Biomedical subjects

Bernhard Zrenner

Publications and source records attributed to Bernhard Zrenner.

40 records · Page 3Linked to original sources

PubMed2002

Radiofrequency ablation of cardiac arrhythmias using a three-dimensional real-time position management and mapping system.

A recently developed three-dimensional real-time position management system (RPM) uses an ultrasound ranging technique that enables multiple distance measurements between two reference catheters and a mapping catheter each equipped with ultrasound transducers. In addition to three-dimensional representation of the catheters and ablation sites it displays real-time movements of catheters (including the tip and shaft). A recently released version of the system enables additional geometry reconstruction of the heart chamber and activation mapping. This study included 21 patients (mean age 59 +/- 14.5 years) referred for radiofrequency catheter ablation of various arrhythmias. Geometry was reconstructed by tracing the endocardial contour of the respective heart chambers. Global and local color coded activation maps were constructed to confirm the nature of arrhythmia and to guide ablation. Spontaneous or induced arrhythmias were typical atrial flutter (n = 8), atypical atrial flutter (n = 3), atrioventricular nodal reentrant tachycardia (n = 3), atrial tachycardia (n = 2), atrial fibrillation (n = 2), ventricular tachycardia (n = 2), and Wolff-Parkinson-White syndrome (n = 1). Geometry reconstruction and mapping of arrhythmias were possible in 20 of 21 patients. RPM-guided radiofrequency ablation was successful in 19 (95%) of 20 patients. Due to difficulties in steering the RPM mapping/ablation catheter, in 6 (28%) successfully mapped patients, radiofrequency ablation was performed using another catheter. In one patient, the RPM-guided map was inconclusive and in another patient, ablation failed due to multiple reentrant circuits. No complications were observed. In conclusion, the new RPM system enables geometry reconstruction and three-dimensional positioning of the ablation catheters, reconstruction of the activation maps, marking of anatomic structures and reproducible tracking of multiple ablation sites. The system could be used to guide radiofrequency ablation of atrial and ventricular arrhythmias.

Arrhythmias, Cardiac↗

PubMed2002

Characterization of paroxysmal and persistent atrial fibrillation in the human left atrium during initiation and sustained episodes.

INTRODUCTION: Atrial fibrillation (AF) in the left atrium (LA) is poorly defined in terms of regional differences in the degree of organization, characteristics of paroxysmal and persistent variants, and electrophysiologic events that develop at the onset of episodes. METHODS AND RESULTS: The study population consisted of 21 patients (15 men and 6 women; mean age 58+/-9.4 years) with paroxysmal (10 patients) or persistent (11 patients) AF. Mapping of the LA during sustained episodes and the onset of AF was performed with a 64-electrode basket catheter. At the onset of AF, repetitive beats starting with atrial premature complexes and ending with generation of the earliest fibrillatory activity were defined as intermediary rhythm. Patients with paroxysmal AF had longer AF cycle lengths and more pronounced regional differences than patients with persistent AF. In total, AF cycle lengths in the LA in patients with persistent AF were 20% shorter than in patients with paroxysmal AF. Initiation of AF was preceded by an intermediary rhythm of 5.5+/-2.5 cycles (6.3+/-2.7 cycles in paroxysmal AF vs 4.2+/-1.0 cycles in persistent AF; P = 0.026). At the onset of AF, the earliest generators of fibrillatory activity were located more frequently in the posterior wall of the LA. CONCLUSION: AF in the LA displays substantial regional differences in terms of AF cycle lengths and degree of organization. Patients with persistent AF have shorter cycle lengths and a higher degree of disorganized activity than patients with paroxysmal AF. Intermediary rhythms play an important role in initiation of AF via activation of generator regions in the LA.

Adult↗

PubMed2002

Prospective randomized comparison of closed cooled-tip versus 8-mm-tip catheters for radiofrequency ablation of typical atrial flutter.

INTRODUCTION: Cooled-tip and 8-mm-tip catheters have been found to be more effective than conventional 4-mm-tip catheters for radiofrequency (RF) ablation of common atrial flutter. The aim of this study was to compare the efficacy and safety of cooled-tip and 8-mm-tip catheters for flutter ablation in a randomized, prospective study. METHODS AND RESULTS: In 100 consecutive patients referred for ablation of common atrial flutter, cavotricuspid ablation was performed with a closed cooled-tip catheter (n = 50) or an 8-mm-tip ablation catheter (n = 50). RF current was applied for 60 to 120 seconds at powers of 40 to 50 W with the closed cooled-tip catheter and in a temperature-controlled mode (65 degrees C/70 W) with the 8-mm-tip catheter. The endpoint was achievement of a bidirectional isthmus conduction block. Cross-over was performed after 15 unsuccessful RF applications for each of the catheters. Complete bidirectional isthmus block was achieved in 99% of patients. Cross-over was performed in 11 patients after primary use of the cooled-tip catheter and in 9 patients after primary ablation with the 8-mm-tip catheter. No significant differences were found in the procedure parameters, such as overall RF applications (12.4 +/- 11.3 vs 12.9 +/- 8.6), ablation duration (42 +/- 43 min vs 39 +/- 27 min), and fluoroscopy time (17.0 +/- 18.7 min vs 15.7 +/- 10.7 min). In a mean follow-up of 8.3 months, 1 patient in the cooled-tip group and 3 patients in the 8-mm-tip group had recurrence of common atrial flutter. CONCLUSION: Use of the closed cooled-tip ablation catheter and the 8-mm-tip catheter have equal and high efficacy for RF ablation of common atrial flutter.

Aged↗

PubMed2002

Direct and indirect catheter-to-catheter carbonization caused by high power radiofrequency delivery via a large tip ablation electrode.

We report two cases of directly and indirectly induced catheter carbonizations by radiofrequency application via a large tip ablation catheter. We assume that during a large tip high power delivery of more than 50 watts, an adjacent, smaller-sized, low resistance electrode produces a local increase in the intensity of the current field that is sufficient to elevate the tissue temperature above 100 degrees C. Due to the potential risk of embolism, this may have an impact on ablation procedures in the left atrium and ventricle using similar mapping configurations.

Adult↗