bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐Term Survival of Chosen Atrial‐Based Pacing Modalities
Authors: IRWIN MARLEEN , CARBOL BONNIE , SENARATNE MANO , GULAMHUSEIN SAJAD
Published: July 2006

Atrial‐based cardiac pacing modalities were chosen in 341 of 684 (50%) patients selected for permanent cardiac pacing at the Grey Nuns Community Health Center between 1989 and 1995. There were 183 males and 158 females. Mean age was 70 years (range 8–97 years). The indications for atrial‐based pacing were: advanced atri‐ oventricular (AV) block (n = 166) 49%; sick sinus syndrome (n = 153) 45%; hypersensitive carotid sinus syndrome (n = 11) 3%; neurocardiac syncope (n = 10) 2.9%; and hypertrophic cardiomyopathy (n = 1) 0.3%. Forty‐eight patients had a known history of paroxysmal atrial arrhythmias. All patients had routine follow‐up performed at 24 hours, 7 days, 6 weeks, 3 months, and then 6 biannuallv. Mean follow‐up was 6.5 years (range 1 month to 12 years). Observed survival of the programmed atrial‐based modality was compared to the original mode chosen at the time of implantation. Thirty‐five of 37 (95%) chosen for AAIR modes remain programmed AAIR. Twenty‐two of 24 (92%) chosen for VDDR modes remain programmed VDDR. Two hundred and fifty‐five of 280 (91 %) chosen for DDD or DDDR modes remain programmed DDDR. Two of 37 (5%) patients originally implanted with AAI pacing systems were upgraded to DDDR mode due to new onset AV block. One of 24 (4%) patients originally implanted with a VDDR pacing system was upgraded to DDDR due to loss of atrial sensing of the single pass lead. Twenty‐six of 304 (8.5%) patients originally implanted with DDD/DDDR (n ‐ 25) and VDDR (n = 1) pacing systems were reprogrammed to VVI or WIR: 16 (62%) due to sustained refractory atrial arrhythmias; 5 (19%) due to atrial lead malfunction; and 5 (19%) due to reasons unrelated to the pacing system. With careful review of the patients' conduction disorder and appropriate selection of pacing modality, the observed survival of long‐term atrial‐based pacing remains at 92% when compared to the chosen modality at the time of implantation. Atrial‐based pacing may be used to reduce the incidence of atrial dysrhythmia with careful programming of the base atrial pacing rates.
Clinical Significance of a New P Wave Lead Vector for Pacemaker Follow‐Up of Atrial Functions
Authors: LU RICHARD M.T. , STEINHAUS BRUCE M. , BAILEY WILLIAM , NADEMANEE KOONLAWEE
Published: July 2006

Patient welfare requires routine follow‐up procedures of implantable pacemakers. However, the assessment of atrial sensing and pacing functions in implantable pacemakers is often a challenge due to difficult identification of low amplitude P waves on surface electrocardiograms (ECGs). A previous body surface mapping study suggested that a novel P wave lead vector (P lead) had larger root mean square values than other standard leads. However, for pacemaker follow‐up procedures, peak‐to‐peak amplitudes are more relevant than root mean square values. In this study, the peak‐to‐peak amplitudes of intrinsic and paced P waves recorded from surface ECG standard lead II and the P lead were compared. In addition, intrinsic and paced R waves were also compared. Data recorded from 15 patients undergoing electrophysiological studies indicated that peak‐to‐peak amplitudes of the P lead were significantly larger than standard lead II: 24% for intrinsic P waves, 30% for paced P waves, and 72% for intrinsic R waves. In addition, the P lead amplitude of paced R waves showed a nonsignificant increase of 24% compared with standard lead II. Therefore, the use of this new lead vector may improve the clinical ease‐of‐use and reduce the time required for follow‐up procedures of implantable pacemakers for atrial sensing and pacing assessments.
Automatic Sensor Adjustment in a Rate Modulated Pacemaker
Authors: GENTZLER RICHARD D. , LUCAS ERIC H. ,   NORTH AMERICAN TRILOGY DR+ PHASE I CLINICAL INVESTIGATORS
Published: July 2006

A new feature (AutoSlope) has been introduced that can automatically adjust the sensor slope based on the chronic activity level of the patient. The algorithm adjusts the slope once per week so that 99% of the sensor response is maintained between the base rate and 23% of the difference between the programmed Base Rate and the Max Sensor Rate. Offsets are available for fine titration of sensor response in individual patients. The AutoSlope feature was evaluated in 93 patients with DDDR pacemakers (Trilogy DR+, Pacesetter). Patients were seen at 1, 3, and 6 months for a total of 178 evaluations. At each evaluation, the AutoSlope value was recorded. Patients then performed a brisk walk at sensor values equivalent to the AutoSlope value. Desired sensor rate was compared to the rate achieved by AutoSlope for the exercise period. Long‐term sensor performance was evaluated by analyzing the sensor histogram. AutoSlope provided the desired sensor rate in most patients. Use of AutoSlope offsets allows fine titration of rate modulation in individual patients. Ongoing changes in sensor performance provided by AutoSlope allow patients to achieve a desired sensor rate from one evaluation to another without changes in permanent programmed settings. Programming a low maximum sensor rate may limit sensor response in some patients.
Present Day Pacemakers for Pulse Generator Exchange: Is 3.5 V a Sufficient Nominal Setting for the Pulse Amplitude?
Authors: SCHUCHERT ANDREAS , VAN LANGEN HERMAN , MICHELS KOEN , MEINERTZ THOMAS ,   THE THERA PACEMAKER STUDY GROUP
Published: July 2006

