Exercise-related ventilatory abnormalities and survival in congestive heart failure

Effects of Sacubitril/Valsartan on Exercise Capacity in Patients with Heart Failure with Reduced Ejection Fraction and the Role of Percentage of Delayed Enhancement Measured by Cardiac Magnetic Resonance in Predicting Therapeutic Response: A Multicentre Study

Background: This study aims to evaluate the cardiopulmonary effects of sacubitril/valsartan therapy in patients with heart failure with reduced ejection fraction (HFrEF), investigating a possible correlation with the degree of myocardial fibrosis, as assessed by cardiac magnetic resonance. Methods: A total of 134 outpatients with HFrEF were enrolled. Results: After a mean follow-up of 13.3 ± 6.6 months, an improvement in ejection fraction and a reduction in E/A ratio, inferior vena cava size and N-terminal pro-B-type natriuretic peptide levels were observed. At follow-up, we observed an increase in VO₂ peak of 16% (p<0.0001) and in O₂ pulse of 13% (p=0.0002) as well as an improvement in ventilatory response associated with a 7% reduction in the VE/VCO₂ slope (p=0.0001). An 8% increase in the ΔVO₂/Δ work ratio and an 18% increase in exercise tolerance were also observed. Multivariate logistic regression analysis showed that the main predictors of events during follow-up were VE/VCO₂ slope >34 (OR 3.98; 95% CI [1.59-10.54]; p=0.0028); ventilatory oscillatory pattern (OR 4.65; 95% CI [1.55-16.13]; p=0.0052); and haemoglobin level (OR 0.35; 95% CI [0.21-0.55]; p<0.0001). In patients who had cardiac magnetic resonance, when delayed enhancement >4.6% was detected, a lower response after sacubitril/valsartan therapy was observed as expressed by improvement in ΔVO₂ peak, O₂ pulse, LVEF and N-terminal pro-B-type natriuretic peptide. No significant differences were observed in ΔVO₂/Δ work and VE/VCO₂ slope. Conclusion:Sacubitril/valsartan improves cardiopulmonary functional capacity in HFrEF patients. The presence of myocardial fibrosis on cardiac magnetic resonance is a predictor of response to therapy.

Analysis of Blood Pressure and Ventilation Efficiency in Different Types of Obesity Aged 40-60 Years by Cardiopulmonary Exercise Test

PURPOSE

This study investigated blood pressure and ventilation efficiency by cardiopulmonary exercise test (CPX) in different types of obesity aged 40-60 years.

MATERIAL AND METHODS

The inclusion criteria of this cross-sectional study were adults aged 40-60 years underwent health checks. CPX was measured according to the relevant standards. According to different body mass index (BMI), there were 3 groups, BMI<24 (kg/m²), 24≤BMI<28 (kg/m²) and BMI≥28 (kg/m²). There were two groups in male, waist circumference≥90 (cm) and waist circumference<90 (cm). Similarly, there were two groups in female, waist circumference≥85 (cm) and waist circumference<85 (cm).

RESULTS

There were 543 individuals (64.6% male and 35.4% female) aged 40-60 years in this study. The resting blood pressure (BP) and peak BP have the significant differences in different BMI groups (p < 0.001) and male or female groups (p < 0.001). However, the resting DBP (77.70±9.45 vs 81.16±8.80, p < 0.001) and peak DBP (85.67±10.21 vs 89.03±9.94, p = 0.002) have the significant differences in different male waist circumference groups, and the resting BP (SBP 113.76±14.29 vs 121.86±15.54, p = 0.001, DBP 71.95±10.83 vs 77.27±11.42, p = 0.005) has the significant differences in different female waist circumference groups. Carbon dioxide Ventilation equivalent (VE/VCO₂) has the significant differences in different male waist circumference groups (26.84±3.10 vs 27.68±2.93, p = 0.009), but it has not the significant differences in different BMI groups and different female waist circumference groups. The oxygen pulse (VO₂/HR) is slightly higher in female group than male group (0.93±0.15 vs 0.89±0.15, p = 0.001). Breathing reserve has the statistical significance in BMI ≥28 group compared with the BMI <24 group (0.52±0.13 vs 0.46±0.17, ηp²=0.021).

CONCLUSION

We found that the blood pressure and ventilation efficiency of CPX were different between the obesity and normal. This will provide a basis for accurate cardiopulmonary assessment of obesity.

Prognostic Value of Peak Oxygen Uptake in Patients Supported With Left Ventricular Assist Devices (PRO-VAD)

OBJECTIVES

The purpose of this study was to examine whether peak oxygen uptake (pVO₂) and other cardiopulmonary exercise test (CPET)-derived variables could predict intermediate-term mortality in stable continuous flow LVAD recipients.

BACKGROUND

pVO₂ is a cornerstone in the selection of patients for heart transplantation, but the prognostic power of pVO₂ obtained in patients treated with a left ventricular assist device (LVAD) is unknown.

METHODS

We collected data for pVO₂ and outcomes in adult LVAD recipients in a retrospective, multicenter study and evaluated cutoff values for pVO₂ including: 1) values above or below medians; 2) grouping patients in tertiles; and 3) pVO₂ ≤14 ml/kg/min if the patient was not treated with beta-blockers (BB) or pVO₂ ≤12 ml/kg/min if the patient was taking BB therapy.

RESULTS

Nine centers contributed data from 450 patients. Patients were 53 ± 13 years of age; 78% were male; body mass index was 25 ± 5 kg/m² with few comorbidities (stroke: 11%; diabetes: 18%; and peripheral artery disease: 4%). The cause of heart failure (HF) was most often nonischemic (66%). Devices included were the HeartMate II and 3 (Abbott); and Heartware ventricular assist devices Jarvik and Duraheart (Medtronic). The index CPET was performed at a median of 189 days (154 days-225 days) after LVAD implantation, and mean pVO₂ was 14.1 ± 5 ml/kg/min (47% ± 14% of predicted value). Lower pVO₂ values were strongly associated with poorer survival regardless of whether patients were analyzed for absolute pVO₂ in ml/kg/min, pVO₂ ≤12 BB/14 ml/kg/min, or as a percentage of predicted pVO₂ values (P ≤ 0.001 for all). For patients with pVO₂ >12 BB/14 and ventilation/carbon dioxide relationship (VE/VCO₂) slope <35, the 1-year survival was 100%.

