Background
Recently, inflammation plays an essential role in the prognosis of atrial fibrillation (AF) patients. Systemic immune-inflammation index (SII), reflecting the inflammation status, which is measured by the formula: neutrophil count × platelet count/lymphocyte count, is a powerful prognostic marker in several types of cancer and cardiovascular disease. However, no information regarding the prognostic value of SII in patients with AF is available.