Electrocardiography ; methods ; Heart Conduction System ; physiopathology ; Heart Diseases ; diagnosis ; Humans

Cardiac resynchronization therapy (CRT) is a major breakthrough in therapy for patients with advanced congestive heart failure, however, a number of key clinical research questions remain, perhaps most importantly the issue of why apparently suitable patients do not respond to CRT. These issues are also relevant to patients who do respond to CRT as potentially their response might be further increased. Though patients do not respond to CRT because of many known postulated reasons, we review the importance of maintaining atrioventricular intrinsic conduction during CRT in this paper, which maybe is one of methods to reduce the rates of non-response to CRT.
Cardiac Resynchronization Therapy ; methods ; Heart Conduction System ; physiopathology ; Humans

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*

PURPOSETo evaluate and compare the effects of heart rate on conduction velocity in the cavotricuspid isthmus (CTI) and septum in patients with and without typical atrial flutter (AF) using electro-anatomic mapping (EAM) of the right atrium (RA).

METHODSTen patients (age 53+/-10 yrs, 7M/3F) with AF and 13 patients (age 51+/-11 yrs, 5M/8F) with atrioventricular nodal reentrant tachycardia (AVNRT) underwent conventional electrophysiological study, electro-anatomic mapping and radiofrequency ablation. Using EAMs obtained during coronary sinus pacing at pacing cycle length (PCL) 600 ms, 400 ms, and 300 ms, we evaluated conduction velocities in the CTI and septum of RA in 10 patients with AF and compared EAMs to 13 patients with AVNRT to determine whether the conduction slowing required to maintain AFL was related to changes in volume alone or altered RA electrophysiology.

RESULTSConduction velocities in CTI and septum were significantly slower at all PCL when AF was compared to AVNRT (*P<0.05). Additionally, in the AF group, septal conduction velocities were slower at PCL 600 ms and 400 ms, but not at 300 ms compared to CTI (*P<0.05). In AF, during PCL 300, conduction in CTI slowed significantly compared to PCL 600 and 400 ms such that there was no difference between CTI and septum at PCL 300.

CONCLUSIONSThere is slower conduction in the septum compared to the CTI in all patients. However, in patients with AF, there is significant slowing of conduction in the CTI and septum as well as decremental rate-dependent slowing of conduction in the CTI. These findings indicate that in addition to RA enlargement, changes in atrial electrophysiology distinguish AF patients from patients with AVNRT.

Adult ; Atrial Flutter ; physiopathology ; Female ; Heart Atria ; physiopathology ; Heart Conduction System ; physiopathology ; Heart Rate ; physiology ; Humans ; Male ; Middle Aged ; Tachycardia, Atrioventricular Nodal Reentry ; physiopathology ; Tricuspid Valve ; physiopathology

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

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.

Animals ; Dogs ; Electrocardiography ; Heart Conduction System ; Torsades de Pointes ; chemically induced ; physiopathology

