Treadmill Cardiopulmonary Exercise Testing Research Articles

Dobutamine stress for evaluation of right ventricular reserve in pulmonary arterial hypertension.

Right ventricular contractile response to pharmacological stress in pulmonary arterial hypertension (PAH) has not been characterised. We evaluated right ventricular contractile reserve in adults with PAH using dobutamine stress echocardiography. 16 PAH patients and 18 age-matched controls underwent low-dose dobutamine stress echocardiography. Contractile reserve was assessed by the change (Δ; peak stress minus rest value) in tricuspid annular plane systolic excursion (TAPSE) and tricuspid annular systolic velocity (S'). A subgroup of 13 PAH patients underwent treadmill cardiopulmonary exercise testing for peak oxygen uptake (V'O2peak). At rest, TAPSE and S' were reduced in the PAH group compared with controls (1.7 ± 0.4 versus 2.4 ± 0.2 cm and 9.7 ± 2.6 versus 12.5 ± 1.2 cm · s(-1), respectively; p<0.05). Contractile reserve was markedly attenuated in PAH compared to controls (ΔTAPSE 0.1 ± 0.2 versus 0.6 ± 0.3 cm and ΔS' 4.6 ± 2.8 versus 11.2 ± 3.6 cm · s(-1); p<0.0001). In the sub-group of PAH patients with preserved right ventricular systolic function at rest, contractile reserve remained depressed compared to controls. V'O2peak was significantly correlated with ΔS' (r=0.87, p=0.0003) and change in stroke volume (r=0.59, p=0.03). Dobutamine stress can reveal sub-clinical reduction in right ventricular contractile reserve in patients with PAH. A correlation with exercise capacity suggests potential clinical value beyond resting measurements.

Supervised Exercise Program Improves Aerobic Fitness in Patients Awaiting Abdominal Aortic Aneurysm Repair

Aerobic fitness is an important predictor of postoperative outcome in major surgery. In this study, we assess the effects of a period of preoperative exercise on aerobic fitness as measured by cardiopulmonary exercise testing (CPET) in patients scheduled for abdominal aortic aneurysm (AAA) repair. As part of a randomized trial, the first patients recruited in the intervention group were enrolled in a supervised exercise program of six week duration. Treadmill CPET parameters were measured before and after exercise preoperatively for these patients. These parameters were as follows: peak oxygen uptake (VO2 peak), anaerobic threshold (AT), and ventilator equivalents for oxygen and carbon dioxide (VE/VO2 and VE/VCO2, respectively). Total exercise time and the time at which AT was achieved were also recorded. A comparison between pre- and postexercise parameters was made to detect for a possible improvement in aerobic fitness. Twenty patients with AAA (17 men; mean age: 74.9 ± 5.9 years) were included in this study. Thirty-five percent of patients had a history of ischemic heart disease, 25% of obstructive airway disease, and 15% of cerebral vascular events. Seventy percent were previous smokers, and 15% were current smokers. Fifty-five percent of patients were taking aspirin and 75% were undergoing statin therapy. The median (interquartile range) VO2 peak at baseline was 18.2 (15.4-19.9) mL/kg/min, and after exercise was 19.9 (17.1-21.1; P=0.048). Median AT at baseline was 12.2 (10.5-14.9), and 14.4 (12.3-15.4) after exercise (P=0.023). Time of exercise tolerated also improved from a median of 379to 604sec (P=0.001). No significant changes were seen in VE/VO2, VE/VCO2, or the time at which AT was achieved. This study shows that cardiopulmonary aerobic fitness improves after a period of supervised exercise in patients scheduled for AAA repair. This is justification for a randomized trial to assess whether this affects morbidity and mortality after AAA repair.

Maximal Exercise Response Is Reduced in Patients with the Total Artificial Heart

Purpose Home discharge with the total artificial heart (TAH) necessitates a shift in focus to quality of life in the TAH patient (pt) including functional ability. The purpose of this study was to evaluate the cardiorespiratory responses to graded exercise in pts with the TAH compared to both advanced heart failure (HF) and LVAD pts. Methods and Materials A retrospective study was conducted on previously gathered data of TAH, LVAD and HF pts who underwent symptom-limited cardiopulmonary exercise testing (CPET). Clinical data was abstracted from the medical record and ANOVA was performed to compare groups. Results Fourteen TAH pts safely underwent treadmill CPET with results listed in Table 1 including p-values indicating significance. Clinical characteristics were similar between groups except for hemoglobin and BMI. Peak oxygen consumption (VO 2 ), %pred. VO2, VAT, %pred. VO2 @ VAT, OUES, and peak MAP were significantly lower in the TAH compared with LVAD and HF groups. Hemoglobin was also significantly lower in the TAH pt. Peak RER was significantly higher and a trend towards an elevated VE/VCO2 slope was noted in the TAH. Waveform analysis was available for 11 TAH pts wherein 9 out of 11 exhibited a full-fill pattern at peak exercise. Conclusions This is the first study to examine maximal exercise capacity in a group of TAH pts. Exercise capacity is significantly reduced in the TAH pt below that observed in LVAD and advanced HF. Although the TAH provides excellent cardiac output, limitations to performance on the CPET may be related to persistent anemia and limited ability of the pump to modulate output for activity. These data also provide a baseline for expected functional status and has implications on the ADL tolerance of these individuals.

