Abstract 2443: Utility of Isoproterenol During Catheter Ablation of Paroxysmal Atrial Fibrillation
Background: Assessment of inducibility of AF by isoproterenol (ISO) infusion may be helpful during catheter ablation for paroxysmal atrial fibrillation (PAF). However, there are limited data on the clinical utility and diagnostic accuracy of isoproterenol in patients with PAF.
Methods and Results: ISO was infused at 5, 10, 15, and 20 μg/min at 2-min intervals until max dose was reached or AF was induced in 20 control subjects with no history of atrial fibrillation and in 80 patients with PAF. In patients with PAF, antral ablation was performed to isolate all pulmonary veins (PVs) after induction of AF by ISO (or rapid pacing if ISO did not induce AF). After restoration of sinus rhythm by ablation or cardioversion, ISO was readministered using the same protocol. Among the 20 control subjects AF (1) or premature atrial depolarizations (PADs, 1) was induced in 2 patients (10%) only after 20 μg/min of ISO. Among 80 patients with PAF, AF (67) or PADs (2) was induced in 69 patients (86%, P<0.001). In patients with PAF, AF was inducible only in 28% at 10 μg/min whereas 91% were inducible after 20 μg/min of ISO (P<0.01). AF terminated by antral ablation in 61% of the patients who were inducible by ISO and in 12% of the patients who were not (P<0.01). After restoration of sinus rhythm, reinducibility during ISO rechallenge in 7 patients (9%), prompted identification of recovery of conduction into PVs in 2 patients and a residual driver in the antrum in 1 patient. ISO had to be discontinued in 4 patients (5%) before reaching the max dose due to reversible chest pain, or systolic blood pressure <85 mmHg.
Conclusions: ISO at doses up to 20 μg/min has a high sensitivity (87%) and specificity (90%) for induction of AF in patients with PAF. Inducibility of AF by ISO may suggest that the mechanism of AF depends on the PVs and/or their antrums.