bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pharmacologic Cardioversion of Chronic Atrial Fibrillation in the Goat by Class IA, IC, and III Drugs
Authors: WIJFFELS MAURITS C.E.F. , DORLAND RICK , ALLESSIE MAURITS A. 
Published: April 2007

Pharmacologic Cardioversion of Chronic AF. Introduction: Recently, we reported that repetitive induction of atrial fibrillation (AF) in the goat causes electrical remodeling of the atria leading to the development of sustained AF. The aim of the present study was to compare Class IA, IC, and III drugs in their ability to cardiovert chronic AF in remodeled atria. Methods and Results: In 16 goats with sustained AF, hydroquinidine (HQ), cibenzoline (Ci), flecainide (FI), and d‐sotalol (dS) were infused. HQ, Ci, FI, and dS restored sinus rhythm (SR) in 83%, 91%, 67%, and 92% of the cases, while adverse drug effects occurred in 17%, 36%, 56%, and 8%. Prior to restoration of SR, AF cycle length prolonged by 68%, 103%, 53%, and 20%, respectively. The QRS width increased by 14%, 64%, and 58% (HQ, Ci, and FI), and remained unchanged by administration of dS. RR intervals were slightly prolonged by HQ, Ci, and FI, and markedly prolonged by dS (48%). The QT interval was moderately prolonged by HQ, Ci, and FI, and considerably by dS (34%). QTc was only slightly prolonged by each of the drugs. Directly after cardioversion of AF, the atrial refractory period was 87 ± 29 (HQ), 119 ± 32 (Ci), 66 ± 10 (FI), and 73 ± 18 msec (dS) (control: 146 ± 18 msec). Atrial conduction velocity was 85 ± 6, 71 ± 11, 86 ± 12, and 110 ± 11 cm/sec compared with a control value of 116 ± 10 cm/sec. Because directly after cardioversion the atrial wavelength was still very short (5.7 to 8.4 cm), the vulnerability for AF was still very high, and a single premature beat reinduced AF in 71% (Ci) to 100% (HQ, FI, and dS) of the cases. Conclusion: In a goat model of sustained AF, Class IA, IC, and III drugs restored sinus rhythm in 67% to 92% of the cases. However, after cardioversion, the atrial wavelength was still abnormally short, and AF was readily inducible in 71% to 100% of the cases.
Right Atrial Focal Atrial Fibrillation
Authors: CHEN SHIH‐ANN , TAI CHING‐TAI , YU WEN‐CHUNG , CHEN YI‐JEN , TSAI CHIN‐FENG , HSIEH MING‐HSIUNG , CHEN CHIEN‐CHENG , PRAKASH V.S. , DING YU‐AN , CHANG MAU‐SONG 
Published: April 2007

Focal Atrial Fibrillation. Introduction: Information about focal atrial fibrillation (AF) originating from the right atrium bas not been well described. The purposes of this study were to demonstrate the electrophysiologic characteristics and radiofrequency catheter ablation in patients who bad right atrial focal AF. Methods and Results: From January 1996 to September 1998, 172 patients with clinically documented attacks of paroxysmal AF were referred to this institution for electrophysiologic study and/or radiofrequency catheter ablation. Anterior free wall, crista terminalis, and right and left superior pulmonary veins were mapped simultaneously. Eight patients (4.7%) had right atrial focal AF, consistent activation sequence, irregular fibrillation interval (mean fibrillation interval: 164 ± 11 msec), and episodes of exit block from the initiating foci observed. The presumed ablation site was chosen on the basis of the earliest bipolar activity relative to an atrial electrogram reference during the initiation of AF. After application of 2 ± 1 radiofrequency pulses, AF was eliminated without recurrence during the follow‐up period (mean: 14 ± 8 months: range: 3 to 25). Twenty‐four‐hour Holter monitoring showed that the number of atrial premature beats decreased significantly at the 3‐month follow‐up (4,216 ± 411 vs 135 ± 14 beats/day). Conclusion: Right atrial focal AF is one subgroup of focal AF, and it can be cured by radiofrequency catheter ablation.
Histopathologic Effects of Radiofrequency Catheter Ablation in Previously Infarcted Human Myocardium
Authors: GRUBMAN ERIC , PAVRI BEHZAD B. , LYLE STEPHEN , REYNOLDS CAROL , DENOFRIO DAVID , KOCOVIC DUSAN Z. 
Published: April 2007