Age-Related Maximum Heart Rate Among Ischemic and Nonischemic Heart Failure Patients Receiving β-Blockade Therapy

BackgroundEquations to predict maximum heart rate (HRmax) in heart failure (HF) patients receiving β-adrenergic blocking (BB) agents do not consider the cause of HF. We determined equations to predict HRmax in patients with ischemic and nonischemic HF receiving BB therapy. Methods and ResultsUsing treadmill cardiopulmonary exercise testing, we studied HF patients receiving BB therapy being considered for transplantation from 1999 to 2010. Exclusions were pacemaker and/or implantable defibrillator, left ventricle ejection fraction (LVEF) >50%, peak respiratory exchange ratio (RER) <1.00, and Chagas disease. We used linear regression equations to predict HRmax based on age in ischemic and nonischemic patients. We analyzed 278 patients, aged 47 ± 10 years, with ischemic (n = 75) and nonischemic (n = 203) HF. LVEF was 30.8 ± 9.4% and 28.6 ± 8.2% (P = .04), peak VO2 16.9 ± 4.7 and 16.9 ± 5.2 mL kg−1 min−1 (P = NS), and the HRmax 130.8 ± 23.3 and 125.3 ± 25.3 beats/min (P = .051) in ischemic and nonischemic patients, respectively. We devised the equation HRmax = 168 − 0.76 × age (R2 = 0.095; P = .007) for ischemic HF patients, but there was no significant relationship between age and HRmax in nonischemic HF patients (R2 = 0.006; P = NS). ConclusionsOur study suggests that equations to estimate HRmax should consider the cause of HF.

Reliability of Peak Exercise Testing in Patients With Heart Failure With Preserved Ejection Fraction

Exercise intolerance is the primary symptom in patients with heart failure and preserved ejection fraction (HFpEF), a major determinant of their decreased quality of life, and an important outcome in clinical trials. Although cardiopulmonary exercise testing (CPET) provides peak and submaximal diagnostic indexes, the reliability of peak treadmill CPET in patients >55 years of age with HFpEF has not been examined. Two CPETs were performed in 52 patients with HFpEF (70 ± 7 years old). The 2 tests were separated by an average of 23 ± 13 days (median 22) and performed under identical conditions, with no intervention or change in status between visits except for initiation of a placebo run-in. A multistep protocol for patient screening, education, and quality control was used. Mean peak oxygen consumption was similar on tests 1 and 2 (14.4 ± 2.4 vs 14.3 ± 2.3 ml/kg/min). Correlation coefficients and intraclass correlations from the testing days were determined (oxygen consumption, r = 0.85, p <0.001, intraclass correlation 0.855; ventilatory anaerobic threshold, r = 0.79, p <0.001, intraclass correlation 0.790; ventilation per carbon dioxide slope, r = 0.87, p <0.001, intraclass correlation 0.864; heart rate, r = 0.94, p <0.001, intraclass correlation 0.938). These results challenge conventional wisdom that serial baseline testing is required in clinical trials with exercise-capacity outcomes. In conclusion, in women and men with HFpEF and severe physical dysfunction, key submaximal and peak ET variables exhibited good reliability and were not significantly altered by a learning effect or placebo administration.

Functional and Hemodynamic Cardiac Determinants of Exercise Capacity in Patients With Systolic Heart Failure

