Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare and potentially lethal genetic disease characterized by progressive replacement of myocytes by fibrofatty tissue. This structural change creates a substrate for severe ventricular arrhythmias and significantly increases the risk of sudden death.
In this article, we take an in-depth, didactic look at the characteristic electrocardiographic findings of ARVC and how the ECG can be a crucial tool for the early diagnosis of this condition.
Electrocardiographic Criteria
The main criteria used in clinical practice are:
- Epsilon wave: a small positive deflection at the end of the QRS complex, indicating late electrical activation.
- Terminal activation delay: prolongation of the terminal portion of the QRS (> 55 ms), reflecting slow conduction in the affected region.
- Nasir index: ratio of the summed QRS duration in V1 to V3 to the summed QRS duration in V4 to V6, considered positive when > 1.2.
- QRS fragmentation: notches or fragments within the QRS complex, suggesting areas of fibrosis and heterogeneous conduction.
- T-wave inversion: inverted T waves in the right precordial leads (V1–V3), indicating abnormal ventricular repolarization.
ECG in arrhythmogenic right ventricular cardiomyopathy. Note the epsilon wave in V1, V2 and V3.
A Closer Look at the Electrocardiographic Criteria
The Task Force Criteria (TFC), the main tool used to diagnose ARVC, highlight the importance of a multidisciplinary approach within cardiology when investigating the disease. This is because tests such as magnetic resonance imaging, echocardiography and ventriculography, together with clinical data such as the presence of arrhythmias and family history, make up the TFC diagnostic criteria along with the ECG. In this context, although analysis of the 12-lead ECG is not mandatory for the diagnosis of ARVC, its interpretation can be essential to raise or lower the likelihood of this diagnosis, since the TFC include criteria for both depolarization and repolarization abnormalities.
| Depolarization abnormalities | Major: epsilon wave in the right precordial leads (V1 to V3). |
|---|---|
| Minor: late potentials on signal-averaged ECG in at least one of three parameters in the absence of QRS ≥ 110 ms on the 12-lead ECG. Filtered QRS duration (fQRS) ≥ 114 ms. Duration of terminal low-amplitude signals (< 40 µV) ≥ 38 ms. Root-mean-square voltage of the terminal 40 ms ≤ 20 µV. Terminal QRS duration ≥ 55 ms in V1, V2 or V3. | |
| Repolarization abnormalities | Major: inverted T waves in the right precordial leads (V1, V2 and V3) or beyond V3 in individuals > 14 years of age (in the absence of RBBB). |
| Minor: inverted T waves in V1 and V2 in individuals > 14 years of age (in the absence of RBBB). Inverted T waves in V1, V2, V3 and V4 in individuals > 14 years of age (in the presence of RBBB). |
A completely normal ECG, without any change typical of ARVC or suggestive of other heart disease, may be found in approximately 12% of patients with the disease. In these cases, further testing should be carefully considered, since, as mentioned, the ECG is not mandatory for the diagnosis.
The epsilon wave, present in about 10 to 35% of cases, is a low-amplitude deflection between the end of the QRS complex and the beginning of the T wave (Figure 2), best seen in the right precordial leads.
Terminal activation delay occurs in 5 to 20% of patients and is defined as an interval ≥ 55 ms from the nadir of the S wave to the end of the QRS in V1-V3. The Nasir index is calculated as the ratio of the summed QRS duration in V1 to V3 to the summed QRS duration in V4 to V6, and is considered positive when > 1.2. QRS fragmentation, which can be mistaken for epsilon waves, has low specificity. Inverted T waves, on the other hand, are present in most cases (83 to 87%) and, when they extend to V3, may indicate advanced disease and a worse prognosis.
References
- Scheffer MK, De Marchi MFN, de Alencar Neto JN, Felicioni SP. Eletrocardiograma de A a Z. São Paulo: Manole, 2024.
- Nunes De Alencar Neto J, Baranchuk A, Bayés-Genís A, Bayés De Luna A. Arrhythmogenic right ventricular dysplasia/cardiomyopathy: an electrocardiogram-based review. Europace. 2018;20(FI1):f3-12.
