Oxygen uptake kinetics in chronic heart failure : clinical and physiological aspects

Chronic heart failure (CHF) is a clinical syndrome characterized by exercise intolerance. Because resting indices of cardiac function and the level of perceived exercise intolerance correlate poorly with the exercise performance of these patients, exercise testing has become an important tool for the evaluation and monitoring of heart failure. Whereas the maximal aerobic capacity (peak VO2) has been shown to be a reliable indicator of the severity and prognosis of heart failure, submaximal exercise parameters may better reflect the ability to perform daily physical activities. Oxygen (O2) uptake kinetics describe the rate of change in oxygen uptake (VO2) during onset or recovery of exercise (O2 onset and recovery kinetics, respectively). Previous studies showed that, compared to healthy individuals, CHF patients have slower O2 onset and recovery kinetics, with the degree of the delay correlating with the functional impairment in these patients. However, it is not well established whether O2 uptake kinetics are sensitive to the effects of therapeutic interventions in CHF patients. Moreover, knowledge is lacking on the pathophysiological background of the delay in O2 uptake kinetics in CHF patients. This thesis addressed the following central questions: 1. Are O2 uptake kinetics useful in clinical practice to quantify and predict the effects of physical training in CHF patients? 2. What are the physiological determinants of O2 uptake kinetics in CHF patients?