The Characteristic Study Of Epicardial Bipolar Electrogram Of Canine Earlist Atrial Activation

Rapid cardiac arrhythmias are common in clinic .This kind of arrhythmia can cause serious results if the heart rate is very high, especially to patients who are unsensitve to antiarrhythmic drugs. In 1987, Borgerefe and others cured a case of free right lateral pathway by radio frequency current ablation. The technology of radiofrequency ablation become an important method to cure rapid arrhythmia with the development of mapping technology. To focal arrhythmias, activation sequence mapping is a common method to determine the target sites of radiofrequency ablation. To complicity place of anatomy, we may not map the true earlist active site for anatomic elements but only relative early active site. It will be unsuccessful if we ablate and thus increase the times and decrease the success ratio of radiofrequency ablation. We found that the bipolar electrogram has its characteristic in clinic experiences. Activation sequence mapping combing with vector mapping may increase the successful rate of radiofrequency. This study take the site of pacing as the earlist atrial activation and the aim of this study is to explain the characters of the epicardial bipolar eletrogram and the regulation of its evolution and to improve the success rate of radiofrtquency ablation. materials and Methods:A total of 9 normal dogs with both gender (weight 15-21 kg )were in this study . After general anesthesia with sodium pentobarbital (30mg/kg im) (stop feeding 12 hours before procedures), these animals were intubated and mechanically ventilated with a pressure-controled ventilator. A right intercastal space thoarecotomy was performed, and 1 or 2 ribs were removed according to the degree of exposure. Pericardium was opened to cradle the heart. Then using the comb-like mapping catheter, pacing and recording epicardial bipolar electrogram at the junction between central of crista of right atria and tricuspid ring, at the same time recording 8 channel epicardial bipolar eletrograme and surface ECG (lead II). Pacing pole as the center of circle, beginning the direction to super vena cava and recording bipolar eletrogram every 300 till to the beginning site.Results:1. 12 traces were obtained from every canine, a total of 108 traces epicardial bipolar eletrogram obtained. The morphology of bipolar eletrogrames near to pacing pole present "Q" or "Qr" type and then "RS" or "Rs" type. The downward aptitude of initial vector of bipolar eletrogrames decrease with the recording pole far away from the pacing pole, and to certain distance the upward initial vector appearing and its aptitude increasing gradually and the morphology becoming more stable.We also found the morphology of the bipolar eletrogrames are similar to each other at the similar distance to pacing pole: the aptitude of downward initial vector decrease gradually and turn quickly from downward to upward.2. Within the range of 4mm(the pacing pole as the center of circle), the direction of initial vector is downward, presenting " Q" type or " Qr'type.3. Polarity reverse of bipolar electrograme take place at the distance of 10mm to pacing pole, presenting "Rs" type or "RS"type.4. The range of the initial downward vector to pacing pole between position 12, 6 and 3, 9 have no significant difference(Z= -0.164 P=0.869).5. The distance of polarity reverse to pacing pole between position 12, 6 and 3, 9have no significant difference(Z= -0.146 P=0.884).Conclusions:1. The characteristic of bipolar electrograms may be helpful to quickly and accurately local the radiofrequency ablation target of focal arrhythmia.2. The crista has no significant affection to epicardial bipolar eletrograms of paralleling and verticalling to it between the range of the initial down vector and the distance showing polarity reverse to pacing role.