Projected pacemaker longevity is calculated according to the nominal setting, which is 3.5 V for pulse amplitude in most present day pacemakers. The aim of this study was to test whether the nominal ventricular output setting of 3.5 V and 0.4 ms provides a 100% safety margin if these pacemakers are connected to implanted ventricular pacing leads. The study included 24 patients undergoing pulse generator exchange. The new pacemaker was either a Thera DR (n = 21) or Them SR (n = 3) device. Ventricular pacing leads were implanted 70 ± 38 months previously. Intraoperative measurements included pacing threshold at 0.5‐ms pulse duration, impedance, and R wave amplitude. To achieve a 100% safety margin with 3.5 V, the cut‐off pacing threshold is 1.7 V. At discharge it was assessed whether ventricular pulse amplitude remained at > 3.5 V or was programmed to > 3.5 V. At pulse generator exchange, pacing threshold was 1.2 ± 0.5 V, including four patients with pacing thresholds > 1.7 V. Impedance was 587 ± 189 Ω and R wave amplitude was 12.8 ± 4.8 mV. At discharge, ventricular pulse amplitude remained at the nominal setting in 13 patients, including 2 patients with high pacing thresholds at pacemaker exchange, and was programmed to < 3.5 V in 7 patients. Ventricular pulse amplitude was programmed to > 3.5 V in four patients. Two of these patients had high pacing thresholds (> 1.7 V/0.5 ms) at pulse generator exchange; the other two patients were programmed to > 3.5 V, although 3.5 V already provided a 100% safety margin. After pulse generator exchange, 92% of the patients could be paced with a 3.5‐ V pulse amplitude. Pacemakers were programmed in four patients > 3.5 V, but in only two of them to obtain a sufficient safety margin. High pacing thresholds at pulse generator exchange did not generally predict high pacing thresholds at discharge.
Activated Pyrolytic Carbon Tip Pacing Leads: An Alternative to Steroid‐Eluting Pacing Leads?
Authors: MASINI MICHELE , LAZZARI MAURO , LORENZONI ROBERTO , DOMICELLI ANNA MARIA , MICHELETTI AGNESE , DIANDA RENZO , MASINI GIUSEPPE
Published: July 2006

Pyrolytic carbon technology is known for its excellent mechanical properties and electrical conductivity; it is particularly biocompatible and does not require high production costs. The Sorin S100/4 lead is a ventricular passive fixation lead with a hemispherical electrode surface area of 4 mm2; the stimulating tip is made of a graphite core coated by a thin activated pyrolytic carbon layer. We evaluated the acute and medium‐term performance of the unipolar version of this lead in 65 patients. At implantation, pacing threshold (at 0.5 ms) was 0.26 ± 0.08 V; pacing impedance (at 5 V and 0.5 ms) was 537 ± 94 Ω and Ft wave amplitude was 15.0 ± 5.5 mV. No lead related complications (dislodgment, perforation, exit block, etc.) occurred in any patient; one patient presented with a wire fracture after 26 months, due to subclavian crush syndrome. Follow‐up procedures were performed at 1 week, and 2‐, 10‐, 18‐, and 30‐months postimplant. Since the leads were connected to pacemakers from different manufacturers, either voltage or duration thresholds were measured, In approximately two thirds of the patients, with an output of 2.5 V, a mean duration threshold of 0.16 ± 0.13 ms at 1 week, 0.12 ± 0.08 ms at 2 months, 0.11 ± 0.06 ms at 10 months, 0.09 ± 0.06 ms at 18 months, and 0.07 ± 0.03 ms at 30 months, was measured. In the remaining one‐third of the patients, a comparable voltage threshold trend was measured. The mean pacing impedance showed a transient drop at 1 week, and then increased to a plateau of about 600 fl reached after 10 months. No sensing defect occurred in any patient. Our data show good acute and intermediate‐term results of the S100/4 lead; the early rise in threshold was remarkably blunted. Activated pyrolytic carbon tip leads might therefore be considered as a possible, inexpensive alternative to steroideluting leads.
Lithium/Carbon Monofluoride (Li/CFx): A New Pacemaker Battery
Authors: GREATBATCH WILSON , HOLMES C.F. , TAKEUCHI E.S. , EBEL S.J.
Published: July 2006

