Can common exercise indices determine peak exercise oxygen consumption and anaerobic threshold during stress testing in patients with chronic congestive heart failure?

Maximal oxygen consumption (VO2 max) is one of the most important predictors of prognosis in chronic heart failure and is now used to define degree of heart failure. While most centres can routinely do treadmill exercise testing (TMT), VO2 max measurements are not widely available. We, therefore, analysed the ability to predict VO2 max from common TMT variables: Peak exercise heart rate, exercise time, and METS achieved in 26 patients with chronic congestive heart failure (NYHA II-III, ejection fraction 43 +/- 2%) in whom exercise VO2 studies were simultaneously done by breath to breath expiratory gas analysis using a metabolic cart. METS achieved during exercise and exercise time correlated reasonably well although not perfectly (r = 0.78 & 0.73 respectively, tail critical value +/-0.41). Resting ejection fraction did not correlate at all (r = 0.0004). The regression equation (2.7) (METS) + 5.8 defined VO2 max with SE of 0.47. Although in unvariate analysis, exercise time, METS achieved & peak heart rate predicted VO2 max, only METS achieved was predictive in step wise regression. None of the parameters predicted the anaerobic threshold accurately although there was a modest relation between AT and peak exercise VO2. We conclude that most exercise variables do not accurately predict VO2 max in patients with chronic congestive heart failure. METS achieved is the best predictor and the VO2 max can be predicted using a regression equation. Anaerobic threshold cannot be predicted without tests involving expiratory gas analysis.