Prediction of peak oxygen uptake from cycle exercise test work level in heart failure patients >/=65 years of age.

D and fatigue are 2 of the classic symptoms of chronic heart failure, particularly when they occur at low levels of activity.1 Exercise testing is often used for diagnostic and prognostic purposes with this population.2–5 Indeed, it is known that decreased peak oxygen uptake (VO2peak) is associated with symptoms6 and with mortality in patients with heart failure.7 Although measurement of VO2peak is desirable, it is often not feasible due to lack of necessary instrumentation and personnel. Thus, clinicians are usually left to quantify the patients’ exercise tolerance based on exercise test time.8 The obvious limitation to this latter approach is that it requires a standardized mode and protocol for testing. However, it is also possible to estimate VO2peak from exercise test workloads. Equations that provide estimations of VO2 have been developed from young, apparently healthy populations performing submaximal, steady-state exercise between 50 and 200 W.9–11 Patients with systolic and diastolic dysfunction have markedly lower VO2peak than age-matched controls,12,13 which would correspond to workloads ,200 W. There is no information available on the accuracy of these equations9,14 in patients with heart failure. This study evaluates the ability of these equations to predict VO2peak in elderly patients with heart failure. • • • Subjects in this study were among the 150 participants in a National Institutes of Health–funded clinical trial of elderly patients diagnosed with heart failure. A detailed explanation of the diagnostic criteria, patient selection, and testing procedures for that trial has been previously presented.15 Participants who only completed the 12.5-W stage (n 5 5) and those who did not complete at least 1 minute of exercise (n 5 20) at the peak stage were excluded from the data analysis. This left 125 subjects who were $65 years of age and were free from valvular disease as the primary etiology for heart failure, recent stroke, uncontrolled systemic hypertension, significant lung disease, and any other condition that would limit exercise performance. Subject classification criteria for systolic dysfunction was an ejection fraction #45% (n 5 50) and for diastolic dysfunction, an ejection fraction $50% (n 5 49). Twenty-six healthy participants without heart failure, who were also $65 years of age, served as controls. Subjects were familiarized with the testing environment and procedures during a screening visit. All exercise tests were performed on an electronically braked cycle ergometer (CPE 2000, MedGraphics, Minneapolis, Minnesota) following a protocol that began with a 2-minute warm-up at 12.5 W, and then proceeded with 3-minute stages of 25, 50, 75, 100, and 125 W. Tests were terminated when the subject complained of severe dyspnea or was unable to continue pedaling. During each test, continuous electrocardiographic and gas exchange monitoring was performed using the MedGraphics CPX/D system (Minneapolis, Minnesota). Expired gas analysis was performed on each breath and peak values for VO2 were derived by taking the highest average of 30 seconds obtained during the peak stage of exercise (VO2 was not measured in recovery). Estimations of VO2peak were derived from 2 different regression equations reported in the American College of Sports Medicine’s Guidelines for Exercise Testing and Prescription (GETP). The first {VO2 (ml z min ) 5 (kg z m z min z 2) 1 (weight [kg] z 3.5} (GETP5) has been in use for '20 years.9 The second {VO2 (mlz min) 5 (kg z m z min z 1.8) 1 (weight [kg] z 7)} (GETP6) is a revised prediction equation14 based on recent studies suggesting inaccuracies with GETP5.10,11 All statistical analyses were performed using the StatView 4.5 software (Abacus Concepts, Berkley, California). A 3 33 analysis of variance was used to analyze for differences between measured and the 2 predicted VO2peak values, and for an interactive effect between patient groups. Significant F values were followed up with Scheffe’s post hoc tests. The criterion for significance was set at p ,0.05. Additionally, regression analyses were performed to assess the degree of relation between the measured value and the estimates obtained from GETP6. Mean values for measured and predicted VO2peak for the 3 groups are listed in Table I. Comparisons of the VO2peak values revealed that although predictions from GETP6 were similar to the measured values, GETP5 predictions resulted in significant underestimations of VO2peak. Importantly, there was no interFrom the Departments of Medicine (Section of Cardiology) and Health and Exercise Science, Wake Forest University, Winston-Salem, North Carolina; and Ball State University, Muncie Indiana. This study was supported by the following research grants: National Institutes of Health Grant AG12257, Bethesda, Maryland; The Claude D. Pepper Older Americans Independence Center of Wake Forest University National Institutes of Health Grant P60AG10484; and The Research and Development Fund of The Center for Ultrasound, and the General Clinical Research Center (Grant MO1RR07122) of the Wake Forest University School of Medicine of Wake Forest University, WinstonSalem, North Carolina. Dr. Kaminsky’s address is: Ball State University, Health and Physical Activity Building #223E, Muncie, Indiana 47306. E-mail: lkaminsk@gw.bsu.edu. Manuscript received August 27, 1999; revised manuscript received and accepted December 20, 1999.