Chapter 22

### INTRODUCTION

One of the most important discoveries in clinical electrophysiology has been the recognition of the importance of the pulmonary veins (PVs) in the initiation and maintenance of atrial fibrillation (AF). AF is the most common sustained cardiac arrhythmia seen in clinical practice and is associated with significant morbidity and mortality. Other atrial arrhythmias originating from the PVs include premature atrial contractions and ectopic atrial tachycardia. Because it is established that the PVs play a crucial role in the genesis and maintenance of AF, the electrical isolation of PVs has become the cornerstone for the treatment of this arrhythmia.

Over the past decade, the PV has been the focus of extensive research, and tremendous new insights have occurred with important clinical application. Morphologic studies have demonstrated the presence of complex anatomic and three-dimensional organization of myocardial clusters extending from the left atrium (LA) into the proximal PV.1,2,3 Basic research studies have found the PVs to be the source of ectopic beats for the initiation of paroxysmal AF (PAF) and foci of ectopic atrial tachycardia.4,5,6 Several studies have also suggested the role of PVs in maintenance of AF.7,8 Experimental models have been developed to study the precipitating factors for enhancing PV arrhythmogenesis.9,10 Electrophysiologic studies have shown that the underlying arrhythmogenic nature of PVs is caused by a combination of reentrant and nonreentrant mechanisms.11,12,13 Studies using advanced imaging and mapping techniques have provided the road map for successful ablation therapy, both surgical and catheter based.14,15

### HISTORICAL PERSPECTIVE

AF is the most common of all sustained abnormal heart rhythms and has the longest diagnostic history. William Einthoven published the first electrocardiogram (ECG) demonstrating AF in 1906. One hundred years later, we better understand the initiation and persistence of AF. The first Cox maze surgery for curative treatment of AF was performed in 1987. The cut-and-sew surgery included cutting the posterior LA and the attached PVs and then reattaching them to electrically isolate the PVs from the atrium. By 1992, improvements in the surgery led to the development of the Cox maze III, which is now considered the most effective surgical cure for AF. As the Cox maze procedure evolved, so did catheter-based approaches for the treatment of AF. In 1994, a trial of multiple linear burns with an ablation catheter by way of a transseptal puncture was undertaken. PV stenosis, a new and difficult-to-treat complication from catheter ablation, was unfortunately identified. This complication led to a complete abandonment of catheter-based ablation with long linear burns for the treatment of AF. Soon afterward, the association of frequent premature atrial contractions and the development of AF was noted. These focal atrial triggers were found to consistently originate from the PVs in most patients, which led to the return of catheter ablation for the treatment ...

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