Electrocardiographic and electrophysiologic characterization of atypical atrial flutter in man: use of activation and entrainment mapping and implications for catheter ablation.

Introduction: Although the circuit in typical counterclockwise atrial flutter has been clearly delineated, the mechanisms of "atypical atrial flutters" have been less well characterized. The purpose of this study was to investigate the ECG and electrophysiologic (EP) characteristics of atypical atrial flutter.

Methods And Results: Thirty-three patients with at least one form of atypical atrial flutter underwent EP evaluation with multipolar atrial activation and entrainment mapping.

Mechanism of initiation of atrial flutter in humans: site of unidirectional block and direction of rotation.

Objectives: Using a standardized induction protocol, we investigated the mechanism of initiation of atrial flutter, before ablation, to determine the site of initiating unidirectional block and to test the hypothesis that the direction of rotation of atrial flutter depends on the pacing site from which it initiates.

Background: The high recurrence rate of atrial flutter after presumed successful ablation may be due to difficulty in reinduction after termination. In addition, induction of clockwise flutter is currently of unknown clinical importance.

Biophysical characteristics of radiofrequency lesion formation in vivo: dynamics of catheter tip-tissue contact evaluated by intracardiac echocardiography.

During clinical radiofrequency catheter ablation a wide range of delivered power may be necessary to achieve success despite an apparently stable catheter position on fluoroscopy. The purpose of this study was to use intracardiac echocardiography to characterize the relation between catheter tip-tissue contact and the efficiency of heating during applications of radiofrequency energy in vivo and to determine whether intracardiac echocardiography could be used prospectively to improve tissue contact. A closed-loop temperature feedback control system was used during radio-frequency applications at five anatomic regions in the right atrium of 15 anesthetized dogs to ensure achievement of a predetermined temperature (70 degrees C) at the catheter tip thermistor by automatic adjustment of delivered power (maximum 100 W).

Postextrasystolic U wave augmentation, a new marker of increased arrhythmic risk in patients without the long QT syndrome.

Objectives: We attempted to determine the correlation between the presence of postextrasystolic changes in the STU segment and a history of sustained ventricular arrhythmias.

Background: Postextrasystolic U wave augmentation (a marked increment in U wave amplitude after premature ventricular complexes [PVCs]) is an adverse prognostic sign in the "pause-dependent long QT syndrome." However, the prevalence of postextrasystolic changes in patients without the long QT syndrome is unknown.

Conduction barriers in human atrial flutter: correlation of electrophysiology and anatomy.

Animal models of atrial flutter and early mapping studies of human atrial flutter have suggested the importance of barriers in this reentrant arrhythmia. The consistency of rate and morphology of typical atrial flutter suggest a common anatomic substrate for this arrhythmia. The unique endocardial architecture of the right atrium provides anatomic barriers around which reentry occurs.

Regional entrainment of atrial fibrillation in man.

Introduction: The feasibility of entrainment of macroreentrant atrial arrhythmias such as atrial flutter is well documented. Recently, it has been shown that regional entrainment of atrial fibrillation is feasible in dogs.

Methods And Results: Three patients with chronic atrial fibrillation underwent electrophysiologic evaluation with attempted entrainment of atrial fibrillation prior to successful endocardial atrial defibrillation.

Activation and entrainment mapping defines the tricuspid annulus as the anterior barrier in typical atrial flutter.

Background: The importance of anatomic barriers in the atrial flutter reentry circuit has been well demonstrated in canine models. It has been shown previously that the crista terminalis and its continuation as the eustachian ridge form a posterior barrier. In this study we tested the hypothesis that the tricuspid annulus forms the continuous anterior barrier to the flutter circuit.

Pathological findings following slow pathway ablation for AV nodal reentrant tachycardia.

Introduction: AV nodal reentrant tachycardia is routinely cured using radiofrequency catheter ablation techniques. However, there remains controversy as to whether the reentrant circuit for this tachycardia exists solely in the AV node or whether perinodal atrial tissues are vital to the circuit. In addition, the effects of radiofrequency ablation of the slow pathway of AV nodal reentrant tachycardia on the AV node are not known.

Results of radiofrequency catheter ablation for atrial flutter.

