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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 6 (1995), S. 0 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Histology of RF Lesions. Introduction: Radiofrequency (RF) ablation of ventricular tachycardia (VT) late after myocardial infarction may be difficult due to characteristics of the infarct containing the reentry circuit. RF lesions in these infarcts in humans have not been characterized. Methods and Results: Catheter mapping and ablation of VT originating from an anterior wall infarct was performed 8 days and again 12 hours prior to death. Pacing identified a region of abnormal conduction where RF ablation terminated VT. This region contained strips of myocytes sandwiched between endocardial fibrosis and dense scar. RF lesions ranged from 2 × 2 mm to 5 × 10 mm and were up to 3 mm in depth. Acute lesions showed superficial thrombus and early coagulation necrosis without inflammation. Older lesions showed coagulation necrosis, sparse neutrophil infiltrate, minimal granulation tissue, hemorrhage, and mixed inflammatory infiltrate along the lumen without re-endothelialization. Conclusion: In this patient, RF lesions had sufficient depth but not width to interrupt the thin, but potentially broad, sheets of myocytes in the reentry circuit. In thinned areas, RF lesions can extend to the epicardium. Selecting sites with abnormal electrograms confines RF lesions to the infarct region. Inflammation and hemorrhage could conceivably cause delayed effects of RF.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: DELACRETAZ, E., et al.: Single Catheter Determination of Local Electrogram Prematurity Using Simultaneous Unipolar and Bipolar Recordings to Replace the Surface ECG as a Timing Reference. Bipolar recordings eliminate much of the far-field signal, while minimally filtered unipolar recordings contain substantial far-field signal components. These properties may allow the onset of the unipolar recording to serve as a timing reference for the bipolar recording obtained from the same electrode catheter during mapping of focal atrial or ventricular tachycardias. Mapping and RF ablation were performed in 26 patients with focal ventricular tachycardia and 14 patients with focal atrial tachycardia. At 205 mapping sites, simultaneous recordings of (1) minimally filtered unipolar electrograms (0.5–500 Hz), (2) high pass filtered unipolar electrograms (100 Hz), and (3) filtered bipolar recordings (30–500Hz) were analyzed. The interval between the onset of the minimally filtered unipolar electrogram and the first peak of the bipolar electrogram (UniOn - Bip) correlated closely with the timing of the local electrogram referenced to the surface ECG (r = 0.85, P 〈 0.001). Of 53 sites where RF ablation was performed, UniOn - BiP was shorter at successful compared to unsuccessful sites (3.8 ± 3.5 vs 9.2 ± 5.2ms, P 〈 0.001) and was 〈 15 ms at all successful sites. In conclusion, the comparison of simultaneous unipolar and bipolar electrograms from a single catheter allows assessment of the prematurity of local electrograms from a focal source without the use of the P wave or QRS onset as a timing reference.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 26 (2003), S. 0 
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Methods for determining if an ablation lesion has been created by RF current application are limited, but needed. This study sought to determine if a change in pacing threshold at the ablation site might be used to assess creation of an ablation lesion. Peak-to-peak amplitude of the bipolar electrogram (EGM) and the unipolar pacing threshold were determined before and after creation of RF lesions using irrigated tip (63 lesions in 11 patients) or conventional ablation catheters (33 lesions in 9 patients) in infarct scars for ablation of ventricular tachycardia. The threshold was measured during continuous pacing at a cycle length of 600 ms by a decrementing output current at a pulse width of 2 ms. The unipolar pacing threshold increased by 254 ± 248% (from 5.7 ± 3.5 to 15.1 ± 6.7 mA, P 〈 0.001 ) after irrigated tip ablation and by 155 ± 144% (from 5.9 ± 3.4 to 12.3 ± 5.7 mA, P 〈 0.001 ) after conventional ablation ( P 〈 0.05 for irrigated tip vs conventional). EGM amplitude decreased by 17 ± 27% (from 0.39 ± 0.32 to 0.30 ± 0.21 mV ) after irrigated tip ablation and by 16 ± 24% (from 0.48 ± 0.27 to 0.41 ± 0.20 mV ) after conventional ablation (irrigated tip vs conventional, P = NS). There was no correlation between the change in bipolar EGM amplitude and the pacing threshold. An increase in unipolar pacing threshold is a marker of lesion creation. In regions of infarction, the relative change in threshold produced by ablation is substantially larger than the change in bipolar electrogram amplitude. The greater increase in pacing threshold after irrigated tip ablation compared to conventional ablation suggests that the magnitude of change reflects lesion size. (PACE 2003; 26:1993–1996)
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 21 (1998), S. 0 
