Right Atrial Function as a Novel Predictor for New‐Onset Atrial Fibrillation in Transthyretin Amyloid Cardiomyopathy

BACKGROUND: Left atrial functional parameters are established predictors of atrial fibrillation (AF), but the role of right atrial (RA) function, particularly RA peak longitudinal strain (LS), in transthyretin amyloid cardiomyopathy (ATTR-CM) remains unclear. This study aimed to investigate the relationship between RA function and AF onset in ATTR-CM. METHODS: The derivation cohort comprised 143 patients with ATTR-CM without prior atrial arrhythmias at Kumamoto University Hospital. Association between baseline parameters and new-onset AF during the follow-up period was analyzed using Cox regression models. Discrimination was assessed using time-dependent receiver operating characteristic analysis at 24 months. RESULTS: During follow-up (median, 30 months), 42 patients (29%) developed new-onset AF. Lower RA peak LS was independently associated with incident AF and showed moderate discrimination (time-dependent area under the curve, 0.72); the optimal cutoff at 24 months was 17.2%. Patients with RA peak LS <17.2% had significantly lower AF-free survival. A novel risk score integrating RA and left atrial peak LS and LA volume index effectively stratified AF risk. External validation in an independent cohort of 81 patients from Oita and Miyazaki University Hospitals confirmed consistent associations between lower RA peak LS and higher AF incidence, supporting the reproducibility of the findings. CONCLUSIONS: RA peak LS is a novel, robust predictor of new-onset AF in ATTR-CM and provides additional information alongside established clinical and left atrial parameters. Incorporating RA functional assessment may improve risk stratification and guide early interventions in high-risk patients.