The reduction in pacemaker size coupled with the addition of more current demanding functions has motivated the development of batteries that can supply higher current densities at useful voltages than the lithium/iodine batteries in use today while retaining the volumetric energy density of that system. The lithium/CFx system offers an attractive alternative for advanced pacemaker systems. The battery can deliver currents in the milliampere range without significant voltage drop. The system is compatible with titanium casing, allowing a 50% reduction in weight over the same size lithium/iodine battery. Cells have been designed and tested in these laboratories and have been shown to be suitable for advanced pacemaker applications.
Is There Increased Sympathetic Activity in Patients with Mitral Valve Prolapse?
Authors: KOCHIADAKIS GEORGE E. , PARTHENAKIS FRAGISKOS I. , ZURIDAKIS EMMANUEL G. , ROMBOLA AMALIA T. , CHRYSOSTOMAKIS STAVROS I. , VARDAS PANOS E.
Published: July 2006

The aim of this study was to investigate autonomic nervous system tone in patients with mitral valve prolapse (MVP). Heart rate variability (HRV) was assessed from 24‐hour ambulatory Holter recordings in 28 patients with primary MVP and in 28 age and sex matched normal control subjects in a drug‐free state. Sixteen of the MVP patients were symptomatic and 12 asymptomatic. Spectral HRV was calculated in terms of low (LF: 0.06–0.15 Hz) and high (HF: 0.15–0.40 Hz) frequency components using fast Fourier transform analysis, and the ratio LF/HF was calculated. Spectral analysis of HRV showed that the MVP patients, taken as a single group, had lower HF and LF and a higher LF/HF ratio than the controls. No significant difference in HRV was found between the 16 symptomatic and the 12 asymptomatic patients, but the symptomatic patients had a significantly higher LF/HF ratio than the controls. Our observations suggest that, during normal daily activities, patients with MVP experience a significant deviation in autonomic nervous system tone with predominance of the sympathetic branch. This predominance is more marked in symptomatic patients.
Spatial Distribution of QT Intervals: An Alternative Approach to QT Dispersion
Authors: VAN LEEUWEN PETER , HAILER BIRGIT , WEHR MICHAEL
Published: July 2006

QT dispersion (QTd) describes the heterogeneity of ventricular repolarization on the basis of the temporal range of QT intervals as measured in the 12‐lead ECG. We examined the spatial distribution of QTd using multichannel magnetocardiograms (MCGs), which noninvasivety register changes in magnetic field strength at 37 sites over the heart. As in ECG, the MCG signal in each channel may be used to measure QT interval. By calculating QT deviation from QTmin at each site, one can reconstruct the spatial distribution of QTd. Analysis of spatial QTd in ten healthy subjects and ten patients after acute myocardial infarction (MI) showed clear differences in spatial distribution. The healthy subjects generally displayed shorter QT intervals along a line corresponding to the approximate position of the septum with longer intervals in plateaus in the upper right and lower left. Spatial QTd of the post‐MI patients deviated from this pattern, often displaying a sharp rise in QT duration over specific areas, which could be related to functional and morphological disturbances. The quantification of local irregularities as well as the overall pattern on the basis of a smoothness index allowed better discrimination between healthy subjects and post‐ MI patients than QTd. Distribution patterns of QTd which reflect local repolarization alterations may thus represent a more differentiated marker for pathology and risk.
Atrial Flutter: Lessons from Surgical Interventions (Musing on Atrial Flutter Mechanism)
Authors: GUIRAUDON GERARD M. , KLEIN GEORGE J. , van HEMEL NORBERT , GUIRAUDON COLETTE M.‐J. , de BAKKER JACQUES M.T.
Published: July 2006

We report our experience with seven patients who underwent direct surgical ablation of problematic common flutter. Intraoperative mapping was obtained in four patients. Surgical techniques varied over time. A circular incision of the right atrium was performed in the first patient. Two patients had epicardial cryoablation of the isthmus between the inferior vena cava and the tricuspid valve annulus. Four patients had extensive endocardial cryoablation of the isthmus. There were no immediate postoperative complications. One patient had atrial fibrillation 2 months postoperatively and underwent a corridor operation 1 year later. The other six patients are free of arrhythmias without antiarrhythmic drugs. Surgical ablation confirmed that the common form of atrial flutter is associated with a right atrial macroreentrant circuit. One of our intraoperative endocardial maps suggested that variant reentrant circuits can be associated with variant forms of flutter.
Type II Atrial Flutter Interruption with Transesophageal Pacing: Use of Propafenone and Possible Change of the Substrate
Authors: DONI FLAVIO , STAFFIERE ELIO , MANFREDI MARGHERITA , PIEMONTI CARLO , TODD SARAH , RIMONDINI ANDREA , FIORENTINI CESARE
Published: July 2006

