Child ; Electrocardiography ; Humans ; Male ; Ventricular Fibrillation ; physiopathology

In our laboratory, the normal ECG signal, the ECG signals of ventricular tachycardia (VT) and of ventricular fibrillation (VF) are studied with the use of Hurst index value. The Hurst index values of the normal ECG signal, VT, VF are calculated separately. There exist obvious differences among the Hurst values of the three kinds of signals,but they are all higher than 0.5 which is a value indicating the long-term relevant character. The long-term relevant character of the normal ECG signal is the best, and the character of VT is better than that of VF. Therefore, the Hurst Index can be used as an identification criterion for distinguishing normal ECG, VT and VF.
Algorithms ; Electrocardiography ; methods ; Humans ; Signal Processing, Computer-Assisted ; Tachycardia, Ventricular ; diagnosis ; physiopathology ; Ventricular Fibrillation ; diagnosis ; physiopathology

Malignant arrhythmias and ventricular fibrillation are generally accepted as one of the major causes of death in cardiovascular diseases. Based on the H-H equations, the mathematical model of the cardiac cell action potential consists of the ion channels, pumps, exchangers and transporters that are closely connected with intra- and extra-cellular ion concentrations, the channel's conditions, nerve transductors and drugs. It can build the link between cell electrophysiology and clinical pathophysiology. By altering the cellular environments the computer simulating study on this kind of model can help us look into the electrophysiological changes of the cardiac tissue and even the whole heart and investigate the mechanisms of the cardiac arrhythmias as well. The components of the model and its computer simulating study are introduced in the paper.
Action Potentials ; Arrhythmias, Cardiac ; physiopathology ; Computer Simulation ; Heart ; physiopathology ; Humans ; Models, Cardiovascular ; Ventricular Fibrillation ; physiopathology

This study was performed to assess the influence of the cryoinjury on the dynamics of wavefronts and to determine whether they can convert ventricular fibrillation (VF) to ventricular tachycardia (VT) in fibrillating right ventricular (RV) of swines using an optical mapping system. A cryoinjury with a diameter of 12 mm was created on the epicardium of perfused RV of swines (n = 6) and optical mapping were taken from baseline until 10 minutes after the cryoinjury. Out of 35 cryoinjuries, the images were possible to be interpreted in 32. The optical action potential could not be observed in either the cryoinjury or peri-injury sites at 1 and 3 minutes, was observed in only the cryoinjury site at 5 minutes, and recovered in both sites at 10 minutes. The cycle length of the tachycardia was 135.9 +/- 23.6 msec at baseline, 176.2 +/- 79.3 msec at 1 minute, 187.6 +/- 97.9 msec at 3 minutes, 185.5 19.2 msec at 5 minutes, and 152.1 +/- 64.1 msec at 10 minutes. The cycle lengths at 1, 3, and 5 minutes after the cryoinjury were significantly more prolonged than that at baseline (p = 0.001, p = 0.006, p = 0.016). After the cryoinjury, the VF changed to VT in 9 (28.0%), and terminated in 2 (6.3%). These changes were observed mainly within 5 minutes after cryoinjury. The cryoinjury had anti-fibrillatory effects on the tissue with VF. This phenomenon was related to a decreasing mass and stabilizing wavefronts.
Ventricular Fibrillation/*physiopathology ; Tachycardia, Ventricular/*physiopathology ; Swine ; Heart Ventricles/*physiopathology/surgery ; Female ; Disease Models, Animal ; *Cryosurgery ; Animals

OBJECTIVETo evaluate the possible association between Tpeak-Tend (Tp-e) interval in surface standard ECG and cardiac events in patients with Brugada syndrome (BrS).

METHODTp-e interval in surface standard ECG was compared between BrS patients (n = 23, all males) and paroxysmal supraventricular tachycardia (PSVT) patients (n = 20, all males) as well as between BrS patients with (n = 16) or without (n = 7) cardiac events.

RESULTSThere was significant difference in Tp-e interval between BrS patients and PSVT patients [(109.57 +/- 22.86) ms vs. (88.50 +/- 13.08) ms, P < 0.05]. Tp-e interval was also significantly longer in BrS patients with cardiac events (syncope, clinical ventricular fibrillation and induced VF during electrophysiological study) than BrS patients without cardiac events [(118.12 +/- 20.40) ms vs. (90.00 +/- 15.27) ms, P < 0.05] while Tp-e interval was similar between BrS patients without cardiac events and PSVT patients (P > 0.05).

