Reproducibility of the determination of anaerobic threshold in patients with heart failure.

Background: The anaerobic threshold (AT) provides information on functional capacity in heart failure (HF). However, the visual determination of the AT by ventilatory methods is subjective, being susceptible to differences between examiners.

Objective: To evaluate the inter- and intra-examiner reproducibility in the determination of the AT in patients with mild to moderate HF, using visual-graphic and V-slope methods. To compare and correlate the results.

Methods: After performing a cardiopulmonary exercise test on a treadmill, visual-graphic and V-slope methods were used for the analysis of the AT. To assess the reproducibility, three examiners determined the AT twice by each method, on different days. For statistical analysis, we used intra-class correlation coefficient (ICC) with p <0.05.

Results: We evaluated a total of 16 subjects, with a mean age of 45.9 +/- 9.7 years, left ventricle ejection fraction of 20.5 +/- 8.1%, and peak exercise oxygen consumption of 20.6 +/- 7.8 mL/kgmin-1. The intra-examiner reproducibility was high in both methods for the three examiners, with ICC values between 0.87 and 0.99. The inter-examiner reproducibility was moderate in both visual-graphic method (ICC = 0.69) and V-slope method (ICC = 0.64). When comparing methods, the ICC found was 0.91.

Conclusion: AT determination by visual-graphic and V-slope methods showed high and moderate inter- and intra-examiner reproducibility, respectively. Moreover, both methods showed good agreement when compared with each other. These results suggest that both methods can be used in a reproducible way in AT assessment of patients with mild to moderate HF.