Treadmill Cardiopulmonary Exercise Testing Research Articles

The effect of rosiglitazone on integrated cardiovascular performance, cardiac structure, function and myocardial triglyceride: trial design and rationale

The thiazolidinedione (TZD) class of medications has been associated with increased risk for peripheral oedema, as well as incident and worsening heart failure (HF). The mechanism of these observed effects remains unclear. Here we present the rationale and study design for a randomised clinical trial designed to evaluate the cardiac effects of rosiglitazone on integrated cardiovascular performance, cardiac structure and function. The study is a randomised, single-centre, double-blind, placebo-controlled, parallel-group clinical trial to evaluate the effect of rosiglitazone on integrated cardiovascular performance in a cohort of patients with type 2 diabetes mellitus (T2DM) at increased risk for developing heart failure (HF). Participants will be randomised to receive rosiglitazone or matching placebo for six months. All subjects will undergo maximal treadmill cardiopulmonary exercise testing at baseline and after six months on study drug, with the primary trial end point of peak oxygen uptake indexed to fat-free mass (VO 2peak-FFM). Approximately two-thirds of the study cohort will undergo cardiac magnetic resonance imaging (MRI) and spectroscopy (MRS) at baseline and after six months of study therapy to assess cardiac structure, function and myocardial triglyceride content. While concerns for peripheral oedema and HF continue to confound clinical use of TZD medications, the direct cardiac effects of these drugs remain poorly understood and the clinical relevance of these clinical observations remains unclear. The present study will combine a series of state-of-the-art assessments to evaluate the cardiac effects of rosiglitazone treatment.

The Relationship Between Heart Rate Reserve and Oxygen Uptake Reserve in Heart Failure Patients on Optimized and Non-Optimized Beta-Blocker Therapy

BACKGROUNDThe relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in heart failure patients either on non-optimized or off beta-blocker therapy is known to be unreliable. The aim of this study was to evaluate the relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in heart failure patients receiving optimized and non-optimized beta-blocker treatment during a treadmill cardiopulmonary exercise test.METHODSA total of 27 sedentary heart failure patients (86% male, 50±12 years) on optimized beta-blocker therapy with a left ventricle ejection fraction of 33±8% and 35 sedentary non-optimized heart failure patients (75% male, 47±10 years) with a left ventricle ejection fraction of 30±10% underwent the treadmill cardiopulmonary exercise test (Naughton protocol). Resting and peak effort values of both the percentage of oxygen consumption reserve and percentage of heart rate reserve were, by definition, 0 and 100, respectively.RESULTSThe heart rate slope for the non-optimized group was derived from the points 0.949±0.088 (0 intercept) and 1.055±0.128 (1 intercept), p<0.0001. The heart rate slope for the optimized group was derived from the points 1.026±0.108 (0 intercept) and 1.012±0.108 (1 intercept), p=0.47. Regression linear plots for the heart rate slope for each patient in the non-optimized and optimized groups revealed a slope of 0.986 (almost perfect) for the optimized group, but the regression analysis for the non-optimized group was 0.030 (far from perfect, which occurs at 1).CONCLUSIONThe relationship between the percentage of oxygen consumption reserve and percentage of heart rate reserve in patients on optimized beta-blocker therapy was reliable, but this relationship was unreliable in non-optimized heart failure patients.

Heart Rate Dynamics During A Treadmill Cardiopulmonary Exercise Test in Optimized Beta-Blocked Heart Failure Patients

