Evidence for vagal denervation as a possible mechanism of successful RF-ablation of atrial fibrillation

A 70-year-old former athlete complained about a twenty-year history of paroxysmal atrial fibrillation with onset at rest and during the night, which became persistent in the last three years. Previous medication including sotalol, flecainide, disopyramide and amiodarone had been unsatisfactory. A circumferential left atrial ablation was performed after transseptal puncture (fig. 1). During delivery of radiofrequency energy at the posterior left atrium several episodes of vagal activation occurred with slowing of AV nodal conduction and concomitant acceleration of atrial fibrillation cycle length (fig. 2). We repeatedly observed the coincidence of slowed AV-nodal conduction with acceleration of atrial fibrillation cycle length (fig. 3). During ablation atrial fibrillation organised and the driving trigger was found at the right superior pulmonary vein (PV) ostium (ABL: ablation catheter positioned directly at the ostium of the right superior PV; distal electrode with PV electrogram preceding the atrial electrogram on the proximal electrode by 90 msec, fig. 4). During ablation the pulmonary vein tachycardia blocked 2:1 and then persisted 4 seconds after PV disconnection from the left atrium (fig. 5). Afterwards the patient was in stable sinus rhythm and atrial fibrillation could not be induced anymore. At follow-up three months after ablation the patient reported no further episode of atrial fibrillation off anti-arrhythmic drugs. His sinus rhythm rate was generally elevated with a mean rate of 85/min (fig. 6). This case provides unique evidence for the direct effects of vagal activation during delivery of radiofrequency energy: slowing of AV nodal conduction, shortening of atrial fibrillation cycle length and disorganisation of atrial electrograms. After ablation there is evidence of vagal denervation with elevation of the sinus rate lasting up for at least three months.