Radiofrequency Ablation in Infarcted Myocardium. Introduction: The use of catheter‐based radiofrequency (RF) ablation for the treatment of ventricular tachyarrhythmias due to previous myocardial infarction has been steadily increasing. The histopathologic changes caused by this technique are not well described in humans. Methods and Results: Three patients with hemodynamically tolerated ventricular tachycardias (VTs) due to previous myocardial infarction underwent endocardial mapping and catheter based RF ablation. All patients received between 5 and 11 RF lesions each of 60‐second duration. One patient underwent myocardial resection of a left ventricular aneurysm 1 day following RF ablation, one expired 7 days after RF ablation, and one expired 9 months after RF ablation. None of the deaths occurred as a result of RF ablation. Pathologic specimens obtained early after RF ablation revealed areas of focal acute Inflammation and fibrin deposition. Later specimens revealed several focal areas of fibrosis and granulation tissue. Specimens obtained late after RF ablation revealed a dense band of fibrosis, measuring 17 × 17 × 5 mm (1,250 mm3). Conclusion: Catheter‐based RF ablation of ischemic VT in humans causes lesions that Initially resemble coagulation necrosis. This is followed by the development of an inflammatory infiltrate and, finally, the development of fibrosis. Repeated application of RF ablation may result in much larger lesions than have been previously reported.
Transmural Atrial Pacing in Patients with Postoperative Congenital Heart Disease
Authors: JOHNSRUDE CHRISTOPHER L. , BACKER CARL L. , DEAL BARBARA J. , STRASBURGER JANETTE F. , MAVROUDIS CONSTANTINE 
Published: April 2007

Transmural Pacing in Congenital Heart Disease. Introduction: Some patients with postoperative congenital heart disease require permanent cardiac pacing, but the use of transvenous or epicardial pacing leads may be limited by type of cardiac malformation, venous connections, body size, or fibrosis. Transmural atrial pacing may provide an alternative in difficult patients, but to date has been described in only a few articles with small patient numbers, and data from lead performance are lacking. Methods and Results: Records were reviewed in 18 consecutive patients (4 months to 21 years old) with postoperative congenital heart disease receiving transmural atrial pacing leads from July 1994 to December 1996. Implantation materials and techniques were described. Lead sensing and capture thresholds obtained acutely and during short‐term follow‐up (mean: 11.0 months) were evaluated, and comparisons were made between patients with postoperative Fontan anatomy and non‐Fontan patients, and between patients receiving steroid‐eluting and nonsteroid leads. Overall, the median acute sensing and capture thresholds of transmural leads were 4.1 mV and 0.7 V at 0.5 msec, respectively. Median follow‐up thresholds were 2.8 mV and 0.8 V, respectively. Performance of leads in Fontan patients was similar to those in non‐Fontan patients. Steroid‐eluting leads had a chronic capture threshold of 0.6 V versus 0.9 V for nonsteroid leads (P = 0.038). Conclusion: Transmural atrial pacing leads were successfully implanted in patients with diverse ages and types of postoperative congenital heart disease. Lead performance was acceptable both acutely and during the first year of follow‐up.
Morphological and Physiological Characteristics of Discontinuous Linear Atrial Ablations During Atrial Pacing and Atrial Fibrillation
Authors: MITCHELL MARK A. , McRURY IAN D. , EVERETT THOMAS H. , LI HUI , MANGRUM J. MICHAEL , HAINES DAVID E. 
Published: April 2007

