bluuebunny/crossref_metadata_2025 huggingface dataset:
Standardized Informal Exercise Testing for Programming Rate Adaptive Pacemakers
Authors: HAYES DAVID L. , VON FELDT LINDA , HIGANO STUART T.
Published: July 2006

t is essential that patients with pacemakers capable of rate modulation undergo some form of exercise testing to assure appropriate rate modulation, Informal exercise testing is a reasonable and Jess expensive alternative to formal treadmill testing. Empiric adjustment of the rate response parameters by assessing the patient's rate response while walking at a self‐determined casual and brisk pace has been used. However, no normals exist to determine the appropriate rate response for a “casual” and “brisk” walk. Volunteers were tested with metronome‐guided casual and brisk walks in an effort to standardize the informal exercise and determine expected heart rate response for these levels of activity, Results of the metronome‐guided rate response in normal volunteers may be useful in determining the appropriate rate response for pacemaker patients when tested in such an informal manner.
What's the Price to be Paid for Rate Response: AV Sequential Versus Ventricular Pacing?
Authors: MARKEWITZ ANDREAS , HEMMER WOLFGANG
Published: July 2006

The purpose of this study was to compare the effects of atrioventricular (AV) sequential and ventricular pacing at rest and during exercise on parameters of left ventricular performance. Twenty‐five patients were studied by means of first pass radionuclide angiography. Pacing rates increased significantly (P < 0.001) during exercise in both pacing modes, resulting in a significant increase in the cardiac index (P < 0.001). Pulmonary transit times decreased significantly (P < 0.001) during exercise in both pacing modes with a significantly shorter pulmonary transit time for AV sequential pacing at rest (P < 0.01) and during exercise (P < 0.05), indicating impaired left ventricular function in ventricular pacing. Regional left ventricular wall movement deteriorated significantly during exercise in both pacing modes (P < 0.02), with a significantly worse performance during ventricular pacing at rest (P < 0.05) and during exercise (P < 0.05). Therefore, the price to be paid for rate response is a deterioration of regional wall movement. An additional loss of AV synchrony worsens the situation. It is concluded that rate modulated pacing requires preservation of AV coordination to optimize left ventricular performance.
Relationship Between Diastolic Mitral Regurgitation and PQ Intervals or Cardiac Function in Patients Implanted with DDD Pacemakers
Authors: ISHIKAWA TOSHIYUKI , KIMURA KAZUO , NIHEI TOYO , USUI TAKASHI , KASHIWAGI MASANOBU , ISHII MASAO
Published: July 2006

Diastolic mitral regurgitation (MR) is known to be induced by prolonging atrioventricular (AV) delay in patients implanted with a DDD pacemaker. We studied the relationship between diastolic MR and PQ intervals on cardiac function in 50 patients (71.3 ± 11.3 years old: mean ± SD), who had been implanted with DDD pacemakers. In 19 patients, prior to pacemaker implantation, pulmonary capillary wedge pressure (PCWP) was measured using a Swan‐Ganz catheter during AV sequential pacing with an AV delay of 0.165 seconds. Transmitrai blood flow was measured with pulsed Doppler echocardiography, while prolonging AV delay stepwise by 0.025 seconds from 0.065 seconds for about 5 minutes each. In nine patients, AV delay could not be prolonged enough due to occurrence of intrinsic AV conduction. In the other 41 patients, diastolic MR was induced by prolonging AV delay. The critical PQ intervals that induced diastolic MR ranged from 0.14 to 0.26 (0.23 ± 0.03) seconds. Four of five patients whose critical PQ intervals were 0.20 seconds or shorter had heart failure, while 36 patients whose critical PQ intervals were >0.20 seconds were free from signs and symptoms of heart failure. Their PCWPs were 2–27 (7.5 ± 5.1) mmHg. There was a significant negative correlation between the critical PQ intervals for the appearance of diastolic MR and PCWP during AV sequential pacing, which was performed prior to pacemaker implantation (r = ‐0.85, P < 0.001). It is suggested that the appearance of diastolic MR is determined mainly by PQ intervals and cardiac function. Measurement of the critical PQ intervals that induce diastolic MR may be useful in assessing cardiac function in patients implanted with DDD pacemakers.
Limitations of the Countershock Dose Response: A Study of Transthoracic Current
Authors: WESLEY ROBERT C. , MORGAN DENNIS , ZIMMERMAN DONALD
Published: July 2006

Dose response assessment of Countershock efficacy has been widely determined with respect to energy but not current. The purpose of this study was to examine the utility of the dose response method in a current‐based model of trunsthoracic defibrillalion (penlobarbital anesthetized dogs, n = 8). Ventricular fibrillation induction lasting 15 seconds was separated by 5‐minute intervals. Current defibrillation threshold (DFT: the lowest current that successfully defibrillated) was determined by decreasing current on successive trials. Energy DFT equaled the energy value of the corresponding current DFT. Subsequent data were expressed in normalized terms with each DFT assigned a normalized value of 1.00. Three shocks were delivered in random order at each of seven normalized current nodes (total of 21 shocks); 0.55, 0.70, 0.85, 1.00, 1.15, 1.30, and 2.00 × DFT (early testing). Randomization was repeated, and a second set of 21 trials were performed (late testing). Composite plots were made relating normalized current and energy to the percent successful defibrillation. The dose response expressed in normalized energy demonstrated an overall shift to the left compared to current. The difference was significant at every node value below the estimated DFT. Ninety percent of successful trials with respect to current and energy occurred at or above 0.85 DFT and 0.55 DFT, respectively. Significant changes in impedance occurred between early testing (60 ± 6 ohms) and late testing (47 ± 5 ohms), n = 8, mean ± SD. Current, compared to energy, is a more accurate parameter in the dose response assessment of transfhoracic defibrillation. This phenomenon is largely secondary to a time‐dependent fall in impedance that results in lower delivered voltage and energy for a fixed delivered current. Energy should not be used as a parameter of Countershock efficacy.
Implantable Cardioverter Defibrillator Implanted by Nonthoracotomy Approach: Initial Clinical Experience with the Redesigned Transvenous Lead System
Authors: MOORE STEPHEN L. , MALONEY JAMES D. , EDEL THOMAS B. , MCGUINN WM. P. , GOHN DOUGLAS , MORANT VICTOR A. , TROHMAN RICHARD , SIMMONS TONY W. , WILKOFF BRUCE L. , CASTLE LON W.
Published: July 2006

