Impairment of ventilatory efficiency in heart failure: prognostic impact

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Usefulness of non-invasive measurement of cardiac output during sub-maximal exercise to predict outcome in patients with chronic heart failure

Peak oxygen consumption (Vo(2)) is a powerful prognostic predictor of survival in patients with chronic heart failure (CHF) because it provides an indirect assessment of a patient's ability to increase cardiac output (CO). However, many patients with CHF who undergo cardiopulmonary exercise testing are unable to perform maximal exercise. New metabolic carts coupled with the inert gas rebreathing technique provide a noninvasive measurement of CO. Whether the noninvasive measurement of CO at a fixed submaximal workload can predict outcome is unknown. This study's population comprised 259 patients (mean age 54 +/- 14 years, mean left ventricular ejection fraction 27 +/- 14%) with CHF who underwent symptom-limited incremental cardiopulmonary exercise testing. Vo(2) and CO were measured at rest, at 25 W, and at peak exercise. Submaximal exercise was defined as <80% peak Vo(2). Among 259 patients, 145 had Vo(2) at 25 W <80% of peak. Vo(2) at 25 W averaged 9.3 +/- 1.8 ml/kg/min. This Vo(2) represented 62 +/- 11% of peak Vo(2), which averaged 15.4 +/- 4.4 ml/kg/min. Prospective follow-up averaged 521 +/- 337 days. In this cohort, there were 15 outcome events (death, urgent heart transplantation, or implantation of a left ventricular assist device as a bridge to transplantation). On univariate Cox hazard analysis, CO at 25 W (hazard ratio 0.64, 95% confidence interval 0.48 to 0.84, p = 0.002) was found to be significant predictor of events of outcome. In conclusion, CO at 25 W measured noninvasively during submaximal exercise may have potential value as a predictor of outcomes in patients with CHF.

The effects of sildenafil and acetazolamide on breathing efficiency and ventilatory control during hypoxic exercise

The reduced arterial oxygen tension at high altitude impairs the ability to work. Acetazolamide improves arterial oxygen saturation (SaO(2)) by increasing ventilation but is associated with an increased work and cost of breathing. Depending on the settings, sildenafil can also increases SaO(2) possibly through a reduction in pulmonary hypertension and interstitial edema, which could improve ventilation-perfusion matching. The objective of this study is to determine the effects of acetazolamide and sildenafil on ventilatory control and breathing efficiency (V(E)/VCO(2)) during submaximal steady-state hypoxic exercise in healthy individuals. Following 18 h of hypoxic exposure in an altitude tent at an oxygen concentration of 12.5% (simulated altitude of 4,300 m), 15 participants performed 10 min of hypoxic exercise on a stationary bicycle at 40% of their sea level peak oxygen uptake (VO(2)) while randomly receiving sildenafil 40 mg (SIL), acetazolamide 125 mg (ACZ) or a placebo (PLA). There was no difference in VO(2) during exercise between conditions while SaO(2) was greater with acetazolamide compared to both placebo and sildenafil. Acetazolamide increased ventilation (PLA 49.0 +/- 3.2, SIL 47.7 +/- 3.1, ACZ 52.1 +/- 3.0 l/min) and reduced end-tidal CO(2) (P(ET)CO(2)) (PLA 32.1 +/- 0.8, SIL 32.8 +/- 0.9, ACZ 29.2 +/- 0.7 mmHg) compared to placebo and sildenafil. Breathing was less efficient with acetazolamide (increased V(E)/VCO(2)) in comparison to placebo and sildenafil (PLA 41.5 +/- 1.0, SIL 40.4 +/- 1.3, ACZ 45.4 +/- 1.0) while sildenafil did not change V(E)/VCO(2) during hypoxic exercise. In conclusion, acetazolamide increased ventilation and reduced breathing efficiency while sildenafil did not affect breathing efficiency despite a trend toward a blunted ventilatory response, possibly due to a reduction in pulmonary hypertension and/or ventilatory drive, during submaximal hypoxic exercise in healthy individuals.

Effect of biventricular pacing on ventilatory and perceptual responses to exercise in patients with stable chronic heart failure

Despite the growing evidence supporting the use of biventricular cardiac resynchronization therapy (CRT) in patients with chronic heart failure (CHF), the mechanisms whereby acute hemodynamic improvements lead to improved exertional dyspnea are not precisely known. We hypothesized that improved cardiac function and ventilation-perfusion relations following CRT would reduce ventilatory demand, thereby improving dynamic operating lung volumes and enhancing tidal volume expansion during exercise. This, in turn, would be expected to reduce perceived exertional dyspnea and contribute to improved exercise performance. In a randomized, double-blind, crossover study, we compared cardiovascular, metabolic, ventilatory responses (breathing pattern, operating lung volumes, pulmonary gas exchange) and exertional symptoms in seven stable CHF patients who undertook incremental cardiopulmonary cycle exercise test with CRT switched to the “on” (CRTon) or “off” (CRToff) modality. Following CRTon, peak oxygen uptake was significantly increased by 15%, and dyspnea ratings were lower for a given work rate (at work rate of 40 W, dyspnea = 1 ± 0.4 vs. 2.5 ± 0.9 Borg units, P < 0.05) and ventilation (at ventilation of 31 l/min, dyspnea = 2 ± 0.7 vs. 3.3 ± 1.1 Borg units, P < 0.05). CRTon was associated with improvements in ventilatory threshold, oxygen pulse, and oxygen uptake/work rate relationships (10.2 ± 1 vs. 7.9 ± 1.3 ml·min−1·W−1, P < 0.05). CRTon reduced the ventilatory requirement during exercise as well as the steepness of ventilation-CO2 production slope (35 ± 4 vs. 45 ± 7, P < 0.05). Changes in end-expiratory lung volume during exercise were less with CRTon than with CRToff (0.12 vs. 0.37 liter, P < 0.05), and breathing pattern was correspondingly slower and deeper. Biventricular pacing improved all noninvasive indexes of cardiac function and oxygen delivery during exercise. The decreased ventilatory demand, improved dynamic operating lung volumes, and the increased ability to expand tidal volume during exercise are potential factors in the reduction of exertional dyspnea.

Altered ventilatory responses to exercise testing in young adult men with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is a disorder characterized by repetitive obstructions of the upper airway. Individuals with OSA experience intermittent hypoxia, hypercapnia, and arousals during sleep, resulting in increased sympathetic activation. Chemoreflex activation, arising from the resultant oscillatory disturbances in blood gases from OSA, exerts control over ventilation, and may induce increases in sympathetic vasoconstriction, contributing to increased long-term risks for hypertension (HTN) and cardiovascular disease (CVD).

