Oxygen uptake efficiency slope, a new submaximal parameter in evaluating exercise capacity in chronic heart failure patients

Background

The oxygen uptake efficiency slope (OUES) is a new submaximal parameter which objectively predicts the maximal exercise capacity in children and healthy subjects. However, the usefulness of OUES in adult patients with and without advanced heart failure remains undetermined. The present study investigates the stability and the usefulness of OUES in adult cardiac patients with and without heart failure.

Methods

Forty-five patients with advanced heart failure (group A) and 35 patients with ischemic heart disease but normal left ventricular ejection fraction (group B) performed a maximal exercise test. PeakVO₂ and percentage of predicted peakVO₂ were markers of maximal exercise capacity, whereas OUES, ventilatory anaerobic threshold (VAT), and slope VE/VCO₂ were calculated as parameters of submaximal exercise.

Results

Group A patients had lower peakVO₂ (P < .001), lower percentage of predicted peakVO₂ (P = .001), lower VAT (P < .05), steeper slope VE/VCO₂ (P < .001), and lower OUES (P < .02). Within group A, significant differences were found for VAT, slope VE/VCO₂, and OUES (all P < .01) between patients with peakVO₂ above and below 14 mL O₂/kg/min. Of all the submaximal parameters, VAT correlated best with peakVO₂ (r =.814, P < .01) followed by OUES/kg (r = .781, P < .01), and slope VE/VCO₂ (r = −.492, P < .001). However, VAT could not be determined in 18 (23%) patients.

Conclusions

OUES remains stable over the entire exercise duration and is significantly correlated with peakVO₂ in adult cardiac patients with and without impaired LVEF. Therefore, OUES could be helpful to assess exercise performance in advanced heart failure patients unable to perform a maximal exercise test. Further studies are needed to confirm our hypothesis.     

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 cardioverterdefibrillator (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.     

The oxygen uptake efficiency slope and its value in the assessment of cardiorespiratory functional reserve

Oxygen uptake efficiency slope is a new index of cardiorespiratory functional reserve derived from the logarithmic relation between oxygen uptake (VO(2)) and minute ventilation during incremental exercise. The oxygen uptake efficiency slope represents how effectively oxygen is extracted and taken into the body from the air, and then ventilated. The physiologic backgrounds of the index are based on: 1) the development of metabolic acidosis that is controlled by the distribution of blood to the skeletal muscles; 2) the physiologic dead space that is affected by the perfusion to the lungs; and 3) arterial carbon dioxide partial pressure. One of the greatest advantages of the oxygen uptake efficiency slope is that it can be calculated by exercise data of submaximal levels. Another advantage is that it is mathematically determined from a set of gas analysis data and, therefore, is completely an objective measurement. Moreover, the oxygen uptake efficiency slope is shown to be highly reproducible. Clinical applications of the oxygen uptake efficiency slope have been reported initially from a population of pediatric patients with heart disease, then from adult patients with chronic heart failure, and finally from elite endurance athletes. Further applications are expected with the use of this sophisticated index. (c)2000 by CHF, Inc.     

Oxygen uptake efficiency slope as monitoring tool for physical training in chronic hemodialysis patients

The purpose of this study was to clarify the utility of oxygen uptake efficiency slope (OUES) as a monitoring tool, and to investigate the effects of physical training in chronic hemodialysis (HD) patients. Seventeen patients (Trained Group) received physical training 2-3 times per week for 20 weeks at the intervals between exercise tests. Patients underwent a combination training of bicycle ergometry, walking and jogging for 30 min duration. The intensity of physical training was adjusted to maintain the exercising heart rate at between 50 and 60% of the peak heart rate. Twelve patients (Control Group) lived without physical training throughout the 20 weeks. Both the Groups received the symptom limited exercise tests before and after the 20 week physical training. Minute ventilation (VE), carbon dioxide output (VCO2) and oxygen uptake (VO2) were continuously measured during the exercise tests. Oxygen uptake efficiency slope was derived from the logarithmic relation between VO2 and VE during an incremental exercise test. In the Trained Group, OUES after physical training (30.1 +/- 5.8) was significantly (P < 0.01) higher than that before physical training (25.2 +/- 2.6), while in the Control Group, OUES did not change in this study period of 20 weeks. In the Trained Group, changes in OUES correlated with those in the maximum oxygen uptake (r = 0.78, P < 0.001) and the anaerobic threshold (r = 0.61, P < 0.01). It was suggested that OUES was applicable as a monitoring tool for cardiorespiratory functional reserve during physical training in HD patients.     