Discontinuous Atrial Ablations. Introduction: Linear atrial ablations are thought to he necessary to accomplish successful catheter ablation of atrial fibrillation. In order to investigate the conduction characteristics of atrial myocardium in regions of linear lesion discontinuity gaps), we performed activation sequence mapping in gap regions during atrial pacing and atrial fibrillation. Methods and Results. In seven dogs, a linear epicardial ablation was created on the right atrial free wall with a discontinuous segment (gap) in the mid‐portion of the lesion. A plaque electrode was used to measure conduction across the gap. Conduction was assessed during (1) atrial pacing from the edge of the plaque electrode during sinus rhythm, and (2) during atrial fibrillation. After each series of measurements, the lesion gap was decreased by creating additional radiofrequency ablations and repeat conduction maps were obtained. The process was repeated until conduction block was observed during atrial pacing. Gap lengths ranged from 0 to 25 mm. During atrial pacing, gaps as narrow as 2 mm demonstrated normal conduction and gaps as large as 5 mm demonstrated block during pacing. Although conduction block was never present across gaps greater than 5 mm, the ability to predict conduction block as a function of gap width was difficult for lesions ≤ 5 mm due to a significant degree of overlap between normal conduction and conduction block in this gap range. During atrial fibrillation, 1/175 (0.6%) mapped wavelets conducted across gaps that demonstrated block during pacing; whereas, 411/600 (68.5%; P < 0.0001) wavelets conducted across gaps that did not demonstrate block during pacing (P = NS compared to preablation measurements). Histologically normal atrial myocytes were observed within gaps exhibiting conduction block. Conclusions: Visible gaps > 5 mm rarely demonstrate conduction block during atrial pacing and atrial fibrillation; whereas, gaps ≤ 5 mm in length may demonstrate block. Lesion gaps that do not demonstrate conduction block during atrial pacing have no higher rate of functional conduction block during atrial fibrillation than fibrillating atria without ablation lesions.
Optimal Target Site for Slow AV Nodal Pathway Ablation
Authors: YAMANE TEIICHI , IESAKA YOSHITO , GOYA MASAHIKO , TAKAHASHI ATSUSHI , FUJIWARA HIDEOMI , HIRAOKA MASAYASU 
Published: April 2007

Optimal Target Site for Slow AV Nodal Pathway. Introduction: Although a variety of ablation techniques have been developed in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT), there have been few reports discussing the location of the optimal target site. Based on our early experiences, we hypothesized that radiofrequency (RF) current applied around the upper margin of the coronary sinus ostium (UCSO) results in the most effective and safe treatment of AVNRT. Methods and Results: To confirm our hypothesis, the efficacy of RF currents applied around the UCSO guided by local electrograms in 59 patients (group B: predetermined focal mapping approach) were compared with the outcomes in 60 other patients previously treated with the standard electrogram‐guided mapping method starting around the lower margin of the coronary sinus ostium (group A). The precise location of ablation catheters at successful sites (S) was also evaluated. All the patients were successfully treated without complications. Significantly fewer RF pulses and lower energies were needed in group B patients (mean RF applications: 4.3 vs 1.4 applications, mean total energy delivered: 4,699 vs 2,236 J in groups A and B, respectively, P < 0.01). Detailed analyses of the anatomical locations of S using CS venography in group B patients who received only a single RF application (46 patients) revealed that the distance between His and S varied according to the length of Koch's triangle, while that between S and UCSO was relatively constant. In 85% of these 46 patients, S was located within 5 mm above and below the level of the UCSO. Conclusion: RF applications around the UCSO guided by local electrograms yielded excellent outcomes in AVNRT patients with wide varieties in the size of Koch's triangle. The optimal target site was located within 5 mm above and below the level of UCSO along the tricuspid annulus.
Alterations in Gene Expression of Proteins Involved in the Calcium Handling in Patients with Atrial Fibrillation
Authors: VAN GELDER ISABELLE C. , BRUNDEL BIANCA J.J.M. , HENNING ROBERT H. , TUINENBURG ANTON E. , TIELEMAN ROBERT G. , DEELMAN LEO , GRANDJEAN JAN G. , DE KAM PIETER JAN , VAN GILST WIEK H. , CRIJNS HARRY J.G.M. 
Published: April 2007