CONCLUSIONS

Even after LVAD implantation, pVO₂ has prognostic value, similar to HF patients not supported by mechanical circulatory support devices. (PROgnostic Value of Exercise Capacity Measured as Peak Oxygen Uptake [pVO₂] in Recipients of Left Ventricular Assist Devices [PRO-VAD]; NCT04423562).

Minute ventilation/carbon dioxide production in chronic heart failure

In chronic heart failure, minute ventilation (V'_E) for a given carbon dioxide production (V'_CO2 ) might be abnormally high during exercise due to increased dead space ventilation, lung stiffness, chemo- and metaboreflex sensitivity, early metabolic acidosis and abnormal pulmonary haemodynamics. The V'_E versus V'_CO2 relationship, analysed either as ratio or as slope, enables us to evaluate the causes and entity of the V'_E/perfusion mismatch. Moreover, the V'_E axis intercept, i.e. when V'_CO2 is extrapolated to 0, embeds information on exercise-induced dead space changes, while the analysis of end-tidal and arterial CO₂ pressures provides knowledge about reflex activities. The V'_E versus V'_CO2 relationship has a relevant prognostic power either alone or, better, when included within prognostic scores. The V'_E versus V'_CO2 slope is reported as an absolute number with a recognised cut-off prognostic value of 35, except for specific diseases such as hypertrophic cardiomyopathy and idiopathic cardiomyopathy, where a lower cut-off has been suggested. However, nowadays, it is more appropriate to report V'_E versus V'_CO2 slope as percentage of the predicted value, due to age and gender interferences. Relevant attention is needed in V'_E versus V'_CO2 analysis in the presence of heart failure comorbidities. Finally, V'_E versus V'_CO2 abnormalities are relevant targets for treatment in heart failure.

Early Effects of Sacubitril/Valsartan on Exercise Tolerance in Patients with Heart Failure with Reduced Ejection Fraction

BACKGROUND

Sacubitril/valsartan in heart failure (HF) with reduced ejection fraction (HFrEF) was shown to be superior to enalapril in reducing the risk of death and hospitalization for HF. Our aim was to evaluate the cardiopulmonary effects of sacubitril/valsartan in patients with HFrEF.

METHODS

We conducted an observational study. Ninety-nine ambulatory patients with HFrEF underwent serial cardiopulmonary exercise tests (CPET) after initiation of sacubitril/valsartan in addition to recommended therapy.

RESULTS

At baseline, 37% of patients had New York Heart Association (NYHA) class III. After a median follow-up of 6.2 months (range 3⁻14.9 months) systolic blood pressure decreased from 117 ± 14 to 101 ± 12 mmHg (p < 0.0001), left ventricular ejection fraction (LVEF) increased from 27 ± 6 to 29.7 ± 7% (p < 0.0001), peak oxygen consumption (VO₂) improved from 14.6 ± 3.3 (% of predicted = 53.8 ± 14.1) to 17.2 ± 4.7 mL/kg/min (% of predicted = 64.7 ± 17.8) (p < 0.0001), minute ventilation/carbon dioxide production relationship (VE/VCO₂ Slope) decreased from 34.1 ± 6.3 to 31.7 ± 6.1 (p = 0.006), VO₂ at anaerobic threshold increased from 11.3 ± 2.6 to 12.6 ± 3.5 mL/kg/min (p = 0.007), oxygen pulse increased from 11.5 ± 3.0 to 13.4 ± 4.3 mL/kg/min (p < 0.0001), and ∆VO₂/∆Work increased from 9.2 ± 1.5 to 10.1 ± 1.8 mL/min/watt (p = 0.0002).

CONCLUSION

Sacubitril/valsartan improved exercise tolerance, LVEF, peak VO₂, and ventilatory efficiency at 6.2 months follow-up. Further studies are necessary to better clarify underlying mechanisms of this functional improvement.

Prognostic ability of VE/VCO2 slope calculations using different exercise test time intervals in subjects with heart failure

BACKGROUND

The minute ventilation-carbon dioxide production (VE/VCO2) slope, obtained during exercise testing, possesses prognostic value in heart failure (HF). The VE-VCO2 relationship is generally linear thereby hypothetically producing similar slope values regardless of the exercise-test time interval used for calculation.

DESIGN

This study assesses the ability of the VE/VCO2 slope, calculated at different time intervals throughout a progressive exercise test, to predict 1-year cardiac-related hospitalization and mortality in subjects with HF.

METHODS

Seventy-two subjects underwent symptom-limited exercise testing with ventilatory expired gas analysis. Mean age and left ventricular ejection fraction for 44 male and 28 female subjects were 51.2 years (+/-13.0) and 27.0% (+/-12.3) respectively. The VE/VCO2 slope was calculated from time 0 to 25, 50, 75 and 100% of exercise time and subsequently used to create five randomly selected VE/VCO2 slope categories.

RESULTS

(The intraclass correlation coefficient found calculation of the VE/VCO2 slope, when divided into quartiles, to be a reliable measure (alpha=0.94, P<0.0001). Univariate Cox regression analysis revealed all VE/VCO2 slope categories (25-100% and random selections) were significant predictors of cardiac-related hospitalization and mortality over a 1-year period. Multivariate Cox regression analysis revealed all VE/VCO2 slope categories outperformed peak oxygen consumption (VO2) in predicting hospitalization and mortality at 1 year.

CONCLUSIONS

Although the different classification schemes were not identical, these results suggest VE/VCO2 slope maintains prognostic significance regardless of exercise-test time interval. Calculation of VE/VCO2 slope may therefore still be valuable in subjects putting forth a sub-maximal effort while effort-dependent measures, such as peak VO2, are not.

Statement on cardiopulmonary exercise testing in chronic heart failure due to left ventricular dysfunction: recommendations for performance and interpretation Part III: Interpretation of cardiopulmonary exercise testing in chronic heart failure and future applications: Task Force of the Italian Working Group on Cardiac Rehabilitation and Prevention (Gruppo Italiano di Cardiologia Riabilitativa e Prevenzione, GICR), endorsed by Working Group on Cardiac Rehabilitation and Exercise Physiology of the European Society of Cardiology

Optimal use of cardiopulmonary exercise testing (CPET) in clinical practice and chronic heart failure (CHF) requires appropriate data presentation and a flexible interpretative strategy. The greatest potential impact on the decision-making process may rest not on the value of any individual measurement, although some are obviously more important than others, but rather on their integrative use. Such an integrative approach relies on interrelationship, trending phenomena and patterns of key gas exchange variable responses. An multiparametric approach will be discussed in different clinical applications, for exercise prescription and monitoring, functional evaluation of drug therapy or cardiac resynchronisation therapy efficacy, and risk stratification. The role of CPET in the daily clinical decision-making process will be underscored. Future indications of CPET will be addressed, suggesting and promoting an extended candidacy either to all CHF patients, including those at high risk or most vulnerable, such as female, elderly patients, and patients with implantable cardioverter defibrillator or in every clinical setting where objective definition of exercise capacity provides implications for medical, surgical, and social decision making.

