bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypertrophic Cardiomyopathy: valuation and Treatment of Patients at High Risk for Sudden Death
Authors: FANANAPAZIR LAMEH , McAREAVEY DOROTHEA
Published: July 2006

Hypertrophic cardiomyopathy (HCM) is a heritable disease characterized by LV hypertrophy with markedly variable clinical, morphological, and genetic manifestations. It is the most common cause of sudden death in otherwise healthy young individuals. HCM patients often have disabling symptoms and are prone to arrhythmias. Frequently, there is associated LV systolic and diastolic dysfunction, LV outflow obstruction, and myocardial ischemia. Over the past decade, progress has been made in identifying patients who are at high risk for sudden death, in elucidating potential mechanisms of sudden death, and in defining therapeutic algorithms that may improve prognosis. It has also been possible to determine the genetic defect in some of the patients and to correlate clinical findings with the molecular defects. An exciting development has been the use of the dual chamber pacemaker as an alternative to cardiac surgery to improve symptoms and relieve LV outflow obstruction.
Ventricular Tachycardia: Pathophysiology and Radiofrequency Catheter Ablation
Authors: SIMONS GRANT R. , KLEIN GEORGE J. , NATALE ANDREA
Published: July 2006

Limitations of pharmacological therapy for VT have led to great interest in alternative nonpharmacological therapies. The appeal of a curative therapy for VT initially led to the search for operative techniques to identify and destroy the underlying substrate, and more recently, has resulted in the development of catheter techniques to achieve the same goal in the electrophysiology laboratory. Investigations into the pathophysiology of VT have resulted in the recognition that this arrhythmia reflects a mechanistically and anatomically heterogeneous set of disorders. Recent growth in our understanding of these distinctions has both led to, and resulted from, simultaneous advances in catheter ablation techniques. The clinical electrophysiology laboratory has served as a testing ground for theories derived from in vitro and animal experiments while also providing its own set of human experimental data regarding the pathophysiology and treatment of VT. As a result of this process, several distinct forms of VT that are amenable to catheter ablation have been characterized. This article will summarize current knowledge of the pathophysiology of various VT subtypes and of techniques for catheter mapping and ablation.
Quantitative Analysis of Concealed Conduction into Accessory Atrioventricular Pathways in Wolff‐Parkinson‐White Syndrome
Authors: TANAKA KAZUSHI , SUZUKI FUMIO , HIEJIMA KAZUMASA , FUJIMURA OSAMU
Published: July 2006

Concealed conduction is demonstrated to occur in an accessory AV pathway (AP). To test the hypothesis that anterograde and retrograde concealed conduction in the AP would have different characteristics, 35 consecutive patients with single APs were studied. The anterograde or retrograde ERP of the AP could be determined in 23 of those patients. Anterograde concealed conduction in the AP was assessed in the first 13 patients with retrograde AP conduction (8 APs with retrograde conduction only and 5 with both directions) (group A). Retrograde concealed conduction in the AP was evaluated in the remaining 10 patients with anterograde AP conduction (6 APs with anterograde conduction only and 4 with both directions) (group B). The concealed conduction in the AP was quantified by determining the ERP of the AP using a “probe” extrastimulus (Sp) introduced in the opposite chamber. The ERP was determined both during conventional extrastimulus (S1S2 method; ERPc) and during that with an Sp (S1SpS2 method; ERPp). The Sp was delivered before or after the last S1 with various S1Sp intervals. The ERPp was determined at each S1Sp interval. Three distinct patterns in concealed conduction in the AP were noted. In the first pattern, the ERPp was always shorter than the ERPc, whereas the reverse relation was noted in the second pattern. The third pattern showed a combination of the two. In group A, only the first pattern was noted. In group B, the first, second, and third patterns were noted in 4, 2, and 4 patients, respectively. The first pattern was noted only in septal APs and the second and third were seen only in left free‐wall APs. The second pattern was seen in patients with retrograde AP conduction, whereas the third one was mainly noted in patients without retrograde AP conduction. These observations indicate that anterograde and retrograde concealed conduction in the AP have different characteristics. Shortening of the ERPp might be due to the “peeling back” phenomenon, and its lengthening might be caused by the presence of the inhomogeneous refractory periods of the AP. (PACE 1997; 20[Pt. I]:1342‐1353)
High Dose Neostigmine Treatment of Malignant Sinus Tachycardia
Authors: SCHULTHEIS LEX W. , BALSER JEFFREY R. , CALKINS HUGH , ROBERTSON SHAWN , WEISS JAMES L. , SUSSMAN MARC , STUART R. SCOTT
Published: July 2006

We report the case of a patient with Wolff‐Parkinson‐White syndrome with angina and cardiogenic shock who improved dramatically following administration of neostigmine. Cardiac output, blood pressure, and stroke volume increased as heart rate was reduced. A previous attempt at heart rate control, in the same patient, using a low dose β antagonist, precipitated hemodynamic collapse. The remarkable recovery of our patient suggests that acetylcholinesterase inhibitors may warrant further investigation in patients with severe sinus tachycardia.
Study of Pacemaker and Implantable Cardioverter Defibrillator Triggering by Electronic Article Surveillance Devices (SPICED TEAS)
Authors: MCIVOR MICHAEL E. , REDDINGER JUDITH , FLODEN ELIZABETH , SHEPPARD ROBERT C. , Johnson Delos , Becker Gerald I. , Mayotte Mark
Published: July 2006