Gene Expression in Human Atrial Fibrillation. Introduction: Atrial fibrillation (AF) leads to a loss of atrial contraction within hours to days. During persistence of AF, cellular dedifferentiation and hypertrophy occur, eventually resulting in degenerative changes and cell death. Abnormalities in the calcium handling in response to tachycardia‐induced intracellular calcium overload play a pivotal role in these processes. Methods and Results: The purpose was to investigate the mRNA expression of proteins and ion channels influencing the calcium handling in patients with persistent AF. Right atrial appendages were obtained from 18 matched controls in sinus rhythm (group 1) and 18 patients with persistent AF undergoing elective cardiac surgery. Previous duration of AF was ≥ 6 months in 9 (group 2) and > 6 months in 9 patients (group 3). In a single semiquantitative polymerase chain reaction, the mRNA of interest and of glyceraldehydes‐3‐phosphate dehydrogenase, were coamplified and separated by gel electrophoresis. L‐type calcium channel α, subunit mRNA content was inversely related to the duration of AF: −26% in group 2 compared to group 1 (P = 0.2), and −49% in group 3 compared to group 1 (P = 0.01). Inhibitory guanine nucleotide binding protein iα2 mRNA content was reduced in group 3 compared to group 1 (−30%, P = 0.01). Sarcoplasmic reticulum calcium ATPase, phospholamban and sodiumcalcium exchanger mRNA contents were not affected by AF. Conclusions: AF‐induced alterations in mRNA contents of proteins and ion channels involved in the calcium handling seem to occur in relation to the previous duration of AF. In the present patient population, these changes were significant only if AF lasted > 6 months.
Biventricular Shocking Leads Improve Defibrillation Efficacy
Authors: YAMANOUCHI YOSHIO , EFIMOV IGOR R. , MOWREY KENT A. , MAZGALEV TODOR N. , WILKOFF BRUCE L. , TCHOU PATRICK J. 
Published: April 2007

Biventricular Shocking Leads:Introduction: A single lead active can configuration has been widely used in patients with life‐threatening ventricular arrhythmias. Occasionally, however, such a defibrillation lead configuration may not achieve adequate defibrillation threshold (DFT). The purpose of this study was to determine whether addition of a left ventricular (LV) lead can improve defibrillation efficacy. Methods and Results: Three transvenous defibrillation leads (8.3‐French with a 5‐cm long unipolar coil) were placed in the right ventricle (RV), LV, and superior vena cava (SVC), along with an active can (92 cm2) in the left subpectoral area. The DFT stored energy of seven combinations of these defibrillation leads were compared in a pig ventricular fibrillation model using a biphasic defibrillation waveform (125 μF, 6.5/3.5 msec). A biventricular leads active can configuration in which the RV and LV leads were of the same polarity reduced the DFT stored energy by approximately 35% when compared to a single RV lead active can configuration (9.6 ± 3.0 J vs 15.0 ± 7.2 J, respectively, P = 0.02). Moreover, adding a SVC lead further reduced the DFT energy (8.4 ± 3.3 J). Conclusion: A biventricular leads active can configuration can significantly improve defibrillation efficacy as compared to a single lead active can configuration. In such a defibrillation lead configuration, the polarity of RV and LV leads should be the same.
Quatrefoil Reentry in Myocardinm: An Optical Imaging Study of the Induction Mechanism
Authors: LIN SHIEN‐FONG , ROTH BRADLEY J. , WIKSWO JOHN P. 
Published: April 2007