Prognostic value of oxygen consumption and ventilatory equivalent slope in female candidates referred for heart transplantation--experience of a single Asian center

BACKGROUND

Ventilatory equivalent (ventilation/CO2 production, VE/VCO2) slope has been suggested to be a much more accurate predicator than peak oxygen consumption (VO2) during exercise for prognosis in patients with heart failure. However, patients tested were predominately male.

METHODS

To investigate whether peak VO2 and VE/VCO2 slope predict the prognosis of female patients with heart failure, we retrospectively collected data of 39 female candidates referred for heart transplantation (HTx) from 2004 to 2011. Both peak VO2 and VE/VCO2 slope were obtained from the results of an exercise pulmonary function test. The outcome was death or mechanical devices implantation or HTx. Logistic regression was used for data analysis.

RESULTS

Mean age and heart failure survival score were 55.8 ± 13.7 years and 7.3 ± 0.7, respectively. Each increment of VE/VCO2 slope decreased 2-year event-free rate (odds ratio [OR] = 0.88, 95% confidence interval [CI] = 0.79 to 0.98) in the female group. The predictions of VE/VCO2 slope for 1-year event-free survival did not reach statistical significance (OR = 0.92, 95% CI = 0.84 to 1.00). On the other hand, peak VO2 was not a strong predictor for 1- and 2-year event-free survival (OR = 1.22 and 1.16, 95% CI = 0.96 to 1.55 and 0.94 to 1.44, respectively).

CONCLUSIONS

Impairment in exercise ventilation holds a clinical and long-term prognostic impact in female patients with heart failure. The role of peak VO2 during exercise in prognostic prediction among the cohort should be further investigated.

The long-term prognostic significance of 6-minute walk test distance in patients with chronic heart failure

Background. The 6-minute walk test (6-MWT) is used to assess patients with chronic heart failure (CHF). The prognostic significance of the 6-MWT distance during long-term followup (>5 years) is unclear. Methods. 1,667 patients (median [inter-quartile range, IQR]) (age 72 [65–77]; 75% males) with heart failure due to left ventricular systolic impairment undertook a 6-MWT as part of their baseline assessment and were followed up for 5 years. Results. At 5 years' followup, those patients who died (n = 959) were older at baseline and had a higher log NT pro-BNP than those who survived to 5 years (n = 708). 6-MWT distance was lower in those who died [163 (153) m versus 269 (160) m; P < 0.0001]. Median 6-MWT distance was 300 (150–376) m, and quartile ranges were <46 m, 46–240 m, 241–360 m, and >360 m. 6-MWT distance was a predictor of all-cause mortality (HR 0.97; 95% CI 0.96-0.97; Chi-square = 184.1; P < 0.0001). Independent predictors of all-cause mortality were decreasing 6-MWT distance, increasing age, increasing NYHA classification, increasing log NT pro-BNP, decreasing diastolic blood pressure, decreasing sodium, and increasing urea. Conclusion. The 6-MWT is an important independent predictor of all-cause mortality following long-term followup in patients with CHF.

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.

Reduced confounding by impaired ventilatory function with oxygen uptake efficiency slope and VE/VCO2 slope rather than peak oxygen consumption to assess exercise physiology in suspected heart failure

Heart failure and ventilatory disease often coexist; both create abnormalities in cardiopulmonary exercise test measurements. The authors evaluated the relative dependency of a well-recognized index of heart failure, peak oxygen consumption (VO(2)), and 2 newer indices, the minute ventilation (VE)/carbon dioxide production (VCO(2)) slope and oxygen uptake efficiency slope (OUES), on standard markers of impaired cardiac and ventilatory function. One hundred twenty-four patients (median age, 65.8; range, 22.6-84.9), with functional limitation from clinical heart failure were exercised. Peak VO(2) was 17.14 ± 7.58 mL/kg/min, VE/VCO(2) slope 50.1 ± 20.1, OUES 1.46 ± 0.68 L/min, and forced expiratory volume in 1 second (FEV(1) ) 1.88 ± 0.75 L. Peak VO(2) is substantially more sensitive to FEV(1) than ejection fraction (4.0 mL/kg/min difference between above- and below-median FEV(1) and 1.5 mL/kg/min between above- and below-median ejection fraction). OUES does not share this peculiar excess sensitivity to FEV(1) (0.12 L/min difference between above- and below-median FEV(1) and 0.01 L/min between above- and below-median ejection fraction). VE/VCO(2) slope has a borderline effect by FEV(1) (7.07 difference between above- and below-median FEV(1) and 2.07 between above- and below-median ejection fraction). Although widely used as a marker of heart failure severity, peak VO(2) is very sensitive to spirometry status and is indeed more affected by FEV(1) than by ejection fraction. OUES in contrast does not show this preferential sensitivity to impaired FEV(1).

Ventilatory inefficiency in major depressive disorder: a potential adjunct for cardiac risk stratification in depressive disorders?

BACKGROUND

Cardiopulmonary exercise testing (CPET) provides insights into ventilatory, cardiac and metabolic dysfunction in heart and lung diseases and might play a role in cardiac risk stratification in major depressive disorder (MDD).

OBJECTIVE

The VE/VCO(2)-slope indicates ventilatory efficiency and has been applied to stratify the cardiac risk in heart failure (HF). Therefore, the current study was conducted to evaluate and classify ventilatory efficiency and its relationship to physical fitness and disease severity in MDD.

METHODS

Exhaustive incremental exercise testing was completed by 15 female MDD patients and pair matched controls. The ventilatory threshold (VT) and the VE/VCO(2)-slope were assessed. Statistical analyses were conducted by means of MANOVAs and follow-up univariate ANOVAs.