The magnetic fields emitted by electronic article surveillance (EAS) systems (shoplifting gates) are a source of interference for implanted medical devices. In the Study of Pacemaker and Implantable Cardioverter Defibrillator Triggering by Electronic Article Surveillance Devices (SPICED TEAS), 25 adult volunteers with ICDs and 50 with pacemakers were exposed to the fields of six different EAS systems. These EAS systems used three modes of operation: magnetic audio frequency, swept radio frequency, and acoustomagnetic technology. No ICD exhibited interference mimicking sensing of tachyarrhythmias with any EAS system. Pacemakers interacted variably, depending on the type of EAS system. Swept radiofrequency systems produced no interaction with any implanted medical device. One magnetic audio frequency system interacted with 2 of 50 pacemakers. The acoustomagnetic system interacted with 48 of 50 pacemakers. Interactions included asynchronous pacing, atrial oversensing (producing “EAS induced tachycardia” in the ventricle), ventricular oversensing (with pacemaker inhibition), and paced beats resulting from the direct induction of current in the pacemaker (“EAS induced pacing”). These interactions produced symptoms in some patients (palpitations, presyncopel only while patients were in the EAS field. No pacemaker was reprogrammed. We conclude that high energy, pulsed low frequency EAS systems such as acoustomagnetic systems interfere with most pacemakers. Pacemaker patients should be advised to minimize exposure to the fields of such systems to prevent the possibility of serious clinical events.
Cerebral Hemodynamics During Carotid Massage in Patients with Carotid Sinus Syndrome
Authors: LEFTHERIOTIS GEORGES , ROZAK PHILIPPE , DUPUIS JEAN‐MARC , VICTOR JACQUES , TADEI ANDRE , SAUMET JEAN LOUIS
Published: July 2006

The effect of cardioinhibition and/or vasodepression on cerebral hemodynamics assessed by transcranial Doppler has been investigated during carotid massage in 11 patients (62–87 years, mean age 72) with carotid sinus syndrome. The patients were tested in the OOO mode (n = 11) with six tested in the DDD mode. Carotid massage in the OOO mode decreased mean arterial pressure by 44% (P < 0.01) and mean cerebral blood flow velocity by 50% (P < 0.01). Although not significant, cerebrovascular resistance increased transiently by 17% during massage, then decreased by 31% upon recovery. Carotid massage in the DDD mode decreased arterial pressure by 30% (P < 0.01), cerebral blood velocity by 23% (P < 0.01), and resistance by 15% (P < 0.05). The decreased cerebral perfusion induced by cardioinhibition and/or vasodepression results from the delayed onset of cerebral autoregulation. Pacing in the DDD mode temporarily assists the critical period preceding the onset of cerebral autoregulation that plays a key role in preventing the deleterious effects of vasodepression.
Late Complications in Patients with Pectoral Defibrillator Implants with Transvenous Defibrillator Lead Systems: High Incidence of Insulation Breakdown
Authors: MEHTA DAVENDRA , NAYAK HEMAL M. , SINGSON MAGDALENA , CHAO SALLY , PE ELENA , CAMUÑAS JORGE L. , GOMES J. ANTHONY
Published: July 2006

As the majority of ICDs with transvenous leads are now implanted in tbe pectoral region, complications associated with the technique are being identified. To determine the incidence of lead complications in patients with transvenous defibrillator leads and ICDs implanted in the pectoral region, 132 unselected consecutive patients with transvenous defibrillator leads had ICDs implanted in the pectoral region. Three lead systems were used:(1) lead system 1(45 patients) consisted of a transvenous pacing sensing lead and a superior vena cava coil with a submuscular patch used for defibrillation;(2) lead system 2(36 patients) utilized a CPI Endotak lead system: and(3) lead system 3(51 patients) utilized a Medtronic Transvene lead system. Patients were followed for 3–54 months(cumulative 2,269, mean 18 months). The average duration of follow‐up with the three systems was 32, 12, and 11 months, respectively. At 30 months follow‐up, all three lead systems had a low incidence of complications. However, there was a 13% overall incidence(45% actuarial incidence) of erosion of the insulation of the pacing sensing lead of system 1 at 50 months of follow‐up. All lead complications were seen in patients with ICDs whose weights were > 195 g and volumes > 115 cc. The erosion was probably a consequence of the pressure by the large ICD against the lead in the pectoral pocket. Follow‐up with lead systems 2 and 3 is relatively short(average 12 months) but no lead erosions were seen. Pectoral implantation of ICDs with long transvenous leads and large generators is associated with a moderate risk of late complications in the form of insulation breaks caused by pressure of the generator against the leads. The use of less redundant leads coupled with smaller ICDs will probably eliminate this complication.
The “SPEM” (Studio Policentrico Elettrocateteri Membrane): A Multicenter Study on Membrane Leads
Authors: RUSCONI LUIGI , SIGLIANO RICCARDO , MININNO ANTONIO ,   THE SPEM INVESTIGATORS
Published: July 2006

SPEM is a multicenter randomized double‐blind study performed to test the acute and chronic electrophysiological behavior of three different ventricular leads: (1) an ion exchange membrane with 30‐μg dexamethasone elution in a contoured activated carbon tip lead (Membrane 1400T, 30 patients); (2) the same lead design without steroid (Membrane 1401T, 24 patients); and (3) the same lead design without steroid or membrane (control group, 27 patients). Twenty‐three of the 81 patients were women; the mean age for all patients was 74 ± 10 years. Parameters are calculated both in uni‐ and bipolar configuration at implant and at follow‐up after 1, 5, 15, 30, 90, 180, and 360 days. Implant threshold (chronaxie = 0.413 ± 0.280 ms, rheobase = 0.264 ± 0.099 V), signal amplitude (13.45 ± 5.87 mV), and slew rate (2.05 ± 1.38 V/s) reveal no significant differences. Pacing impedance values both at implant (unipolar 571 ± 165 Ω; bipolar 605 ± 123 Ω) and at follow‐ups (unipolar 480 ± 72 Ω; bipolar 518 ± 75 Ω) are slightly lower in the unipolar configuration. At 15 and 30‐day follow‐ups, control group and nons‐teroid leads show a higher threshold value growth (in unipolar from 0.16 ± 0.11 to 1.19 ± 0.85 μJ; in bipolar from 0.18 ± 0.13 to 1.24 ± 0.88 μJ) than the membrane steriod leads (in unipolar from 0.13 ± 0.11 to 0.70 ± 0.39 μJ; in bipolar from 0.23 ± 0.32 to 0.76 ± 0.36 μJ); the threshold of nonsteroid leads decreases after 1–3 months and it settles at the same threshold level of the leads with membrane and steroid (in unipolar 0.60 ± 0.33 ±J; in bipolar 0.55 ± 0.26 μJ), which has been stable since the first month. The ion exchange membrane is effective in reducing the chronic pacing threshold like acute steroid elution at low doses, but membrane alone does not prevent an acute pacing threshold increase through the first month postimplant.
Clinical Use of Low Output Settings in 1.2‐mm2Steroid Eluting Electrodes: Three Years of Experience
Authors: DANILOVIC DEJAN , OHM OLE‐JØRGEN , BREIVIK KJELL
Published: July 2006

