Use of Atrial Fibrillation Electrograms and T1/T2 Magnetic Resonance Imaging to Define the Progressive Nature of Molecular and Structural Remodeling: A New Paradigm Underlying the Emergence of Persistent Atrial Fibrillation.

Background: The temporal progression states of the molecular and structural substrate in atrial fibrillation (AF) are not well understood. We hypothesized that these can be detected by AF electrograms and magnetic resonance imaging parametric mapping.

Methods And Results: AF was induced in 43 dogs (25-35 kg, ≥1 year) by rapid atrial pacing (RAP) (3-33 weeks, 600 beats/min), and 4 controls were used.

Regions of Highly Recurrent Electrogram Morphology With Low Cycle Length Reflect Substrate for Atrial Fibrillation.

Traditional anatomically guided ablation and attempts to perform electrogram-guided atrial fibrillation (AF) ablation (CFAE, DF, and FIRM) have not been shown to be sufficient treatment for persistent AF. Using biatrial high-density electrophysiologic mapping in a canine rapid atrial pacing model of AF, we systematically investigated the relationship of electrogram morphology recurrence (EMR) (Rec% and CL) with established AF electrogram parameters and tissue characteristics. Rec% correlates with stability of rotational activity and with the spatial distribution of parasympathetic nerve fibers.

Recent advances in gene therapy for atrial fibrillation.

Atrial fibrillation (AF) is the most common heart rhythm disorder in adults and a major cause of stroke. Unfortunately, current treatments for AF are suboptimal as they are not targeting the molecular mechanisms underlying AF. In this regard, gene therapy is emerging as a promising approach for mechanism-based treatment of AF.

Activation During Sinus Rhythm in Ventricles With Healed Infarction: Differentiation Between Arrhythmogenic and Nonarrhythmogenic Scar.

Background: In infarct-related ventricular tachycardia (VT), the circuit often corresponds to a location characterized by activation slowing during sinus rhythm (SR). However, the relationship between activation slowing during SR and vulnerability for reentry and correlation to components of the VT circuit are unknown. This study examined the relationship between activation slowing during SR and vulnerability for reentry and correlated these areas with components of the circuit.

Modulating the Baseline Impedance: An Adjunctive Technique for Maximizing Radiofrequency Lesion Dimensions in Deep and Intramural Ventricular Substrate: An Adjunctive Technique for Maximizing Radiofrequency Lesion Dimensions in Deep and Intramural Ventricular Substrate.

Background Radiofrequency ablation of intramural ventricular substrate is often limited by insufficient tissue penetration despite high energy settings. As lesion dimensions have a direct and negative relationship to impedance, reducing the baseline impedance may increase the ablation effect on deep ventricular tissue. Methods This study included 16 patients with ventricular tachycardia or frequent ventricular premature complexes refractory to ablation with irrigated catheters.

Expandable Lattice Electrode Ablation Catheter: A Novel Radiofrequency Platform Allowing High Current at Low Density for Rapid, Titratable, and Durable Lesions.

Background: High-current short-duration radiofrequency energy delivery has potential advantages for cardiac ablation. However, this strategy is limited by high current density and narrow safety-to-efficacy window. The objective of this study was to examine a novel strategy for radiofrequency energy delivery using a new electrode design capable of delivering high power at a low current density to increase the therapeutic range of radiofrequency ablation.

A novel octaray multielectrode catheter for high-resolution atrial mapping: Electrogram characterization and utility for mapping ablation gaps.

Introduction: Multielectrode mapping catheters improve the ability to map within the heterogeneous scar. A novel Octaray catheter with eight spines and 48 electrodes may further improve the speed and resolution of atrial mapping. The aims of this study were to (1) establish the Octaray's baseline mapping performance and electrogram (EGM) characteristics in healthy atria and to (2) determine its utility for identifying gaps in a swine model of atrial ablation lines.

Effect of Baseline Impedance on Ablation Lesion Dimensions: A Multimodality Concept Validation From Physics to Clinical Experience.

Background: Radiofrequency ablation using irrigated catheters is performed using a power-controlled mode. However, lesion size is dependent on current delivery at a particular impedance, such that a power value alone may not reflect actual energy delivery, resulting in lesion size variability at similar power settings. We hypothesized that modulating baseline impedance at fixed power settings affects ablation lesion dimensions.

Infarct-Related Ventricular Tachycardia: Redefining the Electrophysiological Substrate of the Isthmus During Sinus Rhythm.

Objectives: In this study, the scientific objective was to characterize the electrophysiological substrate of the ventricular tachycardia (VT) isthmus during sinus rhythm.

Background: The authors have recently described the electrophysiological characteristics of the VT isthmus using a novel in vivo high-resolution mapping technology.

Methods: Sixteen swine with healed infarction were studied using high-resolution mapping technology (Rhythmia, Boston Scientific, Cambridge, Massachusetts) in a closed-chest model.

Nearly asymptomatic left ventricular apical ballooning after a hit-and-run accident.

Tako-tsubo cardiomyopathy is a syndrome that mimics acute myocardial infarction consisting of typical chest pain with acute onset and transient left ventricular wall-motion abnormalities. We present a case of a 53-year-old woman with nearly asymptomatic apical ballooning after a hit-and-run car accident. No blunt force impact occurred over the precordial area.