Magnetic resonance guided focused ultrasound surgery of uterine fibroids--the tissue effects of GnRH agonist pre-treatment.

Objective: The purpose of this study was to determine the ablative effect of magnetic resonance guided focused ultrasound (MRgFUS) on fibroid tissue following the administration of gonadotrophin releasing hormone (GnRH) agonist.

Study Design: Fifty women with clinically symptomatic uterine fibroids were treated. Those with uterine diameter of 10 cm or greater were given 3 months pre-treatment with GnRH agonists.

Characteristics of wavefront propagation in reentrant circuits causing human ventricular tachycardia.

Background: We investigated the relationship between wavefront curvature and slowing of conduction both within and outside the diastolic pathway of circuits causing ventricular tachycardia (VT) in the infarcted human heart.

Methods And Results: Propagation was determined around the reentrant circuits of 11 VT (cycle length, 348+/-75 ms) in 8 patients undergoing high-resolution noncontact mapping. The diastolic pathway had a mean wavefront velocity of 0.

Characterization of the anatomy and conduction velocities of the human right atrial flutter circuit determined by noncontact mapping.

Objectives: This study was done to characterize human right atrial (RA) flutter (AFL) using noncontact mapping.

Background: Atrial flutter has been mapped using sequential techniques, but complex anatomy makes simultaneous global RA mapping difficult.

Methods: Noncontact mapping was used to map the RA of 13 patients with AFL (5 with previous attempts), 11 with counterclockwise and 2 with clockwise AFL.

Endocardial mapping of atrial fibrillation in the human right atrium using a non-contact catheter.

Background: Endocardial mapping of atrial fibrillation in humans is limited by its low resolution and by complexities in the arrhythmia and atrial anatomy.

Methods And Results: A catheter mounted non-contact multielectrode was deployed in the right atrium of 11 patients with atrial fibrillation and used to reconstruct 3360 electrograms, superimposed onto a computer-simulated model of the endocardium, using inverse solution mathematics. This allows construction of isopotential maps of the right atrium.

Noncontact mapping of cardiac arrhythmias.

The development of new mapping systems is beginning to overcome some of the limitations of conventional techniques by offering percutaneous deployment, simultaneous acquisitions of data, high-resolution maps, and correlation of anatomy and electrophysiology, in addition to a catheter location system. The noncontact mapping system continues to undergo development and does not completely address all requirements for an ideal mapping system. The limitations of the system include deterioration in the quality of electrogram reconstruction with increasing distance between the MEA and the endocardium, the inability of the noncontact system to identify subendocardial activation, and problems with distinguishing noise from low-amplitude diastolic electrograms.

Laparoscopic surgery in a 0.5-t interventional magnetic resonance unit.

Background: Intraoperative imaging using magnetic resonance imaging (MRI) is now possible in interventional MR (IMR) units. Magnetic resonance imaging has potential advantages over other methods used to guide surgery. These advantages include visualization of structures deep to the two-dimensional endoscopic image and clarification of surgical anatomy.

Mapping and ablation of ventricular tachycardia with the aid of a non-contact mapping system.

Objective: Treatment of ventricular tachycardia (VT) in coronary heart disease has to date been limited to palliative treatment with drugs or implantable defibrillators. The results of curative treatment with catheter ablation have proved disappointing because the complexity of the VT mechanism makes identification of the substrate using conventional mapping techniques difficult. The use of a mapping technology that may address some of these issues, and thus make possible a cure for VT with catheter ablation, is reported.

Feasibility of a noncontact catheter for endocardial mapping of human ventricular tachycardia.

Background: Catheter ablation of ventricular tachycardia (VT) is limited by difficulty in identifying suitable sites for ablation. This study assesses use of a system capable of simultaneous endocardial mapping of the human left ventricle to map and guide radiofrequency (RF) catheter ablation of VT.

Methods And Results: A catheter-mounted noncontact multielectrode array was used to reconstruct 3360 electrograms, superimposed onto a computer-simulated endocardial model.

Characteristics of sinus rhythm electrograms at sites of ablation of ventricular tachycardia relative to all other sites: a noncontact mapping study of the entire left ventricle.

Introduction: Regions of the diseased ventricle that activate abnormally during sinus rhythm (SR) may be the areas of slow and disorganized conduction that form the diastolic pathway through which reentry may occur during ventricular tachycardia (VT).

Methods And Results: We examined features of electrograms recorded during SR that might indicate a site suitable for ablation of VT using a noncontact mapping system, which enables reconstruction of > 3,000 electrograms. Preablation SR electrogram characteristics at sites of successful radiofrequency ablation (RFA) were examined in 13 patients with 53 VTs.

Simultaneous endocardial mapping in the human left ventricle using a noncontact catheter: comparison of contact and reconstructed electrograms during sinus rhythm.

Background: Catheter ablation of ventricular tachycardia is limited in part by difficulty in identifying suitable sites for ablation. A noncontact multielectrode array (MEA) has been developed that allows reconstruction of 3360 electrograms, using inverse-solution mathematics, that are superimposed onto a computer-simulated model of the endocardium. This study assesses the accuracy of timing and morphology of reconstructed unipolar electrograms compared with contact unipolar electrograms from the same endocardial site.