Recommendations for exercise testing in chronic heart failure patients.

In the chronic heart failure patient, exercise intolerance is one of the hallmarks of disease severity. However, symptoms are modestly related to measures of functional capacity, and symptom scores during exercise tend to under-estimate the level of functional disability, suggesting that clinical symptoms are not reliable indices of exercise intolerance. Therefore, exercise testing has been widely used in the assessment of chronic heart failure patients. Directly measured VO2 has been shown to be a reproducible marker of exercise tolerance in chronic heart failure, and to provide objective and additional information regarding the patient’s clinical status and factors which limit exercise performance. ‘Maximal VO2’ is traditionally defined as a plateau of the maximum oxygen consumption reached during exercise (it does not increase any more while external work increases). VO2 max is generally not achieved in chronic heart failure patients, because they are usually limited by symptoms of fatigue or dyspnoea. ‘Peak VO2’ (VO2 at peak exercise) is the better term to describe the highest oxygen uptake achieved in chronic heart failure. Like maximal workload and exercise duration, peak VO2 is dependent upon motivation and perceived symptoms (of both patient and physician). It is more reliable than other indicators of exercise tolerance. Moreover, exceeding the anaerobic threshold (which generally occurs at 60–70% of the peak VO2) or a respiratory exchange ratio (the ratio of VCO2 to VO2) exceeding 1·0 at peak exercise suggests adequate patient effort.