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Monomorphic ventricular tachycardias associated with regions of scar are most commonly due to reentry. Catheter based techniques have recently been described for mapping of reentry circuits. Fluoroscopic methods have obvious limitations when attempting to map large ventricular reentry circuit and localize target-sites of radiofrequency ablation. Three-dimensional right ventricular endocardial mapping was performed in a 38-year-old patient with ventricular tachycardia 28 years after surgical correction of tetralogy of Fallot by using the CARTO electroanatomical system. The map of electrogram voltage showed low amplitude electrograms over the anterior wall of the right ventricle extending into the right ventricular outflow tract, consistent with the location of the ventriculotomy scar. Recording of local activation time was combined with entrainment mapping to define the macroreentrant circuit during ventricular tachycardia. Since the activation propagated through a broad path around the right ventriculotomy scar, ablation was performed by creating a line of block, which was facilitated by tagging of the lesion sites on the endocardial activation map. Large ventricular reentry circuits can be identified and interrupted by creation of a line of block to interrupt a broad path. A practical approach to mapping combining analysis of electrogram voltage, activation sequence, and entrainment is presented.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: General modalities of analyses that have, been used for ICD studies are reviewed. Published “typical” examples are briefly described. The historical cohort method is exemplified with previously unpublished data from the Seattle Cardiac Arrest Survivor database. The AVID Study database is used to compare the results obtained from nonrandomized methodologies with randomized methodologies. Particular issues related to the use of the ICD for example, mode of death, inability to blind, selection practice, and treatment decision times make this a natural pedagogic platform.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 8 (1997), S. 0 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Outer Loop Tachycardia. Introduction: Ventricular tachycardia (VT) alter postinfarct ventricular septal defect (VSD) repair has not been well characterized. Methods and Results: A 55-year-old man developed refractory VT after inferior wall infarction and VSD repair. Entrainment demonstrated a broad reentry circuit path (outer loop) between the tricuspid annulus and VSD patch. A series of radiofrequency (RF) lesions transected this path, abolishing VI’ and producing conduction block between the inferior and superior aspects of the basal right ventricular septum. Conclusion: Some VTs have broad reentry loops requiring ablation by a series of RF lesions across the path to create a line of block. This approach is analogous to that for atrial flutter.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 9 (1998), S. 0 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 6 (1995), S. 0 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Entrainment Mapping. Many atrial tachycardias, atrial flutter, and postmyocardial infarction ventricular tachycardias are due to reentry through large “macroreentrant” circuits. These circuits can be difficult to define by catheter mapping of the activation sequence. Entrainment techniques allow the relation of a mapping site to the reentrant circuit to be assessed on a site-by-site basis during catheter mapping. Regions of abnormal conduction that are in the reentrant circuit can be distinguished from bystander sites outside the circuit. A mapping site classification to guide catheter ablation is reviewed
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Radiofrequency Ablation of Pseudo-Mahaim Fibers. Introduction: A young woman with refractory recurrent supraventricular tachycardia was referred for catheter ablation. Methods and Results: Electrophysiologic studies revealed the mechanism of tachycardia to be atrioventricular (AV) reentry, utilizing a decrementally conducting atriofascicular accessory pathway as the anterograde limb of the circuit and the normal intraventricular conducting system as the retrograde limb. Pace mapping in the right atrium during sinus rhythm suggested an atrial origin of the accessory pathway several centimeters distant from the AV node. Multiple radiofrequency lesions at the distal insertion of the accessory pathway in or near the right bundle branch failed to abolish preexcitation. In contrast, radiofrequency current applied to the ventricular side of the anterolateral tricuspid ring, adjacent to the atrial origin of the accessory pathway, was successful in abolishing preexcitation and inducible supraventricular tachycardia without affecting AV nodal conduction. Conclusion: Radiofrequency ablation can provide curative therapy for intractable supraventricular tachycardia due to decrementally-conducting atriofascicular accessory pathways. The risk of AV block in such patients as a consequence of the procedure should be quite low.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 7 (1996), S. 0 
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Autonomic Dysfunction After Catheter Ablation. Autonomic dysfunction may occur as a consequence of radiofrequency (RF) catheter ablation of a variety of supraventricular tachycardias, Effects suggestive of autonomic dysfunction that may be seen acutely during the ablation procedure include sudden profound slowing of the sinus rate or transient AV block. These abnormalities may occur during application of RF current, typically along the tricuspid or mitral annulus, at sites distant from both the sinus and AV nodes; they resolve quickly when RF current delivery is terminated. The most common long-term indication of autonomic dysfunction after ablation is inappropriate sinus tachycardia. This complication, rarely a lasting significant clinical problem, is seen after AV node modification and after ablation of accessory pathways. It usually resolves within several months. The mechanism appears to be loss of parasympathetic influence on the sinus node. Autonomic dysfunction after ablation of ventricular tachycardia bas not yet been described, but could occur as newer catheter technologies capable of producing larger lesions are perfected.
    Type of Medium: Electronic Resource
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