The properties of the normal and anomalous pathways were evaluated in 25 patients with accessory pathway to determine the factors influencing the development of orthodromic AV reentrant tachycardia, Nineteen patients had inducible PSVT and six patients had not. The results were as follows ; 1) Age, sex, and accessory pathway location of group A and group B were not different significanlty. 2) The presence of paroxysmal palpitation and the documentation of PSVT on surface ECG between group A and group B were signifcantly different. 3) The atrial effective refractory period(AERP), ventricular ERP, and antegrade ERP of accessory pathway of group A and group B were not different significantly. 4) Block cucle length and ERP of antegrade AV node(BCLa and ERPa) in groupA were shorter than those of antegrade accessory pathway. 5) There was no retrograde conduction through AV node in group A after block in retrograde accessory pathway. 6) Faliure to induce PSVT was accounted for by one of the following ; a) absence of antegrade conduction through AV node after a block of antegrade accessory pathway(4 patients) b) inadequate retrograde accessory pathway properties(3 patients) c) both inadequate antegrade AV nodal and retrograde accessory pathway(1 patient). Therefore, the occurrence of PSVT in patients with accessory pathway depends on the shorter BDLa and ERPa of AV node than those of accessory pathway and BCLr(299+/-51msec)and ERPr(310+/-41msec) of accessory pathway, but it dose not depend on the BCLa and ERPa of accessory pathway.
Atrioventricular Node* ; Electrocardiography ; Humans ; Tachycardia*

Verapamil is highly effective in terminating paroxysmal supraventricular tachycardia(PSVT) by its depressive action on the AV node. In other countries it is already the drug of choice if vagal manevers fail for conversion of PSVT. We evaluated therapeutic efficacy of intravenous verapamil in 30 patients with PSVT who visited Severance Hospital from november 1978 to November 1984. Twenty six of 30 patients(86.7%) had a restoration of normal sinus rhythm by intravenous verapamil without significant side effects. Thus intravenous verapamil is safe and extremely effective in terminating most PSVT.
Atrioventricular Node ; Humans ; Tachycardia, Supraventricular* ; Verapamil*

BACKGROUND: Second degree AV block is occasionally induced during AV nodal reentrant tachycardia by programmed electrical stimulation. This study was performed to determine the incidence, the block site, and the mechanism of AV block during AV nodal reentrant tachycardia. METHODS AND RESULTS: The study population was 67 consecutive patients with AV nodal reentrant tachycardia studied by programmed electrical stimulation. Among these patients, common types(slow pathway for anterograde and fast pathway for retrograde conduction) were 64 patients and uncommon types(fast pathway for anterograde and slow pathway for retrograde conduction) were 3 patients. Among 67 patients with AV nodal reentrant tachycardia 10 patients developed 2:1 AV block during tachycardia. The block site of AV block was infrai bundle in 9 patients and supraHis bundle in patient. There were intermittent aberrancies of RBBB and/or LBBB form during tachycardia in 5 patients with infraHis AV block. CONCLUSION: The occurrence of AV block during AV nodal reentrant tachycardia is not rare and might be related to the prematurity of atrial extrastimulation. The block sites of AV block were infraHis bundle in most cases and this finding suggests that distal common pathway of the reentry circuit is present in the AV node.
Atrioventricular Block* ; Atrioventricular Node ; Electric Stimulation ; Humans ; Incidence ; Tachycardia ; Tachycardia, Atrioventricular Nodal Reentry*

The electrical impulses of atrium arise from the sinus node, subsequently pass through the right and left atrium, and finally arrive at the atrioventricular node. The P wave is the summation of the electrical current generated by depolarization due to its passage through the atrial conduction pathway. It provides many clinical clues that may be useful for diagnosis of atrial, ventricular, or valvular heart diseases. This review article briefly describes the clinical implications, mechanism of genesis, and normal and pathologic features of the P wave.
Atrioventricular Node ; Diagnosis ; Heart Atria ; Heart Valve Diseases ; Sinoatrial Node

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

BACKGROUND AND OBJECTIVES: Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common regular supraventricular tachycardias in both the general population and elderly patients. The aim of this study is to investigate the clinical and electrophysiologic characteristics and efficacy of radiofrequency catheter ablation (RFCA) for treating AVNRT in the elderly. SUBJECTS AND METHODS: This study included 273 consecutive symptomatic AVNRT patients who underwent RFCA for the slow-pathway. The study population was divided into two groups: group I patients were younger than 65 years (n=227, average age: 44.6+/-12.9 years, male : female=89 : 138) and group II patients were older than 65 years (n=46, average age: 69.0+/-3.6, male : female=9 : 37). We compared the baseline clinical, electrocardiographic and electrophysiologic characteristics and the outcomes of RFCA between the two groups. RESULTS: The prevalence of a baseline prolonged PR interval (>200 ms) was not different between the 2 groups (1.8% vs. 6.5%, p>0.05). The baseline sinus cycle length, QT interval and AVNRT cycle length were significantly longer in group II than in group 1 (799.3+/-146.1 ms vs. 864.3+/-159.8 ms, 374.2+/-42.1 ms vs. 397.6+/-40.4 ms, 351.3+/-43.2 ms vs. 384.9+/-57.0 ms, respectively p<0.05). There was no difference in the rate of RFCA-related complications, including transient AV block. The incidence of AV block (> or =second degree) was not different between the two groups (4.0% vs. 6.5%, p>0.05). One patient in group I required permanent pacemaker implantation. CONCLUSION: RFCA in elderly patients is safe and effective as in younger patients. Therefore, performing RFCA for treating AVNRT should also be considered in the elderly patients.
Aged* ; Atrioventricular Block ; Atrioventricular Node ; Catheter Ablation* ; Electrocardiography ; Humans ; Incidence ; Male ; Prevalence ; Tachycardia ; Tachycardia, Atrioventricular Nodal Reentry* ; Tachycardia, Supraventricular

