This paper applied the Shannon Entropy based on the cross correlation to analyze the epicardial signals from anterior wall of the canine atria. The result demonstrated that during sinus rhythm, the stability level of the correlation among signals from anterior right atria is much higher than the signals from anterior left atria. All the signals from the anterior wall descended when the rhythm changed from sinus rhythm to atrial fibrillation(AF). However, there were some regions still having a stable correlation during AF. The results will be helpful to enhance understanding of the correlation characteristic of AF.
Animals ; Atrial Fibrillation ; physiopathology ; Dogs ; Entropy ; Heart Atria ; physiopathology ; Pericardium ; physiopathology

If heart function is normal, the atrial cells are excited in a stable rhythm. But this would change during atrial fibrillation. In this paper, after comparing with the method of characteristic point, we use the dominant frequency method to analyze the activation pattern under sinus and atrial fibrillation rhythm in different parts of atria based on epicardial mapping system. It is found that the activation rhythm changes a lot in different parts of atria, and the automaticity of atrial cells change obviously in somewhere. The result shows that dominant frequency method is very suitable for the analysis of atrial fibrillation signal. What's more, we also roughly discuss the role of this method in exploring the driving sources during atrial fibrillation.
Atrial Fibrillation ; Epicardial Mapping ; Heart Atria ; Humans

Objective To explore a method for real-time pretreatment and character extraction of epicardial signals and promote the research on the electrophysiological mechanism of atrial fibrillation (AF).Methods Firstly,an analysis was made to get the properties of epicardial signals. Then,a method based on template matching was used to extract atrial activities from epicardial signals. At last,the feature points of atrial activities could be recognized.Results The correctness of recognizing feature points of sinus rhythm and AF were 99.7% and 97.0% respectively. Furthermore,only 1~2 s were cost to compute a 10-second data record with this method.Conclusion The proposed method can extract crucial information about atrium depolarization from epicardial signals and is adequate for online analysis.

Objective To investigate the imaging features of gastrointestinal stromal tumors.Methods The clinical and imaging data of 22 patients with gastrointestinal stromal tumors(GIST)proven pathologically were retrospectively analyzed.Results Endophytic masses were displayed in 4 patients,exophytic masses in 19 patients,and exo-and endophytic masses in 3 patients.The images from the gastrointestinal radiography displayed the filling defect mass and the local mucosal fold that was pressed,pushed or even destroyed.The CT imaging showed uniform or inhomogenous tumors with calcification or necrosis and cystic changes.The enhanced CT scanning displayed different enhancements of the lesions and the enhancements were stronger in venous phase than in arterial phase.Ultrasonographical images indicated solid or cystic-solid masses with moderate-or low-level echo.Conclusion The menifestations on the images of gastrointestinal stromal tumors are helpful to diagnose the disease.

Objective To find a method for real-time measurement of epicardial electrical activity suitable for clinical application.Method Combined unipolar and bipolar mapping technique for recording epicardial electrical activity was applied to detect the propagation of depolarization wave over the epicardium.Epicardial signals from 4 pigs were sampled simultaneously during sinus rhythm or atrial fibrillation(AF).Result Active isopotential map showing the spread of excitation on epicardial surface was demonstrated and correlation analysis data were obtained.The difference in correlation coefficients between adjacent sites was evident during sinus rhythm(above 0.8) and AF(about(0.5).) Conclusion The result shows that combined unipolar and bipolar technique improves the electrode efficiency and the precision in epicardial mapping.Distribution of depolarization wave or the reentry pathway during complex arrhythmia may be revealed by correlation analysis.

Image segmentation is a key step for image processing. This study developed an improved region growing algorithm to extract the outline of the heart for 3D-modeling which based on the acquisition of canine cardiac CT images from animal experiment. In this paper the method was also compared with the classic algorithm of threshold segmentation. The result showed that the method can be used for the 3D display technology of cardiac electrical activity in clinical electrophysiology mapping.
Algorithms ; Animals ; Dogs ; Electrophysiology ; Image Processing, Computer-Assisted ; Imaging, Three-Dimensional ; Models, Anatomic ; Models, Cardiovascular ; Tomography, X-Ray Computed

The design of portable and low power consumption 12-lead ECG is based on the digital signal processor TMS320C5515 and the analog front end ADS1298. The ADS1298 collects the ECG signals and deliver them to TMS320C5515. The preprocessed ECG signals are displayed real-time on a LCD and can be stored without compression for a long time. The ECG signals can also be sent to an up computer by a USB connector so that ECG data can be analyzed offline. The system has small volume, high precision and low power consumption.
Electrocardiography, Ambulatory ; instrumentation ; Equipment Design ; Signal Processing, Computer-Assisted ; instrumentation ; Software Design

Objective To explore the mechanism underlying the superiority of the biphasic waveform to monophasic waveform in defibrillation.Method The Luo-Rudy model was adjusted so that it could be used to study defibrillation.Based on the adjusted model the effects of different defibrillation waveforms on cell action potential duration(APD) were studied.Result Biphasic electrical field pulse extended the APD longer than that with monophasic one.Moreover,biphasic waveforms with different strengths could prolong the APD almost equally,while monophasic pulses with different strengths showed different ability to prolong the APD and the spatial distribution of the APD became dispersed.It was also found that the strength of electrical fields pulse contributed much to the change of APD while the duration showed little effect.Conclusion The clinical superiority of biphasic pulses to monophasic pulses in defibrillation is resulted from its ability to prolong the time course of the APD and more importantly,it causes even spatial distribution of the APD.

Objective To study the complex restitution relation between the present action potential duration (APD) and its previous diastole interval (DI) and APD. Method The Luo-Rudy model was paced with different protocols to draw the coordinate curves between the present APD and its first previous DI. These curves were fit with the artificial neural network (ANN). Result Different pacing protocols caused different coordinate curves, and there was no one-to-one relation between pre-sent APD and its first previous DI. ANN fits these curves satisfactorily. Conclusion There is a complex relation between the present APD and the APDs and Dis of the first three previous beats. This relation can be modeled accurately with ANN.

This Paper brings forward a new technology of EEG Telemetry. Using two FDM channels, the signals can be transmitted through public telephone lines: the EEG signals are transmitted by TDM technology in one channel; the parametes are transmitted to the receiver for identification of data or synchronization in the other channel synchronously. This technology can satisfy almost any routine clinic needs, and also the quahty of transmission is nearly perfect: the distortion is little; distinct noise pollution and shift of base-line do not exist, which is valuable in medical application.