METHODS

To evaluate whether OSA elicits exaggerated ventilatory responses to exercise in young men, 14 overweight men with OSA and 16 overweight men without OSA performed maximal ramping cycle ergometer exercise tests. Oxygen consumption (VO(2)), ventilation, (V(E)), ventilatory equivalents for oxygen (V(E)/VO(2)) and carbon dioxide (V(E)/VCO(2)), and V(E)/VCO(2) slope were measured.

RESULTS

The VO(2) response to exercise did not differ between groups. The V(E), V(E)/VCO(2), V(E)/VO(2) were higher (p< 0.05, 0.002, and p<0.02, respectively) in the OSA group across all workloads. The V(E)/VCO(2) slope was greater in the OSA group (p<0.05). The V(E)/VCO(2) slope and AHI were significantly correlated (r=0.56, p<0.03). Thus, young, overweight men with OSA exhibit increased ventilatory responses to exercise when compared to overweight controls. This may reflect alterations in chemoreflex sensitivity, and contribute to increased sympathetic drive and HTN risk.

Myotoxic reactions to lipid-lowering therapy are associated with altered oxidation of fatty acids

Despite exceptional efficacy and safety, fear of muscle toxicity remains a major reason statins are underutilized. Evidence suggests that statin muscle toxicity may be mediated by abnormalities in lipid metabolism. To test the hypothesis that myotubes from patients intolerant of lipid-lowering therapies have abnormal fatty acid oxidation (FAO) responses we compared muscle from 11 subjects with statin intolerance (Intolerant) with muscle from seven statin-naive volunteers undergoing knee arthroplasty (Comparator). Gross muscle pathology was graded and skeletal muscle cell cultures were produced from each subject. FAO was assessed following treatment with increasing statin concentrations. There was no difference in muscle biopsy myopathy scores between the groups. Basal octanoate oxidation was greater in Intolerant than in Comparator subjects (P = 0.03). Lovastatin-stimulated palmitate oxidation tended to be greater for Intolerant compared to Control subjects' myotubes (P = 0.07 for 5 microM and P = 0.06 for 20 microM lovastatin). In conclusion abnormalities in FAO of Intolerant subjects appear to be an intrinsic characteristic of these subjects that can be measured in their cultured myotubes.

Prognostic value of brain natriuretic peptide and enhanced ventilatory response to exercise in patients with chronic heart failure

Whether brain natriuretic peptide (BNP), combined with a cardiopulmonary exercise test (CPx) parameters or echocardiography improves prognostic stratification in mild-to-moderate systolic heart failure (HF) is currently unclear. In 156 consecutive stable outpatients with mild to moderate HF and left ventricular ejection fraction (LVEF) <40%, we assessed the impact of BNP assay, Doppler echocardiography and CPx on survival. Median BNP plasma levels were 207 [90-520] pg/mL. Mean LVEF was 33 +/- 7%. Left bundle branch block (LBBB) was present in 52 patients (33%) and a restrictive filling pattern in 35 (22%). The slope of the relation between minute ventilation and carbon dioxide production (VE/VCO(2) slope) averaged 35 +/- 8; an enhanced ventilatory response (EVR) to exercise (VE/VCO(2) slope >35) was found in 67 patients (43%). During 759 +/- 346 days of follow-up, 24 patients died. By multivariate analysis, the strongest independent predictors of all-cause death among clinical, echocardiographic variables and BNP were LBBB and beta-blocker treatment. When CPx variables were added, the best predictors of mortality were LBBB, beta-blockade and VE/VCO(2) slope. This study highlights the value of a sequential approach, based on clinical, laboratory and functional data to identify high-risk HF patients. BNP assay might constitute a simple alternative tool for patients with an inability or with clinical contraindications to exercise, advanced physical deconditioning and unreliable CPx results. However, whenever feasible, CPx with assessment of EVR is recommended for a more accurate prediction of prognosis.

A cardiopulmonary exercise testing score for predicting outcomes in patients with heart failure

OBJECTIVE

The aim of this study is to evaluate the predictive accuracy of a cardiopulmonary exercise test (CPX) score.

BACKGROUND

Cardiopulmonary exercise test responses, including peak VO(2), markers of ventilatory inefficiency (eg, the VE/VCO(2) slope and oxygen uptake efficiency slope [OUES]), and hemodynamic responses, such as heart rate recovery (HRR) and chronotropic incompetence (CRI) are strong predictors of outcomes in patients with heart failure (HF). However, there is a need for simplified approaches that integrate the additive prognostic information from CPX.

METHODS

At 4 institutions, 710 patients with HF (568 male/142 female, mean age 56 +/- 13 years, resting left ventricular ejection fraction 33 +/- 14%) underwent CPX and were followed for cardiac-related mortality and separately for major cardiac events (death, hospitalization for HF, transplantation, left ventricular assist device implantation) for a mean of 29 +/- 25 months. The age-adjusted prognostic power of peak VO(2), VE/VCO(2) slope, OUES (VO(2) = a log(10)VE + b), resting end-tidal carbon dioxide pressure (PetCO(2)), HRR, and CRI were determined using Cox proportional hazards analysis, optimal cutpoints were determined, the variables were weighted, and a multivariate score was derived.

RESULTS

There were 175 composite outcomes. The VE/VCO(2) slope (> or =34) was the strongest predictor of risk and was attributed a relative weight of 7, with weighted scores for abnormal HRR (< or =6 beats at 1 minute), OUES (>1.4), PetCO(2) (<33 mm Hg), and peak VO(2) (< or =14 mL kg(-1) min(-1)) having scores of 5, 3, 3, and 2, respectively. Chronotropic incompetence was not a significant predictor and was excluded from the score. A summed score >15 was associated with an annual mortality rate of 27% and a relative risk of 7.6, whereas a score <5 was associated with a mortality rate of 0.4%. The composite score was the most accurate predictor of cardiovascular events among all CPX responses considered (concordance indexes 0.77 for mortality and 0.75 for composite outcome composed of mortality, transplantation, left ventricular assist device implantation, and HF-related hospitalization). The summed score remained significantly associated with increased risk after adjusting for age, gender, body mass index, ejection fraction, and cardiomyopathy type.

CONCLUSION

A multivariable score based on readily available CPX responses provides a simple and integrated method that powerfully predicts outcomes in patients with HF.

