Transient Restoration of the Electrical Conduction Between the Left Atrium and Coronary Sinus Musculature
The coronary sinus musculature (CSM) is known to be not only an electrical conductor between the inferior right atrium and left atrial myocardium, but also an arrhythmogenic structure. To eliminate the arrhythmogenic substrate, electrical disconnections between the CSM and left atrium (LA) are often required. We present a transient restoration of the electrical conduction between the CSM and LA by the administration of adenosine after radiofrequency catheter ablation (RFCA) within the CS. A 72‐year‐old woman underwent ablation of persistent atrial fibrillation (AF). After pulmonary vein isolation, AF was still sustained and complex fractionated atrial electrograms (CFEs) was recorded in the CS electrodes. RF applications were delivered within the CS targeting CFE, but it did not work. During ablation along the CS, the high‐frequency potentials representing the CSM disappeared, as shown on the mid‐CS electrodes (solid arrow, Fig. 1A). After the AF terminated by electrical cardioversion, the CSM potentials that had disappeared during the prior ablation appeared as double potentials. Blunt‐ and low‐amplitude potentials, representing the local left atrial activation, appeared first (dashed arrow, Fig. 1B), and then high‐frequency potentials representing the CSM followed (solid arrow, Fig. 1B). To evaluate the LA to PV dormant conduction, 20 mg of adenosine was administrated and revealed gradual merging of the double potentials (1st, 2nd, and 3rd beats, Fig. 1B), which continued throughout the adenosine perfusion and disappeared as the adenosine washed out. This case shows the linkage between CS muscle and LA and transient restoration of slow conduction between the LA and CSM after ablation revealed by an adenosine administration. In such a circumstance, the CSM does not represent the activation pattern of the contiguous LA, and a conduction delay of the CSM can provide the substrate for a reentrant tachycardia such as an unstable reentry involving the CSM and CS atrial junction leading to AF or an atypical atrial flutter using the CSM as a critical isthmus. In this context, adenosine is useful to evaluate a dormant conduction of CSM.