Decreased exercise capacity is the main symptom in patients with heart failure (HF). We assessed the association among noninvasively determined maximal cardiac output at exercise, systolic and diastolic cardiac functions at rest, and peak oxygen uptake (pVo(2)) exercise capacity in patients with congestive HF. We studied 102 patients 62 ± 11 years of age with New York Heart Association class II to IV stable HF and left ventricular (LV) ejection fraction <45%. All patients underwent echocardiography and a treadmill cardiopulmonary exercise test for evaluation of pVo(2) corrected for fat-free mass. During the cardiopulmonary exercise test, cardiac output was estimated noninvasively and continuously using Nexfin HD. Fat-free mass-corrected pVo(2) was associated in an univariate linear regression analysis with peak exercise cardiac index (CI) (beta 0.511, p <0.001), LV end-diastolic pressure estimates (peak early diastolic filling velocity/early diastolic tissue velocity [E/e'], beta -0.363, p = 0.001), and right ventricular function (tricuspid annular plane systolic excursion, beta 0.393, p <0.001). In multivariate analysis peak exercise CI (beta 0.380, p = 0.001), but not cardiac output or LV ejection fraction at rest, was an independent predictor of pVo(2). Other independent predictors of pVo(2) were E/e' (beta -0.276, p = 0.009) and tricuspid annular plane systolic excursion (beta 0.392, p <0.001), also when adjusted for age and gender. In conclusion, peak CI is an independent predictor of fat-free mass-corrected pVo(2) in patients with systolic HF. Of all echocardiographic parameters at rest, right ventricular function and E/e' were independently and significantly associated with pVo(2), whereas LV ejection fraction at rest was not.

Cardiorespiratory parameters before and after acupuncture: observations in a healthy and diseased state

We read the paper titled “Acupuncture and exercise capacity: A case report” by Nascimento RC et al with great interest (1). The results of the study demonstrated that acupuncture is an efficient tool for improving the exercise capacity of an individual. However, some portions of the methodology remain unclear, and we would like to highlight some published data regarding the treadmill cardiopulmonary exercise test. Basically, a treadmill is a piece of equipment used to measure the status of the heart and is used as a diagnostic and prognostic measurement when the appropriate protocol is selected. We are interested in identifying the ramp protocol used by the authors. Additionally, it would be interesting to know whether the subjects completed the protocol before and after acupuncture treatment. For future case reports or studies, we suggest that the subjects recruited for a program to improve health and well-being need to undergo specific protocols, such as the Bruce or modified Bruce protocol, depending on the design of the exercise program (2). Commenting on the results, the authors reported that the patient showed improvement in his exercise capacity following acupuncture treatment. We would like to comment on the effect of the study on two types of clinical subjects. First, when the techniques are applied to neurological subjects (those paralyzed and semiconscious), oxygen consumption and other variables can improve. Similarly, when these techniques are applied to cardiac patients (those diagnosed as hypertensive), negative effects can occur. Physiologically, the amount of oxygen consumption may cause the heart to become stressed following acupuncture therapy. Under such conditions, the heart needs to pump more blood to cope with the demand, which may increase the heart rate and in turn increase blood pressure. Therefore, it can be said that the results of the study would be desirable for a particular population to increase exercise capacity when it is cautiouslxy used for patients with stable vital parameters. Overall, this is an interesting case report for discussion that may benefit individuals who attend a program to improve their well-being. The authors and the editor need to be applauded for highlighting such an innovative treatment for exercise capacity.

Six‐minute walk distance and work relationship with incremental treadmill cardiopulmonary exercise test in COPD

Cardiopulmonary exercise testing (CPET) is increasingly used to evaluate the overall impact of the illness on patients with chronic obstructive pulmonary disease (COPD). While laboratory tests of exercise performance are costly, the 6-min walk test (6-MWT) can be more easily performed. Although the main outcome commonly used in this field test is the distance walked in 6 min (6-MWD), this measure does not account for differences in body weight. Previous studies showed a good correlation between the work performed during the 6-MWT with incremental cycling CPET, an exercise modality more associated with quadriceps fatigability and with lower peak oxygen consumption than incremental walking tests. Evaluate the correlation between the 6-MWD and its derivative body weight-walking distance product, an estimation of the work performed during the 6-MWT, with peak from a treadmill CPET. Thirty COPD patients [forced expiratory volume in 1 s (FEV1) = 39 ± 13%; peak predicted] performed CPET to the limit of tolerance on a treadmill and 6-MWT, 48 h apart.6-MWD and work were correlated to resting and exercise functional variables. The work of walking during the 6-MWT provided greater associations with peak than observed with 6-MWD. This was the case for FEV1, forced vital capacity, inspiratory capacity, lung diffusion capacity for carbon monoxide, peak , carbon dioxide output, minute ventilation and double product (r = 0.57, r = 0.57, r = 0.73, r = 0.7, r = 0.75, r = 0.65, r = 0.51 and r = 0.4, respectively; all P < 0.05). A better association was found between the work estimated from the 6-MWT and peak achieved during CPET, in this case with a treadmill, than the 6-MWD alone.