RESULTS

In patients with MDD, significant different relative work rates and oxygen uptakes at the VT in comparison to healthy controls were observed. Furthermore, we found an increased VE/VCO(2)-slope in depressed patients. We additionally report an inverse relationship between the VE/VCO(2)-slope and peak power output as well as peak oxygen uptake solely in patients. We did not observe any association of assessed parameters with disease severity.

CONCLUSION

CPET measures indicate ventilatory inefficiency in patients with MDD. The elevated VE/VCO(2)-slope indicates that patients with MDD need to ventilate significantly more to a given amount of developing CO(2). Further investigations are needed to verify the application of the ventilatory classification system to stratify cardiovascular risk in depressive disorder.

The lowest VE/VCO2 ratio during exercise as a predictor of outcomes in patients with heart failure

BACKGROUND

The lowest minute ventilation (VE) and carbon dioxide production (VCO(2)) ratio during exercise has been suggested to be the most stable and reproducible marker of ventilatory efficiency in patients with heart failure (HF). However, the prognostic power of this index is unknown.

METHODS AND RESULTS

A total of 847 HF patients underwent cardiopulmonary exercise testing (CPX) and were followed for 3 years. The associations between the lowest VE/VCO(2) ratio, maximal oxygen uptake (peak VO(2)), the VE/VCO(2) slope, and major events (death or transplantation) were evaluated using proportional hazards analysis; adequacy of the predictive models was assessed using Akaike information criterion (AIC) weights. There were 147 major adverse events. In multivariate analysis, the lowest VE/VCO(2) ratio (higher ratio associated with greater risk) was similar to the VE/VCO(2) slope in predicting risk (hazard ratios [HR] per unit increment 2.0, 95% CI 1.1-3.4, and 2.2, 95% CI 1.3-3.7, respectively; P < .01), followed by peak VO(2) (HR 1.6, 95% CI 1.1-2.4, P=.01). Patients exhibiting abnormalities for all 3 responses had an 11.6-fold higher risk. The AIC weight for the 3 variables combined (0.94) was higher than any single response or any combination of 2. The model including all 3 responses remained the most powerful after adjustment for beta-blocker use, type of HF, and after applying different cut points for high risk.

CONCLUSIONS

The lowest VE/VCO(2) ratio adds to the prognostic power of conventional CPX responses in HF.

Ventilatory expired gas at constant-rate low-intensity exercise predicts adverse events and is related to neurohormonal markers in patients with heart failure

BACKGROUND

Ventilatory efficiency (VE/VCO(2) ratio) and the partial pressure of end-tidal carbon dioxide (P(ET)CO(2)), obtained during moderate to high levels of physical exertion demonstrate prognostic value in heart failure (HF). The present investigation assesses the clinical utility of these variables during low-intensity exercise.

METHODS AND RESULTS

One hundred and thirty subjects diagnosed with HF underwent a 2-minute, constant-rate treadmill session at 2 miles per hour. Both the VE/VCO(2) ratio and P(ET)CO(2) were recorded during exercise (30-second average) and their change (Delta) from rest. B-type and atrial natriuretic peptide (BNP and ANP) were also determined. Only P(ET)CO(2) and DeltaP(ET)CO(2) emerged from the multivariate Cox regression. Receiver operating characteristic curve analysis revealed the prognostic classification schemes were significant with thresholds of < or >or=34 mm Hg (hazard ratio: 4.2, 95% CI: 2.2-8.0, P < .001) and < or >or=1 mm Hg (hazard ratio: 3.5, 95% CI: 1.9-6.6, P < .001) being optimal for P(ET)CO(2) and DeltaP(ET)CO(2), respectively. Moreover, subjects with a P(ET)CO(2)>or=34 mm Hg had a significantly lower BNP (214.1 +/- 431.9 vs. 1110.5 +/- 1854.0 pg/mL, P=.005) and ANP (108.2 +/- 103.6 vs. 246.2 +/- 200.4 pg/mL, P < .001).

CONCLUSIONS

The results of this pilot study indicate ventilatory expired gas analysis during a short bout of low-intensity exercise may provide insight into prognosis and cardiac stability.

Cardiopulmonary exercise testing and its application

Cardiopulmonary exercise testing (CPET) has become an important clinical tool to evaluate exercise capacity and predict outcome in patients with heart failure and other cardiac conditions. It provides assessment of the integrative exercise responses involving the pulmonary, cardiovascular and skeletal muscle systems, which are not adequately reflected through the measurement of individual organ system function. CPET is being used increasingly in a wide spectrum of clinical applications for evaluation of undiagnosed exercise intolerance and for objective determination of functional capacity and impairment. This review focuses on the exercise physiology and physiological basis for functional exercise testing and discusses the methodology, indications, contraindications and interpretation of CPET in normal people and in patients with heart failure.

Understanding the basics of cardiopulmonary exercise testing

Cardiopulmonary exercise testing adds important additional information to that provided by the standard exercise test. In particular, cardiopulmonary exercise testing provides precise determination of aerobic capacity, the causes of dyspnea with exertion, and prognosis in patients with systolic heart failure. This review provides basic, practical information about cardiopulmonary exercise testing for the clinician.

Prospective comparison of ventilatory equivalent versus peak oxygen consumption in predicting outcomes of patients with heart failure

In patients with heart failure (HF), peak exercise oxygen consumption (VO2) is an important prognostic tool on which critical clinical decisions are made. However, recent retrospective data have suggested that ventilatory equivalent (VE = ventilation [liters per minute]/VO2 [liters per minute]) may be a stronger predictor of outcomes than VO2 in patients with HF on modern medical therapies. We prospectively collected baseline demographics, cardiovascular history, hemodynamics, and exercise ventilatory data from 221 consecutive patients with HF who underwent treadmill exercise VO2 testing. The composite primary end point was death or heart transplantation. Mean follow-up was 508 days, during which 27 events occurred (13 deaths and 14 transplantations). One-year event-free survival was 88% (n = 104 with 1-year follow-up). Mean age was 49 years, 68% were men, 84% were taking beta blockers, 82% were taking angiotensin-converting enzyme inhibitors, and 21% had an implantable cardioverter-defibrillator. Mean VO2 was 16 +/- 5 ml/kg/min. Mean VE was 47.4 +/- 15.2. Univariate predictors of events included lower VO2 (p <0.0001), higher heart rate at rest (p = 0.05), and presence of an implantable cardioverter-defibrillator (p = 0.024). Higher VE (p = 0.10) and lower maximum systolic blood pressure (p = 0.09) were of borderline significance. Age, gender, HF etiology or severity, and other ventilatory parameters were not significant predictors. Multivariate models that incorporated VE, VO2, or their combination confirmed VO2 as an independent predictor of event-free survival (p < or =0.0002); VE did not independently predict outcomes. Other independent predictors were higher heart rate at rest (p < or =0.02) and presence of an implantable cardioverter-defibrillator (p < or =0.04). In conclusion, peak VO2, but not VE, predicts clinical outcomes of patients with HF who are treated with contemporary medical therapies.

