Frequency coherence mapping of termination of induced canine atrial fibrillation

Multiple unipolar electrodes were used to measure and record right atrial activation in canine atrial fibrillation (AF) model. Twenty open-chest dogs with induced AF by extra-stimulation under continuous infusion of methylacetylcholine. After AF sustained for 5 minutes, 10 dogs received intravenous procainamide and 10 dogs received d, l-sotalol for AF termination. Unipolar electrograms were recorded at baseline and during infusion of antiarrhythmic drugs, using a 120-electrode array (electrode spacing is 3 mm) placed on the right atrial free wall. In this study, we used magnitude-squared coherence in frequency (MSCF) mapping to show the frequency distribution during AF. The data were digitally filtered The spectra were limited within 2-15 Hz for AF signals. We chose each electrode as a reference, and established its MSC spectra with other signals. Then, from 120 MSC spectra at dominant frequency (DF) (MSC>0.5) of reference to compose a DF mapping. The mappings were added together for the same DF. We used the MSCF map to denote four periods: (1) normal sinus rhythm; (2) AF baseline; (3) before AF termination; (4) sinus rhythm following termination. The dominant area (DA) including SA node was chosen with the isochronal maps. The results show that the DA has characteristics different from other sites, when AF terminated The signals of DA are regulated with frequency within 7∼9 Hz (p<0.05) and have longer cycle lengths than other sites (p<0.05). When AF is converted to sinus rhythm, SA node will be re-controlled into the new tempo in the atrium. We demonstrated that an area contains the SA node would be the dominant area in AF termination. Increased organization of electrical activation in DA may be the underlying mechanisms of drug-induced termination of AF.