Assessing pulmonary regurgitation for pulmonary valve replacement: the impact of heart rate on clinical decision-making - Insights from an exercise stress CMR study

Abstract Background Severe pulmonary regurgitation is a frequent long-term complication in patients with congenital heart disease, such as tetralogy of Fallot, pulmonary atresia, and pulmonary stenosis. While symptomatic individuals are generally treated with pulmonary valve replacement (PVR), the optimal timing of intervention in asymptomatic patients remains a topic of active investigation. Cardiovascular magnetic resonance (CMR) imaging, with its capacity for volumetric assessment and quantification of ejection fractions, serves as a cornerstone of diagnostic evaluation, guiding the timing of PVR. Purpose This study aimed to investigate whether the right ventricular end-diastolic volume index (RVEDVi) and pulmonary regurgitation (PR) fraction, used as criteria for PVR, are constant parameters or vary depending on heart rate and/or adrenergic stimulation. Methods We prospectively investigated 17 patients with chronic severe pulmonary regurgitation (PR fraction 40.8% +/- 6.2) due to tetralogy of Fallot (70%), pulmonary atresia with intact ventricular septum (12%), and pulmonary valve stenosis (18%). CMR imaging included flow measurements of the main pulmonary artery and ascending aorta acquired during free breathing, as well as steady-state free precession (SSFP) cine images in axial orientation obtained during breath-hold for volumetric assessment. All examinations were performed on a 1.5 Tesla MR scanner at rest and during submaximal exercise, which increased heart rate by an average of 24%—equivalent to a workload of approximately 25% of peak VO2. Exercise was conducted using a custom-built, MRI-conditional leg paddle ergometer, without interruptions during imaging. Results The results showed a reduction in PR fraction (from 40.8% +/- 6.2 to 35.3%+/-7.6, Δ -13.2%, p