[Objective assessment of subjective symptom in chronic heart failure]

Objective assessment of subjective symptoms in patients with chronic heart disease (CHF) is useful not only in determining severity and prognosis, but also in evaluating the effects of therapy. Recently anaerobic threshold (AT) was introduced as an objective index for functional capacity. We began by evaluating the AT for assessing functional capacity in patients with CHF, using the cardiopulmonary exercise test. In this study, patients with CHF tended to show low values of VO2 at AT. Furthermore, VO2 at AT was decreased in accordance with the increasing severity of the NYHA classification. These results indicate that VO2 at AT can be used as an objective and reliable index for evaluating the functional capacity in patients with CHF. Decreased functional capacity is a major clinical problem in patients with CHF and is associated with skeletal muscle fatigue and/or dyspnea. Secondly, we observed the oxygenation of both working skeletal and respiratory muscles during exercise, using near-infrared spectroscopy to study the factors contributing to exercise limitation of CHF. In this study, the oxygenation profile of exercising skeletal muscle was similar to that of respiratory muscle, but the former showed anaerobic metabolism at an earlier stage of exercise than the latter. In patients with CHF this phenomenon was more prominent than that in normal subjects. These results indicate that near-infrared spectroscopy might be useful in objective assessment of subjective symptoms, namely skeletal muscle fatigue and dyspnea, in patients with CHF.