Introduction Atrial fibrillation (AF)-induced cardiomyopathy (AIC) is retrospectively defined after normalisation of left ventricular ejection fraction (LVEF) in sinus rhythm. It is unclear why some patients develop AIC. Hypothesis Patients with AIC have a subtle cardiomyopathic process that precedes their AF-mediated LVEF reduction. Detailed assessment of cardiac function after successful catheter ablation will reveal this. Objective To evaluate the utility of measures to identify cardiomyopathic features that persist after LVEF normalisation in AIC. Methods Patients with rate-controlled persistent AF and LVEF&lt;50% undergoing catheter ablation (CA) were prospectively evaluated using echocardiography, cardio-pulmonary exercise testing and serum N-terminal pro b-type natriuretic peptide (NT-proBNP) at baseline and 6 months after CA. Participants with AIC, (LVEF recovery (≥50%) and no other cause for cardiac dysfunction) were evaluated using left ventricular (LV) longitudinal strain and left atrial (LA) reservoir strain (LARS). Changes in peak oxygen consumption and the minute ventilation/carbon dioxide production slope were measured as markers of functional capacity and ventilatory inefficiency. A control group of patients with persistent AF with preserved LVEF were also enrolled. Results 34/41 (82.9%) participants recovered LVEF in sinus rhythm; defined as AIC. NT-proBNP levels were elevated in 18 (52.9%), and 16 reported ongoing heart failure (HF) symptoms. 10 (29.4%) had no improvement in functional capacity, and seven (20.6%) showed persistent ventilatory inefficiency. 20 (58.8%) had impaired global LV longitudinal strain with a relative apical sparing pattern. Nine (26.5%) had impaired LARS. There was an overlap of these abnormalities. 32 (94.1%) demonstrated at least one, 17 (50.0%) having no cardiovascular risk factors. Patients with preserved LVEF during persistent AF had similar demographics but a lower burden of short R-R intervals (&lt;660 ms) on Holter monitoring. Discussion Abnormal structural, metabolic and HF biomarkers are seen in patients with AIC in sinus rhythm. These features may represent a precedent subtle cardiomyopathic process predisposing them to left ventricular systolic dysfunction in AF. Trial registration number NCT04987723 .

Characterisation of patients who develop atrial fibrillation-induced cardiomyopathy