Concerning NT-pro-BNP, this biomarker was increased in AF patients in both biological matrices–6843.0 (1522.8–10830.3) ng/L vs. 952.6 (501.6–1997.5) ng/L, p < 0.001 in pericardial fluid; and 827.2 (668.1–1495.0) ng/L vs. 272.7 (146.2–601.3) ng/L, p = 0.002 in serum. The gene discussed is NPPB; the disease is atrial fibrillation.