[Oxygen uptake during exercise before and after cardiac valve surgery: anaerobic threshold and maximal oxygen uptake]

Exercise stress tests with bicycle ergometer were performed before and after surgery in 14 patients with valvular heart diseases. Aortic valve replacements were performed in two patients, open mitral commissurotomy in two, mitral valve replacement in eight and combined valvular procedure in two. All patients except one showed improved NYHA function class after the surgery. Oxygen uptake was assessed at anaerobic threshold and peak achieved workload. One patients who failed to increase his heart rates during exercise both before and after surgery revealed unchanged NYHA function class and decreased oxygen uptake postoperatively. The other patients showed statistically significant increases of oxygen uptake not only at anaerobic threshold but also at peak achieved workload. At anaerobic threshold, oxygen uptake was 0.92 + 0.14 l/min before surgery and 1.09 + 0.22 l/min after surgery. Maximal oxygen uptake increased from 1.11 + 0.27 l/min to 1.47 + 0.36 l/min postoperatively. Heart rates at anaerobic threshold and at peak workload showed no significant differences. Postoperative increases of oxygen uptake was achieved by the increases of oxygen pulses, which was considered to be from the increases of stroke volumes.