The Study, Based On The Technique Of Epicardial Mapping Of Atrial Fibrillation Characterization Methods And Electrical Physiological Mechanism

Atrial fibrillation (AF) is the most common complex arrhythmia in clinical practice. The development of the therapy of AF is different from other medical studies, because it exists concurrently with the mechanism study and mapping technique renovation. Nowadays the medication effects of AF are very poor. However the recurrence of non-medication is also a ubiquitous trend and has a high risk of dangerous during operation. The most important reason of this case is that the mechanisms of AF are not well understood. In this dissertation, a whole-atrial epicardial mapping system has been developed, which can detect the electrical activity on the epicardial surface of atrium and show epicardial electrical activity visually and comprehensively. Animal tests are performed to study the occurrence and maintenance mechanism of AF. Mapping data representation methods and its optimization is also described to offer more information to characterize AF in clinical practice.Firstly, the development of 128-channel epicardial mapping system is introduced to explain the mapping technique. Because local epicardial mapping technique cannot show the complex electrical activity comprehensively during AF, 128-channel whole-atrial epicardial mapping system was constructed with 128-site epicardial mapping electrode patches. The system can directly show the epicardial electrical activities of pulmonary veins (PVs) and bi-atrium simultaneously. Animal tests proved that the system could describe the atrial electrical activity continuously by synchronous sample of multi-channel electrocardiogram (ECG) of epicardium. Result shows that this system can perform successfully in a surgical setting.Combined unipolar and bipolar mapping technique for recording epicardial electrical activity was applied to detect the propagation of depolarization wave over the epicardium. It can improve the electrode efficiency and the precision in epicardial mapping. Initial study of mapping data representation on AF was performed with recorded data from local atrial epicardial surface. Besides traditional isochronal maps, other methods were used to express the characteristics of AF which including dynamic isopotential maps, scattergraph and some statistical graphs. All these maps were used to describe the electrical activity during sinus rhythm and AF. All kinds of maps were presented clearly and the activity of sinus rhythm or AF can be seen quite differently. The dynamic isopotential map and the scattergraph can display the active electrical conduction of the atrium. Furthermore statistical results are also very useful for analysis the exciting mode of AF. The results will help us to find the optimal technique to diagnose the foci of AF for clinical therapy.Comentropy theory was applied to the study of data representation of AF through quantitative estimation of the statistical character of cardiac cycle. The spatial entropy distribution of cardiac cycle can reveal the complexity of electrical activity during AF and the regions with high value may be ectopic exciting foci or reentry paths. This study will be helpful for the radiofrequency ablation of AF. Result shows that methods for mapping data representation may be improved by comentropy theory.Finally, initial study of the mechanisms of AF is performed based on whole-atrial epicardial mapping technique. The occurrence mechanism of AF was operated by measuring local AF cycle length (AFCL) of different sites that arranged all over the epicardial surface of PVs and bi-atrium. To investigate the effects of the fat pad on AF triggered by rapid exciting of PVs, whole-atrial epicardial ECGs after fat pad stimulation were studied. Results show that during AF there exists an AFCL gradient while the shortest AFCL is PV and enhanced spontaneous neural activity at cardiac fat pad may serve as a substrate for focal PV triggering AF. The development process of AF may involve many mechanisms that interact each other. It also shows that the whole-atrial epicardial mapping system described here may be a useful tool for animal tests and clinical study of AF.Assembling the above-mentioned studies, the whole-atrial epicardial mapping technique will be helpful for the further investigation into the mechanisms of AF in animal tests and clinical research. Studies on mapping data representation may benefit the clinical basic research for mechanisms of AF and deciding the foci of AF undergoing radiofrequency ablation.