Lower loop reentry (LLR) is a rare type of right atrial flutter defined as macroreentrant tachycardia maintained by a circuit around the inferior vena cava (IVC). We experienced a patient with the atypical LLR maintained by a circuit around a bundle of multiple hepatic veins (HVs) directly connected with right atrium (RA).
A 32-year-old female after Rastelli operation for mirror-imaged Tetralogy of Fallot with interruption of IVC presented with paroxysmal palpitation. The entrainment study for the atrial tachycardia (AT) with the cycle length of 325 ms suggested a macroreentrant mechanism around the HVs directly connected to the bottom of RA (Figure). After the linear ablation of the tricuspid annulus (TA) to HV isthmus and the additional ablation for fragmentation potentials at the bottom of the RA, the AT was no longer inducible. The AT in this patient would be designated as atypical LLR. This reentrant circuit depends on conduction through the TA-HV isthmus. The AT sometimes showed beat-by-beat variations with a similar activation sequence. This macroreentrant tachycardia appears to have rotated around a bundle of HVs and/or several of them in some instances. 
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