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  • 1
    ISSN: 1572-8595
    Keywords: catheter ablation ; AV reentrant tachycardia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Atrioventricular block (AVB) during atrioventricular nodal reentrant tachycardia (AVNRT) has been well documented [1-4], although it is not a common phenomenon. The mechanism for the initiation and resolution of AVB during AVNRT have been postulated [2,4]. However, the site of AVB and its implication on the reentrant circuit in AVNRT is not clear. We illustrate two examples of AVNRT with AVB and offer further clarification on the site and mechanism of AVB.
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  • 2
    ISSN: 1572-8595
    Keywords: atrial flutter ; electrophysiology ; catheter ablation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Until recently no clinical studies had reported precise right atrium (RA) mapping when performing induction of atrial flutter (AFI). We studied the mode of tachycardia initiation in 16 patients (pts) referred for radiofrequency (RF) AFl ablation. AFl induction was performed at the beginning of the procedure (n = 10), or after previous AFl termination during RF delivery (n = 6). Detailed analysis of AFl initiation was provided by duodecapolar (Halo) and multipolar catheters positioned in the peritricuspidian region at the lateral right atrial wall (LRA), the inferior vena cavatricuspid annulus (IVC-TA) isthmus and the interatrial septum. Induction was obtained during incremental pacing (IAP) (15 pts) or programmed stimulation (1 pt) from the proximal coronary sinus (PCS). Results: Atrial flutter with counterclockwise (CCW) RA rotation was induced in all pts by PCS pacing. During PCS IAP, at long pacing cycle lengths, impulse propagated in a clockwise (CW) direction through the IVC-TA isthmus and then upward at low (L) LRA. This led to a collision at the mid LRA with another wave front propagating in a CCW direction at the septum. IAP from PCS induced a progressive delay of propagation at the IVC-TA isthmus resulting in a prolongation of the PCS-Mid Isthmus interval from 85±29 to 151±42 msec. At same pacing cycle lengths (CL), the PCS-HLRA interval was comparatively less prolonged, from 75±12 to 105±18 msec, p = 0.0007. This preferential slowing of conduction between PCS and mid isthmus, during IAP from PCS, was associated with a displacement of the zone of collision to the Low LRA. Finally a CW functional block occurred at the IVC-TA isthmus and CCW AFl was induced through a period of transient concealed entrainment. The paced CL required to initiate flutter ranged from 290 to 180 msec and the mean CL of induced atrial flutter was 254±27 msec. Conclusions: The IVC-TA isthmus has decremental properties and exhibits wenckebach phenomenon during incremental PCS pacing. Initiation of a counterclockwise flutter by PCS pacing is associated with appearance of a functional unidirectional block at the IVC-TA isthmus.
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  • 3
    ISSN: 1572-8595
    Keywords: catheter ablation ; catheter mapping ; atrial flutter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Introduction: Although recent studies have demonstrated that the endpoint of isthmus conduction block is superior to that of termination and subsequent inability to induce atrial flutter (AFl), the optimal method for determining isthmus conduction block has not been determined. Electroanatomic magnetic mapping during coronary sinus (CS) pacing may provide a reliable endpoint for AFl ablation. Methods and Results: Catheter mapping and ablation was performed in 42 patients with isthmus-dependent AFl. The patients were divided into two groups, based on procedural endpoint: Group I (28 patients) – isthmus conduction block was determined based on multipolar catheter recordings and electroanatomic mapping, and Group II (14 patients) – isthmus conduction block was determined by electroanatomic mapping during CS pacing alone. In Group I, ablation procedures were acutely successful in 25 of 28 patients (89±%). A 100±% concordance between the data presented by multipolar catheter recordings and electroanatomic mapping was noted in determining the presence or absence of isthmus conduction block. In Group II, ablation procedures were acutely successful in 13 of 14 patients, 13 (93±%). After a mean of 16.3±3.7 months follow up, there was 1 atrial flutter recurrence in the 38 patients (2.6±%) with demonstrated isthmus block at the end of the procedure. Conclusions: Electroanatomic magnetic mapping during CS pacing is comparable to the multipolar catheter mapping technique for assessing isthmus conduction block as an endpoint for AFl ablation procedures.
