A Case Report of Irregular Narrow Complex Tachycardia: Atrioventricular Nodal Re-entrant Tachycardia with a Lower Common Pathway Wenckebach.

Previous reports have established the occurrence of atrioventricular (AV) nodal re-entrant tachycardia (AVNRT) exhibiting fixed AV ratios (most commonly 1:1, but also 2:1 or higher grade) or fixed/alternating ventriculoatrial ratios (eg, 1:1, 2:1, 3:2, 4:3, or higher grade). In contrast, the manifestation of an irregularly irregular rhythm during sustained AVNRT combined with a lower common pathway Wenckebach periodicity is exceedingly rare. We formally present a case demonstrating this unusual and complex electrophysiological phenomenon.