Diagnosis, Unique Observations and Ablation of Atypical Fast‐Slow Atrioventricular Nodal Reentrant Tachycardia Using an Inferolateral Left Atrial Slow Pathway: Analysis of Unique 3 Cases

ABSTRACT Introduction Fast–slow atrioventricular nodal reentrant tachycardia incorporating an inferolateral left atrial slow pathway (inf‐lat‐LA‐F/S‐AVNRT) is an exceptionally rare variant of AVNRT. Data regarding its diagnosis, electrophysiological characteristics, and optimal ablation strategy remain limited. Methods We retrospectively analyzed three women (48 ± 15 years) who underwent electrophysiological study and successful ablation of inf‐lat‐LA‐F/S‐AVNRT presenting with a long RP configuration and earliest atrial activation along the mitral annulus at the 3, 4:30, or 6 o'clock position in the left anterior oblique view. Results Atrial tachycardia was excluded using standard criteria. However, differentiation from AV reentrant tachycardia using a slowly conducting left‐sided accessory pathway required a specific maneuver: absence of atrial resetting during two consecutive fully paced ventricular stimuli. Retrograde conduction via the inf‐lat‐LA slow pathway was not reproducibly demonstrated in one patient. Typical features of F/S‐AVNRT, including double atrial response and presence of a lower common pathway, were observed. Novel findings included detectable retrograde activation of the inf‐lat‐LA slow pathway and spontaneous transition between distinct AVNRT circuits. Tachycardia was successfully eliminated by targeting the earliest atrial activation site or by a left‐sided stepwise anatomical approach. Conclusions Inf‐lat‐LA‐F/S‐AVNRT is a rare AVNRT variant with distinctive diagnostic and electrophysiological features that may require an individualized ablation strategy.