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  • 4
    ISSN: 1572-8595
    Keywords: linear lesions ; catheter ablation ; pulsed energy delivery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: For invasive treatment of atrial fibrillation, linear lesions induced with multipolar ablation catheters (MAC) are needed to prevent recurrence. The aim of the study was to compare the efficacy of pulsed versus continuous radiofrequency (RF)-energy delivery using MAC. Methods: In vitro tests were performed using endomyocardial preparations of fresh pig hearts in a 10-liter-bath of physiologic saline solution (37°C) at constant flow conditions (1.5[emsp4 ]l/min). The MAC were placed with a constant pressure of 20 ponds onto the endocardium. The energy (generator: Osypka HAT 200 S) was delivered either pulsed (4 electrodes simultaneously, 5[emsp4 ]ms duty-cycle) or continuously (each electrode separately). In vivo experiments were performed in 6 anesthetized pigs using fluoroscopic positioning of MAC at 40 different intracardial positions and with similar conditions as in vitro experiments. Lesion volume (LV) was calculated after measuring lesion diameter with a microcaliper. The homogeneity of the lesions (LH) was classified from 1–4; with 1 as highest homogeneity. Results: Pulsed energy delivery produced more homogeneous linear lesions in significantly less time. There was no difference in electrode temperature values (50.2±0.8 and 51.3±1.4°C) in vitro and in vivo. In the in vivo experiments, lesion depth and calculated lesion volume were less in both modes of energy delivery but pulsed energy delivery was superior regarding lesion depth and homogeneity. Conclusion: With pulsed energy delivery it is possible to create linear lesions of significantly greater homogeneity. Moreover, larger lesions are induced in less time by pulsed energy delivery in vitro and in vivo.
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  • 5
    ISSN: 1572-8595
    Keywords: slow pathway ; AV node ; catheter ablation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The presence of ectopic rhythm has been considered to be the most important marker for successful slow pathway ablation, but the details of different ectopic rhythms have not been well described. This study included 83 consecutive patients with typical AV node reentrant tachycardia who underwent slow pathway ablation. The interval between the atrial signals of the His bundle electrogram and the distal ablation catheter [A(H)-A(Ab)], and the interval between the atrial components of the distal ablation catheter and the ostium of coronary sinus catheter [A(Ab)-A(CSos)] were measured. One hundred episodes of ectopic rhythm occurred with 81 (81%) successful applications. There are two different origins and three activation sequences of ectopic rhythms, including HIS rhythm (78 applications, the earliest atrial activation in the His bundle electrogram), CSos rhythm (6 applications, the earliest atrial signal in the coronary sinus ostium electrogram) and CSos preceding HIS (CSos→HIS) rhythm (16 applications, the atrial activation sequences changing from CSos to HIS rhythm). The CSos rhythm had a shorter mean cycle length (445 ± 81 vs. 511 ± 132 vs. 579 ± 140 ms, p 〈 0.05), a shorter [A(Ab)-A(CSos)] interval (−2.5 ± 9.8 vs. 14.1 ± 11.2 vs. 12.8 ± 8.4 ms, p 〈 0.05) and a lower success rate (33% vs. 84% vs. 94% p 〈 0.05) than HIS rhythm and CSos→HIS rhythm. Otherwise, the mean cycle length of ectopic rhythm was significant shorter in successful than in failed ablation (506 ± 135 vs. 559 ± 118 ms, p = 0.04). In conclusion, we found two different origins and three activation sequences of ectopic rhythms. CSos rhythm had a lower success rate in ablation of slow pathway, thus it was a poor marker for successful ablation.
