A Computational Study of the Electrophysiological Substrate in Patients Suffering From Atrial Fibrillation.

In the context of cardiac electrophysiology, we propose a novel computational approach to highlight and explain the long-debated mechanisms behind atrial fibrillation (AF) and to reliably numerically predict its induction and sustainment. A key role is played, in this respect, by a new way of setting a parametrization of electrophysiological mathematical models based on conduction velocities; these latter are estimated from high-density mapping data, which provide a detailed characterization of patients' electrophysiological substrate during sinus rhythm. We integrate numerically approximated conduction velocities into a mathematical model consisting of a coupled system of partial and ordinary differential equations, formed by the monodomain equation and the Courtemanche-Ramirez-Nattel model. Our new model parametrization is then adopted to predict the formation and self-sustainment of localized reentries characterizing atrial fibrillation, by numerically simulating the onset of ectopic beats from the pulmonary veins. We investigate the paroxysmal and the persistent form of AF starting from electro-anatomical maps of two patients. The model's response to stimulation shows how substrate characteristics play a key role in inducing and sustaining these arrhythmias. Localized reentries are less frequent and less stable in case of paroxysmal AF, while they tend to anchor themselves in areas affected by severe slow conduction in case of persistent AF.

Simultaneous endo-epicardial-high density mapping of ventricular tachycardia with the use of multi-electrode mapping catheters.

We herein describe a case of VT in an ischemic cardiomyopathy patient utilizing a novel technique of simultaneous endo-epicardial high-density mapping. Epicardial access, in addition to retrograde aortic endocardial access, was performed. Following the creation of the respective endocardial and epicardial electrical substrate maps, activation mapping of the VT was then performed simultaneously with two overlapping HD Grid catheters. Full diastolic pathway mapping was achieved, with EGMs recorded in all segments of the diastolic interval, on the epicardial surface. This case highlights the feasibility of a technique that can reliably detect the presence of activation bridges in a 3D model of VT.