Right heart dysfunction assessed with echography, B-type natriuretic peptide and cardiopulmonary test in patients with chronic heart failure

BACKGROUND

Right ventricle (RV) impairment could influence brain natriuretic peptide (BNP) circulating levels. It is not well known whether echocardiographic parameters assessing RV function could be related to BNP levels in patients with chronic heart failure (CHF). Controversial data are available about the role played by RV dysfunction in determining exercise capacity in CHF patients.

METHODS

Sixty patients with CHF referred to our CHF Unit underwent blood sampling for BNP levels determination, cardiopulmonary exercise test with VO2 peak, VO2-AT and VE/VCO2 slope assessment and M-mode, two-dimensional and Doppler echocardiography with evaluation of right heart function [right atrial pressure (RAP), pulmonary artery pressure (PAP), severity of tricuspid regurgitation (TR), and tricuspid annular plane systolic excursion (TAPSE)].

RESULTS

A significant correlation was detectable between BNP levels and TAPSE (r = -0.33; P < 0.05), RAP (r = 0.34; P < 0.05), PAP (r = 0.42; P < 0.05), TR (P for trend 0.05); correlation with TAPSE remained significant even in multivariate. VO2 peak was significantly related to RAP (r = -0.38, P < 0.05) and TR (P for trend 0.05); AT with PAP (r = -0.40, P < 0.05), RAP (r = -0.50, P < 0.05), TR (P for trend 0.05). Moreover, patients with TAPSE greater than 16 mm had higher values of VO2 peak (13.68 +/- 3.28 vs. 11.49 +/- 2.37 ml/kg/m', P < 0.05) and of VO2-AT (18.36 +/- 1.60 vs. 10.23 +/- 2.31 ml/kg/m'; P < 0.05).

CONCLUSION

Right heart dysfunction assessed by simple echocardiographic parameters is related to neurohormonal activation featured by increased BNP levels and to a worse functional capacity in CHF patients.

Prognostic usefulness of dyspnea versus fatigue as reason for exercise test termination in patients with heart failure

Cardiopulmonary exercise testing (CPX) is an integral tool for assessing the clinical status and prognosis of patients with heart failure (HF). The present investigation examined differences in CPX variables and prognosis according to reason for test termination. One hundred eighty-three patients with HF (69% men, 31% women; mean age 53 +/- 13 years, left ventricular ejection fraction at rest 24.3 +/- 9.9%) underwent CPX in which the minute ventilation/carbon dioxide production slope, peak oxygen consumption, and peak respiratory exchange ratio were determined. Subjects were tracked for cardiac-related events for 2 years after CPX. Dyspnea and fatigue (general fatigue/leg fatigue) were the primary reasons for test termination in 79 and 104 patients, respectively. Peak oxygen consumption (15.4 +/- 5.7 vs 17.5 +/- 5.9 ml o(2) . kg(-1) . min(-1)) was significantly lower, whereas minute ventilation/carbon dioxide production slope (38.5 +/- 12.8 vs 33.9 +/- 9.8) was significantly higher in the dyspnea subgroup (p <0.05). There were 41 cardiac-related events during the 2-year tracking period. Patients with dyspnea were at significantly higher risk of adverse events (hazard ratio 2.1, 95% confidence interval 1.1 to 4.0, p = 0.02). In conclusion, these results indicate that patients with HF terminating an exercise test primarily because of dyspnea have an increased incidence of cardiac-related events and poorer CPX markers than those limited by fatigue.

Ventilatory efficiency and resting hemodynamics in hypertrophic cardiomyopathy

PURPOSE

In patients with systolic heart failure, the ability of cardiopulmonary exercise testing (CPX) variables to reflect pathophysiology is well established. The relationship between CPX and pathophysiology has, however, not been thoroughly investigated in patients with nonobstructive hypertrophic cardiomyopathy (NHCM). The objective of this study was to assess the ability of CPX variables to reflect resting hemodynamics in patients with nonobstructive hypertrophic cardiomyopathy NHCM.

METHODS

We performed CPX and right heart catheterization on 83 subjects with NHCM (51 male/32 female, mean age = 38 +/- 10 yr, NYHA I-III mean = 1.7). Peak oxygen consumption ( O2) and minute ventilation/carbon dioxide ratio (V E/VCO2) at peak exercise were compared to resting hemodynamics including pulmonary artery systolic, diastolic and mean pressures (PASP, PADP and MPAP), and pulmonary capillary wedge pressure (PCWP).

RESULTS

Elevations in PCWP (> or = 15 mm Hg), PASP (> or =30 and > or = 40 mm Hg), PADP (> 15 mm Hg) and MPAP (> or = 20 mm Hg) were detected in 22, 33, 10, and 23% of subjects, respectively. Peak V E/VCO2 (positive correlation) and peak VO2 (negative correlation) correlated modestly with all pressure measurements (r = 0.33-0.51, P < 0.01 for all measurements). By receiver operating curve analysis, a V E/VCO2 >35.5 exhibited the best diagnostic accuracy with a curve areas of 0.81 for PAP > or = 30 mm Hg (sensitivity/specificity = 86%/67%), 0.87 for PAP > or = 40 mm Hg (77%/100%), 0.86 for MPAP > 20 mm Hg (83%/79%), and 0.84 for PCWP > or = 15 mm Hg (80%/76%).

CONCLUSIONS

CPX can accurately identify abnormal resting hemodynamics in patients with NHCM. Further testing of this modality in other forms of diastolic dysfunction may be warranted.

The prognostic value of the heart rate response during exercise and recovery in patients with heart failure: influence of beta-blockade

BACKGROUND

The heart rate increase during exercise (DeltaHR) and heart rate recovery (HRR) have demonstrated prognostic value in several investigations, but its application in the heart failure (HF) population is limited, particularly in a beta-blocked (BB) cohort.

METHODS

Five-hundred and twenty subjects with HF underwent cardiopulmonary exercise testing to determine peak oxygen consumption (VO(2)), the minute ventilation/carbon dioxide production (VE/VCO(2)) slope, DeltaHR and HRR at 1 min (HRR(1)).

RESULTS

There were 79 cardiac-related deaths during the tracking period. A HRR(1) threshold of </>or=16 beats/min was a significant prognostic marker in the overall group (hazard ratio: 4.6, 95% CI: 2.8-7.5, p<0.001) as well as no-BB (hazard ratio: 9.1, 95% CI: 4.1-20.2, p<0.001) and BB (hazard ratio: 2.9, 95% CI: 1.6-5.4, p<0.001) subgroups. The DeltaHR was a significant univariate predictor in the overall group and no-BB subgroup only. Multivariate Cox regression analysis revealed HRR(1) was the strongest prognostic marker (chi-square: 39.9, p<0.001). The VE/VCO(2) slope (residual chi-square: 21.8, p<0.001) and LVEF (residual chi-square: 9.6, p=0.002) were also retained in the regression.