Quatrefoil Reentry in Myocardium. Introduction: The “critical point hypothesis” for induction of ventricular fibrillation has previously been extended to infer the coexistence of four critical points, and hence four simultaneous spiral reentries or a quatrefoil reentry, resulting from only one premature stimulus delivered to the same location as the pacing stimulus. An optical imaging technique was used to explore its existence and to study the induction mechanism of this peculiar reentry pattern. Methods and Results: In 16 isolated, Langendorff‐perfused rabbit hearts, high‐speed optical imaging at 133 or 267 frames/sec was performed to observe the induced response with a unipolar point electrode. A novel quatrefoil‐shaped reentry pattern consisting of two pairs of opposing rotors was created by delivering long stimuli during the vulnerable phase. Successful induction occurred in a narrow range of coupling intervals. A dogbone pattern of virtual electrodes was established during the premature stimulus. Propagating wavefronts launched from the virtual anodes immediately after the termination of S2. The alternating blocking and conducting effects of the virtual electrodes, as well as the boundary between virtual cathode and virtual anode, provided the necessary pathways for quatrefoil reentry. Propagation directions of the reentrant spiral wavefronts reversed with a reversal in S2 polarity. Quatrefoil reentries were not sustained and lasted 1 to 4 complete cycles. Conclusion: The initiation of quatrefoil reentry followed anodal‐or cathodal‐break stimulation as a result of local symmetrical enhancement of the dispersion of tissue excitability. The “critical point hypothesis” provides the minimum topology required for this type of reentry; the “graded response hypothesis” can be viewed as providing a more detailed explanation of how this topology is actually realized. Triggering mechanisms due to the “break” mode of stimulation also posits a new mechanism for defibrillation.
Effects of 17β‐Estradiol on Tachycardia‐Induced Changes of Atrial Refractoriness and Cisapride‐Induced Ventricular Arrhythmia
Authors: CHEN YI‐JEN , LEE SHIH‐HUANG , HSIEH MING‐HSIUNG , HSIAO CHIEN‐JU , YU WEN‐CHUNG , CHIOU CHUEN‐WANG , CHEN SHIH‐ANN 
Published: April 2007

17β‐Estradiol and Arrhythmia.Introduction: Gender difference is known to be associated with the occurrence of arrhythmia. However, the effects of female sex hormone on atrial electrophysiology, and on the occurrence of torsades de pointes (TdP) induced by cisapride have been unclear.Methods and Results: Two experiments were included in this study. In experiment 1, effective refractory periods (ERPs) from five epicardial atrial sites were measured before and after rapid atrial pacing at 800 beats/min for 30 minutes in dogs with pretreatment of verapamil (n = 10), 17β‐estradiol (n = 10), or without pretreatment (n = 10, control group). In experiment 2, limb‐lead ECG and monophasic action potentials in the left and right ventricles were recorded before and after each dose of cisapride (2 to 6 mg/kg) during different ventricular rates in dogs with (n = 9) and without (n = 14) concomitant administration of 17β‐estradiol (0.3 μg/kg). After 17β‐estradiol administration, there were greater atrial ERPs in the study dogs than in the control group. The atrial ERPs were shortened significantly after rapid atrial pacing, but the degree was greater in the control group than in the dogs pretreated with verapamil or 17β‐estradiol. Moreover, the recovery of atrial ERPs was faster in dogs pretreated with verapamil or 17βestradiol than in the control group. In experiment 2, cisapride prolonged the QT interval and biventricular APD)90and induced early afterdepolarizations (EADs) in a dose‐dependent manner. However, dogs receiving cisapride combined with 17β‐estradiol had a greater increase of ventricular repolarization and a higher incidence of EADs than those receiving cisapride only. Moreover, dogs receiving cisapride combined with 17β‐estradiol (3/9, 33%) bad a greater incidence of TdP tban those receiving cisapride only (0/14, 0%, P < 0.05).Conclusions: 17β‐estradiol has a significant effect on atrial electrophysiology, which may be related to the prevention of atrial fibrillation. However, the high incidence of TdP in dogs receiving cisapride combined with 17β‐estradiol suggests that the female sex hormone is an important risk factor of cisapride‐induced proarrhythmia.
Clinical Experience with the New Detection Algorithms for Atrial Fibrillation of a Defibrillator with Dual Chamber Sensing and Pacing
Authors: KÜHLKAMP VOLKER , DÖRNBERGER VOLKER , MEWIS CHRISTIAN , SUCHALLA RALF , BOSCH RALPH E. , SEIPEL LUDGER 
Published: April 2007

