bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Epimyocardial Pacing: Initial Experience with a New Bipolar, Steroid‐Elnting, High Impedance Lead Design
Authors: KARPAWICH PETER P. , STOKES KENNETH B. , PROCTOR KEITH , SCHALLHORN RICK , McVENES RICHARD , FACTKOR MATHEW
Published: July 2006

Epicardial pacing typically is associated with decreased pacing and sensing capabilities compared with the endocardial approach. Since endocardial pacing is neither appropriate nor possible in all instances, this study was conducted to evaluate a new concept in a chronic epimyocardial lead design in six 3‐month‐old growing dogs. The new bifurcated lead (Medtronic model 10401) is a low current drain, high impedance, steroid‐eluting, bipolar design. The implant is facilitated by a suture attached with an atraumatic needle. Twelve ventricular leads were implanted (2 per animal) and followed for 6 months with weekly analysis of pacing and sensing capabilities. Results at explant were compared with implant values. There were no significant differences between implant and explant in sensed R waves, or in the slew rate of the R wave in unipolar or bipolar modes. Lead impedances at explant remained high in both modes: bipolar, 1550 ± 223; unipolar, 1234 ± 262 Ω (P < 0.05). Chronic voltage (v) threshold at 0.5 msec showed no significant change from implant values during the study: unipolar, 0.4 ± 0.2 vs 0.7 ± 0.3; bipolar, 0.5 ± 0.4 vs 1 ± 0.5. Histologic evaluations of the electrode tissue interface demonstrated negligible fibrotic capsule formation. This study introduces a new, easily implanted, high impedance, low threshold, bipolar epimyocardial pacing lead design with excellent chronic pacing and sensing characteristics.
Treatment of Patients with Prior Exit Block Using a Novel Steroid‐Eluting Active Fixation Lead
Authors: CROSSLEY GEORGE H. , REYNOLDS DWIGHT , KAY G. NEAL , EERGUSON T. BRUGE , LAMAS GERVASIO , MESSENGER JOHN , ZMIJEWSKI ATT , BRINKER JEFEREY A. ,   for the MODEL 4068 INVESTIGATORS
Published: July 2006

An increased interest has developed in active fixation leads for several reasons. Exit block is an uncommon complication that is seen with both active and passive fixation leads. Exit block has not been a significant problem with passive fixation steroid‐eluting leads and has been treated with these leads. A new steroid‐eluting active fixation lead was examined for its performance in patients in whom exit block had previously occurred. The lead function was evaluated prospectively in 24 patients with a history of exit block (15 ventricular and 9 atrial). The results in patients with atrial exit block are encouraging with an average chronic stimulation threshold of 0.19 msecs at 2.5 volts. Results in the ventricle are less encouraging with 3 occurrences of recurrent exit block in 15 patients; however, the remaining patients had a good mean threshold of 0.21 ±0.11 msecs at 2.5 volts. There were a remarkable number of non–lead related complications suggesting that this is a substantially different group than routine implantations.
Bipolar Intramyocardial Electrogram From an Implanted Telemetric Pacemaker for the Diagnosis of Cardiac Allograft Rejection
Authors: BONNEFOY E. , NINET J. , ROBIN J. , LEROUX F. , BOISSONAT P. , BRULE P. , CHAMPSAUR G.
Published: July 2006

Noninvasive detection of acute cardiac allograft rejection remains a challenge. Analysis of the epicardial electrogram transmitted by unipolar telemetric pacemaker can be of help in the detection of rejection with myocytolysis but is hampered by extracardiac factors. Instead, the contribution of a bipolar pacemaker for this purpose was studied. The bipolar peak‐to‐peak amplitude of epicardial electrograms (BPPA) from 25 patients implanted with a bipolar pacemaker at the time of heart transplantation was measured at the time of endomyocardial biopsies. BPPA was expressed as a percent of the baseline value. A voltage drop of more than 10% was considered an indication of rejection. Of 118 biopsies, 80 were free of rejection and 38 showed mild to moderate rejection (Grade 1A = 12; Grade 1B = 17; Grade 2 or 3 = 9). The mean value of BPPA was less for grade 2 biopsies (86.4 ± 17%) than for biopsies with no or mild rejection (101.3 ± 14.3% for Grade 0, 101.4 ± 13.8% for Grade 1A, and 98.6 ± 18% in Grade 1; P < 0.05). Diagnostic concordance between BPPA measurement and biopsy results increased with the histological severity of rejection (Grade 1A = 1/12, Grade 1B = 5/17, Grade > 2 = 7/9). Acute rejection was diagnosed with a sensitivity of 34% for Grade 1A, 46% for Grade 1B, and 78% for rejection episodes with myocytolysis (Grade ≥ 2). Specificity remained approximately 90% for all histologic grades. Overshoot after treatment was regularly observed when rejection was associated with a BPPA decrease of more than 10% (8 of 9), however uncommon, if the corresponding BPPA values were < 10% (2 of 13). These results were obtained with a variability of < 4% with moderate exercise, fever, pericardial effusion, or cytomegalovirus infection. Analysis of the bipolar epicardial electrogram transmitted by the telemetric function of a pacemaker implanted at the time of transplantation allows the detection of Grades 2–3 rejection and the monitoring of treatment efficacy. The limitations encountered in the detection of lower grade rejections might be minimized with the use of multiple bipolar derivations.
Sinus Node Dysfunction After Orthotopic Heart Transplantation: The Vienna Experience 1987–1993
Authors: HEINZ GOTTFRIED , KRATOCHWILL CHRISTOPH , SCHMID SUSANNE , KREINER GERHARD , SIOSTRZONEK PETER , PACHER RICHARD , GRIMM MICHAEL , LAUFER GUNTHER , GÖSSINGER HEINZ
Published: July 2006