Oxygen Pulse Kinetics in Fontan Patients During Treadmill Ramp Protocol Cardiopulmonary Exercise Testing

After single-ventricle palliation, patients have variable long-term functional outcomes. Cardiopulmonary exercise testing (CPET) is an assessment tool used to quantify functional outcome. Oxygen pulse kinetics during CPET, which can be an important indicator of dynamic changes in stroke volume reserve, has not been systematically studied in this population. This study aimed to analyze oxygen pulse kinetics during a treadmill ramp protocol among patients with Fontan physiology compared with that of normal subjects and to explore the ability of oxygen pulse kinetics to define functional status further. Peak oxygen pulse and change in oxygen pulse during ramp treadmill CPET were retrospectively collected and compared between 44 Fontan patients and 85 age- and sex-matched control subjects. The peak oxygen pulse was significantly lower in the Fontan group (9.80 ± 4.11 ml/beat) than in the control group (13.62 ± 4.7 ml/beat) (p ≤ 0.001). The resting oxygen pulse did not differ between the two groups (3.13 ± 1.23 vs. 3.09 ± 1.33 ml/beat; p = 0.88). The oxygen pulse was higher in the patients with chronotropic insufficiency, but the difference was not statistically significant (11.11 ± 4.97 vs. 9.25 ± 3.63 ml/beat; p = 0.17). Regression analysis showed a significant difference in the slope of the oxygen pulse-to-workload relationship. The Fontan group showed no relation between degree of reduction in the oxygen pulse from peak to end of exercise and the underlying defect, peak heart rate, peak oxygen consumption, ventilatory anaerobic threshold (VAT), expired volume (VE)/carbon dioxide output (VCO(2)) at the VAT, maximum heart rate, or minimum oxygen saturation. Analysis of oxygen pulse kinetics in Fontan patients suggests that there is an early and progressive limitation in stroke volume compared with control subjects. This limitation may be partially masked by increased oxygen extraction. In patients with chronotropic insufficiency, absolute or body surface area-indexed oxygen pulse may be higher than in those with a normal heart rate response. A composite assessment of the oxygen pulse and oxygen pulse kinetics, including the oxygen pulse slope and the percentage of reduction in oxygen pulse from peak to end of exercise, may allow a more comprehensive assessment of the degree of cardiac limitation in this group of patients.

StepWatch stride counting: Accuracy, precision, and prediction of energy expenditure in children

Accuracy and precision of the StepWatch (SW) was tested in typically developing youth (TDY) with the prediction of oxygen consumption derived from stride counts. Ten TDY (5 boys, 5 girls) with an average age 14.1 years (SD=2.2) enrolled. Participants underwent treadmill cardiopulmonary exercise testing (CPET) wearing two SW devices at 1, 2, 3, and 4 miles per hour (mph). Average sign-corrected disagreement for strides counted between the 2 monitors was 0.4 (0.52), 0.2 (0.42), 0.1 (0.32), and 0.1 (0.32) for 1, 2, 3, and 4 mph, respectively. The ratio of SW counts to observed manual counts averaged 100.03% with ICC=0.995. Oxygen consumption equations were derived from resting and walking VO(2), age, gender, and stride counts. Excellent accuracy and precision was documented for treadmill walking speeds up to 4 mph while VO(2) per number of strides taken appears to decrease with age and is lower in girls.

Prognostic value of a new cardiopulmonary exercise testing parameter in chronic heart failure: oxygen uptake efficiency at peak exercise — comparison with oxygen uptake efficiency slope