Cardiac Transplantation

Heart transplantation is a treatment option available to patients with end-stage heart failure who meet standardized selection criteria for transplant. Through a rigorous evaluation process, professionals set out to establish the patient's severity of heart failure, screen for comorbidities that may negatively affect survival, and assess psychosocial variables necessary for successful outcomes following transplantation. Because of a limited donor organ supply, each of these factors must be examined carefully to assure that this scarce resource is used to its greatest potential benefit.

Influence of etiology on ventilatory expired gas and prognosis in heart failure

BACKGROUND

Mechanisms leading to heart failure (HF) are numerous. Etiology-based differences are, however, frequently not taken into account when assessing results of an exercise test. The purpose of this investigation is to: (1) compare subject characteristics and ventilatory expired gas measures demonstrating clinical value between subjects with ischemic and non-ischemic HF. (2) Examine the prognostic value of HF etiology.

METHODS

71 subjects (44 male/27 female) diagnosed with compensated HF underwent exercise testing with ventilatory expired gas analysis. Mean age and ejection fraction (EF) were 51.3% (+/-12.8) and 27.0% (+/-12.5%) for the entire group. HF etiology was ischemic in 30 subjects (16 male/14 female) and non-ischemic in 41 (28 male/13 female).

RESULTS

Age (57.5+/-10.7 vs. 46.7+/-12.5, p<0.001), minute ventilation-carbon dioxide production (VE/VCO2) slope (39.5+/-9.1 vs. 32.6+/-7.7, p=0.001), and duration of phase 1 kinetics in seconds (46.0+/-23.0 vs. 30.0+/-15.6, p=0.001) were significantly higher while peak oxygen consumption (VO2) in ml O2 kg(-1) min(-1) (12.5+/-4.7 vs. 16.0+/-5.2, p=0.006) and partial pressure of end-tidal CO2 (P(ET)CO2) in mm Hg at rest (32.1+/-4.8 vs. 36.1+/-8.0, p=0.02) and peak exercise (31.7+/-4.3 vs. 36.2+/-5.9, p=0.001) were significantly lower in the ischemic group. Difference in EF did not reach statistical significance (28.4% +/-12.5%-ischemic vs. 26.1%+/-12.5%-non-ischemic, p=0.44). Ischemic etiology was additionally a significant predictor of cardiac-related events (p=0.04).

CONCLUSIONS

These findings demonstrate noninvasive indicators of cardiac function and prognosis is poorer in subjects with ischemic HF etiology. Consideration of HF etiology may therefore be prudent, particularly when considering prognosis.

Cardiopulmonary Exercise Testing and Prognosis in Chronic Heart Failure*

The identification of individuals who are at high risk of chronic heart failure (HF) is a medical art of growing concern. Cardiopulmonary exercise stress testing (CPX) has become an important clinical tool to predict outcome. The value of peak oxygen consumption rests in the fact that it integrates elements of cardiac adaptations, and skeletal muscle, pulmonary, and endothelial dysfunctions more than other traditional prognostic indicators of chronic HF. Recently, exercise-related ventilatory abnormalities have gained attention, stimulating scientific debate and an innovative perspective. This review, through a critical examination of previous experiences, will focus on the prognostic application of CPX, defining a proficient outline of treatment for the individual patient.

Peak VO2 and VE/VCO2 slope in patients with heart failure: a prognostic comparison

BACKGROUND

Exercise testing with ventilatory expired gas analysis has proven to be a valuable tool for assessing patients with heart failure (HF). Peak oxygen consumption (peak VO2) continues to be considered the gold standard for assessing prognosis in HF. The minute ventilation--carbon dioxide production relationship (VE/VCO2 slope) has recently demonstrated prognostic significance in patients with HF, and in some studies, it has outperformed peak VO2.

METHODS

Two hundred thirteen subjects, in whom HF was diagnosed, underwent exercise testing between April 1, 1993, and October 19, 2001. The ability of peak VO2 and VE/VCO2 slope to predict cardiac-related mortality and hospitalization was examined.

RESULTS

Peak VO2 and VE/VCO2 slope were demonstrated with univariate Cox regression analysis both to be significant predictors of cardiac-related mortality and hospitalization (P <.01). Multivariate analysis revealed that peak VO2 added additional value to the VE/VCO(2) slope in predicting cardiac-related hospitalization, but not cardiac mortality. The VE/VCO2 slope was demonstrated with receiver operating characteristic curve analysis to be significantly better than peak VO2 in predicting cardiac-related mortality (P <.05). Although area under the receiver operating characteristic curve for the VE/VCO2 slope was greater than peak VO2 in predicting cardiac-related hospitalization (0.77 vs 0.73), the difference was not statistically significant (P =.14).

CONCLUSIONS

These results add to the present body of knowledge supporting the use of cardiopulmonary exercise testing in HF. Consideration should be given to revising clinical guidelines to reflect the prognostic importance of the VE/VCO2 slope in addition to peak VO2.

Leptin and the ventilatory response to exercise in heart failure

OBJECTIVES

The aim of the study was to test the hypothesis that leptin is involved in the regulation of ventilatory responses to exercise in chronic heart failure (CHF).

BACKGROUND

Exercise-induced hyperventilation is a negative prognostic factor in CHF. Studies in animals suggest that leptin, a hormone secreted by adipocytes, contributes to the regulation of respiration. Plasma leptin levels are elevated in non-cachectic CHF, suggesting the possibility that leptin might be involved in dysregulation of ventilation in CHF.

METHODS

We studied 50 patients with stable CHF without cachexia. All subjects underwent anthropometric measurements, resting echocardiography, pulmonary function tests, and a cardiopulmonary exercise test. The ventilatory response to exercise was assessed by calculating the VE/VCO(2) and VE/VO(2) slopes (VE = ventilation per unit time, VCO(2) = carbon dioxide production, VO(2) = oxygen consumption).

