# Roof-dependent Macro-reentrant Left Atrial Flutter Masked by Probable Epicardial Conduction via the Septopulmonary Bundle

## TL;DR

A rare case of left atrial flutter was found to involve a unique pathway called the septopulmonary bundle, which may complicate diagnosis and treatment.

## Contribution

Highlights the role of the septopulmonary bundle in left atrial flutter and emphasizes the need for detailed 3D mapping in diagnosis.

## Key findings

- A roof-dependent macro-reentrant left atrial flutter was masked by epicardial conduction via the septopulmonary bundle.
- Three-dimensional mapping and electrophysiological pacing maneuvers are crucial for identifying the re-entry circuit.
- The septopulmonary bundle may contribute to the complexity and maintenance of left atrial flutter.

## Abstract

We encountered a 77-year-old woman who had a roof-dependent macro-reentrant left atrial (LA) flutter (LAFL), masked by probable epicardial conduction via the septopulmonary bundle (SPB). The SPB, an epicardial connection in the LA, may contribute to the maintenance and complexity of LAFL. Thus, when evaluating LAFL, physicians should consider the potential involvement of the SPB. Detailed observation using a three-dimensional mapping and comprehensive electrophysiological pacing maneuvers is crucial for identifying the re-entry circuit of LAFL.