Introduction A growing body of evidence shows the prognostic value of oxygen uptake efficiency slope (OUES), a cardiopulmonary exercise test (CPET) parameter derived from the logarithmic relationship between O 2 consumption (VO 2) and minute ventilation (VE) in patients with chronic heart failure (CHF). Objective To evaluate the prognostic value of a new CPET parameter — peak oxygen uptake efficiency (POUE) — and to compare it with OUES in patients with CHF. Methods We prospectively studied 206 consecutive patients with stable CHF due to dilated cardiomyopathy — 153 male, aged 53.3 ± 13.0 years, 35.4% of ischemic etiology, left ventricular ejection fraction 27.7 ± 8.0%, 81.1% in sinus rhythm, 97.1% receiving ACE-Is or ARBs, 78.2% beta-blockers and 60.2% spironolactone — who performed a first maximal symptom-limited treadmill CPET, using the modified Bruce protocol. In 33% of patients an cardioverterdefibrillator (ICD) or cardiac resynchronization therapy device (CRT-D) was implanted during follow-up. Peak VO 2, percentage of predicted peak VO 2, VE/VCO 2 slope, OUES and POUE were analyzed. OUES was calculated using the formula VO 2 (l/min) = OUES (log 10VE) + b. POUE was calculated as pVO 2 (l/min) / log 10peakVE (l/min). Correlation coefficients between the studied parameters were obtained. The prognosis of each variable adjusted for age was evaluated through Cox proportional hazard models and R2 percent (R2%) and V index (V6) were used as measures of the predictive accuracy of events of each of these variables. Receiver operating characteristic (ROC) curves from logistic regression models were used to determine the cut-offs for OUES and POUE. Results pVO 2: 20.5 ± 5.9; percentage of predicted peak VO 2: 68.6 ± 18.2; VE/VCO 2 slope: 30.6 ± 8.3; OUES: 1.85 ± 0.61; POUE: 0.88 ± 0.27. During a mean follow-up of 33.1 ± 14.8 months, 45 (21.8%) patients died, 10 (4.9%) underwent urgent heart transplantation and in three patients (1.5%) a left ventricular assist device was implanted. All variables proved to be independent predictors of this combined event; however, VE/VCO2 slope was most strongly associated with events (HR 11.14). In this population, POUE was associated with a higher risk of events than OUES (HR 9.61 vs. 7.01), and was also a better predictor of events (R2: 28.91 vs. 22.37). Conclusion POUE was more strongly associated with death, urgent heart transplantation and implantation of a left ventricular assist device and proved to be a better predictor of events than OUES. These results suggest that this new parameter can increase the prognostic value of CPET in patients with CHF.

Prognostic value of a new cardiopulmonary exercise testing parameter in chronic heart failure: oxygen uptake efficiency at peak exercise — comparison with oxygen uptake efficiency slope

IntroductionA growing body of evidence shows the prognostic value of oxygen uptake efficiency slope (OUES), a cardiopulmonary exercise test (CPET) parameter derived from the logarithmic relationship between O2 consumption (VO2) and minute ventilation (VE) in patients with chronic heart failure (CHF). ObjectiveTo evaluate the prognostic value of a new CPET parameter — peak oxygen uptake efficiency (POUE) — and to compare it with OUES in patients with CHF. MethodsWe prospectively studied 206 consecutive patients with stable CHF due to dilated cardiomyopathy — 153 male, aged 53.3±13.0 years, 35.4% of ischemic etiology, left ventricular ejection fraction 27.7±8.0%, 81.1% in sinus rhythm, 97.1% receiving ACE-Is or ARBs, 78.2% beta-blockers and 60.2% spironolactone — who performed a first maximal symptom-limited treadmill CPET, using the modified Bruce protocol. In 33% of patients an cardioverter-defibrillator (ICD) or cardiac resynchronization therapy device (CRT-D) was implanted during follow-up.Peak VO2, percentage of predicted peak VO2, VE/VCO2 slope, OUES and POUE were analyzed. OUES was calculated using the formula VO2 (l/min) = OUES (log10VE) + b. POUE was calculated as pVO2 (l/min) / log10peakVE (l/min). Correlation coefficients between the studied parameters were obtained. The prognosis of each variable adjusted for age was evaluated through Cox proportional hazard models and R2 percent (R2%) and V index (V6) were used as measures of the predictive accuracy of events of each of these variables. Receiver operating characteristic (ROC) curves from logistic regression models were used to determine the cut-offs for OUES and POUE. ResultspVO2: 20.5±5.9; percentage of predicted peak VO2: 68.6±18.2; VE/VCO2 slope: 30.6±8.3; OUES: 1.85±0.61; POUE: 0.88±0.27. During a mean follow-up of 33.1±14.8 months, 45 (21.8%) patients died, 10 (4.9%) underwent urgent heart transplantation and in three patients (1.5%) a left ventricular assist device was implanted. All variables proved to be independent predictors of this combined event; however, VE/VCO2 slope was most strongly associated with events (HR 11.14). In this population, POUE was associated with a higher risk of events than OUES (HR 9.61 vs. 7.01), and was also a better predictor of events (R2: 28.91 vs. 22.37). ConclusionPOUE was more strongly associated with death, urgent heart transplantation and implantation of a left ventricular assist device and proved to be a better predictor of events than OUES. These results suggest that this new parameter can increase the prognostic value of CPET in patients with CHF.