Type II atrial flutter (AFII) is an arrhythmia which usually cannot be interrupted by atrial pacing: the underlying mechanism is considered to be a leading circle without an excitable gap. We investigated whether the administration of propafenone, an antiarrhythmic drug, which primarily decreases conduction velocity, has a beneficial effect on AFII interruption using transesophageal pacing. Twelve patients with an AFII were randomized into 2 groups in which pacing was performed without treatment (group A) or two hours after the administration of 600 mg of oral propafenone (group B). Sinus rhythm was attained in 0 of 6 patients in group A and in 4 of 6 patients in group B (P < 0.05). The baseline mean cycle length was the same in both groups (175 ± 7 (A) vs 168 ± 8 ms (B); it lengthened significantly after the administration of propafenone (219 ± 33 vs 168 ± 8 ms; P < 0.05). Propafenone did not significantly lengthen the cycle in the two patients in whom interruption of the arrhythmia was impossible. Our data show that propafenone has a facilitating effect on atrial pacing only when it significantly prolongs the cycle length of the arrhythmia, possible expression of a conversion of AFII into type I, with an anatomical substrate and an excitable gap allowing arrhythmia capture and interruption. In the two patients in whom sinus rhythm was not restored, the absence of a direct dependence of the cycle length on the change in conduction velocity induced by propafenone may be explained by the persistence of a functionally determined circuit, resistant to atrial pacing.
Shortcut Link Between the Fast and Slow Pathways and the Mechanism of Cure in Atrioventricular Nodal Reentrant Tachycardia by Catheter Ablation
Authors: NOGAMI AKIHIKO , TAKAHASHI ATSUSHJ , NAITO SHIGETO , TSUCHIO YASUHIRO , OSHIMA SHIGERU , TANIGUCHI KOICHI , NITTA JUN‐ICHI , AONUMA KAZUTAKA , IESAKA YOSHITO
Published: July 2006

The mechanism of cure in AV nodal reentrant tachycardia (AVNRT) by catheter ablation has not been fully clarified. We hypothesized that disruption of a shortcut link between the fast and slow pathways is responsible for the elimination of tachycardia. Results: AVNRT was eliminated in 20 patients by catheter ablation. In five patients (25%; group 1) slow pathway conduction disappeared 1 week after ablation. In six patients (30%; group II), the effective refractory period of the slow pathway was prolonged by more than 50 ms (212 ± 81 ms vs 340 ± 81 ms; P < 0.05). In the remaining nine patients (45%; group III), there was no change in the refractory period (270 ± 65 ms vs 273 ± 74 ms), although tachycardia was not inducible. A shortcut link between the fast and slow pathways was examined by comparing the A‐H intervals over the slow pathway during the tachycardia and during atrial pacing at the tachycardia cycle length. Prior to ablation, a shortcut link was assumed in 1 of group I patients, 2 of group II patients, and 8 of group III patients. Of the 9 patients in whom the slow pathway was not impaired after ablation (group III), 8 patients were found to have a shortcut link, while 8 of 11 patients with impairment of the slow pathway after ablation (groups I and II) had no shortcut link between the fast and slow pathways (P < 0.05). Conclusion: In patients with a shortcut link between the fast and slow pathways, slow pathway conduction itself does not need to be impaired to eliminate the AVNRT, whereas in patients without this shortcut link, slow pathway conduction must be impaired.
Mapping Reentry Around Atriotomy Scars Using Double Potentials
Authors: CHINITZ LARRY A. , BERNSTEIN NEIL E. , O'CONNOR BRIAN , GLOTZER TAYA V. , SKIPITARIS NICHOLAS T.
Published: July 2006

Supraventricular arrhythmias, often seen in patients after cardiac surgery, may be associated with scars produced in the atria at the time of surgery. Double potentials, found in the presence of functional or anatomical block, can define the limits and critical regions of a reentrant circuit associated with the atriotomy scars. We describe six patients with seven distinct atrial tachycardias in whom atriotomy scars were successfully mapped during intraatrial reentry utilizing the presence and interelectrogram relationship of observed double potentials. The reentrant circuit was mapped in all patients by following the relationship between double potentials along the surgical scar, assuming that they would be widely split in the middle of the scar and merge into a single continuous fractionated potential at the apex of the scar. At this site, atrial pacing was performed to entrain the tachycardia and confirm the participation of the atriotomy scar in the clinically relevant atrial tachycardia. Radiofrequency ablation was performed from the site of electrogram fusion to the nearest anatomical obstacle. Five of seven atrial tachycardias were successfully ablated utilizing this technique over a mean follow‐up of 10 months. We proposed that these double potentials and their interelectrogram relationship are an effective means of mapping atriotomy scars and guiding successful radiofrequency ablation.
Electrocardiographic Identification of Mid‐Septal Accessory Pathways in Close Proximity to the Atrioventricular Conduction System
Authors: LORGA F° ADALBERTO , SOSA EDUARDO , SCANAVACCA MAURICIO , D'AVILA ANDRÉ , KUNIYOSHI RICARDO , de HORTA JOSÉ , FENELON GUILHERME , BRUGADA PEDRO
Published: July 2006