RESULTS

Using a multiple regression model, leptin was significantly and positively correlated with both VE/VCO(2) slope (regression coefficient = 0.87, F = 39.32, p < 0.001) and VE/VO(2) slope (regression coefficient = 0.84, F = 24.04, p < 0.001). This correlation was independent of age, gender, body mass index, body fat, ejection fraction, New York Heart Association functional class, pulmonary function, plasma norepinephrine, angiotensin II, brain natriuretic peptide levels, and medications. Also, the greatest VE/VCO(2) slope was seen in subjects in the highest tertile of leptin.

CONCLUSIONS

Leptin is an independent predictor of VE/VCO(2) slope in heart failure, and may be a link between metabolic, cardiovascular, and respiratory abnormalities in CHF.

Technical considerations related to the minute ventilation/carbon dioxide output slope in patients with heart failure

BACKGROUND

The minute ventilation (VE)-carbon dioxide output (VCO(2)) relationship has recently been demonstrated to have prognostic significance in the heart failure (HF) population. However, the method by which the VE/VCO(2) slope is expressed has been inconsistent.

METHODS

One hundred eighty-eight subjects, who had received diagnoses of HF, underwent exercise testing. Two VE/VCO(2) slope calculations were made, one using exercise data prior to the ventilatory threshold (VT), and one using all data points from rest to peak exercise. Four separate peak exercise VE/VCO(2) slope calculations also were derived with unaveraged, 10-s, 30-s, and 60-s ventilatory expired gas sampling intervals.

RESULTS

Although univariate Cox regression analysis demonstrated pre-VT and peak VE/VCO(2) slope calculations to both be significant predictors of cardiac-related mortality and hospitalization (p < 0.001), the peak classification scheme was significantly better (p < 0.01). The ventilatory expired gas-sampling interval that was used did not impact the predictive ability of the peak VE/VCO(2) slope.

CONCLUSION

Although both the pre-VT and peak VE/VCO(2) slope calculations were prognostically significant, the peak expression was superior. The sampling interval did not appear to have a significant impact on prognostic utility. We hope that the results of the present study will contribute to the standardization of the VE/VCO(2) slope and will enhance its clinical application.

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

OBJECTIVES

We hypothesized that exercise-related periodic breathing (EPB) would be associated with poor prognosis in advanced chronic heart failure (CHF).

BACKGROUND

Patients with CHF might present instability of the ventilatory control system characterized by cyclic waxing and waning of tidal volume (periodic breathing [PB]). This condition is associated with several deleterious circulatory and neuro-endocrine responses; in fact, PB in awake and asleep patients has been identified as an independent risk factor for cardiac death. During exercise, however, the prognostic value of PB is still unknown in CHF patients awaiting heart transplantation.

METHODS

Eighty-four patients with established CHF (65 male, 19 female) were submitted to clinical evaluation, echocardiogram, ventricular scintigraphy, determination of resting serum norepinephrine levels, and an incremental cardiopulmonary exercise test on cycle ergometer. Patients were followed for up to 49.7 months (median = 15.3), and 26 patients (30.9%) died during this period.

RESULTS

Twenty-five of 84 patients presented EPB (29.7%). The following variables were related to mortality according to Kaplan-Meier and univariate Cox regression analysis: EPB (p = 0.004), New York Heart Association class (p = 0.04), serum norepinephrine (p = 0.06), peak oxygen uptake (ml.min(-1).kg(-1) and % predicted; p = 0.085 and p = 0.10, respectively), slope of the ratio of change in minute ventilation to change in carbon dioxide output during exercise (p = 0.10), and scintigraphic left ventricular ejection fraction (p = 0.10). Cox multivariate analysis identified EPB as the only independent variable for cardiac death prediction (p = 0.007). Therefore, EPB alone was associated with a 2.97-fold increase in risk of death in this population (95% confidence interval = 1.34 to 6.54).

CONCLUSIONS

Exercise-related periodic breathing independently predicts cardiac mortality in CHF patients considered for heart transplantation.

Impact of beta-blocker therapy on functional capacity criteria for heart transplant listing

BACKGROUND

Peak exercise oxygen consumption is a widely used parameter to determine the need for transplant listing in patients with severe heart failure. Currently, beta-blocker therapy is known to benefit patients with severe heart failure, although it has minimal or no effects on peak exercise oxygen consumption. This raises the hypothesis that peak exercise oxygen consumption transplant-listing criteria are not valid for patients with heart failure who receive beta-blocker therapy.

METHODS

We compared outcomes in patients with chronic heart failure who underwent heart transplant evaluation with peak exercise oxygen consumption </= 14.0 ml/kg/min and who were treated with beta-blockers (n = 48) or who were not treated with beta-blockers (n = 55).

RESULTS

Outcomes were significantly better for patients treated with beta-blockers (combined end-points of death, transplantation as United Network for Organ Sharing [UNOS] Status 1 or 2, and ventricular assist device placement, p = 0.0001). The 1-year survival was 92% and 3-year survival was 71% in the patients treated with beta-blockers, and 69% and 48% in the patients not treated with beta-blockers (compared with UNOS transplant survival data of 92% 1-year and 77% 3-year survival rates).

CONCLUSIONS

Patients with chronic heart failure and severe functional impairment who were treated with beta-blockers have significantly better outcomes compared with similarly functionally impaired patients who were not treated with beta-blockers, and these patients would not be expected to derive a survival benefit from transplantation. Thus, in patients treated with beta-blockers, the use of peak exercise oxygen consumption as a criterion to list for heart transplantation may no longer be valid. Alternatively, non-usage of beta-blockers may be a criterion to list for transplantation.

Cardiac transplantation as a treatment option for the heart failure patient

Cardiac transplantation is an effective therapy for a select group of heart failure patients. Timely referral of these patients is paramount to optimal patient care. After an extensive evaluation, suitable candidates are added to the national transplant waiting list and prioritized based on medical urgency. The waiting period then begins as these patients face a terminal illness with an unpredictable future.

The prognostic value of body mass index and standard exercise testing in male veterans with congestive heart failure

OBJECTIVE

To evaluate the prognostic characteristics of body mass index (BMI) and standard exercise test variables in a consecutive series of patients with mild to moderate congestive heart failure (CHF) referred for standard exercise tests.

