bluuebunny/crossref_metadata_2025 huggingface dataset:
Permanent Left Atrial Pacing with a Specifically Designed Coronary Sinus Lead
Authors: DAUBERT CLAUDE , LECLERCQ CHRISTOPHE , LE BRETON HERVÉ , GRAS DANIEL , PAVIN DOMINIQUE , POUVREAU YVES , VAN VEROOIJ PAUL , BAKELS NOUD , MABO PHILIPPE
Published: July 2006

This article reports the original use of a specifically designed coronary sinus (CS) lead for permanent left atrial (LA) pacing. The device is characterized by its distal end shape featuring a double 45° angulation. which ensures very close contact with the CS upper wall. The device was successfully implanted in 39 out of 40 patients (97.5%). The tip electrode was eventually positioned in the distal CS in 9 patients, in the middle CS in 21 patients, and close to the ostium in the proximal CS in 9 patients. The mean acute pacing threshold voltage was 0.9 ± 0.5 V with a mean impedance of 578 ± 144 Ω as measured in unipolar distal configuration at 0.5 ms pulse width (PW). The mean A wave amplitude was 3.5 ± 2.1 mV. Early lead dislodgment occurred only once (3%) when the tip electrode was placed in the distal or middle CS, but more often (4/9 cases) when it was placed in the proximal CS. After a mean follow‐up duration of 14 ± 8.5 months, 35 of the 39 successfully implanted leads (89.7%) were still functional in terms of LA pacing and sensing. The mean chronic pacing threshold voltage was 1.5 ± 0.8 V and the mean A wave amplitude was 2.7 ± 1.6 mV. There were no lead related complications. In conclusion, the device proved to be safe and highly effective for permanent LA pacing, provided the distal tip could be positioned in the distal or middle part of the CS.
Efficacy and Safety of a New Protocol for Continuous Infusion of Midazolam and Fentanyl and its Effects on Patient Distress During Electrophysiological Studies
Authors: KOVOOR PRAMESH , PORTER RAE , UTHER JOHN B. , ROSS DAVID L.
Published: July 2006

Electrophysiological studies are often distressing for patients. We devised a regime of continuous infusion of midazolam and fentanyl during electrophysiological studies without the presence of a specialist anaesthetist. The effects on key hemodynamic and respiratory variables and level of sedation were evaluated in detail in the first 775 patients. The safety of this practice was evaluated in 1,344 consecutive patients. Doses were calculated according to patients’ weight and age. A mean total dose of 26 mg of midazolam and 115 meg offentanyl were infused. Satisfactory sedation was achieved in 97% of patients. The mean duration of procedure was 188 ± 90 minutes. Complete amnesia of the procedure was obtained in 87% of patients. Sedation caused clinically insignificant changes in respiratory rate, oxygen saturation, end‐tidal CO2 and blood pressure. There were no major complications related to sedation. Upper airway obstruction, usually minor, occurred in 42% and some restlessness in 20% of sedated patients. The assistance of a specialist anesthetist was required in 0.3% of sedated patients for management of restlessness, hypoventilation, or obstructive sleep apnea. The amount of distress experienced by sedated patients (n = 775) was significantly less compared to a previous series of nonsedated patients (n = 775) undergoing electrophysiological studies (P < 0.001). The degree of distress experienced by patients during electrophysiological studies can be reduced significantly by sedation with intravenous midazolam and fentanyl. Continuous infusion is an efficient, safe, and effective way of administering midazolam and fentanyl.
The Combined Transvenous Implantation of Cardioverter Defibrillators and Permanent Pacemakers
Authors: MATTKE SOREN , MARKEWITZ ANDREAS , MÜLLER DIETER , GRÜNEWALD ANKE , FIEK MICHAEL , SCHMÖCKEL MICHAEL , HOFFMANN ELLEN , STEINBECK GERHARD
Published: July 2006

We developed criteria for implantation and programming of permanent endocardial pacemakers in patients with a nonthoracotomy ICD system. These criteria were prospectively used in 10 patients who recieved an ICD prior to (n = 5) or following (n = 5) implantation of a dual chamber (n = 6) or ventricular (n = 4) pacemaker with a unipolar (n = 4) or bipolar (n = 6) lead configuration. All patients were tested for interactions or malfunctions. Undersensing of ventricular fibrillation by the atrial sense amplifier and inadequate atrial pacing occurred in one patient with a unipolar dual chamber system programmed to AAIR but didn‘t impair ICD sensing. Transient or permanent loss of capture or sensing of the pacemaker was not observed after ICD shocks with the output programmed to double pulse width and voltage of stimulation threshold and the sensitivity to 50% of the detected R wave. One episode of transient reprogramming occurred without clinical consequences. One unipolar ventricular pacemaker lead had to be exchanged against a bipolar lead because of oversensing of the pacing artifact by the ICD. There was no failure of an ICD to detect ventricular arrhythmias due to inadequate pacemaker activity. During a follow‐up period of 21 ± 11 months, a total of 78 ventricular arrhythmias were effectively treated in six patients. Thus, a combined use of transvenous ICD and pacemaker is possible despite the close vicinity of pacing and defibrillations leads. Optimized programming different to the common settings is required. As interactions occurred only in unipolar pacemaker leads bipolar systems should be used in these patients.
Neurohumoral and Hemodynamic Mechanisms of Diuresis During Atrioventricular Nodal Reentrant Tachycardia
Authors: ABE HARUHIKO , NAGATOMO TOSHIHISA , KOBAYASHI HIDEYUKI , MIURA YASUSHI , ARAKI MASARU , KUROIWA AKIO , NAKASHIMA YASUHIDE
Published: July 2006