ICD with DDD Pacemaker. Introduction: A major drawback of therapy with an implantable defibrillator is the nonspecificity of detection. Theoretically, adding atrial sensing information to a decision algorithm could improve specificity of detection. Methods and Results: This open‐label nonrandomized study compares the detection algorithm of the Ventak AV and the Ventak Mini implantable defibrillators. The Ventak AV (n = 39) uses dual chamber detection as opposed to single chamber detection (with rate stability) in the Ventak Mini (n = 55). Programmed zone configurations, rate thresholds, and stability criteria were identical in all patients. In the Ventak AV group, 235 ventricular tachyarrhythmias were adequately detected and treated by the device. In the Mini group, 699 episodes of ventricular fibrillation/tachycardia occurred. All but six of the latter episodes were correctly identified and treated: one patient with incessant ventricular tachycardia had five episodes not terminated by the device, another episode occurred in a patient with a device/lead defect. In the Ventak AV group, 33 episodes of sinus tachycardia and 166 episodes of atrial fibrillation/flutter activated the device; inappropriate therapy was applied to 41% of atrial fibrillation/flutter episodes. In the Ventak Mini group, 226 supraventricular tachyarrhythmias activated the device, eight of which were sinus tachycardia and 218 were atrial fibrillation or flutter; of the atrial fibrillation/flutter episodes 24% were treated inappropriately (fewer vs Ventak AV, P < 0.001). Conclusion: The new detection algorithm incorporated in the Ventak AV did not inadvertently withhold therapy for ventricular tachyarrhythmias, but at the same time the number of inappropriate therapies for atrial fibrillation was not decreased in comparison to a single chamber device.
Effects of Multisite Ventricular Pacing on Cardiac Function in Normal Dogs and Dogs with Heart Failure
Authors: FEI LÜ , WROBLESKI DAVID , GROH WILLIAM , VETTER ALISEN , DUFFIN EDWIN G. , ZIPES DOUGLAS P. 
Published: April 2007

Multisite Ventricular Pacing in Heart Failure. Introduction: We studied the effects on cardiac function of pacing two right and two left ventricular sites in normal and failing hearts with a normal QRS duration. Methods and Results: Hemodynamic parameters were studied in isoflurane‐anesthetized dogs with normal hearts and dogs with heart failure induced by rapid ventricular pacing. Unipolar intramyocardial electrodes were placed at the high right atrium and the apex (A) and base (B) of the left (L) and right (R) ventricles (V). Data were collected after pacing for 5 to 20 minutes. In normal dogs, without bundle branch block (BBB), pacing at either the apex or the base of the left ventricle increased cardiac output by approximately 10% compared with right ventricular apex (RVA) pacing with an AV delay of 10 msec. Positive dP/dt increased approximately 10% during four‐site left and right ventricular apex and base (LRVAB) pacing compared with RVA pacing. In dogs with heart failure but without BBB, cardiac output increased by 8.5% (P < 0.01) during four‐site ventricular pacing with AV delays of 0 and 60 msec compared with RVA pacing. Positive dp/dt increased by 23.5% (P < 0.001) with an AV delay of 0 msec and 9.6% (P < 0.001) with an AV delay of 60 msec during LRVAB pacing compared with RVA pacing. His‐bundle pacing was associated with increased cardiac output compared with RVA pacing. Conclusions: We conclude that pacing simultaneously at two right and two left ventricular sites significantly improves cardiac function compared with single RVA pacing, with or without sequential AV synchrony, in dogs with rapid ventricular pacing‐induced heart failure and no BBB.