DIFFERENCE BETWEEN PEAK VO2 ASSESSED BY CARDIOPULMONARY EXERCISE TEST USING THE BRUCE PROTOCOL AND ESTIMATED BY EXERCISE STRESS TEST IN PATIENTS WITH CHAGASIC CARDIOMYOPATHY

Abstract

Chagas disease remains a significant public health problem in Latin America, even more than a century after its discovery. Among the clinical forms, Chagas cardiomyopathy is the most common and severe, presenting with reduced functional capacity from the early stages, which reinforces the need for regular functional assessment. Measuring peak oxygen consumption (VO2peak) using the Cardiopulmonary Exercise Test (CPET) is the gold standard, but it is an expensive method and not easily accessible in regions with limited technological resources. In this context, the exercise stress test emerges as an alternative, although VO2peak is only estimated, making it necessary to verify the accuracy of the prediction formulas in this population. Thus, the objective of this study was to compare VO2peak assessed directly by CPET with VO2peak estimated by the exercise stress test. Thirty-one patients with Chagas cardiomyopathy (48.3 ± 7.4 years; NYHA I–III) undergoing cardiopulmonary exercise testing (CPET) using the Bruce protocol were evaluated. Estimated peak VO2 was calculated using the formulas VO2peak = (2.9 × time in minutes) + 8.33 and, for women, VO2peak = (2.74 × time in minutes) + 8.03. The difference between the values ​​was analyzed using parametric or non-parametric tests, according to the data distribution; correlation was assessed using appropriate correlation tests, and agreement was assessed using the Bland-Altman plot. The directly assessed peak VO2 was 25.8 ± 8.4 mL·kg·min, while the estimated peak VO2 was 33.4 ± 4.8 mL·kg·min, with a significant difference (p<0.001). Overestimation of 29.4% was observed, and there was no correlation between the measurements (r=0.195; p=0.302). In the Bland-Altman plot, most values ​​remained within the limits of agreement, however, with a high average difference (7.7 mL·kg·min). It is concluded that, in patients with Chagas cardiomyopathy, the prediction of peak VO2 by the exercise stress test differs significantly from the direct measurement, with no correlation between the values, indicating the need for new equations in future studies.

DOI: https://doi.org/10.56238/sevened2026.001-037