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Electrograms
Kinds of Electrograms Terms modified by Electrograms Selected AbstractsDetermining the Local Time of Activation from the Unipolar Electrogram: New Methods, New ChallengesJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000BONNIE B. PUNSKE PH.D. [source] A Coroner's Request for Closure: The Value of the Stored ElectrogramPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2006IRENE H. STEVENSON Pacemaker diagnostics can be useful to troubleshoot both during life and after death. A 58-year old man with a single chamber ventricular pacemaker and a previous His bundle ablation died suddenly. Interrogation of his pacemaker revealed the cause of death not as pacemaker malfunction, but a fatal ventricular arrhythmia. [source] Double Counting of the Ventricular Electrogram in Biventricular Pacemakers and ICDsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2003S. SERGE BAROLD First page of article [source] Effects of an adapted intravenous amiodarone treatment protocol in horses with atrial fibrillationEQUINE VETERINARY JOURNAL, Issue 4 2007D. de CLERCQ Summary Reason for performing study: Good results have been obtained with a human amiodarone (AD) i.v. protocol in horses with chronic atrial fibrillation (AF) and a pharmacokinetic study is required for a specific i.v. amiodarone treatment protocol for horses. Objectives: To study the efficacy of this pharmacokinetic based i.v. AD protocol in horses with chronic AF. Methods: Six horses with chronic AF were treated with an adapted AD infusion protocol. The protocol consisted of 2 phases with a loading dose followed by a maintenance infusion. In the first phase, horses received an infusion of 6.52 mg AD/kg bwt/h for 1 h followed by 1.1 mg/kg bwt/h for 47 h. In the second phase, horses received a second loading dose of 3.74 mg AD/kg bwt/h for 1 h followed by 1.31 mg/kg bwt/h for 47 h. Clinical signs were monitored, a surface ECG and an intra-atrial electrogram were recorded. AD treatment was discontinued when conversion or any side effects were observed. Results: Three of the 6 horses cardioverted successfully without side effects. The other 3 horses did not convert and showed adverse effects, including diarrhoea. In the latter, there were no important circulatory problems, but the diarrhoea continued for 10,14 days. The third horse had to be subjected to euthanasia because a concomitant Salmonella infection worsened the clinical signs. Conclusion: The applied treatment protocol based upon pharmacokinetic data achieved clinically relevant concentrations of AD and desethylamiodarone. Potential relevance: Intravenous AD has the potential to be an alternative pharmacological treatment for AF in horses, although AD may lead to adverse drug effects, particularly with cumulative dosing. [source] Usefulness of Interatrial Conduction Time to Distinguish Between Focal Atrial Tachyarrhythmias Originating from the Superior Vena Cava and the Right Superior Pulmonary VeinJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2008KUAN-CHENG CHANG M.D. Objective: Differentiation of the tachycardia originating from the superior vena cava (SVC) or the right superior pulmonary vein (RSPV) is limited by the similar surface P-wave morphology and intraatrial activation pattern during tachycardia. We sought to find a simple method to distinguish between the two tachycardias by analyzing the interatrial conduction time. Methods: Sixteen consecutive patients consisting of 8 with SVC tachycardia and the other 8 with RSPV tachycardia were studied. The interatrial conduction time from the high right atrium (HRA) to the distal coronary sinus (DCS) and the intraatrial conduction time from the HRA to the atrial electrogram at the His bundle region (HIS) were measured during the sinus beat (SR) and during the tachycardia-triggering ectopic atrial premature beat (APB). The differences of interatrial (,[HRA-DCS]SR-APB) and intraatrial (,[HRA-HIS]SR-APB) conduction time between SR and APB were then obtained. Results: The mean ,[HRA-DCS]SR-APB was 1.0 ± 5.2 ms (95% confident interval [CI],3.3,5.3 ms) in SVC tachycardia and 38.5 ± 8.8 ms (95% CI 31.1,45.9 ms) in RSPV tachycardia. The mean ,[HRA-HIS]SR-APB was 1.5 ± 5.3 ms (95% CI ,2.9,5.9 ms) in SVC tachycardia and 19.9 ± 12.0 ms (95% CI 9.9,29.9 ms) in RSPV tachycardia. The difference of ,[HRA-DCS]SR-APB between SVC and RSPV tachycardias was wider than that of ,[HRA-HIS]SR-APB (37.5 ± 9.3 ms vs. 18.4 ± 15.4 ms, P < 0.01). Conclusions: The wide difference of the interatrial conduction time ,[HRA-DCS]SR-APB between SVC and RSPV tachycardias is a useful parameter to distinguish the two tachycardias and may avoid unnecessary atrial transseptal puncture. [source] Predictors of All-Cause Mortality for Patients with Chronic Chagas' Heart Disease Receiving Implantable Cardioverter Defibrillator TherapyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2007AUGUSTO CARDINALLI-NETO M.D., Ph.D. Background: Implantable Cardioverter Defibrillators (ICD) have sporadically been used in the treatment of either Sustained Ventricular Tachycardia (VT) or Ventricular Fibrillation (VF) in Chagas' disease patients. This study aimed at determining predictors of all-cause mortality for Chagas' disease patients receiving ICD therapy. Methods and Results: Ninety consecutive patients were entered the study. Mean left ventricular ejection fraction was 47 ± 13%. Twenty-five (28%) patients had no left ventricular systolic dysfunction. After device implantation, all patients were given amiodarone (mean daily dose = 331, 1 ± 153,3 mg), whereas a B-Blocking agent was given to 37 (40%) out of 90 patients. Results: A total of 4,274 arrhythmias were observed on stored electrogram in 64 (71%) out of 90 patients during the study period; SVT was observed in 45 out of 64 (70%) patients, and VF in 19 (30%) out of 64 patients. Twenty-six (29%) out of 90 patients had no arrhythmia. Fifty-eight (64%) out of 90 patients received appropriate shock, whereas Antitachycardia Pacing was delivered to 58 (64%) out of 90 patients. There were 31 (34%) deaths during the study period. Five patients were lost to follow up. Sudden cardiac death affected 2 (7%) out of 26 patients, whereas pump failure death was detected in the remaining 24 (93%) patients. Number of shocks per patient per 30 days was the only