BACKGROUND

Controversy exists regarding the prognostic importance of BMI, etiology, and exercise test variables in patients with CHF.

METHODS

All patients referred for evaluation at two university-affiliated Veterans Affairs Medical Centers who underwent treadmill tests for clinical indications between 1987 and 2000 were determined to be dead or alive using the Social Security Death Index after a mean 6 years follow-up. Clinical and exercise test variables were collected prospectively according to standard definitions; testing and data management were performed in a standardized fashion using a computer-assisted protocol. Survival analysis was performed using all-cause mortality as the endpoint for follow-up.

RESULTS

A total of 522 patients with a history and clinical findings of CHF underwent exercise testing. Forty-two percent died during the follow-up period, for an average annual mortality of 6.7%. Cox proportional hazards model chose peak metabolic equivalents (METs), BMI, age, and ischemic etiology in rank order as independently and significantly associated with time to death. A score based on these variables classified patients into low (2% annual mortality), medium (5.2%), and high-risk groups (7% annual mortality).

CONCLUSION

Standard exercise testing and BMI can be used to estimate prognosis in outpatients with heart failure. A score incorporating METs, BMI, age, and etiology efficiently stratified these patients. BMI was chosen by the survival analysis, confirming its surprising inverse relationship to prognosis in CHF patients (i.e., heavier patients do better).

Oscillatory ventilation during exercise in patients with chronic heart failure: clinical correlates and prognostic implications

STUDY OBJECTIVES

Although breathing disorders are often found in patients with chronic heart failure, exertional oscillatory ventilation (EOV) has been occasionally described. The aim of this study was to determine the prevalence, clinical characteristics, and outcome of patients with chronic heart failure and EOV.

SETTING

Cardiology division at tertiary-care hospital.

STUDY POPULATION

We studied 323 patients with chronic heart failure and left ventricular ejection fraction (LVEF) < or = 40%.

MEASUREMENTS AND RESULTS

All patients performed a symptom-limited cardiopulmonary exercise test and were followed up for 22 +/- 11 months (mean +/- SD). EOV was defined as cyclic fluctuations in minute ventilation (E) at rest that persist during effort lasting > or = 60% of the exercise duration, with an amplitude > or = 15% of the average resting value. Patients with EOV (12%), as compared to those without, showed higher New York Heart Association (NYHA) class (p < 0.05) and lower LVEF (p < 0.0001) and peak oxygen consumption (O(2)) [p < 0.0001]. During the follow-up period, 53 patients died or underwent urgent cardiac transplantation; this group showed higher NYHA class (p < 0.05) and E/CO(2) slope (p < 0.0001) and lower LVEF (p < 0.0001), mitral Doppler early deceleration time (p < 0.01), and peak O(2) (p < 0.0001). EOV was more frequent in nonsurvivors than in survivors (28% vs 9%, p < 0.01). Multivariate analysis revealed peak O(2) (chi(2), 51.5; p < 0.0001), EOV (chi(2), 45.4; p < 0.0001), and LVEF (chi(2), 20.6; p < 0.0001) as independent predictors of major cardiac events.

CONCLUSIONS

EOV is not unusual in patients with chronic heart failure, and is associated with worse clinical status, cardiac function, and exercise capacity. EOV is a powerful predictor of poor prognosis and, consequently, it may be considered a valuable guide in the management of patients with chronic heart failure and should suggest a more aggressive medical treatment policy when detected.

Ventilatory response to exercise improves risk stratification in patients with chronic heart failure and intermediate functional capacity

BACKGROUND

Peak oxygen consumption (VO2) has an important prognostic role in chronic heart failure (CHF), but its discriminatory power is limited in patients with intermediate exercise capacity (peak VO2 between 10-18 mL/kg/min). Thus, supplementary exertional indexes are greatly needed.

METHODS

Six hundred patients with CHF with left ventricular ejection fraction (LVEF) < or = 40% who performed a symptom-limited cardiopulmonary exercise testing were screened and followed up for 780 +/- 450 days.

RESULTS

Eighty-seven patients had major cardiac events (77 cardiac deaths and 10 urgent heart transplantations). Multivariate analysis revealed the rate of increase of minute ventilation per unit of increase of carbon dioxide production (VE/VCO2 slope) (chi2, 79.3, P <.0001), LVEF (chi2, 24.6, P <.0001), and peak VO2 (chi2, 9.4, P <.0001) as independent and additional predictors of major cardiac events. VE/VCO2 slope was the strongest independent predictor of outcome (chi2, 20.9, P =.0001) in patients with intermediate peak VO2 (n = 403), and the best cutoff value was 35 (chi2, 25.8; relative risk = 3.2, 95% CI 2.0-5.1, P <.0001). Total mortality rate was 30% in patients with VE/VCO2 slope > or = 35 (n = 103, 26%) and 10% in those with VE/VCO2 slope <35 (n = 300, 74%) (P <.0001). Patients with VE/VCO2 slope > or = 35 had a similar total mortality rate to those with peak VO2 < or = 10 mL/kg/min (30% vs 37%, P not significant).

CONCLUSIONS

A rational and pragmatic risk stratification process with symptom-limited cardiopulmonary exercise testing in CHF should include both peak VO2 and VE/VCO2 slope, the latter index effectively predicting outcome in almost one fourth of patients with intermediate exercise capacity.

Using exercise testing to prognosticate patients with heart failure. Which parameter should we measure?

Peak oxygen consumption, as measured by direct gas exchange analysis during exercise testing, is well established as a powerful and independent predictor of risk for death among patients with chronic, but stable, heart failure. Although there is still some debate about whether peak oxygen consumption should be indexed against a predicted value and what the best cut-off point may be, most authorities agree that peak oxygen consumption is such a powerful predictor of outcome that it routinely should be incorporated into the evaluation of all ambulatory heart transplant candidates. A few recent studies have demonstrated that a hyperventilatory response to exercise, as measured by the VE/VCO2 slope, also may be a powerful and independent predictor of death; however, more large studies, with large numbers of end-points, will be needed before this measure can deservedly take a place alongside peak oxygen consumption as a primary component of the heart failure staging process.

Exercise-related ventilatory abnormalities are more specific for functional impairment in chronic heart failure than reduction in peak exercise oxygen consumption

BACKGROUND

Impaired functional capacity during exercise is used to assess need for transplantation in congestive heart failure patients, although impaired capacity is present in several chronic illnesses. The purpose of this study was to test the hypothesis that ventilatory abnormalities during exercise, rather than functional capacity, are specific to congestive heart failure patients.

