET) CO(2) to predict major cardiac events in a heart failure (HF) cohort referred for CPX. A total of 963 patients with systolic HF undergoing symptom-limited CPX were included in the analysis. Resting and exercise P(ET) CO(2) along with other CPX variables were determined, and patients were followed for major adverse events. With regard to resting measures, multivariate analysis revealed that left ventricular ejection fraction was the most robust prognostic marker (P<.001) while resting P(ET) CO(2) added significant predictive value and was retained in the regression (P<.001). When exercise data were considered, the multivariate analysis revealed that the P(ET) CO(2) apex during exercise added predictive value and was retained (P<.05). In what is the largest evaluation of P(ET) CO(2) in the assessment of systolic HF patients to date, the authors substantiate prior (smaller) studies showing prognostic utility of P(ET) CO(2) , both as a resting measure (an important potential screening tool) and during exercise. These data add to the rationale to incorporate P(ET) CO(2) as a routine monitoring component in HF management.

Cardiopulmonary exercise testing: relevant but underused

Cardiopulmonary exercise testing (CPX) is a relatively old technology, but has sustained relevance for many primary care clinical scenarios in which it is, ironically, rarely considered. Advancing computer technology has made CPX easier to administer and interpret at a time when our aging population is more prone to comorbidities and higher prevalence of nonspecific symptoms of exercise intolerance and dyspnea, for which CPX is particularly useful diagnostically and prognostically. These discrepancies in application are compounded by patterns in which CPX is often administered and interpreted by cardiology, pulmonary, or exercise specialists who limit their assessments to the priorities of their own discipline, thereby missing opportunities to distinguish symptom origins. When used properly, CPX enables the physician to assess fitness and uncover cardiopulmonary issues at earlier phases of work-up, which would therefore be especially useful for primary care physicians. In this article, we provide an overview of CPX principles and testing logistics, as well as some of the clinical contexts in which it can enhance patient care.

Excess ventilation during exercise and prognosis in chronic heart failure

Excess ventilation during exercise with accompanying dyspnea is characteristic of chronic heart failure (CHF), and these patients often exhibit increased Ve relative to the Vco(2) compared with normal subjects. This can be measured in several ways, including using such variables as the slope of Ve versus Vco(2), the lowest ratio of Ve/Vco(2), and the ratio of Ve/Vco(2) at the lactic acidosis threshold or peak exercise. There is now considerable evidence that the degree of excess ventilation during exercise in patients with CHF is a robust predictor of outcome and identifies higher-risk patients requiring aggressive treatment, including heart transplantation. The mechanism of excess ventilation in patients with CHF during exercise is not completely understood. It may be related to enhanced output of chemoreceptors or peripheral muscle ergoreceptors, increased dead space/Vt ratio due to increased contribution of high ventilation-perfusion lung regions or rapid shallow breathing caused by earlier onset of lactic acidosis, or likely resulting from a combination of these causes.

Ordering a cardiopulmonary exercise test for your patient: key considerations for the physician

Cardiopulmonary exercise testing (CPX) is a specialized exercise assessment that provides valuable information in a number of patient populations. Physicians are often familiar with standard exercise testing procedures (i.e., the cardiac stress test) and, therefore, appropriately refer patients with signs/symptoms suggestive of myocardial ischemia. However, the procedures surrounding referral for CPX, and the relevance of the data obtained, may not be as widely understood in the medical community. The purpose of the current special report is to provide physicians referring patients for CPX with information on the appropriateness of CPX referral and testing logistics, the identification of an appropriate CPX laboratory for referral, and definitions on key CPX variables that should be included in the final report.

Submaximal exercise gas exchange is an important prognostic tool to predict adverse outcomes in heart failure