Standard implantation procedure for the implantable Cardioverter defibrillator (ICD) has traditionary required a thoracotomy approach. A newly revised nonthoracotomy defibrillator lead system that uses a single transvenous tripolar endocardial lead alone or in combination with a subcutaneous/submuscular patch lead was introduced into clinical trials in September, 1990. Fourteen patients requiring a Cardioverter defibrillafor for recurrent sustained ventricular tachycardia (eight patients) or aborted sudden cardiac death (six patients) were evaluated for implantation of this lead system. Primary successful lead system implantation was obtained in nine patients. The remaining five patients had unacceptably high defibrillation thresholds (DFTs) for implantation. One of the nine initially successful implants demonstrated unacceptable DFTs and cross‐talk inhibition from a permanent pacemaker necessitating removal of the nonthoracotomy lead system and replacement with a conventional lead system via thoracotomy. All remaining primary implanted patients experienced successful conversion of induced ventricular fibrillation prior to hospital discharge. Continued follow‐up and greater experience to confirm the durability and efficacy of the nonthoracotomy AICD lead system are needed.
Influence of Clinical Characteristics and Shock Occurrence on ICD Patient Outcome: A Multicenter Report
Authors: GROSS JAY N. , SONG SUSAN L. , BUCKINGHAM THOMAS , FURMAN SEYMOUR ,   THE BILITCH REGISTRY GROUP
Published: July 2006

Data on 1,281 patients from the Bilitch impIantabje cardioverter defibrillator (ICD) registry were reviewed to evaluate ICD patient characteristics and survival, and the impact of ICD shock occurrence on outcome. The mean ejection fraction was 34.3%; 78% had coronary disease, 471 patients had at least one shock thought to be appropriate, and 231 patients died. Causes of death included: arrhythmic (41%), nonarrhythmic cardiac (37%), and noncardiac (22%). Cumulative survival from all‐cause mortality at 1, 3, and 5 years was 89%, 76%, and 64%; survival from all‐cause cardiac death was 93%, 90%, and 76%; survival from arrhythmic death was 96%, 92%, and 87%. Patients who had received a shock had a trend towards a worse long‐term prognosis. Shock patients also had a small increase in the prevalence of coronary disease and a somewhat lower ejection fraction than the remainder of the population.
Ventricular and Atrial Defibrillation Using New Transvenous Tripolar and Bipolar Leads with 5 French Electrodes and 8 French Subcutaneous Catheters
Authors: SCOTT STEVEN , AGCORTI PETER , CALLAGHAN FRANK , ABELS DEBRA , BOVEJA BIRINDER
Published: July 2006

This study evaluated the use of new small fransvenous atrial and ventricular leads for converting atrial fibrillation (AF) and ventricular fibrillation (VF) in 10 adult male mongrel dogs. Five dogs (group A) received a right atrial “J” (AJ) and right ventricular (RV) active fixation tripolar lead, each consisting of a platinized platinum pacing tip, anode band, and braided defibrillalion electrode. The remaining five dogs (group B) received one bipolar R V lead and one tripolar AJ lead. The RV leads were implanted in the right ventricular upex (RVA) and the AJ leads were placed in the atrial appendage. Additionally all dogs received two 8 French subcutaneous defibrillulion catheters in the fifth and seventh intercostal spaces. Twenty asymmetric biphasic shocks consisting of five randomized voltage levels were used to convert VF in groups A and B. The bipolar RV lead (group B) had a significantly higher probability of success in converting VF than the tripolar RV lend (group A). In group A defibrillation thresholds for converting AF were obtained using two electrode configurations. No significant difference was observed between the two electrode configurations used to convert AF. Pacing and sensing thresholds were satisfactory for bipolar and tripolar lead configuration.
Is Defibrillation Testing Safe?
Authors: SINGER IGOR , van der LAKEN JACOBA , EDMONDS HARVEY L. , SLATER A. DAVID , AUSTIN ERLE , SHIELDS CHRISTOPHER B. , KUPERSMITH JOEL
Published: July 2006

Determination of defibrillation thresholds (DFTs) and implantable cardioverter defibrillalur (ICD) testing requires repeated inductions of ventricular fibrillation (VF) and defibrillation attempts using known energy outputs. Little is known about the individual and cumulative effects of repetitive brief episodes of VF and hypoperfusion on cerebral function. The potential clinical utility of quantitative electroencephalographic (QEEG) monitoring during intraoperative ICD testing, by using processed 19‐channel EEG (0.5–35 Hz bandwidth), was examined in ten anesthetized patients, five males and five females (mean age 62 ± 10 years), who underwent ICD implantation and testing. Ischemic QEEG patterns were defined as those with a 3 standard deviation increase (P < 0.01) in absolute delta (1.5–3.5 Hz) power persisting for ≥ 2.5 minutes. The majority (80%) of the VF episodes (70) were accompanied by QEEG “slowing” (doubling of the pre‐VF low frequency delta waves amplitude). All the patients (5/5) experiencing > 6 VF episodes showed a statistically significant increase in the low frequency amplitude. In contrast, this EEG abnormality was apparent in only one of five patients experiencing < 6 VF episodes. These results suggest a cumulative QEEG depression associated with ICD testing. QEEG may provide an objective means for establishing an individualized upper safe limit of DFT testing and the total number of induced VF episodes.
Does Reception of Appropriate Shocks from the Implantable Cardioverter Defibrillator Affect Survival?
Authors: TCHOU PATRICK , AXTELL KATHY , KEIM STEPHEN , ANDERSON ALFRED J. , TROUP PAUL , JAZAYERI MOHAMMAD , AVITALL BOAZ , AKHTAR MASOOD
Published: July 2006

