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  • 1
    ISSN: 1572-8595
    Keywords: Radiofrequency Energy ; PSVT ; Catheter Ablation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Temperature monitoring may be helpful for ablation of accessory pathways, however its role in ablation of atrioventricular nodal reentrant tachycardia (AVNRT) using the slow pathway approach is unclear. Therefore, the purpose of this study was to prospectively compare slow pathway ablation for AVNRT using fixed power or temperature monitoring. The study included 120 patients undergoing ablation for AVNRT. Patients were randomly assigned to receive either fixed power at 32 watts, or to temperature monitoring with a target temperature of 60°C. The primary success rate was 72% in the fixed power group and 95% in the temperature monitoring group (p=0.001). The ablation procedure duration (35±29 min vs 35±30 min; p=0.9), fluoroscopic time (32±17 vs 35±19 min; p=0.4), mean number of applications (10.2±8.1 vs 8.4±7.9; p=0.2), and coagulum formation per application (0.2% vs 0.5%; p=0.6) were statistically similar in the fixed power and temperature monitoring groups, respectively. The mean temperature (47.3±4.8°C vs 48.6±3.8°C; p〈0.01), and the temperature associated with junctional ectopy (48.2±3.8°C vs 49.3±3.6°C, p〈0.01) were less for the fixed power than the temperature monitoring group. In the temperature monitoring group, only 31% of applications achieved an electrode temperature of 60°C. During follow up of 6.6±3.6 months there were two recurrences in the fixed power group and one in the temperature monitoring group (p=1.0). In summary, power titration directed by temperature monitoring was associated with an improved primary procedural success rate. Applications of energy were associated with a temperature of approximately 50°C with both techniques, suggesting that there is a low efficiency of heating in the posterior septum.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Slow Pathway Ablation. Introduction: Successful radiofrequency ablation of an accessory pathway has been demonstrated to be associated with an electrode-tissue interface temperature of approximately 60°C or an impedance change of −5 to −10 Ω. However, the temperature and impedance changes associated with ablation of AV nodal reentrant tachycardia (AVNRT) using the slow pathway approach have not been reported. Therefore, the purpose of this study was to define the temperature and impedance changes achieved during ablation of AVNRT. Methods and Results: The study included 35 consecutive patients with AVNRT undergoing radiofrequency ablation of the slow pathway with a fixed power output of 32 W, and using a catheter with a thermistor bead embedded in the distal 4-mm electrode. The procedure was successful in each patient. The steady-state electrode-tissue interface temperature during successful applications of energy was 48.5 ± 3.3°C (range 42° to 56°C), and the steady-state temperature during ineffective applications was 46.8°± 5.5°C (P = 0.03). The mean impedance change during all applications of energy was −1.4 ± 2.8 ω, and did not differ significantly during effective and ineffective applications. Coagulum formation resulted during five applications (2.7%) in two patients (5.7%). There were no recurrences during 114 ± 21 days of follow-up. Conclusions: Successful ablation of AVNRT using fixed power output is achieved at an electrode-tissue interface temperature of approximately 48°C and is associated with a drop in impedance of 1 to 2 ω. These findings suggest that slow pathway ablation requires less heating at the electrode-tissue interface than does accessory pathway or AV junction ablation.
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  • 3
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Validation of Accessory Pathway Potentials. Four pacing maneuvers have been proposed to validate an anterograde accessory pathway potential (APP): (1) atrial pacing to induce complete block between the atrial electrogram and the APP; (2) ventricular pacing to advance the APP without altering the timing of the atrial electrogram; (3) atrial pacing to induce complete block between the APP and the ventricular electrogram; and (4) ventricular pacing to advance the ventricular electrogram without altering the timing of the APP. The purpose of this study was to assess these validation techniques by applying them to electrograms that simulated APPs but which were known to be atrial in origin. In 32 patients undergoing an electrophysiology procedure, a split atrial electrogram containing two components separated by at least 30 msec (mean 54 ± 15 msec) was recorded. Using an atrial extrastimulus tecbnique, complete block between the two components of the atrial electrogram (criterion 1) could never be induced, but complete block between the second component of the atrial electrogram and the ventricular electrogram (criterion 3) consistently was induced. Using a ventricular extrastimulus technique, the second component of the atrial electrogram consistently could be advanced by 10 to 40 msec without altering the timing of the first component (criterion 2). In addition, with ventricular pacing, the ventricular electrogram consistently was advanced without altering the timing of the two components of the atrial electrogram (criterion 4). In conclusion, among the four pacing maneuvers used to validate an anterograde APP, the only one that may be specific for an APP is the ability to induce complete block between the atrial electrogram and the APP.
