Sinus Node Region as an Ultimate Source Driving Chronic Atrial Fibrillation

A 39-year-old male was referred to our institution for catheter ablation of chronic atrial fibrillation (AF) with worsening dyspnea. AF was first diagnosed 25 years ago concomitant to an episode of myocarditis. He had failed treatment using antiarrhythmics, multiple cardioversions, and maze procedure; with AF being permanent over the last 21 years. Electrophysiological study demonstrated no electrical activity in all pulmonary veins, the posterior left atrium (LA), a part of the anterior LA, and the posterior and the lateral right atrium (RA), presumably as a consequence of myocarditis, the maze procedure, and long-lasting AF. Catheter ablation started with a linear lesion between the postero-lateral mitral annulus and the left inferior pulmonary vein, and then targeted the regions with short cycle length and/or fractionated activity in the septum, the roof, and the inferior wall of the LA. This procedure resulted in nearly total abolition of LA activity except in the antero-septal wall and the coronary sinus. Then, mapping was performed in the RA and demonstrated shorter cycle length activity than in the LA. Disconnection of the superior vena cava and ablation of the cavotricuspid isthmus was performed without effect on the fibrillatory cycle length. Using two multielectrode catheters, mapping identified the activity with the shortest cycle length in the sinus node region. Radiofrequency ablation was performed from the anterior RA laterally to an electrically silent area in the posterior RA. After 15 minutes of radiofrequency energy delivery, AF terminated suddenly simultaneous with electrical isolation of the sinus node region (Fig. 1). The earliest atrial activity was mapped in the septal RA. Local firing with a cycle length of 210 msec persisted in the sinus node region continuously for >30 minutes after ablation. The estimated surface area of isolated region with persistent firing was 2 × 3 cm. The remaining RA was activated by septal automatic rhythm, which had occasional pauses relayed by an escape junctional rhythm. This atrial rhythm was maintained after the procedure with a mean of 50 beats/min; however, AF recurred 3 weeks later and remained persistent. This case demonstrated that fibrillatory sources can be localized in the sinus node region, thus implicating an extensive distribution of the critical substrate maintaining chronic AF.