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  • 1
    Electronic Resource
    Electronic Resource
    Localizing and Quantifying Ablation Lesions in the Left Ventricle by Myocardial Contrast Echocardiography (2004)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 15 (2004), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: The inability to determine the extent and intramural depth of ablation lesions can hamper the success of catheter ablation. The study tested the feasibility of differentiating radiofrequency ablation lesions from normal myocardium and quantifying their dimensions by myocardial contrast echocardiography (MCE). Methods and Results: In 11 normal dogs, we created 14 focal and 4 linear lesions at different left ventricular sites. MCE was performed both before and after ablation by using an intracardiac echocardiography catheter (9 MHz) and infusing contrast microbubbles through the left coronary artery. We initially used two-dimensional MCE to image focal lesions and subsequently three-dimensional MCE to image linear lesions. An independent observer examined the lesion pathology. We found that intracardiac echocardiography alone could not delineate lesion dimensions. However, after ablation, MCE localized the lesions as well-defined, low-contrast areas within the normally opacified myocardium. Lesion dimensions by MCE immediately after ablation and 30 minutes later were similar. In 12 focal lesions, the average maximum depth (5.55 ± 1.38 mm) and average maximum diameter (10.38 ± 2.09 mm) by MCE were in excellent agreement with the pathologic depth (5.20 ± 1.45 mm) and diameter (10.61 ± 1.67 mm). Two focal lesions could not be detected by MCE and later were found to be superficial. Three-dimensional MCE correctly reconstructed the extent and shape of linear lesions compared to pathology (length: 18.7 ± 5.7 vs 18.5 ± 5.6 mm; maximum longitudinal cross-sectional area: 81.2 ± 9.6 vs 76.0 ± 10.3 mm2). Conclusion: MCE accurately localized and quantified radiofrequency ablation lesions in the normal left ventricle. This new application of MCE may advance ablation for managing ventricular arrhythmias that involve intramural or epicardial regions by providing instantaneous anatomic feedback on the effects of ablation during catheterization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2004.04087.x
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  • 2
    Electronic Resource
    Electronic Resource
    Electrophysiological Imaging of the Right Atrium Using a Noncontact Multielectrode Cavitary Probe: Study of Normal and Abnormal Rhythms (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Pacing and clinical electrophysiology 21 (1998), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Cavitary electmgrams previously were measured from multiple directions simultaneously in the canine left ventricle with the use of noncontact multielectrode probes. The objective of the present study was to measure cavitary electrograms in the canine right atrium (RA) and describe the corresponding global activation sequences during normal and abnormal atrial rhythms. A 64-electrode custom probe was inserted into the RA of six dogs. Probe position and orientation were guided by fluoroscopy. Probe unipolar electrograms were acquired simultaneously during sinus rhythm, RA pacing, and ventricular pacing, Vagally mediated atrial fibrillation (AF) was induced in four dogs. Probe electrograms were acquired during AF induced at baseline and after intravenous infusion of ibutilide (0.075 mg/kg followed by 0.075 mg/kg infusion over 10 minutes). Isochrone maps were derived from noncontact probe electrograms and were displayed on a beat-by-beat basis during normal and paced rhythms. During AF, maps were displayed for 10 consecutive 100-ms windows. Isochrone maps of normal and paced beats revealed regions of early activation that were consistent with sites of wavefront initiation. During AF, multiple varying activation wavefronts were observed. At baseline, AF cycle length was 110 ± 15 ms and the number of wavefronts was 1.72 ± 0.25 per 100-ms window. After ibutilide, AF cycle increased to 182 ± 36 ms (P = 0.018) and the number of wavefronts decreased to 0.82 ± 0.14 per 100-ms window (P = 0.009). In conclusion, global electrophysiological imaging with a noncontact multielectrode probe delineates RA anatomy. Furthermore, images of AF activation depict multiple wandering wavefronts. Ibutilide reduces the number of these wavefronts and organizes AF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1998.tb01208.x
