bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Ventricular Fibrillation Duration and a Preceding Unsuccessful Shock on the Probability of Defibrillation Success Using Biphasic Waveforms in Pigs
Authors: WINDECKER STEPHAN , KAY G. NEAL , H BRUCE , WALCOTT GREGORY P. , SMITH WILLIAM M. , IDEKER RAYMOND E. 
Published: April 2007

Influence of VF Duration on Defibrillation Efficacy. introduction: While the defibrillation threshold has been reported to increase with ventricular fibrillation (VF) duration for monophasic waveforms, the effect of VF duration for biphasic waveforms is unknown. Methods and Results: The ED 50 requirements (the 50% probability of defibrillation success) for an endocardial lead system, which included a subcutaneous array, were determined by logistic regression using a recursive up‐down algorithm for a biphasic waveform ((6/6 msec). The study was performed in two parts, each with eight pigs. In part 1, ED 50 was compared for shocks delivered after 10 seconds of VF and for shocks delivered after 20 seconds of VF following a failed first shock at 10 seconds. Energy at ED 50 decreased from 6.5 ± 0.9, J for shocks delivered after 10 seconds of VF to 4.9 ± 0.8, J (P < 0.01) for shocks delivered after 20 seconds. To determine if improved second shock efficacy was a result of preconditioning by the failed first shock or a function of VF duration, part 2 of the study compared defibrillation efficacy between shocks delivered after 10 seconds of VF with shocks delivered after 20 seconds of VF with and without a failed first shock at 10 seconds. Mean energy at ED 50 decreased from 10.1 ± 2.4, J for shocks delivered after 10 seconds of VF to 7.9 ± 2.4 J (P < 0.01) and 7.5 ± 3.2 J (P < 0.01) for shocks delivered after 20 seconds of VF with and without a failed first shock, respectively. The mean energy at KD 50 for shocks delivered after 20 seconds of VK with and without a failed first shock was not significantly different (P = 0.53). A strong linear correlation for energy at ED 50 was found between shocks delivered after 10 seconds of VF and shocks delivered after 20 seconds of VF following a failed first shock (r = 0.95, P < 0.01). Conclusion: (1) As opposed to monophasic shocks, ED 50 is significantly lower for biphasic shocks delivered after 20 seconds of VF compared with shocks delivered after 10 seconds of VF in pigs. (2) An unsuccessful biphasic shock in pigs does not affect the defibrillation efficacy for a subsequent shock. (3) ED 50 for a biphasic shock delivered after 20 seconds of VK is linearly related to ED 50 for a shock delivered after 10 seconds of VK.
Effects of Slow Pathway Ablation on Fast Pathway Function in Patients with Atrioventricular Nodal Reentrant Tachycardia
Authors: SHEN WIN‐KUANG , MUNGER THOMAS M. , STANTON MARSHALL S. , OSBORN MICHAEL J. , HAMMILL STEPHEN C. , PACKER DOUGLAS L. 
Published: April 2007

Effects of Slow Pathway Ablation. Introduction: This study investigated whether fast pathway conduction properties are altered by slow pathway ablation in patients with AV nodal reentrant tacbycardia.Methods and Results: Forty consecutive patients who underwent successful ablation of the slow pathway were prospective subjects for the study. Isoproterenol was used to enhance conduction and to differentiate interactive mechanisms. Potential electrotonic interactions were assessed by comparing patients with and those without residual dual AV node pbysiology after slow pathway ablation. Paired and unpaired t‐tests were used when appropriate. P < 0.05 was considered statistically significant. In the entire study population, heart rates were not significantly different before and after slow pathway ablation (RR = 770 ± 114 msec before and 745 ± 99 msec after, P = 0.07). Anterograde fast pathway conduction properties were unchanged after slow pathway ablation (effective refractory period, 348 ± 84 msec before and 336 ± 86 msec after, P = 0.13; shortest 1:1 conduction, 410 ± 93 msec before and 400 ± 82 msec after, P = 0.39). Retrograde fast pathway characteristics also were similar before and after ablation. Neither anterograde nor retrograde last pathway conduction properties during isoproterenol infusion were changed by slow pathway ablation. When the study population was further divided into patients with (n= 13) or without (n = 27) residual dual AV node pbysiology, no significant change was detected in fast pathway function in either group after slow patbway ablation.Conclusions: Fast pathway conduction characteristics were not affected by slow pathway ablation. In patients with AV nodal reentrant tachycardia, observations suggest that fast and slow pathways are functionally distinct.
Responses to Norepinephrine of Normal and “Ischemic” Canine Purkinje Fibers are Consistent with Activation of Different α1‐Receptor Subtypes
Authors: ANYUKHOVSKY EVGENY P. , GUO SHI‐DUO , DANILO PETER , ROSEN MICHAEL R. 
Published: April 2007