A new generation of tined steroid‐eluding leads featuring 1.2‐mm2 distal electrodes (CapSure® Z, Medtronic Inc., Minneapolis MN, USA) has the potential to reduce battery current drain and enhance pulse generator longevity by means of high pacing impedance and low pacing threshold. Forty patients aged 50–87 years (mean 72.4 years) were implanted with 33 ventricular (models 4033 and 5034) and 30 atrial‐J (models 4533 and 5534) leads with 1.2‐mm2 electrodes. Low pacing outputs, mainly in the range from 1 V/0.20 ms to 1.6 V/0.36 ms with ≥ 3:1 pulse width safety margins (PWSM) applied, were instituted at 3–6 months of implantation and adjusted at subsequent follow‐up controls according to changes in thresholds. Cumulative follow‐up period of low outputs was 1,512 months (24 months per lead, range 9–36 months), which involved 3.43 follow‐up controls per lead (range 2–5). During follow‐up, pulse width thresholds (PWTs) at the used amplitudes did not change in 55.5% of the leads; PWTs increased by ≤ 100% in 36.5%, by 101%–200% in 1.6%, and by > 200% in 6.3% of the leads. Changes in PWT that would apparently exceed 3:1 PWSM over a 1‐year period occurred in one atrial lead where even the nominal 3.5 V/0.4‐ms output would not be effective and in one ventricular lead in the aftermath of an acute myocardial infarction (300% PWT rise at 1.6 V). Based on the present observations, pacemaker dependent patients require ≥ 4:1 PWSM and other patients ≥ 3:1 PWSM with output pulse widths ≤ 0.60 ms and annual pacemaker clinic visits. Calculated battery current drain and anticipated longevity associated with a variety of pacing outputs and impedances are provided, compared, and discussed. Correlation between acute and chronic pacing impedances and pacing thresholds was weak, implying that a systematic intraoperative pacing site optimization cannot contribute significantly to the extension of average battery longevity.
Stability of the Defibrillation Probability Curve with the Development of Ventricular Dysfunction in the Canine Rapid Paced Model
Authors: FRIEDMAN PAUL A. , FOLEY DAVID A. , CHRISTIAN TIMOTHY F. , STANTON MARSHALL S.
Published: July 2006

Most patients with implantable defibrillators have diminished cardiac function. Progressive heart failure might impair defibrillation efficacy, leading to interpreted device, failure. This study sought to determine the effect of ventricular dysfunction on defibrillation energy using a biphasic endocardial system. Eleven dogs were ventricularly paced at 225 pulses/min for 2 weeks to induce ventricular dysfunction, and five control dogs remained unpaced. Dose response defibrillation probability curves were generated for each animal at baseline, after 2 weeks (at which time the pacemakers were turned off in the paced group), and then 1 week later. The defibrillation thresholds, ED20, ED50, and ED80 (the 20%, 50%, and 80% effective defibrillation energies, respectively) were determined for each dog at each study. In the paced dogs, the mean ejection fraction fell from 55% to 25% after pacing (P < 0.0001), and rose to 46% after its discontinuation (P = 0.0002). The defibrillation threshold, ED20, ED50, and ED80 remained unchanged in both the control and paced groups for all three studies, even after adjustment for dog weight or left ventricular mass. Rapid pacing produced no change in left ventricular mass. It induced ventricular cavity dilatation and wall thinning, which had opposing effects on defibrillation energy requirements, resulting in no net change of the ED50 in heart failure. In conclusion, the defibrillation efficacy of a biphasic transvenous system is not changed by the development of heart failure using the rapid paced canine model.
Clinical, Electrophysiological Characteristics, and Radiofrequency Catheter Ablation of Atrial Tachycardia Near the Apex of Koch's Triangle
Authors: LAI LING‐PING , LIN JIUNN‐LEE , CHEN TING‐FU , KO WEN‐CHIN , LIEN WEN‐PIN
Published: July 2006

Atrial tachycardia, with its focus near the apex of Koch's triangle, may carry a potential risk of atrioventricular block during radiofrequency catheter ablation. The efficacy and safety of this procedure have never been addressed. The characteristics and catheter ablation results are reported for six patients with atrial tachycardia near the apex of Koch's triangle. All six patients were female aged 49.6 ± 9.3 years (range 39–63). Organic heart disease was present in 3 (50%) of the 6 patients. The P wave in surface ECG had a mean axis of − 28° (range − 90°–+ 30°) in the frontal plane. The catheter ablation was guided by activation sequence mapping. The energy was titrated from low power level. Atrial overdrive pacing was used to monitor the atrioventricular conduction should accelerated functional rhythm occur. At the final successful ablation site, the local atrial activation was 41.8 ± 9.1 ms before the P wave and His‐bundle potential was present in 5 of the 6 patients. All patients had their atrial tachycardia eliminated without recurrence or heart block during a follow‐up period of 17.7 ± 8.5 months (range 6–30). In conclusion, atrial tachycardia near the apex of Koch's triangle has distinct clinical and electrophysiological features, Radiofrequency catheter ablation can be performed effectively. However, extreme care must be taken to prevent inadvertent atrioventricular block. Titrated energy application and continuous monitoring of atrioventricular conduction are mandatory.
Dependency on Atrial Electrophysiological Properties of Appearance of Paroxysmal Atrial Fibrillation in Patients with Wolff‐Parkinson‐White Syndrome: Evidence from Atrial Vulnerability Before and After Radiofrequency Catheter Ablation and Surgical Cryoablation
Authors: MURAOKA YUJI , KARAKAWA SHINJI , YAMAGATA TOGO , MATSUURA HIDEO , KAJIYAMA GORO
Published: July 2006