Which is the best parameter of submaximal cardiopulmonary exercise testing?

I read with great interest the study by Davies et al.¹in which it was reported that the oxygen uptake efficiency slope(OUES) is a determinant of survival in patients with chronicheart failure (CHF). Indeed, the essential point is that itis     

The effect of aging on submaximal exercise performance and recovery

The upward drift of gas exchange variables during 70% maximal exercise and recovery half-times in aged and young subjects of equivalent age-predicted aerobic capacity was measured. In the aged subjects, upward drift of VE, VO2, and HR was reduced compared with the young group. The recovery of VE, VCO2, and VO2 was slowed in the aged. However, at 10 minutes post-exercise, VCO2, VO2, and HR had returned to similar relative values for both groups; in the young subjects VE remained elevated at the end of recovery. The reduced upward drift of gas exchange variables and HR during exercise in aged subjects is consistent with an attenuated response of glycogenolysis and lactate production to adrenergic stimulation and/or to selective loss of type II skeletal muscle fibers. The slowed recovery of VE, VCO2, and VO2 in elderly persons is consistent with age-related reduced CO2 chemosensitivity, delaying elimination of the exercise-induced CO2 load.     

Response of the oxygen uptake efficiency slope to exercise training in patients with chronic heart failure

BACKGROUND: The oxygen uptake efficiency slope (OUES) is a new exercise parameter that provides prognostic power in patients with CHF. Little is known about the effects of exercise training (ET) on OUES. AIM: To describe the response of OUES to 6 months of ET in CHF patients and compare its evolution to that of other exercise variables. METHODS: 35 patients with CHF (NYHA II-III, age 54+/-9y, LVEF 31+/-10%) performed 3 maximal exercise tests, i.e. at the start, middle and end of a 6 month ET program. OUES, PeakVO(2), ventilatory anaerobic threshold (VAT) and slope VE/VCO(2) were determined. RESULTS: OUES, peakVO(2), VAT, slope VE/VCO(2), peak Watt, 6MWT and NYHA-class improved during the first part of the ET period (p<0.05). Only VAT, peak Watt and 6MWT continued to improve during the second part of the ET period (p<0.05) Improvements in OUES correlated better with improvements in peakVO(2) (r=0.77, p<0.001), than changes in other prognostic variables. DISCUSSION: OUES improves significantly after 6 months of ET. Changes in peakVO(2) correlate best with changes in OUES. OUES is sensitive to ET and can be used to evaluate the progression of exercise capacity in CHF patients.     

Thallium-201 myocardial imaging during maximal and submaximal exercise: Comparison of submaximal exercise with propranolol

Propranolol is an effective drug for patients with angina and has been shown to favorably alter exercise ejection fraction and myocardial perfusion images in patients with coronary disease. A characteristic effect of propranolol is reduction in exercise heart rate (HR). Twenty men with coronary disease (10 with prior infarction), angina-limited exercise tests, abnormal myocardial blood flow distribution images (MBFDI) (²⁰¹thallium) during exercise, and normal resting ejection fractions underwent treadmill exercise testing with imaging on three occasions. Control maximal exercise was performed initially with measurement of MBFDI. Propranolol, 40 mg by mouth four times a day, was administered for a week with exercise repeated to the same workload. A third study, with men off propranolol, was undertaken with exercise continued only to the HR obtained while the men were taking propranolol (submaximal exercise). All men had improvement in MBFDI while receiving propranolol (men without infarction + 780 ± 88 [average ± SEM] normalized count rate difference between control and propranolol; men with infarction +724 ± 73 normalized counts). Greater count differences were noted when control exercise and HR-controlled, submaximal exercise MBFDI were compared with a greater difference in men with infarction (+1094 ± 89 normalized counts) than for men without infarction (+896 ± 88 normalized counts). Results suggest that propranolol improves MBFDI during exercise in men with angina, but that submaximal exercise results in more normal MBFDI than does propranolol for exercise to the same HR.     