α1‐Receptor Subtype Stimulation of Purkinje Fibers. Introduction: Previously we found that WB4101 (WB) 10‐7 M competitively blocks three α1‐adrenergic receptor‐effector responses: the increase in normal automaticity occurring in Purkinje fibers (PF) at high membrane potentials: the increase in abnormal automaticity occurring in PF at depolarized membrane potentials; and the prolongation of PF action potential duration. These observations are consistent with two different hypotheses: (1) WB blocks a single α1‐receptor subtype, which subserves different effector pathways; and (2) WB blocks different receptor subtypes, eacb of which subserves an independent patbway. The aim of this study was to test both hypotheses.Methods and Results: We used standard microelectrode techniques to study the concentration‐dependent actions of three α1‐adrenoreceptor blockers (WB (α1A≫α1D], 5‐methylurapidil [5‐MU] [α1A, ≫α1D], and UK52,046 [nonselective]) on norepinephrine (NK) effects in normal PF and in PF depolarized with a simulated ischemic solution ([K+]o= 10 mM; pO2 < 20 mmHg; pH 6.8; maximum diastolic potential ‐60 ± 1 mV). In normally polarized PF, concentration‐dependent actions of all blockers on both the positive cbronotropic response and the prolongation of action potential duration completely coincide. In contrast, the response to NE of abnormal automaticity in “ischemic” PF differs from normals: there is a bigh sensitivity to WB and 5‐MU and no response to UK52,046.Conclusions: (1) A single receptor subtype appears responsible for botb the α1‐induced prolongation of repolarization and the positive chronotropic effect in normal PF. (2) Two different receptor subtypes may be responsible for the α1‐induced effects on automaticity in normal and ischemic fibers. It is likely that the latter one is α1A, and that consideration of antiarrhythmic therapy with α1‐adrenergic blockers should focus on this subtype as a potential target.
Early Afterdepolarizations Produced by d,1‐Sotalol and Clofilium
Authors: PATTERSON EUGENE , SCHERLAG BENJAMIN J. , LAZZARA RALPH 
Published: April 2007

EAD Formation by Class III Drugs. Introduction: The roles for L‐type calcium current and Na‐Ca exchange in early afterdepolarizations (EADs) attending d, l‐sotalol and clofilium were examined in canine Purkinje fibers and in enzymatically dispersed myocytes from canine subepicardium.Methods and Results: Spontaneous EADs were compared to EAD formation potentiated by stimulation of Na‐Ca exchange and facilitation of ICa‐L (Bay K8644). Bay K8644 (10‐8 M) and stimulation of Na‐Ca exchange potentiated bradycardia‐dependent EADs. Stimulation of Na‐Ca exchange in Pnrkinje fibers pretreated with d, l‐sotalol (10‐5 M) and clofilium (10‐7 M) induced EADs at takeoff potentials negative (‐63 ± 4 and ‐62 ± 4 mV, respectively) to EADs potentiated by Bay K8644 (10‐8 M) (‐33 ± 2 and ‐34 ± 2 mV, respectively, P < 0.05), or EADs induced by Bay K8644 alone (10‐6 M) (‐31 ± 5 mV). In myocytes, Bay K8644 (10‐8 M) potentiated EADs in d, l‐sotalol‐ (10‐6 to 10‐4M) or clofilium‐treated (10‐9 to 10‐7 M) cells at reduced potentials (‐10 ± 3 and ‐10 ± 4 mV, respectively) compared to EADs elicited by clofilium or d, l‐sotalol alone (‐25 ± 3 and ‐24 ± 3 mV, respectively), or stimulation of Na‐Ca exchange in the presence of d, l‐sotalol or clofilium (‐26 ± 4 and ‐26 ± 4 mV, respectively). Spontaneous EADs or EADs elicited by stimulation of Na‐Ca exchange coincident with drug treatment were suppressed by increasing Cao2+ but were not suppressed by nifedipine (10‐7 M).Conclusion: EADs elicited by d, l‐sotalol and clolllium in canine Purkinje tissue and epicardial myocytes are dependent upon Na‐Ca excbange rather than ICa‐L“window current.”
Reproducibility of the Adenosine‐5′‐Triphosphate Test in Vasovagal Syndrome
Authors: FLAMMANG DANIEL , CHASSING ANNICK , DONAL ERWAN , HAMANI DJAMEL , ERICKSON MARK , McCARVILLE SALLY 
Published: April 2007