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  • 6
    ISSN: 1572-8595
    Keywords: catheter ablation ; temperature ; large electrode ; porcine heart ; IVC-TV isthmus ; atrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Radiofrequency catheter ablation of atrial flutter, atrial fibrillation or ventricular tachycardia may be favoured by large lesions. We compared lesions created in unipolar mode using 10-mm/8 F electrodes with those of 4-mm/7 F catheters. Methods: Ablations were first performed in porcine hearts in vitro (70°C, 60 s, tangential catheter tip-tissue orientation). Anaesthetized pigs were thereafter ablated with 10- or 4-mm catheters in the right atrial free wall (RAFW), inferior vena cava-tricuspid valve (IVC-TV) isthmus and left ventricle (LV). Results: In vitro, lesion length doubled and lesion volume tripled using the 10-mm catheter. Average power supply was 69 (SD12) (10-mm tip) versus 26 (SD7) W (4-mm tip). In vivo, lesion length increased by 50% and lesion volume fivefold. Charring at the lesion surface or sudden impedance rises were not observed in vivo. Histologically, coagulation necrosis and minor haemorrhages were found. One RAFW lesion (10-mm) showed a dissection approaching the epicardium. Fibrinous platelet clots or overt thromboses covered the endocardial surface in half of all lesions. Three 10-mm electrode isthmus lesions extended to the right descending posterior artery and one LV lesion to the left anterior descending artery, but there was no damage to the arterial walls. Following six ablations with the 10-mm electrode and two with the 4-mm tip, injury to the adjacent lung tissue of 0.5 to 6.0 mm depth was found (p = 0.22). Conclusion: RF ablation using 10-mm/8 F electrodes created significantly larger lesions. 10-mm electrodes appeared safe in the porcine IVC-TV isthmus and LV, but not in the RAFW.
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  • 7
    ISSN: 1572-8595
    Keywords: atrial fibrillation ; catheter ablation ; permanent pacing ; pacemakers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: The Ablate and Pace Trial (APT) prospectively assessed the effects of catheter ablation of the AV conduction system and permanent pacemaker implantation on health-related quality of life, survival, exercise capacity, and ventricular function in 156 patients with symptomatic atrial fibrillation. Methods: All patients referred for catheter ablation and permanent pacemaker implantation because of medically-refractory atrial fibrillation at 16 centers were screened for enrollment in a prospective registry. Baseline assessment prior to ablation included measurement of quality of life, including the Health Status Questionnaire, the Quality of Life Index and the Symptom Checklist: Frequency and Severity. Exercise capacity was assessed with metabolic treadmill exercise testing and ventricular function was quantitated with echocardiography. The quality of life instruments, exercise capacity, and echocardiography were repeated at 3 and 12 months after catheter ablation. Results: The APT population included 90 men and 66 women (66.1 ± 11.5 years of age) with either chronic (n = 70), recurrent (n = 31), or paroxysmal atrial fibrillation (n = 55). Structural heart disease was present in 78.2% of patients. Successful ablation of AV conduction was achieved in 155 of 156 patients (99.4%). Survival at 1 year was 85.3%, with 5 of 23 deaths being sudden cardiac deaths. Survival over the first year of follow-up was significantly lower for patients with a baseline left ventricular ejection fraction (LVEF) 〈0.45 (0.73) than for patients with a LVEF ≤0.45 (0.88, p = 0.03). The NYHA functional class improved from 2.1 at baseline to 1.8 at 3 months and 1.9 at 12 months of followup (p = 0.0001). Significant improvement in quality of life scores were noted for all 8 subscales of the Health Status Questionnaire, for the overall rating of the Quality of Life Index, the Health and Function subscales; Arrhythmia-related symptoms were markedly reduced as measured by the Symptom Checklist: Frequency and Severity scale. The mean LVEF improved from 0.50 ± 0.20 at baseline to 0.54 ± 0.20 at 3 months (p = 0.03). The LVEF 12 months after ablation was 0.52 ± 0.20, not statistically different from baseline. Individuals with reduced systolic function at baseline had the greatest improvement, from LVEF 0.31 ± 0.20 at baseline to 0.41 ± 0.20 at 3 months and 0.41 ± 0.30 at 12 months (p = 0.0001). There were no significant changes in treadmill exercise duration (10.0 ± 4.3 min at baseline and 11.6 ± 3.6 min at 12 months) or VO2max (1467 ± 681 ml O2 min baseline and 1629 ± 739 ml O2 min at 12 months). Conclusions: Catheter ablation of the AV conduction system and permanent pacemaker implantation were associated with improved quality of life and left ventricular function in this population of highly symptomatic patients with atrial fibrillation refractory to medical therapy.
