Discrete radiofrequency lesion at the atrial insertion site of the tendon of Todaro in the perfused rabbit preparation lengthens A-H interval, mimicking fast pathway input ablation. This study attempts to define the cellular electrophysiology of the ablation region prior to and after the elimination of fast AV node conduction. In six superfused rabbit AV node preparations, the cellular electrophysiology around the region of the atrial insertion to the tendon of Todaro was recorded using standard microelectrode technique prior to and after ablation. Before ablation, the action potentials recorded in the area of proposed lesion were exclusively from atrial or AN cells. At postablation, the superior margin of the lesion was populated with atrial or AN cells. AN, N, or NH cells bordered the lower part of the lesion. Electrophysiology of surviving cells at the edges of the lesion showed no significant changes in their Vmax, APD50 or APD90 and MDP from preablation values. Fast AV node pathway input ablation in the rabbit heart can be accomplished with a singular lesion around the atrial insertion site of the tendon of Todaro, involving atrial or AN cells. The results of the studies imply that inputs to the compact node may act as a substrate for successful ablation of AV node reentry tachycardia.
Action Potentials/physiology ; Animal ; Atrioventricular Node/surgery* ; Atrioventricular Node/physiology ; Atrioventricular Node/cytology* ; Catheter Ablation/methods* ; Electrophysiology ; Rabbits ; Recovery of Function ; Tachycardia, Supraventricular/surgery ; Tachycardia, Supraventricular/physiopathology

Atrioventricular Node ; physiopathology ; Cardiac Complexes, Premature ; diagnosis ; physiopathology ; surgery ; Catheter Ablation ; Humans ; Male ; Middle Aged

BACKGROUNDNominal atrioventricular (AV) interval in dual chamber pacemaker (DDD) is not the best AV delay in the majority of patients with atrioventricular block. To find a simple method for optimizing AV delay adjustment, we assessed surface electrocardiography (ECG) for optimizing AV delay during dual chamber pacing.

METHODSDDD pacemakers were implanted in 46 patients with complete, or almost complete, AV block. Optimal AV delay was achieved by programming an additional delay of 100 ms, to the width of intrinsic P wave or to the interval between pacing spike to the end of P wave on surface ECG. Left ventricular (LV) end diastolic and end systolic volumes, ejection fraction and diastolic parameters were measured by Doppler echocardiography during both nominal and optimal AV delay pacing.

RESULTSCompared to nominal AV delay setting, LV end diastolic volume increased [to (53.2 +/- 11.3) ml from (50.2 +/- 10.2) ml, P < 0.05], end systolic volume decreased [to (26.1 +/- 9.0) ml from (27.9 +/- 8.2) ml, P < 0.05] during adjusted AV delay pacing, resulting in an increase in LV ejection fraction [to (68.2 +/- 5.3)% from (64.5 +/- 4.3)%, P < 0.05]. LV diastolic filling and isovolumic relaxation time were not significantly changed.

CONCLUSIONOptimization of AV delay by surface ECG is a simple method to improve LV systolic function during dual chamber pacing.

Adult ; Aged ; Aged, 80 and over ; Atrioventricular Node ; physiopathology ; Cardiac Pacing, Artificial ; methods ; Electrocardiography ; methods ; Female ; Heart Block ; physiopathology ; therapy ; Humans ; Male ; Middle Aged ; Time Factors

PURPOSE: The optimal pacing mode with either single chamber atrial pacemaker (AAI or AAIR) or dual chamber pacemaker (DDD or DDDR) is still not clear in sinus-node dysfunction (SND) and intact atrioventricular (AV) conduction. MATERIALS AND METHODS: Patients who were implanted with permanent pacemaker using AAI(R) (n = 73) or DDD(R) (n = 113) were compared. RESULTS: The baseline characteristics were comparable between the two groups, with a mean follow-up duration of 69 months. The incidence of death did not show statistical difference. However, the incidence of hospitalization for congestive heart failure (CHF) was significantly lower in the AAI(R) group (0%) than the DDD(R) group (8.8%, p = 0.03). Also, atrial fibrillation (AF) was found in 2.8% in the AAI(R) group, which was statistically different from 15.2% of patients in the DDD(R) group (p = 0.01). Four patients (5.5%) with AAI(R) developed AV block, and subsequently switched to DDD(R) pacing. The risk of AF was lower in the patients implanted with AAI(R) than those with DDD(R) [hazard ratio (HR), 0.84; 95% confidence interval, 0.72 to 0.97, p = 0.02]. CONCLUSION: In patients with SND and intact AV conduction, AAI(R) pacing can achieve a better clinical outcome in terms of occurrence of CHF and AF than DDD(R) pacing. These findings support AAI(R) pacing as the preferred pacing mode in patients with SND and intact AV conduction.
Aged ; Atrial Fibrillation/complications/physiopathology ; Atrioventricular Node/*physiopathology ; Cardiac Pacing, Artificial ; Cohort Studies ; Female ; Follow-Up Studies ; Heart Failure/complications ; Humans ; Male ; Middle Aged ; Proportional Hazards Models ; Retrospective Studies ; Sick Sinus Syndrome/*physiopathology ; Treatment Outcome

Arrhythmia, Sinus ; physiopathology ; Arrhythmias, Cardiac ; physiopathology ; surgery ; Atrioventricular Node ; anatomy & histology ; physiology ; Catheter Ablation ; Electrophysiologic Techniques, Cardiac ; Electrophysiology ; Heart ; anatomy & histology ; physiology ; Heart Atria ; anatomy & histology ; Heart Conduction System ; physiology ; Humans ; Models, Cardiovascular ; Wolff-Parkinson-White Syndrome ; physiopathology

OBJECTIVETo observe the changes of surface ECG and cell couplings between sinoatrial node cells and myocardial cells following transplantion of pedicled autologous sinoatrial node tissue graft into the right ventricle of a canine model of complete atrioventricular block.

METHODSTen healthy dogs were randomized into transplantation group and control group. Pedicled autologous sinoatrial node tissue grafts were transplanted into the right ventricle in the transplantation group, while the sinoatrial nodes were only excised in the control group after placement of temporary myocardial pacing wires. The changes of surface ECG were observed at 1, 2, 3 and 4 weeks postoperatively. At 4 weeks, complete atrioventricular block was induced in the dogs by radiofrequency ablation of the His bundle. The heart rate of the dogs in both groups were recorded after the injection of isoproternol (ISO) from the femoral vein, and the transplanted tissue graft was observed under optical and transmission electron microscopes.

RESULTSNo significant changes occurred in the surface ECG. All the dogs showed ECG waveforms specific of complete heart block after the ablation, and the ventricular heart rates were similar between the two groups (P>0.05). The ventricular heart rate did not undergo obvious changes after ISO injection (P>0.05). The transplanted pedicled autologous sinoatrial node survived in the dogs and the sinoatrial node cells established desmosome junctions with the myocardial cells, but the number of junctions was not sufficient to support heart pacing.

CONCLUSIONDesmosome junction can occur between ventricular myocardial cells and sinoatrial node cells at the edge of transplanted pedicled autologous sinoatrial node tissue.

Animals ; Atrioventricular Block ; physiopathology ; surgery ; Cardiotonic Agents ; pharmacology ; Dogs ; Electrocardiography ; Female ; Heart Rate ; drug effects ; Heart Ventricles ; surgery ; Intercellular Junctions ; Isoproterenol ; pharmacology ; Male ; Myocardium ; cytology ; Sinoatrial Node ; cytology ; transplantation ; Tissue Transplantation ; Transplantation, Autologous