CONCLUSIONS

These results indicate that HRR maintains prognostic value in HF irrespective of BB use. The routine inclusion of HRR in the prognostic assessment of patients with HF may be warranted.

Impact of pulmonary hypertension on gas exchange and exercise capacity in patients with pulmonary fibrosis

Pulmonary hypertension is a relevant interceding morbidity in patients with pulmonary fibrosis that has significant impact on exercise tolerance and outcome. The aim of this study was to further characterize the exercise intolerance, dyspnoea and ventilatory inefficiency of patients with pulmonary fibrosis in the presence or absence of pulmonary hypertension via cardiopulmonary exercise testing. Thirty-four patients underwent pulmonary function testing, symptom-limited exercise testing on a bicycle and dyspnoea evaluation according to the BORG scale. Pulmonary hypertension was assessed by echocardiography and in a subset of patient's right heart catheterization. Sixteen of 34 patients with pulmonary fibrosis revealed pulmonary hypertension. While all study patients did not differ in lung functions and demographic characteristics, patients suffering from pulmonary hypertension showed a significantly impaired exercise tolerance and worsened ventilatory inefficiency. The extent of pulmonary artery pressure elevation impacted significantly on ventilatory inefficiency. In addition, the increased ventilatory requirements significantly influenced the extent of dyspnoea in patients with pulmonary hypertension. We conclude that pulmonary hypertension has a significant impact on exercise capacity and dyspnoea in patients with interstitial lung disease (ILD). The further impairment of exercise capacity as well as the extent of dyspnoea in patients with interceding PHT is attributable to a significantly impaired ventilatory inefficiency.

The initial slope of the VCO2/VO2-curve (s1) in cardiopulmonary exercise testing is a strong and independent predictor of outcome in patients with previous myocardial infarction

BACKGROUND

Detecting heart failure (HF) patients at risk is a relevant clinical problem. Our goal was to define associations of clinical HF-markers and exercise parameters with respect to their prognostic power in HF-patients.

METHODS

We performed cardiopulmonary exercise testing (CPET) in 103 ischemic HF-patients. CPET-parameters included peak VO(2), VO(2) at AT, peak oxygen pulse, minimal CO(2) and O(2) equivalents, VE/VCO(2) and s1, a motivation-independent and submaximal parameter representing the initial slope of the VCO(2)/VO(2)-curve that has not been described in HF-patients so far.

RESULTS

Median follow-up was 668 days. The combined endpoint of cardiovascular death and rehospitalization due to HF occurred in 14 patients. Patients with/without events differed significantly regarding their age, NYHA-class, LVEF and NT-proBNP serum-levels. Patients with events had significantly lower peak VO(2)- and higher s1-values. NT-proBNP serum-levels, NYHA-class and LVEF were significantly correlated with peak VO(2). Only age, peak VO(2) and s1 were independent predictors of adverse events. Using multivariate analysis, s1 was a strong and independent parameter with good sensitivity and specificity.

CONCLUSION

s1 is an independent and powerful predictor in HF-patients. Since s1 is independent of maximal exercise capacity, s1 might be more accurate for the evaluation of HF-patients not willing or unable to perform maximal exercise.

Reproducibility of the self-controlled six-minute walking test in heart failure patients

INTRODUCTION

The six-minute walk test (6WT) has been proposed to be a submaximal test, but could actually demand a high level of exercise intensity from the patient, expressed by a respiratory quotient >1.0, following the guideline recommendations. Standardizing the 6WT using the Borg scale was proposed to make sure that all patients undergo a submaximal walking test.

PURPOSE

To test the reproducibility of the six-minute treadmill cardiopulmonary walk test (6CWT) using the Borg scale and to make sure that all patients undergo a submaximal test.

METHODS

Twenty-three male heart failure patients (50+/-9 years) were included; these patients had both ischemic (5) and non-ischemic (18) heart failure with a left ventricle ejection fraction of 23+/-7%, were diagnosed as functional class NYHA II-III and were undergoing optimized drug therapy. Patients were guided to walk at a pace between "relatively easy and slightly tiring" (11 and 13 on Borg scale). The 6CWT using the Borg scale was performed two times on a treadmill with zero inclination and patient control of speed with an interval of 24 hours. During the sixth minute, we analyzed ventilation (VE, L/min), respiratory quotient, Oxygen consumption (VO2, ml/kg/min), VE/VCO2 slope, heart rate (HR, bpm), systolic blood pressure (SBP, mmHg), diastolic (DBP, mmHg) blood pressure and distance.

RESULTS

The intraclass correlation coefficients at the sixth minute were: HR (r i=0.96, p<0.0001), VE (r i=0.84, p<0.0001), SBP (r i=0.72, p=0.001), distance (r i=0.88, p<0.0001), VO2 (r i=0.92, p<0.0001), SlopeVE/VCO2 (r i=0.86, p<0.0001) and RQ<1 (r i=0.6, p=0.004).

CONCLUSION

Using the 6CWT with the Borg scale was reproducible, and it seems to be an appropriate method to evaluate the functional capacity of heart failure patients while making sure that they undergo a submaximal walking test.

Mechanical right ventricular dyssynchrony in patients after atrial switch operation for transposition of the great arteries

Recent data suggest potential benefits of cardiac resynchronization therapy in the management of right ventricular (RV) dysfunction in congenital heart disease. The aim of this study was to determine the nature, prevalence, and functional implications of mechanical RV dyssynchrony in patients after Senning or Mustard procedures for transposition of the great arteries. Twenty-eight patients (mean age 21.1 +/- 3.5 years) at 19.9 +/- 3.2 years after atrial switch operations and 29 healthy controls were studied. The times from the onset of QRS to peak systolic strain (T epsilon) at the base of and the mid RV free wall, the ventricular septum (VS), and the left ventricular (LV) free wall were determined using tissue Doppler echocardiography. Intraventricular mechanical delay was defined as Delta T epsilon(RV-VS) and interventricular mechanical delay as Delta T epsilon(RV-LV). In patients, the magnitude of RV intra- and interventricular mechanical delay was correlated with cardiac magnetic resonance-derived RV volumes and ejection fractions (n = 26) and treadmill exercise testing parameters (n = 20). Compared with controls, patients had significantly longer Delta T epsilon(RV-VS) (48.1 +/- 50.9 vs 17.0 +/- 16.1 ms, p <0.001) and Delta T epsilon(RV-LV) (63.1 +/- 49.5 vs 19.0 +/- 12.9, p <0.001). Nine patients (32%) exhibited RV dyssynchrony (Delta T epsilon(RV-VS) >49 ms, control mean +/- 2SD), and 16 patients (57%) showed interventricular dyssynchrony (Delta T epsilon(RV-LV) >45 ms). In patients, RV intra- and interventricular mechanical delay was correlated negatively with the RV ejection fraction (both r = -0.42, p = 0.03) and percentage predicted maximum oxygen consumption (r = -0.50, p = 0.03, and r = -0.52, p = 0.02, respectively) and positively with minute ventilation/carbon dioxide production slope (r = 0.49, p = 0.03, and r = 0.56, p = 0.01, respectively). In conclusion, RV dyssynchrony is common in young adults after atrial switch operations and is associated with RV systolic dysfunction and impaired exercise performance.