In the present study, the annual incidence of postoperative sinus node dysfunction and the type of sinus node abnormality after cardiac transplantation were followed over a 6½‐year period in 185 patients. Each year the sinus node function was systematically characterized by rhythm and corrected sinus node recovery time in a significant number of patients. Over the entire study period, there were 131 patients with normal sinus node function (corrected sinus node recovery time 318 ± 55 msec) while 54 patients had latent (n = 24, sinus rhythm, corrected sinus node recovery time 8,053 ± 2,198 msec) or manifest (n = 30, absence of sinus rhythm or pacemaker dependence) sinus node dysfunction. Twenty‐nine patients had pacemaker placement. The incidence of sinus node dysfunction declined in absolute terms and when indexed by the actual number of patients transplanted per year (index 1987: 38.5; 1998: 17.6; 1989: 23.2; 1990: 29.1; 1991: 10.4; 1992: 7.5; 1993: 2.2). Among those with sinus node dysfunction, the annual percentage of patients presenting with prolonged recovery time, escape rhythm, and those reverting back to sinus rhythm until discharge did not change significantly over the study period (P = 0.22). On multivariate analysis, only the date of transplantation was significantly associated with the occurrence of postoperative sinus node deficiency (P = 0.0007) while age of recipient (P = 0.85) or donor (P = 0.96), the type of cardioplegia used (P = 0.09) and ischemic time (P = 0.09) were insignificant. This decline in the annual incidence of sinus node dysfunction most probably may be interpreted in terms of improvements in management (learning curve). It is unclear which changes in particular are responsible for this development. In view of the lack of other significant associations, this might be an indication that operative trauma plays a role in the etiology of sinus node dysfunction after cardiac transplantation.
Analysis of Circadian Distribution of Premature Ventricular Contractions in Patients After Heart Transplantation
Authors: PIETRUCHA ARTUR , MATYSEK JERZY , PIWOWARSKA WIESŁAWA , MROCZEK‐CZERNECKA DANUTA , GACKOWSKI ANDRZEJ , STOBIERSKA BOŻENA , NESSLER JADWIGA , MUSIAŁEK PIOTR , DZIATKOWIAK ANTONI
Published: July 2006

The aim of our study was to analyze circadian distribution of premature ventricular contractions (PVC) and its coupling interval (CI) in patients after orthotopic heart transplantation (HTx). Forty‐two patients (5 females, 37 males) were monitored from 2 weeks to 5 years after HTx; 180 24‐hour Holter ECG studies were performed. All recordings were divided into two groups: group I, within 1 month after HTX; and group II, after 1 month. Patients with more than 250 PVC/24 hours were selected for distribution of PVC and CI evaluation. Conclusions: Ventricular arrhythmias occur frequently in patients after heart transplantation. In patients with high Lown scale arrhythmias low occurrence (< 250/24 hours) of PVC was frequently observed (IVa: 81.8%; IVb: 84.7%). Similar patterns of circadian distribution (CD) of PVC and CD of HR in denervated heart after HTx suggest the influence of circulating catecholamines on their occurrence.
Is the Ventricular Effective Refractory Period Different When Determined by Incremental Versus Decremental Scanning?: The Effect of Pacing Cycle Length, d‐Sotalol, and Levcromakalim
Authors: LEERSSEN HENDRIK M. , VOS MARC A. , den DULK KAREL , van der ZANDE JOLANDA , WELLENS HEIN J.
Published: July 2006

In tbe clinical setting, the ventricular effective refractory period (VERP) is determined by an 8‐beat drive train (S1S1), followed by a premature stimulus (S2), which is decremented in subsequent drive trains until capture is lost. Variation in intertrain pauses and capturing extra stimuli disturb steady‐state conditions and reduce reproducibility of values found for the VERP. To increase reproducibility, a protocol without intertrain pause and incremental scanning (IS) of S2 was developed. In anesthetized dogs with chronic AV block, determination of the VERP using IS and decremental scanning (DS) without intertrain pause was compared at 800 and 350 msec pacing cycle length (PCL). The measurements were repeated after the administration of d‐sotalol to lengthen the VERP and levcromakalim to shorten the VERP. The results showed no difference between IS and DS at both PCLs with or without medication. Recurrent and abrupt rate changes were avoided daring IS, making this the protocol of choice when induction of arrhythmias is to be avoided.
Frequency Dependent Effects of Class I Antiarrhythmic Agents Studied in Patients with Implanted Pacemakers
Authors: TAKANAKA CHIEI , LEE JONG KOOK , NONOKAWA MAKOTO , SUGIYAMA TSUYOSHI , YAME SEITARO
Published: July 2006

Use and frequency dependency are common properties of Class I antiarrhythmic agents, which block cardiac sodium channels in vitro. The purpose of this study was to examine the rate dependent effects of Class I agents on ventricular conduction in humans in a crossover fashion. Twelve patients with implanted pacemakers who required antiarrhythmic therapy were studied. Four Class I agents were administered as follows: lidocaine. 1 mg/kg bolus followed by 4 mg/min infusion; disopyramide, 1 mg/kg bolus followed by 0.02 mg/kg per hour; aprindine, 1 mg/kg bolus followed by 4 mg/min infusion; and flecainide, 100 mg/day orally for 1 week. Trains of ventricular test stimuli between 70–180 ppm were applied during stable VVI pacing at 60 ppm. QRS duration was determined using signal‐averaged as well as standard ECCs. Lidocaine produced significant QRS prolongation at rates > 110 ppm (3.0%± 1.4% at 120 ppm. P < 0.05; 7.2%± 1.8% at 180 ppm, P < 0.01). Aprindine, disopyramide. and flecainide produced significant QRS prolongation at rates as low as 70 ppm and in a frequency dependent manner: 12.7%± 1.5%, 9.6%± 1.6%, and 13.3%± 2.8% at 70 ppm, respectively, (P < 0.01); 21.6%± 0.6%, 14.7%± 2.4%, and 29.9%± 4.2% at 180 ppm, respectively, (P < 0.01). Time constants of the single exponential development of QRS prolongation when the pacing rate was abruptly increased to 150 ppm were 0.09 ± 0.02 sec for lidocaine, 5.1 ± 1.2 sec for aprindine, 8.1 ± 1.7 sec for disopyramide, and 11.9 ± 1.4 sec for flecainide. These findings indicate that therapeutic doses of Class I agents cause a rate dependent depression of ventricular conduction in humans that is comparable to their blocking effect on cardiac sodium channels.
Regular Ventricular Rhythms Before Conversion of Recent Onset Atrial Fibrillation to Sinus Rhythm
Authors: BOTTO G.L. , BONINI W. , BROFFONI T. , CAPPELLETTI G. , FALCONE C. , LOMBARDI R. , PAULESU A. , PEDRAGLIO E. , FERRARI G.
Published: July 2006

