LAUSR

Attentive appraisal to electrical spontaneous events during tachycardia is essential to the understanding of its mechanism. Introduction Atrioventricular nodal reentrant tachycardia (AVNRT) is one of the most common supraventricular tachycardias, and uncommon manifestations present a challenging diagnosis and can lead to misdiagnosis, subjecting patients to unnecessary risks, making the correct diagnosis of utmost importance. Uncommon AVNRT manifestations can mimic other supraventricular tachycardias such as atrial fibrillation, atrial tachycardia (AT), junctional tachycardia (JT), or some supraventricular arrhythmias mediated by rare or common bypass tracts. At least in some patients with AVNRT, the upper and lower common pathways are present and responsible for some unusual findings. Case report A 42-year-old woman was referred for electrophysiological study owing to palpitations refractory to beta-blockers. An electrocardiogram (ECG) recorded during symptoms revealed a supraventricular tachycardia (SVT). The patient complained of recurrent palpitations since adolescence frequently interrupted by 6 mg adenosine bolus. No comorbidity was referred. The cardiologic evaluation revealed normal left ventricular function, sinus resting ECG, and no sustained arrhythmias in 24-hour Holter monitoring. Under conscious sedation and local anesthesia, 2 right femoral vein and 1 right jugular vein punctures were performed to insert catheters in the right chambers (Supplemental Figure 1S): 1 quadripolar catheter in the right atrium / right ventricle, 1 quadripolar catheter in His bundle, and a decapolar catheter in coronary sinus floor, respectively. Baseline ventriculoatrial (VA) conduction was evaluated by