Abstract Body (Do not enter title and authors here): Background
Whether the presence and extent of atrial cardiomyopathy (AtCM) has an impact on effectiveness of early rhythm control (ERC) in patients with atrial fibrillation (AF) is not known.

Method
In this prespecified subanalysis of the EAST-AFNET 4 trial, the effects of ERC on outcome were compared between AF patients with different stages of AtCM. AtCM was determined by atrial size, PR interval in the surface ECG, and brain natriuretic peptide concentrations (NTproBNP). Associations between AtCM and the primary outcomes (cardiovascular death, stroke, hospitalization for heart failure and acute coronary syndromes; ACS) were compared over a mean follow-up of 5.1 years.

Results
The EAST-AFNET 4 trial included a total of 2,789 patients. For this analysis, 1,395 patients on ERC and 1,394 on usual care (UC) were included. Left atrial (LA) size varied substantially in the overall study population (largest LA size up to 8.6 cm) without a significant difference between ERC and UC at baseline (mean ERC 4.4 ± 0.8 cm vs. UC 4.4 ± 0.9 cm; p=ns). PR intervals (ERC: 176 ± 32ms vs. UC 178 ± 37ms) and NTproBNP concentrations (mean ERC 772 ± 1,268 pg/mL vs. UC 825 ± 1,135 pg/mL; p=ns) were comparable between the two randomized groups. Larger left atrial diameters were related to occurrence of first primary outcome (HR per SD 1.26; 1.12-1.43; p<0.001) and recurrence of AF (HR per SD 1.19; 1.09-1.29; p<0.001). Similarly, higher NTproBNP concentrations were associated with the first primary outcome (HR per SD 1.81; 1.53-2.15; p<0.001) and with AF recurrence (HR per SD 1.53; 1.37-1.7; p<0.01). ERC reduced the first primary outcome during a 5.1 years follow-up (ERC HR 0.69;0.54-0.9; p=0.005), regardless of the degree of AtCM.

Conclusion
In patients with recently diagnosed AF, recurrent AF and cardiovascular events are more common in the presence of atrial cardiomyopathy. Early rhythm control is effective regardless of the degree of AtCM in AF patients.