The impluntable Cardioverter defibrillafor has become an important therapeutic modality for treatment of life‐threatening ventricular tachyarrhythmias. Recent reports have suggested that patients who receive appropriate shocks from this device have an inordinately high overall mortality, and questioned the extent of benefit these patients derive from the implant. This report analyzed the survival among 184 patients who received the implantable Cardioverter defibrillator to assess survival differences between patients who received appropriate shocks versus those who did not. At a mean follow‐up of 24 ± 18.7 months, 68 patients received an appropriate shock from their device while 116 did not receive an appropriate shock. Overall survival of the entire population was quite similar (o those published by others. There was no significant difference between overall survival of patients who received an appropriate shock versus those who did not. However, there was a statistically significant difference in sudden death mortality. The group of patients that received appropriate shocks included all five sudden deaths. This observation suggested that sudden death in this population was likely due to ventricular tachyarrhythmias rather than strictly bradycardia or asystole. The “benefit” of the device to the entire population was also assessed by estimating survival after receipt of the first appropriate shock. Using this approach, an estimated 10% of patients died without receiving an appropriate shock. In other words, ultimately, 90% of patients were expected to benefit from the device. This survival curve, which initiated only after receipt of the first appropriate shock was fairly similar to those estimated from conventional methods. Therefore, survival after receipt of an appropriate shock was comparable to overall survival and there was no significant difference between survival of patients who received appropriate shocks and those who did not.
Proarrhythmic Response to Antiarrhythmic Drug as a Risk Factor for Sudden Cardiac Death in Patients with Ischemic Heart Disease
Authors: TRUSZ‐GLUZA MARIA , GIEC LESZEK , DABROWSKI ANDRZEJ , KUCH JERZY , PASYK STANISLAW , PIWOWARSKA WIESTLAWA , PRACKA HALINA , SADOWSKI ZYGMUNT , WODNIECKI JAN
Published: July 2006

The prognostic significance of arrhythmogenicc response to an antiarrhythmic drug was studied. In 782 palients with ischemic heart disease (IHD) and frequent and/or complex ventricular premature boats (VPBs), 1,041 drug tests guided by 24‐hour Holter monitoring were conducted. The following drugs were assessed: beta blockers, disopyramide, mexiletine, amiodarone. Proarrhythmia was defined as: (1) > 4‐fold increase in VPBs, (2) > 10‐fold increase in repetitive forms, or (3) new occurrence of ventricular tachycardia or ventricular fibrillation (VT/VF). During a follow‐up of 1–49 months fmean 22) patients were treated with anfiarrhythmic drugs found to be safe in control Holter monitoring, Proarrhythmic effects were observed in 8.4% of patients. No drug was completely free of this type of reaction. In long‐term observation, cardiac death and sudden death occurred in 5.3 and 32 patients, respectively. With actuarial analysis (Kaplan‐Meier method, log‐rank test) there was a significant difference in cardiac death (P < 0.01) and sudden death rate (P < 0.05) of proarrhythmia (+) compared with proarrhythmia (‐) patients at 1 year (11% vs 4%, 7% vs 3%) and 3 years (24% vs 11%, 16% vs 7%). Proarrhythmic response was an independent risk factor apart from myocardial infarction, VT/VF, ejection fraction < 40% and QTc > 440 msec. Arrhythmogenic response to antiarrhythmic drugs seems to be en additional predictor of sudden death in IHD.
Low Energy Direct Current Ablation in Patients with the Wolff‐Parkinson‐White Syndrome: Clinical Outcome According to Accessory Pathway Location
Authors: LEMERY ROBERT , TALAJIC MARIO , ROY DENIS , COUTU BENOIT , LAVOIE LINDA , LAVALLÉE ERIC , CARTIER RICHARD
Published: July 2006

Forty‐five patients with (he Wolff‐Parkinson‐White syndrome underwent direct current (DC) ablation using a low energy power source (Cardiac Recorders). Anodal shocks of 10–40 joules were given to either a 6 French quadri polar catheter (Bard), a 7 French bipolar contoured catheter (Bard), or a 7 French deflectable catheter with a 4‐mm distal electrode (Mansfield). The indifferent electrode consisted of a large patch that was positioned under the left scapula. There were 26 males and 19 females, with a mean age of 34 years (range 9–67), Accessory pathways were located in the left free wall in 30 patients (67%) and were posteroseptal in 15 patients (33%). The shortest ventriculoatrial interval during mapping (89 ± 21 msec), the mean cumulative amount of energy per patient (322 ± 283 joules), and the mean CK‐MB rise (45 ± 30 units, normal 0–30 units) were not significantly different between both groups. Ablation was successful in 29/30 patients (97%) with a left free‐wall accessory pathway, and in 13/15 patients (87%) with a posteroseptal accessory pathway. All three patients with failure of ablation had multiple accessory pathways, and two of these patients had Ebstein's anomaly. Palients with left free‐wall and posteroseptal accessory pathways, respectively, differed significantly in terms of: total session time (4.1 ± 1 hours vs 5.3 ± 1.3, p = 0.0001), total procedure lime for ablation (2.6 ± 0.8 hours vs 3.2 ± 1.2, P = 0.02), and fluoroscopy time (46 ± 24 min vs 64 ± 29. P = 0.006). In 13 patients (29%) with a concealed accessory pathway, these variables were not significantly different from patients with overt preexcifation. In conclusion, low energy DC ablation can successfully ablate accessory pathways with a high success rate (93%). Procedure and fluoroscopy time are not related to the type of accessory pathway (overt vs concealed), but vary significantly according to accessory pathway location—left free‐wall accessory pathways require shorter sessions and minutes of fiuoroscopy for successful ablation.
Biomagnetic Noninvasive Localization of Accessory Pathways in Wolff‐Parkinson‐White Syndrome
Authors: WEISMULLER P. , ABRAHAM‐FUCHS K. , SCHNEIDER S. , RICHTER P. , KOCHS M. , EDRICH J. , HOMBACH V.
Published: July 2006

