Epsilon Waves During Ventricular Tachycardia in a Case of Arrhythmogenic Right Ventricular Dysplasia
Epsilon waves represent delay in depolarization of the right ventricular (RV) free wall and outflow tract in patients with arrhythmogenic RV dysplasia. Normally, the free wall of the RV is the last part of the heart to undergo depolarization.1 If there is selective damage of the RV free wall, the ECG may show features of delayed and anisotropic conduction in that region, which are most pronounced in the anterior chest leads. Epsilon waves are low amplitude and are visible only on the ECG leads overlying the RV.2
This is the case of a 46-year-old man who was resuscitated after cardiac arrest caused by sustained monomorphic ventricular tachycardia (VT). Cardiac magnetic resonance imaging showed a dilated RV with fatty infiltration of the RV free wall with mild RV dysfunction. A mural dissection of the interventricular septum was also noted in the magnetic resonance imaging (Figure 1A). Computed tomography angiography demonstrated an aneurysmal area in the RV outflow region (Figure 1B). His baseline ECG showed incomplete right bundle-branch block, T-wave inversions in leads V1 to V3, and a small epsilon wave in the anterior chest leads (Figure 2).
The patient received a single-chamber implantable cardioverter-defibrillator (St. Jude Medical Inc., St. Paul, Minn.) and antiarrhythmic therapy with amiodarone. Later, he presented with multiple implantable cardioverter-defibrillator discharges related to VT. His amiodarone dose was increased, but he continued to be in slow VT with features of congestive heart failure. ECG of the slow VT showed epsilon waves in anterior chest lead V1 (Figure 3).
Mapping and ablation of the VT with CARTO™ (Biosense Webster Inc., Diamond Barr, CA) mapping of the RV was performed. A voltage map showed a large area of scar on the RV inferior free wall (Figure 4). Activation mapping demonstrated the tachycardia exit point in the mid inferior wall of the RV (Figure 5). The area demonstrated fragmented diastolic potentials, and ablation of this region terminated the tachycardia. To modify the substrate, a linear ablation line was created to meet the tricuspid annulus. After ablation, no VT was inducible; over a follow-up of 4 years, the patient has had no further implantable cardioverter-defibrillator therapies. Slower VTs in the monitoring zone of the implantable cardioverter-defibrillator were documented.
Epsilon waves are typically seen in sinus-rhythm ECGs in patients with arrhythmogenic RV dysplasia. It is unusual to see epsilon waves during VT because most of the tachycardias in arrhythmogenic RV dysplasia exit from the triangle of dysplasia with early activation occurring in the RV myocardium. However, they may be seen in rare cases when extensive disease of the RV free wall causes extremely slow activation in that region.
The reported ECG prevalence of epsilon waves in arrhythmogenic RV dysplasia ranges from 4% to 29% in various series.3 Demonstration of epsilon waves during VT is rare.
The presence of epsilon waves during VT probably indicates delayed activation of the RV free wall and outflow tract region because of extensive disease. Although the VT is exiting from the RV free wall, scarring and fibrosis of the nearby RV myocardium cause conduction delay and result in fragmented potentials in endocardial mapping and epsilon waves in surface ECGs and signal-averaged ECGs.
- © 2010 American Heart Association, Inc.
- McKenna WJ,
- Thiene G,
- Nava A,
- Fontaliran F,
- Blomstrom-Lundqvist C,
- Fontaine G,
- Camerini F
- Hamid MS,
- Norman M,
- Quraishi A,
- Firoozi S,
- Thaman R,
- Gimeno GR,
- Sachdev B,
- Rowland E,
- Elliot PM,
- McKenna WJ