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Case report: Slow conducting accessory pathway in an Ebstein's anomaly patient: Is this a Mahaim fiber?
Yi Liu1, Yuwei Chen1, Qiang Xiao2
1Department of Cardiovascular Medicine, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China.
Abstract:
We report a case of multiple accessory pathways (APs) in an Ebstein's anomaly patient with a history of prior ablation. Electrophysiological study demonstrated a slow conducting AP which pre-excited ventricle only during atrial tachycardia or rapid atrial pacing. The non-decremental property and a longstanding fragment potential at the ablation target site rule out Mahaim fiber. The slow conducting AP might be caused by inadequate prior ablation, and highlights that delta wave absent and prolonged AV interval in target point could not definitely indicate anterograde conduction block when we ablate a manifest AP. Rapid atrial pacing may unveil the slow conducting AP.
Insights
This study found a slow accessory pathway (AP) in an Ebstein's anomaly patient, potentially missed by prior ablation. Rapid atrial pacing revealed this AP, emphasizing careful electrophysiological assessment.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Surgery
Background:
- Ebstein's anomaly is a congenital heart defect affecting the tricuspid valve.
- Accessory pathways (APs) can cause arrhythmias in patients with congenital heart disease.
- Prior ablation procedures may not always eliminate all APs.
Purpose of the Study:
- To report a case of multiple accessory pathways in an Ebstein's anomaly patient post-ablation.
- To investigate the characteristics of a slow-conducting AP.
- To highlight diagnostic challenges in identifying residual APs.
Main Methods:
- Electrophysiological study (EPS) was performed.
- Atrial tachycardia and rapid atrial pacing were utilized.
- Analysis of electrophysiological signals, including delta waves and AV intervals, was conducted.
Main Results:
- A slow-conducting accessory pathway (AP) was identified in an Ebstein's anomaly patient with a history of ablation.
- The AP pre-excited the ventricle only during atrial tachycardia or rapid atrial pacing.
- Non-decremental properties and fragment potentials ruled out Mahaim fibers.
- Absence of delta waves and prolonged AV intervals at the target site did not confirm anterograde conduction block.
Conclusions:
- Inadequate prior ablation may lead to residual slow-conducting APs.
- Diagnostic criteria for complete AP ablation need careful consideration, especially in complex cases.
- Rapid atrial pacing is a valuable tool for uncovering subtle or slow-conducting APs.
