High-resolution/Density Mapping in Patients with Atrial and Ventricular Arrhythmias

High density mapping of complex atrial tachycardia in patients after cardiac surgery

To provide an overview of the current application of high-density mapping (HDM) in the mechanism of complex atrial tachycardias (ATs). Complex ATs are frequently scar-related, after history of previous cardiac surgery and large scars. These scar-related ATs are difficult to manage medically and frequently recur after electrical cardioversion. HDM technologies have enabled rigorous elucidation of AT mechanisms in patients post cardiac surgery. This article showed the application of HDM technology in complex ATs from the mechanisms of complex ATs, the development of HDM technology, and the identification of scars or critical isthmus from HDM. HDM-guided approach is highly effective for identifying the ATs mechanism and critical isthmus.

SANS FLUORO Too Big to Fail

We present the first ever reported case of a super morbidly obese patient (BMI > 60) with drug refractory, symptomatic persistent atrial fibrillation who underwent an uncomplicated, but unsuccessful PVI ablation procedure and subsequently underwent AV node ablation and cardiac resynchronization therapy - pacemaker (CRT-P) insertion using a zero fluoroscopy technique. This case demonstrates the following two critical points: (1) difficulties in the treatment of massively obese patients with arrhythmias1; (2) increased use of fluoroless procedures2-4.

High density mapping guided partial antral ablation for a pulmonary vein isolation

The muscular discontinuities at the pulmonary vein (PV)–left atrial (LA) junction are known. The high-density mapping may help to find the muscular discontinuity. This study evaluated the efficacy of a partial antral ablation for a pulmonary vein (PV) isolation using high density (HD) mapping. A total of 60 drug-refractory atrial fibrillation (AF) patients undergoing catheter ablation were enrolled. The detailed activation mapping of each PV and LA junction was performed using an HD mapping system, and each PV segment’s activation pattern was classified into a “directly-activated from the LA” or “passively-activated from an adjacent PV segment” pattern. The antral ablations were performed at the directly-activated PV segments only when the PV had “passively-activated segments”. If the PV did not contain passively-activated segments, a circumferential antral ablation was performed on those PVs. A “successful partial antral ablation” was designated if the electrical isolation of targeted PV was achieved by ablation at the directly-activated segments only. If the isolation was not achieved even though all directly-activated segments were ablated, a “failed partial antral ablation” was designated, and then a circumferential ablation was performed. Among 240 PVs, passively-activated segments were observed in 140 (58.3%) PVs. Both inferior PVs had more passively-activated segments than superior PVs, and the posteroinferior segments had the highest proportion of passive activation. The overall rate of successful partial antral ablation was 85%. The atrial tachyarrhythmia recurrence was observed in 10 patients (16.7%) at 1-year. HD mapping allowed the evaluation of the detailed activation patterns of the PVs, and passively-activated segments may represent muscular discontinuity. Partial antral ablation of directly-activated antral segments only was feasible and effective for a PVI.

P-Wave Morphology in Focal Atrial Tachycardia: An Updated Algorithm to Predict Site of Origin

OBJECTIVES

This study sought to report P-wave morphology (PWM) from a series of paraseptal (PS) atrial tachycardia (AT), revise then prospectively evaluate a simplified PWM algorithm against a contemporary consecutive cohort with focal AT.

BACKGROUND

The 2006 PWM algorithm was useful in predicting the origin of focal AT. An updated algorithm was developed given advances in multipolar 3-dimensional mapping, potential limitations of PWM in separating PS sites, and a renewed interest in the P-wave in mapping non-pulmonary vein triggers.

METHODS

The PWM from a consecutive series of 67 patients with PS AT were analyzed. PS sites included were coronary sinus ostium, perinodal, left and right septum, septal tricuspid annulus, superior mitral annulus, and noncoronary cusp. Next the P-wave algorithm was revised and prospectively evaluated by 3 blinded assessors.

RESULTS

The P-wave for PS sites was neg/pos (n = 50), iso/pos (n = 10), or isoelectric (n = 4) in lead V₁ (96%). The P-wave algorithm was modified and prospectively applied to 30 consecutive patients with focal AT who underwent successful ablation. Foci (n = 30) originated from the right atrium (33.3%), left atrium (30%), and PS (36.7%). Using the PW algorithm, the correct anatomic location was identified in 93%. Incorrect interpretation of the terminal positive P-wave component (n = 3) and initial negative P-wave deflection (n = 1) in lead V₁ misidentified 4 paraseptal cases.

CONCLUSIONS

The revised PWM algorithm offers a simplified and accurate method of localizing the responsible site for focal AT. The P-wave remains an important first step in mapping atrial arrhythmias.

Dielectric imaging for electrophysiology procedures: The technology, current state, and future potential

Electroanatomic mapping systems have become an essential tool to guide the identification and ablation of arrhythmic substrate. Recently, a novel guiding system for electrophysiology procedures was introduced that uses dielectric sensing to perform high resolution anatomical imaging. Dielectric imaging systems use electrical fields to differentiate anatomic structures based on their conductivity and permittivity. This technique enables non-fluoroscopic, noncontact mapping of anatomic structures, assessment of pulmonary vein occlusion state during cryoballoon ablation, and has the potential to assess for additional tissue characterization including tissue thickness and tissue type. This article elaborates on the functioning and potential of dielectric imaging systems and provides two cases to illustrate the clinical impact for electrophysiology procedures.

The Ideal Cardiac Mapping System

Cardiac mapping has witnessed significant and unprecedented progress over more than a century. At present, several mapping/imaging technologies are commercially available, alone or in combination. This article briefly discusses the advantages and limitations (disadvantages) of each technique.

Historical Perspectives on Cardiac Mapping and Ablation

Cardiac mapping has evolved from single point-by-point registration of cardiac electrical activity to its utmost real-time multimodality of mapping and imaging for catheter ablation of arrhythmias. The technology began with electrocardiogram recordings and evolved to the simultaneous registration of depolarization and repolarization using optical mapping and real-time multimodality imaging. Zero to near-zero fluoroscopy is currently used in practice to avoid radiation exposure. Real-time noninvasive mapping, imaging, and ablation of arrhythmias are in use in practice. We present the contemporary up-to-date progress on the role of cardiac mapping and imaging in the diagnosis and management of cardiac arrhythmias.