The pathogenesis of paroxysmal atrial fibrillation in patients with Wolff‐Parkinson‐White syndrome and the effects of elimination of accessory pathways on the appearance of atrial fibrillation are still controversial. Fifty‐four patients with Wolff‐Parkinson‐White syndrome were classified into three groups: a No AFgroup (n = 24), patients without paroxysmal atrial fibrillation; an RF‐AF Group (n =12), patients with paroxysmal atrial fibrillation whose accessory pathways were eliminated using radiofrequency catheter ablation; and a Cryo‐AF Group (n = 18), patients with paroxysmal atrial fibrillation whose accessory pathways were eliminated with surgical Cryoablation. The electrophysiological characteristics of each group were evaluated prior to and following the elimination of their accessory pathways. As indices of atrial vulnerability, the presence of fragmented atrial activity and repetitive atrial firing zones were assessed. Deducibility of atrial fibrillation was significantly reduced following ablation of accessory pathways in the Cryo‐AF group (83.3%‐5.6%, P < 0.0001), while it was unchanged in the RF‐AF group (83.3%‐75%). In preablation studies, the effective refractory periods of the atrium in the RF‐AF group and the Cryo‐AF group were significantly shorter compared with the No AF group (204 ± 18 ms, 197 ± 16 ms vs 246 ± 44 ms, respectively, P < 0.0001). Following ablation, the effective refractory period for patients in the Cryo‐AF group was significantly prolonged compared with before ablation (197 ± 16 ms to 232 ± 24 ms, P < 0.0001). As a result of this prolongation of the effective refractory period of the atrium, the fragmented atrial activity and repetitive atrial response zones narrowed following ablation in the Cryo‐AF group, but not in the RF‐AF group. Therefore, the pathogenesis of atrial fibrillation in patients with Wolff‐Parkinson‐White syndrome may depend on the refractory period of the atrium rather than on the presence of accessory pathways.
Comparison of Right– and Left–Sided Pectoral Implantation Parameters with the Jewel Active Can Cardiodefibrillator
Authors: FLAKER GREG C. , TUMMALA RANGARAO , WILSON JOHN ,   WORLD WIDE JEWEL INVESTIGATORS
Published: July 2006

A total of 1,207 patients received a Medtronic jewel active, can ICD (models 721BC, 7219C), with a Transvene had in 97 centers in Europe and North America. Nineteen implants were from the right pectoral region. Patients with right–sided ICDs did not differ in terms of mean age. % male, left ventricular ejection fraction, New York Heart Association Functional Class, antiar–rhythmic drug therapy, indication for the implantable cardioverter defihrillator, and R wave values at implantation, but tended to have slightly higher pacing thresholds (1.2 ± 0.5 V vs 1.0 ± 0.6 V, P = 0.012) and higher defibrillation thresholds (14.7 ± 6.4 J vs 11.5 ± 6 J, P = 0.11) compared with patients with left sided implants. Patients with right–sided implants had a longer implantation time compared with patients with left–sided implants (118 ± 70 minutes vs 91 ± 46 minutes, P = 0.074). In follow–up, 5 patients with right–sided implantation received successful therapy for either ventricular fibrillation, (8 episodes) or ventricular tachycardia (5 episodes). No ineffective therapy from the device was delivered in any patients with right–sided implantation. Right–sided pectoral implants are feasible with the Medtronic Jewel active can ICD.
The Effects of Pneumothorax on Defibrillation Thresholds during Pectoral Implantation of an Active Can Implantable Cardioverter Defibrillator
Authors: COHEN TODD J. , LOWENKRON DAVID D.
Published: July 2006

Pneumothorax has previously been reported to increase defibriliation thresholds and lead impedance in monophasic systems. This article demonstrates a case using an active can system in which the lead impedance between the right ventricular defibriliation coil and the device improved from 70 il with pneumothorax to 48 Ω after resolution. The defibriliation threshold also improved from > 30 fto ≤ 10 J after the pneumothorax had resolved. We conclude that acute pneumothorax can increase the transthoracic lead impedance and defibriliation thresholds: however, with resolution both parameters can return to acceptable levels with an active can system.
Experience with a Lead Fixation/Suture Sleeve
Authors: GAMMAGE MICHAEL D. , KRABB HANS‐JURGEN , MOQUET BENOIT , HUGUET RENE G. , JAUSSERAN JEAN M. , POHNDORF PETER J.
Published: July 2006

Current anchoring systems on pacemaker leads are crude in comparison to the lead technology. Poor anchoring technique may cause damage to the lead or early displacement from incorrect suture tension. We describe experience with a locking anchoring sleeve that applies a constant gripping force to the lead body. This can be locked and unlocked to allow optimal positioning after fixation of the sleeve to underlying tissues. The sleeve was fitted to a 55D polyurethane lead (Medtronic 4024, 7 Fr, bipolar, steroid elating) implanted in the ventricular position in 22 patients at four European centers. All implants were uncomplicated; data were collected on handling and ease of use. Assessments were made using a scale of 1–10 (10 = excellent, 5 = equivalent to conventional sleeve). Overall ease of use compared to conventional sleeve was 7.79 ± 0.62 (mean ± SD). Mean scoring of flexibility of the lead at the transition points was 7.92 ± 0.72; ability to lock/unlock the sleeve scored 6.28 ± 1.78. Ease of suturing around the sleeve scored 8.07 ± 0.77, and ability to slide the sleeve along the lead body scored 6.48 ± 1.99. Chest X rays at 6 weeks showed no change in lead position with respect to postimplant films, and all leads showed a straight path on either side of the sleeve with no evidence of conductor distortion. Follow‐up to 3 years has been without problem. All leads remain intact and in place, with stable thresholds and no evidence of erosion. There have been no complaints of patient discomfort. We conclude that this device is safe and effective and offers a significant advance in lead fixation.
Effects of Hydrophilic and Lipophilic β‐Blockers on Heart Rate Variability and Baroreflex Sensitivity in Normal Subjects
Authors: PITZALIS MARIA VITTORIA , MASTROPASQUA FILIPPO , MASSARI FRANCESCO , FORLEO CINZIA , PASSANTINO ANDREA , COLOMBO ROBERTO , TOTARO PAOLO , RIZZON PAOLO
Published: July 2006