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

In order to verify the hypothesis that left ventricular epicardial (LV-Epi) pacing and biventricular (BiV) pacing unavoidably influence the myocardial electrophysiological characters and may result in high risk of malignant ventricular arrhythmia, we calculated, in both normal mongrel dogs and dog models with rapid-right-ventricular-pacing induced dilated cardiomyopathy congestive heart failure (DCM-CHF), the monophasic action potential duration (MAPD) and the transmural dispersion of repolarization (TDR) in intracardiac electrogram together with the QT interval and T(peak)-T(end) (T(p(-T(e)) interval in surface electrocardiogram (ECG) during LV-Epi and BiV pacing, compared with those during right ventricular endocardial (RV-Endo) pacing. To prepare the DCM-CHF dog model, rapid right ventricular pacing (250 bpm) was performed for 23.6+/-2.57 days to the dog. All the normal and DCM-CHF dogs were given radio frequency catheter ablation (RFCA) to His bundle with the guide of X-ray fluoroscopy. After the RFCA procedures, the animals were under the situation of complete atrioventricular block so that the canine heart rates could be voluntarily controlled in the following experiments. After a thoracotomy, ECG and monophasic action potentials (MAP) of subendocardial, subepicardial and mid-layer myocardium were recorded synchronously in 8 normal and 5 DCM-CHF dogs during pacing from endocardium of RV apex (RV-Endo), epicardium of LV anterior wall (LV-Epi) and simultaneously both of the above (biventricular, BiV), the later was similar to the ventricular resynchronization therapy to congestive heart failure patients in clinic. The Tp-Te) meant the interval from the peak to the end of T wave, which was a representative index of TDR in surface ECG. The TDR was defined as the difference between the longest and the shortest MAPD of subendocardial, subepicardial and mid-layer myocardium. Our results showed that in normal dogs, pacing participating of LV (LV-Epi, BiV) prolonged MAPD of all the three layers of the myocardium (P<0.05) with the character that mid-layer MAPD was the longest and subepicardial MAPD was the shortest following subendocardial MAPD. At the same time, TDR prolonged from 26.75 ms at RV-Endo pacing to 37.54 ms at BiV pacing and to 47.16 ms at LV-Epi pacing (P<0.001). Meanwhile in surface ECG, BiV and LV-Epi pacing resulted in a longer Tp-Te) interval compared with RV-Endo pacing (P<0.01), without parallel QT interval prolongation. Furthermore, all the DCM-CHF model dogs showed manifestations of congestive heart failure and enlargement of left ventricles. Based on the lengthening of mid-layer MAPD from 257.35 ms to 276.30 ms (P<0.0001) and increase of TDR from 27.58 ms to 33.80 ms (P equals;0.002) in DCM-CHF model due to the structural disorders of myocardium compared with the normal dog, LV-Epi and BiV pacing also led to the effect of prolonging MAPD of three layers of the myocardium and enlarging TDR. From these results we make the conclusions that prolongation of MAPD of subendocardial, subepicardial and mid-layer myocardium and increase in TDR during pacing participating of LV (LV-Epi, BiV) may contribute to the formation of unidirectional block and reentry, which play roles or at least are the high risk factors in the development of malignant ventricular arrhythmia, especially in case of structural disorders of myocardium. These findings must be considered seriously when ventricular resynchronization therapy is performed to congestive heart failure patients.
Action Potentials ; Animals ; Bundle-Branch Block ; complications ; physiopathology ; Cardiomyopathy, Dilated ; complications ; physiopathology ; Dogs ; Female ; Heart Conduction System ; physiopathology ; Heart Failure ; etiology ; physiopathology ; Heart Ventricles ; physiopathology ; Male ; Torsades de Pointes ; physiopathology ; Ventricular Dysfunction, Left ; physiopathology ; Ventricular Function, Left

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

Maze operation could alter P wave morphology in electrocardiogram (ECG), which might prevent exact diagnosis of the cardiac rhythm of patients. However, characteristics of P wave in patients with sinus rhythm after the operation have not been elucidated systematically. Consecutive patients who underwent the modified Cox Maze operation from January to December 2007 were enrolled. The standard 12-lead ECG and echocardiography were evaluated in patients who had sinus rhythm at 6 months after the operation. The average axis of P wave was 65+/-30 degrees. The average amplitude of P wave was less than 0.1 mV in all 12-leads, with highest amplitude in V1. The most common morphology of P wave was monophasic with positive polarity (49%), except aVR lead, which was different from those in patients with enlarged left atrium, characterized by large P-terminal force in the lead V1. There were no significant differences in P-wave characteristics and echocardiographic parameters between patients with LA activity (30.6%) versus without LA activity (69.4%) at 6 months after the operation. In conclusion, the morphology of P wave in patients after Maze operation shows loss of typical ECG pattern of P mitrale: P wave morphology is small in amplitude, monophasic and with positive polarity.
Atrial Fibrillation/*physiopathology/*surgery ; Cardiovascular Surgical Procedures/*methods ; Electrocardiography/*methods ; Female ; Heart Conduction System/*physiopathology/*surgery ; *Heart Rate ; Humans ; Male ; Middle Aged ; Treatment Outcome