In order to identify ECG characteristics of overt midseptal accessory pathways (APs) predictive of close proximity to the AV conduction system we analyzed data from patients who underwent successful RF catheter ablation of a mid‐septal AP, Mean patient age was 31 ± 16 years, and 13 were male. The 40° right anterior oblique view was used to divide the mid‐septal area into 3 zones: 1 (anteriorportion); 2 (intermediate); and 3 (posterior portion). The 12‐lead ECG was analyzed with regard to delta wave polarity and R/S transition in the precordial leads. The findings from patients ablated at zone 3 were compared to those at zones 1 and 2. All patients had a positive delta wave in the leads I, II, aVL, and negative delta wave in the leads III and aVR. The R/S transition occurred in lead V2 in 80% of patients. The delta wave in lead aVF was the only ECG characteristic that correlated with the AP ablation zone. Six of 8 patients ablated at zone 3 had a negative delta wave in lead aVF while 6 out of 7 patients ablated at zone 1 or 2 had a positive or isoelectric delta wave in lead aVF (P = 0.03). A positive or isoelectric delta wave in lead aVF identifies mid‐septal AP in close proximity to the AV conduction system.
In Vitro and In Vivo Results of Transcatheter Microwave Ablation Using Forward‐Firing Tip Antenna Design
Authors: LIEM L. BING , MEAD R. HARDWIN , SHENASA MOHAMMAD , KERNOFF ROBERT
Published: July 2006

This study was designed to test a microwave (MW) ablation system using approximately 2,450 MHz of energy and a deflectable catheter with forward‐firing tip antenna, an early clinical prototype system. In vitro three‐dimensional thermal mapping of single and double helix antenna designs was performed. Quantitative measurements of antenna radiation were recorded on tissue phantoms equipped with temperature sensors distributed radially and outwardly. In vivo testing consisted of closed‐chest AV junction ablation in three dogs. Thermal mapping showed hemispherical heat distribution from the tip antenna. For the double helix design, this distribution was measured at 8,4‐mm diameter with a maximum temperature of 61.62°C. As expected, the single helix design produced less heating with a measured diameter of 6.4 mm and maximum temperature of 55.90°C. The in vivo study produced lesions of geometry and size concordant with these heating patterns. MW ablation produced bundle branch block in one dog and complete AV nodal block in the remalning two, without transvalvular or other structural damage. The histopathology of the lesions was typical of a thermal burn showing hemorrhage and coagulative necrosis with clearly demarcated borders. We conclude that, using this early clinical prototype system with a deflectable catheter and a forward‐firing tip antenna design, MW heating can produce a moderate‐size lesion and is safe and effective for cardiac ablation.
Role of Na+‐H+ Exchange on Reperfusion Related Myocardial Injury and Arrhythmias in an Open‐Chest Swine Model
Authors: FUKUTA MOTOYUKI , WAKIDA YASUSHI , IWA TORU , UESUGI MICHITAKA , KOBAYASHI TADASHI
Published: July 2006

The inhibition of Na+‐H+ exchange (NHE) with amiloride analogues in vitro has been shown to prevent reperfusion arrhythmias and additional cell necrosis. Inhibition of intracellular Ca2+ overload via NHE inhibition has been suggested as a mechanism of these protective effects. The aim of this study was to examine whether treatment with amiloride analogues reduces the incidence of reperfusion arrhythmias and limits infarct size in vivo. Open‐chest swine were exposed to a 30‐minute left anterior descending artery (LAD) occlusion and 180 minutes of reperfusion during atrial pacing at 150 ppm. Intravenous 5‐(N,N‐dimethyI)‐amiloride (AML, 5 μg/kg per min) was administered in the treatment group (n = 7) and intravenous saline in the control group (n = 7), starting 10 minutes before coronary occlusion. The infusion was continued during ischemia and reperfusion. The area at risk was defined by monastral blue dye and infarct size by triphenyltetrazolium chloride staining. Limb leads ECG and monophasic action potentials (MAPs) from the epicardium in the ischemic area were recorded. There was no significant difference in the size of the area at risk and hemodynamic parameters between the groups. However, the infarcted area was 0.4%± 1.0% of the area at risk in the treatment group, whereas it was 62%± 29% in the control group (P < 0.05). Pathological examination (Hematoxylin‐eosin and mallory s phosphotungstic acid‐hematoxylin staining) revealed that all of the infarcted area consisted of contraction band necrosis. MAP duration in both groups was significantly shortened during ischemia. After reperfusion, MAP duration in the treatment group recovered earlier than that of control group. However, there was no significant difference in the incidence of ventricular tachyarrhythmia between the groups. Inhibition of NHE with AML prevented reperfusion related cell necrosis in the in vivo swine model, but did not reduce the incidence of ventricular tachyarrhythmia.
A New Contact Probe for Intraoperative Laser Ablation
Authors: OHTAKE HIROSHI , WATANABE GO , MISAKI TAKURO , MATSUNAGA YASUHIRO , TAKAHASHI MASAO , TSUNEZUKA YOSHIO , KAWASUJI MICHIO , WATANABE YOH
Published: July 2006

