7 Cardiovascular magnetic resonance assessment of pulmonary transit time during adenosine stress in endurance athletes

<h3>Introduction</h3> Pulmonary transit time (PTT) is a valuable measure of cardiopulmonary function. The impact of Atrial Fibrillation (AF) on PTT in athletes remains understudied. Understanding the relationship between fitness levels and PTT could offer insights into cardiopulmonary adaptation from exercise. This study aims to compare PTT at rest and during stress between veteran endurance athletes in sinus rhythm (SR) and AF. Furthermore, we seek to determine the relationship between PTT and fitness, and whether this relationship is impacted by AF. <h3>Materials and Methods</h3> 106 amateur competitive cyclists and triathletes in SR, and 25 with AF, aged over 50 years were prospectively recruited. Participants underwent comprehensive stress-perfusion cardiac magnetic resonance imaging and exercise history was recorded. PTT was measured automatically from arterial input function dynamic series of both the left (LV) and right ventricle (RV) during rest/stress perfusion imaging, calculated as the time (in seconds) between the centroid of the LV and RV indicator dilution curves. Unpaired t-tests were used to compare PTT between the two groups, while regression analysis examined the relationship between PTT and fitness metrics (active years, training hours, LV mass, LV ejection fraction (EF), RVEF), and whether AF modified this. <h3>Results</h3> PTT during stress was significantly prolonged in athletes with AF compared to SR (8.4 s vs. 7.1 s, p = 0.015). The AF group demonstrated significantly lower LV mass (127.5 g vs. 138 g, p = 0.044) and higher left atrial volume (LAV) (111.8 mL vs. 89.2 mL, p &lt; 0.001). Regression analysis revealed no significant correlation between PTT and fitness metrics, even when accounting for AF. <h3>Discussion</h3> In lifelong endurance athletes, PTT during stress is significantly prolonged in those with AF compared to SR. However, the significant differences in LV mass and LAV suggest that this is due to AF-related structural cardiac changes, rather than fitness levels. As an ongoing study, we seek to compare VO2 max to PTT during stress in both groups to further validate this. <h3>Conclusion</h3> In endurance athletes the presence of AF affects the PTT during stress. Further studies are needed to understand the clinical significance of this observation. <h3>Acknowledgements</h3> This research was supported by a scholarship from Heart Research UK, which funded and made it possible for my summer research to take place as a medical student. I am grateful for their support.