CONCLUSIONThe prolongation of Tp-e (> or = 120 ms) was associated with higher cardiac events in BrS patients.

Adult ; Brugada Syndrome ; diagnosis ; physiopathology ; Electrocardiography ; Humans ; Male ; Middle Aged ; Risk Factors ; Ventricular Fibrillation ; diagnosis ; physiopathology

Adult ; Bundle-Branch Block ; physiopathology ; Electrocardiography ; Humans ; Male ; Myocardial Infarction ; complications ; Syndrome ; Ventricular Fibrillation ; etiology ; physiopathology

This is a research with the aim of using joint entropy method to analyze the dynamical complexity information on the electrocardiogram signals recording of normal sinus rhythm (NSR), ventricular tachycardia (VT) and ventricular fibrillation (VF). We included the symbolic dynamical theory and surrogate data concept in it. By calculating the joint entropy between original and surrogate time series, we quantified the dynamical complexity of original series. By computer analysis of actual heartbeat rhythm data, the rationality of joint entropy method was confirmed. The results indicated that the joint entropy values of different signals can be of use in distinguishing the NSR, VT and VF signals.
Diagnosis, Differential ; Electrocardiography ; Entropy ; Humans ; Signal Processing, Computer-Assisted ; Tachycardia, Ventricular ; diagnosis ; physiopathology ; Ventricular Fibrillation ; diagnosis ; physiopathology

Based on human ventricular single cell mathematical model, a two-dimensional mesh of ventricular wall tissue was constructed. Through the increasing of the concentration of extracellular K+, we simulated the propagation of spiral wave in a condition under the influence of ischemia in 2-D human ventricular tissue. The results showed that along with the increase of ischemic level and size, the instability of spiral waves increased, and under the influence of certain ischemic level and size, spiral waves broke up. Through this simulation study of the effects of ischemia on spiral waves in 2-D human ventricular tissue, we explained the corresponding mechanism of the maintenance of ventricular tachycardia and the cause of ventricular fibrillation under the influence of ischemia.
Arrhythmias, Cardiac ; etiology ; physiopathology ; Computer Simulation ; Heart Ventricles ; Humans ; Models, Cardiovascular ; Myocardial Ischemia ; complications ; physiopathology ; Tachycardia, Ventricular ; etiology ; physiopathology ; Ventricular Fibrillation ; etiology ; physiopathology

Humans ; Myocardial Ischemia ; complications ; Tumor Necrosis Factor-alpha ; physiology ; Ventricular Fibrillation ; physiopathology

Ventricular fibrillation (VF) is the main cause of sudden death in cardiovascular diseases. The effects of electrophysiological heterogeneity and dynamic factors bring a lot of difficulties in understanding and revealing the mechanisms of VF. Cardiac short-term memory is one of the factors that make invalidation of restitution curve slope as the criteria for transition from ventricular tachycardia to VF. Therefore, investigation of inherent properties of short-term memory and its role in VF has great significance. In this paper we took advantage of the perturbed down-sweep protocol to measure dynamic and local S1S2 restitution curves on three widely used mathematical models to reveal their memory property. And by making abrupt change of the stimulation cycle length, we examined the attenuation process of the memory. The results showed, the rate-dependent action potendial duration (APD) is related with S1 pacing. The APD difference under different S2 cycle length is more pronounced with short S1 cycle length. Except the Luo-Rudy 1991 model, the Luo-Rudy 1994 and Noble 1991 models can at least reflect some of the short-term memory. And the memory attenuated in exponential way. Therefore, in quantitative electrophysiological study, these two models can be used in the future for investigating the characteristics of the short-term memory and its contribution to VF.
Action Potentials ; Computer Simulation ; Electrocardiography ; Heart Conduction System ; physiopathology ; Humans ; Models, Cardiovascular ; Models, Theoretical ; Myocardial Contraction ; physiology ; Ventricular Fibrillation ; physiopathology ; Ventricular Function