AF remodeling

Mechanisms underlying ATR. Rapid atrial rates increase potentially cytotoxic Ca²⁺ loading. Autoprotective I_Ca,L reductions occur via rapidly developing functional changes (I_Ca,L inactivation) and more slowly developing changes in gene and protein expression. Decreased I_Ca,L reduces Ca²⁺ loading but decreases APD. Diminished APD shortens refractoriness and reduces the wavelength (WL), which allows for smaller and more atrial reentry circuits, thus making AF unlikely to terminate. Atrial tachycardia also increases inward-rectifier currents such as I_K1 and I_K,ACh,c, which further reduces APD and promotes AF.