RF catheter ablation for symptomatic typical atrial flutter is associated with a high procedural success rate, but a second RF procedure may be required in up to one third of subjects, particularly those with right atrial enlargement. In those subjects with both established AF and flutter, RF ablation for atrial flutter may decrease the recurrence rate of AF. However, patients remain at risk for the development of newly documented AF, most likely secondary to the high incidence of underlying structural heart disease.

Ablation of 'incisional' reentrant atrial tachycardia complicating surgery for congenital heart disease. Use of entrainment to define a critical isthmus of conduction.

Background: Intra-atrial reentrant tachycardia occurs frequently after surgery for congenital heart disease and is difficult to treat. We tested the hypotheses that intra-atrial reentrant tachycardia in patients who had undergone prior reparative surgery for congenital heart disease could be successfully ablated by targeting a protected isthmus of conduction bounded by natural and surgically created barriers and that entrainment techniques could be used to identify these zones.

Methods And Results: Eighteen consecutive patients with 26 intra-atrial reentrant tachycardias complicating surgery for congenital heart disease (9 atrial septal defect repair, 4 Fontan, 2 Mustard, 2 Senning, and 1 Rastelli procedure) underwent electrophysiological study and ablation attempts.

Radiofrequency catheter modification of the sinus node for "inappropriate" sinus tachycardia.

Background: Radiofrequency catheter ablation is the treatment of choice for patients with paroxysmal supraventricular tachycardias refractory to medical therapy. However, in symptomatic patients with inappropriate sinus tachycardia resistant to drug therapy, catheter ablation of the His' bundle with permanent pacemaker insertion is currently applied. We evaluated the safety and efficacy of radiofrequency modification of the sinus node as alternative therapy for patients with inappropriate sinus tachycardia.

Role of right atrial endocardial structures as barriers to conduction during human type I atrial flutter. Activation and entrainment mapping guided by intracardiac echocardiography.

Background: The importance of barriers in atrial flutter has been demonstrated in animals. We used activation and entrainment mapping, guided by intracardiac echocardiography (ICE), to determine whether the crista terminalis (CT) and eustachian ridge (ER) are barriers to conduction during typical atrial flutter in humans.

Methods And Results: In eight patients, ICE was used to guide the placement of 20-pole and octapolar catheters along the CT and interatrial septum and a roving catheter to nine sites: just posterior (1) and anterior (2) to the CT along the lateral right atrium, at the fossa ovalis (3), and just posterior and anterior to the ER at the low posterolateral (4 and 5), low posterior (6 and 7), and low posteromedial (8 and 9) right atrium.

Comparison of high energy direct current and radiofrequency catheter ablation of the atrioventricular junction.

Objectives: The goal of the study was to determine short- and long-term success and complications of radiofrequency atrioventricular (AV) junction catheter ablation and to compare these with those of high energy direct current catheter ablation.

Background: Catheter ablation of the AV junction with radiofrequency or direct current energy is an accepted treatment for drug-refractory supraventricular tachycardias. Few data are available on the long-term success and effects of radiofrequency ablation or its comparison with direct current ablation.

A blinded comparison of noninvasive, in vivo phosphorus nuclear magnetic resonance spectroscopy and the in vitro halothane/caffeine contracture test in the evaluation of malignant hyperthermia susceptibility.

Malignant hyperthermia (MH) is a potentially fatal, anesthetic-induced syndrome. Currently, the only accurate means of diagnosing susceptibility to this syndrome is the testing of biopsied skeletal muscle for its contracture response to halothane and caffeine. A less invasive means of diagnosis is needed.

Non-invasive evaluation of malignant hyperthermia susceptibility with phosphorus nuclear magnetic resonance spectroscopy.

Using in vivo 31P NMR spectroscopy, the authors compared the NMR spectra of the flexor muscles of the forearm from 13 humans characterized as MH susceptible on the basis of in vitro caffeine/halothane contracture tests with those from 25 normal controls. The levels of phosphocreatine (PCr), inorganic phosphate (Pi), and ATP during rest, graded exercise, and post-exercise recovery were measured in their forearms. MH susceptible subjects had significantly (P less than 0.

Naltrexone blocks the post-shock increase of ethanol consumption.

Attention has recently focused on the possibility of an interaction between ethanol and the endorphin system. In this study the opiate blocker naltrexone prevents the expected post-shock increase of ethanol consumption. This provides further evidence that endogenous opiates are involved in the voluntary drinking of ethanol in rats.