BACKGROUNDCalculating the maximum heart rate for age is one method to characterize the maximum effort of an individual. Although this method is commonly used, little is known about heart rate dynamics in optimized beta-blocked heart failure patients.AIMThe aim of this study was to evaluate heart rate dynamics (basal, peak and % heart rate increase) in optimized beta-blocked heart failure patients compared to sedentary, normal individuals (controls) during a treadmill cardiopulmonary exercise test.METHODSTwenty-five heart failure patients (49±11 years, 76% male), with an average LVEF of 30±7%, and fourteen controls were included in the study. Patients with atrial fibrillation, a pacemaker or noncardiovascular functional limitations or whose drug therapy was not optimized were excluded. Optimization was considered to be 50 mg/day or more of carvedilol, with a basal heart rate between 50 to 60 bpm that was maintained for 3 months.RESULTSBasal heart rate was lower in heart failure patients (57±3 bpm) compared to controls (89±14 bpm; p<0.0001). Similarly, the peak heart rate (% maximum predicted for age) was lower in HF patients (65.4±11.1%) compared to controls (98.6±2.2; p<0.0001). Maximum respiratory exchange ratio did not differ between the groups (1.2±0.5 for controls and 1.15±1 for heart failure patients; p=0.42). All controls reached the maximum heart rate for their age, while no patients in the heart failure group reached the maximum. Moreover, the % increase of heart rate from rest to peak exercise between heart failure (48±9%) and control (53±8%) was not different (p=0.157).CONCLUSIONNo patient in the heart failure group reached the maximum heart rate for their age during a treadmill cardiopulmonary exercise test, despite the fact that the percentage increase of heart rate was similar to sedentary normal subjects. A heart rate increase in optimized beta-blocked heart failure patients during cardiopulmonary exercise test over 65% of the maximum age-adjusted value should be considered an effort near the maximum. This information may be useful in rehabilitation programs and ischemic tests, although further studies are required.

Flattening of Oxygen Pulse during Exercise May Detect Extensive Myocardial Ischemia

Flattening of oxygen pulse curve during incremental cardiopulmonary exercise testing has been proposed for the improvement of diagnostic accuracy of exercise-induced myocardial ischemia. In this study, we compare the oxygen pulse response to incremental treadmill exercise in patients with and without ischemia as detected by myocardial perfusion scintigraphy. Eighty-seven patients referred to exercise myocardial perfusion scintigraphy were also evaluated with incremental treadmill cardiopulmonary exercise testing. One investigator prospectively identified patients who presented transient exercise-induced perfusion defects on 99mTc sestamibi myocardial scintigraphies. Another investigator evaluated the response of oxygen pulse to incremental exercise testing without knowledge of electrocardiographic response or scintigraphic findings. Exercise myocardial perfusion scintigraphy detected transient perfusion defects in 36% of the patients. Compared with patients with normal perfusion studies, patients with exercise-induced ischemia presented similar peak double product, peak oxygen uptake, and anaerobic threshold. Oxygen pulse at 25% of peak (ischemia: 9.7 +/- 2 mL per beat; no ischemia: 9.3 +/- 2 mL per beat), 50% of peak (11.2 +/- 3 vs 10.8 +/- 3 mL per beat), 75% of peak (12.5 +/- 3 vs 11.9 +/- 3 mL per beat), and at peak exercise (13 +/- 4 vs 13 +/- 4 mL per beat) were not different in exercise-induced ischemia and normal groups, respectively. However, patients who presented extensive transient perfusion defects during exercise had a lower peak oxygen pulse (12.8 +/- 3.8 vs 16.4 +/- 4.6 mL per beat; P < 0.05). The analysis of the oxygen pulse response to incremental exercise test does not identify mild myocardial ischemia. Flattening of oxygen pulse response during incremental exercise might be present only with extensive myocardial ischemia.

VE/VCO2 slope is associated with abnormal resting haemodynamics and is a predictor of long‐term survival in chronic heart failure