independent predictor of mortality. Conclusion: Number of shocks per patient per 30 days predicts outcome in Chagas' disease patients treated with ICD. [source] The VA Relationship After Differential Atrial Overdrive Pacing: A Novel Tool for the Diagnosis of Atrial Tachycardia in the Electrophysiologic LaboratoryJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2007MITSUNORI MARUYAMA M.D. Introduction: Despite recent advances in clinical electrophysiology, diagnosis of atrial tachycardia (AT) originating near Koch's triangle remains challenging. We sought a novel technique for rapid and accurate diagnosis of AT in the electrophysiologic laboratory. Methods: Sixty-two supraventricular tachycardias including 18 ATs (10 ATs arising from near Koch's triangle), 32 atrioventricular nodal reentrant tachycardias (AVNRTs), and 12 orthodromic reciprocating tachycardias (ORTs) were studied. Overdrive pacing during the tachycardia from different atrial sites was performed, and the maximal difference in the postpacing VA intervals (last captured ventricular electrogram to the earliest atrial electrogram of the initial beat after pacing) among the different pacing sites was calculated (delta-VA interval). Results: The delta-VA intervals were >14 ms in all AT patients and <14 ms in all AVNRT/ORT patients, and thus, the delta-VA interval was diagnostic for AT with the sensitivity, specificity, and positive and negative predictive values all being 100%. When the diagnostic value of the delta-VA interval and conventional maneuvers were compared for differentiating AT from atypical AVNRT, both a delta-VA interval >14 ms and "atrial-atrial-ventricular" response after overdrive ventricular pacing during the tachycardia were diagnostic. However, the "atrial-atrial-ventricular" response criterion was available in only 52% of the patients because of poor ventriculoatrial conduction. Conclusions: The delta-VA interval was useful for diagnosing AT irrespective of patient conditions such as ventriculoatrial conduction. [source] Laplacian Electrograms and the Interpretation of Complex Ventricular Activation Patterns During Ventricular FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000PH.D., RUBEN CORONEL M.D. Laplacian Electrograms and Ventricular Fihrillation. Introduction. During ventricular fibrillation (VF) interpretation of a local electrogram and determination of the local activation moment are hampered by remote activity or intervening repolarization waves. Successful defibrillation depends on critical timing of the shock relative to local activation. We tested the applicabillity of Laplacian electrograms for detection of the moment of local activation during VF. Methods and Results. From isolated perfased porcine infact heart, 247 local unipolar electrograms were recorded simultaneously (13 × 19 matrix, interelectrode distance 0.3 mm) from the left ventricular wall during sinus rhythm, following pacing or during VF, Activation maps were constructed based on local unipolar electrograms, and Laplacian electrograms were calculated from local electrograms ane its eight neighbors. The Laplacian electrogram displayed a sharp R/S complex with local activation iodicted by the moment of zero crossing without interference from remote activity or repolarization waves. Its amplitude increased with decreasing interelectrode distance, Following epicardial stimulation, Laplacian amplitude was significantly larger than during complexes with different morphology. Collision of wavefronts was associated with entirely positive Laplacian waveforms; "focal" appearancce of acitivity was associated with an entirely negative waveform. Activation block in the activation maps was correlated with the appearance of substanined episodes of negativity or positivity in the Laplacian electrogram (depending on the location of the recording site relative to the line of block). Conclusion. Laplacian electrograms allow detection of the moment of local activation without interference from remote activity or repolarization, especially during complex arrhythmias. The technique applied toe automatic sensing devices, such its the internal defibrillator, may optimize defibrtilation success. (J Cardiovasc Electrophysiol, Vol. 11, pp. 1119-1128, October 2000) [source] Relationship of Specific Electrogram Characteristics During Sinus Rhythm and Ventricular Pacing Determined by Adaptive Template Matching to the Location of Functional Reentrant Circuits that Cause Ventricular Tachycardia in the Infarcted Canine HeartJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2000EDWARD J. CIACCIO Ph.D. Localization of Reentrant Circuits. Introduction: It would be advantageous, for ablation therapy, to localize reentrant circuits causing ventricular tachycardia by quantifying electrograms obtained during sinus rhythm (SR) or ventricular pacing (VP). In this study, adaptive template matching (ATM) was used to localize reentrant circuits by measuring dynamic electrogram shape using SR and VP data. Methods and Results: Four days after coronary occlusion, reentrant ventricular tachycardia was induced in the epicardial border zone of canine hearts by programmed electrical stimulation. Activation maps of circuits were constructed using electrograms recorded from a multichannel array to ascertain block line location. Electrogram recordings obtained during SR/AP then were used for ATM analysis. A template electrogram was matched with electrograms on subsequent cycles by weighting amplitude, vertical shift, duration, and phase lag for optimal overlap. Sites of largest cycle-to-cycle variance in the optimal ATM weights were found to be adjacent to block lines bounding the central isthmus during reentry (mean 61.1% during SR; 63.9% during VP). The distance between the mean center of mass of the ten highest ATM variance peaks and the narrowest isthmus width was determined. For all VP data, the center of mass resided in the isthmus region ocurring during reentry. Conclusion: ATM high variance measured from SR/AP data localizes functional block lines forming during reentry. The center of mass of the high variance peaks localizes the narrowest width of the isthmus. Therefore, ATM methodology may guide ablation catheter position without resorting to reentry induction. [source] Atrial, SA Nodal, and AV Nodal Electrophysiology in Standing Horses: Normal Findings and