Several clinical factors decrease the accuracy of intraoperative laser ablation. The distance to the target, the irradiation angle, and the media are reported among these factors. We developed a new laser probe to resolve these problems. This probe has a hollow conical tube with a tip covered by a thin film. Zero‐degree centigrade saline was fed into this probe. Results from using the new probe were compared with those from the conventional noncontact irradiation method with cooling by sprinkled cooling water. In beating canine hearts, ventricles were irradiated with neodymium‐yttrium aluminum garnet (Nd:YAG) lasers at 50–200 //mm2. There was no difference in the mean volume of irradiated tissue between the new and the noncontact method. However, the distribution of volume values in the new method was smaller than that in the noncontact method (P < 0.05). In conclusion, results obtained indicate that this new probe could perform more accurate intraoperative ablation than the conventional method. Problems of stabilizing the distance to the target, the irradiation angle, and the media were resolved.
Initial Single‐Center Experience with an Advanced Third‐Generation Investigational Defibrillator
Authors: LAMPERT RACHEL , ROSENFELD LYNDA , McPHERSON CRAIG , LEWIS RICHARD , VANZETTA ALICE , BATSFORD WILLIAM
Published: July 2006

The CPI PRxII is a recently approved, multitiered implantable cardioverter defibrillator (ICD) that delivers high and low energy biphasic shocks, antitachycardia (ATP) and bradycardia pacing, and stores 2.5 minutes of electrograms from the widely spaced shocking electrodes. The PRxII was implanted in 58 patients at Yale‐New Haven Hospital between December 1993 and January 1995. At implant, mean biphasic defibrillation threshold (DFT) in patients with testing to failure was 10 J (1–20). All 36 patients who were candidates for a new transvenous system underwent successful nonthoracotomy implantation. Based on noninvasive predischarge EPS results, 30 patients had ≥ 1VT zone: 21 patients had ATP, 9 others had first shock ≤ 5 J. During follow‐up, 13 patients had been treated for 379 events (range, 1–127). Of 340 events in a zone with ATP, 97% responded to ATP, 3% required shock. First programmed shock converted all events in a VF zone. Details, including RR intervals, were available for ail events in 15 of 17 patients receiving appropriate or inappropriate therapy or diverted shocks. One hundred eleven of 148 available electrograms confirmed VT by morphology, rate, and/or presence of AV dissociation. In nine patients, electrogram data altered therapy through diagnosis of inappropriate or diverted therapy, guidance of detection enhancements, or diagnosis of previously unrecognized VTs. We conclude the PRxII achieves low DFTs that obviate the need for thoracotomy and effectively treats ventricular arrhythmias with ATP and shock, with programming guided by noninvasive electrophysiology. Multiple stored electrograms from widely spaced shocking electrodes greatly enhance diagnostic capabilities, facilitating effective treatment.
Comparison of a Unipolar Defibrillation System with a Dual Lead System Using an Enlarged Defibrillation Anode
Authors: MATTKE SÖREN , FIEK MICHAEL , MARKEWITZ ANDREAS , MÜLLER DIETER , HOFFMANN ELLEN , SCHMÖCKEL MICHAEL , STEINBECK GERHARD
Published: July 2006

The unipolar system for transvenous defibrillation, consisting of a single right ventricular lead as the cathode and the device shell as anode, has been shown to combine low de‐ fibrillation thresholds (DFTs) and simple implantation techniques. We compared the defibrillation efficacy of this system with the defibrillation efficacy of a dual lead system with a 12‐cm long defibrillation anode placed in the left subclavian vein. The data of 38 consecutive patients were retrospectively analyzed. The implantation of an active can system was attempted in 20 patients (group 1), and of the dual lead system in 18 patients (group 2). Both groups had comparable demographic data, cardiac disease, ventricular function, or clinical arrhythmia. The criterion for successful implantation was a DFT of > 24 J. This criterion was met in all 18 patients of group 2, The active can system could not be inserted in 3 of the 20 group 1 patients because of a DFT > 24 J. In these patients, the implantation of one (n = 2) or two (n = 1) additional transvenous leads was necessary to achieve a DFT ≤ 24). The DFTs of the 17 successfully implanted group 1 patients were not significantly different from the 18 patients in group 2 (12.3 ± 5.7 f vs 10.8 ± 4.8 J). The defibrillation impedance was similar in both groups (50.1 ± 6.1 ± 48.9 ± 5.2 Ω). In group 1, both operation duration (66.8 ± 17 min vs 80.8 ± 11 min; P < 0.05) and fluoroscopy time (3.3 ± 2.1 min vs 5.7 ± 2.9 min; P < 0,05) were significantly shorter. Thus, the active can system allows reliable transvenous defibrillation and a marked reduction of operation duration and fluoroscopy time. The dual lead system, with an increased surface area defibrillation anode, seems to he a promising alternative for active can failures.
Transtelephone Monitoring for Pacemaker Follow‐Up 1981–1994
Authors: PLATT SIMIE , FURMAN SEYMOUR , GROSS JAY N. , ANDREWS CAROLYN , BENEDEK MICHAEL
Published: July 2006

