Results
We identified 5 patients from Cleveland Clinic and 9 patients from the University of California, San Francisco, who had very slow (110 bpm or less) typical AVNRT. Three additional patients were excluded because they did not undergo AOD or AES pacing maneuvers as noted in the Methods section, although tachycardia was no longer inducible after their slow pathway ablation. Therefore, a total of 11 patients were included in this analysis. Patient characteristics and electrophysiologic study data are shown in Table 1. Ages ranged from 20 to 78 years. There were six females and five males. One patient was undergoing a 4th ablation (Case 4), and two patients had their 2nd ablations (Case 7 and 9). All other patients were undergoing their initial ablation. The tachycardia cycle length ranged from 560ms to 782ms. Septal VA times were all within 70ms. All patients except for one demonstrated V-A-V response by VOD, which showed PPI-TCL over 115ms. VOD reproducibly terminated tachycardia in one patient (Case 8), and thus VOD could not be obtained.
We delivered AOD or AES to distinguish this tachycardia from JT. Advancement of the tachycardia was recognized by overdrive pacing from at least one location of the atrium (usually from the coronary sinus ostium) in 5 patients. Termination of tachycardia was recognized in one patient by overdrive atrial pacing (Case 4). With regards to the response to AES, 6 patients showed an A-H-A response, while one patient (Case 1) showed A-H-H-A response with the advancement of the tachycardia, likely due to a double ventricular response.
All patients underwent successful slow pathway ablation rendering their tachycardia not inducible after ablation.