To evaluate the effect of a hydrophilic and a lipophilic β‐ blocker on the autonomic nervous system, 20 normal subjects were studied under baseline conditions and 7 days after being randomly assigned to metoprolol (200 mg/day), nadolol (80 mg/day), and placebo. Under each condition, the time‐domain parameters were analyzed by means of 24‐hour ECG monitoring and the frequency‐domain parameters by means of the autoregressive method using 10‐minute ECGs during rest, controlled respiration, and after a head‐up tilt test. The alpha index (the gain in the relationship between the RR period and systolic arterial pressure variability) was also calculated. Both nadolol and metoprolol significantly increased all of the time‐domain parameters except the standard deviation of the RR intervals; they also modified the frequency‐domain parameters. Both blunted the significant reduction in the high frequency (HF) component and alpha index during tilt. In normal subjects, hydrophilic and lipophilic β‐blockers similarly modify the time‐ and frequency‐domain parameters that are particularly evident when high sympathetic tone is present (during daytime and tilt). The value of the alpha index was increased by both β‐blockers in the HF, but not in the low frequency band; this difference might be due to the fact that the former is a measure of the vagal component of the baroreflex control and the latter a measure of the sympathethic component. The effects of hydrophilic and lipophilic β‐blockers on the time‐ and frequency‐domain parameters of heart rate variability are similar.
Transvenous Single Lead Atrial Defibrillation: Efficacy and Risk of Ventricular Fibrillation in an Ischemic Canine Model
Authors: OSSWALD STEFAN , TROUTON THOMAS G. , ROELKE MARC , O'NUNAIN SEAN S. , FALLON JOHN T. , HOLDEN HARTLEY B. , RUSKIN JEREMY N. , GARAN HASAN
Published: July 2006

Transvenous atrial defibrillation with multiple atrial lead systems has been shown to be effective in models without the potential for ventricular arrhythmias. The specific aim of this study was to evaluate the efficacy and safety of transvenous single lead atrial defibrillation in a canine model of ischemia cardiomyopathy. Ten dogs had ischemia cardiomyopathy induced by repeated intracoronary micmsphere injections. The mean LV ejection fraction decreased from 71%± 9% to 38%± 14% (P = 0.003). Spontaneous atrial fibrillation (AF) developed in four dogs, and in six AF was induced electrically. Atrial defibrillation thresholds (ADFTs) were determined with synchronous low energy shocks using a transvenous tripolar lead with two defibrillation coils (right ventricle, superior vena cava) and an integrated sensing lead (RV coil vs electrode tip). The ADFTs derived by logistic regression were compared at 50% and 90% probability of success (ED50, ED90): ED50 was 2.4 ±1.7 J and 2.9 ±2.1 J, respectively, for 5‐ and 10‐ms monophasic shocks, and 1.8 ± 0.9 J and 2.1 ± 1.3 J, respectively, for 5‐ and 10‐ms biphasic shocks. Immediately after 3 of 2,179 (0.1%) synchronized shocks, ventricular fibrillation (VF) developed. VF was induced in 3 of 1,062 (0.3%) shocks with integrated sensing (RV coil vs electrode tip) compared to 0 of 1,117 shocks when a separate bipolar RV sensing electrode was used for synchronization. In our canine model of ischemic cardiomyopathy, low energy atrial defibrillation via a transvenous single lead system was highly effective. However, there was a small but definite risk of VF induction, which seemed to be greater when an integrated as opposed to a true bipolar RV sensing was used.
Possible Involvement of Cerebral Hypoperfusion as a Trigger of Neurally‐Mediated Vasovagal Syncope
Authors: ABE HARUHIKO , KOHSHI KIYOTAKA , KUROIWA AKIO
Published: July 2006

It is well known that some patients with neurally mediated syncope have a feeling of aura before the onset of syncope. A case is reported in which cerebral dysfunction recorded by EEG was present before the onset of a vasovagal reaction. The vasovagal reaction, bradycardia and/or asystole, was preceded by abnormal EEG findings when the patient complained of feeling a headache, photophobia, and nausea. These findings suggest that cerebral hypoperfusion, such as with cerebral vasospasms, before the onset of bradycardia might be involved in the mechanism of neurally mediated syncope in patients with an aura.
Transcoronary Ethanol Ablation of the Atrioventricular Node in a Young Patient with Tricuspid Atresia
Authors: COSTEAS XENOPHON F. , BERUL CHARLES I. , FOOTE CAROLINE B. , HOMOUD MUNTHER K. , MARX GERALD R. , SMITH JOHN J. , ESTES N. A. MARK , WANG PAUL J.
Published: July 2006

Catheter ablation of AV conduction with radiofrequency energy can be challenging in the presence of structural abnormalities of the AV junction, either congenitally or after reconstructive surgery. We used transcoronary ethanol to ablate the AV node in a patient with classic tricuspid atresia and refractory intraatrial reentry tachycardia. This approach provides an alternative means of creating complete heart block with catheter‐based techniques, when radiofrequency catheter ablation is technically impossible or ineffective.
Long–Term Effect of VVI Pacing on Atrial and Ventricular Function in Patients with Sick Sinus Syndrome
Authors: PAXINOS GEORGE , KATRITSIS DEMOSTHENES , KAKOUROS STAVROS , TOUTOUZAS PAVLOS , CAMM A. JOHN
Published: July 2006

