Left anterior fascicular block (LAFB) is a heart disease identifiable from an abnormal electrocardiogram (ECG). It has been reported that LAFB is associated with an increased risk of heart failure. Non-specific intraventricular conduction delay due to the lesions of the conduction bundles and slow cell to cell conduction has also been considered as another cause of heart failure. Since the location and mechanism of conduction delay have notable variability between individual patients, we hypothesized that the impaired conduction in the ventricular myocardium may lead to abnormal ECGs similar to LAFB ECG patterns. To test this hypothesis, based on a computer model with a three dimensional whole-heart anatomical structure, we simulated the cardiac exciting sequence map and 12-lead ECG caused by the block in the left anterior fascicle and by the slowed conduction velocity in the ventricular myocardium. The simulation results showed that the typical LAFB ECG patterns can also be observed from cases with slowed conduction velocity in the ventricular myocardium. The main differences were the duration of QRS and wave amplitude. In conclusion, our simulations provide a promising starting point to further investigate the underlying mechanism of heart failure with LAFB, which would provide a potential reference for LAFB diagnosis.
Adult ; Bundle-Branch Block/diagnostic imaging* ; Computer Simulation ; Electrocardiography ; Heart/diagnostic imaging* ; Heart Atria/diagnostic imaging* ; Heart Conduction System/physiopathology* ; Heart Failure/diagnostic imaging* ; Heart Ventricles/diagnostic imaging* ; Humans ; Male ; Models, Anatomic ; Models, Theoretical ; Muscle Cells ; Myocardium ; Phantoms, Imaging ; Poisson Distribution

Sudden cardiac death （SCD）, most commonly seen in coronary heart disease, is a kind of sudden death caused by series of cardiac parameters, which usually combines with myocardial infarction. However, some SCDs （including early myocardial infarction） happen suddenly and cause death in a very short time. In these circumstances, typical morphological changes are lack in macroscopic or microscopic fields, which make such SCDs become the emphasis and difficulty in the present research. SCD caused by myocardial infarction and abnormalities of cardiac conduction system （CCS） is related to atherosclerosis of coronary artery closely. This paper reviews cardiac dysfunction caused by myocardial infarction and diseases of CCS from morphology and molecular biology, and explores potential relationship between them. This paper aims to provide clues to the mechanism of myocardial infarction related sudden death and possible assistance for forensic diagnosis of SCD.
Coronary Disease ; Death, Sudden, Cardiac/etiology* ; Heart Conduction System/physiopathology* ; Humans ; Myocardial Infarction/physiopathology*

OBJECTIVE: To analyze the incidence of long (short) PR interval in electrocardiogram among healthy people in Changsha and the clinical significance.
 METHODS: Twelve-lead body surface electrocardiogram was taken to measure the heart rates and PR intervals from 4 025 healthy individuals (age range from 6 min after birth to 83 years old) who performed physical examination from Jan, 1993 to Dec, 2012 in the Second Xiangya Hospital, Central South University. Statistics were analyzed by SPSS 16.0.
 RESULTS: The total incidence of short PR interval was 19.65% (791/4 025). The age group from birth to 13 years old had a higher incidence than the other age groups (χ2=432, P<0.01). The age groups from 1 month after birth and from 1 month to younger than 1 year-old displayed the highest incidences (43.29% and 44.34%, respectively). The lowest incidences were obtained from the 14-17 year-old, 40-49 year-old and 50-59 year-old groups (0.20%, 0.41%, and 0.33%, respectively). The total incidence of long PR intervals was 3.58% (144/4 025). The 1 year-old group had the highest incidence (6.74%), which decreased with the increase of age. The lowest incidence of long PR intervals occurred in the age group from 14-17 years old, which gradually increased after 50 years old. There were no significant differences in long (short) PR intervals between the gender (P>0.05).
 CONCLUSION The incidence of long (short) PR intervals varies in different age groups of healthy people. The incidences of long (short) PR intervals in children before 10 years old are higher than those in adults, especially the short PR intervals, as a result of the heart rate affected by childhood autonomic nervous function and the change in atrial volume with age. Adults have long (short) PR interval should be regularly followed-up to prevent cardiovascular events.
Adolescent ; Adult ; Aged ; Aged, 80 and over ; Child ; Child, Preschool ; Electrocardiography ; Heart Conduction System ; physiopathology ; Humans ; Incidence ; Infant ; Infant, Newborn ; Middle Aged ; Young Adult

The early cardiac biological pacemaker studies were mostly around HCN channel, and how to build a biological pacemaker through the enhanced If current. In recent years, however, people found that the genes of Tbx3 could play an important role in the development of cardiac conduction system, especially in processes of the maturity of the sinoatrial node and maintenance of its function. And the Tbx3 can further optimize the biological pacemaker. Therefore, it could be a new therapeutic focus in biological pacemaker and treatment of cardiac conduction system disease. This paper summarizes some of the latest research progress of the Tbx3 in biological pacemaker in recent years. We hope that this review could provide theoretical basis for the clinical applications of Tbx3.
Arrhythmias, Cardiac ; genetics ; Biological Clocks ; Brugada Syndrome ; Cardiac Conduction System Disease ; Heart ; physiopathology ; Heart Conduction System ; abnormalities ; Humans ; Sinoatrial Node ; T-Box Domain Proteins ; genetics