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  • 3
    Electronic Resource
    Electronic Resource
    Noncontact Endocardial Mapping: Reconstruction of Electrograms and Isochrones From Intracavitary Probe Potentials (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 8 (1997), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Noncontact Endocardial Mapping. Introduction: Mapping endocardial activation and repolarization processes is critical to the study of arrhythmias and selection of therapeutic procedures. Previously, we developed methodology for reconstructing endocardial potentials from potentials measured with a noncontact, intracavitary probe. This study further develops and evaluates the ability of the approach to provide detailed information on the spatiotemporal characteristics of the activation process. Specifically, we reconstructed endocardial electrograms and isochrones throughout the activation process over the entire endocardium during a single beat. Methods and Results: Cavity potentials were measured with a 65-electrode probe placed inside an isolated canine left ventricle. Endocardial potentials were measured simultaneously using 52 electrodes. Potentials were acquired during subendocardial pacing from different locations. Computed electrograms at various sites closely resemble the measured electrograms (correlation coefficient 〉 0.9 at 60% of the electrodes). Computed isochrones locate subendocardial pacing sites with 10-mm accuracy. Two pacing sites, 17 mm apart, were resolved. Critical regions, such as areas of isochrone crowding, were accurately reconstructed. Conclusions: Results indicate the applicability of the approach to mapping the cardiac excitation process on a beat-by-beat basis without occluding the ventricle. The ability of locating electrical events (e.g., single or multiple initiation sites) is demonstrated. Importantly, the method is shown to be capable of reconstructing electrograms over the entire endocardium and determining nonuniformities of activation spread (e.g., areas of slow conduction). These capabilities are important to clinical application in the electrophysiology laboratory and experimental studies of arrhythmias in the intact animal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1997.tb00807.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of Pulmonary Vein Ablation on Regional Atrial Vagal Innervation and Vulnerability to Atrial Fibrillation in Dogs (2005)
    350 Main Street , Malden , MA 02148-5018 , USA , and 9600 Garsington Road , Oxford OX4 2DQ , UK . : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 16 (2005), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Introduction: Pulmonary vein (PV) isolation has proven to be an effective therapy for atrial fibrillation (AF). However, clinical evidence suggests that suppression of AF after PV isolation could not be fully attributed to the interruption of electrical conduction in and out of the PVs. Furthermore, little is known regarding the effects of ablation around the PVs on the atrial electrophysiological properties. We aimed to study the changes in atrial response to vagal stimulation (VS) after PV ablation (PVA). Methods: We studied 11 adult mongrel dogs under general anesthesia. Bilateral cervical sympathovagal trunks were decentralized. Propranolol was given to block sympathetic effects. Multipolar catheters were placed into right atrial appendage (RAA), distal and proximal coronary sinus (CSD, CSP), and left atrial free wall (LAFW). PVA was performed via trans-septal approach. Atrial effective refractory period (AERP) and vulnerability window (VW) of AF were measured with and without VS before and after ablation to isolate the PVs. Results: After ablation, AERP shortening in response to VS significantly decreased in the left atrium (43.64 ± 21.57 vs 11.82 ± 9.82 msec, P 〈 0.001 at LAFW; 50.91 ± 26.25 vs 11.82 ± 14.01 msec, P 〈 0.001 at CSP; 50 ± 31.94 vs 17.27 ± 20.54 msec, P 〈 0.005 at CSD), while the response to VS did not change significantly at RAA (58.18 ± 28.22 vs 50.91 ± 22.12 msec, P = 0.245). After ablation, atrial fibrillation VW during VS narrowed (20.63 ± 11.48 vs 5.63 ± 8.63 msec, P 〈 0.03 at LAFW; 26.25 ± 12.46 vs 5.00 ± 9.64 msec, P = 0.001 at CSP; 28.75 ± 18.47 vs 6.88 ± 7.53 msec, P 〈 0.02 at CSD, and 33.75 ± 24.5 vs 16.25 ± 9.91 msec, P = 0.03 at RAA). Conclusions: Ablation around the PV ostia diminishes left atrial response to VS and decreases the atrial VW. The attenuated vagal response after ablation may contribute to the suppression of AF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2005.50048.x
