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

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

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

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

OBJECTIVETo observe the action potential duration restitution (APDR) change and potential association with ventricular arrhythmia (VA) in Langendorff-perfused chronic heart failure rabbit hearts.

METHODSMale rabbits were randomly divided into two groups: control (CTL, n=15) group and chronic heart failure (CHF, n=15) group. CHF was induced by injecting isoproterenol (300 µg×kg(-1) ×d(-1)) for 14 days. Four weeks later, cardiac function and structure change of both groups were assessed by echocardiography. In the whole Langendorff-perfused hearts, the monophasic action potential (MAP) and the effective refractory period (ERP) were recorded from left anterior basal ventricle, left anterior free wall, left anterior apex and left posterior basal ventricle, left posterior free wall and left posterior apex, the APD curves were also constructed in both groups; at the six sites of every isolated heart, the programmed electrical stimulation and burst pacing were used to induce action potential duration (APD) alternans and VA, respectively.

RESULTSLeft ventricular ejection was reduced and end-dimension was enlarged in rabbits of CHF group. Compared with the same sites of CTL group, the 90% of MAP duration (MAPD90), the ERP, the max slope (Smax) of APDR curves, the pacing cycle length of inducing the APD alternans and the VAs were significantly increased (all P<0.05) in CHF group; the spatial dispersions of MAPD90, ERP and Smax of APDR curves in CHF group were also greater than in CTL group (all P<0.05).

CONCLUSIONThe ventricular APD alternans might be linked with occurrence of the VA in CHF rabbits. Increase of the Smax from APDR curves and the spatial dispersions of Smax in this CHF model might facilitate the development of ventricular arrhythmia.

Action Potentials ; Animals ; Arrhythmias, Cardiac ; physiopathology ; Electrocardiography ; Heart Failure ; physiopathology ; Heart Ventricles ; physiopathology ; Male ; Rabbits ; Ventricular Fibrillation ; 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

OBJECTIVEThe cardiac action potential (AP) and the intracellular Ca(2+) transient (CaT) are closely associated under normal physiological conditions, but not during ventricular fibrillation (VF). The purpose of this study was to determine whether this dissociation is directly related to the higher activation rate during VF.

METHODSWe optically mapped AP and CaT simultaneously in nine isolated rabbit hearts. Pinacidil, a K(ATP) channel opener, was used to shorten the action potential duration (APD) in order to capture tissue at fast pacing rates or to induce ventricular tachycardia (VT) comparable to VF activation rates. Mutual information (MI) was used to calculate the degree of AP and CaT coupling.

RESULTSPinacidil (40 micromol/L) infusion significantly shortened APD. The averaged cycle length (CL) of VF without Pinacidil was (77 +/- 13) ms, whereas the shortest CL achieved during VT under Pinacidil infusion was 76 ms. MIs during fast pacing (1.13 +/- 0.15) bits and fast VT (0.88 +/- 0.18) bits were higher than those during baseline VF (0.39 +/- 0.11) bits, VF with Pinacidil infusion (0.21 +/- 0.07) bits and VF after Pinacidil washout (0.36 +/- 0.15) bits. MIs during fast pacing or fast VT were higher than those of VFs at comparable dominant frequencies.

CONCLUSIONSCaT is closely associated with the AP during fast pacing and fast VT, but not during VF. The reduced MI during VF is not secondary to the fast rate of ventricular activation.

Action Potentials ; Animals ; Calcium ; metabolism ; In Vitro Techniques ; Myocardium ; metabolism ; Rabbits ; Ventricular Fibrillation ; metabolism ; physiopathology