We discuss two cases of incessant atrial tachycardia (AT), including the presentation and clinical course. It is important to differentiate AT from other causes of supraventricular tachycardia, such as atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT), as it would have implications on clinical management. Electrocardiographic features of AT, especially the presence of an AV Wenckebach phenomenon with 'grouped beating', are critical for differentiating AT from AVRT and AVNRT. It is also vital to identify the P waves and their relations to QRS on electrocardiography, as this would aid in the differentiation of various supraventricular tachycardias.
Aged ; Diagnosis, Differential ; Electrocardiography ; Electrophysiology ; Female ; Heart Conduction System ; abnormalities ; Hemodynamics ; Humans ; Male ; Respiration ; Tachycardia ; diagnosis ; Tachycardia, Atrioventricular Nodal Reentry ; diagnosis ; Tachycardia, Supraventricular ; diagnosis ; Tricuspid Valve ; physiopathology

PURPOSE: Recent studies show positive association of early repolarization (ER) with the risk of life-threatening arrhythmias in patients with coronary artery disease (CAD). This study was to investigate the relationships of ER with myocardial scarring and prognosis in patients with CAD. MATERIALS AND METHODS: Of 570 consecutive CAD patients, patients with and without ER were assigned to ER group (n=139) and no ER group (n=431), respectively. Myocardial scar was evaluated using cardiac single-photon emission computed tomography. RESULTS: ER group had previous history of myocardial infarction (33% vs. 15%, p<0.001) and lower left ventricular ejection fraction (57+/-13% vs. 62+/-13%, p<0.001) more frequently than no-ER group. While 74 (53%) patients in ER group had myocardial scar, only 121 (28%) patients had in no-ER group (p<0.001). During follow up, 9 (7%) and 4 (0.9%) patients had cardiac events in ER and no-ER group, respectively (p=0.001). All patients with cardiac events had ER in inferior leads and horizontal/descending ST-segment. Patients with both ER in inferior leads and horizontal/descending ST variant and scar had an increased adjusted hazard ratio of cardiac events (hazard ratio 16.0; 95% confidence interval: 4.1 to 55.8; p<0.001). CONCLUSION: ER in inferior leads with a horizontal/descending ST variant was associated with increased risk of cardiac events. These findings suggest that ER in patients with CAD may be related to myocardial scar rather than pure ion channel problem.
Aged ; Arrhythmias, Cardiac/physiopathology ; Cicatrix/*physiopathology ; Coronary Artery Disease/*pathology/*physiopathology ; Death, Sudden, Cardiac/pathology ; Female ; Heart Conduction System/abnormalities/physiopathology ; Humans ; Male ; Middle Aged ; Myocardium/*pathology ; Prognosis

We investigated whether the presence of J wave on the surface electrocardiography (sECG) could be a potential risk factor for ventricular fibrillation (VF) during acute myocardial infarction (AMI). We performed a retrospective study of 317 patients diagnosed with AMI in a single center from 2009 to 2012. Among the enrolled 296 patients, 22 (13.5%) patients were selected as a VF group. The J wave on the sECG was defined as a J point elevation manifested through QRS notching or slurring at least 1 mm above the baseline in at least two leads. We found that the incidence of J wave on the sECG was significantly higher in the VF group. We also confirmed that several conventional risk factors of VF were significantly related to VF during AMI; time delays from the onset of chest pain, blood concentrations of creatine phosphokinase and incidence of ST-segment elevation. Multiple logistic regression analysis demonstrated that the presence of J wave and the presence of a ST-segment elevation were independent predictors of VF during AMI. This study demonstrated that the presence of J wave on the sECG is significantly related to VF during AMI.
Arrhythmias, Cardiac/*diagnosis ; Creatine Kinase/blood ; *Electrocardiography ; Female ; Heart Conduction System/*abnormalities ; Humans ; Male ; Middle Aged ; Myocardial Infarction/*diagnosis/pathology ; Retrospective Studies ; Risk Factors ; Ventricular Fibrillation/*diagnosis/pathology/physiopathology

Adult ; Arrhythmias, Cardiac ; diagnosis ; physiopathology ; Brugada Syndrome ; Cardiac Conduction System Disease ; Electrocardiography ; Female ; Heart Conduction System ; abnormalities ; physiopathology ; Humans ; Young Adult

Arrhythmias, Cardiac ; diagnosis ; genetics ; pathology ; Brugada Syndrome ; diagnosis ; genetics ; pathology ; Channelopathies ; diagnosis ; genetics ; pathology ; DNA Mutational Analysis ; Electrocardiography ; Genetic Testing ; Heart Conduction System ; physiopathology ; Humans ; Infant ; Long QT Syndrome ; diagnosis ; genetics ; pathology ; Muscle Proteins ; genetics ; Mutation ; NAV1.5 Voltage-Gated Sodium Channel ; genetics ; Sodium Channels ; genetics ; Sudden Infant Death ; etiology

OBJECTIVETo investigate the mechanism of drug-induced torsade de pointes (Tdp) in dogs.

METHODSIn arterially perfused canine left ventricular wedge preparations, the action potential duration (APD) of the endocardial (Endo), midmyocardial (M) and epicardial (Epi) myocytes, and transmural electrocardiogram (ECG) were recorded simultaneously. The effects of different concentrations of D-Sotalol on APD, transmural dispersion of repolarization (TDR), early after depolarization (EAD) and Tdp were observed.

RESULTSD-Sotalol prolonged APD of the Endo, M and Epi cells in a concentration-dependent manner from 0-100 µmol/L, and increased TDR due to a preferential APD prolongation of the M cells relative to Epi and Endo cells. The application of D-Sotalol elicited EAD, R on T ventricular premature beats, transmural reentry and Tdp in the M cells.

CONCLUSIONEAD and R on T ventricular premature beats induced by D-Sotalol in M cells triggers Tdp, which is maintained by TDR increment and transmural reentry.