Thirty‐two consecutive patients with paroxysmal supraventricular tachycardias, with previously defined mechanisms of the tachycardias, were interviewed by noninvestigators about whether they experienced symptoms of diuresis during or at the termination of the tachycardias, to test the hypothesis that patients with AV nodal reentrant tachycardia would have a feeling of diuresis, polyuria, or both during or at the termination of the tachycardia. Twelve of the 13 patients with AV nodal reentrant tachycardia (92%), two of the 15 patients with AV reentrant tachycardia (13%), and one of the 4 patients with atrial flutter associated with 2:1 AV conduction (25%) felt diuresis during or at the termination of the tachycardias (AV nodal reentrant tachycardia vs other forms of tachycardia; P < 0.001). In 14 of the 32 patients, the right atrial pressure and plasma atrial natriuretic peptide (ANP) concentration were measured during both the tachycardias and sinus rhythm. The mean right atrial pressure during AV nodal reentrant tachycardia was significantly elevated compared to that during other forms of tachycardia (P < 0.01). The plasma ANP concentration during AV nodal reentrant tachycardia was also elevated significantly compared to that during other forms of tachycardias (P < O.OO1). There were no significant differences in the cycle lengths of the tachycardias, age, left atrial dimensions, or the left ventricular ejection fraction between the AV nodal reentrant tachycardia and the other forms of tachycardia. We concluded that the feeling of diuresis during or at the termination of tachycardia was a more common symptom in patients with AV nodal reentrant tachycardia. The higher secretion of plasma ANP from the right atrium might be involved in the mechanism of this symptom.
Procainamide Induced Change of the Width of the Zone of Entrainment and its Relation to the Inducibility of Reentrant Ventricular Tachycardia
Authors: AIZAWA YOSHIFUSA , TANABE YASUTAKA , NAITOH NAOKI , WASHIZUKA TAKASHI , SHIBATA AKIRA , JOSEPHSON MARK E.
Published: July 2006

Procainamide depresses conduction velocity and prolongs refractoriness in myocardium responsible for reentrant VT, but the mechanism by which the induction of VT is suppressed after procainamide administration remains to be determined. In the present study, the relationship between electrophysiological parameters and the noninducibility of VT was assessed during procainamide therapy with a special reference to the change of an excitable gap. Clinically documented monomorphic sustained VT was induced in 30 patients and, utilizing the phenomenon of transient entrainment. the zone of entrainment was measured as the difference between the cycle length of VTand the longest paced cycle length interrupting VT (block cycle length) which was determined as the paced cycle length decreased in steps of 10 ms, and used as an index of the excitable gap. The effective refractory period was measured at the pacing site and the paced QBS duration was used as an index of the global conduction time in the ventricle. The cycle length of VT, the block cycle length, and the width of the zone of entrainment were determined and compared between the responders and nonresponders. In 15 patients, these parameters were determined at the intermediate dose and related to subsequent noninducibility at the final dose. At the final doses of procainamide, VT was suppressed in 8 (26.7%) of 30 patients. However, the cycle length of VT, the block cycle length, and the width of the zone of entrainment were unable to predict the drug efficacy, i.e., noninducibility. The change in the effective refractory period at the pacing site or the width of the paced QRS duration was not different between the responders and nonresponders. Among the variables, only the width of the zone of entrainment showed a significant narrowing in the responders at the intermediate dose of procainamide, and it was smaller than that of the nonresponders. The significant narrowing of the width of the zone of entrainment was associated with the subsequent noninducibility of VT at the final dose. The present study showed that the baseline cycle length of VT, the block cycle length, the drug induced change of the effective refractory period, or the paced QRS duration was not a predictor of the noninducibility after procainamide administration. However, a significant narrowing of the width of the zone of entrainment at the intermediate dose was associated with the noninducibility of VT at the final dose.
Clinical Performance of Steroid‐Eluting Pacing Leads with 1.2‐mm2 Electrodes
Authors: DANILOVIC DEJAN , BREIVIK KJELL , HOFF PER IVAR , OHM OLE‐JØRGEN
Published: July 2006

To raise pacing impedance and reduce battery current drain, new tined steroid‐eluting leads were developed with 1.2‐mm2 hemispherical electrodes, instead of conventional 5–8 mm2. Twenty‐two unipolar J‐shaped atrial leads and 25 unipolar ventricular leads (models 4533 and 4033, respectively) were implanted in 33 consecutive patients and followed for a mean of 25 months (range 18–29). Handling characteristics of atrial leads were found favorable. The leads slipped easily into the right atrial appendage and were easy to position. Handling characteristics of ventricular leads were satisfying, but more efforts had to be applied to cross the tricuspid valve. Special care was taken to avoid perforation of the myocardium due to the small lead tip. Following implantation, four ventricular and one atrial lead exhibited instability of pacing thresholds that resolved spontaneously within 1–3 days of implantation. Except for this, no lead malfunctioned. The reoperation rate was zero. The mean electrogram amplitudes of 15 mV (ventricle) and 4 mV (atrium), and the mean chronic pacing threshold of 0.085 ms at 1.6 V (app. 0.43 Vat 0.5 ms) were comparable with the best values seen in the literature on passive fixation leads. The rest of the electrophysiological parameters were enhanced: mean pacing impedances were 984 Ω (acute) and 900 Ω (chronic), mean slew rates 3.26 V/s (ventricle) and 1.75 V/s (atrium), mean acute voltage threshold at 0.5 ms was 0.25 V, mean current and energy thresholds calculated at 0.5 ms were 260 μA and 32 nJ (acute) and 478 μA and 103 nJ (chronic). The electrical characteristics of these leads provide for increased pacemaker longevity in combination with substantial safety margins for pacing and sensing.
The Top Ten Fallacies of Nonsustained Ventricular Tachycardia
Authors: MARINCHAK ROGER A. , RIALS SETH J. , FILART ROLAND A. , KOWEY PETER R.
Published: July 2006

