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Notes: Backqround: Predictors of atrioventricular nodal reentrant tachycardia (AVNRT) recurrence after radiofrequency ablation including the importance of residual slow pathway conduction are not known. The aim of this study was to report the acute and long-term results of slow pathway ablation in a large series of consecutive patients with AVNRT and to analyze the potential predictors of arrhythmia recurrence with a particular emphasis on the residual slow pathway conduction after ablation. Methods: The study included 506 consecutive patients with AVNRT (mean age 52.6 ± 16 years, 315 women) who underwent slow pathway ablation using a combined electrophysiological and anatomical approach. The end point of ablation procedure was noninducibility of the arrhythmia. The primary end point of the study was the recurrence of AVNRT. Results: Acute success was achieved in 500 patients (98.8%). After ablation, 471 patients (93%) were followed up for a mean of 903 ± 692 days. Of the 465 patients with successful ablation, 24 patients (5.2%) developed AVNRT recurrences during the follow-up. No significant differences in the cumulative rates of AVNRT recurrence were observed in groups with or without electrophysiological evidence of residual slow pathway conduction (P = 0.25, log-rank test). Multivariate analysis identified only age as an independent predictor of AVNRT recurrence (hazard ratio 0.96, 95% confidence interval 0.94–0.99, P = 0.004) with younger patients being at an increased risk for arrhythmia recurrence. Conclusions: Our study demonstrated that only younger age, but not other clinical or electrophysiological parameters including residual slow pathway conduction predicted an increased risk for AVNRT recurrence after slow pathway radiofrequency ablation.

Notes: Electromagnetic interference may result in transient or persistent suspension of antitachycardia therapies in ICDs. The incidence of such events has not been assessed so far. Patient charts were retrospectively analyzed for the occurrence of temporary suspension of antitachycardia therapies as it is stored in the Holter of St. Jude Medical or Ventritex ICDs. Follow-up data of 46 patients and 83.7-patient years were analyzed. Overall, 43 episodes of transient ICD inactivation occurred. Twenty-two of these episodes were related to intentional ICD inactivation in the emergency room or during surgery and 12 episodes were related to ICD follow-up. In nine episodes an environmental source of electromagnetic interference is presumed. None of the interactions resulted in persistent ICD inactivation or reprogramming of the devices. The risk for temporary suspension of ICD therapies unrelated to surgery, intentional magnet application in the emergency room, or routine follow-up is 11% per patient and year. Evaluation of its potential sources and the prevalence of ICD inhibition is warranted. (PACE 2004; 27:221–223)

Notes: Radiofrequency catheter ablation (RFCA) is an effective treatment for the interruption of accessory bypass tracts in WPW syndrome or the modification of the Ay-nodal conduction system in patients with A V-nodal tachycardias. However RFCA may also damage cardiac innervation. The purpose of this pilot study was to assess possible changes in sympathetic innervation after RFCA as evaluated by the cathecholamine analog carbons-11- hydoxyephedrine (HED) positron emission tomography (PET) which allows the visualisation of sympathetic nerve terminals. We investigated nine patients with supraventricular tachycardias before and two to six weeks after RFCA. Myocardial perfusion was depicted by n-I3-ammonia-PET. In addition to visual analysis, HED retention was quantified in the myocardial quadrant distal to the location of intervention; these results were compared with values in remote areas. Before RFC A, myocardial perfusion showed homogenous distribution in 8 of 9 patients. One patient showed a perfusion defect in the posterior wall. HED retention matched perfusion distribution in all patients. After RF'CA there was no significant change observed either in ammonia or in HED distribution. Quantitative HED retention data showed no significant change before versus after RFC A. Thus, HED-PET does not demonstrate any abnormalities of tracer uptake indicating integrity of sympathetic nerve terminals after radiofrequency ablation therapy.

Notes: SCHREIECK, J., et al.: 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.

Notes: Since the development of fracially coaled Iridium electrodes recordings of monophasic action potentials are possible. Intraoperative recordings of MAP from 15 pacemaker implantations were done after positioning the chronically implantabie pacemaker leads (Biotronik, Berlin, Germany) in the right ventricle by using five screw-in electrodes and ten anchor electrodes. Intraoperative recordings of MAP are possible with all implanted pacemaker leads. The recordings of typical MAP signals were always accompanied with stable electrode positions and good sensing and pacing characteristics.

Notes: SCHMITT, C., et al.: Pseudotermination of Intermittent Atrial Fibrillation by a Pacemaker Algorithm: Antitachycardia Pacing Without Capture Miscounted as Successful Termination of Fibrillation Episodes. A patient is described with intermittent AF and an implanted pacemaker which provides preventive pacing and overdrive stimulation designated to terminate atrial arrhythmias. The case highlights the possibility of false estimation of therapeutic efficacy and possible proarrhythmic effect of this therapeutic modality.

Notes: An anatomically related circumstance is reported as indication for the internal low energy Cardioversion instead of an external approach. A new single lead electrode configuration is described.

Notes: Characterization of AF in the LA. 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.

Notes: Activation of the LA During Atrial Flutter. Introduction: Activation of the left atrium (LA) in patients with isthmus-dependent right atrial flutter (AFL) has not yet been studied. The aim of this study was to analyze the activation patterns in the LA in patients with counterclockwise and clockwise AFL. Methods and Results: The study population consisted of 12 patients (10 men and 2 women; mean age 61 ± 13 years) with documented AFL and atrial fibrillation referred for ablation. The LA was mapped with a 64-electrode basket catheter inserted through a transseptal approach (10 patients) or an open foramen ovale (2 patients). In patients with counterclockwise AFL (10 episodes), the LA was activated for a mean of 133 ± 28 msec. Two endocardial breakthroughs of earliest activity on the left side of the interatrial septum, separated in time by an interval of 38 ± 15 msec, were observed in 9 episodes (90%). Two wavefronts originated from these breakthroughs, which activated the posterior and the anterior LA walls, respectively. In one patient, the entire LA was activated from the inferior breakthrough. In patients with clockwise AFL (five episodes), the LA activation time was 130 ± 13 msec. During ongoing episodes, two early electrical breakthroughs, separated in time by an interval of 41 ± 15 msec, appeared in the high anteroseptal and low posteroseptal LA regions. The superior wavefront that emerged from the high anterolateral LA region was the dominant activation pathway in 4 (80%) of 5 episodes. Conclusion: In patients with AFL, the LA is activated by two wavefronts originating from the high anterior and the low posterior regions of the interatrial septum. The sequence of activation of these interatrial connections in counterclockwise or clockwise AFL and the conductive properties of the LA conduction pathways determine the activation patterns in the LA.

Notes: 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°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.