The influence of body mass index on the oxygen uptake efficiency slope in patients with heart failure

There does not appear to be a relationship between peak oxygen consumption (VO(2)) and body mass index (BMI) in patients with heart failure (HF). We assessed the hypothesis that BMI and the oxygen uptake efficiency slope (OUES) would be related. Three hundred and thirty-seven HF patients (280 male/57 female, mean age: 56.5+/-14.1 years, resting left ventricular ejection fraction: 35.1+/-14.2%, BMI: 29.3+/-6.2 kg/m(2)) underwent cardiopulmonary exercise testing where peak VO(2) and the OUES (VO(2)=a log(10)VE+b, units: L/min) were determined. Pearson product moment correlation analysis revealed that the correlation between BMI and the OUES was significant (r=0.32, p<0.001). Furthermore, the OUES was prognostically significant in normal weight (optimal threshold: 1.2, hazard ratio: 3.7, 95% confidence interval: 1.4-9.9, p=0.01), overweight (optimal threshold: 1.5, hazard ratio: 3.9, 95% confidence interval: 1.3-11.1, p=0.01) and obese (optimal threshold: 1.7, hazard ratio: 4.1, 95% confidence interval: 1.4-12.8, p=0.01) subgroups. The OUES appears to improve with body weight in patients with HF. Furthermore, the OUES appears to be a significant prognostic marker irrespective of BMI although the optimal threshold value may differ according to body weight.     

终末期慢性心力衰竭患者运动中摄氧通气效率指标的临床应用

目的 评估心肺运动试验(CPET)摄氧通气效率指标摄氧效率平台(OUEP)、摄氧效率斜率(OUES)、通气量((V) E)/二氧化碳排出量((V)CO2)最低值和(V)E/(V)CO2斜率在监测终末期慢性心力衰竭(CHF)患者心功能和血液动力学状态中的意义.方法 入选2012年10月至2013年9月阜外心血管病医院住院行心脏移植的CHF患者26例.收集临床资料和CPET参数.在行CPET的2周内,进行超声心动图和Swan-Ganz导管检查监测血液动力学参数,并对CPET中摄氧通气效率指标与超声心动图参数和血液动力学参数进行相关性分析.结果 CPET摄氧效率指标OUEP、OUES与传统指标峰值氧耗量(峰值(V)O2)之间相关性好(r=0.535、P＜0.01;r=0.840、P＜0.001).在终末期CHF患者中OUEP相对峰值(V)O2的变化斜率约为32,而OUES相对峰值(V)O2的变化斜率仅约为2,两者相差约16倍,OUEP改变比OUES、峰值(V)O2更加敏感和显著(P＜0.05).OUEP、峰值(V)O2测定值占预测值百分比(％ pred)、(V)E/(V)CO2斜率和(V)E/(V)CO2最低值与无创血液动力学参数峰值心输出量(r =0.535,P＜0.01; r=0.652,P＜0.001; r=-0.640,P＜0.001; r=-0.606,P=0.001)和峰值心脏指数(r=0.556,P＜0.01;r=0.772,P＜0.001; r=-0.641,P＜0.001;r=-0.620,P＜0.001)均显著相关,但与静息状态下有创血液动力学参数心输出量和心脏指数不相关(P＞0.05).峰值(V)O2(％pred)和(V)E/(V)CO2斜率与肺动脉收缩压(r=-0.424,P＜0.05; r=0.509,P＜0.01)和平均肺动脉压力(r=-0.479,P＜0.05;r=0.405,P＜0.05)均显著相关,峰值(V)O2(％pred)还与肺毛细血管楔压显著相关(r=-0.415,P＜0.05),(V)E/(V)CO2斜率与肺血管阻力亦呈显著相关(r=0.429,P＜0.05).结论 CPET摄氧通气效率指标OUEP,可配合传统指标峰值(V)O2、(V)E/(V)CO2最低值、(V)E/(V)CO2斜率等,对CHF患者心功能和血液动力学状态的变化进行更好地监测和评估,以指导终末期CHF患者的临床管理.     

Instantaneous hyperemic flow-versus-pressure slope index. Microsphere validation of an alternative to measures of coronary reserve.