Nonsustained ventricular tachycardia (NSVT) continues to remain a subject of controversy. This is true despite a wealth of epidemiologic and basic/clinical laboratory findings that have accumulated during the past 2 decades. However, these data not only generate the impetus to conduct further research, but also provide compelling arguments against continued adherence to time honored precepts about NSVT that evolved since the inception of the “PVC Hypothesis,” although never substantiated by rigorous scientific inquiry. This paper discusses the “top ten” fallacies of NSVT and details the data that support abandonment of them.
Interaction Between Electronic Article Surveillance Systems and Implantable Defibrillators: Insights from a Fourth Generation ICD
Authors: MATHEW PHILIP , LEWIS CAROLYN , NECLIA JOHN , KROL RYSZARD B. , SAKSENA SANJEEV
Published: July 2006

We present a case report of an inappropriate discharge from a fourth generation implantable cardioverter defibrillator (ICD) as a result of exposure to electromagnetic interference. A 60‐year‐old man implanted with a Medtronic 7219D defibrillator experienced shocks without preceding symptoms while walking through an electronic surveillance system in a store. Though this has been reported, the mechanism of the interaction remains unexplained. The electrogram storage capabilities of this particular device enabled us to establish that this resulted from inappropriate sensing of the electromagnetic interference.
Ventricular Output Failure in a DDD Permanent Pacemaker Associated with Increased Atrial Output
Authors: SANTUCCI PETER A. , MITRA RAMAN L.
Published: July 2006

Previous reports have described the occurrence of ventricular autput failure in a permanent DDD pacemaker system related to an increase in the atrial output in the presence of low atrial lead impedance (Medtronic Synergyst®/Synergyst II®). This phenomenon is seen exclusively following atrial paced events and may potentially lead to significant bradyarrhythmia or ventricular asystole in a pacemaker dependent patient. We describe the occurrence of analogous behavior in a Medtronic Symbios® 7006 generator.
A Pitfall in Using Far‐Field Bipolar Electrograms in Arrhythmia Discrimination in a Patient with an Implantable Cardioverter Defibrillator
Authors: NAYAK HEMAL M. , TSAO LANA , SANTONI‐RUGIU FRANCESCO , GOMES J. ANTHONY , MEHTA DAVENDRA
Published: July 2006

Analysis of stored electrograms from bipolar far‐field electrodes is considered to be useful in differentiating supraventricular from ventricuiar arrhythmias. A case of inappropriate ICD shocks for sinus tachycardia is presented whereby successive shocks caused marked widening of the ventricuiar electrograms. Analysis of these stored electrograms, recorded from far‐field bipolar electrodes, gave the false impression of ventricuiar tachycardia. The widening was due to the current of injury effects, probably a consequence of the large amount of intervening myocardium between the bipoies. While analyzing recordings from far‐field bipolar electrodes is generally useful, it is not always reliable, for changes in electrogram morphoiogy, reiative to baseline rhythm, may result from other factors like current of injury.
Runaway in a Modern “Soft Top” Pacemaker
Authors: BETTS T.R. , THOMAS R.D. , HUBBARD W.N.
Published: July 2006

Although runaway pacemaker was a relatively common occurrence, modern pacemaker design has made it extremely rare. We report a case occurring with a modern “soft‐top” pacemaker that resuited from a loss of hermeticity. Although the different treatment options are discussed, the definitive maneuvre is explantation of the faulty pacemaker.
Underdetection of Ventricular Tachycardia Using a 40 ms Stability Criterion: Effect of Antiarrhythmic Therapy
Authors: LE FRANC PIERRE , KUŚ TERESA , VINET ALAIN , ROCQUE PIERRE , MOLIN FRANCK , COSTI PAOLO
Published: July 2006

Inappropriate shocks can complicate cardioverter defibrillator therapy. Among solutions proposed to avoid oversensing are algorithms to reduce inappropriate detection of atrial fibrillation (AF) or sinus tachycardia. In patients not on antiarrythmic drugs, an interval stability criterion of 40 ms has been validated with the Medtronic PCD to discriminate ventricular tachycardia (VT) from AF. With this algorithm, VT is considered stable if no interval varies from one of the three preceding in tervals by more than 40 ms. If an interval does not fulfill this criterion, the VT event counter is reset to zero. The aim of this study was to investigate the incidence of underdetection when this criterion is ap plied in patients treated with antiarrhythmic drugs. We studied 132 sustained monomorphic VTs induced in 42 patients during 101 electrophysiological studies (EPS). EPS were performed without treatment (group I. 24 patients, 44 VTs); on Class Ia drug (group II, 17 patients, 24 VTs); Class Ic drug (group III, 22 patients, 39 VTs); or sotalol (group IV, 17 patients, 25 VTs). The endocardial electrogram of all VT episodes was digitized and the stability algorithm was applied. The reset arrhythmias were distributed among no delay, small, moderate (<10 s) and important (>15 s) delay in VT detection. The relation be tween drug use and reset was analyzed. Beset was found in 86 (65%) of induced VTs. No difference in heart rate or induction mode was shown between reset and nonreset VTs. There was a significative asso ciation between drag use and reset probability (Chi2 significantly different, P < 0.05). In patients treated with Class Ic drugs, the probability of finding an important delay in VT detection was 12.5% versus 0% in nontreated patients or in patients treated with sotalol. We conclude that a stability criterion of 40 ms is probably safe in nontreated patients but should be used with caution in patients treated with antiarrhythmics, especially in the presence of Class Ic drags.
Value of Automatic Processing and Reliability of Stored Data in an Implanted Pacemaker: Initial Results in 59 Patients
Authors: LIMOUSIN MARCEL , CEROUX LAURENCE , NITZSCHE REMI , CAZEAU SERGE , PIOGER GUY , VICTOR JACQUES , POTY HERVE , PUGLISI ANDREA , RICCI RENATO
Published: July 2006