Electrophysiologic Effects of Quinidine and DiltiazemJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2007Colin C. Schwarzwald Background: Although atrial arrhythmias are clinically important in horses, atrial electrophysiology has been incompletely studied. Hypotheses: Standard electrophysiologic methods can be used to study drug effects in horses. Specifically, the effects of diltiazem on atrioventricular (AV) nodal conduction are rate-dependent and allow control of ventricular response rate during rapid atrial pacing in horses undergoing quinidine treatment. Animals: Fourteen healthy horses. Methods: Arterial blood pressure, surface electrocardiogram, and right atrial electrogram were recorded during sinus rhythm and during programmed electrical stimulation at baseline, after administration of quinidine gluconate (10 mg/kg IV over 30 minutes, n = 7; and 12 mg/kg IV over 5 minutes followed by 5 mg/kg/h constant rate infusion for the remaining duration of the study, n = 7), and after coadministration of diltiazem (0.125 mg/kg IV over 2 minutes repeated every 12 minutes to effect). Results: Quinidine significantly prolonged the atrial effective refractory period, shortened the functional refractory period (FRP) of the AV node, and increased the ventricular response rate during atrial pacing. Diltiazem increased the FRP, controlled ventricular rate in a rate-dependent manner, caused dose-dependent suppression of the sinoatrial node and produced a significant, but well tolerated decrease in blood pressure. Effective doses of diltiazem ranged from 0.125 to 1.125 mg/kg. Conclusions and Clinical Importance: Standard electrophysiologic techniques allow characterization of drug effects in standing horses. Diltiazem is effective for ventricular rate control in this pacing model of supraventricular tachycardia. The use of diltiazem for rate control in horses with atrial fibrillation merits further investigation. [source] Acute effects of escalating doses of amiodarone in isolated guinea pig heartsJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 3 2002S. BICER Bicer, S., Patchell, J. S., Hamlin, D. M., Hamlin, R. L. Acute effects of escalating doses of amiodarone in isolated guinea pig hearts. J. vet Pharmacol. Therap.25, 221,226. Cardiac effects of escalating concentrations of amiodarone were determined on isolated perfused guinea pig hearts (Langendorff preparations). Spontaneously beating hearts were instrumented for the measurement of RR, PQ, QRS, QT and QTc durations (from a bipolar electrogram), and dP/dtmax and dP/dtmin from an isovolumetric left ventricular pressure curve. Ten hearts were exposed to escalating concentrations of amiodarone (10,7, 10,6, 10,5 and 10,4 M) in dimethyl sulfoxide (DMSO)/Krebs,Henseleit or to DMSO/Krebs,Henseleit (vehicle). Measurements were collected during the last minute of a 15-min concentration. Means of all parameters were compared by ANOVA with repeated measures design. When compared with vehicle, amiodarone prolonged QT and QTc durations at concentrations >10,6 M. The apparent lengthening of RR, PQ and QRS at concentrations >10,6 M did not achieve statistical significance. Similarly, the apparent decreases in dP/dtmax and dP/dtmin at concentrations >10,6 M did not achieve statistical significance. The putative therapeutic concentration of amiodarone is between 2 and 4 × 10,6 M. In this study, at a concentration of 10,6 M, only RR and dP/dtmin tended to change, but they were not different from vehicle. Thus, amiodarone in this preparation has little potential for cardiac toxicity at therapeutic concentrations. [source] A Technique for the Rapid Diagnosis of Wide Complex Tachycardia with 1:1 AV Relationship in the Electrophysiology LaboratoryPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2009AMIR ABDELWAHAB M.B. B.Ch., M.Sc. Background:The differential diagnosis of wide complex tachycardia (WCT) with 1:1 atrioventricular (AV) relationship is broad. Accurate identification of the tachycardia mechanism is essential for successful ablation. We suggest a simple pacing maneuver that can immediately clarify the tachycardia mechanism in the electrophysiology laboratory. Methods:Eight consecutive patients (four males, 32 ± 14 years) demonstrating stable sustained WCT with persistent 1:1 AV relationship during electrophysiologic testing were included in this study. During the tachycardia, atrial overdrive pacing was performed. The following responses were observed: (1) a change of the QRS morphology during atrial pacing and (2) the first return electrogram of the tachycardia, whether occurring in the atrium (AVA response) or in the ventricle (AVVA response). Results:Atrial overdrive pacing was successfully performed in all patients. It was associated with either a change or narrowing of the QRS in all ventricular tachycardia (VT) patients but not in supraventricular tachycardia (SVT) patients. All VT patients had an AVVA response upon cessation of atrial overdrive pacing as opposed to AVA response in SVT patients, P = 0.029. Conclusion:The response to atrial overdrive pacing during WCT with 1:1 AV relationship can rapidly diagnose or rule out VT as a mechanism of tachycardia. [source] Analysis of Atrioventricular Nodal Reentrant Tachycardia with Variable Ventriculoatrial Block: Characteristics of the Upper Common PathwayPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2009KENJI MORIHISA M.D. Background: The precise nature of the upper turnaround part of atrioventricular nodal reentrant tachycardia (AVNRT) is not entirely understood. Methods: In nine patients with AVNRT accompanied by variable ventriculoatrial (VA) conduction block, we examined the electrophysiologic characteristics of its upper common pathway. Results: Tachycardia was induced by atrial burst and/or extrastimulus followed by atrial-His jump, and the earliest atrial electrogram was observed at the His bundle site in all patients. Twelve incidents of VA block: Wenckebach VA block (n = 7), 2:1 VA block (n = 4), and intermittent (n = 1) were observed. In two of seven Wenckebach VA block, the retrograde earliest atrial activation site shifted from the His bundle site to coronary sinus ostium just before VA block. Prolongation of His-His interval occurred during VA block in 11 of 12 incidents. After isoproterenol administration, 1:1 VA conduction resumed in all patients. Catheter