GDF15 and atrial fibrillation: GDF-15 was only increased in AF patients with aortic stenosis when measured in the pericardial fluid (median (Q1–Q3) 775.6 (660.0–1274.8) ng/L vs. 616.2 (401.7–983.9) ng/L, p = 0.031); in fact, serologic GDF-15 remained similar between groups (1697.0 (1040.5–2727.5) ng/L vs. 1102.0 (764.7–1835.8) ng/L, p = 0.124).