title: [Intra- and interatrial conduction - consequences for electrode placement].
abstract: Background Intra-atrial (IAA) and inter-atrial (IEA) conduction times during atrial pacing (P) are determined by conduction characteristics of IAA and IEA activation and by the atrial origin of stimulation. It seems that atrial P at identical locations can induce different conduction times dependent on the quality of the IAA and IEA conduction structures. Purpose of the study The aim of this study was to analyze the influence of pacing on normal IAA and IEA activation and the p-wave duration (PWD) in a sheep model. Different atrial wall contact pacing positions as well as a novel floating pacing configuration (BIdirectional MOnophasic ImpulSe: BIMOS; induced partial overlapping of electrical fields by splitting a conventional pacing impulse between three electrodes) were tested. The influence of pacing on a primary prolonged PWD is summarized, using published data. Methods Normal IAA, IEA conduction times and PWD: Twenty Merino sheep (4.6±0.7 years; 60.1±3.6 kg) were studied. EP catheters were placed under fluoroscopy close to the His Bundle (HBE), in the high right atrium (HRA), in the coronary sinus ostium (Cs-Os), and in the left lateral atrium (LLA). A modified single-VDD lead was introduced with the atrial ring electrodes floating in the high and mid right atrium. IAA (S/P-HRA, S/P-Cs-Os, S/P-HBE, S/P-floating), IEA conduction times (S/P-LLA), and P-wave duration (PWD) were assessed during intrinsic sinus rhythm (S), during bipolar cathodal P during wall contact in the HRA and in the Cs-Os, as well as during floating P with BIMOS configuration. Primary prolonged PWD: the influence of different novel pacing concepts ("biatrial" P, "dual site" P, "septal" P, "Bachmann bundle" P) on primary prolonged PWD were analyzed using data from the literature. Results Normal IAA and IEA conduction times and PWD: The mean PWD during S was significantly shorter than during HRA- (66.6±12.8 ms; vs. 116.2±11.1 ms; p<0.05) and Cs-Os-pacing (66.6±12.8 ms vs. 94.4±9.0 ms; p<0.05). Floating pacing with BIMOS showed no significant difference to S: 66.6±12.8 ms vs. 85.4±8.8 ms (p>0.05). PWD decreased significantly when the pacing protocol was changed from HRA pacing to floating pacing with BIMOS. The IEA conduction time (S/P-LLA) was also significantly shorter during S than during HRA pacing (34.7±14.7 ms vs. 89.7±13.5 ms; p<0.05), Cs-Os pacing (34.7±14.7 ms vs. 66.3±7.0 ms; p<0.05), and BIMOS pacing (34.7±14.7 ms vs. 61.3±12.7 ms; p<0.05). Compared to HRA pacing, floating pacing with BIMOS leads to a significant reduction of the PWD. Primary prolonged PWD: All new pacing concepts were developed primary for pace prevention of atrial arrhythmias. These pacing concepts reduce significantly primary prolonged PWD compared to S as known from the literature ("biatrial": S: 181±28 ms vs. P: 108±13 ms; p<0.05; "dual site": S: 120±12 ms vs. P: 103±17 ms; p<0.05, "septal": S: 132±23 ms vs. P: 84±14 ms; p<0.05; and "Bachmann bundle" S: 163±14.7 ms vs. P: 134±13.5 ms; p<0.05). Conclusion This study demonstrates the prolongation of primary normal IAA and IEA conduction times by pacing at different locations compared to S. Thereby floating pacing using BIMOS results in the smallest prolongation of conduction times. Pacing at the Cs-Os does not reduce the IAA conduction time but reduces the IEA conduction time in comparison to HRA pacing. On the other hand, the new pacing concepts for pace prevention of atrial fibrillation always showed a significant reduction of a primary prolonged PWD. This different behavior of IAA and IEA conduction times and PWD during pacing has to be taken into account before implantation of an atrial pacing lead.
authors.affiliation: Magdeburg, Germany, DE.
authors.forename: Dagmar
authors.initials: D
authors.lastname: Hartung
authors.forename: Wolfgang M
authors.initials: WM
authors.lastname: Hartung