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  • 1
    Electronic Resource
    Electronic Resource
    Influence of Wavefront Dynamics on Transmembrane Potential Characteristics During Atrial Fibrillation (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 11 (2000), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Transmembrane Potential Characteristics. Introduction: Although computerized mapping studies have demonstrated the presence of multiple wavelets during atrial fibrillation (AF) and that action potential amplitude and duration in AF vary significantly from beat to heat, no study has correlated the single cell action potential changes with the patterns of activation during AF. Methods and Results: We studied wavefront dynamics and single cell transmembrane potential (TMP) characteristics in 12 isolated perfused canine right atria. The endocardial surface was mapped using 477 bipolar electrodes while TMP was recorded with a standard glass microelectrode from an epicardial cell. AF was induced in the presence of acetylcholine. Successful simultaneous TMP recordings and activation maps were made during six episodes of AF and for a total of 141 activations. Large variations of TMP amplitude and duration were observed frequently; 34% of them have a low amplitude (〈50% of the amplitude recorded during pacing). Low-amplitude potentials were recorded when the impaled cell was (1) in an area of random reentry (67%, n = 36); (2) within 3.2 mm of the core of organized functional reentry (22%, n = 12); (3) in the middle of two merging wavefronts (9%, n = 5); and (4) at the point of spontaneous wavebreak (2%, n = 1). Conclusion: Large variations of TMP are observed frequently during in vitro AF. Low-amplitude TMPs are associated with specific patterns of AF activation wavefronts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2000.tb00072.x
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  • 2
    Electronic Resource
    Electronic Resource
    Relation Between Cellular Repolarization Characteristics and Critical Mass for Human Ventricular Fibrillation (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 10 (1999), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Critical Mass for Human Ventricular Fibrillation. Introduction: The critical mass for human ventricular fibrillation (VF) and its electrical determinants are unclear. The goal of this study was to evaluate the relationship between repolarization characteristics and critical mass for VF in diseased human cardiac tissues. Methods and Results: Fight native hearts from transplant recipients were studied. The right ventricle was immediately excised, then perfused (n = 6) or superfused (n = 2) with Tyrode's solution at 36° C. The action potential duration (APD) restitution curve was determined by an S1-S2 method. Programmed stimulation and burst pacing were used to induce VF. In 3 of 8 tissues, 10 μM cromakalim, au ATP-sensitive potassium channel opener, was added to the perfusate and the stimulation protocol repeated. Results show that, at baseline, VF did not occur either spontaneously or during rewarming, and it could not he induced by aggressive electrical stimulation in any tissue. The mean APD at 90% depolarization (APD90) at a cycle length of 600 msec was 227 ± 49 msec, and the mean slope of the APD restitution curve was 0.22 ± 0.08. Among the six tissues perfused, five were not treated with any antiarrhythmic agent. The weight of these five heart samples averaged 111 ± 23 g (range 85 to 138). However, after cromakalim infusion, sustained VF (〉 30 min in duration) was consistently induced. As compared with baseline in the same tissues, cromakalim shortened the APD90 from 243 ± 32 msec to 55 ± 18 msec (P 〈 0.001) and increased the maximum slope of the APD restitution curve from 0.24 ± 0.11 to 1.43 ± 0.10 (P 〈 0.01). Conclusion: At baseline, the critical mass for VF in diseased human hearts in vitro is 〉 111 g. However, the critical mass for VF can vary, as it can he reduced by shortening APD and increasing the slope of the APD restitution curve.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1999.tb00280.x
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  • 3
    Electronic Resource
    Electronic Resource
    Transmembane Potential Properties of Atrial Cells at Different Sites of a Spiral Wave Reentry: Cellular Evidence for an Excitable but Nonexcited Core (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: Transmembrane action potentials (TAPs) were recorded during simultaneous mapping of a reentrant wavefront induced in canine isolated atria. The activation pattern was visualized dynamically using a high resolution electrode catheter mapping system. During functional reentry (spiral wave), cells in the core of the spiral wave remained quiescent near their resting membrane potential. Cells away from the core progressively gained TAP amplitude and duration, and at the periphery of the spiral wave the cells generated TAPs with full height and duration. During anatomical reentry, when the tip of the wavefront remained attached to the obstacle (a condition of high source-to-sink ratio), the TAP near the obstacle had normal amplitude and duration. However, when the tip of the wavefront detached from the obstacle (condition of lowered source-to-sink ratio) the TAP lost amplitude and duration. These results are consistent with the theory that the source-to-sink ratio determines the safety factor for wave propagation and wave block near the core. With decreasing source-to-sink ratio, TAP progressively decreases in amplitude and duration. In the center of the core, the cells, while excitable, remain quiescent near their resting potential. This decrease reflects a progressive decrease in the source-to-sink ratio. TAP vanishes in the core where cells remain quiescent near their resting potential. Functional and meandering reentrant wavefronts are compatible with the spiral mechanism of reentry where block at the rotating point is provided by the steep curvature of the wave tip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8159.1998.tb01182.x