If was our purpose to assess the clinical relevance of noninvasive magnelocardio‐graphic localization of accessory pathways. Nine patients with Wolff‐Parkinson‐White (WPW) syndrome were Studied, For all of them the site of the accessory pathway was known from invasive catheter mapping. A 37‐SQUID (superconducting quantum interference device) sensor multichannel system (KRENIKONR) was used, allowing synchronous registration with all channels. The site of the eleclrophysiological activity at the beginning of the delta wave was determined. Magnetic resonance images of the heart were obtained to correlate the biomagnetically localized activity with the anatomy. Magnetocardiographic localization of the bypass tract corresponded with catheter mapping with a spatial difference of 0–5 cm, 1.8 cm on the average, compared to the results obtained by catheter mapping. Thus, magnetocardiography is a promising new method for noninvasive localization of accessory pathways in WPW patients. This may streamline further invasive procedures.
Acute and Chronic Hemodynamic Impact of Total Right Ventricular Disarticulation
Authors: DOIG J. COLIN , NIMKHEDKAR KISHORE , BOURKE JOHN P. , MCCOMB JANET M. , HILTON COLIN J. , FURNISS STEPHEN S. , CAMPBELL RONALD W.F.
Published: July 2006

Right ventricular disarticulation is a radical operation to control ventricular arrhythmias in patients with arrhythmogenic right ventricular dysplasia. This report describes the acute and chronic hemodynamic impact of the procedure based on our experience of five patients with life‐threatening arrhythmias unresponsive to medical therapy who have undergone total disarticulation of the right ventricle. Although all patients suffered acute postoperative hemodynamic problems, all survived and returned to an excellent functional class. Right ventricular disarticulation should be considered in patients with drug refractory ventricular tachycardias due to arrhvthmogenic right ventricular dysplasia when the arrhythmia either poses a life threat or results in chronic morbidity.
Transcoronary Atrioventricular Nodal Modification Using Microvascular Collagen
Authors: SNEDDON JAMES F. , LINKER NICHOLAS J. , O'NUNAIN SEAN , SIMPSON IAIN A. , CAMM A. JOHN , WARD DAVID E.
Published: July 2006

Surgical and catheter based techniques for atrioventricular (AV) nodal modification have recently been described. Similarly, transcoronary embolization for the treatment of arrhythmias has recently emerged as a potentially useful approach. This report reviews our experience of a novel technique using embolizafion of the AV node with an inert agent, cross‐linked collagen, for the treatment of AV nodal reentrant tachycardia. Three patients with refractory nodal tachycardia received 0.1–0.5 mL cross‐linked coJlagen (2 mg/mL) delivered via a catheter placed within the nodal artery. All developed transient complete AV block with subsequent recovery of conduction. Two patients have had no further tachycardia and were noninducible at restudy. One patient required electrical modification because of recurrent symptoms. One patient sustained a limited posterior infarct due to back‐spill of collagen into the distal right coronary artery. This novel technique provides an alternative approach to a cure for AV nodal tachycardia without producing long‐term heart block.
Lower Pacemaker in High Degree Atrioventricular Block is Modulated Electrotonically by Atrial Excitations
Authors: TAKAYANAGI KAN , INDUE TERUO , SAKAI YOSHIHIKO , MOROOKA SHIGENORI , TAKABATAKE YUTAKA
Published: July 2006

To see if the lower pacemaker in patients with atrioventricular (AV) block was modulated electrofonically by atrial excitation, we studied R‐R intervals in two groups of AV block patients using a phase response curve (PRC). Group f consisted of 20 patients with high degree AV block, including seven patients in whom complete AV block was transiently observed in the course of acute inferior myocardial infarction. Group II consisted of 19 parents with complete AV block. In every patient, PRC was obtained from the continuous electrocardiogram by plotting each R1‐R2 interval (response) on the ordinate as a function of the R1‐Px interval (phase, x = 1, 2 …) on the abscissa, In Group I, the R‐R interval was prolonged when the P wave fell in (he initial half of (he R‐R interval, and was abbreviated when the P wave fell in the later half of the cycle. In Group II, the fluctuation of the R‐R interval was minimum. In ten group I patients, with the improvement of the AV block, PRC became sharper and transition from prolongation to shortening occurred at shorter R‐P intervals. We conclude that, in Group I, lower pacemaker was modulated electrotonicalIy by atrial excitations through decreased electrical coupling along the AV node.
Transesophageal Echocardiographic Evaluation for Mural Thrombus Following Radiofrequency Catheter Ablation of Accessory Pathways
Authors: GOLI VASU D. , PRASAD RAJESH , HAMILTON KAREN , MOULTON KRIEGH P. , TYLER MAUREEN , LOGAN PAULA , LAZZARA RALPH , JACKMAN WARREN M.
Published: July 2006