Patients with chronic heart failure (CHF) present with exercise-induced hyperpnea, but its pathophysiological mechanism has not been thoroughly investigated. We aimed to determine the relationship between exercise-induced hyperpnea, resting haemodynamic measurements and the validity of ventilatory response (V(E)/V(CO(2)) slope) as a mortality predictor in CHF patients. Ninety-eight CHF patients (90M/8F) underwent a symptom-limited treadmill cardiopulmonary exercise test (CPET). Right heart catheterization and radionuclide ventriculography were performed within 72 h of CPET. Twenty-seven patients died from cardiac causes during 20+/-6 months follow-up. Non-survivors had a lower peak oxygen consumption (V(O(2)p)), (16.5+/-4.9 vs. 20.2+/-6.1, ml/kg/min, p=0.003), a steeper V(E)/V(CO(2)) slope (34.8+/-8.3 vs. 28.9+/-4.8, p<0.001) and a higher pulmonary capillary wedge pressure (PCWP) (19.5+/-8.6 vs. 11.7+/-6.5 mm Hg, p=0.008) than survivors. By multivariate survival analysis, the V(E)/V(CO(2)) slope as a continuous variable was an independent prognostic factor (chi(2): 8.5, relative risk: 1.1, 95% CI: 1.03-1.18, p=0.004). Overall mortality was 52% in patients with V(E)/V(CO(2)) slope > or =34 and 18% in those with V(E)/V(CO(2)) slope <34 (log rank: 18.5, p<0.001). In a subgroup of patients (V(O(2)p): 10-18 ml/kg/min), V(E)/V(CO(2)) slope was a significant predictor of mortality (relative risk: 6.2, 95% CI: 1.7-22.2, p=0.002). Patients with high V(E)/V(CO(2)) slope had higher resting PCWP (19.9+/-9.1 vs. 11.3+/-5.7 mmHg, p<0.001) and V(E)/V(CO(2)) slope correlated significantly with PCWP (r: 0.57, p<0.001). The V(E)/V(CO(2)) slope, as an index of ventilatory response to exercise, improves the risk stratification of CHF patients. Interstitial pulmonary oedema may be a pathophysiological mechanism of inefficient ventilation during exercise in these patients.

Prognostic characteristics of cardiopulmonary exercise testing in heart failure: comparing American and European models

Cardiopulmonary exercise testing (CPET) in the heart failure population is a standard of care in both American and European clinics, although the mode of exercise typically differs. The purpose of the present study was to compare the prognostic characteristics of peak oxygen consumption (VO2) and the minute ventilation-carbon dioxide production (VE/VCO2) slope between two independent heart failure groups. One hundred and two subjects underwent maximal exercise CPET using bicycle ergometry at San Paolo Hospital in Milan, Italy (SPH) and 105 subjects underwent treadmill CPET at Virginia Commonwealth University in Richmond, Virginia (VCU). Subjects were tracked for cardiac-related mortality for a 1-year period after CPET. There were 13 cardiac-related deaths over the 1-year tracking period in both groups. Optimal prognostic threshold values for peak VO2 were 12.9 ml O2/kg per min (sensitivity 81%, specificity 69%) in the SPH group and 12.0 ml O2/kg per min (sensitivity 74%, specificity 69%) in the VCU group. An optimal prognostic threshold value for the VE/VCO2 slope was 34.4 in the SPH (sensitivity 61%, specificity 85%) and 34.5 in the VCU (sensitivity 64%, specificity 93%) groups. The prognostic characteristics of peak VO2 and the VE/VCO2 slope were similar between the two centers. These results suggest that the mode of exercise does not greatly impact the prognostic utility of CPET responses in heart failure. They further suggest that prognostic guidelines for the application of CPET in heart failure may be applied globally, irrespective of differences in testing modality.

Exercise Capacity and Biochemical Profile during Exercise in Patients with Glycogen Storage Disease Type I

Glycogen storage disease type I (GSD-I) is an inherited disorder of carbohydrate metabolism. Hepatic glucose-6-phosphatase is deficient, leading to impaired gluconeogenesis and glycogenolysis. Patients prevent fasting hypoglycemia by frequent feeds of low glycemic index foods. Normal muscle does not contain glucose-6-phosphatase, and GSD-I is usually classified as a hepatic glycogenosis. However, clinical experience has suggested that patients have decreased cardiovascular fitness, but this had not been formally investigated. This paper reports the results of maximal treadmill cardiopulmonary exercise testing in adult patients with GSD-I. It documents a major reduction in exercise capacity in these patients and demonstrates biochemical aspects of exercise that are different from those of normal controls. All patients showed a reduction in exercise capacity, but there was a wide range of exercise tolerance. Additional work needs to address whether improved adherence to or intensification of therapy in adulthood will ameliorate exercise intolerance.

