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Dynamic epicardial mapping system is a useful instrument for studying electrophysiological characteristics of atrial fibrillation (AF). It is important to develop an optimal therapy for AF. The purpose of this research is to show the electrical activity on the epicardial surface of atrium and therefore find the appropriate technique or ablation procedures to prevent AF. It emphasizes on dynamic threedimensional (3D) holograph based on whole-atrial epicardial mapping. A system was designed to display successively either sampling waveform or the pattern of depolarization distribution. 64 unipolar electrodes arranged in eight flexible patches were adopted to detect signals. They can be located respectively on the surface of posterior and anterior LA or RA, and pulmonary veins (4 patches). Each electrode patch was designed to adaptable to the corresponding epicardial surface of canine atrium. Animal tests were operated on ten dogs in which chronic AF had been induced. Each 20-second sampling data during sinus or AF rhythm were recorded and stored for analysis. Multilevel B-splines were applied to compute the whole atria surface through a set of irregularly spaced point. Thus the 3D isopotential map was drawn to reflect the conduction of depolarization wave dynamically during AF. The propagation of electrical activity was different during sinus and AF rhythm. The results demonstrate that the system could find the pathway of AF through 3D dynamic exhibition. Nevertheless, 64 sites are not enough to detect the electrical activity thoroughly. A multi-site epicardial mapping system more than 128 channels is being developed for more exact mapping. [ABSTRACT FROM AUTHOR]

When heart is in ventricular fibrillation or atrial fibrillation, its electrical activities are very complex not only on spatial distribution but also on temporal variation. It is very difficult to find out its rules by traditional points by points mapping method. The 64/176-channel epicardial mapping system developed by Fudan University can be used to study the complex arrhythmias and has acquired some interesting results from the animal trials. The system includes a multi-electrodes patch, 64-channel ECG (electrocardiogram) signal amplifier, 80-channel A/D converter and a PC (personal computer). The electrode patch contains 8*8 array of electrodes with 2mm spacing. These 64 electrodes can be formed to 64 unipolar leads and 112 bipolar leads (totally 176 leads) for an electrocardiogram (ECG). Each electrode on the patch and the referenced electrode (which position is defined during the surgery) compose a unipolar lead. A pair of adjacent electrodes (include x-direction and y-direction) on the patch composes a bipolar lead. This unipolar leads and bipolar leads combined mapping technique make the independent channels of the ECG detecting greatly increased than the electrode quantity. The technique not only reduces the hardware and software expends but also increases the detecting precision. It uses finite hardware resources to detect depolarization wave from any way, any direction wherever in the whole mapping area. The system also can provide several techniques to analyze the depolarization wave signals from different sides, such as temporal, spatial and statistical. [ABSTRACT FROM AUTHOR]

During nearly one hundred years developments, the discharge wave-shapes of the defibrillator was improved from the AC to DC, from monophasic to biphasic. The truncated decaying exponential wave-shape has become the standard for implantable cardiac defibrillators (ICD) now and has been adopted by more and more automatic external defibrillators (AED). The defibrillation energy was decreased distinctly through these improvements. The low energy defibrillation has several superiorities: ➀ alleviating the shock harmfulness to the body, ➁ lighting the mental pressure of the sufferer, ➂ prolonging the battery's life of ICD. So the investigation on decreasing the defibrillation energy is very important. The mechanism of ventricular defibrillation is the shock electric field interacts with myocardium cells are not in absolute refractory and enforces these cells depolarizing and turning into refractory period. Then this myocardium cannot response the new stimulation from the other myocardium excitation. Lf there are enough myocardium cells being in refractory period, the ventricular fibrillation will stop. The goal of our research is decreasing the defibrillation energy markedly. We started with improving the wave-shapes and the current distribution of the defibrillator discharge. A multifunctional defibrillator for research has been designed and built to realize this goal. Several results have been obtained after a total of seven animal trials. During the animal trials, one of the discharge electrodes was put into the right ventricle transvenous and the other electrode was affixed to the left thorax's surface. The minimum Vf defibrillation energy threshold is 1.5J, and the average VF defibrillation energy threshold is 7.5±5J. The minimum VF defibrillation voltage threshold is 250V, and the average VF defibrillation voltage threshold is 360±100V. The minimum VF defibrillation threshold of amounts of electric charge is 0.006C, and the average VF defibrillation threshold of muounts of electric charge is 0.03±0.01C. [ABSTRACT FROM AUTHOR]