Background: Catheter ablation of accessory pathways (APs) provides a definitive therapy for patients with Wolff‐Parkinson‐White Syndrome. The reported incidence of thrombus formation on ablation‐induced injuries with direct current shock varies from 0%‐20% in animal studies. The purpose of this study was to determine the prevalence of mural thrombus following catheter ablation with radiofrequency current of accessory pathways in humans. Methods and Results: Radiofrequency current (30–35 warts) was applied through a catheter electrode placed against the mitral or tricuspid annulus guided by catheter recordings of AP potentials. Transthoracic (TTE) and transesophageal echocardiography (TEE) were performed in 95 of 111 patients, at 18 ± 6 hours following catheter ablation. After ablation. no thrombus was identified at or near the ablation site in any patient. Two out of 95 patients had a mural thrombus at a remote site that was detected by TEE but not by TTE. No new wall motion abnormality was detected in any patient. No significant regurgitant valvular lesion was found in any patient. Conclusion: Intracardiac thrombus was not identified at the site of catheter ablation, possibly owing to the small lesions produced by radiofrequency energy and high blood flow normally present in those areas. However, patients may be at small risk for mural thrombus at a remote site from prolonged placement of catheters.
Diagnosis and Surgical Treatment of Tachycardias in Patients with Nodoventricular Fibers
Authors: BOCKERIA LEO A. , CHIGOGIDZE NICKOLAY A. , GOLUKHOVA ELENA Z. , ARTJUKHINA TATYANA V.
Published: July 2006

From May, 1982 to April, 1991 25 patients were examined and 23 had open heart surgery for tachycardia with nodoventricular fibers (NVF) participation. All patients suffered tachycardia for more than 5 years. Most patients had syncope. The patients had: true NVF tachycardia (11), atrioventricular node reentry tachycardia (5), orthodromic atrioventricular tachycardia (AVT) (5), and atrial flutter (1) all with passive propagation through NVF, pseudonodoventricular tachycardia (AVT with slow accessory pathways) two patients. In 18 out of the 23 who had surgery there were no signs of preexcitation or tachycardia events in the follow‐up period.
Demonstration of Right and Left Atrial Dissociation by Atrial Rapid Pacing or Extrastimulation During Fast‐Slow (Uncommon) Form of Atrioventricular Nodal Reentrant Tachycardia
Authors: SUZUKI FUMIO , HARADA TOMO‐O , KAWARA TOKUHIRO , TANAKA KAZUSHI , HIRAO KENZO , HIEJIMA KAZUMASA
Published: July 2006

Some recent works suggest that extranodal atrial fibers may form part of the reenlry circuit in the atrioventricular (AV) nodal reentrant tachycardia (AVNRT). This hypothesis is based on the fact that the perinodal dissection successfully abolished AVNRT while preserving intact AV conduction. Apart from the surgical success, the electrophysiological evidence supporting this hypothesis has not been demonstrated, especially in the uncommon (fast‐slow) form of AVNRT. We present some electrophysiological evidence suggesting atrial participation in eight patients with the fast‐slow form of AVNRT. During the tachycardia, rapid pacing or extrastimulation was done from the orifice of the coronary sinus (CS) and the right atrium (RA), while recording the electrograms of the CS and the low septal RA. In seven patients, right and left atrial dissociation was demonstrated during pacing from the RA, while in the remaining one this was demonstrated from the CS. The interatrial dissociation will be unlikely if the intranodal reentry circuit connects with the atria via a single upper common pathway. This suggests that the upper turnaround of the reentry circuit involves atrial tissue and that the extranodal accessory pathway with long conduction times may form the ascending limb of the circuit (atrionodal reentry). Alternatively, the reentry circuit is entirely intranodal and two or more connecting pathways are present between the atria and the circuit.
The Role of Catheter Ablation Techniques in the Treatment of Classic (Type 1) Atrial Flutter
Authors: SAOUDI NADIR , DERUMEAUX GENEVIÉVE , CRIBIER ALAIN , LETAC BRICE
Published: July 2006

Several attempts at circuit interruption of type 1 atrial flutter by means of surgical or catheter techniques have been published. We recently reported the results of a series of patients who underwent catheter fulguration of the low septal right atrium, with a mean follow‐up of almost 3 years. True electrophysiological success was observed in 7/14 patients (50%). Clinical success, defined as absence of symptoms, was observed in 8/14 (57%) in this patient population. No serious complications were encountered, but the potential risks of DC shock, and the experience that we gained in right atrial mapping using this approach, led us to reconsider the role of atrial DC ablation in these patients. Additional studies assessing the meaning of fragmented electrograms, and identification of one for of severall slow conduction areas of the reentrant circuit are ongoing.
Efficacy and Safety of Oral Sotalol in Early Infancy
Authors: TIPPLE MARION , SANDOR GEORGE
Published: July 2006

