Ionic mechanisms of electrical remodeling in human atrial fibrillation

Objectives: Atrial fibrillation (AF) is associated with a decrease in atria l ERP and ERP adaptation to rate as well as changes in atrial conduction ve locity. The cellular changes in repolarization and the underlying ionic mec hanisms in human AF are only poorly understood. Methods: Action potentials (AP) and ionic currents were studied with the pa tch clamp technique in single atrial myocytes from patients in chronic AF a nd compared to those from patients in stable sinus rhythm (SR). Results: The presence of AF was associated with a marked shortening of the AP duration and a decreased rate response of atrial repolarization. L-type calcium current (I-Ca,I-L) and the transient outward current (I-10) were bo th reduced about 70% in AF, whereas an increased steady-state outward curre nt was detectable at test potentials between -30 and 0 mV. The inward recti fier potassium current (I-K1) and the acetylcholine-activated potassium cur rent (I-KACh) were increased in AF at hyperpolarizing potentials. Voltage-d ependent inactivation of the fast sodium current (I-Na) was shifted to more positive voltages in AF. Conclusions: AF in humans leads to important changes in atrial potassium an d calcium currents that likely contribute to the decrease in APD and APD ra te adaptation. These changes contribute to electrical remodeling in AF and are therefore important factors for the perpetuation of the arrhythmia. (C) 1999 Elsevier Science B.V. All rights reserved.