Thoracic fluid content — a possible determinant of ventilatory efficiency in patients with heart failure

Ventilatory efficiency, evaluated by cardiopulmonary exercise testing (CPET), has considerable prognostic value in patients with chronic heart failure (CHF) due to left ventricular systolic dysfunction (LVSD). Its determinants nevertheless remain controversial. AimTo investigate the possible correlation between parameters of ventilatory efficiency obtained by CPET and thoracic fluid content (TFC), assessed by thoracic electrical bioimpedance (TEB), in patients with CHF due to LVSD. MethodsWe studied 120 patients with LVSD and CHF, referred to our laboratory for CPET: 76% male, age 52.1±12.1 years, 37% of ischemic etiology, left ventricular ejection fraction 27.6±7.9%, 83% in sinus rhythm, 96% receiving ACEIs and/or ARBs and 79% beta-blockers, and 20% treated with a cardiac resynchronization device. TEB studies were performed after 15 minutes of rest, prior to symptom-limited treadmill CPET, using the modified Bruce protocol. CPET-derived peak oxygen consumption (pVO2), the slope of the relationship between minute ventilation (VE) and carbon dioxide production (VCO2), VE/VCO2 at the anaerobic threshold (AT), and TFC assessed by TEB were considered for analysis. ResultsTFC ranged between 20.6 and 45.8kOhm−1, mean 32.2, SD=5.7, median 32.7, pVO2 8.9–40.6ml/kg/min, mean 21.0, SD 6.2, median 20.2, VE/VCO2 slope 19.8–60.7, mean 30.7, SD 7.9, median 29.1 and VE/VCO2 at AT 21–62, mean 33.1, SD 7.5, median 31.5. By linear regression, TFC did not correlate with pVO2 (r=0.05, p=0.58), but showed correlation with parameters of ventilatory efficiency: r=0.20, p=0.032, r2=0.04 for VE/VCO2 slope and r=0.25, p=0.009, r2=0.06 for VE/VCO2 at AT. ConclusionTFC correlates with CPET parameters of ventilatory efficiency in patients with CHF due to LVSD, suggesting that it may be one of its determinants.

Fluido torácico total – Um possível determinante da eficácia ventilatória em doentes com insuficiência cardíaca

Ventilatory efficiency, evaluated by cardiopulmonary exercise testing (CPET), has considerable prognostic value in patients with chronic heart failure (CHF) due to left ventricular systolic dysfunction (LVSD). Its determinants nevertheless remain controversial. Aim To investigate the possible correlation between parameters of ventilatory efficiency obtained by CPET and thoracic fluid content (TFC), assessed by thoracic electrical bioimpedance (TEB), in patients with CHF due to LVSD. Methods We studied 120 patients with LVSD and CHF, referred to our laboratory for CPET: 76% male, age 52.1±12.1 years, 37% of ischemic etiology, left ventricular ejection fraction 27.6±7.9%, 83% in sinus rhythm, 96% receiving ACEIs and/or ARBs and 79% beta-blockers, and 20% treated with a cardiac resynchronization device. TEB studies were performed after 15 minutes of rest, prior to symptom-limited treadmill CPET, using the modified Bruce protocol. CPET-derived peak oxygen consumption (pVO 2), the slope of the relationship between minute ventilation (VE) and carbon dioxide production (VCO 2), VE/VCO 2 at the anaerobic threshold (AT), and TFC assessed by TEB were considered for analysis. Results TFC ranged between 20.6 and 45.8 kOhm−1, mean 32.2, SD = 5.7, median 32.7, pVO 2 8.9–40.6 ml/kg/min, mean 21.0, SD 6.2, median 20.2, VE/VCO 2 slope 19.8–60.7, mean 30.7, SD 7.9, median 29.1 and VE/VCO 2 at AT 21–62, mean 33.1, SD 7.5, median 31.5. By linear regression, TFC did not correlate with pVO 2 (r = 0.05, p = 0.58), but showed correlation with parameters of ventilatory efficiency: r = 0.20, p = 0.032, r 2 = 0.04 for VE/VCO 2 slope and r = 0.25, p = 0.009, r 2 = 0.06 for VE/VCO 2 at AT. Conclusion TFC correlates with CPET parameters of ventilatory efficiency in patients with CHF due to LVSD, suggesting that it may be one of its determinants.

173 A generic method to assess the adequacy of individual maternal cardiac reserve to tolerate the demands of pregnancy and labour

IntroductionClinicians often feel apprehensive when managing pregnant patients with heart disease. To complement current evaluation, we have developed a new method of directly assessing the individual patient's cardiac functional reserve...

