Subsequent analysis showed significant difference in apelin concentration between healthy controls and patients with AF (0.982 ± 0.060 vs. 0.694 ± 0.148 ng/ml, p = 0.001, d = 1.044) as well as between patients with and without AF (0.694 ± 0.148 vs. 0.975 ± 0.458 ng/ml, p = 0.001, d = −1.021), respectively. This evidence concerns the gene APLN and atrial fibrillation.