Influence of the incremental step size in work rate on exercise response and gas exchange in patients with pulmonary hypertension

Background

Cardiopulmonary exercise testing (CPET) has become increasingly important as a routine procedure in daily clinical work. So far, it is generally accepted that an individualized exercise protocol with exercise duration of 6 to 12 minutes is preferable to assess maximal exercise performance. The aim of this study was to compare an individualized NYHA adapted exercise protocol with a fixed standard protocol in patients with severe pulmonary arterial hypertension.

Methods

Twenty-two patients (17 female, 5 male; mean age 49 ± 14 yrs) underwent symptom limited CPET on a bicycle. On two consecutive days each subject performed a stepwise CPET according to a modified Jones protocol (16 Watt per minute stages) as well as an individualized NYHA adapted protocol with 5 or 10 Watt/min stages in a randomized order. Oxygen uptake at peak exercise (peakVO₂) and anaerobic threshold (VO₂AT), maximal ventilation (VE), breathing reserve (VE/MVV), ventilatory efficiency (VE vs. VCO₂ slope), exercise time, maximal power and work rate were assessed and compared between both protocols.

Results

Comparing both, adapted NYHA protocol and standardized Jones protocol, we found significant differences in maximal power (56.7 ± 19 W vs. 74 ± 18 W; p < 0.001) and exercise time (332 ± 107 sec. vs. 248 ± 72 sec.; p < 0.001). In contrast, no significant differences were obvious comparing both protocols concerning work rate, VE, VE/MVV, peakVO₂, VO₂AT and VE vs. VCO₂ slope.

Conclusion

Variations of incremental step size during CPET significantly affect exercise time and maximal power, whereas relevant parameters for clinical judgement and prognosis such as oxygen uptake, ventilation and ventilatory efficiency remain unchanged. These findings have practical implications for the exercise evaluation of patients with pulmonary hypertension. To reach maximal results for ventilation, oxygen uptake and gas exchange an individualization of incremental step size appears not to be mandatory.

Relation of the prognostic value of ventilatory efficiency to body mass index in patients with heart failure

The ventilatory efficiency, minute ventilation (VE)/carbon dioxide production (VCO2), slope consistently provides valuable prognostic information in patients with heart failure (HF). Patients with a higher body mass index (BMI) have demonstrated an improved prognosis in the HF population, a phenomenon that has been termed the "obesity paradox." The purpose of this study was to evaluate the prognostic ability of the VE/VCO2 slope according to BMI in patients with HF. Seven-hundred four patients with HF (555 men, 149 women, mean age 56.8+/-13.4 years, ejection fraction 33.1+/-13.3%) with a BMI>or=18.5 kg/m2 underwent cardiopulmonary exercise testing. Subjects were divided into 3 BMI subgroups (18.5 to 24.9, 25.0 to 29.9, and >or=30 kg/m2). Each subject was tracked for major cardiac events (death, transplantation, left ventricular assist device implantation) for 2 years after testing. There were 86 major cardiac events (71 deaths, 10 transplantations, 5 left ventricular assist device implantations) during the 2-year tracking period (overall annual event rate 8.2%). The VE/VCO2 slope was the strongest prognostic marker in each BMI subgroup. Subjects in the highest BMI group had the lowest mean VE/VCO2 slope and the lowest rate of major cardiac events of the 3 groups. Multivariate Cox regression analysis showed that peak VO2 did not add additional prognostic value to the VE/VCO2 slope and was removed from the regression for each BMI subgroup. In conclusion, the findings of the present study indicate that VE/VCO2 slope maintains prognostic value irrespective of BMI in patients with HF.

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.

Excessive ventilation during early phase of exercise: A new predictor of poor long-term outcome in patients with chronic heart failure

BACKGROUND

Studies demonstrating prognostic value of excessive exercise ventilation in chronic heart failure (CHF) have focused on data derived from the whole cardiopulmonary exercise test (CPET). Whether ventilatory response to early phase of exercise is useful for risk stratification in CHF is unknown.

METHODS AND RESULTS

We evaluated 216 patients with systolic CHF who underwent CPET (age: 60+/-11 years, NYHA class [I/II/III/IV]: 18/104/77/17). Ventilatory response to exercise (slope of regression line relating ventilation to carbon dioxide production) was calculated from the whole exercise test (VE-VCO(2)-all) and from the first 3 min of exercise (early phase - VE-VCO(2)-3 min). During follow-up (mean: 40+/-20 months, >3 years in survivors), 89 (41%) CHF patients died. High VE-VCO(2)-all and VE-VCO(2)-3 min predicted poor outcome in single predictor analyses, and in multivariable models when adjusted for prognosticators (age, NYHA class, ejection fraction, peak VO(2)) (P<0.0001). In receiver operating characteristic curve analysis, areas under curve for 3-year follow-up were similar for VE-VCO(2)-all and VE-VCO(2)-3 min. VE-VCO(2)-3 min maintained its prognostic value in patients taking beta-blockers (P<0.0001) and those unable to perform maximal CPET (P=0.0009).

CONCLUSIONS

In CHF patients, excessive ventilation assessed over the first 3 min predicts poor outcome. Assessment of ventilatory response to exercise for prognostic stratification may be extended to patients unable to perform maximal CPET.