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  • 4
    Electronic Resource
    Electronic Resource
    Stable Bound Pair of Spiral Waves in Rabbit Ventricles (2002)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 13 (2002), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2002.00414.x
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  • 5
    Electronic Resource
    Electronic Resource
    Radio frequency Catheter Ablation of Sustained Intraatrial Reentrant Tachycardia in a Patient With Mirror-Image Dextrocardia (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 5 (1994), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: RF Catheter Ablation in Dextrocardia. Introduction: There has been limited experience with radio frequency catheter ablation in patients with Dextrocardia. This report describes a 37-year-oid man who had corundum type Atrial septal defect, mirror-image Dextrocardia, and drug-refractory Atrial tachycardia, in whom catheter-mediated radio frequency energy successfully eliminated the tachycardia without complication. Methods and Results: On electrophysiologica study, the Atrial tachycardia could be induced and terminated by Atrial extra stimulation or rapid Atrial pacing. Mixed resetting response pattern and manifest entrainment were also demonstrated. These findings suggested that the mechanism of atrial tachycardia might be related to reentry with an excitable gap. Because of the mirrorimage dextrocardia, biplane fluoroscopy was adjusted to the right anterior oblique (RAO) 60°G and left anterior oblique (LAO) 30° positions. Inducibility of the tachycardia was completely abolished after the sixth application of radiofrequency current (30 W). It was noted that the successful electrogram preceded the onset of P wave during Atrial tachycardia by about 40 msec. Conclusion: This report presents another case in which radiofrequency catheter ablation was used in a patient with Dextrocardia. Atrial tachycardia in patients with congenital heart disease may be difficult to control pharmacologically; however, the use of radiofrequency catheter ablation could be recommended as an alternative to medication and surgery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1994.tb01203.x
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  • 6
    Electronic Resource
    Electronic Resource
    Simultaneous Biatrial Computerized Mapping During Permanent Atrial Fibrillation in Patients with Organic Heart Disease (2002)
    Oxford, UK : Blackwell Science Inc
    Journal of cardiovascular electrophysiology 13 (2002), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Activations in Permanent Atrial Fibrillation. Introduction: Activation patterns during permanent atrial fibrillation (AF) in patients with organic heart diseases are unclear. Methods and Results: We studied six patients with permanent AF and organic heart diseases undergoing surgery. The duration of AF averaged 4.9 ± 7.6 years. Computerized epicardial mappings of the right atrial (RA) free wall and the left atrial (LA) posterior wall were simultaneously performed with 224 bipolar electrodes at 3-mm spatial resolution. In the RA, large wavefronts and conduction blocks were frequently observed. The lines of block correlated with the crista terminalis and large pectinate muscles. In contrast, the LA had rapid repetitive activities originated from corners of the electrode plaque, near the four pulmonary veins (PVs). On average, 2.8 ± 1.2 sites of rapid repetitive activities were identified per patient. They activated continuously, intermittently, or alternately during AF. The mean activation cycle length in the RA (196 ± 22 msec) was significantly longer than that in the LA (179 ± 26 msec; P = 0.004). The maximum dominant frequency in the LA was higher than that in the RA (6.41 ± 1.18 Hz vs 5.66 ± 0.55 Hz; P = 0.049). The maximum dominant frequency was consistently located in areas with rapid repetitive activations near the PVs. Conclusion: During human permanent AF associated with organic heart diseases, the activation cycle length was shorter in the LA posterior wall than in the RA free wall. Rapid repetitive activities are consistently observed in the LA posterior wall, at or near the PVs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2002.00571.x
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  • 7
    Electronic Resource
    Electronic Resource
    Patterns of spiral tip motion in cardiac tissues (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 8 (1998), S. 137-148 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In support of the spiral wave theory of reentry, simulation studies and animal models have been utilized to show various patterns of spiral wave tip motion such as meandering and drifting. However, the demonstration of these or any other patterns in cardiac tissues have been limited. Whether such patterns of spiral tip motion are commonly observed in fibrillating cardiac tissues is unknown, and whether such patterns form the basis of ventricular tachycardia or fibrillation remain debatable. Using a computerized dynamic activation display, 108 episodes of atrial and ventricular tachycardia and fibrillation in isolated and intact canine cardiac tissues, as well as in vitro swine and myopathic human cardiac tissues, were analyzed for patterns of nonstationary, spiral wave tip motion. Among them, 46 episodes were from normal animal myocardium without pharmacological perturbations, 50 samples were from normal animal myocardium, either treated with drugs or had chemical ablation of the subendocardium, and 12 samples were from diseased human hearts. Among the total episodes, 11 of them had obvious nonstationary spiral tip motion with a life span of 〉2 cycles and with consecutive reentrant paths distinct from each other. Four patterns were observed: (1) meandering with an inward petal flower in 2; (2) meandering with outward petals in 5; (3) irregularly concentric in 3 (core moving about a common center); and (4) drift in 1 (linear core movement). The life span of a single nonstationary spiral wave lasted no more than 7 complete cycles with a mean of 4.6±4.3, and a median of 4.5 cycles in our samples. Conclusion: (1) Patently evident nonstationary spiral waves with long life spans were uncommon in our sample of mostly normal cardiac tissues, thus making a single meandering spiral wave an unlikely major mechanism of fibrillation in normal ventricular myocardium. (2) A tendency toward four patterns of nonstationary spiral tip motion was observed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166294