ablation at the right inferoparaseptum eliminated antegrade slow pathway conduction and rendered AVNRT noninducible in all patients. Conclusion: Selective elimination of the slow pathway conduction at the inferoparaseptal right atrium may suggest that the subatrial tissue linking the retrograde fast and antegrade slow pathways forms the upper common pathway in AVNRT with VA block. [source] Exact Location of the Branching Bundle in the Living HeartPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2009MASAMITSU ADACHI M.D., Ph.D. Aims: The His bundle electrogram is believed to reflect the exact location of the His bundle. However, the distinction between distal His bundle potential and proximal right bundle branch potential is challenging. The aim of this study was to pinpoint the location of the branching point of the His bundle, and to compare that site with the site of recording of the largest His bundle electrogram (LH) during sinus rhythm. Methods: We hypothesized that the site of earliest His activation (EH) during retrograde conduction via the left bundle branch is the branching point. We studied 15 nonconsecutive patients (mean age = 40 ± 22 years; eight men). We performed a programmed stimulation from right ventricular apex until retrograde right bundle branch block appeared. At that point we measured (1) the distance between antegrade LH site and retrograde EH site and (2) the atrial-to-ventricular amplitude ratio (A/V ratio) at both sites. Results: EH was recorded at the proximal electrode of the His bundle catheter in all patients. Mean distance between EH and LH was 9.8 ± 2.5 mm. The mean A/V ratios at the EH site and the LH site were 1.01 ± 0.42 and 0.08 ± 0.06, respectively. Discussion: This study showed that the EH site is located approximately 10-mm proximal to the LH site. The mean A/V ratio at the EH site during sinus rhythm is approximately 1.0. These observations suggest that the majority of His potentials reflect proximal right bundle activation. Before delivering radiofrequency energy in the para-Hisian area, attention should be paid to the presence of a His potential and to the A/V ratio, rather to the amplitude of the His electrogram. [source] Atrial Activation Occurring Immediately after Successful Cardioversion of Atrial FibrillationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2008ARTURO MARTÍN PEÑATO MOLINA M.D. Background and Objective: Electrical defibrillation is very effective in interrupting atrial fibrillation (AF). However, its mechanism is not completely understood. We report our observations in patients subjected to external electriocardioversion (ECV) of atrial fibrillation and contrast them with recent theories about defibrillation mechanism. Methods: In 13 consecutive patients transthoracic electrical cardioversion for AF was performed during an electrophysiological study (11 monophasic -200,360 J- and 9 biphasic shocks -50,150 J-). About 10,16 electrograms were obtained with multipolar catheters recording right atrium, coronary sinus, and right pulmonary artery. AF was defined by interelectrogram intervals and changing sequences among recordings, indicating complete lack of organization. We evaluated the presence of propagated activations immediately (<300 ms) after successful shocks (,1 discrete electrogram in all recordings). In unsuccessful shocks we evaluated changes in electrogram morphology (discrete/fragmented) and interelectrogram intervals before and after defibrillation. Results: About 16/20 shocks terminated AF. In 6/16 one or two cycles of atrial activation were recorded just after the shock and before AF ended. In 10/16 AF was interrupted immediately after the shock. 4/20 shocks did not interrupt the arrhythmia. After these shocks, transient organization of recorded activity with longer interelectrogram cycle length and disappearance of fragmented activity were transiently observed. Conclusion: Our clinical findings in atrial defibrillation in vivo reproduce experimental data that show myocardial activations early after successful direct current shocks. These observations suggest that successful defibrillation depends not only on the immediate effects of the shock, but also on transient effects on electrophysiological properties of the myocardium, capable of interrupting persistent or reinitiated activations. [source] Use of an Intracardiac Electrogram Eliminates the Need for a Surface ECG during Implantable Cardioverter-Defibrillator Follow-UpPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2007KEVIN A. MICHAEL M.B.Ch.B. Background:A surface electrocardiogram (SECG) for pacing threshold measurements during routine implantable cardioverter-defibrillator (ICD) follow-up can be cumbersome. This study evaluated the use of an intrathoracic far-field electrogram (EGM) derived between the Can and superior vena cava (SVC) electrode,the Leadless electrocardiogram (LLECG), in dual chamber ICDs in performing pacing threshold tests. Methods:The LLECG was evaluated prospectively during atrial and ventricular pacing threshold testing as a substudy of the Comparison of Empiric to Physician-Tailored Programming of Implantable Cardioverter-Defibrillators trial (EMPIRIC) in which dual chamber ICDs were implanted in 888 patients. Threshold tests were conducted at 1 volt by decrementing the pulse width. Follow-up at three months compared pacing thresholds measured using LLECG with those using Lead I of the surface ECG (SECG). The timesaving afforded by LLECG was assessed by a questionnaire. Results:The median threshold difference between LLECG and SECG measurements for both atrial (0.00 ms, P = 0.90) and ventricular (0.00 ms, P = 0.34) threshold tests were not significant. Ninety percent of atrial and ventricular threshold differences were bounded by ± 0.10 ms and ,0.10 to +0.04 ms, respectively. We found that 99% of atrial and ventricular thresholds tests at six and 12 months attempted using LLECG were successfully completed. The questionnaire indicated that 65% of healthcare professionals found LLECG to afford at least some timesaving during device follow-ups. Conclusion:Routine follow-up can be performed reliably and expeditiously in dual chamber Medtronic (Minneapolis, MN, USA) ICDs using LLECG alone, resulting in overall timesaving. [source] Activation Sequence Modification During Cardiac Resynchronization by Manipulation of Left