Abstract
Heart failure constitutes a major public health problem worldwide. The electrophysiological remodeling of failing hearts sets the stage for malignant arrhythmias, in which the role of the late Na + current (I NaL) is relevant and is currently under investigation. In this study we examined the role of I NaL in the electrophysiological phenotype of ventricular myocytes, and its proarrhythmic effects in the failing heart. A model for cellular heart failure was proposed using a modified version of Grandi etal. model for human ventricular action potential that incorporates the formulation of I NaL. A sensitivity analysis of the model was performed and simulations of the pathological electrical activity of the cell were conducted. The proposed model for the human I NaL and the electrophysiological remodeling of myocytes from failing hearts accurately reproduce experimental observations. The sensitivity analysis of the modulation of electrophysiological parameters of myocytes from failing hearts due to ion channels remodeling, revealed a role for I NaL in the prolongation of action potential duration (APD), triangulation of the shape of the AP, and changes in Ca 2+ transient. A mechanistic investigation of intracellular Na + accumulation and APD shortening with increasing frequency of stimulation of failing myocytes revealed a role for the Na +/K + pump, the Na +/Ca 2+ exchanger and I NaL. The results of the simulations also showed that in failing myocytes, the enhancement of I NaL increased the reverse rate-dependent APD prolongation and the probability of initiating early afterdepolarizations. The electrophysiological remodeling of failing hearts and especially the enhancement of the I NaL prolong APD and alter Ca 2+ transient facilitating the development of early afterdepolarizations. An enhanced I NaL appears to be an important contributor to the electrophysiological phenotype and to the dysregulation of [Ca 2+] i homeostasis of failing myocytes. © 2012 Trenor et al.
