Interleukin-18 among atrial fibrillation patients in the absence of structural heart disease

Inflammation plays a role in the genesis and perpetuation of atrial fibrillation (AF). Interleukin (IL)-18 is a pleiotropic proinflammatory cytokine with a central role in the inflammatory cascade. We hypothesize that the circulating IL-18 concentration is elevated in AF patients. In a case-control study design, 56 cases with AF and 26 controls were enrolled. All AF cases were categorized into paroxysmal and persistent AF or lone AF and AF with hypertension. Circulating levels of IL-18, tumour necrosis factor-alpha, high-sensitivity C-reactive protein, matrix metalloproteinase (MMP)-9, and tissue inhibitor of MMP-1 were measured. In adjusted analyses, only age, MMP-9, and IL-18 were independently associated with AF, in which IL-18 had the most significant association (P = 0.0011, standardized estimate &bgr = 1.76, OR = 1.02, 95% confidence interval: 1.01-1.03). Interleukin-18 levels in persistent AF patients were higher than those in paroxysmal ones (P = 0.0011). Patients who developed AF within 24 h prior to sampling displayed a higher level of IL-18 than those with sinus rhythm (P = 0.0027). Interleukin-18 was positively correlated with left atrial diameter (r = 0.33, P = 0.0117). This study documents the elevated IL-18 in AF patients. Interleukin-18 may be superior to other inflammatory markers which are known to be elevated in AF.