Ventricular Epicardial Pacing Stimulus StrengthPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2007USHA B. TEDROW M.D. Background: Success of cardiac resynchronization therapy (CRT) depends on altering electrical ventricular activation (VA) to achieve mechanical benefit. That increases in stimulus strength (SS) can affect VA has been demonstrated previously in cardiomyopathy patients undergoing ablation. Objective: To determine whether increasing SS can alter VA during CRT. Methods: In 71 patients with CRT devices, left ventricle (LV) pacing was performed at escalating SS. Timing from pacing stimulus to right ventricular (RV) electrogram, ECG morphology, and maximal QRS duration on 12 lead ECG were recorded. Results: Demographics: Baseline QRS duration 153 ± 25 ms, ischemic cardiomyopathy 48%, ejection fraction 24%± 7%. With increased SS, conduction time from LV to right ventricle (RV) decreased from 125 ± 56 ms to 111 ± 59 ms (P = 0.006). QRS duration decreased from 212 ± 46 ms to 194 ± 42 ms (P = 0.0002). A marked change in QRS morphology occurred in 11/71 patients (15%). The RV ring was the anode in 6, while the RV coil was the anode in 5. Sites with change in QRS morphology showed decrease in conduction time from LV to RV from 110 ± 60 ms to 64 ± 68 ms (P = 0.04). Twelve patients (16%) had diaphragmatic stimulation with increased SS. Conclusions: Increasing LV SS reduces QRS duration and conduction time from LV to RV. Recognition of significant QRS morphology change is likely clinically important during LV threshold programming to avoid unintended VA change. [source] Atrial Electrogram Amplitude and Efficacy of Cavotricuspid Isthmus Ablation for Atrial FlutterPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2003MEHMET OZAYDIN Large atrial electrogram amplitudes recorded in the cavotricuspid isthmus (CTI) may reflect thick atrial musculature. For this reason, in patients with atrial flutter, the efficacy of an application of conventional radiofrequency energy may be related to the amplitude of the local atrial electrogram. In 100 consecutive patients (mean age 59 ± 13 years) with atrial flutter, contiguous applications of radiofrequency energy were delivered in the CTI. The criterion for complete CTI block was the presence of widely split double potentials (>110 ms) along the entire ablation line during pacing from the coronary sinus and posterolateral right atrium. The atrial electrogram amplitude was measured before and after applications of radiofrequency energy at sites of gaps in the ablation line. Complete CTI block was achieved in 90 (90%) of the 100 patients. The mean atrial electrogram amplitudes at gap sites where an application of radiofrequency energy did and did not result in complete block were 0.36 ± 0.42 and 0.67 ± 0.62 mV, respectively (P < 0.01). The positive and negative predictive values (for complete block) of a ,50% decrease in electrogram amplitude after an application of radiofrequency energy were 100% and 35%, respectively. The mean atrial electrogram amplitude is larger at CTI sites where complete isthmus block cannot be achieved with conventional radiofrequency energy. The efficacy of conventional radiofrequency ablation may be improved by identifying areas in the CTI where the voltage is relatively low. (PACE 2003; 26:1859,1863) [source] Temporal Changes in the Endocardial ST Segment During the Evolution of Myocardial Infarction in DogsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2002JONATHAN LESSICK LESSICK, J., et al.: Temporal Changes in the Endocardial ST Segment During the Evolution of Myocardial Infarction in Dogs. Acute coronary occlusion causes ST-segment elevation on the body surface ECG and on the epicardial electrogram in the territory supplied by that artery. The occurrence and significance of endocardial ST changes have not been studied. The NOGA electromechanical mapping was performed on eight anesthetized dogs at baseline, immediately after occlusion of the LAD, and again at 5 hours to assess regional changes in the ST segment. At 3 days and 4 weeks the ventricles were remapped for comparison. Regional unipolar ST-segment elevation was measured for each zone from NOGA maps at 0, 80, and 120 ms after the J point. ST segments rose immediately in the infarct zones, as demarcated by echocardiography, compared to remote zones, but by 3 days had dropped below, and at 4 weeks returned to baseline values. Immediately postocclusion, ST elevation at 120 ms best differentiated between normal versus abnormal echo scores (concordance = 0.80), probably by correcting for pressure induced ST elevation. In conclusion, acute endocardial ST-segment changes occur in the infarct zone in the dog, showing a distinctive temporal evolution. [source] Shock Coordinated with High Power of Morphology Electrogram Improves Defibrillation Success in Patients with Implantable Cardioverter DefibrillatorsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2002ALEXANDER BERKOWITSCH BERKOWITSCH, A., et al.: Shock Coordinated with High Power of Morphology Electrogram Improves Defibrillation Success in Patients with Implantable Cardioverter Defibrillators. Animal studies have suggested that the success of defibrillation may depend on the properties of VF waveform obtained from the morphology electrogram (ME) at the time of the shock. The reliable identification of depolarization events in the fibrillatory signal can be achieved using adaptive estimation of the instantaneous signal power (P). The aim of this study was to investigate if a high P of the ME (PME) was related to ventricular DFT and if the upslope in ME can be associated with the depolarization event. A total of 575 VF (mean duration 10 s) episodes recorded and stored during ICD implantation in 77 patients with ventricular arrhythmias were used for analysis. The DFT was defined using a double step-down test. The values of PME immediately before pulse delivery (Pshock) and shock outcomes were registered. The differences between Pshock of successful and failed defibrillation were tested with the Mann-Whitney U test. The relationship between individual medians of Pshock (Pmed) and DFT was analyzed using the Kruskall-Wallis H-test. The coincidence between identified depolarization and upslope in ME was tested using the chi-square test. A P value of 0.05 was set for an error probability. The Pshock in case