New Exercise Test Variables for the Decision Process in Pulmonary Valve Replacement

Background: Pulmonary valve regurgitation leads to chronic volume overload with RV remodeling. Progressive RV dilatation may lead to RV dysfunction, exercise intolerance, and an increased risk of VT. Even though considerable research has investigated the best timing for pulmonary valve repair it remains an unanswered question. Enlargement of the RV determined using cMRI remains the gold standard for this decision. If the correct parameter could be identified, the direct measurement of exercise tolerance using CPET could possibly aid the decision process. However, so far, all classical CPET parameters could not be correlated to RV-volume, nor could any improvement of these parameters after valve replacement be discerned.

Methods: We evaluated retrospectively all cardiopulmonary exercise tests performed on a treadmill or exercise bike by patients with PVR in our hospital over the last four years. As a control group we used CPET results from patients with comparable heart defects but without PVR of comparable age and sex. All CPET results were compared with data from cMRI, resting and exercise ECG, and echocardiography. We introduced several new CPET parameters, especially designed to analyze the O2pulse before and after the end of exercise.

Results: Overall, we were able to include 44 patients with PVR (mean age: 18.5 ± 0.8 years) and 25 subjects without PVR (mean age: 18.3 ± 1.0 years). There were no significant differences for all classical CPET parameters between the patients with PVR and the control group. Nor were there any significant correlations between these parameters and the parameters from the cMRI, ECG or echocardiogram. However, the duration of elevated O2pulse after peak exercise proved to be significantly different between the two groups (110 ± 240 milliseconds vs. 29 ± 60 milliseconds).

Conclusion: In this study, classic CPET parameters proved to add no benefit to the decision process for pulmonary valve replacement in patients with PVR as shown previously. However, the course of the O2pulse before and after the end of exercise proved to be significantly different between the two groups. The O2pulse represents a surrogate parameter of the stroke volume calculated using Fick’s law. It usually increases up to termination of exercise and then drops immediately. The paradoxical course of the O2pulse suggests that the stroke volume cannot be increased according to the demand and then does not decrease readily, maybe as a consequence of beginning RV remodeling and an increased stiffness of this RV.

Publication History

Article published online:
13 February 2024