Transtelephone monitoring (TTM) is capable of detecting pacemaker pulse generator malfunction, battery depletion, and lead failure. The accuracy of TTM was analyzed by a review of Montefiore Medical Center records between October 1981 and March 1994. Each group of transmissions from a single patient, starting with implant and ending with a pacemaker operation, was defined as a closed cycle (CLOSE), if undergoing continuing follow‐up at the time of analysis, as a continuing cycle (CONT), and if a cycle had ended with death or loss to follow‐up, an open cycle (OPEN). TTM records of 2,632 patients were analyzed, providing 3,291 cycles. There were 731 CONT, 433 CLOSE, and 2,127 OPEN cycles; 331 procedures were indicated by TTM. of which 279 were impending depletion, 30 sudden depletion, and 22 lead malfunctions. Of the 102 procedures not indicated by TTM, 85 were for nonurgent reasons (recall: 41; DDD upgrade: 16; patient/MD request: 28) and 17 for urgent reasons. In patients followed by TTM who had a lead problem, 22 were detected by TTM before clinical manifestations and 16 were not. There were no cases in which TTM follow‐ up did not detect battery depletion. The total number of TTM contacts, available for 3,094 cycles, was 88,654 (range, 1–163, median 19), of which 0.4% yielded a procedure. During the same period, 75% of all secondary interventions during the first 2 years occurred during the first 2 months after implant because of lead malfunction, with a subsequent SI rate of 0.005 per month for the third through the twenty‐fourth months.
Comparative Reproducibility of Defibrillation Threshold and Upper Limit of Vulnerability
Authors: SWERDLOW CHARLES D. , DAVIE SCOTT , AHERN TOM , CHEN PENG‐SHENG
Published: July 2006

The upper limit of vulnerability (ULV) is the strength at or above which VF is not induced when a stimulus is delivered during the vulnerable phase of the cardiac cycle. Previous studies have demonstrated a statistically significant correlation between the ULV and the defibrillation threshold (DFT) in groups of patients. However, the correlation between ULV and DFT may not be close in individual patients. This imperfect correlation may be due to physiological factors or to limitations of the measuremen t methods. The reproducibility of either DFT or ULV has not been studied critically. The purpose of this study was to compare the reproducibility of clinically applicable methods for determination of DFT and ULV. We prospectively studied 25 patients with a transvenous implantable cardioverter defibrillator (Medtronic 7219D) at postoperative electrophysiological study. DFT was defined as the lowest energy that defibrillated after 10 seconds of VF. The ULV was defined as the lowest energy that did not induce VF with three shocks at 0, 20. and 40 ms before the peak of the T wave in ventricular paced rhythm at a cycle length of 500 ms. Both the DFT and the ULV were determined twice for biphasic pulses using a three‐step, midpoint protocol. There was no significant difference between the two determinations of DFT (10.1 ± 5.9 J vs 10.4 ± 5.8 J), the two determinations of ULV (13.4 ± 6.8 J vs 13.8 ± 6.6) or the DFT‐ULV Pearson correlation coefficients for each determination (0.84, P < 0.001 vs 0.75, P < 0,001). To analyze reproducibility, Lin concordance coefficients for second determination versus first determination were constructed for both ULV and DFT. This coefficient is similar to the Pearson correlation coefficient, but measures closeness to the line of identity rather than the line of regression. The Lin concordance coefficient for ULV was higher than that for DFT (0.93, 95% CI 0.85–0.97 vs 0.64, 95% Cl 0.33–0.82; P < 0.01). For paired comparison of defibrillation efficacy under different experimental conditions, the sample sizes required to detect differences of 2 J, 3 J, and 4 J (80% power, P < 0.05) were 52, 24, and 15 for DFT versus 15, 8, and 6 for ULV. We conclude that a simple, clinically applicable method for determination of ULV is more reproducible than the single point DFT. Measured correlations between the ULV and single point are limited by the reproducibility of the DFT measurement.
Aspergillus Fumigatus Infection of an Automatic Internal Cardiac Defibrillator
Authors: DUNN CHRISTOPHER J. , RUDER MICHAEL , DERESINSKI STANLEY C.
Published: July 2006

We report a patient without immune compromise with infection of an automatic internal cardiac defibrilla‐ tor patch due to Aspergillus fumigatus presenting 8 years after implantation. The mechanism of infection was unknown, but symptoms began 1 month after laser uvulopalatopharyngoplasty was performed for sleep apnea. The patches were surgically removed and the patient was treated sequentially with amphotericin B and itraconazole. He remains without evidence of infection 12 months after the completion of therapy.
Comparison of Bipolar Atrial Electrogram Amplitude in Sinus Rhythm, Atrial Fibrillation, and Atrial Flutter
Authors: WOOD MARK A. , MOSKOVLJEVIC PREDRAG , STAMBLER BRUCE S. , ELLENBOGEN KENNETH A.
Published: July 2006