Resting Lung Function and Hemodynamic Parameters as Predictors of Exercise Capacity in Patients With Chronic Heart Failure

The aim of this study was to examine the role of resting pulmonary function and hemodynamic parameters as predictors of exercise capacity in patients with chronic heart failure. Fifty-one patients with chronic heart failure underwent resting pulmonary function testing, including inspiratory capacity (IC) and symptom-limited, treadmill cardiopulmonary exercise testing (CPET). Right-heart catheterization and radionuclide ventriculography were performed within 2 days of CPET. Mean (+/- SD) left ventricular ejection fraction was 31 +/- 12% and cardiac index was 2.34 +/- 0.77 L/min/m(2). Percentage of predicted FEV(1) was 92 +/- 14%, percentage of predicted FVC was 94 +/- 15%, FEV(1)/FVC was 81 +/- 4%, and percentage of predicted IC was 84 +/- 18%. Mean peak oxygen uptake (peak O(2)) was 17.9 +/- 5.4 mL/kg/min. Analysis of variance among the three functional Weber classes showed statistically significant differences for pulmonary capillary wedge pressure (PCWP) and IC. Specifically, the more severe the exercise intolerance, the lower was IC and the higher was PCWP. In a multivariate stepwise regression analysis, using peak O(2) (liters per minute) as the dependent variable and the pulmonary function test measurements as independent variables, the only significant predictor selected was IC (r = 0.71, p < 0.0001). In a final stepwise regression analysis including all the independent variables of the resting pulmonary function tests and hemodynamic measurements, the two predictors selected were IC and PCWP (r(2) = 0.58). In patients with chronic heart failure, IC is inversely related to PCWP and is a strong independent predictor of functional capacity.

Evaluación de tres cuestionarios de actividad en pacientes con insuficiencia cardíaca

The activity questionnaire most frequently used in heart failure, the New York Heart Association Classification, does not correlate well with peak oxygen uptake. The correlation of this variable with other activity questionnaires was analyzed in 83 patients (69 with heart failure and 14 control patients), 61.5 11 years old, who were interviewed and classified according to the Canadian Cardiovascular Society Classification. The Dyspnea-Fatigue Index and functional capacity according to the Specific Activity Questionnaire were determined for each patient. Subsequently, the treadmill cardiopulmonary exercise test (Naughton) was performed and the following correlations with peak oxygen uptake were found: Canadian Cardiovascular Society, r = 0.39; Dyspnea-Fatigue Index, r = 0.44; Specific Activity Questionnaire, r = 0.38. p < 0.001 for all three. The Dyspnea-Fatigue Index yielded the best correlation, although it was only slightly better than the Canadian Cardiovascular Society Classification, which is easier to obtain.

Impact of serial changes in cardiac hemodynamics on exercise performance in patients with heart failure due to ischemic and nonischemic cardiomyopathy

Although prior studies have examined the role of central and peripheral hemodynamics on exercise tolerance within populations of patients with heart failure, a clear relation between hemodynamics and exercise has not been demonstrated. This may be due to the inability to control for other factors that may influence exercise performance. To isolate the impact of hemodynamics on exercise, we studied the relation between changes in these factors within individual patients studied on 2 occasions. A consecutive series of 133 ambulatory patients with heart failure were evaluated on 2 separate occasions with right-sided cardiac catheterization and treadmill cardiopulmonary exercise testing. Linear regression models were constructed and correlation coefficients were determined to examine the relation between changes in hemodynamic variables and changes in exercise variables over time for each patient. A significant correlation between peak oxygen consumption (VO2) and pulmonary arterial wedge pressure was found for both the first (r = −0.316, p <0.001) and second (r = −0.183, p = 0.029) tests. A stronger inverse correlation between the change in pulmonary arterial wedge pressure and change in peak VO2 was observed in the study patients (r = −0.470, p <0.001). Similar correlations were found between change in peak VO2 and changes in pulmonary arterial pressures. Changes in left ventricular filling pressure influence exercise tolerance in patients with heart failure due to left ventricular systolic dysfunction. Interpretation of cardiopulmonary exercise testing for the purpose of determining cardiac transplantation eligibility will be improved with knowledge of left ventricular filling pressure.

