Norishige Morita

Parasympathetic blockade promotes recovery from atrial electrical remodeling induced by short-term rapid atrial pacing.

The purpose of the present study was to assess the influence of autonomic blockade on shortening of effective refractory period (ERP) induced by short‐term rapid atrial pacing (RAP) and its recovery process. Fifteen patients (8 men, 7 women, age 52 ± 16 years) without structural heart disease and without a history of atrial fibrillation were included in this study. All patients underwent RAP at a cycle length of 300 ms for 5 minutes, after which the ERP was measured in all patients at 1, 3, 5, 7.5, and 10 minutes following cessation of RAP. In ten patients, these RAP and measurements of ERPs were repeated after administration of propranolol (P) and subsequent administration of atropine (P + A), respectively. In the remaining five patients atropine (A) was given first and then the administration of propranolol followed (P + A). Relative to the baseline value, the ERP immediately after RAP did not differ significantly from the Control(C), P, A, or P + A (C, 79%± 8%; P, 82%± 9%; A, 80%± 6%; P + A, 82%± 13%). However, the ERP 3 minutes after cessation of RAP was significantly (P < 0.05) longer in A (93%± 4%) and P + A (97%± 5%) than that in C (86%± 5%) and P (86%± 5%). The recovery time for ERP to return to pre‐RAP value was significantly shorter during A and P + A than during either C or P (C, 536 ± 161 s; P, 503 ± 172 s; A, 282 ± 111 s; P + A, 291 ± 147 s; P < 0.05). Parasympathetic blockade may promote recovery from ERP shortening induced by short‐term RAP. (PACE 2004; 27:33–37)

Successful radiofrequency catheter ablation of an anteroseptal (superoparaseptal) atrioventricular accessory pathway from the left ventricular outflow tract.

This case report describes a patient with Wolff‐Parkinson‐White syndrome in whom the ECG exhibited a typical pattern of an anteroseptal (superoparaseptal) accessory pathway. Successful radiofrequency catheter ablation was achieved from the septal side of the left ventricular outflow tract. It might be worthwhile to map the left side of the anterior septum if an accessory pathway potential is not appreciable along the tricuspid annulus to avoid the potential complication of AV block in patients with a typical anteroseptal accessory pathway ECG pattern. (PACE 2004; 27:668–670)

The role of Purkinje fibers in the emergence of an incessant form of polymorphic ventricular tachycardia or ventricular fibrillation associated with ischemic heart disease

Background: The clinical and electrophysiological characteristic of ventricular premature contractions (VPCs) which trigger the incessant form of polymorphic ventricular tachycardia (VT), so‐called “electrical storm” associated with ischemic heart disease, remains unclarified. The aim of this study was to evaluate those matters and the possible role of the Purkinje network in the emergence of an electrical storm.

Anatomic and Electrophysiologic Evaluation of a Right Lateral Atrioventricular Mahaim Fiber

We report a patient who underwent an electrophysiologic study and radiofrequency catheter ablation for a right lateral Mahaim fiber. During sinus rhythm with overt preexcitation, propagation mapping was performed in the right ventricle using a three‐dimensional electro‐anatomical mapping system (CARTO). Small discrete potentials, which reflected the excitation of the Mahaim fiber, could be recorded along the line from the vicinity of the parental tricuspid annulus to approximately one‐third of distal site from the base to the apex. The relationship of the timing of its potential to the anatomical location could be disclosed on recordings of the local electrogram and anatomical map.

Clinical significance and contributing factors of long-term variability in induced ventricular tachyarrhythmias.

Introduction: Ventricular arrhythmias induced during electrophysiologic study (EPS) may vary over time, making arrhythmia induction studies unreliable. The aim of this prospective study was to clarify the clinical significance of long‐term variability in induced arrhythmias and to elucidate factors determining this variability.

Pronounced Effect of Procainamide on Clockwise Right Atrial Isthmus Conduction Compared with Counterclockwise Conduction: Possible Mechanism of the Greater Incidence of Common Atrial Flutter During Antiarrhythmic Therapy

Bidirectional Conduction Property of Low RA Isthmus. Introduction: It has been shown that the induction rates of common and reversed common atrial flutter are comparable during baseline control study, whereas the rate is significantly greater for common flutter than reversed common flutter during administration of antiarrhythmic agents. The mechanism of this discrepancy is not known.

Analysis of Posterior Mitral Annular Activation During Entrainment and Catheter Ablation of Mitral Isthmus Ventricular Tachycardia Using a Coronary Sinus Catheter

A detailed analysis of the ventricular activation along the posterior aspect of the mitral annulus was made using a multipolar catheter positioned in the coronary sinus in a patient with mitral isthmus ventricular tachycardia (VT) associated with a remote inferior myocardial infarction and prior cryosurgical ablation for the elimination of a different preexisting VT. A change in the timing and sequence of the ventricular activation along the isthmus could be observed during induction of the VT and entrainment pacing. A radiofrequency (RF) current application directed at the posterolateral region of the isthmus successfully eliminated this tachycardia. During the RF delivery, complete conduction block was confirmed by a sudden change in the activation sequence during sinus rhythm.