of failed defibrillation was significantly lower than Pshock in successful cases by the pulses of any strength (P < 0.001). The test revealed a significant inverse correlation between Pmed and DFT with P < 0.001. The depolarization corresponded to the upslope of ME in 85% of cases. This study demonstrated that a high value of instantaneous power of ME indicates the optimal time for shock delivery. The implementation of this algorithm in ICDs may improve the defibrillation efficacy. [source] Atrial Activation Sequence During Junctional Tachycardia Induced by Thermal Stimulation of Koch's Triangle in Canine Blood-Perfused Atrioventricular Node PreparationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2002ATSUSHI IWASA IWASA, A., et al.: Atrial Activation Sequence During Junctional Tachycardia Induced by Thermal Stimulation of Koch's Triangle in Canine Blood-Perfused Atrioventricular Node Preparation. Junctional tachycardia is observed during radiofrequency ablation of the slow pathway. The authors investigated the atrial activation sequence during junctional tachycardia induced with thermal stimulation in canine blood-perfused atrioventricular node (AVN) preparation. The canine heart was isolated (n = 7) and cross-circulated with heparinized arterial blood of the support dog. The activation sequence in the region of Koch's triangle (15 × 21 mm) was determined by recording 48 unipolar electrograms. Atrial sites anterior to the coronary sinus ostium (site AN), close to the His-potential recording site (site N) and superior to site N (site F), were subjected to a continuous temperature rise from 38°C to 50°C with a heating probe. The temperature of the tissue adjacent to the heating site was monitored simultaneously. Junctional tachycardia at a rate of 92 ± 12 beats/min with the His potential preceding the atrial one in the His-bundle electrogram was induced during thermal stimulation at site AN (temperature 42.1°C ± 0.9°C) in all seven preparations, whereas junctional tachycardia was induced during stimulation at site N in one and at site F in none. In each case, the temperature rose only at the site of stimulation. The earliest activation site during junctional tachycardia induced by site AN stimulation was at the His-potential recording site in five preparations and the middle of Koch's triangle in the other two. After creating an obstacle between sites AN and N, atrial tachycardia at a rate of 85 ± 11 beats/min was induced during site AN stimulation. The earliest activation site during this tachycardia was site AN. Thus, junctional tachycardia induced by thermal stimulation was suggested to originate from the AN thermal stimulation site. The impulse from the stimulation site appeared to conduct via the posterior input to the compact AVN and junctional tachycardia was generated. When the posterior input was interrupted, atrial tachycardia was generated. [source] A Segmental Polynomial Model of Ventricular Electrograms as a Simple and Efficient Morphology Discriminator for Implantable DevicesANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2006Jeffrey L. Williams M.D. Background: The goal of this study is to construct a polynomial model of the ventricular electrogram (EGM) that faithfully reproduces the EGM and can be implemented in current, low computational power implantable devices. Such a model of ventricular EGMs is still lacking. Methods: New Zealand White rabbits underwent chronic implantation of pacemakers through a left thoracotomy approach. Unipolar ventricular EGMs sampled at a frequency of 1 kHz were stored digitally in 1-minute segments before and after intravenous injection of isoproterenol or procainamide. Each cardiac cycle was divided into a QR and an RQ segment which were modeled separately using a 6th order polynomial equation. Results: The 14 coefficients of each cardiac cycle were reproducible throughout the baseline recordings (r , 0.94, P < 0.002). Isoproterenol caused no changes in the coefficients of the QR segment but significantly altered all but one of the seven coefficients of the RQ segment (p6= 0.0039, p5= 0.017, p4= 0.00007, p3= 0.112, p2= 0.00016, p1= 0.0086, pa= 0.00003). Procainamide caused statistically significant changes in both QR segment (p6= 0.018, p5= 0.287, p4= 0.019, p3= 0.176, p2= 0.016, p1= 0.362, pa= 0.000044) and RQ segment (p6= 0.0028, p5= 0.036, p4= 0.002, p3= 0.058, p2= 0.022, p1= 0.718, pa= 0.0018) coefficients. Conclusion: Our data demonstrate the feasibility of a segmental polynomial equation that reproduces the phases of depolarization and repolarization of the rabbit EGM. This model is reproducible and demonstrates the expected changes with antiarrhythmic drug administration. If reproduced in humans, these findings can have wide applications in patients with implantable devices, ranging from morphologic discrimination of arrhythmias to early detection of metabolic derangements or drug effects. [source] Characteristics of Complex Fractionated Electrograms in Nonpulmonary Vein Ectopy Initiating Atrial Fibrillation/Atrial TachycardiaJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2009LI-WEI LO M.D. Background: Nonpulmonary vein (PV) ectopy initiating atrial fibrillation (AF)/atrial tachycardia (AT) is not uncommon in patients with AF. The relationship of complex fractionated atrial electrograms (CFAEs) and non-PV ectopy initiating AF/AT has not been assessed. We aimed to characterize the CFAEs in the non-PV ectopy initiating AF/AT. Methods: Twenty-three patients (age 53 ± 11 y/o, 19 males) who underwent a stepwise AF ablation with coexisting PV and non-PV ectopy initiating AF or AT were included. CFAE mapping was applied before and after the PV isolation in both atria by using a real-time NavX electroanatomic mapping system. A CFAE was defined as a fractionation interval (FI) of less than 120 ms over 8-second duration. A continuous CFAE (mostly, an FI < 50 ms) was defined as electrogram fractionation or repetitive rapid activity lasting for more than 8 seconds. Results: All patients (100%) with non-PV ectopy initiating AF or AT demonstrated corresponding continuous CFAEs at the firing foci. There was no significant difference in the FI among the PV ostial or non-PV atrial ectopy or other atrial CFAEs (54.1 ± 5.6, 58.3 ± 11.3, 52.8 ± 5.8 ms, P = 0.12). Ablation targeting those continuous CFAEs terminated the AF and