van der Velden et al. in their research indicated that local variations in the expression of connexin proteins (Cx40 or Cx43), whether upregulated or downregulated, may underlie conduction velocity heterogeneity (or dispersion), thereby creating conditions conducive to micro-reentry, which could lead to sustained atrial fibrillation (41). This evidence concerns the gene GJA5 and atrial fibrillation.