The incidence of fast atrial tachycardias with regular ventricular rhythm was assessed in a population of 243 patients with recent onset (< 72 hours) atrial fibrillation (AF), without heart failure, randomly treated with single loading oral dose of propafenone (600 mg), flecainide (300 mg), digoxin (1 mg), or placebo for acute conversion to sinus rhythm (SR). Fast atrial arrhythmias developed in 14 (6%) patients: 6/92 treated with propafenone, 3/34 treated with flecainide, 1/25 treated with digoxin, and 4/ 92 who received placebo (P = NS). Heart rate > 175 beats/min with 1:1 AV conduction ensued in 4 cases: 2 treated with flecainide and 2 treated with placebo; in the other cases 2:1 AV conduction was observed. Widening of QRS during regular tachycardia was observed in 4 patients; 3 who received propafenone and 1 who received flecainide. Conversion to SR within 4 hours was achieved in 55/92 (60%) patients treated with propafenone, 20/34 (59%) patients treated with flecainide, 7/25 (28%) patients treated with digoxin, and 19/92 (20%) treated with placebo (P < 0.001 propafenone vs placebo and flecainide vs placebo; P < 0.05 propafenone vs digoxin and flecainide vs digoxin). Periods of regular tachycardia are expected in recent onset AF and may not necessarily represent a proarrhythmic effect of Class 1C drugs, rather than mark the transition from AF to SR. Class 1C agents are probably responsible for widening of the QRS complex seen during these tachycardias. Propafenone and flecainide appear equally effective in converting recent onset AF.
Correlation of Signal‐Averaged P Wave with Electrophysiological Testing for Atrial Vulnerability in Strokes of Unexplained Etiology
Authors: GENCEL L. , POQUET F. , GOSSE P. , HAISSAGUERRE M. , MARGUS F.I. , CLEMENTY J.
Published: July 2006

Atrial fibrillation is considered the main cause of cardioembolic strokes. After detailed investigations, about 30% of ischemic strokes remain unexplained. A percentage of these ischemic attacks may result from asymptomatic episodes of paroxysmal atrial fibrillation (PAF). Previous studies have demonstrated that electrophysiological testing and signal‐averaged P wave (SAPW) ECG are useful to detect patients with PAF. Methods and Results: Twenty patients with unexplained ischemic strokes had electrophysiological studies (EPS) to determine atrial vulnerability and SAPW recordings. At EPS, patients were classified in group I (10 patients) if they had a latent atrial vulnerability index < 2 and/or more than 1 minute of sustained atrial arrhythmia. Otherwise they were classified in group II (10 patients). In group I, the filtered P wave duration was greater: 142 versus 120 msec (P = 0.03) and RMS 30 tended to he lower: 2.54 versus 4.13 μV (P = O.11) than in group II. A filtered P wave duration > 125 msec associated with a RMS 30 < 3 μV had a positive predictive value of 78% and a negative predictive value of 88% for the detection of patients with abnormal atrial vulnerability at EPS. Conclusions: SAPW may be useful to identify patients at risk of PAF who may be candidates for EPS.
Esophageal Balloon Electrode Catheter for Transthoracic Recording of His‐Bundle Potential with Transesophageal Atrial Pacing
Authors: HEINKE MATTHIAS , KÜHNERT HELMUT , VOLKMANN HANS , BUTKEWITZ FRANK , MÜLLER SIEGFRIED
Published: July 2006

To evaluate the influence of transesophageal atrial pacing of the transthoracic His potential identification, we combined signal‐averaged ECG with transesophageal atrial pacing with low threshold for pacing averaging ECG recording. A tripolar 10 French esophageal balloon electrode catheter, with one cylindrical electrode on the tip of the catheter and two balloon electrodes on the cardiac side of the catheter, used in 53 patients, allowed a painless transesophageal atrial pacing and a high signal to noise distance in the signal‐averaged ECG. Transesophageal atrial pacing allowed in 37 of 53 patients an identification of His potential by increasing the distance between the end of the atrial potential and the onset of the His potential in the pacing averaging ECG. The esophageal balloon electrode catheter allowed a painless transesophageal atrial pacing with low threshold for atrial capture during a long pacing time and a high signal to noise distance in the pacing averaging ECG. The increasing of the heart rate with transesophageal atrial pacing allowed the transthoracic identification of the His potential in the pacing averaging ECG.
Mechanisms of AV Node Reentrant Tachycardia in Young Patients With and Without Dual AV Node Physiology
Authors: SILKA MICHAEL J. , KRON JACK , HALPERIN BLAIR D. , McANULTY JOHN H.
Published: July 2006

