Potential Ionic Mechanism for Repolarization Differences Between Canine Right and Left Atrium

Abstract—Experimental and clinical evidence suggests a critical role for the left atrium (LA) in atrial fibrillation (AF). In animal models, repolarization is faster in the LA than in the right atrium (RA), leading to more stable reentry circuits with a shorter intrinsic period in the LA. The ionic mechanisms underlying LA-RA repolarization differences are unknown. Therefore, we evaluated ionic currents and action potentials (APs) with the whole-cell patch clamp in isolated canine atrial myocytes. The density of the rapid delayed rectifier current (IKr) was greater in the LA (eg, 1.83±0.10 pA/pF at +20 mV) than in the RA (1.15±0.07 pA/pF, P<0.01; n=16 cells per group). The slow and ultrarapid delayed rectifier, the inward rectifier, L-type Ca2+, and transient outward K+ currents were all comparable in the LA and RA. There were no differences in kinetic or voltage-dependent properties of currents in LA versus RA. Western blots of ether-a-go-go–related gene (ERG) protein in three RA and corresponding LA reg...