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  • 8
    ISSN: 1572-8595
    Keywords: catheter ablation ; microwave energy ; pulsing arrhythmia ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Microwave energy has been proposed as a possible technique to createlarge myocardial lesions. Achieving a uniform myocardial temperaturegradient during microwave ablation may prevent excessive endocardialtemperatures while maintaining temperatures at depth. The goal of thecurrent study was to examine the ability of microwave (MW) pulsing toachieve a more uniform myocardial temperature gradient. Using an in-vitroovine endocardial model, we measured tissue temperature at 0.5-mm, 2.0-mm,and 3.5-mm depths in a circulating saline bath. MW energy was delivered at20 W at 915 MHz for 30 seconds. Pulse configurations of 1 second on–1second off, 3 seconds on-3 seconds off, and 5 seconds on-5 seconds off, with30 seconds of total MW time were compared with 30-seconds continuous.Maximum temperatures at 0.5 mm were significantly lower at 63.2 ±5.89C for the 1-second pulse compared with 83.5 ∓ 7.31C for thecontinuous-energy delivery. Pulse configurations 3 seconds on–3seconds off and 5 seconds on–5 seconds off also resulted in asignificantly lower surface temperature than continuous-energy delivery.However, temperatures at the 2.0-mm and 3.5-mm depth created by the pulsingdelivery were similar to those achieved during continuous-energy delivery.Thus, microwave pulsing achieves a lower endocardial temperature and resultsin a more uniform temperature gradient. These techniques may prevent theexcessive endocardial damage that may result in an increased risk ofthrombus formation and embolization.
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  • 9
    ISSN: 1572-8595
    Keywords: catheter ablation ; database ; relational structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A relational database was designed to facilitate patient management and storage of complex electrophysiologic data of patients undergoing radiofrequency catheter ablation. The database has to deal with multiple data entries per patient record like radiofrequency current applications and catheters. Background. Due to the complexity of catheter mapping and ablation therapy, the investigators have to handle various data types. Contradictory to a flat-file database, a relational structured database is not limited to a “single record structure”. Implementation. The designed database is built on the relational database programming environment 4th Dimension (ACI). It is implemented on an Apple Macintosh computer system. The relational structure consists of 13 data files and enables an unlimited data entry of multiple items per data field: In 1288 patients 10308 radiofrequency current applications were applied for ablation therapy and 4798 diagnostic or therapeutic catheters were used.
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  • 10
    ISSN: 1572-8595
    Keywords: catheter ablation ; cryotherapy ; isothermic period ; arrhythmia ; lesion size
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A prototype steerable 8.5F bipolar catheter fitted with a feedback thermocouple was tested in 7 anaesthetized pigs (30 kg) guided by the electrocardiogram in order to modify the AV nodal and His-Purkinje system conductive properties. Thermal energy was delivered by a pressurized N 2O tank (〉650 psi) via a cardiac cryo unit (Spembly, Hampshire, UK) into the catheter wherein gas expands resulting in a tip temperature as low as −70 ± 2°C within 10 seconds. Cryoablation under fluoroscopic and electrocardiographic guidance was applied at distinct sites in both ventricles for 60 or 120 seconds. After a follow-up period of 6 weeks, the ablation lesions found were well demarcated with small margins of hypertrophy of myocardial cells. With respect to lesion volume variability (8–207 mm 3) and geometry, a relationship between the 0°C isothermic period and cryolesion volume was found. Results of an in vitro model corroborated this relationship. Therefore, an isothermic period probably can predict the lesion size and its geometry in terms of lesion depth. This potential therapeutic mode of transcatheter cryoablation deserves further investigation.
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