Elsevier

American Heart Journal

Volume 149, Issue 1, January 2005, Pages 175-180
American Heart Journal

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

https://doi.org/10.1016/j.ahj.2004.07.004Get rights and content

Abstract

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.

Section snippets

Study population

The study population consisted of 80 consecutive patients who visited the outpatient clinic between January and July 2003 prior to their enrollment in a cardiac rehabilitation program. All patients performed a maximal cardiopulmonary exercise test with a respiratory exchange ratio (RERmax) >1.10 and were free of exercise-limiting comorbidities, such as cerebrovascular disease, musculoskeletal impairment, or vascular disease of the lower extremities. Patients were divided into 2 groups according

Baseline clinical and demographic characteristics

Characteristics of patients with and without LV dysfunction are detailed in Table I. By definition group A patients had a lower EF (P < .01) and a higher New York Heart Association (NYHA) class (P < .01). No difference in age, body mass index, or sex was noted between the groups. The incidence of ischemic heart disease was significantly higher in group B patients (P < .01). No difference was noted between both groups in the percentage of patients taking angiotensin-converting enzyme inhibitors

Discussion

Although peakVO2 is considered as a gold standard for stratification of heart failure patients, its use is limited by conditioning status, patient motivation, skeletal muscle structure, pulmonary function, and hemoglobin level. Because of all these limitations, some patients will not achieve their anaerobic threshold during exercise and peakVO2 can not be accurately assessed. To overcome these limitations, submaximal metabolic parameters have been proposed as surrogates to estimate exercise

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