Aerobic exercise physiology in a professional rugby union team

Introduction: In professional rugby, different positional roles may require different levels of aerobic fitness. Forward and backline players from a team of elite rugby players were tested to evaluate the differences between the two groups. Methods: 28 male players, 15 backs and 13 forwards, underwent maximal treadmill cardiopulmonary exercise testing (CPX), lung spirometry, a 3 km timed run, and body fat measurement. Results: Peak oxygen uptake was higher in backs than in forwards (peak VO 2 48.3±2.1 vs. 41.2±2.7 ml kg −1 min −1, P<0.05) with no significant difference in peak respiratory exchange ratio (1.08±0.02 vs. 1.07±0.02, P=NS), exercise time (1306±39.7 vs. 1217±25.1 s, P=NS) or time for 3 km run (667.5±14.1 vs. 699.0±20.7 s, P=NS). However, the forwards were taller and heavier (height 190.2±2.2 vs. 179.5±1.3 cm, P<0.001, body mass 104±2.4 vs. 86.3±1.7 kg, P<0.0001) and had a higher fat content (body fat percentage 12.8±0.8 vs. 9.7±0.6%, P<0.01) and forced expiratory volume in 1 s (FEV1, 4.9±0.1 vs. 4.5±0.2 l, P<0.05). There was a significant negative correlation between peak VO 2, 3 km run time ( r=−0.45, P<0.05) and weight ( r=−0.54, P<0.003) for all subjects. Conclusion: Backline players have a higher peak oxygen uptake per kilogram than forwards, although the cardiopulmonary exercise test duration, degree of anaerobic metabolism and 3 km run time are not significantly different. These results could be due to the two groups’ different body structure, being shorter, lighter and having a lower percentage body fat. These differences, which are likely to be a result of selection for specific roles in the game, should be taken into account when evaluating aerobic fitness within a rugby team.

Relation of changes over time in ventricular size and function to those in exercise capacity in patients with chronic heart failure

Background We studied the direction and magnitude of changes in left ventricular (LV) cavity size and mass over time and whether these changes were related to those in exercise performance in patients with chronic heart failure (CHF). Methods and Results The study group was composed of 59 patients (55 men aged 58 ± 10 years) with CHF and LV end-diastolic diameter (EDD) >55 mm. All underwent echocardiography and a treadmill cardiopulmonary exercise test within a 4-week interval (baseline) and again after a period of ≥4 months (median of 14 months). At baseline, the group as a whole had moderate to severe LV dysfunction with an EDD of 70 ± 9 mm, end-systolic diameter (ESD) of 60 ± 11 mm, and LV mass of 500 ± 200 g. The mean peak oxygen consumption (VO 2, 18 ± 6 mL/kg per minute) was unrelated to LV cavity size or mass. EDD increased in 37 (63%) of the patients and fell in 22 (37%) patients from the initial to the second test. The absolute magnitude of changes over time averaged 7 mm for EDD, 125 g for mass, and 6 mL/kg per minute for peak VO 2. Changes in LV size and mass per year were significantly related to those in peak VO 2 ( r = −0.49 for EDD, r = −0.56 for ESD, and r = −0.44 for LV mass, respectively, all P < .001) and ventilatory response to exercise ( r = 0.60, r = 0.58, and r = 0.72 for EDD, ESD, and LV mass; respectively, all P < .001). Conclusions Changes over time in objective measures of LV dimensions and mass, in patients with CHF are significantly related to those in exercise capacity and respiratory efficiency.

Exercise and heart failure. Relation of the severity of the disease to the anaerobic threshold and the respiratory compensation point.

