Functional predictors of poor outcomes in Chagas cardiomyopathy: The value of end-tidal carbon dioxide at peak exercise

Background: Functional impairment can be detected from the onset of heart disease in patients with Chagas cardiomyopathy (ChC) and the prognostic value of the end-tidal carbon dioxide at peak exercise (PETCO₂ peak) should be investigated.

Objective: To verify the prognostic value of PETCO₂ peak in patients with ChC.

Methods: Seventy-six patients with ChC (49.2 ± 9.8 years, NYHA I-III) were evaluated by echocardiography and Cardiopulmonary Exercise Testing. Patients were followed up to four years and the end-point was defined as cardiovascular death, stroke, or cardiac transplantation.

Results: At the end of the follow-up period (29.0 ± 16.0 months), 16 patients (21%) had experienced adverse events. The area under the receiver operating characteristic (ROC) curve to identify the risk of adverse events by PETCO₂ peak in patients with ChC was 0.83 (95% CI: 0.69 to 0.97), and the value of 32 mmHg was the optimal cut point (70% of sensitivity and 85% of specificity). In the Kaplan-Meier diagram, there was a significant difference (p<0.001) between patients with reduced (≤ 32 mmHg) and preserved PETCO₂ peak (>32 mmHg). In the final Cox multivariate model, only reduced PETCO₂ peak (HR 4.435; 95% CI: 1.228 to 16.016, p = 0.023) and VO_2peak (HR 0.869; 95% CI: 0.778 to 0.971, p = 0.013) remained as independent predictors of poor outcome in ChC patients.

Conclusion: Reduced PETCO₂ peak and VO2_peak demonstrated valuable prognostic value in patients with ChC. The cutoff points for both functional variables can be used during risk stratification and may help in the development of therapeutic strategies in ChC patients.