Vasovagal Syndrome: ATP Test Reproducibility. Introduction: Adenosine‐5′‐triphosphate (ATP) provokes negative chronotropic and dromotropic vagal effects. In vasovagal syndrome, ATP test (20‐mg IV bolus infusion) represents a promising technique for identifying patients at risk of severe cardioinhibitory response of vagal origin. The electrocardiographic and related symptom reproducibility of this descriptive test must be assessed. Methods and Results: In order to achieve this objective, ATP tests were performed twice in 80 patients (44 men, 36 women; mean age 72.3 ± 12.2 years) by using the recently published test procedure and criteria of positivity. The second test was repeated shortly after the initial test (mean: 7 days) in 43 patients and long‐term (mean: 3.7 years) in 37 patients. The initial ATP test provoked a cardiac pause > 10 seconds in 31 patients (39%) and a short cardiac pause (< 10 sec) or n pause in 49 patients (61%). The electrocardiographic outcome was reproduced during the second ATP test in 36 patients (84%) of the short‐term group and in 29 patients (78%) of the long‐term group. Similarly, symptoms were reproduced in 38 patients (88%) of the short‐term group and 29 patients (78%) of the long‐term group, reflecting the severity of the electrocardiographic outcome. Conclusion: The negative chronotropic and dromotropic vagal effect of ATP can he reproduced short term and long term in 84% and 78% of patients, respectively. Associated symptoms were related to the severity of the electrocardiographic outcome.
Verapamil‐Sensitive Left Anterior Fascicular Ventricular Tachycardia: Results of Radiofrequency Ablation in Six Patients
Authors: NOGAMI AKIHIKO , NAITO SHIGETO , TADA HIROSHI , OSHIMA SHIGERU , TANIGUCHI KOICHI , AONUMA KAZUTAKA , IESAKA YOSHITO 
Published: April 2007

Verapamil‐Sensitive Left Anterior Fascicular VT. Introduction: Verapamil‐sensitive left ventricular tachycardia (VT) with a right bundle branch block (RBBB) configuration and left‐axis deviation bas been demonstrated to arise from the left posterior fascicle, and can be cured by catheter ablation guided by Purkinje potentials. Verapamil‐sensitive VT with an RBBB configuration and right‐axis deviation is rare, and may originate in the left anterior fascicle. Methods and Results: Six patients (five men and one woman, mean age 54 ± 15 years) with a history of sustained VT with an RBBB configuration and right‐axis deviation underwent electrophysiologic study and radiofrequency (RF) ablation. VT was slowed and terminated by intravenous administration of verapamil in all six patients. Left ventricular endocardial mapping during VT identified the earliest ventricular activation in the anterolateral wall of the left ventricle in all patients. RF current delivered to this site suppressed the VT in three patients (ablation at the VT exit). The fused Purkinje potential was recorded at that site, and preceded the QRS complex by 35, 30, and 20 msec, with pace mapping showing an optimal match between the paced rhythm and the clinical VT. In the remaining three patients, RF catheter ablation at the site of the earliest ventricular activation was unsuccessful. In these three patients, Purkinje potential was recorded in the diastolic phase during VT at the mid‐anterior left ventricular septum. The Purkinje potential preceded the QRS during VT by 66, 56, and 63 msec, and catheter ablation at these sites was successful (ablation at the zone of slow conduction). During 19 to 46 months of follow‐up (mean 32 ± 9 months), one patient in the group of ablation at the VT exit bad sustained VT with a left bundle branch block configuration and an inferior axis, and one patient in the group of ablation at the zone of slow conduction experienced typical idiopathic VT with an RBBB configuration and left‐axis deviation. Conclusion: Verapamil‐sensitive VT with an RBBB configuration and right‐axis deviation originates close to the anterior fascicle. RF catheter ablation can be performed successfully from the VT exit site or the zone of slow conduction where the Purkinje potential was recorded in the diastolic phase.
Lead Fixation in Dogs Achieved with RF Energy
Authors: BONNER MATTHEW , MEHRA RAHUL , ZIPES DOUGLAS P. 
Published: April 2007