Stored data in implantable pacemakers have rarely been used as a diagnostic tool because of the complexity. Our group bas developed software called AIDA, providing an automatic interpretation of data stored in memories of the Chorus (ELA medical) pacemaker. We com pared the results of AIDA analysis to surface ECG Holter interpretation in 59 patients (age 75 ± 9 years). In 33 cases, neither AIDA nor the Holter found any anomaly. Eleven patients demonstrated episodes of supraventricular tachycardia (SVT), confirmed by AIDA in ten patients; AIDA failure was due to nonsustained episodes of SVT not inducing mode switch. Loss of atrial sensing, pacemaker‐mediated tachycar dia, and ventricular extrasystoles were detected by AIDA in ten patients. Traditional Holter missed three cases. This initial study confirms that stored pacemaker data, automatically interpreted can provide reli able information over a 24‐hour period.
Effects of Polarity on Defibrillation Thresholds Using a Biphasic Waveform in a Hot Can Electrode System
Authors: YAMANOUCHI YOSHIO , MOWREY KENT A. , NADZAM GEORGE R. , HILLS DONALD G. , KROLL MARK W. , BREWER JAMES E. , DONOHOO ANN M. , WILKOFF BRUCE L. , TCHOU PATRICK J.
Published: July 2006

The polarity of a monophasic and biphasic shocks have been reported to influence DFTs in some studies. The purpose of this study was to evaluate the effect of the first phase polarity on the DFTofa biphasic shock utilizing a nonthoracotomy “hot can” electrode configuration which had a 90‐μF capacitance. We tested the hypothesis that anodal first phase was more effective than cathodal ones for defibrillation using biphasic shocks in ten anesthetized pigs weighing 38.9 ± 3.9 kg. The lead system consisted of a right ventricular catheter electrode with a surface area of 2.7 cm2 and a left pectoral “hot can” electrode with 92.9 cm2 surface area. DFT was determined using a repeated “down‐up” technique. A shock was tested 10 seconds after initiation of ventricular fibrillation. The mean delivered energy at DFT was 11.2 ± 1.7 J when using the right ventricular apex electrode as the cathode and 11.3 ± 1.2 J (P = NS) when using it as the anode. The peak voltage at DFT was also not significantly different (529.0 ± 41.3 and 531.8 ± 28.6 V, respectively). We concluded that the first phase polarity of a biphasic shock used with a nonthoracotomy “hot can” electrode configuration did not affect DFT.
The Upper Link of Human Common Atrial Flutter Circuit Definition by Multiple Endocardial Recordings during Entrainment
Authors: ARRIBAS FERNANDO , LÓPEZ‐GIL MARÍA , COSÍO FRANCISCO G. , NÚÑEZ AMBROSIO
Published: July 2006

Common atrial flutter is due to a macroreentry circuit in the right atrium, but the cranial path of the circuit has not been defined. The objectives of this article are to determine the cranial turning point of flutter activation in relation to a hypothetic obstacle, the superior vena cava opening, by examining the changes in activation sequence produced by entrainment from different points. In 13 cases of common atrial flutter with typical counter‐clockwise right atrial circuits confirmed by endocardial mapping the atrium was paced from the high posterior and mid‐septal walls. Entrainment was confirmed by simultaneous recordings of 6–7 right atrial electrograms. Changes in sequence of electrograms from high septum and high anterolateral walls was sought. Electrogram sequence and morphology did not change with entrainment at the posterior wall with respect to the basal flutter or mid‐septal wall entrainment. Pacing “below” the superior vena cava did not advance the anterior wall electrogram in relation to the septal electrogram. These findings suppport the concept that common Putter activation turned around (cranial and anterior to) the superior vena cava opening, and not around the free end of a line of block below the superior vena cava in the posterior wall. Common atrial flutter activation rotates cranial (and anterior) to the superior vena cava opening, through the “right atrial roof” The line of functional block should span from inferior to superior vena cava openings.
Transcutaneous T Wave Shock: A Universal Method for Ventricular Fibrillation Induction
Authors: MAZER C. DAVID , GREENE MARY B. , MISALE PATRICK S. , NEWMAN DAVID , DORIAN PAUL
Published: July 2006

Our objective was to develop a universal noninvasive method for VF induction. ICD implantation requires VF induction. Conventional rapid ventricular stimulation may fail to induce VF. Some ICDs can deliver low energy shocks on the T wave to induce VF. We hypothesized that an external dual chamber pacemaker and an external defibrillator could be configured to allow reliable VF induction with any ICD system. A surface ECC signal was delivered to the atrial channel of an external dual chamber DDD pacemaker. The ‘AV’ delay was adjusted so that the ventricular output of the pacemaker was delivered to an external defibrillator synchronized to deliver 5–50 J. Twenty‐six patients at ICD implant or follow‐up had VF induced in native rhythm (sinus rhythm or atrial fibrillation), or during a ventricular pacing train (3–8 beats at cycle length 500–880 ms). VF was successfully induced in 14 of 25 (56%) patients in native rhythm; and in 16 of 17 (94%) patients during pacing (P = 0.013). VF induction success rate was 36% in native rhythm (31/86 attempts) and 88% during pacing (69/78 attempts) (P < 0.001). The ‘R’ to shock interval was 269 ± 31 ms in native rhythm and 257 ± 48 ms during pacing. Energy delivered from the external defibrillator was 19 ± 3 J in native rhythm and 21 ± 6 J during pacing. We concluded that VF induction by synchronizing a small external shock to the T wave is a fast, effective way to reliably ensure arrhythmia induction with any ICD at implant or follow‐up. This method is more successful during pacing than in sinus rhythm.
Relation Between Left Atrial Size and Secondary Atrial Arrhythmias After Successful Catheter Ablation of Common Atrial Flutter
Authors: FREY BERNHARD , KREINER GERHARD , BINDER THOMAS , HEINZ GOTTFRIED , BAUMGARTNER HELMUT , GÖSSINGER HEINZ D.
Published: July 2006

