Noninvasive electrocardiographic imaging (ECGI) of scar-related atypical atrial flutter

We report the first application of ECGI in a patient with atypical atrial flutter that developed after catheter ablation for PV isolation. ECGI detected and mapped regions of low voltages that coincided with scar tissue around the PVs from the previous catheter ablation procedures, as verified during a Cox-Maze surgical procedure. The flutter reentry circuit was constrained by the scar and mainly confined to the LA. The mitral isthmus between the coronary sinus and the PVs participated in the reentry circuit. ECGI also imaged a region of low potentials on the LAA, which is uncommon. Typically, the LAA is a region of high voltage, as measured by endocardial mapping. During the Cox-Maze procedure, it was observed that the LAA was extensively scarred (from the underlying disease not from the prior ablation), consistent with the ECGI reconstruction of low voltages in this region. The case reported in this manuscript was unique from the ECGI perspective because before the Cox-Maze procedure the diagnosis was atrial fibrillation. ECGI constructed a monomorphic stable reentrant activation pattern that was repeated for many beats, indicating anatomical rather than functional reentry. Both ECGI reconstruction of low potentials and direct observation during surgery consistently identified an extensive scar around which the ECGI-reconstructed isochrones formed the reentry circuit; the scar provided the anatomical substrate that stabilized the reentry. The repeatability of the reentry pattern over many beats demonstrates the consistency of ECGI methodology. It should be recognized that ECGI generates the entire activation map during a single beat and is therefore well suited to detect beat-to-beat changes during an arrhythmia. In contrast, catheter mapping (e.g., CARTO) is conducted point-by-point in a roving-prove fashion and requires data from many beats to construct an activation map. As such, it cannot provide data for comparison to ECGI in most cases. After the Cox-Maze procedure, the patient returned to normal sinus rhythm.