Indications and limits of the exercise test in chronic heart failure

Assessment of exercise capacity has been widely used in the evaluation of chronic heart failure (CHF), both to define the severity of the syndrome and to assess the changes induced by therapy. Various exercise tests and protocols can be used. The simple stress test using the exercise bicycle or the treadmill can give useful indications only in patients with severe or lower functional reductions. Maximum exercise duration usually depends on the patientʹs and the physicianʹs motivation. The addition of respiratory gas exchange measurements, maximum oxygen consumption (VO2) or anaerobic threshold, increases the exactness of the assessment of the exercise limitation in CHF. VO2 maximum provides an objective marker of aerobic capacity and it is biased by neither the patient nor the physician. This technique, however, requires the patient to exercise to exhaustion, and it is somewhat subjective and not indicative of normal daily exercise routine. The anaerobic threshold is a useful way of evaluating adaptability to submaximal efforts and the impact of the therapy on the daily performance. Nevertheless, it is significantly influenced by the fitness level and it has a reduced prognostic capability compared to VO2 maximum. Submaximal exercise tests discriminate particularly between patients with severe CHF. The major limits are the influence of the patientʹs motivation and its limited validation in terms of reproducibility and prediction in controlled surveys.