Abstract 15449: Cardiopulmonary Best Abstract Award : Pausing Reveals Exercise-Induced Uncoupling: Exploring the Dynamics of RV-PA Coupling in the Six-Minute Walking Test

Abstract

Background: The six-minute walking test (6MWT) is a commonly used test for assessing the functional capacity of patients with pulmonary hypertension (PH), providing functional and prognostic information. Functional capacity depends on RV-PA coupling, the matching of right ventricular contractility to afterload. However, the dynamics of RV-PA coupling during the 6MWT have never been studied. Methods: We used a wireless hemodynamic monitoring system (CorLog, emka-medical, Germany) to continuously measure right ventricular pressure in 10 patients with PH (8 = group I, 1 = III, 1 = IV) during a 6MWT. We calculated right ventricular ejection fraction (RVEF) and Ees/Ea based on the pressure signal as shown in the figure (panel a). Dyspnea was evaluated using the Borg scale. Results: By analyzing the hemodynamic response during the 6MWT, we identified two patterns: 1) Improved/preserved coupling: Five patients exhibited an initial improvement in Ees/Ea and maintained coupling at least at the baseline level throughout the test, without requiring pauses. 2) Uncoupling associated with pauses: Five patients experienced a slight increase in Ees/Ea at the beginning, followed by a progressive loss of coupling and ejection fraction, necessitating pauses. During pauses, Ees/Ea values restored, enabling patients to resume walking. Patients of the second phenotype reported higher levels of dyspnea. The highest reported Borg score was 8 ± 0.9 vs. 4.6 ± 1.2 in the first group. Also, the covered distance was shorter in the second group (159 ± 64m vs. 288 ± 88m, p=0.03). Both groups showed differences in Ees/Ea (0.47 [0.46 - 0.57] vs. 0.34 [0.30 - 0.43], P=0.05) and RVEF (34 ± 4.1% vs. 28.5 ± 2.6%, P=0.03) at baseline, with Group One exhibiting superior values. Conclusion: This is the first investigation into the significance of RV-PA coupling in real-life exercise limitation and dyspnea during the 6MWT. Pauses observed during the 6MWT can serve as indicators of exercise-induced uncoupling.