Recent advances in electrophysiological mapping and radiofrequency catheter ablation have demonstrated the participation of perinodal atrial tissue or pathways in atrioventricular node reentrant tachycardia (AVNRT). Current concepts of the role of these pathways in the genesis of the various forms of AVNRT continue to evolve. In view of these recent advances, this study investigated the electrophysiology of AVNRT in young patients, and factors potentially associated with variant forms of this arrhythmia. Detailed programmed stimulation and catheter mapping were performed in 35 consecutive young patients with AVNRT. This group consisted of 15 male and 20 female patients, with a mean age of 12.1 ± 4.2 years (range 3–18 years). Of the 35 patients, 23 demonstrated dual AV node physiology, either in response to a critically timed extrastimulus (n = 17) or to rapid pacing (n = 6). The common form (antegrade slow‐retrograde fast) of AVNHT was demonstrated in 21 of these 23 patients. Antegrade fast‐retrograde slow (n = 1) and antegrade slow‐retrograde slow (n = 1) forms of AVNRT were identified in the 2 other patients. In contrast, only 5 of the 12 patients who did not demonstrate dual AV node physiology had the common form of AVNRT (P = 0.03). Eive of these patients also had the slow‐slow form of AVNRT, while 1 patient each had a fast‐slow and fast‐fast form of AVNRT. Patients with dual AV node physiology were older (14.2 ± 2.0 years) and more likely to be female (16 of 23) than patients in whom dual A V node physiology was not identified, where the mean age was 10.6 ± 4.2 years and only 4 of 12 patients were female (P = 0.02 for age and P = 0.07 for gender). These observations suggest that the physiology of AV node reentry may evolve as a function of age, with slow‐fast AVNRT prevalent in adolescents. However, absence of dual AV node physiology should not preclude diagnosis of AVNRT in young patients with supraventricular tachycardia, in whom atypical forms of AVNRT may be common.
Atrioventricular Nodal Physiology After Slow Pathway Ablation
Authors: TAKAHASHI ATSUSHI , IESAKA YOSHITO , IGAWA MASAYUKI , TOKUNAGA TAKESHI , AMEMIYA HIROSHI , FUJIWARA HIDEOMI , AONUMA KAZUTAKA , NOGAMI AKIHIKO , HIROE MIGHIAKI , MARUMO FUMIAKI , HIRAOKA MASAYASU
Published: July 2006

The A V nodal physiology before and 1 week after “slow pathway potential” guided catheter ablation was examined in 32 patients with AV nodal reentrant tachycardia. A mean of 4.9 applications of radiofrequency energy eliminated AV nodal reentrant tachycardia in all patients. There were no significant differences in sinus cycle length (815 ± 159 msec vs 813 ± 162 msec;P = NS) and fast pathway conduction properties before and 1 week after ablation. Slow pathway conduction was completely eliminated in 10 (31%) (group I) of 32 patients after ablation. In the remaining 22 patients residual slow pathway conduction associated with one AV node echo was observed. In 15 patients (47%) (group II), the effective refractory period of the slow pathway showed a change of < 30 msec (265 ± 51 vs 266 ± 51 msec; P = NS), and in 7 patients (22%) (group III), a prolongation of more than 80 msec (247 ± 56 vs 340 ± 42 msec; P = 0.0001) before and 1 week after ablation. Minimal and maximal A2‐H2 interval over the slow pathway in group II was not significantly changed (Min A2‐H2:241 ± 37 vs 247 ± 40 msec; P = NS, Max A2‐H2: 346 ± 79 vs 350 ± 60 msec; P = NS), while a significant prolongation was measured in group III (Min A2‐H2: 261 ± 53 VS 373 ± 107 msec; P < 0.01. Max A2‐H2: 359 ± 41 vs 427 ± 63 msec; P < 0.05) before and after ablation. Conclusion: In group II patients there was no evidence shown of impairment of the slow pathway. This suggests that disruption of the link between fast and slow pathways may be responsible for the elimination of AV nodal reentrant tachycardia, besides the elimination or impairment of the slow pathway itself, in “slow pathway potential” guided catheter ablation, and that the slow pathway potential may not necessarily represent activation of the slow pathway itself or of its atrial connection.
Radiofrequency Catheter Ablation and Modulation of Atrioventricular Conduction in Patients with Atrial Fibrillation
Authors: MENOZZI CARLO , BRIGNOLE MICHELE , GIANFRANCHI LORELLA , LOLLI GINO , ODDONE DANIELE , GAGGIOLI GERMANO , BOTTONI NIGOLA
Published: July 2006

We attempted radiofrequency ablation of the AV junction with a sequential right‐ and left‐sided approach in 78 patients affected by severely symptomatic, drug refractory atrial fibrillation. Stable third‐degree A V block was obtained in 99% of cases and, after 3 months, persisted in 92% of cases. Single session, stepwise, radiofrequency modulation of the AV node was attempted in 13 patients with paroxysmal atrial fibrillation. During sinus rhythm, ablation of the slow and fast AV node pathways was performed in order to increase the nodal refractory period or to slow conduction. Clinically successful modulation of AV conduction was achieved in 15% of cases and persisted during a 3‐month follow‐up. In conclusion. AV junction ablation is a well‐established means of treating atrial fibrillation, but implies the implant of a permanent pacemaker. AV node modulation avoids the pacemaker implant, but is efficacious only in a minority of patients. Thus, in patients affected by paroxysmal atrial fibrillation, AV modulation should be attempted first; if this is ineffective. AV ablation can be performed during the same session.
Long‐Term Survival After Closed‐Chest His‐Bundle Ablation with DC Shock for Supraventricular Arrhythmias: A 10‐Year Experience with 317 Consecutive Patients
Authors: POQUET FRANCK , GENCEL LAURENT , LEMETAYER PHILIPPE , HAISSACUERRE MICHEL , CLÉMENTY JACQUES
Published: July 2006