BACKGROUND. The instantaneous hyperemic flow-versus-pressure (i-HFVP) slope index is a new method of assessing maximal coronary conductance and can be used as an alternative to conventional measures of coronary reserve. The i-HFVP slope index is determined by measuring the slope of the linear diastolic segment of the relation between instantaneous aortic pressure and hyperemic coronary flow. METHODS AND RESULTS. To validate the i-HFVP slope index as a measure of maximal coronary conductance, we compared this method with a microsphere-derived measurement of maximal coronary conductance (m-HFVP slope index) by determining the slope of the least-squares regression line of the data points for coronary flow during maximal hyperemia and four or five steady-state alterations of aortic pressure in 43 dogs (open-chest, anesthetized preparations) with or without coronary stenoses. The i-HFVP slope index demonstrated no dependence on heart rate, left ventricular end-diastolic pressure, or mean aortic pressure and was highly reproducible within the groups studied (intraclass correlation coefficient, 0.86 for normal arteries, 0.87 for stenotic arteries, and 0.93 for combined groups; for all coefficients, p less than 0.001). The i-HFVP slope index was significantly decreased in the presence of a stenosis (10.3 +/- 3.9 for normal arteries versus 3.6 +/- 1.6 for stenotic arteries, p less than 0.001) as was the transmural m-HFVP slope index (8.9 +/- 4.6 for normal arteries versus 5.3 +/- 3.1, p less than 0.01). Of special importance, the i-HFVP slope index measurement for normal arteries was not significantly different from the transmural and subendocardial m-HFVP slope index measurements (10.3 +/- 3.9 versus 8.9 +/- 4.6 and 9.2 +/- 5.7, respectively). For stenotic arteries, the i-HFVP slope index measurement was also not significantly different from the transmural and subendocardial m-HFVP slope index measurements (3.6 +/- 1.6 versus 5.3 +/- 3.1 and 4.1 +/- 2.3, respectively). The i-HFVP slope index correlated best with subendocardial m-HFVP slope index measurements (correlation coefficient, 0.57; p less than 0.001). When the 95% confidence intervals for the transmural (or subendocardial) m-HFVP slope index in normal arteries were compared with the i-HFVP slope index values, the latter demonstrated a systematic trend to overestimate the m-HFVP slope index. In the presence of a stenosis, this effect was minimized, and the slope values were nearly identical. CONCLUSIONS. The i-HFVP slope index correlates most closely with subendocardial coronary conductance; the index is a hemodynamically independent measure of coronary reserve that is reproducible over a broad range of aortic pressures; and the methodology is applicable to an intact circulation in experimental preparations and may with future developments also prove useful in humans.     

The validation of oxygen uptake efficiency slope in patients with stroke

To evaluate the real aerobic capacity is difficult due to impaired limbs function in stroke patients. Oxygen uptake efficiency slope (OUES) could represent the aerobic capacity in submaximal exercise test. Hence, we designed this observational study to investigate the application of the OUES for evaluating aerobic capacity in these patients.Thirty-seven stroke patients were classified into 2 groups according to their Brunnstrom stage of affected lower limbs. Patients underwent cardiopulmonary exercise testing to assess cardiorespiratory fitness. Minute ventilation and oxygen consumption were measured, and OUES was calculated, compared with healthy reference values, and correlated with the peak oxygen consumption. The predictive validity of submaximal OUES was derived.Study participants’ OUES (median 566.2 [IQR, 470.0-711.6]) was 60% of healthy reference values and correlated positively with the peak oxygen consumption (r = 0.835) (P < .01). The predictive validity of oxygen uptake efficiency slope at 50% of maximal exercise duration (OUES₅₀) and oxygen uptake efficiency slope at 75% of maximal exercise duration (OUES₇₅) for oxygen uptake efficiency slope at 100% of maximal exercise duration (OUES₁₀₀) was 0.877 and 0.973, respectively (P < .01). The OUES₅₀, OUES₇₅, and OUES₁₀₀ groups were not significantly different; agreement of submaximal and maximal OUES values was strong.OUES is a valuable submaximal index for evaluating cardiorespiratory fitness in stroke patients. Moderate-to-high concurrent validity of this parameter with peak oxygen consumption and the high predictive validity of OUES₅₀ and OUES₇₅ for OUES₁₀₀ suggest maximal exercise testing in stroke patients who cannot reach maximal exercise is unnecessary.     