We conducted a prospective, 6–month echocardiographic study on the effect of WI pacing on left atrial and ventricular function and dimensions in patients with sick sinus syndrome. Thirty nine patients (23 women and 16 men, aged 71.7 ± 9.2 years; 30 in sinus rhythm and 9 in atrial fibrillation) who had a WI pacemaker implanted because of sick sinus syndrome were recruited in the study. In 26 patients who presented with and remained in sinus rhythm, paced left ventricular ejection fraction and stroke volume were significantly decreased (71.4%± 11.8% to 67.0%± 13.6%, and 73.9 ± 29.0 cm3 to 66.3 ±21.1 cm3, respectively, P < 0.001 for both), whereas the paced diastolic dimension of the left atrium was significantly increased (3.2 ± 0.7 cm to 3.7 ± 0.9 cm, P < 0.001) at 6 months as compared with preimplantation. In nine patients with atrial fibrillation at implantation, paced left ventricular ejection fraction at follow–up was significantly decreased (67.7%±10.1% to 64.2%± 10.6%, P = 0.003), but paced stroke volume and left atrial diastolic dimension were not significantly changed (75.1 ± 25.6 cm3 to 79.0 ± 22.7 cm3, and 4.3 ±1.2 cm to 4.6 ±1.5 cm, P = NS for both) at follow–up. Cessation of pacing and restoration of sinus rhythm in 21 patients at follow–up did not result in any significant change of ejection fraction (67.5%± 10.2% to 67.6%± 9.7%, P = NS) whereas stroke volume was increased (59.1 ± 19.6 cm3 to 69.1 ± 22.3 cm3, P < 0.0001) in comparison with paced values. However, compared with preimplantation values, ejection fraction was significantly decreased (70.4%± 10.0% to 67.6%± 9.7%, P = 0.001), whereas stroke volume was not significantly changed (68.4 ± 22.3 cm3 to 69.1 ± 22.3 cm3, P = NS) during sinus rhythm at follow–up. In 14 of those patients, discontinuation of pacing resulted in a significant increase of left atrial fractional shortening (8.1 %± 1.7% to 20.1 %± 4.3%, P < 0.001) and significant increase of left atrial diastolic dimension compared with paced and preimplantation levels (3.8 ± 0.7 cm vs 3.6 ± 0.7 cm and 3.0 ± 0.5 cm, respectively, P < 0.001). Long–term WI pacing in patients with sick sinus syndrome results in increase of the left ventricular end–systolic dimension and permanent reduction of the left ventricular ejection fraction. In the left atrium, WI pacing causes an immediate reduction of the fractional shortening as well as long–term increase of the diastolic dimension.
Instantaneous Lead Entrapment: Successful Percutaneous Removal Using the Cook Workstation
Authors: BARAKAT KHALID , ROBINSON NICHOLAS M. , DYMOND DUNCAN S.
Published: July 2006

An unusual complication of transvenous endocardial lead placement is reported in which an electrode became entrapped within the vicinity of the tricuspid valve apparatus, resisting all initial attempts at removal. The lead was subsequently successfully removed percutaneously via the right femoral vein.
Physiology of the Escape Rhythm After Radiofrequency Atrioventricular Junctional Ablation
Authors: SHEPARD RICHARD K. , NATALE ANDREA , STAMBLER BRUCE S. , WOOD MARK A. , GILLIGAN DAVID M. , ELLENBOGEN KENNETH A.
Published: July 2006

The physiology of the escape rhythm (ER) and its response to pharmacological modulation under varying autonomic conditions were studied in 48 patients undergoing radiofrequency ablation of the atrioventricular junction (AVJ) for refractory atrial fibrillation. The QRS morphology and cycle length (CL) of the baseline ER were measured 15 minutes postablation. The CL of the ER was measured in response to doses of isoproterenol, atropine, adenosine, lidocaine, and verapamil. The ER QRS was narrow (QRS < 120 ms) in 20 patients and wide (QRS > 120 ms) in 28 patients. Of the 28 patients with wide QRS ER, 11 patients had a new bundle branch block (8 patients new right bundle branch block [RBBB] and 2 patients new left bundle branch block [LBBB]). The ERCL was similar in both narrow and wide ERs (1,593 ± 376 ms and 1,516 ± 296 ms, P = 0.44). In 23 patients receiving isoproterenol infusion, the ER CL decreased with increasing doses from 1 mcg/min to 2 mcg/min (1,378 ± 200 to 1,240 ± 229 ms, P < 0.001), but did not decrease further at 3 mcg/min [1,201 ±192 ms, P = 0.48 vs 2 mg/min). Seven patients received 0.02 mg/kg of atropine, and ER decreased significantly (1,572 ± 408 ms to 1,319 ± 333 ms, P = 0.028). In 30 patients who received intravenous boluses of adenosine (6–18 mg), the ER did not change significantly. In 28 patients who received 150 mg of lidocaine, the ER increased from 1,462 ± 286 ms to 1,715 ± 467 ms (P < 0.001), and one patient developed transient asystole. Nineteen patients received 7.5 mg of verapamil, and the ER did not change (1,488 ± 313 ms to 1,513 ± 666 ms, P = 0.80). There was no significant difference in response to isoproterenol, adenosine, lidocaine, or verapamil between the patients with wide and narrow QRS ERs. We conclude that patients may have stable ERs immediately following AVJ ablation even when a wide complex ER results. The ER is responsive to sympathetic stimulation and vagal blockade. The ER is prolonged after lidocaine but not after verapamil, suggesting response to sodium but not to calcium channel blockade. These data are consistent with an ER originating in the distal compact AV node or proximal His bundle.
Long‐Term Performance of Bipolar Epicardial Atrial Pacing Using an Active Fixation Bipolar Endocardial Lead
Authors: EPSTEIN MICHAEL R. , WALSH EDWARD P. , SAUL J. PHILIP , TRIEDMAN JOHN K. , MAYER JOHN E. , GAMBLE WALTER J.
Published: July 2006

