Case report: orthodromic atrioventricular re-entrant tachycardia with left lateral accessory pathway-smart diagnosis with a smart device.

Background: Patients with supraventricular tachycardia (SVT) are often symptomatic, but frequency of symptoms is very variable. Definition of tachycardia mechanism and diagnosis is dependent on documentation of the arrhythmia by electrocardiogram (ECG), but this documentation is often missed by standard evaluation with a Holter ECG. Wearable smart devices with ECG function are valuable diagnostic tools in such patients. Case summary: We describe a case of a 59-year-old male patient who suffered from infrequent palpitations, where documentation of two distinct tachycardia ECG tracings with a wearable smart device led to the correct diagnosis. One tracing showed an episode of narrow QRS complex tachycardia at a heart rate of 200 b.p.m. and the other a broad complex tachycardia with left bundle branch block morphology at a slower heart rate. Based on these findings, which demonstrate Coumel's sign, atrioventricular re-entrant tachycardia with left lateral accessory pathway was suspected. Electrophysiological study confirmed the diagnosis, and an accessory pathway located at the lateral mitral isthmus was successfully ablated. Discussion: Aberrant ventricular conduction due to functional bundle branch block is an important finding during SVT. In the presented case, a wearable smart device was able to document two episodes of tachycardia with two distinct ECG morphologies, one with broad QRS complexes at a slower heart rate and the other with a faster episode of narrow QRS complexes. Therefore, the wearable device was not only able to document an episode of symptomatic tachycardia, but it also additionally offered important keys to the correct diagnosis.