Interesting electrophysiological findings in a patient with coexistence of atrial tachycardia originating from coronary sinus and slow-fast atrioventricular nodal reentrant tachycardia.

Slow-fast atrioventricular nodal tachycardia (AVNRT) has various electrophysiological aspects due to atrioventricular (AV) nodal physiology. In addition, concomitantly another form of arrhythmia with AVNRT, especially atrial tachycardia (AT), was an infrequent arrhythmia. A 38-year-old female with narrow QRS tachycardia underwent electrophysiological study due to frequent faintness. The electrophysiological study disclosed the coexistence of AT originating from coronary sinus (CS) with slow-fast AVNRT. We easily diagnosed AT originating from CS and terminated with several radiofrequency ablations (RFA) around CS. The diagnosis of slow-fast AVNRT, however, was somewhat difficult due to the following findings: (1) small amount of adenosine triphosphate (ATP) could terminate slow-fast AVNRT reproducibly; (2) we could provoke slow-fast AVNRT only by RV pacing with isoproterenol infusion. With other electrophysiological findings, we diagnosed slow-fast AVNRT. Radiofrequency energy was delivered initially in the posteroseptal region, followed by inside CS, and finally in the middle septal region, which completed the slow pathway ablation. After the procedure, we could never provoke these arrhythmias. <Learning objective: Coexistence of focal AT originating from CS with slow-fast AVNRT is a rare phenomenon. Furthermore, slow-fast AVNRT could show unusual characteristic as following: (1) small amount of ATP terminates slow-fast AVNRT; (2) atrial pacing never provoked slow-fast AVNRT with isoproterenol infusion whereas ventricular pacing did, which depends on the physiological characteristic of the dual AV nodal pathway. Accordingly, we should precisely assess the obtained electrophysiological findings.>.