Dry Pericardial Access Enables Definitive Treatment of Septopulmonary Bundle-Mediated Roof-Dependent Flutter

Catheter ablation for atrial fibrillation (AF) is widely accepted as an effective alternative to antiarrhythmic drug therapy. However, epicardial roof-dependent macro-re-entrant atrial tachycardia (epi-RMAT) after ablation for persistent AF is not uncommon. Reported ablation strategies include left atrial posterior wall isolation, roof-line ablation, and anterior and septal linear lesions. Recent studies indicate that despite extensive endocardial ablation, residual epicardial conduction via the septopulmonary bundle (SPB) can bypass the roof line, making durable success challenging.

A 61-year-old man presented with atrial flutter after prior catheter ablation for persistent AF. In the electrophysiology laboratory, activation mapping and entrainment demonstrated an SPB-mediated, epicardially driven atrial flutter. Conventional endocardial linear ablation failed to terminate the tachycardia. Despite anatomic constraints, the arrhythmia was successfully terminated using an epicardial ablation approach.

In post-AF ablation patients, SPB-mediated epi-RMAT should be suspected when roof-dependent flutter persists despite apparently complete endocardial lines. When conventional endocardial strategies are ineffective, targeted epicardial ablation can interrupt the critical isthmus and terminate the tachycardia. This case illustrates a feasible strategy for managing challenging epicardial circuits encountered after AF ablation.

Complex epicardial fiber architecture of the left atrium-particularly the SPB-may constitute key components of roof-dependent re-entry after AF ablation. Recognizing epicardial involvement helps identify the true circuit and can improve both procedural safety and efficacy when endocardial lesions are insufficient. Consider an epicardial approach when mapping and entrainment suggest SPB-mediated conduction that circumvents the roof line.