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Background: Electrical isolation of pulmonary veins (PV's) is crucial to achieve success in catheter ablation for trigger elimination in focal atrial fibrillation (AF). To guide ostial PV radiofrequency (RF) delivery, it is necessary to identify the electrical breakthrough (EBT) between PV and left atrium. For this purpose, coronary sinus (CS) fixed rate pacing is commonly used. This study evaluated, whether CS extrastimulus pacing is superior in identifying the EBT area as compared to fixed rate pacing.

Objective: Atrial fibrillation (AF) as an “indicator arrhythmia” for enhanced atrial vulnerability in mouse hearts has not yet been systematically examined. We therefore evaluated a transesophageal rapid atrial stimulation protocol for the induction of AF in C57Bl/6 mice. Methods: 40 C57Bl/6 mice (19 female and 21 male; 5.2 ± 2.1 months; 18 – 27 g) were examined by closed chest transesophageal atrial stimulation. Baseline ECG and electrophysiological parameters, AF-inducing stimulation cycle length (CL) and AF duration were analyzed. Results: The surface ECG demonstrated a significantly faster heart rate in female mice (R-R: 138.7 ± 19.9 ms versus 150.5 ± 15.7 ms, P < 0.05). AF was inducible in 90 % of the population and not inducible in 4 mice, all female (21 % in this subgroup). Mean induction CL was 27.4 ± 7.3 ms. Mean AF duration was 26.9 ± 42.6 s before spontaneous termination. In a subgroup of 4 female and 4 male mice (mean age 7.5 months), successive testing of AF induction showed a range of higher susceptibility to AF at stimulus amplitudes of 3.0 – 4.0 mA and stimulation CLs between 15 – 25 ms. AF induction was observed to be constantly reproducible in the individual animals. No correlation to pacing stimulus length and amplitude was found. Conclusions: This study demonstrates that it is possible to reproducibly induce self-terminating AF and supraventricular arrhythmias in mice by transesophageal atrial burst stimulation. The presented method allowing serial testings of the same animal can be a useful tool in further investigations with transgenic mice and might be helpful in the characterization of underlying genetic or molecular mechanisms of AF.

Background: Atrial fibrillation (AF) can be cured in a subgroup of patients performing catheter ablation and eliminate trigger arrhythmias mainly originating in the pulmonary veins (PV's).

Electrical isolation of pulmonary veins (PV's) is crucial to achieve success in catheter ablation for trigger elimination in focal atrial fibrillation (AF). To guide ostial PV radiofrequency (RF) delivery, it is necessary to identify the electrical breakthrough (EBT) between PV and left atrium. For this purpose, coronary sinus (CS) fixed rate pacing is commonly used. This study evaluated, whether CS extrastimulus pacing is superior in identifying the EBT area as compared to fixed rate pacing.In 9 patients (51 +/- 10 years) undergoing a left sided electrophysiological study for AF ablation, 25 PV's (10 right and 15 left-sided PV's) were mapped using a 4 French fixed-wire catheter with eight 6 mm coiled Platinum electrodes in a distal looped configuration (Revelation Helix, Cardima Inc.). For mapping and ablation the electrode loop was positioned in the PV ostium rectangular to the longitudinal PV axis. EBT area was identified as those electrodes indicating the earliest PV signals during CS pacing. We measured number of EBT electrodes and time between EBT and the latest activated bipoles at the electrode loop during fixed rate and extrastimulus pacing. The reduction of two or more EBT electrodes was defined as a significant benefit in EBT identification.In 22 of 25 PV's mapped PV potentials could be observed. Performing fixed rate pacing the EBT area was identified in a mean of 4.2 +/- 1 electrodes, whereas using extrastimulus pacing, EBT area could be significantly reduced to 2.3 +/- 0.8 electrodes. The time between EBT and latest electrode activated increased from 14 +/- 7 ms to 22 +/- 10 ms indicating an intrapulmonary conduction delay during extrastimulus pacing. In 13 of 22 PV's mapped (59%), extrastimulus pacing was beneficial in the identification of the EBT, as the primary target for RF delivery.CS extrastimulus pacing induces intra-PV decremental conduction properties allowing one to identify a more localised and smaller EBT area as the primary target for RF delivery. Performing PV ablation to treat focal AF, extrastimulus maneuvers allow to unmask the "true" EBT and thus may help to limit intrapulmonary RF delivery.

In this study, we report an intraprocedural incident in patients undergoing ablation for atrial fibrillation. During left atrial manipulation our patients suffered from acute chest pain, showed ECG signs of an acute inferior wall myocardial infarction, and increased levels of cardiac Troponin I (cTnI). We strongly recommend being aware of unexpected reactions during isolating pulmonary veins for focal atrial fibrillation, especially when passing the dorsal part of the left atrium. If pericardial effusion is ruled out and ECG signs as well as symptoms disappear, the ablation procedure should proceed. We think patients undergoing pulmonary vein ablation for atrial fibrillation should be informed of this threatening complication.

We report a case study demonstrating delayed circumferential intrapulmonary-venous conduction characteristics during coronary sinus extrastimulus pacing. This phenomenon allowed the unmasking and discrimination of a localized left atrial to PV breakthrough from secondarily activated PV muscle in a common left-sided PV ostium. Thus, this pacing manoeuvre may serve to guide RF delivery in the treatment of focal AF.

Atrial fibrillation (AF) can be cured in a subgroup of patients performing catheter ablation and eliminate trigger arrhythmias mainly originating in the pulmonary veins (PV's).This case report describes the use of a novel catheter design combining both, circumferential mapping and radiofrequency delivery capabilities to perform pulmonary vein ablation in patients with focal AF. It could be demonstrated that this catheter was able to eliminate pulmonary vein potentials in a single left atrial catheter technique without acute evidence for PV stenosis. In two PV's of a second patient, where the Helix catheter was placed in a very ostial position, it was not possible to completely eliminate the PV signal component of the ostial electrogram. Long-term follow-up with AF recurrence documentation will clarify whether ostial PV signal amplitude reduction may serve as an acceptable procedural endpoint.PV potential elimination is feasible using this novel catheter design; safety and long-term efficacy of this single catheter approach will be evaluated in a multicenter study (BITMAP study: Breakthrough and Isolation Trial: Mapping and Ablation of Pulmonary Veins).