Survival after closed‐chest ablation of His bundle with DC shock for supraventricular arrhythmias was analyzed for a 10‐year period (May 1982‐December 1992) with 317 consecutive patients (167 males, 150 females; mean age 66 years; range 33–93 years). Of these, 54 patients died (17.3%) and 5 were lost to follow‐up. The mean age at ablation was 70.3 ± 8.3 years with a range of 49–93 years. Of those who died, the mean survival was 30.5 ± 28.6 months with a range of 36 hours to 120 months; the diagnosis of heart disease was; hypertension (n = 14), cardiomyopathy (n = 8), ischemic (n = 7), valvular (n = 6). Cor pulmonale (n = 3), valvular and ischemic (n = 2). hypertension and ischemic (n = 1), miscellaneous (n = 3), and none (n = 10). Of the patients who died after ablation, the arrhythmias at the time of the ablation were atrial fibrillation (AF; n = 33), sick sinus syndrome (n = 5), atrial flutter (AFL; n = 4), paroxysmal AV junctional tachycardia (PAVJT; n = 4), AF + AFL (n = 4), atrial tachycardia (n = 2). PAVJT + AFL (n = 1), and AF + AFL + atrial tachycardia (n = 1). Death was sudden in 13 patients (25%), due to heart failure in 10 (19.2%), myocardial infarction in 4 (7.7%), stroke in 4 (7.7%). aortic vascular accident in 3 (5.8%), miscellaneous in 18 (34.6%), and undetermined in 2. The overall survival rate was 94.5% at 1 year (n = 256), 80.1% at 5 years (n = 88), 72.8% at 8 years (n = 20), and 51% at 10 years (n = 4); patients with no underlying heart disease had a better survival. DC ablation of the His bundle was not associated with a high short‐ or long‐term mortality. This study may serve as a historical review with which to compare closed‐chest ablation of the His bundle with that of other energy sources such as radiofrequency energy.
Intraoperative Mapping is Not Necessary for VT Surgery
Authors: THAKUR RANJAN K. , GUIRAUDON GERARD M. , KLEIN GEORGE J. , YEE RAYMOND , GUIRAUDON COLLETTE M.
Published: July 2006

Surgical ablation of ventricular tachycardia is generally guided by the results of pre‐ and intraoperative cardiac mapping. However, in certain situations intraoperative cardiac mapping may not be possible and, therefore, surgery has to be based on information obtained preoperatively. This raises the question whether intraoperative mapping is necessary for the success of this approach. We describe our experience with encircling endocar‐dial cryoablation for ischemic VT and examine the contribution of intraoperative mapping for this procedure. Thirty‐three patients with inducibie VT refractory to medical therapy and a well defined anatomic scar were considered for surgery. All patients underwent baseline electrophysiology study and intraoperative mapping was attempted during normothermic cardiopulmonary bypass. In 14 patients, VT was inducibie intraoperatively (Group 1) and surgical ablation was guided by this information, whereasin 19patients, VT could not be mapped for various reasons (Group 2). Reasons for failure to obtain intraoperative map included noninducibility (3), nonsustained VT (8), polymorphic VT (4), VF (3), and incessant VT with hemodynamic collapse and cardiac arrest (1). The two groups did not differ with respect to age, location of myocardial infarction, or preoperative left ventricular ejection fraction. The operative procedures were similarin the twogroups with respect to aortic cross clamp time, cardiopulmonary bypass time, number of cryoablation lesions, concomitant revascularization, aneurysmectomy, and ICD implantation. Encircling endocardial cryoablation was performed in 32 patients and one patient underwent partial right ventricular free wall disconnection (RV infarct). Thirteen patients underwent concomitant coronary artery bypass grafting (5 in Group 1 and 8 in group 2). One patient had prophylactic ICD patches (Group 1). The mean LVEF pre‐ and postoperatively were similar in the two groups. One patient died postoperatively. Three patients had recurrent VT perioperatively: one patient was treated with amiodarone and two had an ICD implantation. During long‐term follow‐up (mean 5 years), survival was similar in the two groups. Conclusions: Encircling endocardial cryoablation for ventricular tachycardia is a useful surgical technique in selected patients. Preoperative cardiac mapping is useful in defining a surgical plan, but intraoperative mapping is not crucial to the success of encircling endocardial cryoablation.
Comparison of Signal‐Averaging Electrocardiographic Systems Using Device Specific Criteria in 104 Normal Subjects
Authors: MORENO FIDELA L. , KARAGOUNIS LABROS A. , VILLANUEVA TERESA , HORN SUSAN D. , ANDERSON JEFFREY L.
Published: July 2006

The advent of several signal‐averaged electrocardiogram (SAECG) systems for late potential (LP) assessment warrants comparisons to assess intersystem reproducibility and variability. Simultaneous SAECGs on two systems. Arrhythmia Research Technology (ART) and Marquette (MEI), were performed on 104 normal volunteers (53 males, age 44 ± 14 years), and analyzed filtered QRS duration (TEQRS), root mean square voltage (RMS40), and low amplitude signal duration (LAS40), filtered at 40–250 Hz. The Gomes criteria (TFQRS > 114 msec, RMS40 < 20 μV and LAS40 > 38 msec) were used as criteria for LP. The data was also analyzed using the recently proposed system specific criteria for MEI (TFQRS >120 msec, RMS40 <20 μV and LAS40 > 38 msec). Where appropriate, statistical analysis was performed using simple linear and Spearman's rank correlation, analysis of variance, Finn's R and cNemar's test. Results: The means ± SD for ART and MEI were: TFQRS: 97.2 ± 8.9 vs 108.2 ± 7.2 msec (R = 0.76), RMS40: 31.8 ± 17.8 vs 45.3 ± 19.9 μV (R = 0.53), and LAS40: 32.2 ± 8.4 vs 30 ± 7.4 (R = 0.54). When the Gomes criteria were applied, the number of subjects identified by each system as abnormal were: TFQRS = 3 vs 22 (P < 0.001), RMS 40 > = 20 vs 8 (P = 0.004), LAS40 = 21 vs 9 (P = 0.004), TFQRS/RMS40 = 3 vs 6 (P = 0.38), TFQRS/LAS40 = 3 vs 7 (P = 0.22), RMS40/LAS40 40 = 17 vs 8 (P = 0.02), and all three criteria = 3 vs 6 (P = 0.38) for ART vs MEI, respectively. Percent agreement was 81.7% for TFQRS and 84.6% for RMS40 and LAS40 when single criteria were applied. Agreement improved when combined criteria were utilized (87.5%–95.2% for any two criteria and 95.2% for all three criteria). The intersystem agreement that was not due to chance was 0.63–0.69 for single criteria and 0.75–0.90 for combined criteria. Disagreement was highly significant for the three criteria when used singly and for RMS40 and LAS40 combined. Disagreement was not significant when TFQRS was used in combination with ≥ one other criteria. When the MEI criteria were applied, there was a decrease in the number of subjects identified by the MEI system as abnormal, using the TFQRS criteria singly or in combination. Percent agreement for system specific TFQRS measurements was 94.2% for single criteria and 97.1% for combined criteria. The intersystem agreement that was not due to chance improved (88–0.94). Disagreement between system specific criteria for TFQRS was not significant (P > 0.05). Conclusion: Our data indicate that although there is a general correlation between ART and MEI measurements, variability is substantial, leading to significant differences when the criteria for LP are applied, especially for single parameter determinations. Thus, there is a need to establish system specific normal ranges and more accurate criteria for LP parameters.
High Resolution ECG and Left Ventricular Volume After Acute Myocardial Infarction
Authors: JUNG JENS , HEISEL ARMIN , ÖZBEK CEM , BAY WOLFGANG , STOLL HANS P. , SEN SEMI , ALEXANDER CHRISTOPH , SGHIEFFER HERMANN
Published: July 2006