Catheter ablation ptovides an effective cure for patients with typical atrial flutter. However, these patients may have the potential to develop atrial tachyarrhythmias other than common atrial flutter. This study examines clinical and echocardiographic predictors for the occurrence of uncommon atrial flutter or atrial fibrillation after abolition of common atrial flutter. The study population comprised 17 patients (12 men, 5 women, age 32–74 years) who underwent successful radiofrequency catheter ablation of common atrial flutter. Common atrial flutter did not recur in any patient during a median follow‐up time of 8 (range 1–25) months. Within a median of 7 (range 1–223) days, however, symptomatic atrial tachyarrhythmias occurred in 8 of 17 patients (47%): uncommon atrial flutter (n = 4); atrial fibrillation (n = 3); and both uncommon atrial flutter and atrial fibrillation in one patient. Preablation left atrial volume was significantly larger in patients who developed secondary arrhythmias compared with patients who remained in sinus rhythm (57.9 ± 15.6 vs 43.7 ± 16.4 cm3, P < 0.05). Enlarged left atrial volume dichotomized at 51 cm3 independently predicted postablation atrial arrhythmias (x2=5.11, rel. risk = 5.3, P < 0.05). On Kaplan‐Meier analysis, time to occurrence of postablation atrial arrhythmias was significantly shorter in patietits with enlarged left atrium (P < 0.02). In conclusion, symptomatic uncommon atrial flutter and atrial fibrillation develops in a substantial proportion of patients after successful ablation of common atrial flutter. Out of a series of clinical and echocardiographic parameters, preablation left atrial size is the best predictor for the occurrence of these postablation atrial arrhythmias.
Steroid‐Eluting Epicardial Pacing Electrodes: Six Year Experience of Pacing Thresholds in a Growing Pediatric Population
Authors: CUTLER NANCY GOLDMAN , KARPAWICH PETER P. , CAVITT DIANNE , HAKIMI MEHDI , WALTERS HENRY L.
Published: July 2006

Indications for pacemaker implantation in the pediatric population often include sinus or atrioventricular node dysfunction following surgery for congenital heart defects. However, patient size, cardiac defects, and vascular and valvular concerns may limit transvenous lead utilization. Since the epicardial surface of these patients often exhibits variable degrees of fibrosis from scar tissue formation or pericardial adhesions, chronic low output (2.5/1.6 V, 0.3 ms) epicardial pacing from implant is not currently recommended in children due to frequent threshold changes and electrode exit block. As a result, pacing in children is often viewed as a less efficient system than in adults. The addition of steroid combined with newer low threshold electrode designs however stabilizes the electrode‐tissue interface and eliminates postimplant changes seen with standard smooth surface electrodes potentially permitting efficient chronic pacemaker application to all patient ages. The stability of chronic low output epicardial pacing with steroid‐eluting electrodes was prospectively studied in 22 patients (ages 2 days‐18.5 years, median 3.5 years) for up to 6 years. Chronic pulse width thresholds were compared according to implant site and association of prior cardiac surgery. A total of 26 pacing leads were implanted. The acute implant mean pulse width threshold (2.5 V) for all the electrodes studied was 0.10 ms ± 0.05 ms. Stable low thresholds were maintained for up to 6 years without significant variation from implant. Mean ventricular pulse width thresholds (0.12 ms ± 0.05 ms) were significantly higher (P < 0.001) than atrial thresholds (0.06 ms ± 0.03 ms) at implant and throughout the study period. The thresholds in the patients following cardiac surgery were comparable to those without previous cardiac surgery (P = NS). Stable low thresholds may be chronically maintatined for up to 6 years for epicardial steroid‐eluting electrodes irrespective of pacing site or associated cardiac surgery.
Precipitous Exit Block with Epicardial Steroid‐Eluting Leads
Authors: BEDER STANLEY D. , KUEHL KAREN S. , HOPKINS RICHARD A. , TONDER LISA M. , MANS DAN R.
Published: July 2006

Between fanuary 1990 and October 1992, we implanted 16 steroid‐eluting ventricular epicardial pacing leads (Medtronic 10295A and 10295B/4965) in 12 patients. There were 8 males and 4 females ranging in age from 3 months to 49 years (mean 8.7 ± 13.2, median 6.0years). Structural cardiac disease was present in 11 of 12 patients. Follow‐up ranged from 3–73 months postimplant (mean 35.7 ± 22.3, median 28.5 months). Lead fracture (10295A) occurred in 1 of 12 patients. Of the remaining 11 patients, 8 of 11 have very low long‐term pacing thresholds. Unexpectedly, 3 patients demonstrated precipitous threshold increases from 3 months to 3.5 years postimplant. Although no deaths resulted in these exit block patients, 1 of 3 exit block patients developed marked worsening of congestive heart failure. We reviewed and analyzed the data obtained at 4 weeks postimplant for all of the 10295A and 4965 patients in the entire Medtronic clinical study database. Using the criterion of a 4 week postimplant pacing threshold ≥ 0.12 ms (5 V), we found that the long‐term risk of eventual exit block was 27.3% for the 10295A lead (P = 0.005) and 7.5% for the 10295B/4965 lead (P = 0.03). We, therefore, recommend that in patients implanted with the 4965 steroideluting epicardial lead, ventricular pacing thresholds ≥ 0.12 ms (5 V) measured at 4 weeks postimplant should prompt frequent threshold testing to detect late and potentially sudden ventricular pacing threshold increases.
The Importance of the Left Atrioventricular Interval during Atrioventricular Sequential Pacing
Authors: CHEVALIER STEPHAN , BASTA MAGDY , LEITCH JAMES W.
Published: July 2006

