Response to Progressive Bicycle Exercise before and following Aortic Valve Replacement

Abstract

The O₂ uptake response to symptom-limited progressive bicycle exercise that was performed serially before and up to 1 year after uncomplicated isolated aortic valve replacement (AVR) was evaluated in 37 patients. Before surgery, an unusually rapid exercise O₂ uptake response was seen in about half the patients, while the AVR appeared to result in a change in O₂ uptake kinetics to within normal limits in the majority of the patients within the first 3 postoperative months. The inappropriate O₂ uptake response was found to be associated with more significant limitation in exercise tolerance, and it appeared to be mediated not only by a pronounced exercise heart rate response but, probably, also by an exaggerated arteriovenous O₂ difference. These findings suggest that peripheral vascular responses in patients with chronic aortic valve disease may play a major role in the different O₂ uptake responses to progressive bicycle exercise. The physiological significance of O₂ kinetics during exercise, however, requires further study.