Sotalol, a nonselective β blocking agent with additional Class III activity has been shown to be extremely elective in the treatment of supraventricular tachycardias in adults and children. Little information is available on its use in infants. From August, 1985 to April, 1990, 18 infants, 2 months of age or less, were treated with oral sotalol for supraventricular arrhythmias. Their age ranged from a few hours to 2 months, mean 5 weeks, at the start of treatment. Weights were between 2.58–5 kg, mean 3.9 kg and dosage 2–4 mg/kg/24 hrs given in two equal doses, 12 hourly. Sixteen infants had structurally normal hearts, one had multiple cardiac rhabdo‐myomas, and one was postoperative Mustard procedure for transpostion of the great arteries. Thirteen of 18 infants had reentrant forms of supraventricular tachycardia, six of these had overt preexcitation. Two infants had chaotic atrial tachycardia, two atrial flutter, and one with ectopic atrial tachycardia. Previous antiarrhythmic therapy had been unsuccessful in 12 patients. All infants, except one with chaotic atrial tachycardia, were successfully controlled with sotalol. Ten infants discontinued therapy between the ages of 7 and 18 months as it was felt to be no longer necessary. Mean duration of treatment was 12.8 months. Three had recurrences of their arrhythmia and were again successfully controlled by sotalol. Mild sinus bradycardia occurred in all infants. No other side effects were noted. Sotalol is an effective, safe drug for the treatment of supraventricular tachycardias in early infancy.
Steroid‐Eluting Epicardial Leads in Pediatrics: Improved Epicardial Thresholds in the First Year
Authors: HAMILTON ROBERT , GOW ROBERT , BAHORIC BORIS , GRIFFITHS JEAN , FREEDOM ROBERT , WILLIAMS WILLIAM
Published: July 2006

From 1986 to 1991, we evaluated the clinical use of three new epicardial lead designs incorporating a steroid‐eluting electrode. Medtronic models SP2114 (bipolar high profile), 10320 (bipolar low profile), 10295A/4965 (unipolar low profile) steroid epicardial (SE) leads were used on either atrium or ventricle for a total of 21 lead placements in 17 patients. Energy thresholds (T) were calculated and compared with our most recent 16 nonsteroid epicardial (NE) Medtronic model 4951 lead implants for which T was available. SE leads demonstrated no acute T rise and continued T improvements at 1 year of follow‐up. We conclude that epicardial application of SE lead technology offers a major improvement in pacing lead function and potential pacemaker longevity over NE leads in pediatric patients in whom endocardial pacing is precluded by size or anatomy.
Paradoxic Embolism Due to Altered Hemodynamic Sequencing Following Transvenous Pacing
Authors: SILKA MICHAEL J , RICE MARY J
Published: July 2006

A young patient, who experienced a cerebral embolic event 30 days after transvenous pacemaker iead placement, is reported. This patient had previously been paced with an epicardial lead without evidence of right to left intracardiac shunt. However, hemodynamic evaluation post‐embolism demonstrated a marked temporal disparity of the pulmonary and systemic ventricles. This phasic divergence resulted in a brief reversal of right and left ventricular pressure ratios, and a paradoxic intracardiac shunt at a small ventricular septal defect. The potential for similar events in the presence of any defect of the atrial or ventricular septum mandates caution in the use of transvenous pacemaker leads in such patients.
Transvenous Cryoablation of the Bundle of His
Authors: GILLETTE PAUL C. , SWINDLE M. MICHAEL , THOMPSON ROBERT P. , CASE CHRISTOPHER L. ,   (with technical assistance of JOE ARMENIA, MARK HAROLD, and CHARLENE KERR)
Published: July 2006

Cardiac dysrhythmias are a prominent cause of morbidity and mortality. Pharmacological treatment is ineffective in a large number of patients and is associated with many serious side effects. Thus, direct treatment of cardiac arrhythmias has been used with increasing frequency. Each form of direct treatment, such as surgical ablation, DC catheter ablation, radiofrequency catheter ablation, laser catheter ablation suffer serious drawbacks. Thus, we investigated the utility of transvenous catheter cryoablation of the bundle of His in five miniature swine, 40–60 lbs. in weight. Complete atrioventricular block was produced in each animal during cryothermia and persisted for 1 hour of observation in four out of five swine. In the fifth animal, 2:1 atrioventricular block within the atrioventricular node persisted for 1 hour of observation. Morphological and histologic examination revealed no dysfunction of capillaries and myofibriles in the atrioventricular node and proximal bundle of His. This potential mode of transcatheter therapy deserves further investigation.
Long‐Term Functional Integrity of Atrial Leads
Authors: PARSONNET VICTOR , HESSELSON AARON B. , HARARI DAVID C.
Published: July 2006

The effectiveness and reliability of atrial leads has been questioned. We studied retrospectively, all atrial leads implanted at our center (n = 494; 438 Medtronic Model 6957J, 56 Medtronic Model 4512) over a 5‐year period ending December 31, 1987, to determine the frequency of atrial lead failure (pacing, sensing, or both) and the median duration of proper pacing and sensing function for each lead model studied. Eighty‐eight percent of the polyurethane atrial leads continued to function satisfactorily at 5 years, results somewhat better than those reported heretofore in the literature, as well as our own past results with a variety of different lead types. There were 29 failures of pacing, sensing, or both (6% of implants). The cumulative survival of the atrial leads at 5 years was 88%. Pacing and sensing survival were 91%± 2.4% and 88%± 2.9%, respectively. We conclude that the choice of pacing mode for a new pacemaker should be based solely on the clinical indication and not on the concern that atrial pacing and sensing will be unreliable.
A Three‐Dimensional Display for Cardiac Activation Mapping
Authors: MASSÉ STÉPHANE , SEVAPTSIDIS ELIAS , PARSON IAN D. , DOWNAR EUGENE
Published: July 2006

A three‐dimensional display is described that allows activation sequences from the epicardium and endocardium to be shown simultaneously on the same image. Three electrode arrays (epicardial sock, left ventricular balloon, right ventricular balloon) are represented in a three‐dimensional perspective by an array of dots that are intensified when activated. This arrangement requires fewer calculations and is easier to interpret than siiced‐isochronal maps but cannot represent a complete heart cycle in one image. The three‐dimensional display eliminates the distortion caused by two‐dimensional diagrams and facilitates activation correlation between electrode arrays. A standard, low cost microcomputer has been used to implement the activation display.
Antitachycardia Pacemaker Treatment of Postoperative Arrhythmias in Pediatric Patients
Authors: FUKUSHIGE JUNICHIRO , PORTER CO‐BURN J. , HAYES DAVID L. , MCGOON MICHAEL D. , OSBORN MICHAEL J. , VLIETSTRA RONALD E.
Published: July 2006