AIMS

Traditionally, VO(2peak) has been used to determine prognosis in heart failure; however, this measure has limitations. Hence, other exercise and gas exchange parameters measured submaximally, e.g. breathing efficiency (V(E)/VCO(2)), end-tidal CO(2) (P(ET)CO(2)), oxygen uptake efficiency slope (OUES), and circulatory power [ systolic blood pressure (SBP)], have been investigated. The aim of this study was to investigate the prognostic relevance of submaximal exercise gas exchange in heart failure patients. Method and results One hundred and thirty-two consecutive heart failure patients (mean age 56 ± 12 years, ejection fraction 29 ± 11%) performed peak treadmill testing. Gas exchange and haemodynamic variables were measured continuously. Gas exchange data obtained from the first 2 min of exercise and at a respiratory exchange ratio (RER) of 0.9 were the measurements of interest. Over a median follow-up period of 62.4 (range 0-114) months, there were 44 endpoints (death or transplant). Univariate analysis demonstrated submaximal predictors of survival, which included V(E)/VCO(2) slope and ratio, P(ET)CO(2), OUES, and circulatory power (P ≤ 0.01). When these and additional submaximal variables were included together in the multivariable analysis, the strongest submaximal exercise predictive model (C-statistic 0.75) comprised data from the first stage of exercise (V(E) and circulatory power) and at an RER of 0.9 (V(E)/VCO(2) ratio). The inclusion of VO(2 peak) and demographic data, with submaximal data (V(E)/VCO(2) ratio at an RER = 0.9), increased the predictiveness of the model (C-statistic 0.78).

CONCLUSION

Submaximal exercise measures provide useful prognostic information for predicting survival in heart failure. This form of testing is logistically easier, cheaper, and safer for patients compared with maximal exercise.

Cardiopulmonary exercise testing variables reflect the degree of diastolic dysfunction in patients with heart failure-normal ejection fraction

PURPOSE

Previous investigations have reported a relationship between variables obtained from echocardiography with tissue Doppler imaging (TDI) and cardiopulmonary exercise testing (CPX) in systolic heart failure (HF) cohorts. The purpose of the present investigation was to perform a comparative analysis between echocardiography with TDI and CPX in patients with HF and normal ejection fraction (NEF).

METHODS

Patients with HF-NEF (N = 32) underwent echocardiography with TDI and CPX to determine the following variables: (1) the ratio between mitral early velocity (E) and mitral annular velocity (E'), (2) ejection fraction, (3) left ventricular (LV) mass, (4) left ventricular end systolic volume, (5) peak oxygen uptake (.VO2), (6) ventilatory efficiency, (7) the partial pressure of end-tidal carbon dioxide (P(ET)CO2) at rest and peak exercise, and (8) heart rate recovery at 1 minute (HRR1).

RESULTS

Pearson correlation revealed that E/E' was significantly correlated with peak oxygen uptake (r = -0.55, P = .001), the ventilatory efficiency slope (r = 0.60, P < .001), resting P(ET)CO2 (r = -0.39, P = .03), peak P(ET)CO2 (r = -0.50, P = .004), and HRR1 (r = -0.63, P < .001). Left ventricular mass and left ventricular end systolic volume were not correlated with any CPX variable. Ejection fraction was correlated with HRR1 (r = -0.55, P = .001). An HRR1 threshold of less than 16 and/or 16 or more beats per minute (higher value positive) effectively identified subjects with an E/E' > 10 (positive likelihood ratio: 13:2).

DISCUSSION

E/E' provides an accurate reflection of LV filling pressure and thus, insight into diastolic function. The results of the present investigation indicate CPX provides insight into cardiac dysfunction in patients with HF-NEF and thus, may eventually prove to be a valuable and accepted clinical assessment.

The future of aerobic exercise testing in clinical practice: is it the ultimate vital sign?

The four traditional vital signs: resting heart rate, blood pressure, respiratory rate and body temperature, serve as the cornerstone of a physical examination. Other assessments such as pain have been proposed as additional vital signs. To this point however, there has been limited consideration for aerobic exercise assessment as a vital sign. A wealth of literature demonstrating the prognostic, diagnostic and interventional value of the aerobic exercise assessment now exists, supporting its use in numerous clinical scenarios. Moreover, the assessment of the aerobic exercise response allows for the manifestation of physiologic abnormalities that are not readily apparent during the collection of resting data. This review will provide evidence supporting the assertion that the aerobic exercise assessment may be afforded vital sign status in future clinical practice.

The Clinical Utility of Cardiopulmonary Exercise Testing in Suspected or Confirmed Myocardial Ischemia

Heart disease is a major cause of morbidity and mortality in the United States, with coronary artery disease (CAD) representing more than half of all cardiovascular events. Stable patients presenting with symptoms suggestive of CAD are likely to undergo an exercise electrocardiogram (ECG) and/ or imaging study as a first-line diagnostic assessment. A cardiopulmonary exercise test (CPX) is an ECG stress test plus ventilatory gas analysis. Recently, CPX has been used to detect exercise-induced myocardial ischemia (EIMI) suggestive of underlying CAD. Two CPX variables, oxygen pulse (VO2/HR) and the slope of oxygen consumption versus work rate (Δ VO2/ Δ WR), have been identified to be especially indicative of EIMI. Currently, there are a number of diagnostic tests available for the identification of CAD, with the most widely used being stress ECG, stress myocardial perfusion imaging (MPI) and echocardiography, and cardiac catheterization. Exercise ECG, although inexpensive, has a number of well-recognized limitations, including low sensitivity resulting in false-negative results. Stress (exercise or pharmaceutically induced) MPI and catheterization are more accurate but also more invasive and expensive. It appears that CPX may improve the diagnostic accuracy of exercise ECG. This review will address the potential utility of CPX in patients with suspected or confirmed myocardial ischemia.

