Atrial fibrillation I: a new classification system

See related editorial on page 1693. I n the past, many relatively simple electrophysiologic concepts were made to seem complex because of the confusing and inconsistent terminology used to describe them. For example, the terms nonuniform refractoriness, inhomogeneous recovery, nonuniform repolarization, dispersion of refractoriness, and desynchronized repolarization all refer to the same electrophysiologic abnormality. We are now facing a similar problem with atrial fibrillation. Previously, atrial fibrillation could be treated within acceptable standards by physicians who possessed only a superficial understanding of the arrhythmia itself because the only options for treatment were rhythm-control or rate-control drugs. However, the recent introduction of surgical and catheter interventional treatment for atrial fibrillation has changed the requirements for therapeutic competence and, as a result, has generated the usual bewildering terminology that occurs when an entity is poorly understood and has no accurate classification system. The confusing terminology surrounding atrial fibrillation has resulted in faulty concepts, unsound treatment schemes, and misleading claims regarding the results of interventional therapy. This problem stems primarily from the vague meaning and multiple uses of the term chronic. The descriptors paroxysmal and chronic have traditionally been used to characterize atrial fibrillation clinically, although their precise meaning has never been clarified. Most authors, including this one, have used the term paroxysmal to denote episodic or intermittent atrial fibrillation and the term chronic to denote continuous, unrelenting atrial fibrillation, both terms being applied without regard to how long the patient had the fibrillation. Recently, however, the term chronic has been used to describe atrial fibrillation of long duration, regardless of whether the atrial fibrillation is intermittent or continuous. Because chronic in other areas of medicine means long standing, it is understandable that the term has evolved to describe long-standing atrial fibrillation. However, because chronic, when applied to atrial fibrillation, has traditionally meant continuous, its new use has led to an unfortunate and potentially dangerous confusion regarding the results of various types of interventional therapy. Moreover, our cardiology colleagues have recently proposed a new classification system for atrial fibrillation that includes the additional terms persistent and permanent, which, unfortunately, do not describe unique electrophysiologic characteristics and therefore only serve to cloud the issue further. The optimal treatment of atrial fibrillation depends on a proper understanding of the electrophysiologic basis of each of its clinical manifestations. It is fortuitous that in the case of atrial fibrillation, both its clinical manifestation and its proper interventional treatment are dictated by its underlying electrophysiology. Unfortunately, accuracy in diagnosis and interventional treatment are impossible using terms such as chronic, paroxysmal, persistent, and permanent to characterize atrial fibrillation because these terms do not discriminate between the different types of atrial fibrillation, and they also mean different things to different people. The confusion in diagnosis (and therefore in the subsequent reporting of interventional results) caused by this contemporary terminology can be illustrated in the following hypothetical cases. Suppose that a patient has had multiple, recurrent, self-terminating bouts of atrial fibrillation for the past 25 years despite medical therapy and several unsuccessful electrical cardioversion attempts. Is this chronic atrial fibrillation because it has been present for a long time? Is it paroxysmal atrial fibrillation because it is intermittent in nature? Is it persistent atrial fibrillation because it persists despite medical therapy From the Division of Cardiothoracic Surgery, Washington University School of Medicine, St Louis, Mo.