Atrial Fibrillation in the Wolff-Parkinson-White Syndrome

Abstract

Since the advent of catheter ablation for atrial fibrillation (AF) aiming the pulmonary veins a few years ago, there has been an overwhelming interest and a dramatic increase in AF investigation. AF has a different dimension in the context of the Wolff-Parkinson-White (WPW) syndrome. Indeed, AF may be a nightmare in a young person that has an accessory pathway (AP) with fast anterograde conduction. It may be life-threatening if an extremely rapid ventricular response develops degenerating into ventricular fibrillation. Therefore, it is very important to know the mechanisms involved in the development of AF in the WPW syndrome. There are several possible mechanisms that may be involved in the development of AF in the WPW syndrome, namely, spontaneous degeneration of atrioventricular reciprocating tachycardia into AF, the electrophysiological properties of the AP, the effects of AP on atrial architecture, and intrinsic atrial muscle vulnerability. Focal activity, multiple reentrant wavelets, and macroreentry have all been implicated in AF, perhaps under the further influence of the autonomic nervous system. AF can also be initiated by ectopic beats originating from the pulmonary veins, and elsewhere. Several studies demonstrated a decrease incidence of AF after successful elimination of the AP, suggesting that the AP itself may play an important role in the initiation of AF. However, since AF still occurs in some patients with the WPW syndrome even after successful ablation of the AP, there should be other mechanisms responsible for the development of AF in the WPW syndrome. There is a clear evidence of an underlying atrial muscle disease in patients with the WPW syndrome. Atrial myocardial vulnerability has been studied performing an atrial endocardial catheter mapping during sinus rhythm, and analizing the recorded abnormal atrial electrograms. This review analizes the available data on this singular setting since AF has a reserved prognostic significance in patients with the WPW syndrome, and has an unusually high incidence in the absence of any clinical evidence of organic heart disease.

Figure 1. Atrial fibrillation in the Wolff-Parkinson-White syndrome

12 lead electrocardiographic recording in a patient with induced atrial fibrillation in the manifest Wolff-Parkinson-White syndrome. There is an evident very rapid ventricular rate. Reprinted with permission from Avalos Morel P, Centurión OA, Bianco Cáceres HF et al. Rev Soc Parag Cardiol 2005;2:159-168.

Figure 2. Atrial endocardial mapping sites

The upper part of the figure shows 12 endocardial mapping sites in the right atrium. The atrial endocardial electrograms were recorded in each patient from the anterior, lateral, posterior and medial aspects of the high right atrium (a,b,c,d), mid right atrium (e,f,g,h) and low right atrium (i,j,k,l). SVC= superior vena cava; IVC= inferior vena cava; Ao= aorta; PA= pulmonary artery; LA= left atrium; RV= right ventricle; LV= left ventricle. The lower part of the figure show 2 atrial endocardial electrograms to distinguish an abnormal atrial electrogram (A) with 10 fragmented deflections and 130 ms in duration, from a normal atrial electrogram (B) with 2 deflections and 80 ms in duration. Reprinted with permission from Centurion OA et al. Influence of advancing age on fractionated right atrial endocardial electrograms. Am J Cardiol 2005;96:239-242.

Figure 3. Induction of fragmented atrial activity (FAA)

An example of the induction of fragmented atrial activity (FAA) as defined in the text. Surface electrocardiographic lead V1 is shown together with intracardiac electrograms from the high lateral right atrium (HLRA), and distal coronary sinus (CSd). S1 and S2 are, respectively, the driving and premature stimulus artifacts. The basic drive cycle length (BCL) was 500 ms and the coupling interval (S1 S2 interval) was 230 ms. There is a prolongation of the duration of atrial activity from 110 to 200 ms in the HLRA. CD indicates interatrial conduction delay. Reprinted with permission from Konoe A, Fukatani M, Tanigawa M, et al. Electrophysiological abnormalities of the atrial muscle in patients with manifest Wolff-Parkinson-White syndrome associated with paroxysmal atrial fibrillation. PACE 1992;15:1040-1052.

Figure 4. Induction of interatrial conduction delay (CD)

Atrial extrastimulus testing in a patient with paroxysmal AF showing atrial conduction delay (CD). S1 and A1 refer to the driving stimulus and the atrial electrogram, respectively, of the basic drive beat. S2 and A2 refer to the stimulus artifact and the atrial electrogram, respectively, of the induced premature beat. The atrial extrastimulus was programmed at a coupling interval of 190 ms with a driving cycle length of 500 ms. The S1-A1 interval in the distal coronary sinus was 135 ms. At the premature beat, S2-A2 interval prolonged to 230 msec. The maximum CD in this patient was 95 msec. This atrial CD led to repetitive atrial firing (RAF). HRA indicates high right lateral atrium; RAA, right atrial appendage; HBE, His bundle area; and CSd, distal coronary sinus. Reprinted with permission from Isomoto S, Centurión OA, Shibata R, et al. The effects of aging on the refractoriness and conduction of the atrium in patients with lone paroxysmal atrial fibrillation revealed with programmed atrial stimulation. Rev Soc Parag Cardiol 2005;3:25-30.

Figure 5. Induction of repetitive atrial firing (RAF)

An example of the induction of repetitive atrial firing (RAF) as defined in the text. Surface electrocardiographic lead V1 is shown together with intracardiac electrograms from the high lateral right atrium (HLRA), and distal coronary sinus (CSd). S1 and S2 are, respectively, the driving and premature stimulus artifacts. The basic drive cycle length (BCL) was 500 ms and the coupling interval (S1 S2 interval) was 230 ms. Reprinted with permission from Konoe A, Fukatani M, Tanigawa M, et al. Electrophysiological abnormalities of the atrial muscle in patients with manifest Wolff-Parkinson-White syndrome associated with paroxysmal atrial fibrillation. PACE 1992;15:1040-1052.

Figure 6. Normal atrial endocardial electrograms

Examples of measurement of the duration (top), and the number of deflections (bottom) of the intraatrial electrogram. Surface electrocardiographic lead V1 is shown together with the right atrial electrogram (RA). In the top panel, the arrows show the onset and the end of the intraatrial electrogram. In the bottom panel, the arrows show the deflections of the intraatrial electrograms. Reprinted with permission from Konoe A, Fukatani M, Tanigawa M, et al. Electrophysiological abnormalities of the atrial muscle in patients with manifest Wolff-Parkinson-White syndrome associated with paroxysmal atrial fibrillation. PACE 1992;15:1040-1052.

Figure 7. Abnormally prolonged and fractionated atrial endocardial electrogram

Example of an “abnormal atrial electrogram”. This abnormal atrial electrogram was recorded from high lateral right atrium (RA). Abnormal atrial electrogram as defined in the text. Reprinted with permission from Konoe A, Fukatani M, Tanigawa M, et al. Electrophysiological abnormalities of the atrial muscle in patients with manifest Wolff-Parkinson-White syndrome associated with paroxysmal atrial fibrillation. PACE 1992;15:1040-1052.