TLR4 and atrial fibrillation: P. gingivalis can increase the expression of toll-like receptor 2 (TLR-2) [30] and toll-like receptor 4 (TLR-4) [31], which can induce atrial fibrosis [32], reduce the transient outward potassium ion current [33], promote atrial structural remodeling and electrical remodeling, and increase the occurrence risk and recurrence risk of atrial fibrillation.