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  • 5
    Electronic Resource
    Electronic Resource
    Pharmacologic Enhancement of Atrial Electrical Defibrillation Efficacy: Role of Ibutilide (1997)
    Springer
    Journal of interventional cardiac electrophysiology 1 (1997), S. 291-298 
    Details
    ISSN: 1572-8595
    Keywords: cycle length ; defibrillation threshold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The study was designed to identify the influence of ibutilide on activation during atrial fibrillation (AF) and determine its role in enhancing the efficacy of electrical conversion of AF. Vagally-mediated acute AF was induced in 12 anesthetized dogs. In 5 dogs, a cross-shaped epicardial patch containing 16 recording electrodes was placed on the right atrium. In 7 dogs, defibrillation patch electrodes overlying both atria were used to deliver biphasic shocks (50% tilt; 90 °F). Measurements were made at baseline and following ibutilide (0.075 mg/kg bolus followed by 0.075 mg/kg infusion over 10 minutes). Right atrial multisite electrogram recordings revealed significant prolongation in AF cycle length at all sites following ibutilide. In all dogs, AF cycle length increased with ibutilide from 90±23 to 130±49 ms (p 〈 0.005). Whereas, atrial defibrillation threshold decreased from 0.83±0.5 to 0.53±0.29 J (p =0.020). In conclusion, ibutilide prolongs cycle length of canine vagally-mediated acute AF. Furthermore, ibutilide facilitates electrical conversion of AF by lowering energy requirement. Thus, controlled drug infusion in conjunction with electrical defibrillation may be useful for managing AF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009781026210
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  • 6
    Electronic Resource
    Electronic Resource
    Activation Effects of Single-Site and Dual-Site Right Atrial Pacing in Canine (2000)
    Springer
    Journal of interventional cardiac electrophysiology 4 (2000), S. 501-509 
    Details
    ISSN: 1572-8595
    Keywords: atrium ; mapping ; pacing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Medical therapy for managing atrial fibrillation remains less than satisfactory. Electrical therapy such as right atrial (RA) pacing was shown to reduce rate of recurrence of atrial fibrillation, while evidently dual-site pacing was more effective than single-site pacing. However, similarities and/or differences in the electrophysiological consequences of single-site and dual-site RA pacing are unclear. Our objective was to simultaneously map RA and left atrial (LA) activation patterns and compare intra-atrial and interatrial activation properties during single-site and dual-site RA pacing in the normal canine heart. Basket-shaped catheters carrying 64 electrodes were deployed under the guidance of fluoroscopy and echocardiography into both the RA and LA of 7 dogs. Basket unipolar electrograms were simultaneously recorded while pacing at high lateral RA (HRA) alone, at inferior RA septum (RAS) alone, and at both sites simultaneously. We found that pacing at HRA alone resulted in the longest interatrial conduction time (47±6[emsp4 ]ms). Pacing at RAS alone significantly shortened interatrial conduction time (29±5[emsp4 ]ms) and completely activated both the RA and LA simultaneously (70±6[emsp4 ]ms and 69±8[emsp4 ]ms, respectively). Dual-site pacing at HRA and RAS significantly abbreviated RA complete activation time (52±7[emsp4 ]ms), but did not alter interatrial conduction time or LA activation pattern compared to pacing at RAS alone. In conclusion, single-site pacing at RAS shortened interatrial conduction time compared to HRA and completely activated both atria simultaneously in canines with normal atria. In addition to shortening interatrial conduction time, dual-site pacing at HRA and RAS abbreviated RA complete activation time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009812631562
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