Chest
Clinical InvestigationsCARDIOLOGYOxygen Cost of Exercise Is Increased in Heart Failure After Accounting for Recovery Costs*
Section snippets
Subjects
Healthy adult volunteers (n = 11) were recruited from the Seattle area. Normal subjects were not trained athletes and were not receiving any medicines. Patients with heart failure (n = 45) were referred for clinical exercise testing from the End Stage Heart Failure Clinic (Table 1). All subjects signed an informed consent form approved by the Human Subjects Committee at the University of Washington. Subjects were between the ages of 23 years and 65 years. Criteria for heart failure were
Results
Table 1 outlines subject characteristics. The patients with heart failure were on average 13 years older than the healthy subjects, and most were male. The patients with heart failure were 9 kg heavier but similar in height. At peak exercise, the patients with heart failure had a 29% lower peak heart rate, a 60% lower peak oxygen consumption, a 60% lower peak workload, and a 34% lower oxygen pulse compared to control subjects (Table 2). Peak ventilatory efficiency (e/co2) was 23% higher, but
Discussion
Previous investigators have reported that patients with heart failure have a lower o2 at a given workload during maximal ramp exercise. They suggested that patients with heart failure were more efficient than normal subjects2356; however, none to our knowledge have accounted for the increase in recovery o2 in the evaluation of efficiency. We found total oxygen cost is greater when oxygen consumption during recovery is included for New York Heart Association class II-IV patients with heart
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Dr. Mitchell and Dr. Steele are supported by a grant from the American Federation for Aging Research.
Dr. Levy is supported by National Institutes of Health grant K12 AG00503.
Supported in part by the Geneva Foundation.
Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (e-mail: [email protected]).