Effect of insulin sensitivity on severity of heart failure

Insulin resistance is associated with various cardiac dysfunctions both molecularly and clinically, including cardiac muscle relaxation and blood flow. Although, these dysfunctions result in heart failure, relationship between insulin resistance and severity of heart failure is not well studied yet. Since severity of chronic heart failure can be determined by exercise tolerance, we attempted to assess the insulin resistance in patients with chronic heart failure and evaluated the relationship between insulin sensitivity and exercise tolerance. We examined nine chronic heart failure patients. Insulin sensitivity was determined with euglycemic hyperinsulinemic clamp technique. Exercise tolerance was assessed using cardiopulmonary exercise testing. There was no correlation between body mass index and insulin sensitivity, while between body fat ratio, significant negative correlation was investigated (r=-0.463). Insulin sensitivity was negatively correlated with exercise tolerance (with anaerobic threshold, r=0.548; with peak oxygen uptake, r=0.581). Insulin sensitivity also showed significant positive correlation with cardiac function during exercise (GIR versus peak oxygen pulse: r=0.535). Insulin sensitivity is revealed to have some effects on exercise tolerance and cardiac function in patients with chronic heart failure. Insulin resistance seems to be one of the important targets in managing the chronic heart failure.

Alveolar-capillary membrane conductance is the best pulmonary function correlate of exercise ventilation efficiency in heart failure patients

BACKGROUND

In heart failure (HF), changes in lung mechanics and gas diffusion are limiting factors to exercise. Their contribution to an increased exercise ventilation to CO2 production (VE/VCO2) slope is undefined.

METHODS

A total of 67 stable HF patients underwent cardiopulmonary exercise and pulmonary function tests, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), maximal voluntary ventilation (MVV), total lung capacity (TLC) and alveolar diffusing capacity with its subcomponents (alveolar-capillary membrane conductance (D(m)) and capillary blood volume (V(c))).

RESULTS

Patients showed a mild restrictive pattern (FEV1=85+/-15% and FVC=75+/-13% of normal predicted) and a moderate D(m) reduction (32+/-12 ml min(-1) mm Hg(-1)). Average peak VO(2) was 15.6+/-4.0 ml min(-1) kg(-1) and the VE/VCO2 slope was 39.6+/-11.0. At simple Spearman correlation analysis, all variables, but V(c), correlated with peak VO2; only D(m) correlated with VE/VCO2 slope. At partial Spearman correlation, all variables lost the peak VO2 correlation, and D(m) still inversely correlated with VE/VCO2 slope (r=-0.35; p=0.005). In patients with a high VE/VCO2 slope (cutoff value 34), despite comparable lung volumes, D(m) was significantly more depressed (30+/-13 vs. 35+/-10 ml min(-1) mm Hg(-1); p<0.01).

CONCLUSIONS

Pulmonary function tests and alveolar gas diffusing capacity poorly correlate with peak VO2. D(m) impairment rather than lung volumes correlates with exercise ventilation efficiency. This finding further adds to the pathophysiological relevance of an abnormal gas exchange in HF patients.

Exercise oscillatory ventilation may predict sudden cardiac death in heart failure patients

OBJECTIVES

The purpose of this study was to test the ability of cardiopulmonary exercise testing (CPET)-derived variables as sudden cardiac death (SCD) predictors.

BACKGROUND

The CPET variables, such as peak oxygen uptake (VO2), ventilatory requirement to carbon dioxide (CO2) production (VE/VCO2) slope, and exercise oscillatory breathing (EOB), are strong predictors of overall mortality in chronic heart failure (CHF) patients. Even though up to 50% of CHF patients die from SCD, it is unknown whether any of these variables predicts SCD.

METHODS

One hundred fifty-six CHF patients (mean age: 60.9 +/- 9.4 years; mean ejection fraction: 34.9 +/- 10.6%) underwent CPET. Subjects were tracked for sudden versus pump-failure cardiac mortality over 27.8 +/- 25.2 months.

RESULTS

Seventeen patients died from SCD, and 17 died from cardiac pump failure. Survivors showed significantly higher peak VO2 (16.8 +/- 4.5 ml x kg(-1) x min(-1)) and lower VE/VCO2 slope (32.8 +/- 6.4) and prevalence of EOB (20.3%), compared with subjects who experienced arrhythmic (13.5 +/- 3.2 ml x kg(-1) x min(-1); 41.5 +/- 11.4; 100%) or nonarrhythmic (14.1 +/- 4.7 ml x kg(-1) x min(-1); 38.1 +/- 7.3; 47.1%) deaths (p < 0.05). At Cox regression analysis, all variables were significant univariate predictors of both sudden and pump failure death (p < 0.01). Multivariate analysis, including left ventricular (LV) ejection fraction, LV end systolic volume, and LV mass selected EOB, was the strongest predictor of both overall mortality (chi-square: 38.7, p < 0.001) and SCD (chi-square: 44.7, p < 0.001), whereas VE/VCO2 slope was the strongest ventilatory predictor of pump failure death (chi-square: 11.8, p = 0.001).

CONCLUSIONS

Exercise oscillatory breathing is an independent predictor of SCD in patients with CHF and might help as an additional marker for prioritization of antiarrhythmic strategies.

Effect of biventricular pacing on the exercise pathophysiology of heart failure

BACKGROUND

Biventricular pacing (BVP) is used for cardiac resynchronization therapy in wide-QRS-complex heart failure. We sought to quantify the effect of BVP on the exercise pathophysiology of heart failure patients.

METHODS

Using cardiopulmonary exercise testing, we analyzed exercise data for a multicenter study sponsored by St. Jude Medical. Patients had pacemaker electrodes implanted in both ventricles in the standard manner and were randomized by St. Jude before exercise testing. Exercise measurements included peak oxygen uptake (Vo(2)), peak O(2) pulse, anaerobic threshold (AT), and ventilatory equivalent for CO(2) (reflecting change in peak exercise cardiac output, stroke volume, maximal sustainable exercise capacity, and ventilation-perfusion mismatching, respectively) at baseline and at a 6-month follow-up. The studies included progressively and uniformly increasing work rate to maximum tolerance. The investigators were blinded both to sponsor-controlled randomization and pacemaker status. There were 239 paired 6-month studies, as follows: 47 studies served as the control with the pacemaker off (ie, the BVP-OFF group); and 192 patients received pacing (ie, the BVP-ON group).

RESULTS

The BVP-ON group significantly improved in all exercise parameters in contrast to the control group (p < 0.0001). When baseline measurements for the BVP-ON group were ranked in quintiles, only patients in the three functionally worst quintiles improved significantly at 6 months (peak Vo(2) < 11.6 mL/min/kg, AT < 7.6 mL/min/kg, peak O(2) pulse < 12.0 mL/beat, and minute ventilation/Vco(2) ratio at AT > 38.1) [p < 0.01 to < 0.0001].

