Atrial Fibrillation/surgery* ; Atrioventricular Node/surgery* ; Catheter Ablation ; Heart Failure/therapy* ; Humans

We reviewed the anatomical characteristics of the conduction system in the ventricles of human and ungulate hearts and then raised some questions to be answered by clinical and anatomical studies in the future. The ventricular conduction system is a 3-dimensional structure as compared to the 2-dimensional character of the atrial conduction system. The proximal part consisting of the atrioventricular node, the bundle of His and fascicles are groups of conducting cells surrounded by fibrous connective tissue so as to insulate from the underlying myocardium. Their location and morphological characters are well established. The bundle of His is a cord like structure but the left and right fascicles are broad at the proximal and branching at the distal part. The more distal part of fascicles and Purkinje system are linear networks of conducting cells at the immediate subendocardium but the intra-mural network is detected at the inner half of the ventricular wall. The papillary muscle also harbors Purkinje system not in the deeper part. It is hard to recognize histologically in human hearts but conducting cells as well as Purkinje cells are easily recognized in ungulate hearts. Further observation on human and ungulate hearts with myocardial infarct, we could find preserved Purkinje system at the subendocardium in contrast to the damaged system at the deeper myocardium. Further studies are necessary on the anatomical characteristics of this peripheral conduction system so as to correlate the clinical data on hearts with ventricular arrhythmias.
Arrhythmias, Cardiac ; Atrioventricular Node ; Bundle of His ; Connective Tissue ; Heart ; Heart Conduction System ; Humans ; Myocardial Infarction ; Myocardium ; Papillary Muscles ; Purkinje Cells ; Purkinje Fibers ; Tachycardia, Ventricular

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

Concealed bypass tract (CBT) results from incomplete development of the atrioventricular (AV) annulus. CBT conducts only in a retrograde direction, and therefore does not cause pre-excitation on standard electrocardiograms. The most common tachycardia associated with CBT is an orthodromic atrioventricular reentrant tachycardia (AVRT): a pathway involving anterograde circuitry through the AV node and His Purkinje system and retrograde conduction over the accessory pathway. Orthodromic AVRT accounts for approximately 90%-95% cases of AVRT. Most incidences of CBT occur at the left free wall. Vagal maneuvers and/or intravenous (IV) adenosine are recommended for first line acute management of AVRT. However, pharmacological therapy with IV diltiazem, verapamil, or beta blockers can also be effective for acute treatment for orthodromic AVRT in patients who do not show pre-excitation on their resting ECG during sinus rhythm. The first-line ongoing therapy for AVRT is catheter ablation of CBT; when catheter ablation is not indicated or preferred, oral beta blockers, diltiazem, verapamil, flecainide, propafenone, or amiodarone are recommended.
Adenosine ; Amiodarone ; Atrioventricular Node ; Catheter Ablation ; Diltiazem ; Electrocardiography ; Flecainide ; Humans ; Incidence ; Propafenone ; Tachycardia ; Tachycardia, Supraventricular* ; Verapamil

Among patients with Wolff-Parkinson-White syndrome, atrioventricular reciprocating tachycardia (AVRT) and atrioventricular nodal reentrant tachycardia (AVNRT) can coexist in a single patient. Direct transition of both tachycardias is rare; however, it can occur after premature atrial or ventricular activity if the cycle lengths of the two tachycardias are similar. Furthermore, persistent atrial activation by an accessory pathway (AP) located outside of the AV node during ongoing AVNRT is also rare. This article describes a case of uncommon atrial activation by an AP during AVNRT and gradual transition of the two supraventricular tachycardias without any preceding atrial or ventricular activity in a patient with preexcitation syndrome.
Atrioventricular Node ; Humans ; Pre-Excitation Syndromes ; Tachycardia* ; Tachycardia, Atrioventricular Nodal Reentry ; Tachycardia, Paroxysmal ; Tachycardia, Reciprocating ; Tachycardia, Supraventricular ; Wolff-Parkinson-White Syndrome*

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*

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

Veratrum patulum has toxicological relevance because of the potential for misidentification of this plant as mountain garlic. Veratrum patulum has an ester-alkaloid that provokes cardiac arrhythmias by excessive vagal stimulation and depression of the sinoatrial and atrioventricular nodes of the heart and hypotension, cardiomegaly. We report on a retrospective case of successful outcome in patients with veratrum patulum poisoning through active treatment from the early phase after ingestion. We report on a case involving a patient who experienced dizziness, dyspnea, hypotension, and elevation of cardiac enzyme, cardiomegaly. These cases were kept under observation and generally recovered with supportive care. We report on cases of veratrum patulum poisoning with review of literature.
Arrhythmias, Cardiac ; Atrioventricular Node ; Cardiomegaly ; Depression ; Dizziness ; Dyspnea ; Eating* ; Garlic ; Heart ; Humans ; Hypotension ; Plants ; Poisoning ; Retrospective Studies ; Veratrum*

A permanent pacemaker is a mainstay treatment for symptomatic bradyarrhythmia, including atrioventricular node blocks and sick sinus syndrome. Although this device was introduced to aid electrical recovery, pacemakers can cause mechanical dysfunction of the tricuspid valve, resulting in significant tricuspid regurgitation (TR). Because pacemaker-related TR is a correctable cause of right heart failure, it is of paramount importance to assess the presence or severity of TR and its association with pacemakers. However, acoustic shadowing from the pacemaker wire hampers the accurate visualization of TR jets, and increases the risk of failing to detect severe TR. Accordingly, goal-directed imaging with a high index of clinical suspicion should be performed when patients present with right heart failure after pacemaker implantation. In this issue of the Journal, the authors sought to investigate the frequency of aggravated TR in patients after pacemaker implantation. They also explored the predictors of TR aggravation, which might provide valuable information for identification of patients who require meticulous follow-up to allow timely intervention. These data regarding the predictive variables for pacemaker-related TR can serve as a roadmap for future studies to identify strategies for reducing the risk of significant TR, such as a tailored approach based on heart rhythm (bradyarrhythmia only vs. combined atrial fibrillation), pacemaker mode (VVI vs. DDD), the location of the pacemaker lead (apical vs. base), and the use of state-of-the art techniques (classical lead vs. leadless).
Acoustics ; Atrioventricular Node ; Bradycardia ; Follow-Up Studies ; Heart ; Heart Failure ; Humans ; Shadowing (Histology) ; Sick Sinus Syndrome ; Tricuspid Valve ; Tricuspid Valve Insufficiency*

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