Cardiac magnetic resonance tissue characterization in endurance athletes with paroxysmal atrial fibrillation phenotype (PAFIYAMA).

BACKGROUND

Endurance athletes have an increased risk of atrial fibrillation (AF), and focal late gadolinium enhancement (LGE) is frequently detected on cardiac magnetic resonance (CMR); however, whether myocardial fibrosis or diffuse myocardial abnormalities underlie AF-related functional phenotypes remains unclear. We previously described a paroxysmal AF phenotype in male endurance athletes (PAFIYAMA), characterized by reduced forward flow despite preserved global systolic function; nonetheless, the underlying myocardial substrate remains unknown.

METHODS

In this observational cross-sectional study, 63 competitive male endurance athletes (PAFIYAMA n = 22; controls n = 41) underwent CMR with cine imaging, LGE, native T1, extracellular volume fraction (ECV), and T2 mapping. Training load was derived from the Lifetime Total Physical Activity Questionnaire. Group comparisons and multivariable models adjusted for age, body mass index, training load, and peak exercise blood pressure.

RESULTS

Focal LGE was present in 15/63 (24%) athletes and did not differ between PAFIYAMA and controls. Among LGE-positive athletes, enhancement was predominantly hinge-point/insertional (8/15, 53.3%) or limited septal intramyocardial (6/15, 40.0%), with one subepicardial lateral case (1/15, 6.7%). Athletes with LGE had larger indexed biventricular volumes but similar native T1, ECV, and T2. Compared with controls, PAFIYAMA athletes showed lower biventricular stroke volume indices and lower left ventricle mass, with a slightly lower LVEF that remained within the normal range, and no differences in LGE prevalence or mapping indices.

CONCLUSIONS

In endurance athletes with the PAFIYAMA phenotype, CMR tissue characterization does not support focal LGE or diffuse mapping abnormalities as the substrate of the functional phenotype; interpretation of LGE in athletes should integrate pattern and clinical context.