Bipolar epicardial leads are not yet widely available for atrial use. Since September 1986, we have used a bipolar active fixation endocardial lead (Cardiac Pacemakers model number's 4266, 4268, and 4269) as a bipolar epicardial atrial lead by attaching the corkscrew tip to the atrial surface and imbricating atrial tissue around the more proximal electrode. A total of 77 bipolar epicardial atrial leads have been implanted using this approach in 72 patients with congenital heart disease (ages 3 months to 38.7 years; mean 8.9 ± 8.8 years). Indications for atrial pacing included AV block (n = 46), sinus node dysfunction (n = 17), and antitachycardial pacing (n = 9). Indications for epicardial pacing included the presence of an intracardiac right to left shunt (n = 33), concomitant cardiac surgery (n = 26), surgeon preference (n = 7), and lack of transvenous access to the atrial endocardium (n = 6). Follow‐up (median 23 months; mean 28.0 ± 23.1 months; range 1–78 months) data beyond 1 month postimplantation were available for 44 leads. Atrial sensing was ≥ 2.0 mV for 26 leads (59%) with sensing possible at ≥ 0.75 mV for 42 leads (95%). Threshold data were available at 5 V for 37 leads and at 2.5 V for 36 leads with mean pulse width thresholds measuring 0.21 ± 0.33 ms and 0.34 ± 0.34 ms, respectively. Two leads failed (high capture thresholds at 5 days [n = 1], lead fracture at 42 months [n = 1]); one of which was replaced. Four additional leads were replaced electively (marginal thresholds [n = 1], intermittent phrenic nerve stimulation [n = 1], damaged during subsequent surgery [n = 1], clinically irrelevant insulation break [n = 1]) concomitant with additional cardiac surgery. Until a commercially available lead is developed and released, improvisation with a bipolar active fixation endocardial lead as a bipolar epicardial atrial lead is a reasonable approach to providing bipolar atrial sensing and pacing in patients for whom endocardial pacing is contraindicated.
Spontaneous Reinitiation of Atrial Fibrillation Following Transvenous Atrial Defibrillation
Authors: SRA JASBIR , BIEHL MICHAEL , BLANCK ZALMEN , DHALA ANWER , JAZAYERI MOHAMMAD R. , DESHPANDE SANJAY , AKHTAR MASOOD
Published: July 2006

Spontaneous reinitiation of atrial fibrillation (AF) has not been systematically looked at in patients undergoing transvenous AF. This study involved 11 patients, the mean age 60 ± 8 years. 3 male and 8 female, in whom transvenous atrial defibrillation successfully converted AF to sinus rhythm. Eight patients had paroxysmal AF and three patients had chronic persistent AF for 4 weeks or more. Four patients were taking antiarrhythmic medications at the time of testing. Multipolar transvenous catheters were positioned inside the coronary sinus, right atrium, and the right ventricle. Atrial defibrillation testing was performed using the METRIX atrial defibrillation system in nine patients and the Ventritex HVSO2 in the remaining two patients. A total of 64 therapeutic shocks (range 3–11) were delivered in the 11 patients, and 31 of these successfully converted AF to sinus rhythm. In four patients spontaneous AF was reinitiated following 12 successful transvenous atrial defibrillation episodes. The mean time to reinitiation of AF following shock delivery and restoration of sinus rhythm was 8.26 ± 5.25 seconds, range 1.8–19.9 seconds. All 12 episodes of spontaneous AF were preceded by a spontaneous premature atrial complex. The coupling interval of the premature atrial complexes was 443 ± 43 ms, range 390–510 ms. None of the patients taking antiarrhythmic medications or those demonstrating no premature atrial complexes had spontaneous reinitiation of AF. In conclusion, spontaneous reinitiation of AF can occur in a significant proportion of patients with AE undergoing transvenous atrial defibrillation. This phenomenon is preceded by the occurrence of atrial premature complex. Findings of this study may have significant clinical implications.(PACE 1998; 21:1105–1110)
Rhythm Management in Atrial Fibrillation—With a Primary Emphasis on Pharmacologic Therapy: Part 3
Authors: KASSOTIS JOHN , COSTEAS CONSTANTINOS , BLITZER MARK , REIFFEL JAMES A.
Published: July 2006

Atrial fibrillation (AF) is the most common, sustained, symptomatic tachyarrhythmia that clinicians are called upon to manage. Management strategies include ventricular rate control coupled with anticoagulation, versus restoration and maintenance of sinus rhythm. Rate control may be achieved pharmacologically, with agents that impair AV nodal conduction directly and/or by increasing parasympathetic/sympathetic balance, or by modifying or ablating the A V nodal region anatomically. Rhythm control may be achieved by electrical or pharmacologic conversion followed by maintenance of sinus rhythm by pharmacologic (or occasionally ablative) therapies. This article will present current approaches to rate and rhythm control issues in atrial fibrillation. Parts 1 and 2, published previously, dealt with rate control and with the restoration of sinus rhythm. Part 3, the current article, details the selection process of choosing a therapy to maintain sinus rhythm, including the likelihood of success, the risks of therapy, and individualization of therapy as dependent upon the nature of the structural heart disease present. It also discusses nonpharmacologic approaches that have been recently developed or are undergoing development. One suggested drug selection algorithm is provided.
Long‐Term Memory Monitoring in Infant Tachycardias
Authors: ECKERD JOHN M. , ALLEY KATHY , VOGELBACH DALE
Published: July 2006

Evaluation and detection of pathological tachycardias in infants sometimes is difficult. Noninvasive recording of the infant's ECG at the time of symptoms forms the mainstay of diagnosis, although invasive electrophysiological testing may be required. Accurate rhythm diagnosis is central to successful treatment. The advent of high capacity ambulatory memory monitoring makes it possible to record ECG signals, as well as apnea data. We present two cases of infant tachycardia studied by memory monitor. These devices yield good quality ECG signals and may provide information regarding a particular rhythm disturbance.
Atrial Fibrillation and Anticoagulation in Patients with Permanent Pacemakers: Implications for Stroke Prevention
Authors: SPARKS PAUL B. , MOND HARRY G. , KALMAN JONATHAN M. , JAYAPRAKASH SHENTHAR , LEWIS MICHAEL A. , GRIGG LEEANNE E.
Published: July 2006