METHODS

We compared exercise-related gas exchange among a group of congestive heart failure patients and a group of patients who had chronic liver disease and normal cardiac function, matched for functional impairment, and a group of normal controls.

RESULTS

Patients with congestive heart failure and patients with chronic liver disease experienced marked reduction in peak exercise oxygen consumption compared with normal controls (14.0 +/- 1.4 and 14.2 +/- 3.7 ml/kg/min, respectively, vs 25.8 +/- 5.6 ml/kg/min, p < 0.01). Minute ventilation at peak exercise was significantly higher in congestive heart failure subjects than in chronic liver disease patients (59.3 +/- 16.8 liter/min vs 41.4 +/- 14.2 liter/min, p < 0.05), although carbon dioxide production was similar (1,380 +/- 308 ml vs 1,180 +/- 389 ml, p = not significant), so that the ratio of minute ventilation to carbon dioxide production (ventilatory equivalent for carbon dioxide, an index of ventilatory drive) was significantly elevated in congestive heart failure subjects (43 +/- 9 vs 36 +/- 7, p < 0.05).

CONCLUSIONS

Although functional impairment characterizes both congestive heart failure and chronic liver disease, only congestive heart failure patients exhibit exercise-related ventilatory abnormalities. Exercise-related ventilatory abnormalities may be more specific to the underlying pathophysiology of chronic heart failure and should be considered when evaluating patients for heart transplantation.

[Role of rehabilitation in the treatment of chronic heart insufficiency]

Rehabilitation is an important component of the modern comprehensive care plan for patients with chronic heart failure. Cardiac rehabilitation combines exercise training with therapeutical adaptations, behavioral modifications and psychosocial interventions. Based on these data, patients with controlled heart failure should be involved in cardiac rehabilitation programs. Training prescription needs a strict previous cardiac evaluation. Exercise training monitoring must be adjusted to the physical tolerance of each patient. Cardiac rehabilitation has been found to improve functional capacity, reduce symptoms, and finally reduce cardiac morbidity and mortality. These beneficial effects were associated with muscular, endothelial and ventilatory improvements. Reduced sympathetic tone may decrease arrhythmias and may limit the progression of left ventricular dysfunction.

Effect of angiotensin-converting enzyme inhibitor (enalapril or imidapril) on ventilation during exercise in patients with chronic heart failure secondary to idiopathic dilated cardiomyopathy

Eighteen patients with heart failure were studied to clarify whether angiotensin-converting enzyme inhibitor treatment improves excess ventilation during exercise. Treatment with angiotensin-converting enzyme inhibitors had a beneficial effect on excess ventilation during exercise, without significant improvement in exercise capacity in patients with moderate congestive heart failure.

Cardiopulmonary exercise parameters in relation to all-cause mortality in patients with chronic heart failure

In this study we analysed the all-cause mortality over a period of maximal 6 years in 60 male patients (age: 63.4+/-8.3 years, mean+/-S.D.), suffering from chronic heart failure with resting left ventricular ejection fraction and E/O2 slope as independent factors. We assessed functional NYHA class (II: n=36, III: n=24), radionuclide left ventricular ejection fraction (29.2+/-10.4%) and peak values of heart rate, O2, CO2, E, anaerobic threshold and exercise duration with an incremental work load test on the treadmill. O2 relative to E was based on the individual slopes of the regression of O2 on E during the first 6 min of exercise. These slopes with other exercise-related variables and factors such as etiology, medication, and NYHA class were analysed with a Cox's Regression Method. A survival time analysis (Kaplan-Meier survival curve) was done to establish the influence of E/O2 slope and left ventricular ejection fraction (both split into above and below median values), as well as their interaction, on survival. From all investigated exercise-related variables. E/O2 slope is the most powerful variable regarding prediction of all-cause mortality in our group of chronic heart failure patients. Concerning risk stratification, the subgroup (n=18) with a relatively high left ventricular ejection fraction (>28%) and flat E/O2 slope (<27.6) had most survivors (77.8%) after about 3 years, while the subgroup (n=12) with a relatively high left ventricular ejection fraction (>28%), but a steep E/O2 slope (>27.6) had least survivors (33.3%). This difference in percentage is highly significant (P=0.0025). The fact that E/O2 slope and left ventricular ejection fraction show comparable main and interaction effects between measures of exercise tolerance (e.g., anaerobic threshold, peak O2, exercise duration) on the one hand, and all-cause mortality on the other, suggests the existence of common sources of variance. Based on our analysis, it is unlikely that effects on all-cause mortality are mediated through phenomena related to exercise tolerance. Therefore, we hypothesize that the effects on exercise tolerance and all-cause mortality both depend on common factors, which cause both cardiac and peripheral organ (c.q. muscular) dysfunctions. Moreover, this study clearly shows that E/O2 slope during incremental exercise is an important prognostic marker for risk stratification in chronic heart failure patients, NYHA class II and III.

Maximal and submaximal exercise testing in heart failure

Although reduced exercise capacity is the main complaint of patients with congestive heart failure (CHF), the best method to measure it remains controversial. Peak VO2, obtained using maximal exercise testing, is the most accurate measure of maximal functional capacity. It is related to peak exercise cardiac output and is one of the most important independent variables for the prognostic assessment of patients with CHF. It has, however, a low sensitivity for measurement of changes induced by therapy and is poorly related to everyday physical activity, patient symptoms, and quality of life. The anerobic threshold may also be regarded as a parameter of maximal functional capacity. Its value is mainly indirect, because it shows that the patient is performing a maximal effort limited by the cardiovascular system. The VO2 kinetics at the start and at the end of exercise are probably more related to patient symptoms, but it is unresolved which protocols and parameters might best be used to study this aspect of exercise performance. Duration of a submaximal exercise at a constant work rate and the distance walked during a 6-min walking test are gaining wide popularity as parameters of submaximal performance. However, when these exams are carried out up to exhaustion in patients with severe functional limitation, they may involve attainment of the anerobic threshold and therefore their clinical meaning may be similar to the one of a maximal exercise test. Moreover, tests based on the assessment of submaximal exercise capacity have been useful for assessment of therapy in single-center trials but have been often inadequate in multicenter trials.