Lead Fixation in Dogs Achieved with RF Energy. Introduction: The purpose of this study was to test whether radiofrequency (RF) energy could be used to fixate leads to the endocardium. Methods and Results: In six dogs we measured the dislodgment force and pacing threshold before and after RF Fixation in the coronary sinus (CS) and right ventricle (RV). RF fixation was achieved with a CardioRhythm Atakr* ablation unit. The dislodgment force of CS leads fixed with RF energy was 1.63 ± 0.65 oz, compared with < 0.1 oz for similar leads placed in the CS of six separate dogs. In the RV, leads fixed with RF energy had a dislodgment force of 1.29 ± 0.27 oz, compared with 0.48 ± 0.28 oz. for urethane (P < 0.01) and 1.01 ± 0.21 oz for silicone (P= 0.41) tined leads. In the CS, the pacing threshold for RF fixed leads increased significantly from 2.2 ± 1.1 V (0.5 msec) before fixation to 4.2 ± 1.3 V after fixation (P < 0.01), while in the RV, the pacing threshold increased from 0.41 ± 0.05 V (0.5 msec) before fixation to a mean of 2.03 ± 0.44 V after fixation (P < 0.01). In another group of six dogs studied for 12 weeks. 5 of 6 RF fixed CS leads remained attached, as did 8 of 10 RF fixed RV leads. For the RV leads, the mean pacing threshold was 0.90 ± 0.35 V, compared with 0.53 ± 0.18 V (0.5 msec) for similar tined leads (P= 0.02) and 1.2 ± 0.30 V (0.5 msec) for screw leads (P= 0.18) in the RV. Conclusion: We conclude that RF energy can be used to attach leads to the RV and CS endocardium. While the RV pacing thresholds increased acutely, the mean chronic thresholds were not significantly different for RF fixed leads and standard tined or screw leads.
Evolution of the Organization of Epicardial Activation Patterns During Ventricular Fibrillation
Authors: HUANG JIAN , ROGERS JACK M. , KENKNIGHT BRUCE H. , ROLLINS DENNIS L. , SMITH WILLIAM M. , IDEKER RAYMOND E. 
Published: April 2007

Activation During Ventricular Fibrillation. Introduction: This study quantified how the organization of epicardial activation changes during the first 40 seconds of ventricular fibrillation (VF).Activation During Ventricular Fibrillation. Introduction: This study quantified how the organization of epicardial activation changes during the first 40 seconds of ventricular fibrillation (VF). Methods and Results: Unipolar potentials were mapped from a 504 (24 × 21) electrode array (2‐mm interelectrode spacing) on the anterior right ventricle (RV) and left ventricle (LV) epicardium. The array covered approximately 20% of the epicardial surface. In each of seven pigs, six episodes of VF were induced by premature stimulation. One‐half second epochs of VF were analyzed, starting 0, 10, 20, 30, and 40 seconds post induction and using novel pattern analysis algorithms. Eight parameters were quantified: (1) the number of wavefronts; (2) the epicardial area activated by wavefronts; (3) the fraction of wavefronts arising from epicardial breakthrough or from a focus; (4) the fraction of wavefronts terminated by conduction block; (5) the multiplicity index (number of distinct activation pathways in the rhythm); (6) the repeatability index (number of times activation pathways are traversed); (7) the activation rate; and (8) the wavefront propagation velocity. The results showed that VF patterns were less organized at 10 than at 0 seconds, with more, smaller wavefronts traversing a larger variety of pathways for fewer repetitions. VF activation patterns then gradually reorganized up to 40 seconds, but by a different mechanism: the spatial size of subpatterns grew, but the dynamics otherwise appeared unchanged. During both transitions, both activation rate and propagation velocity slowed monotonically. Conclusion: Thus, changes in organization during VF can occur by multiple mechanisms.
Radiofrequency Current Application on Immature Porcine Atrial Myocardium: No Evidence of Areas of Slow Conduction After 12‐Month Follow‐Up
Authors: WINDHAGEN‐MAHNERT BRITTA , BOKENKAMP REGINA , BERTRAM HARALD , PEUSTER MATTHIAS , HAUSDORF GERD , PAUL THOMAS 
Published: April 2007