CONCLUSION

BVP benefited aerobic function and ventilation-perfusion mismatching most in those patients with the greatest physiologic impairment.

Exercise training reduces sympathetic nerve activity in heart failure patients treated with carvedilol

BACKGROUND

Evidence suggests that carvedilol decreases muscle sympathetic nerve activity (MSNA) in patients with heart failure (HF) but carvedilol fails to improve forearm vascular resistance and overall functional capacity. Exercise training in HF reduces MSNA and improves forearm vascular resistance and functional capacity.

AIMS

To investigate whether the beneficial effects exercise training on MSNA are maintained in the presence of carvedilol.

METHODS AND RESULTS

Twenty seven HF patients, NYHA Class II-III, EF <35%, peak VO(2) <20 ml/kg/min, treated with carvedilol were randomly divided into two groups: exercise training (n=15) and untrained (n=12). MSNA was recorded by microneurography. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. The four-month training program consisted of three 60-min exercise/week on a cycloergometer. Baseline parameters were similar between groups. Exercise training reduced MSNA (-14+/-3.3 bursts/100 HB, p=0.001) and increased forearm blood flow (0.6+/-0.1 mL/min/100 g, p<0.001) in HF patients on carvedilol. In addition, exercise training improved peak VO(2) in HF patients (20+/-6%, p=0.002). MSNA, FBF and peak VO(2) were unchanged in untrained HF patients on carvedilol.

CONCLUSION

Exercise training reduces MSNA in heart failure patients treated with carvedilol. In addition, the beneficial effects of exercise training on muscle blood flow and functional capacity are still realized in patients on carvedilol.

N-Terminal Prohormone Brain Natriuretic Peptide as a Marker for Detecting Low Functional Class Patients and Candidates for Cardiac Transplantation: Linear Correlation With Exercise Tolerance

BACKGROUND

N-terminal prohormone brain natriuretic peptide (NT Pro BNP) plasma levels have been associated with indices of left ventricular (LV) function and aerobic capacity in heart failure. The aim of our study was to use NT Pro BNP for the prediction of low functional class patients and also to detect candidates for cardiac transplantation.

METHODS

We studied 100 patients with impaired left ventricular (LV) function. Mean LV ejection fraction (LVEF) was 35% +/- 9%. Blood samples for NT Pro BNP assessment were taken at baseline during treadmill exercise testing. LV cavity diameters, left atrial size, and LVEF were measured by echocardiography.

RESULTS

Plasma levels of NT Pro BNP correlated significantly with peak oxygen consumption (VO(2)) values (r = -0.77, p < 0.001). LVEF correlated well with NT Pro BNP (r = -0.67, p < 0.001). NT Pro BNP plasma levels correlated strongly with New York Heart Association functional class (r = 0.70, p < 0.001). NT Pro BNP values exceeding 335 pg/ml showed 83% sensitivity and 76% specificity for detecting VO(2) values below 20 ml/kg/min (area under the curve [AUC] = 86%, p < 0.001). NT Pro BNP plasma levels exceeding 1,190 pg/ml showed 83% sensitivity and 86% specificity for detecting VO(2) of less than 14 ml/kg/min (AUC = 90%, p < 0.001). NT Pro BNP plasma levels exceeding 1,610 pg/ml showed 87% sensitivity and specificity 82% for detecting VO(2) of less than 10 ml/kg/min (AUC = 90%, p < 0.001). NT Pro BNP plasma levels exceeding 680 pg/ml showed 91% sensitivity and 73% specificity for detecting LVEF of less than 28% (AUC = 86%, p < 0.001).

CONCLUSIONS

NT Pro BNP plasma levels correlate both with LVEF and aerobic capacity, can predict low functional cardiopulmonary exercise capacity in patients with impaired left ventricular function, and are useful for detecting candidates for cardiac transplantation.

The Prognostic Value of Ventilatory Efficiency with Beta-Blocker Therapy in Heart Failure

PURPOSE

Beta-blockade (BB) has been shown to improve outcomes among patients with heart failure (HF). The impact this pharmacological approach has on the prognostic information gained from cardiopulmonary exercise testing (CPX) is, however, unclear.

METHODS

Four hundred seventeen subjects diagnosed with HF underwent CPX. The numbers of subjects prescribed and not prescribed a BB agent were 167 and 250, respectively. Subjects were tracked for cardiac-related mortality after CPX.

RESULTS

Values are reported for the no-BB versus the BB group throughout. Age (57.9 +/- 13.3 vs 55.6 +/- 12.5), peak VO2 (16.2 +/- 5.7 vs 16.5 +/- 5.5 mL x kg(-1) x min(-1)), VE/VCO2 slope (34.2 +/- 9.0 vs 33.2 +/- 7.4), and peak RER (1.07 +/- 0.16 vs 1.05 +/- 0.14) were similar between groups (P > 0.05). Multivariate Cox regression analysis revealed that the VE/VCO2 slope was the superior predictor of death in both groups (chi-square: 71.9, P < 0.001; and 18.4, P < 0.001). The optimal threshold values for VE/VCO2 slope in the no-BB and BB groups were 36.0 and 34.3, respectively.

CONCLUSIONS

The results of the present study indicate that BB does not alter the prognostic value/characteristics of the VE/VCO2 slope. Findings from previous investigations examining the prognostic significance of CPX predominantly using HF groups not receiving a BB agent may, therefore, still be applicable in modern-day clinical practice.

Exercise Capacity of Cardiac Asymptomatic Hereditary Hemochromatosis Subjects

PURPOSE

The exercise capacity of cardiac asymptomatic subjects with hereditary hemochromatosis (HH) has not been well described. In this study, we tested whether the iron overload associated with HH affected exercise capacity with a case control study design.

METHODS

Forty-three HH and 21 normal control subjects who were New York Heart Association functional class I underwent metabolic stress testing using the Bruce protocol at the clinical center of the National Institutes of Health. Exercise capacity was assessed with minute ventilation (.VE), oxygen uptake (.VO2), and carbon dioxide production (.VCO2) using a breath-by-breath respiratory gas analyzer.

