Rachael Chaska, Enola Okonkwo, Maram Bishawi, Bryan Hyman

A 32-year-old male with a history of remote repair of Tetralogy of Fallot, presented to the emergency department with chest pressure, pre-syncope, and headache.  In the emergency department, he was found to have an epsilon wave on electrocardiogram prompting electrophysiology consult.  Subsequently, he was found to have inducible ventricular arrhythmia warranting implantation of a cardioverter defibrillator. The epsilon wave is most commonly associated with arrhythmogenic right ventricular cardiomyopathy but can be seen in a variety of conditions associated with increased risk of life threatening arrythmia.

INTRODUCTION

The epsilon wave is a delayed depolarization found between the QRS and ST segment.  It was described by Fontaine et al. in 1973 as a low amplitude post-excitation wave secondary to structural heart disease, namely arrythmogenic right ventricular cardiomyopathy (ARVC). Recognizing this ECG finding is essential for emergency physicians because of the increased risk of life-threatening arrhythmias.

CASE DESCRIPTION

A 32-year-old male with a history of diabetes, repaired Tetralogy of Fallot (rTOF), and prior syncopal episodes presented to the emergency department after experiencing chest pressure, lightheadedness, generalized weakness, and near syncope. There was no reported loss of consciousness or head trauma but a gradually worsening headache.

Initial ED vitals were within normal limits. Physical exam was notable for generalized weakness without focality and a grade II systolic murmur at the right lower sternal border. A CT head, CXR, and laboratory tests (table 1) were unremarkable.

The ECG was interpreted by the ED physician as a right bundle branch pattern with epsilon waves and inverted T-waves in the anterior leads. In the setting of pre-syncope, electrophysiology was consulted and the patient was admitted for cardiogenic syncope.

Echocardiogram showed normal left and right heart function with mild to moderate tricuspid and pulmonary regurgitation. Pulmonary artery peak pressures were normal. Cardiac MRI showed no evidence of infiltrative disease, infarct, or inflammation of the ventricles.  A prominent ligamentum arteriosum without evidence of shunt and a 9mm x 3mm crypt was seen in the inferioseptal left ventricle. MRI brain ruled out intracranial etiologies.

The patient was taken to the EP lab and underwent ventricular extrastimulation leading to inducible sustained ventricular tachycardia (VT) requiring external defibrillation.  He subsequently underwent implantation of cardioverter defibrillator (ICD). The remainder of patient’s hospital course was uncomplicated. 

Discussion

The ECG is a valuable diagnostic tool for patients presenting with syncope.  Emergency physicians must recognize the epsilon wave and understand the potential for these patients to experience life threatening arrhythmia. Epsilon waves are characterized as abnormal depolarizations occurring between the end of a QRS complex and the beginning of a T wave. The cause of this electrical signal is due to the impeded conduction within the ventricular myocardium, inducing post-excitation of the myocytes in the ventricle [1]. The epsilon wave is traditionally seen in ARVC secondary to fibro-fatty changes within the right ventricle, but epsilon waves have been reported in cardiac sarcoidosis, Brugada Syndrome, right ventricular myocardial infarction, and Tetralogy of Fallot [1–7].

Emergency physicians are developing greater familiarity with the epsilon wave and associate it with ARVC.  ARVC is responsible for nearly 20% of cardiac deaths in patients under 35 [8] and is the most common cause of sudden cardiac death in Italian athletes [9].  The prevalence of ARVC is estimated to be 1/5000 patients [10]. Epsilon waves are usually noted in the right pericardial leads, but patients may also have left sided or more diffuse ECG involvement [1].  The degree of ECG abnormalities appears to correlate with disease severity and provides prognostic value [11,12].

This case is interesting as it demonstrates an epsilon wave in a patient with rTOF without typical ARVC structural abnormalities such as a dilated RV, myocardial infiltration, or regional wall motion abnormality.  Despite the normal RV seen on echo and MRI, this patient was experiencing life threatening arrhythmias likely originating from scar tissue related to his rTOF. rTOF patients with monomorphic VT have been shown to have arrhythmogenic slow conducting cardiac isthmuses [13].

Known risk factors for VT in rToF patients include older age at repair and assessment, QRS ≥180ms, low QRS vector magnitude, RV hypertrophy, and RV mass:volume ≥0.3 g/mL [14–16].  The presence of epsilon waves in these patients is not well studied or common.  It is possible that the presence of the epsilon wave may be obscured by the RBBB pattern [17].  Presence of an epsilon wave in rTOF may represent a subset of rToF patients at increased risk of arrhythmia. One case report describes a patient with rToF and epsilon wave who had resolution of both VT and epsilon wave with ablation [7].

The epsilon wave represents a significant ECG abnormality and in the right clinical context, an EP consult is warranted.  As physicians become more astute at recognizing the epsilon wave it is likely that additional etiologies for this ECG abnormality will be reported and further data will be needed to clarify which patients are at highest risk of adverse outcomes. Cardiac MRI is generally recommended as part of the evaluation.  ICD placement is often the preventative treatment of choice for patients with inducible ventricular arrhythmias.     

disclosures

The authors have no conflicts of interests.

References

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about the authors

Rachael Chaska, is a 4th year medical student at the University of South Florida Select Program based in Pennsylvania. She is a former paramedic and plans to enter an Emergency Medicine residency program following graduation. Dr. Okonkwo is the Assistant Program Director at USF Emergency Medicine. Dr. Maram Bishawi is an Attending Physician at Tampa General Hospital. She is a former graduate of USF Emergency Medicine Residency Program. Dr. Bryan Hyman is currently a PGY 3 resident at USF EM and serves as the Academic Chief Resident.