Abstract
Pulmonary vein isolation and atrial substrate modification using catheter ablation have been developed as a standard treatment for atrial fibrillation (AF). However, the standard end-point for these procedures is still not well established. This study aimed to investigate the characteristics among positive and negative AF vulnerability patients with normal structural heart, in order to define the endpoint of the atrial substrate modification. Fifty supraventricular tachycardia patients with normal heart structure referred for electrophysiological study and catheter ablation were enrolled. After eliminating the underling arrhythmias, the basic cycle length, effective refractory period of the right atrium, and the P wave indices in 12-lead electrocardiograms were measured. The AF vulnerability test was performed by atrial burst decremental pacing with a pacing cycle length decreasing from 290 ms to 200 ms. The AF vulnerability test was considered as positive when the duration of the induced AF or atrial tachyarrhythmias (ATs) was longer than 10 seconds. The parameters of atrial substrates were compared between patients with positive and negative values of the AF vulnerability test. ATs or AF were induced in 24 (48%) patients. Among these patients, 12 (24%) induced ATs or AF were found to be sustained (duration more than 10 seconds). However, only two of these patients could reproduce the positive result after 10 minutes of the first induced protocol. Comparing the patient baseline characteristics, P wave characteristics and cardiac echo parameters, there were no significant differences between the positive and negative AF vulnerability groups. In conclusion, AF and ATs could be induced in patients with a structurally normal heart. The traditional clinical indices of atrial substrates were not significantly different between the positive and negative AF vulnerability patients. Protocols other than atrial burst decremental pacing should be investigated to evaluate the endpoint of the atrial substrate modification.