A low amplitude His-bundle potential predicts failure of the right-sided approach for atrioventricular junction ablation

In 30 patients with drug refractory atrial fibrillation-flutter who underwe nt radiofrequency (RF) ablation of the atrioventricular (AV) junction, 23 w ere successfully ablated using the conventional right-sided approach (group A). Seven patients required a left-sided approach (group B) after multiple applications from the conventional right-sided approach failed to produce complete AV block. The amplitude of the His-bundle potential recorded at th e ablation site differed significantly between the 2 groups (0.23+/-0.11 mV in group A vs 0.12+/-0.04 mV in group B; p<0.005). Also, the amplitude of the His-bundle potential recorded in the standard position across the tricu spid annulus differed significantly between the 2 groups (0.27+/-0.35 mV in group A vs 0.11+/-0.44 mV in group B; p<0.007), There was no significant d ifference in the amplitude of the ventricular potential between the 2 group s. The probability of successful ablation of the AV junction with a convent ional right-sided approach was 6 out of 12 patients (50%) if the His amplit ude was <0.12 mV, and 17 out of 18 patients (94%) if the His amplitude was >0.12mV (p<0.005). Patients in group B had a mean of 20.5+/-13.0 failed rig ht-sided RF applications (5-33 applications), but required a mean of only 2 subsequent RF applications for success on the left side (1-6 applications) . The His-amplitude recorded from the left side using the same catheter was significantly greater than that on the corresponding right-side (0.22+/-0. 09 mV on the left side vs 0.12+/-0.04 mV on the right side: p<0.05). Total mean fluoroscopic time was 62+/-12 min for group B and 20+/-13 min for grou p A patients. Tn patients that underwent RF ablation of the AV junction, a maximum His amplitude <0.12 mV predicted a success rate of approximately 50 % in the present study. An early switch to a left-sided approach may avoid multiple RF applications and prolonged fluoroscopic time in patients with a low amplitude His-bundle potential.