Epsilon waves are the surface manifestation of myocardial regions with delayed activation and are considered the hallmark of arrhythmogenic right ventricular cardiomyopathy. However, other conditions can also result in epsilon waves and simulate arrhythmogenic right ventricular cardiomyopathy. In this case, a patient presents with recurrent ventricular tachycardia and large epsilon waves due to cardiac sarcoidosis. (
Level of Difficulty: Intermediate.
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Atrioventricular (AV) discordance is an uncommon form of congenital heart disease. 1 In patients with this abnormality, the right atrium is connected to the morphological left ventricle through the mitral valve and the left atrium to the morphologically right ventricle through the tricuspid valve. AV discordance is a "sine qua non" feature of congenitally corrected transposition of the great arteries (cc-TGA). However, AV discordance can also be associated with other congenital heart malformations, such as double outlet right ventricle. In cc-TGA, the concomitant ventriculoarterial discordance (double discordance) physiologically corrects the pulmonary and systemic circulation, so that they remain in series. Thus, these patients are acyanotic and often remain asymptomatic until adulthood. 2 This is more likely to occur when the systemic right ventricular function is preserved and in the absence of concomitant severe defects such as ventricular septal defect, pulmonary outflow tract obstruction or systemic tricuspid valve regurgitation.However, patients with AV discordance frequently present with arrhythmias even if they do not suffer from other congenital abnormalities. Conduction system disorders, AV nodal reentrant tachycardia, and accessory AV pathways (APs) account for a high incidence of arrhythmias in these patients.Why do these patients develop these arrhythmias even in the presence of near-normal circulation? To answer this question, we need to understand the developmental abnormalities that occur as a result of the peculiar anatomical arrangement in these patients. We will now discuss how the abnormal embryological development underlies the arrhythmias that arise in patients with AV discordance.
| CONDUCTION DISORDERS IN AV DISCORDANCEIn the presence of situs solitus and AV discordance, both left ventricle and mitral valve are located to the right and connected to the pulmonary artery. Due to the location of the pulmonary outflow tract between the ventricular septum and the mitral valve on the right, there is a malalignment between the ventricular and atrial septa. As a result, the AV node that is usually located inferiorly and posteriorly in front of the ostium of the coronary sinus in the AV septum and at the apex of the triangle of Koch becomes hypoplastic and frequently does not connect with the His bundle (Figure 1).Patients with cc-TGA have an additional superiorly and laterally located AV node situated close to the mouth of the right atrial appendage and lateral margin of the fibrous continuity between pulmonary and mitral valves. This additional AV node gives origin to an elongated AV bundle that runs medially to reach the fibrous trigone and continue as the penetrating portion of the His bundle eventually giving rise to the right bundle branch and the divisions of the left bundle branch. 3 The bundle branches follow the respective ventricles so that the left bundle is now located on the right side following the morphological left ventricle and the right bundle on the left side with the morpholog...
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