Several large prospective randomized trials have demonstrated that anticoagulation with warfarin reduces the risk of thromboembolic stroke in high risk patients with chronic AF by approximately 70%. Large numbers of patients with permanent pacemakers have AF, and anticoagulation rates in this population have not been described. In a prospective analysis of 110 consecutive patients attending the pacemaker clinic of a large university hospital, we assessed the number of patients with AF and the proportion of these patients who were receiving anticoagulation to prevent thromboembolic stroke. Where necessary, temporary pacemaker reprogramming to low ventricular rates was utilized to facilitate the diagnosis of AF. Fifty‐three of the 110 patients (48%) were diagnosed with AF, all of whom (100%) had accepted high risk factors for thromboembolic stroke. Only eight of the 53 (15%) had been anticoagulated with warfarin. Thirty‐six of the 53 patients (68%) diagnosed with AF had no prior documented diagnosis of chronic AF, and the majority had no symptoms suggesting AF. A single lead II ECG was insufficient in 67 of the 110 patients (61%) to diagnose the underlying atrial rhythm; the remainder required 12‐lead ECGs or temporary pacemaker reprogramming to low ventricular rates to diagnose the underlying atrial rhythm. AF is common in patients with permanent pacemakers. It is commonly asymptomatic, and anticoagulation is markedly underutilized in reducing stroke risk in these patients. Attention to the possibility of AF in paced patients should allow prompt diagnosis and allow both the initiation of anticoagulation in order to reduce thromboembolic stroke risk and consideration for cardioversion of AF to sinus rhythm.
Effect of Atrioventricular Sequential Pacing on Left Ventricular Flow Dynamics in a Patient with Mid‐Ventricular Obstruction
Authors: TAKEUCHI MASAAKI , ABE HARUHIKO , KUROIWA AKIO
Published: July 2006

The effect of dual chamber atrioventricular sequential pacing on the intraventricular pressure gradient was tested using Doppler echocardiography in a patient with hypertrophic mid‐ventricular obstruction. Atrioventricular sequential pacing with relatively short atrioventricular delays reduced in the left ventricular pressure gradient at the mid‐ventricular level. Also, atrioventricular sequential pacing affected the degree and profile of the isovolumetric relaxation flow. These results suggest that atrioventricular sequential pacing affects both systolic and diastolic left ventricular flow dynamics in mid‐ventricular obstruction.
Paroxysmal Atrial Flutter Suppressed by Repair of a Large Paraesophageal Hernia
Authors: SCHILLING RJ. , KAYE G.C.
Published: July 2006

We present a case of recurrent atrial flutter resistant to medical therapy in a patient with an associated paraesophageal hernia, repair of which has produced suppression of the clinical arrhythmia for over one year.
Multiple Inappropriate Shocks Precipitated by Interrogation of an Implantable Cardioverter Defibrillator
Authors: HUNN RICHARD H. , ASHBAUGH TIMOTHY J. , CALDERINI MARK , ANDERSON KELLEY P.
Published: July 2006

A 57‐year‐old man suffered multiple inappropriate shocks from an implantable cardioverter defibrillator that could not be inactivated because the magnet switch feature was deactivated. Attempts to interrogate the defibrillator caused shocks to be delivered. Emergent explantation was performed and a loose sensing lead was discovered. Sensing and defibrillation leads functioned normally, and testing of the explanted generator demonstrated no abnormalities. A new generator was put in place and the patient has been without shocks for 6 months. This case illustrates the need for robust methods of attenuating electromagnetic interference and the importance of multiple methods of device inactivation.
Recipient to Donor Conduction of Atrial Tachycardia Following Orthotopic Heart Transplantation
Authors: LAI WALLACE , KAO ANDREW , SILKA MICHAEL J. , HALPERIN BLAIR D. , RAITT MERRITT , OLIVER RONALD , McANULTY JOHN H. , KRON JACK
Published: July 2006

We report a case of atrial tachycardia in a 60‐year‐old male 8 years postorthotopic heart transplantation. At electrophysiology study, the clinical rhythm was found to arise from the remnant of the recipient atrium and was successfully terminated by delivery of radiofrequencv energy. Surgical scars formed at the anastomosis of the recipient and donor atrium during the time of orthotopic heart transplantation are thought to electrically isolate the two areas. Although rarely recognized, dysrhythmias originating from the recipient atrial remnant may occur more often than previously thought.
Chronic Performance of a Transvenous Steroid Pacing Lead Used as an Epi‐Intramyocardial Electrode
Authors: KARPAWICH PETER P. , WALTERS HENRY , HAKIMI MEHDI
Published: July 2006

Excessive surface fibrosis or fat limits effective electrode insertion in patients requiring epicardial pacing. We present chronic performance of a modified transvenous steroid lead used as an epi‐intramyocardial electrode in a patient following repair of a univentricular heart after failure of both standard and steroid‐eluting epicardial leads. Low implant threshold values remained stable during a 3‐year postimplant interval demonstrating an effective and innovative approach to epicardial pacing.
Laparoscopic Hernia Repair of an Incisional Hernia Secondary to Placement of an Implantable Cardioverter Defibrillator
Authors: LAWTON JENNIFER S. , EMBREY RICHARD P. , DeMARIA ERIC J.
Published: July 2006

We present the lapamscopic repair of a large incisional hernia secondary to placement of a subcostal ICD pulse generator. Laparoscopic repair of large incisional hernias provides a unique and technically feasible form of repair in the 2%–13% of patients who will develop an incisional hernia following an abdominal surgery. This form of hernia repair is associated with minimal morbidity and prompt resumption of patient activities and work.