During atrioventricular (AV) sequential pacing from the right heart, the interval between the left atrium and ventricle may vary from the programmed AV interval depending on the position of the atrial and ventricular electrodes and interatrial and interventricular conduction. The aim of this study was to determine the hemodynamic effects of altering the left AV interval while keeping the programmed AV interval constant. Four male and 17 female patients, aged 49 ± 15 years were studied. The left AV interval was measured by a catheter in the coronary sinus. Stroke volume and mitral flow were measured by simultaneous echo Doppler during AV sequential pacing from the right atrial appendage and right ventricular apex at programmed AV intervals of 100. 60, and 6 ms. The atrial catheter was then positioned on the atrial septum and the measurements repeated. With the atrial catheter in the right atrial appendage, interatrial activation time (118 ± 20 ms) was similar to interventricular activation time (125 ± 21 ms) and the left AV interval was almost identical to the programmed right AV interval. There was a significant correlation between interatrial and interventricular activation times (r = 0.8; P < 0.001). Positioning the atrial electrode on the septum decreased interatrial activation time by 39 ± 12 ms and increased the left AV interval by a similar amount. At a programmed AV interval of 60 ms, the left AV interval increased from 67 ± 15 ms to 105 ± 17 ms after the atrial catheter was repositioned from the appendage to the septum (P < 0.001). Compared to pacing from the right atrial appendage, atrial septal pacing increased mitral A wave velocity integral (2.8 ± 1.4 vs 4.4 ±1.7 cm at a programmed AV interval of 60 ms, P < 0.01), decreased E wave velocity integral (8.1 ± 2.2 vs 6.1 ± 2.4 cm, P < 0.001) but did not alter stroke volume (44.8 ± 10.6 vs 44.9 ± 10.1 mL). In contrast, a 40 ms decrease in the programmed right AV interval from 100 to 60 ms decreased stroke volume from 48.0 ± 10.0 to 44.9 ± 10.2 mL (P < 0.001). There was a strong relationship between interatrial and interventricular conduction so that patients with prolonged interatrial conduction still had equivalent left and right AV intervals during atrioventricular sequential pacing from the right atrial appendage and right ventricular apex. Positioning the atrial electrode on the septum decreases interatrial activation time and increases the left AV interval by about 40 ms but has minimal hemodynamic effect in patients without heart failure.
Initial Clinical Experience with a New Small Sized Third‐Generation Implantable Cardioverter Defibrillator: Results of a Multicenter Study
Authors: FENELON GUILHERME , HUVELLE ETIENNE , BRUGADA PEDRO ,   EUROPEAN VENTAK MINI INVESTIGATOR GROUP
Published: July 2006

This study reports the acute clinical experience with the new CPI VENTAK MINI: a small sized (68 cc), implantable cardioverter defibrillator (ICD) with 33 J stored energy. Implantation of the device was attempted in 113 patients (90 men, mean age 57 ± 16 years, 64 with coronary artery disease, mean left ventricular ejection fraction 41%) with ventricular tachycardia or ventricular fibrillation (VF). All 113 patients (100%) were ultimately implanted, 12% of them for ICD replacement. Transvenous lead implantation was accomplished in all 104 patients (100%) receiving new leads, 95% of them with a single lead configuration. The safety criteria for implantation (2 consecutive VF conversions at 15 J or 3 at 20 J. in both cases without failures to convert) were demonstrated in all but 7 patients (6%). In 6 of these, safety criteria were not fully assessed while in the last patient defibriliation efficacy was not determined. Of the 104 patients with new leads, 90% underwent pectoral implantation. Of the 9 patients (9%) abdominally implanted, only 4 (4%) (3 children) were judged small sized for pectoral implant. At predischarge testing, reliable VF detection and conversion were noted in 96 of 97 patients tested. There was no perioperative mortality. At a 3.6 ± 1.3 months follow‐up, 34% of the patients had a spontaneous arrhythmic event, and 24% of the patients received shocks. Clinically inappropriate therapies occurred in 8% of the episodes in which any kind of therapy was delivered. This study demonstrates the short‐term clinical efficacy and safety of the new device, and that pectoral implantation can be performed in the large majority of patients.
Performance of Basic Ventricular Tachycardia Detection Algorithms in Implantable Cardioverter Defibrillators; Implications for Device Programming
Authors: ANDERSON MARK H. , MURGATROYD FRANCIS D. , HNATKOVA KATERINA , XIE BAIYAN , JONES SUSAN , ROWLAND EDWARD , WARD DAVID E. , CAMM A. JOHN , MALIK MAREK
Published: July 2006

