Editorial (Thematic Issue: Focal Atrial Tachycardias and Atrial Flutter: Are they Hot Enough to Make a Thematic Issue?)

Abstract

Focal atrial tachycardias and atrial flutter represent a considerable part of the arrhythmias treated by electrophysiologists worldwide. Antiarrhythmic drug therapy might control these arrhythmias. Unfortunately, in many cases this therapy is fraught with side effects or ar-rhythmias recur. With the advent of invasive electrophysiology, an increasing number of these substrates are becoming amenable to catheter ablation. This makes catheter ablation the better alternative of medical therapy and is therefore recommended by the currently accepted guide-lines [1]. Despite the great advance in our understanding of these arrhythmias, there are still questions that remain and issues that have not been fully elucidated. This thematic issue focuses on important points and problems in the management of atrial tachycardias and flutter with specific emphasis on the challenges electrophysiologists are facing during planning and carrying out catheter ablation. Surface P wave during tachycardia is a classical tool to aid exact diagnosis and help plan the ablation strategy in cases of focal atrial tachycardias and atrial flutter. Looking at the surface ECG in an attempt to define the P wave morphology and try to pinpoint the focus loca-tion is probably the most routine thing an electrophysiologist would do before undertaking electrophysiological study and catheter ablation. But is the ECG the most accurate way to help us plan our procedure in advance? Many groups have attempted to find the best way to predict the location of atrial ectopic foci based on P wave morphology on surface ECG [2]. A detailed review of the different algorithms based on P wave morphology is presented by Lee and Fynn in the current thematic issue [3]. The matter has been presented in a very systematic way with links to arrhythmia mechanisms and specific patterns of interatrial conduction that might explain the observed morphology of P waves. The reader is drawn to the natural conclusion that P wave morphology is an important classical tool. However, there are numerous limitations of ECG that preclude its use as a sole method to guide the ablation approach. One of these limitations is spatial resolution of surface ECG that does not exceed 17 mm according to published data [4]. This makes the method inaccurate in defining the focus location in potentially ar-rhythmogenic areas located close to each other [5]. In those cases intracardiac mapping should solve the case. However when foci arise at or close to the interatrial septum biatrial mapping is frequently required. This comes with all the inherent risks of transseptal puncture. The re-view by Traykov looks into the available techniques and maneuvers to predict the chamber of origin in focal atrial tachycardias demonstrating earliest activation at the interatrial septum [6]. Most of these are based on analysis of timing, sequence and morphology of intracardiac elec-trograms during tachycardia. A very interesting approach described in detail in the paper by Traykov is the analysis of the morphology of the earliest electrogram recorded from the right atrial septum or proximal to middle coronary sinus. The review presents interesting evidence that electrograms from these zones are double or fragmented and consist of two components -a far-field component representing activation of the left atrial septal aspect and a near-field component arising from the activation of the right atrial septal aspect. The sequence of these compo-nents can be used to determine the chamber of origin of focal atrial tachycardias. The results from this approach coming from different inves-tigators have been nicely summarized in this review paper emphasizing the fact that chamber of origin of these tachycardias is possible to be determined with high diagnostic accuracy without the need for biatrial mapping. Atrial tachycardias foci tend to cluster in specific atrial regions. For the right atrium the structures that most frequently exhibit ectopic activity are crista terminalis, coronary sinus os and tricuspid annulus. In the left atrium foci tend to cluster to the pulmonary veins and the mitral annulus. Other more infrequent but increasingly recognized foci locations are the left and right atrial appendages and the aortic root [7-9]. In this thematic issue the paper by Taylor et al. provides a very interesting review of the electrophysiological characteristics of foci from these locations [10]. Frequently referring to important anatomical facts and considerations it also provides an update to the ablation approach in these cases.