The purpose of this randomized, prospective trial was to determine if Bachmann's bundle pacing reduces the incidence of AF after CABG. The study included 161 patients with no history of AF who were randomized to three groups. Group 1 included 50 patients as controls. Group 2 included 60 patients who had an epicardial wire placed at the lateral wall of the right atrium. In the 51 patients of group 3, the wire was placed at the Bachmann's bundle. In groups 2 and 3, atrial pacing (AAI 96 beats/min) was initiated immediately after CABG and continued for 5 days. The study endpoint was AF lasting > or = 1 minute. Baseline clinical parameters were similar in all three groups. The incidence of AF was not reduced by pacing (group 1: 42%; group 2:48%; group 3:37%; P = NS). The paced P wave duration was increased in group 2 (129 +/- 14 ms vs group 3: 96 +/- 21 ms; P < 0.05). Paced P wave duration was a risk factor for postoperative AF (odds ratio 1.015; 95% CI 1.0021-1.028; P < 0.05). Analysis comparing the pacing groups revealed a reduction in AF during Bachmann's bundle pacing (50 vs 29%; P < 0.01). Pacing thresholds were significantly better at Bachmann's bundle compared to group 2. In conclusion, an anatomically guided pacing at the Bachmann's bundle does not reduce the overall incidence of postoperative AF compared to controls. However, the Bachmann's bundle offers favorable capabilities for postoperative a trial pacing, and thus it is a preferable site for electrode placement if postoperative atrial pacing is required.

Catheter ablation of VT by direct intramyocardial injection of ethanol during the chronic phase of myocardial infarction is feasible. It may be a useful tool for catheter ablation when the area of interest is located deep intramyocardially or subepicardially or when a more regional approach requires ablation of larger amounts of tissue.

Background: Different substrate based ablation strategies have been developed for ablation of ventricular tachycardia (VT) after myocardial infarction (MI). We investigated the “Dynamic Substrate Mapping (DSM)”, a tool integrated into the noncontact mapping (NCM) system. Methods: An electrophysiologic study (EPS) was performed 96 ± 10 days after experimental anteroseptal MI in 19 female sheep. Scar was defined by NCM during sinus rhythm. The area of scar was determined using the DSM tool with a cut-off of 50 %, 40%, 30% and 20% of the largest deflection of the unipolar electrogram. The scar was determined by either magnetic resonance imaging (MRI, n=9) or pathology (n=10). Areas determined by MRI or pathology and by DSM were compared. In 11 patients referred for ablation of VT simultaneous electroanatomical mapping and NCM was performed. The location of the low voltage area in the bipolar voltage map and the DSM were compared. Results: For all 19 animals a low voltage area was delineated with a cut off of 50% of the largest unipolar deflection. The low voltage area determined with DSM was greater then the scar determined by pathology or MRI (29,32 ± 28,83 cm 2 vs 8,52 ± 3,48 cm 2 . p < 0,05). Infarct scar determined by MRI or pathology was always located within the low voltage area determined by DSM. There was no correlation between the sizes of the low voltage area determined by pathology/MRI and DSM. Delineation of a low voltage area was not possible in all animals with a cut off of 40%, 30%, and 20%. In 11 patients, locations of the low voltage areas determined by bipolar voltage maps and DSM corresponded well. The area defined by DSM was larger then the area defined by bipolar voltage map. there was a good correlation between the size of the low voltage areas determined by bipolar voltage map and DSM for cut off values of 50% and 40% (r 2 = 0,66 and r 2 = 0,61; p<0,05). With a cut off of 30% and 20% of the largest unipolar deflection a low voltage area could not be defined for all patients. Conclusion: Sizes of abnormal myocardium defined by DSM do not correlate with scar areas determined by pathology or MRI. Areas of abnormal myocardium delineated by DSM are greater then areas defined with bipolar voltage map. A detailed description of the scar border zone with DSM during sinus rhythm alone is not feasible.

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