An automatic antitachycardia pulse generator (Intertach 262–12) was implanted in each of six pediatric patients (mean age, 10 years) with drug‐resistant and persistent postoperative supraventricular arrhythmias. Four had bradycardia‐tachycardia syndrome, two after a Mustard procedure for transposition of the great arteries, one after a Senning procedure for the same anomaly, and one after a Fontan procedure for univentricular heart with transposition of the great arteries. Of the two remaining patients, one had atrial flutter after a modified Fontan procedure for univentricular heart and one had intra‐atrial reentry tachycardia after a modified Fontan procedure for double‐outlet right ventricle with pulmonary stenosis. During a mean follow‐up interval of 31 months after implantation, pacemakers were activated on multiple occasions and functioned appropriately in all six patients. Complications necessitated six invasive interventions in three patients: erosion or infection of the system, adaptor fracture, and connector block fracture on one occasion each and lead dislodgment on three occasions. Four of the six patients continued to take drugs at the end of this study; however, all patients had their drug therapy reduced and one was taking digoxin only. The number of hospital admissions decreased after implantation. Despite a number of technical challenges, this newer multiprogrammable antitachycardia pacemaker appears to be a valuable addition to the treatment of refractory postoperative supraventricular tachyarrhythmias in pediafric patients.
The Initial Clinical Experience with an Implantable Cardioverter Defibrillator/ Antitachycardia Pacemaker
Authors: SINGER IGOR , AUSTIN ERLE , NASH WHITNEY , GILBO JENNIFER , KUPERSMITH JOEL
Published: July 2006

GuardianR antitachycardia pacing (ATP) 4210 is a third generation, multiprogrammable Cardioverter defibrillator undergoing Phase I clinical trials. The tiered response includes ATP, low energy cardioversion or defibrillation, and bradycardia support. Extensive telemetry is available, including an episode log and details of all episode events. Five patients underwent the implaniation of GuardianR ATP 4210 as part of a Phase I trial at the University of Louisville. Two of the five patients had multiple VT episodes that were reverted successfully using ATP pacing (slow VT) and defibrilIation (fast VT) and VF episodes, which resulted in defibrillation therapy over a follow‐up period of 6 to 8 months. Four of the five patients required brudycardia support for bradyarrhythmias unassociated with ATP therapy or defibrillation and one patient required bradycardia support postdefibrillutan therapy. The device design is microprocessor based and requires continuous interrogation of the microprocessor memory and checks of the validity of programmed parameters to continue its operation. When the safety check fails, the device is designed to shut down its antitachycardia and defibrillalor functions, This design feature has a potential for leaving the patient unprotected if the device shuts down. Modification of this feature is required to ensure the device's long‐term safety.
Physical and Dynamic Characteristics of DC Ablation in Relation to the Type of Energy Delivery and Catheter Design
Authors: LEMERY ROBERT , LAVALLEE ERIC , GIRARD ALAIN , MONTPETIT MICHEL
Published: July 2006

We evaluated and compared the in vitro characteristics of direct current ablation using high energy ablation (Hewlett‐Packard defibrillator) and a new form of low energy ablation (low energy ablation power supply, Cardiac Recorders, UK). Two new catheters with a large distal electrode have been recently introduced for catheter ablutian: a low energy 7F bipolar catheter (Bard) with a contoured distal electrode, and a 7F deflectable catheter with a 4‐mm tip (Mansfield). In vitro studies were carried out in a large tank filled with physiological saline while recording voltage, current, and pressure. High speed cinematography at 32,000 frames per second (Cordin, Utah) was done to assess the dynamic behavior of the vapor globe with both systems of energy delivery. We evaluated shocks of 50, 100, 150, 200, and 300 joules with the conventional system, and shocks of 10, 15, 20, 30, and 40 joules with the new system, and also compared the effects of varying catheter design with both systems of energy delivery. The conventional system using high energy showed significant arcing and increases in pressure. Low energy direct current ablation produces nonarcing shocks with 20 joules or Jess, and significantly Jess vapor globe and gas formation during arcing shocks, with a shorter duration of increase in pressure. This new system using low energy direct current may reduce the risk and complications reported with high energy ablations.
Two Phase Radiofrequency Catheter Ablation of Isolated Ventricular Endomyocardium
Authors: DESAI JAWAHAR M. , NYO HTAY , VERA ZAKAUDDIN , TESLUK HENRY
Published: July 2006

This report describes a two phase radiofrequency (TPRFJ energy source producing two radiofrequency sinusoidal voltages of similar frequency but different phase angles between three points of wire. When delivered through an orthogonal electrode catheter array (OECA) TPRF energy produces a square‐shaped lesion of the area covered by the five electrodes (0.8 cm2). The purposes of the study were: to create square‐shaped Jesions using TPRF energy; to compare the size of lesions created by single phase radiofrequency (SPRF) to that of TPRF energy; and to study the depth of such lesions and to create lesions of desired size by adjacent placement of the OECA using TPRF energy. Ablations were created in nine isolated bovine hearts using three power settings (10, 20, and 40 watts) and three pulse durations (5, 10, and 20 seconds). Pathological examination was performed to document the length, width, depth, and the microscopic changes of ablations. TPRF energy increases the size of lesion (P < 0.001) and utilizes less power (P < 0.008) at the same power setting and pulse duration compared to SPRF energy. This is possibly related to earlier rise in impedance with TPRF compared to SPRF ablations. The largest lesion for both SPRF (0.51 ± 0.08 cm2) and TPRF (1.03 ± 0.18 cm2) ablations were observed at 20 watts for 20 seconds. By adjacent placement of the OECA and TPRF energy desired size (6 cm2) lesions were created. There was no significant difference between the depth of SPRF versus TPRF ablations at comparable power setting and pulse duration. Pathological examination revealed the shape of lesions were elliptical or cross‐shaped for SPRF and square for TPRF ablations. Microscopic examination revealed coagulation necrosis, edema, and few necrotic cardiac muscle strands. Conclusions: TPRF energy can cause 1.2 cm2 lesions. TPRF compared to SPRF energy causes larger lesions but depth of lesions are not different than SPRF energy at the same power setting and pulse duration. By adjacent placement of OECA and TPRF energy desired size lesion can be created (6 cm2).
Recovery of Sinus Node Function after Pacemaker Implant for Sinus Node Disease Following Cardiac Transplantation
Authors: MARTÍ VICENS , BALLESTER MANEL , OTER RAMÓN , OBRADOR DAMIÀ , LUNA ANTONI BAYÉS‐DE
Published: July 2006

