[Determination of anaerobic threshold and influence of hemodynamics on exercise intolerance in patients after cardiac valve surgery].

In order to evaluate the exercise tolerance of the patients after cardiac valve surgery, the exercise stress test by supine bicycle ergometer was performed in 26 patients. An anaerobic threshold (AT) was determined by lactate threshold. The mixed venous oxygen saturation (SvO2) was measured simultaneously to assess the relationship between AT and SvO2 during exercise test. The study group consisted of 10 men (mean age: 46.2 years) and 16 women (mean age: 49.4 years). Each patient received either of following two programs: 1) a single step test of approximately 5 METS, which corresponded to the exercise tolerance level of NYHA functional Class II (Group A, 18 patients); and 2) a consecutive multi-staged test, which was begun at a worked of 25 W and increased by 25 W in every 3 minutes until the symptomatic maximum or ended at 100 W (Group B, 8 patients). Eleven patients (6 patients in Group A, 5 patients in Group B) had reached AT point during the test. SvO2 was 26.6 +/- 3.6% in group A patients, and 29.3 +/- 1.4% in group B patients at the point of AT. This data suggests that anaerobic metabolism begins at the level of SvO2 slightly less than 30%, and that SvO2 is a simple and usefull indicator for the estimation of AT. In patients with reduced exercise tolerance which was recognized by AT point at exercise stage of about 5 METS, the right atrial and pulmonary arterial mean pressure were higher than the others (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)