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  • 4
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: The long-term efficacy of radiofrequency catheter ablation of atrial fibrillation (AF) has been based on patient-reported symptoms suggestive of AF. However, asymptomatic recurrences of AF may remain undetected. The aim of this study was to determine the prevalence of asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for AF. Methods and Results: Among 244 consecutive patients (mean age 53 ± 11 years) who underwent a pulmonary vein isolation procedure for symptomatic paroxysmal AF and who reported no symptoms of recurrent AF at ≥6 months after the procedure, 60 patients with a history of ≥1 episode of AF per week were asked to participate in this study. Preablation, these patients had experienced 19 ± 13 episodes of AF per month. The patients were provided with a patient-activated transtelephonic event recorder for 30 days, a mean of 642 ± 195 days after the ablation procedure, and were asked to record and transmit recordings on a daily basis and whenever they felt palpitations. Seven patients (12%) felt palpitations during the study, although they had not experienced symptoms previously. Each of these 7 patients had an episode of AF documented with the event monitor during symptoms. In these 7 patients, the mean number of episodes per month decreased from 19 ± 14 preablation to 3 ± 1 postablation (P 〈 0.001). Among the 53 asymptomatic patients, an episode of AF was captured in 1 (2%) patient during the study period. Conclusion: Asymptomatic recurrences of AF after an apparently successful catheter ablation procedure for symptomatic paroxysmal AF are infrequent.
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  • 5
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Bundle Branch Reentry Due to Functional His-Purkinje Block. Introduction: His-Purkinje conduction delay, manifested by bundle branch block QRS complex configuration or by HV interval prolongation, is considered an essential condition for maintenance of bundle branch reentrant tachycardia (BBRT). Methods and Results: Of 178 patients with different types of ventricular tachycardia (VT), 13 were found to have BBRT as the underlying electrophysiologic mechanism. Of these 13 patients (9 men and 4 women; mean age 64 ± 13 years), 6 had an HV interval ≤55 msec (group A), and 7 had a prolonged HV interval (〉55 msec; group B) during sinus rhythm (SR). PR interval (169 ± 32 vs 339 ± 138 msec, P = 0.01) and QRS duration (116 ± 17 vs 167 ± 29 msec, P = 0.003) during SR were significantly shorter in group A than in group B. In group A, the HV interval was significantly longer during VT than during SR (73 ± 18 vs 47 ± 7 msec, P = 0.007). There were more patients with functional His-Purkinje block (split His potentials, a jump of HV interval induced by programmed atrial stimulation or burst pacing) or phase 3 block in group A than group B (6/6 patients vs 0/7 patients, P 〈 0.001). Successful ablation of the right bundle branch was performed in all 13 patients without deteriorating AV block. Two patients died in each group, and VTs (other than BBRT) or ventricular fibrillation were documented by ICD electrogram storages in 4 patients during follow-up of 27 ± 17 months. Conclusion: A prolonged HV interval during SR is not a prerequisite for BBRT. Functional His-Purkinje system abnormalities appear to be the electrophysiologic substrate for this specific type of BBRT.
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  • 6
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Ablation of Atypical Atrial Flutter. Introduction: Mapping techniques have not been systematically evaluated with respect to atypical atrial flutter (AF) not involving the inferior vena cava isthmus. The purpose of this study was to assess prospectively the use of concealed entrainment (CE) in mapping of AF and to assess the clinical benefit of ablation of clinically relevant atypical AF. Methods and Results: In seven consecutive patients without prior cardiac surgery presenting with atypical AF, mapping was performed in the right and, if necessary, left atrium. At sites with CE, radiofrequency energy was delivered. In a posthoc analysis, the endocardial activation time, stimulus-flutter wave (F) interval, presence of split potentials and diastolic potentials, and postpacing Interval were assessed, and effective sites were compared to ineffective sites. A total of 22 forms of atypical AE either could be induced or were present at the time of the study. Eleven of the 13 targeted atypical AFs (85%) were successfully ablated. The positive predictive value of CE increased from 45% to 75% in the presence of matching electrogram-F and stimulus-F intervals or if flutter terminated during entrainment pacing, and to 88% in the presence of split atrial electrograms or diastolic potentials. During short-term clinical follow-up, none of the patients had recurrence of the ablated AE. However, the majority of patients required either medication for atrial fibrillation or repeated interventions for new forms of AF. Conclusion: Mapping and ablation of atypical AF is feasible if sites with CE can be identified. However, the clinical benefit of successful ablations in patients with atypical flutter appears to be limited.
