Interpolated junctional extrasystoles mimicking complex polymorphic ventricular arrhythmias in a healthy young athlete: a case report.

Background: In young competitive athletes, ventricular arrhythmias could be a reason for concern as they may represent the sign of a serious underlying cardiac condition. On the other hand, atrial or conduction system premature beats are usually benign. However, when the properties of the His-Purkinje system lead to conduction aberrancies, there is a risk of misinterpreting benign arrhythmias as potentially at risk ventricular ectopic beats. Case summary: We described the case of a healthy young athlete with asymptomatic interpolated junctional ectopic beats interpreted as polymorphic ventricular tachycardia during pre-participation screening. Discussion: Strange and rare electrocardiogram pictures may be observed during sport pre-participation screening. The small atrioventricular (AV) junction is made up of many specialized fibres with different conduction properties. Junctional arrhythmias can have a normal anterograde conduction or can be conducted with aberrancy. Rarely, they can be interpolated and cause PR prolongation or bundle branch block by increasing the refractory period of the AV node and/or the conduction system. When aberrancy occurs, they can be mistaken for 'atypical' ventricular arrhythmias. Prognosis of these events remains uncertain.