Hyperkalemia induces wide spectrum of electrocardiographic abnormalities on its severity. In general, hyperkalemia produces a gradual depression of the excitability, conduction velocity of the specialized pacemaker cells and conducting tissues throughout the heart. High serum potassium levels are thought to impair the conduction in the Purkinje fibers and ventricles more than in the AV node, although complete AV block can occur. So, hyperkalemia-induced complete AV block without prolongation of the QRS complex is a rare condition. We report a case of complete AV block without QRS complex widening in patient with hyperkalemia. To our knowledge, this is the first reported case in Korea.
Atrioventricular Block* ; Atrioventricular Node ; Depression ; Electrocardiography ; Heart ; Humans ; Hyperkalemia ; Korea ; Potassium ; Purkinje Fibers

Atrioventricular Block ; complications ; Atrioventricular Node ; surgery ; Heart Neoplasms ; complications ; surgery ; Humans

BACKGROUND AND OBJECTIVES: In cases of radiofrequency catheter ablation (RFCA) for patients with atrioventricular nodal re-entrant tachycardia (AVNRT), complete elimination of slow pathway is not always achievable. Furthermore, in situations of the so-called modified slow pathway, the underlying mechanism of tachycardia elimination remains unclear. SUBJECTS AND METHODS: Patients who underwent RFCA for AVNRT, and showed persistence of dual atrioventricular nodal physiology but no induction of AVNRT after ablation were enrolled. We measured electrophysiologic parameters before and after the ablation procedure. RESULTS: The study subjects included 31 patients (39% men; mean age 43±19 years). The RR interval, Wenckebach cycle length of AV node, slow pathway effective refractory period, maximal AH interval of fast pathway and slow pathway showed no significant changes before and after ablation. However, fast pathway effective refractory period (360±67 vs. 304±55, p<0.001) and differences between slow pathway effective refractory period and fast pathway effective refractory period (90±49 vs. 66±35, p=0.009) were decreased after slow pathway ablation. CONCLUSION: We suggest a possible relationship between the mechanism of tachycardia elimination in AVNRT and an alteration of the re-entrant circuit by removal of the atrial tissue in Koch's triangle. This may be a critical component of providing the excitable gap for the maintenance of tachycardia rather than the electrical damage of slow pathway itself.
Atrioventricular Node* ; Catheter Ablation ; Humans ; Male ; Physiology* ; Tachycardia*

BACKGROUNDAdvances in catheter ablation procedures for the treatment of supraventricular arrhythmias have created the need to understand better the morphological and electrophysiological characteristics of the inferior nodal extension (INE) and transitional cellular band (TCB) in the atrioventricular (AV) junctional area.

METHODSFirstly, we observed the histological features of 10 rabbit AV junctional areas by serial sections under light microscopy. Then we recorded the action potentials (APs) of transitional cells (TCs) in the INE, TCBs, AV node, and ordinary right atrial myocytes from the AV junctional area of 30 rabbits using standard intracellular microeletrode techniques.

RESULTSUnder light microscopy, the INE appeared to be mostly composed of transitional cells linking upward to the AV node. Four smaller TCBs originated in the orifice of the coronary sinus, the region between the septal leaflet of the tricuspid valve and the coronary sinus, the inferior wall of the left atrium, and the superior interatrial septum, respectively, all linking to the INE or the AV node. Compared with ordinary atrial myocytes, the AP of the TCs in both the INE and the TCBs had a spontaneous phase 4 depolarization (not present in ordinary atrial myocytes), with a less negative maximum diastolic potential, a smaller amplitude, a slower maximum velocity of AP upstroke, and a longer action potential duration at 50% repolarization (APD50) and at 30% repolarization (APD30). The AP characteristics of these TCs were similar to those of the AV node, except that the velocities of the phase 4 spontaneous depolarization were slower and their action potential durations at 90% repolarization (APD90) were shorter. Moreover, APD50 and APD30 of the TCs of the TCBs were shorter than in the case of TCs of the AV node.

CONCLUSIONSThe TCs of the INE and TCBs are similar to slow response automatic cells. They provide a substrate for slow pathway conduction. In addition, repolarization heterogeneity exists in the AV junctional area.