Around 20% of patients with third generation implantable cardioverter defibrillators receive inappropriate therapy, usually triggered by atrial fibrillation. This is because the criteria used for ventricular tachycardia detection by current implantable cardioverter defibrillators are based on the analysis of a sequence of RR intervals and may be inappropriately satisfied by supraventricular tachyarrhythmias. Algorithms for ventricular tachycardia detection were challenged against the full RR interval sequences from 482 spontaneous episodes of atrial fibrillation and 260 spontaneous episodes of ventricular tachycardia to determine their ability to discriminate between the arrhythmias. The sensitivities and specificities of the algorithms were calculated over a wide range of programmable parameters. For a given window length and detection interval, the most stringent algorithms, that required all beats to be classified as “fast”, were more specific than those allowing a proportion of “normal” intervals, even after adjustment for differing sensitivity. These differences were less marked for faster tachycardias. Specificity increased with the detection window length to a limit of approximately 18 beats. We conclude that ventricular tachycardia is detected with the highest specificity if all beats in an analyzed sequence are required to be “fast” even after lengthening of the tachycardia detection interval to maintain sensitivity. Further improvement in algorithm performance may require the incorporation of criteria such as tachycardia onset and stability.
Implantation of Cardioverter Defibrillator and Pacemaker Using the Same Pectoral Quadrant
Authors: STRASBERG BORIS , ERDMAN SHIMSHON , KUSNIEC JAIRO , MAZUR ALEXANDER
Published: July 2006

We implanted a cardioverter defibrillator (ICD) together with a pacemaker system in three patients with ventricular tachycardia and bradyarrhythmias. Both systems (ICD and pacemaker) were implanted in the same left pectoral quadrant using a single skin incision and the subclavian and/or the cephalic vein. The ICD was implanted deep to the pectoralis major muscle, the pacemaker was placed subcutaneously in a more medial pocket. There were no technical difficulties during implantation or complications during follow‐up.
Late Recurrence of Atrial Flutter Following Radiofrequency Catheter Ablation
Authors: CHEEMA ASIM N. , GRAIS IRA M. , BURKE JOHN H. , INBAR SHMUEL , KADISH ALAN H. , GOLDBERGER JEFFREY J.
Published: July 2006

The success rate for catheter ablation of atrial flutter has been reported to be approximately 90%, but recurrences are common and can be seen in up to 20% of cases. Most of these recurrences are seen within a few weeks following ablation. We report on a patient who developed a recurrence of type I atrial flutter 2 years after an initially successful radiofrequency catheter ablation procedure. Whether the recurrent atriai flutter is due to a new reentrant circuit resulting from slow progression of atrial disease or due to the changes produced by radiofrequency energy in the nearby myocardium is not clear. Further work to define the electrophvsiological changes in the atrial myocardium produced by radiofrequency energy, as well as long‐term follow‐up of patients undergoing radiofrequency catheter ablation for atrial flutter may help in answering these questions.
Atrial Flutter in a Pediatric Patient in the Immediate Period After the Fontan Procedure: Control with Oral Propafenone
Authors: HERZBERG GILBERT Z. , ROSSI ANTHONY F.
Published: July 2006

A 2‐year‐old male underwent Fontan procedure as the third stage palliative repair for hypolastic left heart syndrome. On postroperative day number 15, he developed atrial flutter unresponsive to multiple attempts at cardioversion and therapeutic levels ofdigoxin and pro‐cainamide. Oral propafenone was administered and within 6 hours no further arrhythmias or side effects were noted. This case suggests that oral propafenone can be used with efficacy for the treatment of atrial flutter encountered in the immediate postoperative period following the Fontan procedure.
Demonstration of Purkinje Potential During Idiopathic Left Ventricular Tachycardia: A Marker for Ablation Site by Transient Entrainment
Authors: NISHIZAKI MITSUHIRO , ARITA MASATAKA , SAKURADA HARUMIZU , ASHIKAGA TAKASHI , YAMAWAKE NORIYOSHI , NUMANO FUJIO , HIRAOKA MASAYASU
Published: July 2006

A Marker for Ablation Site by Transient Entrainment. During VT of QRS morphology with right bundle branch block and left axis deviation in a patient without obvious structural heart disease, entrainment by pacing from the right ventricular outflow tract and high right atrium was demonstrated. During entrainment of VT, a Purkinje potential preceding the QRS and recorded at the left ventricular midseptum was activated by orthodromic impulses in the reentry circuit. The interval between the Purkinje potential and the earliest left ventricular activation was decrementally prolonged with shortening of pacing cycle length. Radiofrequency energy was applied to this site, resulting in successful elimination of VT. Therefore, the Purkinje potential represented activation by an orthodromic wavefront in the reentry circuit, while the orthodromically distal site to this potential showed an area of slow conduction with decremental property.
The Optimal Pacing Rate: An Unpredictable Parameter
Authors: PAYNE GILLIAN , SPINELLI JULIO , GARRATT CLIFEORD J. , SKEHAN J. DOUGLAS
Published: July 2006

A three phase relation has been demonstrated between increasing heart rate and cardiac output at rest. Phase I with cardiac output increasing with increasing heart rate, phase II a plateau, and phase III decreasing cardiac output with any further increase in heart rate. The “optimal rate” can be defined as the heart rate at the onset of phase II. Twenty patients were studied, 13 male, mean age 60 years (range 31–71 years). All had chronic complete heart block and established DDD pacing. A maximal exercise test was performed to determine peak sinus rate. Exercise hemodynamics were measured using an ambulatory monitor (Capintec Vest), which permits measurement of relative cardiac output and relative ejection fraction. The patients were programmed to VVI pacing at a rate of 60 beats/min and performed three exercise tests at different workloads. The order of workloads was randomized and selected from a range (0, 25, 50, or 75 W) depending on fitness. After 3‐minute stabilization, the VVI pacing rate was increased at 1‐minute intervals until higher than peak sinus rate giving a total exercise time of 12 minutes. The “optimal rate band” was determined at each workload. The mean of this “optimal rate band” for each workload varied in a nonlinear manner. There was no correlation between “mean optimal rate” and age or the peak rate predicted by the Astrand formula. Current definitions of chronotropic incompetence are inaccurate. Are some of these people at their “optimal rate” already? The arbitrary selection of rate response curves on age related criteria may lead to an impaired hemodynamic response.
Transvenous Defibrillation Leads: Is There an Ideal Position of the Defibrillation Anode?
Authors: TRAPPE HANS‐JOACHIM , PFITZNER PETRA , FAIN ERIC , DRESLER CRISTOPH , FIECUTH HANS‐GERD
Published: July 2006