The presence of ventricular late potentials (LPs) early after acute myocardial infarction (AMI) was recently reported to correlate with left ventricular dilatation subsequent to AMI. We assessed prospectively the relationship between LP (time domain) in the late phase of AMI and left ventricular end‐diastolic volume (EDV) measured by equilibrium radionuclide angiocardiography 4 weeks and 12 months after AMI. In 80 consecutive patients 4 weeks and 12 months after thrombolytic therapy for AMI, LP and EDV were deter mined (EDV1, EDV2). There was no significant correlation between QRS duration (r = 0.18), RMS40 (r = 0.08), or LAS40 (r = 0.1) and EDV1 or EDV2 in patients with or without LP at baseline. In both groups (patients with [n = 15] and without LP [n = 65]), EDVl and EDV2 were comparable (128 ± 32 mL vs 126 ± 35 mL; 114 ± 40 mL vs 117 ± 36 mL; P = NS). In addition, there was no significant difference between EDVl and EDV2 in patients who developed new LP (n = 6) or lost LP (n = 9) 12 months after AMI. In contrast to LP in the very early phase after AMI, there seems to be no significant correlation between the high resolution ECG in the late phase after thrombolytic therapy for AMI and left ventricular EDV.
The Effects of Intravenous Mexiletine on Spectra of the Signal‐Averaged ECG
Authors: ZALIUNAS REMIGIJUS , ZABIELA PETRAS , SLAPIKAS RIMVYDAS , VAINORAS ALFONSAS , PENTIOKINIENE DAIVA , LEVISAUSKIENE REGINA , BECHTOLD HEINRICH , MEYER ULRIKE
Published: July 2006

This study examined the effects of intravenous mexiletine on the time‐domain and spectrotemporal signal‐averaged ECG (SAECG). SAECGs were recorded in 60 postmyocardial infarction (MI) patients with more than 100 premature ventricular beats per hour, before and after a constant infusion of mexiletine, 7 mg/ kg, given over 1 hour. Spectrotemporal analysis was done on a fixed analyzed signal duration of QRS complex and ST segment of X, Y, and Z leads using a temporal window of rectangular type, measuring the signal content between 10–120 Hz. Intravenous mexiletine produced no significant change in the mean values of any of the time‐domain variables. However, mexiletine either increased or decreased the power density spectrum (PDS) and PDS ratio (40–120 Hz/25–120 Hz) of the SAECG. and in rare cases only did it not alter the spectra of the SAECG. When PDS ratio in lead Z decreased after mexiletine, it was usually higher at baseline in comparison with that when the PDS ratio increased, or vice versa. When the treatment with mexiletine was effective, PDS increased in comparison with that when the drug was ineffective, or vice versa. Not all ranges (10–120 Hz) of spectra of the SAECG, but only certain frequency bands (25–40 Hz in lead Z,P = 0.0253; 40–55 Hz in lead Y, P = 0.0096; 55–70 Hz in Xlead, P = 0.0018; and in lead Z, P = 0.0002; 70–85 Hz in lead X, P = 0.0025; and in lead Z, P = 0.0075, 85–100 Hz in lead X, P = 0.0033) were associated with mexiletine efficacy. However, PDS ratio changes after mexiletine did not correlate with drug efficacy as measured by Holter monitoring. These results might provide a new understanding relative to the role and impact of mexiletine therapy in post‐MI patients.
Autonomic Imbalance Assessed by Heart Rate Variability Analysis in Vasovagal Syncope
Authors: PRUVOT E. , VESIN J.M. , SCHLAEPFER J. , EROMER M. , KAPPENBERGER L.
Published: July 2006

In this prospective study, the autonomic modulation of the sinus node of 12 patients (mean age 28 ± 7 years) suffering from vasovagal syncope (VVS) was compared to that of 11 sex and age matched control patients (mean age 32 ± 4 years) by analysis of heart rate variability. Spectral indices (low frequency power [Plf], high frequency power [Phf], total power [Pt], sympathovagal balance [LF/HF]) and temporal indices, the mean of all coupling intervals between normal beats (mRR), the standard deviation about the mean (sdRR), the percentage of adjacent R to R intervals differing by more than 50 msec (pNN50), and the root mean square of variations in successive R to R intervals (rMSSD) were compared at baseline and during head‐up tilt between and within groups. Baseline results were similar in both groups. During tilt testing, comparison of results between groups revealed only significantly higher sdRR and rMSSD and lower LF/HF ratio in VVS patients. Within WS patients, comparison of temporal and spectral analysis between baseline and tilt showed a significant increase of most indices (Plf, Phf, Pt, sdRR, and rMSSD) but a comparable LF/HF ratio; in contrast, control patients exhibited only a significant increase of LF/ HF ratio. In conclusion. VVS patients who developed vasovagal syncope during head‐up tilt demonstrated a nonreciprocal modulation of the sinus node by the autonomic nervous system indicative of a pronounced physiological sympathetic surge along with a paradoxical vagal input to the cardiovascular system.
Intraindividual Reproducibility of Heart Rate Variability Before and During Postural Tilt in Patients with Syncope of Unknown Origin
Authors: VARDAS PANOS , KOGHIADAKIS GEORGE , ORFANAKIS ALEXANDROS , KALAITZAKIS MIGHAIL , MANIOS EMMANOUIL
Published: July 2006

