Demonstration of the Anatomical Tachycardia Circuit in Sinoatrial Node Reentrant Tachycardia: Analysis Using the Entrainment Method.

Background The anatomical tachycardia circuit of sinoatrial node reentrant tachycardia (SANRT) has not been well clarified. This study aimed to elucidate the tachycardia circuit of SANRT. Methods and Results Exit and entrance of the intranodal sinoatrial node conduction (I-SANC) of the reentry circuit were identified in 15 SANRT patients. After identifying the earliest atrial activation site (EAAS) during the tachycardia (EAAS-SANRT), rapid atrial pacing was delivered from multiple atrial sites to identify the entrainment pacing site where manifest entrainment and orthodromic capture of the EAAS-SANRT were demonstrated. Radiofrequency energy was then delivered starting at a site 2 cm proximal to the EAAS-SANRT in the direction of the entrainment pacing site and gradually advanced toward the EAAS-SANRT until tachycardia termination to localize the I-SANC entrance. The EAAS-SANRT was orthodromically captured by pacing delivered from the distal coronary sinus (n=7), high posteroseptal right atrium (n=2), low posteroseptal right atrium (n=2), low anterolateral right atrium (n=2), or coronary sinus ostium (n=2). Radiofrequency energy delivery to the entrance of the I-SANC, 10.4±2.8 mm away from the EAAS-SANRT, terminated tachycardia immediately after onset of energy delivery (3.4±2.3 seconds). The successful ablation site was located further from the EAAS during sinus rhythm (EAAS-sinus) than the EAAS-SANRT (12.8±4.5 versus 7.2±3.1 mm;