AT and eliminated the non-PV ectopy in all patients (100%). During a follow-up of 7 months, 22% of the patients had an AF recurrence with PV reconnections. There was no recurrence of any ablated non-PV ectopy during the follow-up. Conclusion: The sites of the origin of the non-PV ectopies were at the same location as those of the atrial continuous CFAEs. Those non-PV foci were able to initiate and sustain AF/AT. By limited ablation targeting all atrial continuous CFAEs, the AF could be effectively eliminated. [source] Frequency Analysis of Atrial Electrograms Identifies Conduction Pathways from the Left to the Right Atrium During Atrial Fibrillation,Studies in Two Canine ModelsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2009KYUNGMOO RYU Ph.D. Studies of atrial fibrillation (AF) have demonstrated that a stable rhythm of very short cycle length in the left atrium (LA) can cause fibrillatory conduction in the rest of the atria. We tested the hypothesis that fast Fourier transform (FFT) analysis of atrial electrograms (AEGs) during this AF will rapidly and reliably identify LA-to-right atrium (RA) conduction pathway(s) generated by the driver. Methods and Results: During induced atrial tachyarrhythmias in the canine sterile pericarditis and rapid ventricular pacing-induced congestive heart failure models, 380,404 AEGs were recorded simultaneously from epicardial electrodes on both atria. FFT analysis of AEGs during AF demonstrated a dominant frequency peak in the LA (driver), and multiple frequency peaks in parts of the LA and the most of the RA. Conduction pathways from the LA driver to the RA varied from study-to-study. They were identified by the presence of multiple frequency peaks with one of the frequency peaks at the same frequency as the driver, and traveled (1) inferior to the inferior vena cava (IVC); (2) between the superior vena cava and the right superior pulmonary vein (RSPV); (3) between the RSPV and the right inferior pulmonary vein (RIPV); (4) between the RIPV and the IVC; and (5) via Bachmann's bundle. Conduction pathways identified by FFT analysis corresponded to the conduction pathways found in classical sequence of activation mapping. Computation time for FFT analysis for each AF episode took less than 5 minutes. Conclusion: FFT analysis allowed rapid and reliable detection of the LA-to-RA conduction pathways in AF generated by a stable and rapid LA driver. [source] Automatic 3D Mapping of Complex Fractionated Atrial Electrograms (CFAE) in Patients with Paroxysmal and Persistent Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2008JINJIN WU M.D. Background: Complex fractionated atrial electrograms (CFAE) are a possible target for atrial fibrillation (AF) ablation and can be visualized in three-dimensional (3D) mapping systems with specialized software. Objective: To use the new CFAE software of CartoXP® (Biosense Webster, Diamond Bar, CA, USA) for analysis of spatial distribution of CFAE in paroxysmal and persistent AF. Methods: We included 16 consecutive patients (6 females; mean 59.3 years) with AF (6 paroxysmal and 10 persistent) undergoing AF ablation. Carto maps of left atrium (LA) were reconstructed. Using the new CFAE software, the degree of local electrogram fractionation was displayed color-coded on the map surface. LA was divided into four regions: anterior wall, inferior wall, septum, and pulmonary veins (PV). The relationship among regions with CFAE visualized and CFAE ablation regions (persistent AF only) was analyzed retrospectively. Results: In paroxysmal and persistent AF, CFAE were observed in all four LA regions. In paroxysmal AF, the density of CFAE around the PV was significantly higher than in other regions (P < 0.05) and higher than in persistent AF (P < 0.05). In persistent AF, CFAE were evenly distributed all over the LA. Of 40 effective ablation sites with significant AF cycle length prolongation, 33 (82.5%) were judged retrospectively by CFAE map as CFAE sites. Conclusion: CFAE software can visualize the spatial distribution of CFAE in AF. CFAE in persistent AF were observed in more regions of LA compared to paroxysmal AF in which CFAE concentrated on the PV. Automatically detected CFAE match well with ablation sites targeted by operators. [source] Complex Fractionated Electrogram Distribution and Temporal Stability in Patients Undergoing Atrial Fibrillation AblationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2008JEAN-FRANÇOIS ROUX M.D. Background: Targeting of complex fractionated electrograms (CFEs) has been described as an approach for catheter ablation of atrial fibrillation (AF); however, the distribution and temporal stability of CFE regions remain poorly defined. Methods: In patients with persistent AF referred for ablation, we performed two consecutive left atrial (LA) CFE maps prior to AF ablation. Bipolar electrograms were acquired during AF, and the mean AF cycle length and electrogram voltage were automatically determined at each point. Sites with mean CL ,120 ms were considered CFE positive. The two maps were then compared qualitatively and quantitatively. Results: A total of 15 patients (93% male, age 56.1 ± 9.0 years) undergoing AF ablation were studied. The two maps were separated in time by 31 ± 10 minutes. There was no significant difference in the number of CFE-positive regions (12.3 ± 5.2 vs 11.3 ± 4.7; P = 0.06) between the maps. While CFEs were widely distributed within the LA, the PV/left atrial junction (73%) and left atrial appendage (77%) were most often CFE positive. The presence of CFEs at each region was concordant 78% of the time. There was a significant correlation between the two maps (r = 0.35 ± 0.21, range 0.1,0.84; P < 0.001) with a percent difference of 17.5 ± 9.4%. Conclusions: During persistent AF, most CFE regions are found in the vicinity of the PVs. There is a significant correlation between two CFE maps constructed 31 minutes apart, with 78% concordance of CFE sites. [source] Ablation of Posteroseptal and Left Posterior Accessory Pathways Guided by Left Atrium,Coronary Sinus Musculature Activation SequenceJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 7 2008RÓBERT PAP M.D. Introduction: While some posteroseptal and left posterior accessory pathways (APs) can be ablated on the tricuspid annulus or within the coronary venous system, others require a left-sided approach. "Fragmented" or