Maintaining physical fitness of patients with chronic heart failure: a randomized controlled trial

We aimed to compare the effects of three different training advices, after 1 year, following a 6 months supervised cardiac rehabilitation period in patients with chronic heart failure (CHF). Sixty-nine CHF patients were randomized, at the end of their rehabilitation period, either to usual care (UC) or to UC and controlled home training (HT), prolonged supervised training (ST) or preferred training (PT). Treadmill cardio-pulmonary exercise testing was performed before rehabilitation, postrehabilitation and thereafter at 3-month intervals during the 1-year follow-up. submaximal exercise capacity [Oxygen consumption and workload at the respiratory compensation point (VO2RCP, WattRCP) and submaximal workload (SMW) efficiency (SMW/HR) at 70% of the initial maximal workload] was chosen as a primary endpoint, because health status in CHF patients depends largely on their ability to perform activities at a submaximal level. After 6 months of rehabilitation, the four groups (UC, HT, ST and PT) were comparable with regard to cardiac rehabilitation-derived benefit, both at the submaximal and maximal level. Although exercise capacity during follow-up declined in both UC and HT patients, ST and especially PT patients maintained and even improved VO2peak and VO2RCP. However, only PT patients managed to maintain or even increase submaximal (WattRCP and SMW/HR ratio) workload (P=0.045 and <0.0001 for interaction, respectively). Ventilatory-derived prognostic markers during treadmill cardio pulmonary exercise testing evolved similarly in the four subgroups. This study suggests that engagement in physical training of their own choice (PT), might be the optimal training modality for maintaining physical capacity in CHF patients.

Effect of Acute β-blocker Withholding on Ventilatory Efficiency in Patients With Advanced Chronic Heart Failure

Background This is the first study to examine the effect of acute (24-hour) β-blocker withholding on ventilatory efficiency in patients with advanced chronic heart failure (CHF) during maximal incremental treadmill cardiopulmonary exercise test. Methods and Results Seventeen CHF patients were studied either 3 hours after administration of β-blocker (BB ON) or 27 hours after the last β-blocker ingestion (BB OFF). The ventilatory efficiency was measured via the slope of the linear relationship between ventilation (V′ E) and carbon dioxide production (V′CO 2) (ie, V′ E/V′CO 2 slope). Measurements were also made at rest, anaerobic threshold (AT), maximal end-tidal pressure for carbon dioxide (P ETCO 2max), respiratory compensation point (RC), and peak exercise. Compared with BB ON, the V′ E/V′CO 2 slope was significantly increased during BB OFF (30.8 ± 7.4 vs. 29.1 ± 5.4, P = .04). At peak exercise, oxygen uptake (V′O 2, 16.0 ± 2.7 vs. 15.6 ± 2.8 mL·kg·min) and V′CO 2 (1458 ± 459 vs. 1414 ± 429 mL/min) were not different between the 2 conditions, whereas V′ E was higher during BB OFF (49.5 ± 10.7 vs. 46.1 ± 9.6 L/min, P = .04). No differences were noted at AT and RC in V′O 2, V′CO 2, V′ E, V′ E/V′O 2, and V′ E/V′CO 2 ratios during the 2 conditions. At P ETCO 2max, used to noninvasively estimate the CO 2 set point, V′ E was higher (33.9 ± 7.6 vs. 31.7 ± 7.3 L/min, P = .002) and P ETCO 2 was lower (37.4 ± 4.8 vs. 38.5 ± 4.0 mm Hg, P = .03), whereas V′CO 2 was unchanged (1079 ± 340 vs. 1050 ± 322 mL/min) during BB OFF. Conclusion Acute β-blocker withholding resulted in decreased ventilatory efficiency mostly from an increase of V′CO 2-independent regulation of V′ E and less likely from a change in ventilation/perfusion mismatching.

Is the 6-min walking test a sub-maximal exercise test in heart failure patients?

