Dissociation between coronary sinus and left atrial conduction in patientswith atrial fibrillation and flutter

Introduction: Coronary sinus (CS) recordings are routinely used during elec trophysiologic studies for various supraventricular and ventricular arrhyth mias with the understanding that they represent left atrial (LA) activity. However, the behavior of CS electrical activity during atrial arrhythmias h as not drawn any special attention beyond standard considerations. Methods mad Results: The study population consisted of 9 patients (3 women; mean age 59 +/- 11 years) with atrial fibrillation (AF) and atrial flutter (AFL) who developed dissociation of conduction between the CS and posterio r LA during spontaneous AF and AFL, In all patients, the LA and the CS were mapped using a 64-electrode basket catheter and a multipolar electrode cat heter, respectively. The right atrium (RA) was mapped simultaneously using a 24-polar electrode catheter (7 patients) or a 64-electrode basket cathete r (2 patients). Eight patients showed stable double potentials in CS record ings during AF (9 episodes) and AFL (3 episodes). During ongoing arrhythmia s, the first row of potentials maintained a constant relationship with the RA activity, whereas the second row of potentials was discordant with the p osterior wall of the LA in 7 patients and concordant in 2 patients. In 1 pa tient with counterclockwise AFL, CS activation was isolated from the poster ior wall of the RA until it reached the distal portion of the CS, after whi ch it entered the lateral region of the LA. In 1 patient, a macroreentrant LA tachycardia involving CS muscle was observed. Rapid atrial pacing from t he proximal CS and extrastimuli produced longitudinal dissociation of CS ac tivation in all patients. Conclusion: Conduction between the CS and posterior LA can be dissociated during sponta neous atrial arrhythmias and provocative proximal CS pacing.