In a 4‐year interval, 3/55 (7.8%) heart transplant recipient developed (>4 weeks) severe sinus node dysfunction. An epicardia) ventricular pacemaker was implanted at 90, 40, and 38 days after operation. Follow‐up ranged from 7 to 20 months. In two of the three coses, failure of stimulation or sensing was detected at the 3rd and 4th month after pacemaker Implantation. Sinus rhythm reappeared in two of the three patients at the 2nd and 4th months after transplantation, Severe sinus node disease requiring pacemaker implantation can improve following the first 3 months after transplantation. Failure of stimulation or sensing may not be uncommon.
Diagnostic Value of Synchronized Transesophageal Atrial Pacing
Authors: MARINSKY GERMAN , RIMSA EDUARDAS , SILEIKIS VYTAUTAS , KAZAKEVICIUS TOMAS
Published: July 2006

Synchronized tronsesophageol atrial pacing (single and double extrastimili) was used in 137 patients with various tachycardias inducible by atrial pacing during transesophageal electrophysiologicalstudy (EPS). This pacing mode in five patients initiated atrioventriculur tachycardias with ipsilateral bundle branch block not seen when using other pacing modes. During the tachycardia, single or double extrastimuli caused ipsilateral bundle branch block disappearance in two patients with atrioventricular tachycardia, and changed AV activation ratio in one patient with atrioventricular functional reentrant tachycardia. This pacing mode causes very little discomfort, what is important in children, and enhances diagnostic abilities of transesophageal EPS. So, this pacing mode should be used routinely as one of the steps of transesophageal EPS.
Effects of Lidocaine on Defibrillation Threshold in the Pig: Evidence of Anesthesia Related Increase
Authors: NATALE ANDREA , JONES DOUGLAS L. , KIM YOU‐HO , KLEIN GEORGE J.
Published: July 2006

Some antiarrhythmic drugs may influence the ability of a shock to defibrillate a patient but the effect of lidocciine on defibrillation efficacy has been controversial, suggesting multiple influencing factors. We determined the effects of three doses of lidocaine on defibrillation thresholds, using single and sequential shocks, in 36 open chest halothane‐anesthetized pigs. An additional eight pigs were anesthetized with barbiturate and received the highest infusion regime of lidocaine. Shocks were delivered through three mesh electrodes sutured over the anterior right ventricle, posterior right ventricle, and lateral left ventricle for sequential pulse shocks and between a lateral right to a lateral left ventricular mesh electrode for single pulse shocks. Triplicate defibrillation thresholds (DFTs) were obtained before and after lidocaine (n = 32) or saline (n = 12) administration, either with halothane or barbiturate anesthesia. Lidocaine did not alter DFT at any dose with either the single pulse (control 17.4 ± 3.7 joules [J], highest dose of lidocaine 13.5 ± 1.7 J, P = NS) or sequential pulse shocks (control 7.6 ± 0.8 J, highest dose lidocaine 6.6 ± 0.7 J, P = NS), when halothane anesthesia was used. Similar results were obtained with lower doses. In contrast, lidocaine in pentobarbital anesthetized pigs produced a significant increase of the DFT with single (control 13.7 ± 1.9, during lidocaine 16.6 ± 3.1, P < 0.01) and sequential shocks (control 11.1 ± 2.2, during lidocaine 14.5 ± 3A, P < 0.01). Interaction between barbiturates and lidocaine, and/or pH may account for the inconsistency in previous studies and must be considered for animal and clinical experiments.
Complications Associated with Retained Pacemaker Leads
Authors: PARRY GARETH , GOUDEVENOS JOHN , JAMESON STUART , ADAMS PHILIP C. , GOLD RONALD G.
Published: July 2006

Retention of functionless pacemaker leads may occur following mechanical or infective problems (potentially or definitely infected) or after electrical failure of the lead. One hundred nineteen patients with a pacemaker lead for leads) retained between 1970 and 1990 were reviewed retrospectively. Lead retention after an intervention dictated by potential or definite infection of the pacing system resulted in complications in 27 of 53 patients (51%), which in 22 patients (42%) were major (septicemia, superior vena cava syndrome, and further surgery under general anesthesia for recurrent “infective” problems) including three deaths. Complications were less likely if lead retention occurred after electrical failure with three minor and two major (surgery under general anesthesia, superior vena cava syndrome) complications in 66 patients (P < 0.001). Bacteriology of swabs taken at the time of retention in the patients with potential or definite infection was unhelpful in predicting future complications: 8/18 patients (44%) whose swabs were negative had complications of which 5/18 (28%) were major. In our experience retention of functionless pacemaker leads after an intervention dictated by potential or definite infection of the pacing system, is associated with significant morbidity and mortality and should be avoided.