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  • 7
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Left Anterior Fascicular Tachycardia. Introduction: A 45-year-old man with idiopathic ventricular tachycardia (VT) having a right bundle branch block configuration with right-axis deviation underwent au electrophysiologic test. Methods and Results: Mapping demonstrated a site on the auterobasal wall of the left ventricle where there was an excellent pace map and an endocardial activation time of -20 msec, hut radiofrequency catheter ablation at this site was unsuccessful. At a nearby site, a presumed Purkinje potential preceded the QRS complex by 30 msec during VT and sinus rhythm, and catheter ablation was effective despite a poor pace map and an endocardial ventricular activation time of zero. Conclusion: Idiopathic VT with a right bundle branch configuration and right-axis deviation may originate in the area of the left anterior fascicle. A potential presumed to represent a Purkinje potential may he more helpful than endocardial ventricular activation mapping or pace mapping in guiding ablation of this type of VT.
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  • 8
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Lower Turnaround Point of AVNRT. Introduction: Recent observations suggest that the circuit of AV nodal reentrant tachycardia (AVNRT) may extend down to the His bundle. The purpose of this study was to develop a quantitative model indicating the location of the lower turnaround point in AVNRT. Methods and Results: Slow pathway modification was performed in 70 patients with typical AVNRT. During sinus rhythm, ventricular pacing was performed with the AVNRT cycle length. During AVNRT, the HinitAinit interval was measured from initial His to the initial atrial deflection recorded in the His-bundle lead. During ventricular pacing, the HendAinit interval was measured from end of the His to the beginning of the atrial deflection. It was hypothesized that x reflects conduction time from the lower turnaround point to Ainit, whereas y reflects conduction time from the lower turnaround point to Hinit. Anterograde conduction during AVNRT and retrograde conduction during ventricular pacing were assumed to be identical if there was 1:1 retrograde conduction at the AVNRT cycle length. The following formulas descrihe the relation of the measured parameters: x - y = HinitAinit; and x + y =HendAinit. Resolving hoth formulas yields the unknown x and y: y = (HendAinit+ HinitAinit)/2. = (HendAinit + HinitAinit)/2. These criteria were present in 52 of 70 patients. The mean cycle length of AVNRT was 355 ± 42 msec, mean HinitAinit was 54 ± 27 msec, and mean HendAinit was 60 ± 29 msec. Accordingly, in 20 of 52 patients, the lower turnaround point was located within the His bundle (y = - 15.4 ± 16.1 msec), in 3 of 52 it was in the nodal-His junctional area (y = 0), and in 29 of 52 it was above the His bundle (y =+12.7 ± 10.3 msec). The HinitAinit interval was significantly longer (66 ± 32 msec vs 47 ± 20 msec; P = 0.02) and the HendAinit interval was significantly shorter (45 ± 30 msec vs 69 ± 24 msec; P = 0.004) when the first group was compared with the others. Conclusion: In about 1 of 3 of patients with typical AVNRT, the lower turnaround point of the circuit is within the His bundle; in more than half of the patients it is above the His bundle. These data do not support the concept that all AVNRTs have an intranodal circuit, but are in accordance with the finding of longitudinal dissociation of the His bundle.
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  • 9
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
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  • 10
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Objective: We sought to better define the electrophysiologic mechanism of atrial flutter in patients after heart transplantation. Background: Atrial flutter is a recognized problem in the postcardiac transplant population. The electrophysiologic basis of atrial flutter in this patient population is not completely understood. Methods: Six patients with cardiac allografts and symptoms related to recurrent atrial flutter underwent diagnostic electrophysiologic study with electroanatomic mapping and radiofrequency catheter ablation. Comparison was made with a control nontransplant population of 11 patients with typical counterclockwise right atrial flutter. Results: In each case, mapping showed typical counterclockwise activation of the donor-derived portion of the right atrium, with concealed entrainment shown upon pacing in the cavotricuspid isthmus (CTI). The anastomotic suture line of the atrio-atrial anastomosis formed the posterior barrier of the reentrant circuit. Ablation of the electrically active, donor-derived portion of the CTI was sufficient to terminate atrial flutter and render it noninducible. Comparison with the control population showed that the electrically active portion of the CTI was significantly shorter in patients with transplant-associated flutter and that ablation was accomplished with the same or fewer radiofrequency lesions. Conclusions: Atrial flutter in cardiac transplant recipients is a form of typical counterclockwise, isthmus-dependent flutter in which the atrio-atrial anastomotic suture line forms the posterior barrier of the reentrant circuit. Ablation in the donor-derived portion of the CTI is sufficient to create bidirectional conduction block and eliminate this arrhythmia. Ablation or surgical division of the donor CTI at the time of transplantation could prevent this arrhythmia.
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