Mechanisms by which exercise training benefits patients with heart failure

Clinical consequences of heart failure are fatigue, dyspnea, and progressive impairment of exercise tolerance. Regular exercise training is associated with health-improving effects. In patients with stable heart failure, exercise training can relieve symptoms, improve exercise capacity and quality of life, as well as reduce hospitalization and, to some extent, risk of mortality. Progressive exercise training is associated with pulmonary, cardiovascular, and skeletal muscle metabolic adaptations that increase oxygen delivery and energy production. This Review focuses on current knowledge of mechanisms by which progressive and moderate exercise training can have sustained beneficial effects on patients with heart failure.

Determining the preferred percent-predicted equation for peak oxygen consumption in patients with heart failure

BACKGROUND

Peak oxygen consumption (Vo(2)) is routinely assessed in patients with heart failure undergoing cardiopulmonary exercise testing. The purpose of the present investigation was to determine the prognostic ability of several established peak Vo(2) prediction equations in a large heart failure cohort.

METHODS AND RESULTS

One thousand one hundred sixty-five subjects (70% males; age, 57.0+/-13.8 years; ischemic etiology, 43%) diagnosed with heart failure underwent cardiopulmonary exercise testing. Percent-predicted peak Vo(2) was calculated according to normative values proposed by Wasserman and Hansen (equation), Jones et al (equation), the Cooper Clinic (below low fitness threshold), a Veteran's Administration male referral data set (4 equations), and the St James Take Heart Project for women (equation). The prognostic significance of percent-predicted Vo(2) values derived from the 2 latter, sex-specific equations were assessed collectively. There were 179 major cardiac events (117 deaths, 44 heart transplantations, and 18 left ventricular assist device implantations) during the 2-year tracking period (annual event rate, 10%). Measured peak Vo(2) and all percent-predicted peak Vo(2) calculations were significant univariate predictors of adverse events (chi(2)> or =31.9, P<0.001) and added prognostic value to ventilatory efficiency (VE/Vco(2) slope), the strongest cardiopulmonary exercise testing predictor of adverse events (chi(2)=150.7, P<0.001), in a multivariate regression. The Wasserman/Hansen prediction equation provided optimal prognostic information.

CONCLUSIONS

Actual peak Vo(2) and the percent-predicted models included in this analysis all were significant predictors of adverse events. It seems that the percent-predicted peak Vo(2) value derived from the Wasserman/Hansen equations may outperform other expressions of this cardiopulmonary exercise testing variable.

Metabolic parameters derived from cardiopulmonary stress testing for prediction of prognosis in patients with heart failure: the ochsner experience

Cardiopulmonary parameters, particularly peak oxygen consumption, have proven utility in prognostic stratification for patients with heart failure. These have been typically corrected for total body weight as opposed to lean body mass (LBM). For practical purposes, fat consumes virtually no oxygen and receives minimal perfusion. Based on this rationale and on observations from previous studies, several investigations conducted at the Ochsner Clinic Foundation have assessed the prognostic value of metabolic parameters when corrected for LBM. Three studies reviewed in this discussion consistently found greater prognostic value for LBM-corrected parameters, especially peak oxygen consumption and oxygen pulse. These findings lead to a strong recommendation for LBM correction of cardiopulmonary exercise stress test-derived parameters for more accurate prognostic stratification in patients with heart failure, especially in the obese population. Other centers have studied additional parameters such as the ventilation to carbon dioxide production slope, oxygen uptake efficiency slope, and partial pressure of end-tidal carbon dioxide during exercise and rest. In multiple studies, these ventilation-dependent parameters have shown prognostic superiority compared with the standard peak oxygen consumption even when obtained from submaximal exercise data. However, no study to our knowledge has compared these parameters with LBM-adjusted values as described herein. The prognostic validity of cardiopulmonary exercise stress test-derived parameters requires further investigation in patients treated with β-blockers.