The study by Jehn et al. (2009) is interesting and adds important information to the discussion about the 6-min walking test as a sub-maximal exercise test in heart failure patients. The current study compared the cardiorespiratory responses during a 6-min walking test performed in a corridor with those during a maximal cycle ergometer exercise test in patients with three different stages of heart failure based on the peak oxygen uptake (VO2peak): group 1: [25.2 ml/kg per minute; group 2: between 17.5 and 25.2 ml/kg per minute and group 3: \17.5 ml/kg per minute. The authors concluded that heart failure patients with a VO2peak \17.5 ml/kg per minute reached higher levels of respiratory response during the 6-min walking test compared with patients with a VO2peak [25.2 ml/kg per minute. These data would benefit from being expressed relative to the responses to incremental exercise on the treadmill, rather than the cycle ergometer; i.e., treadmill walking being more closely related to walking test performance. In addition, the authors could have used the prognostic cutoff point for VO2peak in heart failure patients to divide the groups: 14 ml/kg per minute (Mehra et al. 2006), or more recently 12.5 ml/kg per minute (Guimaraes et al. 2009) instead of the 17.5 ml/kg per minute criterion. The discussion on the nature of the sub-maximal 6-min walking test is not new. Guimaraes et al. 2002 evaluated the cardiorespiratory response of 12 male heart failure patients (New York Heart Association functional class III and 15.4 ml/kg per minute) in a treadmill cardiopulmonary exercise test and in a 6-min walking test. The tests showed that the respiratory exchange ratio at end exercise was of the order of 1.0 (mean of 1.06). The respiratory exchange ratio during the 6-min walking test represented 94% of the peak respiratory exchange ratio reached in the cardiopulmonary exercise test. It is known that peak respiratory exchange ratio above 1.05 represents an effort near to the maximum in heart failure patients (Carvalho et al. 2009a, b). The study by Guimaraes contests, for the first time, the sub-maximal status of the classical 6-min walking test and proposes a new method to perform this test using the Borg Scale between ‘‘relatively easy’’ and ‘‘slightly tiring’’. This new method assures the 6-min walking test as sub-maximal. The Borg Scale is recognised as an important tool of self-monitoring and self-regulation of the exercise (Carvalho et al. 2009a, b). A second study (Guimaraes et al. 2008) showed that the 6-min walking test using the Borg Scale in heart failure patients is reproducible and once more that this methodology assures the 6-min walking test as sub-maximal. Thus, the study by Jehn et al. provided new perspectives for the evaluation of the 6-min walking test by taking into account the different cardiorespiratory responses on the different functional status of the heart failure patients.

The relationship between heart rate and oxygen consumption in heart transplant recipients during a cardiopulmonary exercise test

In healthy subjects, the percentage of heart rate reserve (%HRR) versus the percentage of oxygen consumption reserve (%VO(2)R) is the closest relationship between heart rate and VO(2) and it seems also to be true to heart failure patients only if they are under optimized beta-blocker therapy. To evaluate the closest relationship between heart rate and VO(2) (%peak heart rate versus %peak VO(2); %HRR versus %VO(2)R or absolute heart rate versus absolute VO(2)) in heart transplant recipients during a treadmill cardiopulmonary exercise test. A total of 19 sedentary heart transplant recipients (5.4 ± 3.3 years after transplant) in a stable condition (for, at least, 3 months), were recruited to perform a cardiopulmonary exercise test. The relationship between %HRR-%VO(2)R, %peak heart rate versus %peak VO(2) and absolute heart rate versus absolute VO(2) were tested. The strongest relationship was found between %HRR-%VO(2)R (r = 0.95, p<0.0001), followed by %peak heart rate versus %peak VO(2) (r = 0.91, p<0.0001) and absolute heart rate versus absolute VO(2) (r = 0.67, p<0.0001). The mean regression line did not coincide with the line of identity in any group (p<0.0001 for all groups). The %HRR versus %VO(2)R showed the closest relationship followed by %peak heart rate versus %peak VO(2) and absolute heart rate versus absolute VO(2). Despite this, the perfect reliability of the heart rate versus VO(2) was not found.

Heart rate dynamic during an exercise test in heart failure patients with different sensibilities of the carvedilol therapy: Heart rate dynamic during exercise test

Background Some trials suggest that the titration of Carvedilol is based on rest heart rate from 50 to 60 bpm and a target daily dose of 50 mg/day. Aim To evaluate the heart rate dynamic in heart failure patients with different sensibilities of the Carvedilol therapy during an exercise test. Methods Patients were divided into four groups and submitted a treadmill cardiopulmonary exercise test: heart rate > 60 bpm and Carvedilol < than 50 mg/day (30 patients) (non-optimized group); heart rate > 60 bpm and Carvedilol > = 50 mg/day (19 patients) (non-optimized low-sensibility); heart rate between 50 and 60 bpm and Carvedilol > = 50 mg/day (16 patients) (optimized); heart rate between 50 and 60 bpm and Carvedilol < 50 mg/day (10 patients) (optimized high-sensible group). Results The heart rate peak and the percentage of the peak heart rate in relation with the maximum heart rate predicted for age during the cardiopulmonary exercise test were the same between the non-optimized (128 ± 13, bpm; 74 ± 7%) and non-optimized low-sensibility (136 ± 20, bpm; 78 ± 8%) groups, and between the optimized (105 ± 25, bpm; 60 ± 13%) and optimized high-sensible (108 ± 16, bpm; 62 ± 8%) groups. The heart rate reserve was the same. Conclusion The heart rate dynamic was almost the same between groups with rest heart rate > 60 bpm and between groups < 60 bpm, independently of the Carvedilol dose. Based on these findings, we propose a new method to titrate carvedilol therapy by the cardiopulmonary exercise test.