Mitral valve reserve in double-orifice technique: an exercise echocardiographic study

BACKGROUND AND AIM OF THE STUDY: The edge-to-edge technique is used to restore valvular competence in mitral insufficiency. The efficacy of the method is under debate due to the potential for creating functional mitral stenosis. An exercise echocardiographic study was carried out to investigate valve function and hemodynamics in patients who had undergone double-orifice mitral valve repair. METHODS: Thirty patients (mean age 49.1 +/- 12.7 years) with previous double-orifice mitral valve repair underwent exercise echocardiography (10 W/min). An annular prosthesis was present in 28 patients (93%). The mean and maximum mitral valve gradient, planimetric valve area, stroke volume, systolic pulmonary artery pressure, heart rate and systolic blood pressure were measured at baseline and at peak stress. RESULTS: At peak stress, heart rate (77.7 +/- 12.2 versus 118.6 +/- 26.0 beats/min, p < 0.00001), systolic blood pressure (124.1 +/- 10.9 versus 146.6 +/- 22.8 mmHg, p < 0.00001) and stroke volume (78.0 +/- 10.2 versus 97.0 +/- 15.1 ml, p < 0.00001) were significantly increased, showing a physiological behavior of the mitral valve. The mean mitral valve gradient (2.8 +/- 1.3 versus 4.6 +/- 1.9 mmHg, p < 0.00001), maximum mitral valve gradient (6.4 +/- 2.8 versus 10.5 +/- 4.6 mmHg, p < 0.00002) and systolic pulmonary artery pressure (22.8 +/- 6.1 versus 28.2 +/- 9.9 mmHg, p < 0.001) were increased, but not to pathologic levels. Planimetric valve area increased significantly (3.2 +/- 0.6 versus 4.3 +/- 0.7 cm2, p < 0.00001). A significant negative linear correlation was found between the relative change in mitral valve area and planimetric valve area at rest (r = -0.51, p < 0.05). CONCLUSION: The double-orifice repair, even with concomitant ring annuloplasty, does not cause mitral valve obstruction, either at baseline or during physical exercise, and does not affect valve hemodynamic and valve reserve.     

Value of Doppler index combining systolic and diastolic myocardial performance in predicting cardiopulmonary exercise capacity in patients with congestive heart failure: effects of dobutamine

STUDY OBJECTIVE: Doppler-derived myocardial performance index (MPI), a measure of combined systolic and diastolic myocardial performance, was assessed at rest and after low-dose dobutamine administration in patients with idiopathic or ischemic dilated cardiomyopathy. MPI also was correlated with other conventional echocardiographic indexes of left ventricular (LV) function, and its ability to assess cardiopulmonary exercise capacity in those patients was investigated. SETTINGS: A tertiary-care, university heart failure clinic. PATIENTS: Forty-two consecutive patients (27 men; mean [+/- SD] age, 57 +/- 10 years) with heart failure (New York Heart Association [NYHA] class, II to IV) who had received echocardiographic diagnoses of dilated cardiomyopathy. Coronary angiography distinguished the cause of dilated cardiomyopathy. INTERVENTIONS: Low-dose IV dobutamine was infused after patients underwent a baseline echocardiographic study. All patients also underwent a cardiopulmonary exercise test using a modified Naughton protocol. RESULTS: Advanced NYHA class and restrictive LV filling pattern were associated with higher index values. A negative correlation was found between MPI and LV stroke volume, cardiac output, early filling/late filling velocity ratio, and late LV filling velocity, as well as oxygen uptake at peak exercise (r = -0.550; p < 0.001) and at the anaerobic threshold (r = -0.490; p = 0.002). Dobutamine administration produced an improvement in MPI, reducing its value and decreasing the isovolumic relaxation and contraction times. Stepwise regression analysis revealed that the rest index and the late LV filling velocity were the only independent predictors of cardiopulmonary exercise capacity. CONCLUSION: MPI correlates inversely with LV performance, reflects disease severity, and is a useful complimentary variable in the assessment of cardiopulmonary exercise performance in patients with heart failure.