Electrophysiologic Sequelae 12 Months After Radiofrequency Current Application. Introduction: Radiofrequency current (RFC) application is a widely used procedure for treatment of supraventricular arrhythmias. The purpose of this study was to investigate late electrophysiologic sequelae of RFC lesions at immature atrial myocardium in pigs, as they have not yet been systematically investigated in vitro. Methods and Results: RFC application (temperature guided) was performed in seven piglets (mean age 6 weeks) by a steerahle 6‐French electrode catheter positioned at the lateral aspect of the tricuspid valve annulus. After 12 months, hearts were removed, and lesions with surrounding tissue were isolated. The viable tissue at the border of the specimen was paced with a cycle length of 500 and 600 msec. One hundred fifty impalements were performed on each specimen using capillary microelectrodes to record action potential characteristics from the lesion's surface and the surrounding tissue. In all seven specimens, no transmembrane action potentials from the fibrotic surface of each of the lesions could be recorded. The surrounding viable tissue was sharply demarcated electrically. No areas of slow conduction were detected. Action potential characteristics as mean maximum diastolic transmembrane potential, mean action potential duration at 90% repolarization, and upstroke velocity of phase 0 of the action potential were all normal. Conclusion: No evidence of areas of slow conduction 12 months after RFC application at immature atrial myocardium suggests that this technique is safe regarding occurrence of late atrial tachyarrhythmias after the procedure.
Effect of Skin Electrode Location on Radiofrequency Ablation Lesions: An In Vivo and a Three‐Dimensional Finite Element Study
Authors: JAIN MUDIT K. , TOMASSONI GERY , RILEY RICHARD E. , WOLF PATRICK D. 
Published: April 2007

Skin Electrode Location Affects RF Ablation Lesions. Introduction: Objectives: To assess the effect of skin electrode location on radiofrequency (RF) ablation lesion dimensions and energy requirements. Background: Little is known about the effects of skin electrode location on RF ablation lesion dimensions and efficiency. Methods and Results: Temperature‐controlled ablation at 60°C for 60 seconds was performed in six sheep. Paired lesions were created in the lateral, anterior, posterior, and septal walls of both the ventricles. For group 1 lesions, the skin electrode was positioned directly opposite the catheter tip (optimal). For group 2 lesions, we used either the standard posterior location or an anterior location if the posterior skin electrode location was used for group 1. Group 1 lesions were 5.8 × 0.8 mm deep and 9.3 × 1.9 mm wide, compared with 4.6 × 1.0 m deep and 7.7 × 1.9 mm wide group 2 lesions (P < 0.001). Group 1 lesion dimensions also bad less variability. A finite element model was used to simulate temperature‐controlled ablation and to study the effect of skin electrode locations on lesion dimensions, ablation efficiency, and blood beating. The optimal location was 1.6 times more efficient, and the volume of blood heating to ≥ 90° C was 0.005 mm3 for optimal versus 2.2 mm3 for the nonoptimal location. Conclusion: Optimal skin electrode placement: (1) creates deeper and larger lesions; (2) reduces lesion size variability; and (3) decreases blood beating.
Cytochalasin D as Excitation‐Contraction Uncoupler for Optically Mapping Action Potentials in Wedges of Ventricular Myocardium
Authors: WU JIASHIN , BIERMANN MARTIN , RUBART MICHAEL , ZIPES DOUGLAS P. 
Published: April 2007

Myocardium Immobilization for Repolarization Mapping. Introduction: Cytochalasin D In tissue bath superfusate inhihits the contraction of isolated thin trabeculae from canine right ventricle without affecting the intracellular action potential recorded with glass microelectrode. The purpose of this study was to test whether cytochalasin D could also be used to immobilize perfused wedges of ventricular muscle without affecting the action potential duration or propagation, and also to determine the optimal concentration and time duration of drug in the perfusate. Methods and Results: Using a membrane potential sensitive dye, di‐4‐ANEPPS, and a high‐resolution photodiode optical mapping system at a rate of 1,000 frames/sec, we recorded action potentials on the transmural surface of arterially perfused wedges of muscle from the canine left ventricular free wall. We also recorded arterial pulse pressure as a surrogate for tissue contraction. Cytochalasin D at ≥ 20 μmol/L in the perfusate for ≥ 6 minutes reduced the arterial pulse pressure to approximately one tenth of its initial value and significantly reduced or eliminated motion artifacts in the action potentials. A sustained concentration of 10μmol/L cytochalasin D in the perfusate prevented contraction from recurring after the tissue was immobilized with an initial concentration of 25 μmol/L. Cytochalasin D had little effect on the action potential duration and on its transmural gradient, and did not slow the transmural velocity of excitation propagation. Conclusion: Cytochalasin D can be used to uncouple excitation and contraction in perfused canine cardiac muscle for the fluorescent‐optical mapping of action potentials without affecting action potential duration or slowing transmural propagation.