Fast Fourier analysis (FFT) of heart rate may be used to characterize overall heart rate variability (HRV) as well as low (LF: 0.06–0.10 Hz) and high (HF: 0.15–0.40 Hz) frequency components, which are attributable to sympathetic and vagal influences. This study examined the reproducibility of the spectral characteristics of HRV before and during postural tilt in patients being evaluated for unexplained syncope. Twenty patients (14 men, age 55 ± 12 years) with a history of syncopal episodes underwent 2 tilt table tests (T1 and T2) 1 to 6 weeks apart. For purposes of analyses the patients were divided into 2 groups according to the results of tilt testing. In 11 patients (Group A: 7 men, mean age 53.5 ± 12 years) syncope was induced in 1 (5 patients) or both tilt tests. In the remaining 9 patients (Group R: 7 men, age 56.7 ± 14 years) syncope did not develop during either test. Spectral indexes (SI) of HRV were computed by FFT for 2‐minute segments derived from Holter recordings before and during 60° head‐up tilt. We compared the SI measured in the two tilt, tests during the following 2‐minute periods: P1, just before tilt at rest, in a supine position; P2, immediately after tilt; P3, just before the end of the tilt. Results: P1 and P2: There were no significant differences in SI between T1 and T2 for low frequencies, high frequencies, or total power in either Group. In Group A, LF at time of maximum tilt exposure (P3) tended to be slower during T2 than in T1 (5.58 ± 1.44 vs. 6.56 ± 1.11, P < 0.05). However, this difference primarily reflects the findings in the five patients in whom syncope did not occur during T2. When these 5 patients were excluded the LF were essentially identical (6.43 ± 0.97 vs 6.80 ± 1.30; P = NS). Conclusions: Spectral indexes of HRV before and during the early part of tilt testing are reproducible. The SI during the later part of the test are related to the patient's response. However, this response is not predictable on the basis of sympathetic or parasympathetic tone before or during the early part of the test.
The Effect of Exogenous Adenosine in Patients with Neurally‐Mediated Syncope and Sick Sinus Syndrome
Authors: BRIGNOLE MICHELE , MENOZZI CARLO , ALBONI PAOLO , ODDONE DANIELE , GIANFRANCHI LORELLA , GAGGIOLI GERMANO , LOLLI GINO , PAPARELLA NELLY
Published: July 2006

The effects of a 20‐mg IV, bolus of adenosine 5’triphosphate (ATP) on the heart rhythm was studied in 79 patients affected by neurally‐mediated syncope (26 cases) or sick sinus syndrome (22 cases) or both syndromes (31 cases) and in 31 healthy control subjects in order to examine the sensitivity of cardiac purinoceptors in such circumstances. During ATP infusion, the sinus cycle lengthened to > 2 seconds in no control, in 1 (4%) patient with neurally‐mediated syncope, in 5 (23%) patients with sick sinus syndrome, and in 13 (42%) patients with both neurally‐mediated and sick sinus syndromes (P = 0.01). Atrioventricular block occurred in 14 (45%) of controls, in 10 (38%) patients with neurally‐mediated syncope, in 4 (18%) patients with sick sinus syndrome, and in 13 (42%) patients with both neurally‐mediated syncope and sick sinus syndrome (n.s.). Thus, exogenous ATP exerts different effects on patients with neurally‐mediated syncope and patients with sick sinus syndrome. In fact, intrisic disease of the sinus node is necessary to modulate an abnormal adenosine‐mediated sinus arrest, whereas patients affected by neurally‐mediated syncope alone show a normal sensitivity to the drug administration. The effect of ATP on atrioventricular conduction is greater than that on sinus node and is of similar magnitude in patients and controls; thus the clinical meaning of ATP induced atrioventricular block remains uncertain.
Termination and Acceleration of Ventricular Tachycardia with Autodecremental Pacing, Burst Pacing, and Cardioversion in Patients with an Implantable Cardioverter Defibrillator
Authors: HAMMILL STEPHEN C. , PACKER DOUGLAS L. , STANTON MARSHALL S. , FETTER JOSEPH ,   MULTICENTER PCD INVESTIGATOR GROUP
Published: July 2006

This multicenter study reports the outcome of ventricular tachycardia (VT) therapy (conversion or acceleration) and the relationship to initial tachycardia cycle length and other clinical variables using an implantable device with the capability of autodecremental or burst pacing, Cardioversion, and defibrillation. The device was implanted in 444 patients (mean age 58 ± 15 years) with 1,240 episodes of VT induced with noninvasive programming and reported in a multicenter database. Only the first sequence attempted for conversion by pacing or Cardioversion was assessed, and Cardioversion energies were 0.2–5 J. Autodecremental pacing was used to treat 700 induced episodes of VT during titration of pacing therapies (57% converted and 12% accelerated), burst pacing to treat 357 episodes (49% converted and 11% accelerated), and Cardioversion to treat 183 episodes (82% converted and 4% accelerated). Cardioversion was the most effective treatment and had the lowest acceleration rate. Shorter VT cycle lengths were more likely to accelerate with burst pacing and longer VT cycle lengths to convert with both burst and autodecremental pacing. Patients with higher ejection fractions were more likely to convert with autodecremental and burst pacing. Use of Cardioversion, higher ejection fraction, absence of unrepaired aneurysm, longer VT cycle lengths, coronary artery disease, and use of autodecremental pacing predicted conversion. Lower ejection fraction and VT cycle lengths ± 300 msec predicted tachycardia acceleration.
Alternation of QRS Morphology and Effect of Radiofrequency Ablation in Idiopathic Ventricular Tachycardia
Authors: WASHIZUKA TAKASHI , AIZAWA YOSHIFUSA , CHINUSHI MASAOMI , NAITOH NAOKI , MIYAJIMA TAKEFUMI , KUSANO YORIKO , KITAZAWA HITOSHI , UCHIYAMA HIROHIDE , TAKAHASHI KAZUYOSHI , SHIBATA AKIRA , MIYAJIMA SEIICHI , SATOU MASAHITO
Published: July 2006