A potential benefit of two‐lead transvenous defibrillation systems is the ability to independently position the defibrillation electrodes, changing the vector field and possibly decreasing the DFT, Using the new two‐lead transvenous TVL lead system, we studied whether DFT is influenced by SVC lead position and whether there is an optimal position. TVL leads and Cadence pulse generators were implanted in 24 patients. No intraoperative or perioperative complications were observed. In each patient, the DFTs were determined for three SVC electrode positions, which were tested in random order: the brachiocephalic vein, the mid‐RA, and the RA‐SVC junction. The mean DFTs in the three positions were not statistically different, nor was any single lead position consistently associated with lower DFTs. However, an optimal electrode position was identified in 83% of patients, and the DFT from the best lead position for each patient was significantly lower than for any one of the electrode positions (P < 0.01). The mean safety margin for the best SVC lead position was approximately 27 J. These results demonstrate the advantage of a two‐lead system, as well as the importance of testing multiple SVC lead positions when the patient's condition permits. Both of these factors can decrease the DFT and maximize the defibrillation safety margin. This will become increasingly important as pulse generator capacitors become smaller (as part of the effort to decrease generator size) and the energy output of the generators consequently decreases.
The Effect of Electrode Size on Transvenous Defibrillation Energy Requirements: A Prospective Evaluation
Authors: HALPERIN BLAIR D. , REYNOLDS BRIAN , FAIN ERIC S. , LIGON DAVID A. , SILKA MICHAEL J.
Published: July 2006

Recent technological advances have resulted in high success rates for implantation of nonthoracotomy defibrillation lead systems. Further decreases in defibrillator size, facilitating pectoral placement, will depend in part on lowering defibrillation energy requirements. The purpose of this study was to determine if endocardial defibrillation energy requirements are influenced by electrode size. Thirteen adult mongrel dogs were studied under general anesthesia. A9 Fr integrated bipolar pace/sense/defibrillation electrode (cathode) was positioned transvenously at the RV apex. The second defibrillation electrode (anode) was positioned at the junction of the RA and SVC. Two diameters of the proximal electrode, 7 Fr and 11 Fr, were sequentially tested in random order in each animal. The DFT for each electrode was determined using a 50‐V up‐down method. Energy, leading edge voltage, and current, current distribution, and total resistance were measured. The mean defibrillation voltage threshold with the 11 Fr proximal electrode was significantly less than with the 7 Fr proximal electrode (551.1 ± 76.5 V vs 588.5 ± 54.6 V, P < 0.01). Similarly, the mean DFT with the 11 Fr electrode was less than with the 7 Fr electrode (20.7 ±5.7J vs 23.3 ± 4.4 J.P < 0.01). Lower DFTs were found using the larger electrode in 11 of the 13 animals studied. However, there was no difference in defibrillation lead impedance between the two electrode systems. Endocardial defibrillation energy requirements may be lowered with a larger diameter proximal electrode. The mechanism by which this occurs may be due to a more even distribation of current gradients with the larger electrode. Determination of the optimal electrode size requires evaluation in humans, as this may allow further reduction in defibrillation energy requirements and defibrillator size.
Acute Hemodynamic Effects of Atrioventricular Pacing at Differing Sites in the Right Ventricle Individually and Simultaneously
Authors: BUCKINGHAM THOMAS A. , CANDINAS RETO , SCHLÄPFER JÜRG , AEBISCHER NICOLE , JEANRENAUD XAVIER , LANDOLT JACQUELINE , KAPPENBERGER LUKAS
Published: July 2006

We hypothesized that pacing, which provided a rapid uniform contraction of the ventricles with a narrower QRS, would produce a better stroke volume and cardiac output (CO). We sought to study whether pacing simultaneously at two sites in the right ventricle (right ventricular apex and outflow tract) would provide a narrower QRS and improved CO in 11 patients undergoing elective electrophysiology studies. Patients were studied by transthoracic echocardiography measurement of CO using the Doppler flow velocity method in normal sinus rhythm, AOO pacing (rate 80), DOO pacing in the right ventricular apex (AV delay 100 ms). DOO pacing in the right ventricular outflow tract, and DOO pacing at both right ventricular sites simultaneously in random order. The COs were 5.42 ± 1.83, 5.61 ± 1.97. 5.67 ± 1.6. 5.84 ± 1.68. and 5.86 ± 1.52 L/min, respectively (no significant difference by repeated measures analysis of variance [ANOVA]). The QRS durations were 0.09 ± 0.02, 0.09 ± 0.02. 0.13 ± 0.027, 0.13 ± 0.03, and 0.11 ± 0.03 sees respectively. Repeated measures ANOVA showed that the QRS duration significantly increased with right ventricular apex or right ventricluar outflow tract pacing compared to sinus rhythm and AOO pacing (P < 0.001) but then diminished with pacing at both sites (P < 0.01). QRS duration was not correlated with CO, however the change in QRS duration correlated significantly with the change in CO when pacing was performed at the two right ventricular sites simultaneoasly. In conclusion, during DOO pacing, there was a trend for pacing in the right ventricular outflow tract or both sites to improve the CO compared to the right ventricular apex. With simultaneous pacing at both ventricular sites, the QRS narrowed. Further studies will be required to see if this approach has value in patients with poor left ventricular function or congestive heart failure.