Coronary Sinus Tachycardia Driving Atrial Fibrillation
A 59-year-old man underwent radiofrequency catheter ablation for symptomatic drug refractory atrial fibrillation (AF). Prior ablations for AF had included pulmonary vein (PV) electrical isolation and additional substrate modification involving linear ablation joining the 2 superior PVs (roofline) and the anterior mitral annulus with the roofline (anterior line). Despite significant clinical improvement, further mapping and ablation was performed because of recurrent arrhythmia. At the time of the procedure, the ECG demonstrated AF with intermittent termination that was followed by immediate re-initiations, suggestive of a focal source (Figure 1A and 1B). Mapping of the earliest activity during initiation of AF localized the site of origin to the coronary sinus (CS); however, there were changes in local activation sequence suggestive of multiple foci or multiple exits to the left atrium. Radiofrequency energy was delivered at sites of earliest activity within the mid-CS, which was progressively mapped to more proximal sites (Figure 1C). Final application of radiofrequency energy at the ostium of the CS resulted in electrical isolation of the CS from the atria with termination of AF. Despite restoration of sinus rhythm, ongoing fibrillatory activity with a cycle length range from 81 to 210 ms was still recorded in the CS (Figure 2A). This activity occurred in episodic bursts alternating with slow dissociated rhythms without conduction to the adjacent chambers (Figure 2B). After CS isolation, AF could no longer be induced. This unreported observation is conclusive evidence for the role of the CS as an independent driver maintaining AF by sustained or episodic bursts of activities of short cycle length driving the atria. These observations are analogous to the role of the PVs and superior vena cava in AF and further implicate an important function of the thoracic veins in the maintenance of AF.