RESULTS

The exercise capacity of HH subjects was not statistically different from that of control subjects (exercise time 564 +/- 135 vs 673 +/- 175 s, P = 0.191; peak .VO2 29.6 +/- 6.4 vs 32.5 +/- 6.7 mL.kg(-1).min(-1), P = 0.109; ventilatory threshold 19.0 +/- 3.4 vs 21.0 +/- 5.0 mL.min(-1).kg(-1), P = 0.099; data are for HH vs control subjects). Ventilatory efficiency was comparable between groups (.VE/.VCO2 slope 23.7 +/- 3.2 vs 23.4 +/- 4.2, P = 0.791). No significant correlation between the markers of iron levels and the markers of exercise capacity was noted. Iron depletion by 6-month phlebotomy therapy in 18 subjects who were newly diagnosed did not affect exercise testing variables (exercise time 562 +/- 119 vs 579 +/- 118 s, P = 0.691; peak .VO2 29.5 +/- 3.7 vs 29.1 +/- 4.7 mL.kg(-1).min(-1), P = 0.600; ventilatory threshold 18.5 +/- 2.8 vs 17.9 +/- 3.8 mL.kg(-1).min(-1), P = 0.651; data are from before and after phlebotomy therapy). Abnormal ischemic electrocardiographic responses and complex arrhythmias were more frequently seen in HH subjects.

CONCLUSIONS

The aerobic exercise capacity of asymptomatic HH subjects seems not to be statistically different from that of normal subjects. The iron levels do not seem to affect exercise capacity in asymptomatic HH subjects.

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.

Exercise testing with concurrent beta-blocker usage: is it useful? What do we learn?

Cardiopulmonary exercise testing (CPET) has been used for the assessment of severity of heart failure (HF), secondary to left ventricular systolic dysfunction. Initial studies determined that oxygen consumption (VO2) during exercise, as a measure of functional capacity, correlated well with the hemodynamic responses related to chronic HF. These studies led to the use of peak VO2 as a prognostic indicator in chronic HF. In addition, the use of several ventilatory parameters, eg, minute ventilation/carbon dioxide production during submaximal and peak exercise, were shown to have additive and (in some studies) superior prognostic value in patients with chronic HF. However, most of these studies were performed before beta-adrenergic blockade became the main focus of therapy in chronic HF. Unlike other drugs used in the treatment of HF, these drugs do not consistently improve exercise capacity as measured by peak VO2. Several retrospective studies and one prospective study have examined the effect of long-term beta-blocker therapy on the prognostic value of CPET in patients with chronic HF. These studies indicate that patients on beta-blockers have improved overall cardiovascular outcomes compared with patients not on these drugs. In addition, peak exercise VO2 still has prognostic value in beta-blocked patients; however, the thresholds for increased risk and need for transplantation have to be lower than in patients not on these drugs. There appears to be a real demand for a comprehensive survival score tool that includes the use of beta-blockade, along with CPET performance.

Carvedilol reduces exercise-induced hyperventilation: A benefit in normoxia and a problem with hypoxia

AIMS

To evaluate whether carvedilol influences exercise hyperventilation and the ventilatory response to hypoxia in heart failure (HF).

METHODS AND RESULTS

Fifteen HF patients participated to this double blind, randomised, placebo controlled, cross-over study. Patients were evaluated by quality of life questionnaire, echocardiography, pulmonary function and cardiopulmonary exercise tests (ramp and constant workload) both in normoxia (FiO2 = 21%) and hypoxia (FiO2 = 16%, equivalent to a simulated altitude of 2000 m). Carvedilol improved clinical condition and reduced left ventricle size, but had no effect on lung mechanics. In normoxia during exercise, ventilation was lower, V(CO2) unchanged and PaCO2 (constant workload) or PetCO2 (ramp) higher with carvedilol, exercise capacity was unchanged (peak workload 92+/-22 and 90+/-22W for placebo and carvedilol, respectively). Abnormal V(E)/V(CO2) slope was reduced by carvedilol. Hypoxia increased ventilation but less with carvedilol; exercise capacity decreased to 87+/-21W (placebo) and to 80+/-11 W (carvedilol, p < 0.01). With hypoxia, carvedilol decreased V(E)/V(CO2) slope. At constant workload exercise with hypoxia, PaO2 decreased to 69+/-6 mm Hg (placebo) and to 64+/-5 (carvedilol, p < 0.01).

CONCLUSION

Carvedilol reduced hyperventilation possibly by reducing peripheral chemoreflex sensitivity as suggested by PaCO2 increase with normoxia and PaO2 decrease with hypoxia without V(CO2) and V(D)/V(T) changes. Lessening hyperventilation is beneficial when breathing normally, but detrimental when hyperventilation is needed for exercise at high altitude.

Changes in exercise capacity, ventilation, and body weight following heart transplantation

AIMS

Peak oxygen uptake adjusted to body weight (peak VO(2)) and ventilatory efficiency (VE/VCO(2)-slope) are important prognostic parameters in chronic heart failure. Our study prospectively examined changes in these parameters over 24 months following heart transplantation (HTx) and evaluated the potentially confounding effects of weight gain.

METHODS AND RESULTS

One hundred patients with chronic heart failure (16 female, mean age at HTx 53.9+/-9.6 years) underwent cardiopulmonary exercise testing before and 3, 6, 12 and/or 24 months after HTx. Twenty-five healthy individuals served as matched normals. VE/VCO(2)-slope during exercise improved significantly at 6 (-23.7%), 12 (-21.3%), and 24 months (-32.3%; all p<0.002 vs. baseline). At 6 months, VE/VCO(2)-slopes were similar to the matched normals (31.8+/-4.3), 46 of 78 patients achieved values within the 95% confidence interval of normal. Peak VO(2) increased significantly after HTx at 6 (+31.8%), 12 (+36.2%), and 24 months (+42.2%; all p<0.005). None of the patients reached values within the 95% CI of normal. Although VE/VCO(2)-slope and peak VO(2) were correlated inversely at every time point (p<0.03), reduction in VE/VCO(2)-slope did not correlate with increase in peak VO(2). Symptoms that limited exercise changed from dyspnoea before HTx to leg fatigue after HTx.

CONCLUSION

Following HTX, VE/VCO(2)-slope returns to normal values in the majority of patients; however, despite improvement, peak VO(2) remains abnormal in all patients. Symptoms causing patients to stop exercising change from dyspnoea to leg fatigue.

[Exercise training in cardiac patients: usefulness of the cardiopulmonary exercise test]

Exercise training is currently including in the treatment of coronary arterial disease patients, in patients with left ventricular dysfunction as well as in patients who underwent cardiac transplantation or cardiac surgery. However methods of prescribing exercise-training programs are difficult to determine and must be adapted for each patient Exercise test with gas analysis through the determination of anaerobic threshold may help to understand the physiopathological mechanism related to exercise limitation in these patients. Exercise test may help to precise exercise intensity during cardiac rehabilitation and may assess the benefits on exercise tolerance.