Electrophysiological mapping and ablation
Procedures were carried out under general anaesthetic. With the exception of amiodarone, antiarrhythmic drugs were stopped a minimum of five days prior to the procedure. Venous access was obtained via bilateral femoral vein puncture under direct ultrasound guidance. Heparin boluses were administered prior to trans-septal puncture followed by continuous heparin infusion to maintain an ACT >350s. A decapolar catheter (Inquiry, Abbott Medical) was inserted into the coronary sinus through an AcQRef (Acutus Medical) sheath which includes a distal electrode used as a unipolar reference. The first AcQMap catheter was advanced over a 0.032 guide wire into the RA via an AcQGuide (Acutus Medical) sheath and ultrasound used to reconstruct the right atrial chamber anatomy as previously described.(7) The ablation catheter (Tacticath, Abbott Medical) was advanced via an Agilis sheath into the left atrium across the single transseptal puncture site. The second AcQGuide sheath was then exchanged for the transseptal access sheath over the guide wire and a second AcQMap catheter advanced into the LA (see figure 2). The LA anatomy was then generated with ultrasound. A circular mapping catheter (Inquiry Optima or Advisor Variable Loop, Abbott Medical) was used to undertake electroanatomic voltage mapping and guide pulmonary vein isolation.
In a subset of 9 patients, activation maps were obtained using Supermap during pacing from up to three atrial sites (left atrial appendage, high right atrium and proximal coronary sinus) with direct cardioversion used to restore sinus rhythm where necessary. Pacing consisted of a 4-beat drive train at 800ms cycle length followed by a single extrastimulus with coupling interval 20ms above the effective refractory period and was mapped using the AcQMap Supermap algorithm. Additional details are provided in the supplementary methods.
In patients attending the procedure in sinus rhythm AF was induced using burst atrial pacing, otherwise all AF recordings were obtained prior to DCCV. Once AF was established, recordings of 2 minutes duration were generated and time alignment between systems facilitated using a below threshold pacing stimulus from the coronary sinus catheter of 4 beats at 1000, 800 and 600ms intervals and 12 second rest period. Pulmonary vein isolation was performed using contact force guided radiofrequency ablation using 40-50 Watts (Tacticath ablation catheter, Abbott Medical). Simultaneous biatrial AF mapping was repeated following completion of PVI. Additional ablation and AF mapping was undertaken at the discretion of the operator.