double potentials are frequently recorded in the coronary sinus (CS), with a smaller, blunt component from left atrial (LA) myocardium, and a larger, sharp signal from the CS musculature. Methods and Results: Forty patients with posteroseptal or left posterior AP were included. The LA,CS activation sequence was determined at the earliest site during retrograde AP conduction. Eleven APs (27.5%) were ablated on the tricuspid annulus (right endocardial), 9 (22.5%) inside the coronary venous system (epicardial), and 20 (50%) on the mitral annulus (left endocardial). A "fragmented" or double "atrial" potential was recorded in all patients inside the CS at the earliest site during retrograde AP conduction. Sharp potential from the CS preceded the LA blunt component (sharp/blunt sequence) in all patients with an epicardial AP, and in 10 of 11 (91%) patients with a right endocardial AP. Therefore, 18 of 19 (95%) APs ablated by a right-sided approach produced this pattern. The reverse sequence (blunt/sharp) was recorded in 19 of 20 (95%) patients with a left endocardial AP. Conclusion: During retrograde AP conduction, the sequence of LA,CS musculature activation,as deduced from analysis of electrograms recorded at the earliest site inside the CS,can differentiate posteroseptal and left posterior APs that require left heart catheterization from those that can be eliminated by a totally venous approach. [source] State of the Art: Catheter Ablation of Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2008MATTHEW WRIGHT M.B.B.S., Ph.D. Curative treatment of atrial fibrillation with catheter ablation is now a legitimate option for a large number of patients. In the last decade a tremendous amount has been discovered about this fascinating arrhythmia, yet there is still much that is understood. A number of different ablation strategies have been used including pulmonary vein isolation, targeting of fractionated electrograms, compartmentalising the atria with linear lesions and various combinations and modifications of these lesion sets. The optimal ablation strategy for both paroxysmal and long-lasting persistent atrial fibrillation is unknown. In this review the possible mechanisms underlying atrial fibrillation are examined along with the current catheter ablation techniques used in the treatment atrial fibrillation. [source] An Acute Model for Atrial Fibrillation Arising from a Peripheral Atrial Site: Evidence for Primary and Secondary TriggersJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2008BENJAMIN J. SCHERLAG Ph.D. Background: We previously demonstrated that acetylcholine (Ach) injected into cardiac ganglionated plexi (GP) causes pulmonary vein (PV) ectopy initiating atrial fibrillation (AF). Objective: To determine the effects of Ach applied at non-PV sites. Methods: Overall, 54 dogs were anesthetized with Na-pentobarbital. A right and left thoracotomy allowed the placement of multielectrode catheters to record from the superior PVs, mid portion of the atrium and the atrial appendages (AA). A monophasic action potential (MAP) was recorded from the AA. Ach (1, 10, 100 mM) was applied sequentially to the AA. Results: In 19 of 26 animals, Ach 100 mM on the right (n = 15) or left (n = 4) AA induced focal, sustained AF (,10 minutes) with rapid regular firing (cycle length = 37 ± 7 ms) at the AA. A clamp with teeth placed across the AA caused arrest in the AA. However, AF was sustained only when PV sites adjacent to the GP manifested complex fractionated atrial electrograms (CFAE). Clamping the AA prior to Ach (100 mM) application resulted in focal AF arising at the PVs but not at the AA. When a clamp without teeth was applied prior to Ach application, no AF at either AA or PV site could be induced. Conclusion: Isolation of the focal AF at the AA (primary trigger) by clamping caused cessation of activity in the AA, but AF continued due to secondary triggers arising from PVs. The possible mechanism(s) responsible for these findings are discussed, and various ancillary experiments (n = 28) were added to help elucidate mechanisms. [source] Mechanism of Propensity to Atrial Fibrillation in Patients Undergoing Isthmus Ablation for Typical Atrial FlutterJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 2 2005HEMANTH RAMANNA M.D. Background: Patients undergoing isthmus ablation for atrial flutter (AFL) may reveal postablation atrial fibrillation (AF). The electrophysiological mechanism is unclear. In patients with idiopathic AF, enhanced spatial dispersion of right atrial refractoriness was the substrate for the initiation of AF. We hypothesize that dispersion of right atrial refractoriness in patients undergoing AFL ablation is the major cause of postablation AF. Methods: Consecutive patients (n = 42) undergoing isthmus ablation for typical AFL were included. Twelve right atrial unipolar electrograms were recorded. Inducibility of AF was assessed by a pacing protocol, starting with one extrastimulus, followed by more aggressive pacing until AF was induced. Mean fibrillatory intervals were used to assess local refractoriness of each recording site. Spatial dispersion of right atrial refractoriness was calculated as the coefficient of dispersion (CD-value: standard deviation of the mean of all local mean fibrillatory intervals as a percentage of the overall mean fibrillatory interval). A CD-value of 3.0 or less was defined as normal, whereas CD-value greater than 3.0 was considered enhanced dispersion. PES and refractoriness analysis were followed by isthmus ablation. Results: Of the 42 patients, 29 had CD-value of 3.0 or less. In these 29 patients, AF was induced with 1 extrastimulus in only 1 patient, with 2 extrastimuli in 4 patients and burst pacing was required to induce AF in 24 of these 29 patients. Prior to the procedure, 5 of 29 patients had AF episodes, after ablation 6 of 29 patients. Of the 42 patients, 13 had CD-value greater than 3.0, AF was induced with a single extrastimulus in 11 patients, with 2 extrastimuli in the remaining 2 patients. Of the 13 patients, 11 had AF episodes both before and after ablation (P < 0.001). Conclusion: Enhanced spatial dispersion of right atrial refractoriness may be the substrate for propensity to AF in patients with AFL. The substrate was associated with enhanced inducibility of atrial fibrillation. [source] | ||||||||||||||||||||||