Visualization of elusive structures using intracardiac echocardiography: Insights from electrophysiology

Electrophysiological mapping and ablation techniques are increasingly used to diagnose and treat many types of supraventricular and ventricular tachycardias. These procedures require an intimate knowledge of intracardiac anatomy and their use has led to a renewed interest in visualization of specific structures. This has required collaborative efforts from imaging as well as electrophysiology experts. Classical imaging techniques may be unable to visualize structures involved in arrhythmia mechanisms and therapy. Novel methods, such as intracardiac echocardiography and three-dimensional echocardiography, have been refined and these technological improvements have opened new perspectives for more effective and accurate imaging during electrophysiology procedures. Concurrently, visualization of these structures noticeably improved our ability to identify intracardiac structures. The aim of this review is to provide electrophysiologists with an overview of recent insights into the structure of the heart obtained with intracardiac echocardiography and to indicate to the echo-specialist which structures are potentially important for the electrophysiologist

Functional Mathematical Model of Dual Pathway AV nodal Conduction

[EN] Dual atrioventricular (AV) nodal pathway physiology is described as two different wave fronts that propagate from the atria to the His bundle: one with a longer effective refractory period [fast pathway (FP)] and a second with a shorter effective refractory period [slow pathway (SP)]. By using His electrogram alternance, we have developed a mathematical model of AV conduction that incorporates dual AV nodal pathway physiology. Experiments were performed on ¿ve rabbit atrial-AV nodal preparations to develop and test the presented model. His electrogram alternances from the inferior margin of the His bundle were used to identify fast and slow wave front propagations. The ability to predict AV conduction time and the interaction between FP and SP wave fronts have been analyzed during regular and irregular atrial rhythms (e.g., atrial ¿brillation). In addition, the role of dual AV nodal pathway wave fronts in the generation of Wenckebach periodicities has been illustrated. Finally, AV node ablative modi¿cations have been evaluated. The model accurately reproduced interactions between FP and SP during regular and irregular atrial pacing protocols. In all experiments, speci¿city and sensitivity higher than 85% were obtained in the prediction of the pathway responsible for conduction. It has been shown that, during atrial ¿brillation, the SP ablation signi¿cantly increased the mean HH interval (204 39 vs. 274 50 ms, P 0.05), whereas FP ablation did not produce signi¿cant slowing of ventricular rate. The presented mathematical model can help in understanding some of the intriguing AV node mechanisms and should be considered as a step forward in the studies of AV nodal conduction.This work was supported by the Spanish Ministry of Education and Science under TEC2009-13939 and by the Universitat Politecnica de Valencia through its research initiative program. In addition, partial support was provided by a grant from the State of Ohio to the Cleveland Clinic Atrial Fibrillation Innovation Center, a Wright Center of Innovation.Martínez Climent, BA.; Guillem Sánchez, MS.; Zhang, Y.; Millet Roig, J.; Mazgalev, TN. (2011). Functional Mathematical Model of Dual Pathway AV nodal Conduction. AJP - Heart and Circulatory Physiology. 300(4):1393-1401. doi:10.1152/ajpheart.01175.2010S13931401300