OBJECTIVE - To identify, the anaerobic threshold and respiratory compensation point in patients with heart failure. METHODS - The study comprised 42 Men,divided according to the functional class (FC) as follows: group I (GI) - 15 patients in FC I; group II (GII) - 15 patients in FC II; and group III (GIII) - 12 patients in FC III. Patients underwent a treadmill cardiopulmonary exercise test, where the expired gases were analyzed. RESULTS - The values for the heart rate (in bpm) at the anaerobic threshold were the following: GI, 122+/-27; GII, 117+/-17; GIII, 114+/-22. At the respiratory compensation point, the heart rates (in bpm) were as follows: GI, 145+/-33; GII, 133+/-14; GIII 123+/-22. The values for the heart rates at the respiratory compensation point in GI and GIII showed statistical difference. The values of oxygen consumption (VO2) at the anaerobic threshold were the following (in ml/kg/min): GI, 13. 6+/-3.25; GII, 10.77+/-1.89; GIII, 8.7+/-1.44 and, at the respiratory compensation point, they were as follows: GI, 19.1+/-2. 2; GII, 14.22+/-2.63; GIII, 10.27+/-1.85. CONCLUSION - Patients with stable functional class I, II, and III heart failure reached the anaerobic threshold and the respiratory compensation point at different levels of oxygen consumption and heart rate. The role played by these thresholds in physical activity for this group of patients needs to be better clarified.

Effects of Dihydrocodeine on Chemosensitivity and Exercise Tolerance in Patients With Chronic Heart Failure

Objectives. We sought to test the hypothesis that suppression of chemosensitivity (respiratory response to arterial blood gases) with dihydrocodeine may improve dyspnea and exercise tolerance in patients with chronic heart failure.Background. Exertional dyspnea is a common limiting symptom in patients with chronic heart failure. The mechanisms underlying this symptom are not fully understood but may be related to increased ventilation caused, in part, by the augmentation of chemosensitivity. Suppression of chemosensitivity with mild opiates may thus improve this symptom as well as exercise tolerance.Methods. Twelve men with chronic heart failure (mean [± SE] age 65.5 ± 1.5 years, range 58 to 75; left ventricular ejection fraction 21.3 ± 3.0%, range 8 to 39) received placebo or dihydrocodeine (1 mg/kg body weight) on two separate days in a randomized, double-blind design. One hour later, hypoxic and hypercapnic chemosensitivities were assessed using the transient inhalations of pure nitrogen and the rebreathing of 7% carbon dioxide in 93% oxygen, followed by treadmill cardiopulmonary exercise testing. The symptoms of dyspnea and fatigue during the exercise test were assessed using a modified Borg scale from 0 to 10.Results. There was a significant fall in hypoxic and hypercapnic chemosensitivities with dihydrocodeine administration compared with placebo (0.447 ± 0.096 vs. 0.746 ± 0.104 liter/min per percent arterial oxygen saturation, p = 0.005; 2.480 ± 0.234 vs. 2.966 ± 0.283 liter/min per mm Hg, p = 0.01, respectively). Exercise duration was prolonged from 455 ± 27 s on placebo to 512 ± 27 s (p = 0.001) with dihydrocodeine, and peak oxygen consumption increased from 18.0 ± 0.6 to 19.7 ± 0.6 ml/kg per min (p = 0.002). The ventilatory response to exercise, characterized by the regression slope relating minute ventilation to carbon dioxide output, decreased from 34.19 ± 2.35 to 30.85 ± 1.91 (p = 0.01). With dihydrocodeine administration, the change in the modified Borg score for dyspnea was −0.80 (p = 0.003) at 6 min and −0.33 (p = 0.52) at peak exercise, whereas that for fatigue did not change significantly. Arterial oxygen saturation was maintained during exercise despite dihydrocodeine administration (99.3% at rest vs. 98.9% at peak exercise, p = 0.21).Conclusions. Augmented chemosensitivity is important in the pathophysiology of chronic heart failure. Its suppression with dihydrocodeine was associated with a reduction of exercise ventilation, an improvement in exercise tolerance and a decrease in breathlessness. Pharmacologic modulation of chemosensitivity may benefit patients with chronic heart failure and merits further investigation.(J Am Coll Cardiol 1997;29:147–52)>