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  • 8
    Electronic Resource
    Electronic Resource
    Increased Extracellular Collagen Matrix in Myocardial Sleeves of Pulmonary Veins: An Additional Mechanism Facilitating Repetitive Rapid Activities in Chronic Pacing-Induced Sustained Atrial Fibrillation (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: Cell uncoupling due to fibrosis or increased extracellular collagen matrix (ECM) affects the formation of ectopic focal activity. Whether or not the increase of ECM also exists in the pulmonary veins (PVs) with rapid atrial pacing is unknown. We sought to test the hypothesis that in chronic atrial pacing dogs with sustained atrial fibrillation (AF), the amount of ECM was increased in both atria and the PVs. Methods and Results: We induced sustained AF in dogs by rapid atrial pacing. Computerized mapping techniques were used to map both atria and the PVs. We also used histological assessment to quantify the amount of ECM. After 118 ± 24 days of rapid atrial pacing, sustained AF was induced in 7 dogs. Repetitive rapid activities (RRAs) either continuously or intermittently arose from the PVs during sustained AF. Histological study shows that there was no fibrosis in both atrial free walls and the PVs. However, the amount of ECM was increased in these regions. The mean ECM surface area fraction at each region in the dogs with sustained AF was all significantly higher compared to the corresponding region in normal dogs. Similarly, the heterogeneity of the ECM surface area fraction at each region in the dogs with sustained AF was also all significantly higher compared to normal dogs. Conclusions: In chronic atrial pacing-induced sustained AF, structural remodeling (i.e., inhomogeneous increase of ECM) also involves the PVs. Reduced coupling of the myocytes in the PV due to histological changes may provide an additional mechanism facilitating RRAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2005.40794.x
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  • 9
    Electronic Resource
    Electronic Resource
    Relation Between the Rapid Focal Activation in the Pulmonary Vein and the Maintenance of Paroxysmal Atrial Fibrillation (2001)
    Oxford, UK : Blackwell Futura Publishing, Inc.
    Pacing and clinical electrophysiology 24 (2001), S. 0 
    Details
    ISSN: 1540-8159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: WU, T.-J., et al.: Relation Between the Rapid Focal Activation In the Pulmonary Vein and the Maintenance of Paroxysmal Atrial Fibrillation. This case report describes a patient with drug refractory paroxysmal atrial fibrillation (PAF). Rapid focal activations with multiple sharp spikes were continuously identified inside the left superior pulmonary vein (PV) during sustained AF. Among seven episodes of AF, cessation of rapid focal activations coincided with the conversion of AF to flutter (n = 4) or immediate AF termination (n = 3). Guided by sharp spikes in the PV, abrupt termination of AF occurred during radiofrequency energy application. Conclusively, rapid focal activations inside the PV are critical in AF maintenance. Cessation of these rapid focal activations underlies the mechanism by which AF converts to flutter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2001.00902.x
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  • 10
    Electronic Resource
    Electronic Resource
    Coexistence of Two Types of Ventricular Fibrillation During Acute Regional Ischemia in Rabbit Ventricle (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: We previously reported that a normal ventricle can demonstrate two types of ventricular fibrillation (VF), depending on the underlying electrophysiologic characteristics at the time of VF induction. We hypothesize that the two types of VF can coexist in acutely ischemic ventricles. Methods and Results: Optical mapping studies were performed with di-4ANEPPS in 15 Langendorff-perfused rabbit hearts. Coronary artery branches were ligated to create regional ischemia in 10 hearts. Action potential duration measured to 50% repolarization (APD50) during ischemia showed an area with uniformly shortened APD50 (zone 1), an area with normal or lengthened APD50 (zone 3), and an area in between with an APD50 gradient (zone 2). Ischemia flattened APD restitution (APDR) slope and reduced conduction velocity in zone 1, creating a condition for type II VF. APDR steepened and the conduction velocity changed little in the nonischemic zone (zone 3), creating a condition for type I VF. During induced VF, the dominant frequency in zones 2 and 3 progressively increased after ischemia onset. The dominant frequency in zone 1 (ischemic zone) first decreased and then slightly increased but typically remained less than the dominant frequency in zone 3. The number of wavebreaks increased with time in all three zones (baseline: 4.3 ± 1.5; 30 min: 11.7 ± 5.6; 60 min: 15.6 ± 11 per frame; P 〈 0.01). Conclusion: Two types of VF can coexist during acute regional ischemia. Both ischemic and nonischemic regions develop proarrhythmic changes during regional ischemia, thus contributing to increased ventricular vulnerability to VF and sudden death during acute coronary occlusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2004.04337.x
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