New perspectives on catheter-based ablation of ventricular tachycardia complicating Chagas' disease: experimental evidence of the efficacy of near infrared lasers for catheter ablation of Chagas' VT.

Chronic Chagas' myocarditis can alter the myocardial substrate in a way that facilitates the emergence of fatal VT in a way similar to the long-term consequences of myocardial infarction. Post-myocardial infarction and Chagas' VT share many similarities: they are both macroreentrant circuits, entrainable, involving any wall segment from the endocardium to the epicardium. However, as compared to patients with post-MI VT, Chagasic patients tend to be younger and have a higher left ventricular ejection fraction.

Dielectrical spectroscopy of canine myocardium during acute ischemia and hypoxia at frequency spectrum from 100 kHz to 6 GHz.

We studied dielectrical properties of canine myocardium during acute ischemia and hypoxia using dielectrical spectroscopy method at frequency spectrum from 100 kHz to 6 GHz. This study was conducted on a group of six canines with acute ischemia and seven canines with hypoxia. Hypoxia (10% for 30 min) decreases myocardial resistance (rho), while the dielectrical permittivity (epsilon') of the myocardial tissue remains statistically unchanged.

The nonpharmacologic management of the permanent form of junctional reciprocating tachycardia.

The permanent or recurring form of junctional reciprocating tachycardia (PJRT) is an incessant tachycardia that has characteristic clinical and electrophysiologic features of PJRT. Each patient demonstrated near-incessant reciprocating tachycardia with a 1:1 atrioventricular (AV) relationship and with a retrograde P wave (P') occurring closer to the succeeding QRS complexes (i.e.

Effects of energy delivery via a His bundle catheter during closed chest ablation of the atrioventricular conduction system.

In this paper we summarize our experience and report the characteristics of energy delivery in 23 patients who have undergone closed chest ablation of the normal atrioventricular (AV) conduction system for the treatment of refractory supraventricular arrhythmias. The induction of AV block was achieved by the synchronous delivery of electrical energy with a damped sinusoidal waveform utilizing a standard direct current defibrillator and a standard tripolar His bundle catheter. The procedure was well tolerated, though one patient experienced ventricular fibrillation, which was uneventfully converted with external paddles.

Transvenous ablation of the atrioventricular conduction system in dogs: electrophysiologic and histologic observations.

The correlation of histologic and electrophysiologic findings in dogs undergoing transvenous ablation of atrioventricular (AV) conduction has not been described. The creation of complete AV block in 10 dogs was attempted by delivering a direct-current shock transvenously through a standard tripolar electrode catheter. The catheter was positioned to record the largest unipolar atrial and His bundle electrograms.

Localization of septal pacing sites in the dog heart by epicardial mapping.

To examine whether different septal pacing sites could be distinguished by their epicardial activation patterns, six to eight stimulating electrodes were placed throughout the septum in seven open chest dogs. Unipolar electrograms were obtained from 52 epicardial electrodes during pacing from each stimulating electrode and isochronous epicardial maps were constructed. The location of each stimulating electrode was found by dissection, and its distance from the overlying epicardium was measured.

The induction of atrial flutter and fibrillation and the termination of atrial flutter by esophageal pacing.

In patients with Wolff-Parkinson-White syndrome (WPW), it is important to assess the ventricular response during atrial flutter or fibrillation since conduction across the accessory pathway during these atrial rhythms may cause hemodynamic impairment or life-threatening ventricular arrhythmias. We have recently reported the effective use of an esophageal electrode in pacing the atrium. In this study we prospectively assessed the ability to induce atrial flutter and fibrillation by esophageal pacing in 23 patients with WPW or other electrophysiological abnormalities.

The electrophysiologic basis and management of symptomatic recurrent tachycardia in patients with Ebstein's anomaly of the tricuspid valve.

Twenty-two patients with Ebstein's anomaly were evaluated because of recurrent tachycardia. A total of 30 accessory pathways were present in 21 of the 22 patients. Twenty-six accessory pathways were of the atrioventricular (A-V) type while four were Mahaim fibers.

Catheter technique for closed-chest ablation of the atrioventricular conduction system.

This report describes a catheter technique for ablating the His bundle and its application in nine patients with recurrent supraventricular tachycardia that was unresponsive to medical management. A tripolar electrode catheter was positioned in the region of the His bundle, and the electrode recording a large unipolar His-bundle potential was identified. In the first patient, two shocks of 25 and 50 J, respectively, were delivered by a standard cardioversion unit to the catheter electrode, resulting in an intra-His-bundle conduction defect.

Techniques of intraoperative electrophysiologic mapping.

Cardiac mapping during sinus rhythm and during spontaneous or induced ventricular arrhythmias is a promising technique that offers a variety of potential strategies to improve our ability to locate abnormal areas in the heart that are the seat of arrhythmias. If surgical procedures are to become more limited in scope in an attempt to salvage myocardium, mapping will need to be used to a greater extent. However, it remains to be established which mapping technique will prove most sensitive and specific in detecting sites of arrhythmia, and whether the localizing method used allows a more directed surgical intervention to be successful.

