Response to progressive bicycle exercise before and following aortic valve replacement.

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 significant of O2 kinetics during exercise, however, requires further study.