Learning Objectives

After completing this lesson, you should be able to:

1. What Is an Epsilon Wave?

An epsilon wave is a small, low-amplitude deflection recorded immediately after the end of the QRS complex and before the onset of the ST segment. It is classically sought in the right precordial leads, particularly V1–V3. Depending on the tracing and recording method, it may appear as a subtle notch, a brief spike, or a low-amplitude oscillation.

Figure 1. Actual ECG example in V1. The epsilon wave is the small, low-amplitude deflection immediately following the main QRS complex (arrow), before the ST segment.

Proposed electrophysiological basis

The traditional explanation is delayed activation of portions of the right ventricular myocardium. In arrhythmogenic cardiomyopathy, myocardial injury and fibrous replacement may create regions of slow or discontinuous conduction. The resulting delayed electrical activity can appear as a small signal after the principal ventricular depolarization.

The exact appearance depends on the distribution of myocardial disease, lead orientation, recording technique, and ECG filtering. A subtle terminal signal should therefore be assessed carefully and reproducibly.

2. Where and How to Identify It

On a standard 12-lead ECG, inspect the terminal portion of the QRS complex and the early ST segment in V1, V2, and V3. The supplied LITFL reference describes the finding most often in the right precordial leads, with occasional visibility in other leads.

Examples of epsilon-wave morphology

Figure 2. Examples of subtle epsilon-wave patterns: a wiggle-wave morphology, a small positive spike, a small negative spike, and a terminal deflection in V1. The arrows identify the small terminal signals. These examples illustrate morphological variation rather than a diagnostic grading scale.

Figure 3. Additional example in lead II showing a subtle low-amplitude deflection at the end of the QRS complex (arrow). Epsilon waves are classically sought in V1–V3; examples in other leads may occur.

How to read these examples

Look for a discrete, reproducible low-amplitude signal at the terminal QRS / immediately post-QRS region. It may be upright, downward, or appear as a small oscillation. Do not mistake a large R′ wave, a broad QRS complex, baseline artefact, or an ordinary notch within the QRS for an epsilon wave.

3. Association With Arrhythmogenic Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC), within the broader spectrum of arrhythmogenic cardiomyopathy, is characterized by ventricular myocardial disease and a propensity to ventricular arrhythmias. The right ventricle is commonly involved, although left ventricular or biventricular disease can also occur.

An epsilon wave may provide a clue to delayed right ventricular activation. However, it is not a stand-alone diagnosis, and its absence does not exclude ARVC. The 2023 ESC cardiomyopathy guideline specifically cautions that epsilon waves are often overcalled, show poor interobserver agreement, and should be used cautiously for diagnostic purposes.

Other ECG features that may support suspicion

• T-wave inversion in the right precordial leads, especially V1–V3, interpreted according to age and the presence or absence of complete right bundle branch block.
• Prolonged terminal activation duration in V1–V3 in the absence of complete right bundle branch block.
• Ventricular ectopy or ventricular tachycardia with a left bundle branch block morphology, suggesting a right ventricular origin.
• Low QRS voltages or other conduction/repolarization abnormalities in the appropriate clinical context.

These findings must be integrated with personal and family history, ambulatory rhythm monitoring, cardiac imaging (particularly echocardiography and cardiac magnetic resonance), and genetic or other investigations when indicated.

4. Fontaine Leads: An Alternative Recording Configuration

Fontaine bipolar precordial leads (F-ECG) were developed to emphasize electrical potentials arising from the right ventricle. The configuration changes the electrode connections to create three bipolar chest leads, designated FI, FII, and FIII.

With this arrangement, the ECG machine records three bipolar leads (FI, FII, and FIII) rather than the usual limb leads I, II, and III. The vertical FI lead is described as particularly useful for displaying epsilon potentials and may also help visualize atrial activity in selected circumstances.

5. A Practical ECG Review Approach

1. Confirm the tracing quality.
   Check calibration, baseline stability, electrode placement, and filtering. A very small deflection is vulnerable to artefact.
2. Inspect the right precordial leads.
   Review V1–V3 carefully, focusing on the end of the QRS and the transition into the ST segment.
3. Look for a reproducible terminal signal.
   Determine whether the deflection is consistently present across beats and is genuinely after the QRS rather than a notch within it.
4. Review the whole ECG.
   Assess T-wave morphology, terminal activation, QRS characteristics, ventricular ectopy, and any other relevant abnormalities.
5. Correlate clinically.
   Consider symptoms (including syncope or palpitations), family history of cardiomyopathy or sudden death, rhythm monitoring, and cardiac imaging.
6. Seek expert review when uncertain.
   Because agreement between readers can be poor, do not label an equivocal terminal deflection as an epsilon wave without careful review.

6. Diagnostic Pitfalls and Limitations

Distinguishing an epsilon wave from a J (Osborn) wave

Both may appear near the QRS–ST junction, but they represent different ECG phenomena. A J wave is a deflection at the end of the QRS complex, classically associated with early repolarization or hypothermia in the appropriate context. An epsilon wave is described as a delayed, low-amplitude depolarization signal after the QRS, classically sought in right precordial leads in arrhythmogenic cardiomyopathy. In subtle tracings, morphology and timing can overlap; avoid making the distinction from a single isolated notch without reviewing the full ECG and clinical setting.

7. Key Takeaways

• An epsilon wave is a small, low-amplitude terminal depolarization signal between the end of the QRS and the onset of the ST segment.
• It is classically assessed in V1–V3 and associated with delayed right ventricular activation in arrhythmogenic cardiomyopathy.
• A small wiggle or low-amplitude positive or negative spike may be seen; morphology and visibility vary between leads and recordings.
• Fontaine bipolar leads may improve visualization in selected cases; RA is placed at the manubrium, LA at the xiphoid, and LL at the V4 position.
• The finding has limited sensitivity and important reproducibility concerns. The 2020 Padua criteria classify it as a minor criterion.
• Diagnosis requires a multiparametric assessment; neither the presence nor absence of an epsilon wave should determine the diagnosis alone.

Knowledge Check

References