His bundle interruption for control of inappropriate ventricular responses to atrial arrhythmias.

Forty-two patients with life-threatening or disabling atrial arrhythmias are discussed. Fifteen had Kent bundles as the basis for the reentry tachycardia, while 27 had arrhythmias that originated in or above the atrioventricular (AV) node. Nineteen of the latter had an AV node that conducted atrial impulses rapidly to the ventricle.

A digital timer for on-line interval measurement.

A digital timer suitable for on-line timing of cardiac intervals on a beat-by-beat basis is described in detail. The device expedites the process of on-line data acquisition and analysis of mapping and timing of atrial and/or ventricular multiple data points for electrophysiologic surgery. An unusual feature allows interval measurement between a fixed reference point and varying data points to be expressed as a positive value regardless of whether the data point occurs before or after the reference.

Role of Mahaim fibers in cardiac arrhythmias in man.

Twelve patients with evidence of Mahaim fibers are reported, six with nodoventricular (NV) fibers and six with fasciculoventricular (FV) fibers. All patients with NV fibers had left bundle branch block morphology, and a sustained reentrant tachycardia with this morphology was proved in each case. In three of the six, ventriculoatrial dissociation occurred during tachycardia.

The transition to ventricular fibrillation induced by reperfusion after acute ischemia in the dog: a period of organized epicardial activation.

Ventricular fibrillation was induced in eight of 10 open-chest dogs by reperfusion after a 15-minute occlusion of the proximal circumflex coronary artery. Simultaneous recordings were made from 27 epicardial electrodes spaced over both ventricles. Analysis of the initial 1.

The sock electrode array: a tool for determining global epicardial activation during unstable arrhythmias.

The conventional technique for mapping the sequence of epicardial activation uses a hand-held electrode moved over the heart to record from a number of epicardial sites one at a time, and requires 5-15 minutes to record from 50 or more sites distributed over the entire ventricular epicardium. This method is inadequate for arrhythmias that are transient or vary from beat to beat. To overcome these limitations the "sock electrode array," a contour-fitting sock containing 26 or 52 electrodes, has been developed.

Use of the esophageal lead in the diagnosis of mechanisms of reciprocating supraventricular tachycardia.

Recent studies have emphasized the role of concealed accessory pathways in reciprocating supraventricular tachycardia. Diagnosis has generally required multicatheter electrophysiologic study. We recorded esophageal electrograms during study in 16 patients with reciprocating tachycardia due to reentry using an accessory atrioventricular pathway, and in 12 patients with reciprocating tachycardia due to reentry in the AV node.

Accessory atrioventricular pathway in an infant: prediction of location with body surface maps and ablation with cryosurgery.

A 10-month-old infant with multiple muscular ventricular septal defects, congestive heart failure, Wolff-Parkinson-White syndrome, and supraventricular tachycardia is presented. The site of ventricular pre-excitation was predicted by analysis of ST-T wave isopotential body surface maps to be in the posterior free wall of the right ventricle. The site was confirmed by epicardial mapping of the ventricles during surgery.

Cryosurgical ablation of the atrioventricular node-His bundle: long-term follow-up and properties of the junctional pacemaker.

We used a cryosurgical technique to ablate the atrioventricular (AV) node-His bundle in twenty-two selected patients with disabling supraventricular tachyarrhythmias unresponsive to medical management. Successful AV block was achieved in seventeen. There was no intraoperative mortality and significant surgical complications were not encountered.

Epicardial mapping of the onset of ventricular tachycardia initiated by programmed stimulation in the canine heart with chronic infarction.

The initial beats of ventricular tachycardia (VT) induced by programmed stimulation (PS) of the heart have frequently been observed to differ in QRS configuration from the subsequent uniform QRS complexes of tachycardia. The transient nature of these initial beats has made their study difficult during epicardial mapping with conventional, hand-held recording electrodes. Twenty-four dogs were studied with PS 1-10 months after coronary ligation.

Reentry within the atrioventricular node: surgical cure with preservation of atrioventricular conduction.

Paroxysmal supraventricular tachycardia (PSVT) is commonly caused by reentry within the atrioventricular (AV) node. This arrhythmia was abolished by operative dissection of the AV junction in a patient with disabling tachycardia that was not controlled by drugs. The operation was intended to create complete AV block, but AV conduction persisted after surgery.

Reaction of the myocardium to cryosurgery: electrophysiology and arrhythmogenic potential.

The acute and chronic electrophysiological effects of a cryolesion produced in the left ventricle were studied in six dogs. All dogs had frequent ventricular premature beats (VPB) and five of six dogs had ventricular tachycardia during the first 4 days after the cryolesion; only one of the six dogs continued to have VPBs after 1 week, and this dog had identical VPBs before the creation of the cryolesion. Neither control dog had VPBs.