Acute Alterations of Oxygen Uptake and Symptom-Limited Exercise Time in Patients With Mitral Stenosis After Balloon Valvuloplasty

To determine the acute influence of improvement in orifice area in mitral stenosis by percutaneous transluminal valvuloplasty (PTVP) on cardiopulmonary exercise capacity, treadmill walking time (TWT), oxygen uptake parameters at maximum exercise as well as at highest comparable workloads and parameters of breathing work were assessed pre- and post-PTVP. PTVP was carried out in 16 patients who had moderately severe mitral stenosis, bringing about an average increase in mitral valve orifice area from 1.0 +/- 0.1 cm2 to 2.2 +/- 0.5 cm2 (p < 0.0005). Based on standardized conditions, the patients (six in functional class A, five in class B, and five in class C according to Weber's classification) underwent symptom-limited treadmill cardiopulmonary exercise testing before as well as 2 days after PTVP. In addition, subgroup analysis (eight patients in sinus rhythm, eight patients in atrial fibrillation) was performed to determine a potential influence of the underlying cardiac rhythm on cardiopulmonary exercise parameters. To rule out a PTVP-independent training effect, a control group of ten patients with mitral stenosis underwent the same kind of cardiopulmonary exercise testing on 2 consecutive days. After-PTVP, TWT augmented by 19% (p < 0.0005) in all patients. Maximum oxygen uptake in percent of predicted maximal values at peak exercise and at anaerobic threshold was enhanced by 10% (p < 0.005). Ventilation at highest comparable workload was diminished by 10% (p < 0.025), whereas oxygen uptake and oxygen pulse at highest comparable workload did not differ, reflecting both unaltered cardiac output at comparable workloads and a more economic ventilation, respectively. Furthermore, PTVP-mediated alterations of TWT, but not of oxygen uptake at peak exercise were more pronounced in patients in sinus rhythm than in those in atrial fibrillation, reflecting more effective economization of cardiac work and ventilation in the former subgroup. Except for a statistically significant increase of TWT of 5%, no clinically relevant differences between both exercise tests were found with respect to oxygen uptake in the control group. Impaired cardiopulmonary fitness in patients with moderately severe mitral stenosis is improved substantially by PTVP immediately after the intervention, mainly the result of acute reduction of pulmonary congestion and subsequent decrease in dead space to tidal volume ratio. Adherence to standardized conditions is considered crucial for comparability of cardiopulmonary data.

Use of the cardiopulmonary exercise test to evaluate the patient with chronic heart failure.

Isotonic exercise testing imposes a physiological stress on the cardiopulmonary unit. Accordingly, monitoring of oxygen, carbon dioxide and air flow during an exercise test (i.e. a cardiopulmonary exercise test) can be used to assess heart function in patients with chronic heart failure. Specifically, an incremental treadmill cardiopulmonary exercise test represents a non-invasive means to determine aerobic capacity, or maximal oxygen uptake (VO2max ml min-1 kg-1), and anaerobic threshold (AT, ml min-1 kg-1). These objective measures of cardiopulmonary function are then used to grade the severity of failure and the functional capacity of the patient. In addition, they may be used to predict the cardiac reserve, or maximal cardiac index (CImax, l min-1 m-2) during exercise. That is, the severity is considered to be mild (class A) when AT greater than 14 or VO2max greater than 20, mild to moderate (class B) when AT falls between 11 and 14 or VO2max between 16 and 20, moderate to severe (class C) when AT ranges between 8 and 11 or VO2max between 10 and 16, and severe (class D) when AT less than 8 or VO2max less than 10. The predicted CImax for classes A, B, C and D are greater than 8, 6-8, 4-6 and less than 4, respectively. Finally, a major objective of medical therapy in patients with heart failure is to improve cardiac output and oxygen delivery to working skeletal muscle and thereby enhance effort tolerance. This therapeutic endpoint can be gauged by cardiopulmonary exercise testing from the response in AT and VO2max.