We performed electrophysiological studies in 13 patients with idiopathic VT and attempted radiofrequency (RF) catheter ablation in 4 of them.Results: VT was induced by programmed stimulation in all patients and the mean cycle length was 363 ± 58 msec. In 8 of 13 patients (62%), alternation of either the cycle length and/or morphology of VT was observed. Transient entrainment was achieved in all patients by rapid pacing from the right ventricular outflow tract so reentry was considered the underlying mechanism of VT. The site of earliest activation (EAS) during VT was located at the apicoposterior portion of the left ventricular septum and used as the target site for RF catheter ablation. Spikelike presystolic activity was detected 20–40 msec prior to the large deflection of the local electrogram in four patients. VT was terminated by a few seconds of RF current in all four patients, but subsequently new VTs with a slightly different morphology were induced in three of them and re‐mapping showed a shift of the EAS. After additional RF ablation at the new EAS, VT was no longer induced. No complication was noted and VT did not recur during a follow‐up period for a mean of 9.3 ± 5.2 months.Conclusion: RF catheter ablation seems useful and safe for idiopathic VT. The alternation of QRS morphology and the findings at the time of catheter ablation suggest that an alternative pathway or multiple exits may be present in some patients with idiopathic VT, because the change in VT morphology was associated with a shift of the EAS.
An Esophageal and Gastric Approach to Ventricular Pacing
Authors: COCHRANE DAVID J. , McENEANEY DAVID J. , DEMPSEY GEORGE J. , ANDERSON JOHN McC. , ADGEY A.A. JENNIFER
Published: July 2006

Using a unipolar esothoracic pacing system (where current passes from a point source positioned in the distal esophagus to a chest wall pad) and pulse duration of 50 msec, satisfactory 1:1 ventricular capture was obtained in57 (86%) of 66 patients, with a mean threshold current of 27.7 mA at an optimal depth of 40.3 cm from the lower lip. When the unipolar esothoracic and bipolar transesophageal ventricular pacing systems were compared, the bipolar system was associated with a lower success rate and higher threshold current. When unipolar esothoracic pacing and gastrothoracic pacing (where current passes from a point source positioned in the stomach to a chest wall pad) were compared in 23 patients with bradyarrhythmia, ventricular capture was achieved using gastrothoracic pacing in 22 patients (96%) and esothoracic pacing in 21 (91%): gastrothoracic pacing required less current (16.0 mA ± SD 7.2 vs25.8 mA± SD 8.6). Optimal ventricular capture occurred using a unipolar gastrothoracic pacing electrode inserted to an average depth of 44.3 cm together with a high impedance chest pad (250 Ω) placed in the fourth interspace at the left sternal edge, with 50‐msec current pulses and a mean threshold of 16.0 mA. Thus, using a gastroesophageal electrode system, ventricular pacing can be achieved successfully, and the availability of such a system could play a major role in resuscitation of patients from severe bradyarrhythmias.
Improved Spatial Resolution for Cardiac Mapping Using Current Source Density‐Based Electrode Arrays
Authors: PIEPER CARL F. , PACIFICO ANTONIO
Published: July 2006

The time of the minimum slope (i.e., the fastest negative deflection) in monopolar (MP) electrograms from normal hearts compares closely with time of phase 0 of the action potential in cells underlying the electrode, but poor rejection of far‐field activity may limit the utility ofMP electrode technology in dense arrays used for the study of ventricular tachycardia and fibrillation. The purpose of this study is to evaluate more myopic discrete bipolar (BP) and nondirectional, two‐dimensional current source density (CSD) based arrays for rejection of far‐field potentials and precision of activation time determination. Simultaneous recordings of the CSD, MP, and multiple BP electrograms were performed on normal dog epicardium. The time of the minimum slope in MP electrograms was compared to activation times in CSD and BP derivations using: (1) peak; (2) steepest slope; (3) zero crossing of the steepest sloping segment in either direction; and (4) waveform morphology. In vivo, CSD amplitude was reduced significantly more than MP and BP amplitudes by insertion of inert media between the heart and the electrodes. The time of the steepest slope in CSD electrograms designated activation times closest to the time of the minimum slope in MP electrograms (0.9 ± 1.3 msec). We conclude that CSD provides a nondirectional electrode system that accurately defines the time of local activation and possesses better spatial specificity than MP electrode systems and BP electrode systems having the same interelectrode distances.
QT Dispersion Does Not Predict Early Ventricular Fibrillation After Acute Myocardial Infarction
Authors: LEITCH JAMES , BASTA MAGDY , DOBSON ANNETTE
Published: July 2006

Ventricular arrhythmias may be associated with increased QT dispersion (difference between maximum and minimum QT on standard 12‐lead ECG). We performed a case control study to determine if QT dispersion on the admission ECG could predict early VF after acute myocardial infarction. The cases were 24 patients with acute myocardial infarction (14 inferior, 8 anterior, and 2 lateral) with VF within 12 hours of admission. There were 24 control patients without VF matched for site of infarction and ST segment score (sum of ST segment elevation). VF occurred a median of 153 minutes (interquartile range 93–245) after onset of chest pain and 33 minutes (range 7–104) after initial ECG. QT (399 ± 37 and 394 ± 37), QT corrected (440 ± 38 and 429 ± 29), and QT dispersion (68± 20 and 66 ± 27) were similar in patients and controls. By design, ST score was similar (11 ± 9 vs 9 ± 5 mV), although a good match could not be obtained for three patients with extreme ST elevation. Patients with VF presented to the hospital earlier after the onset of chest pain (median 95 min [range 65–188] compared to 150 min [range 80–270], P= 0.05) and had a lower serum sodium (138 ± 2.4 vs 140 ± 2.5, P = 0.05) than controls. Thus, QT interval and QT dispersion, measured on the presenting ECG, did not predict early VF after myocardial infarction.