Exercise-related ventilatory abnormalities are more specific for functional impairment in chronic heart failure than reduction in peak exercise oxygen consumption

Background: Impaired functional capacity during exercise is used to assess need for transplantation in congestive heart failure patients, although impaired capacity is present in several chronic illnesses. The purpose of this study was to test the hypothesis that ventilatory abnormalities during exercise, rather than functional capacity, are specific to congestive heart failure patients. Methods: We compared exercise-related gas exchange among a group of congestive heart failure patients and a group of patients who had chronic liver disease and normal cardiac function, matched for functional impairment, and a group of normal controls. Results: Patients with congestive heart failure and patients with chronic liver disease experienced marked reduction in peak exercise oxygen consumption compared with normal controls (14.0 +/- 1.4 and 14.2 +/- 3.7 ml/kg/min, respectively, vs 25.8 +/- 5.6 ml/kg/min, p < 0.01). Minute ventilation at peak exercise was significantly higher in congestive heart failure subjects than in chronic liver disease patients (59.3 +/- 16.8 liter/min vs 41.4 +/- 14.2 liter/min, p < 0.05), although carbon dioxide production was similar (1,380 +/- 308 ml vs 1,180 +/- 389 ml, p = not significant), so that the ratio of minute ventilation to carbon dioxide production (ventilatory equivalent for carbon dioxide, an index of ventilatory drive) was significantly elevated in congestive heart failure subjects (43 +/- 9 vs 36 +/- 7, p < 0.05). Conclusions: Although functional impairment characterizes both congestive heart failure and chronic liver disease, only congestive heart failure patients exhibit exercise-related ventilatory abnormalities. Exercise-related ventilatory abnormalities may be more specific to the underlying pathophysiology of chronic heart failure and should be considered when evaluating patients for heart transplantation.