Ventilatory anaerobic threshold before and after cardiac valve surgery

The purpose of this study was to objectively assess exercise tolerance before and after cardiac valve surgery by using an objectively determined ventilatory anaerobic threshold (AT). Nine patients (mean age: 38.2 +/- 8.1 years) with predominantly mitral regurgitant lesions were studied by a symptomatic maximal treadmill exercise test which included a determination of AT. The mean lengths of time from preoperative exercise testing to cardiac surgery, and from surgery to postoperative exercise testing were 5.9 +/- 4.0 and 12.1 +/- 8.3 months, respectively. The determination of AT on data plots was performed after blinding to patient identification and pre- vs postoperative status. After surgery, the clinical symptoms and NYHA class improved significantly with a decrease in the cardio-thoracic ratio and echocardiographic diastolic dimensions. The mean peak VO2 (ml/kg/min) increased significantly from 20.2 +/- 7.1 to 29.7 +/- 7.9 (p < 0.01). Together with these changes, AT (ml/kg/min in VO2) increased from a mean of 14.8 +/- 4.8 to 22.8 +/- 5.5 (p < 0.01). In conclusion, symptomatic improvement and an increase in peak oxygen uptake after cardiac valve surgery were accompanied by a significant increase in the objectively determined AT. AT determined in a blind manner provides an objective means of evaluating exercise tolerance when a double-blind intervention cannot be performed.