Automatic mode switching pacemakers revert to non‐atrial tracking modes in response to sensed atrial tachyarrhythmias. It is unclear how atrial electrogram amplitudes in sinus rhythm compare to those during atrial tachyarrhythmias. In this study, peak‐to‐peak bipolar atrial electrogram amplitudes were measured during sinus rhythm and either atrial fibrillation or atrial flutter in 69 patients. The mean atrial electrogram amplitudes were 1,59 ± 1.36 m V during sinus rhythm and 0.77 ± 0,58 mV during atrial fibrillation (P < 0.0001) for 25 patients with atrial fibrillation and 1.81 ± 2.07 mV during sinus and 1.5 ± 1.81 mV(P < 0.0001) for 44 patients with atrial flutter. The mean electrogram amplitudes during both atrial fibrillation and flutter correlated significantly with amplitudes during sinus rhythm (R = 0.79, R = 0.94. respectively, both P < 0,0001). The coefficient of variance of individual electrogram amplitudes was greater in atrial fibrillation than sinus (P < 0.0001). By comparing 20th percentile electrogram amplitudes in atrial fibrillation and flutter to mean sinus amplitudes, intermittent very low electrogram amplitudes (< 0.3 mV) were more likely during atrial fibrillation and flutter if the mean sinus electrogram amplitudes were < 1.5 mV and < 0.5 mV, respectively (P < 0.01). Eightieth percentile electrogram amplitude values in atrial fibrillation and flutter were equally likely to exceed mean sinus amplitude values in respective patients, in conclusion, mean atrial electrogram amplitudes during atrial fibrillation and flutter are less than but correlated to sinus rhythm electrogram amplitudes. Very low amplitude individual electrograms during these atrial arrhythmias are associated with low mean sinus rhythm electrogram amplitudes. These findings may have implications for the programming of permanent dual chamber pacemakers in patients with paroxysmal atrial fibrillation and flutter.
How to Measure AV Nodal Refractoriness in the Presence of Verapamil, Amiodarone, Digoxin, and Diltiazem
Authors: STARK GERHARD , KASPER KARIN , SCHULZE‐BAUER CHRISTIAN , STARK ULRIKE , DECRINIS MARTIN , TRITTHART HELMUT A.
Published: July 2006

On the AV node the negative dromotropic action of verapamil, amiodarone, digoxin, and diltiazem is known to be rate dependent. The effective refractory period of the AV node (AV‐ERP) at o short cycle length is related to the AV conduction at that cycle length. We investigated how the numher of stimuli during the conditioning train (S1) (during measurement of refractoriness at a high pacing rate [cycle length = 180 ms]) might influence the AV‐ERP in isolated guinea pig hearts in a Langendorff preparation. Verapamil (10 nM), amiodarone (10 μM), digoxin 10.G nM). and diltiazem (30 nM) caused a comparable prolongation of the AV conduction time (AVCT). All four drugs caused a significant prolongation of the AV‐ERP when evaluated by a standard stimulation protocol with a conditioning train of 10 stimuli (10 S1) at a pacing cycle length of 180 ms followed by the test stimulus (S2). When the number of stimuli during the conditioning train (SJ was increased (> 10), until the prolongation of AVCT reached steady state, the AV‐ERP in the presence of verapamil (132 ± 4 vs 141 ± 3 ms; P < 0.05. mean ± S.E.M.) and diltiazem (143 ± 3 vs 151 ± 3 ms; P < 0.05) was prolonged significantly further. These results indicate that the effect of drugs on AV‐ERP should be measured with a modified stimulation protocol, whereby the number of conditioning stimuli is comparable to the time constant characterizing the prolongation of AVCT at fast pacing rates.
Relative Efficacy of Different Tilts with Biphasic Defibrillation in Humans
Authors: NATALE ANDREA , SRA JASBIR , KRUM DAVID , DHALA ANWER , DESHPANDE SANJAY , JAZAYERI MOHAMMAD , NEWBY KEITH , WASE ABDUL , AXTELL KATHY , VANHOUT WARREN L. , AKHTAR MASOOD
Published: July 2006

Objective: The goal of this study was to assess if tilt bears any impact on defibrillation efficacy of biphasic shocks. Background: Although it has been shown that hiphasic waveform may increase the defibrillation efficacy, this pulsing method has not been as extensively studied in patients, and information regarding the effect of different tilts is lacking. Methods: This study consisted of two similar but distinct protocols including 33 patients undergoing transvenous defibriilator implant. In 17 patients (Part I) defibrillation threshold was obtained delivering biphasic waveforms with 50%, 65%, and 80% tilt in random fashion. Similarly, in 16 patients (Part II) testing of biphasic waveform with 40%, 50%, and 65% tilt was performed in random order. The electrode system used consisted of two transvenous leads and a subcutaneous patch in all 33 patients. Results: In Part I, tilt of 50% demonstrated a defibrillation threshold significantly lower than 65% tilt (7.5 ± 4.3 J vs 9.7 ± 5.0 J; P = 0.04) and 80% tilt (7.5 ± 4.3) vs 11.7 ± 5.9 J; P < 0.01). Similarly, 65% tilt provided a lower defibrillation threshold than 80% tilt (9.7 ± 5.0 J vs 11.7 ± 5.9 J; P = 0.02). In Part II, no significant difference was observed in terms of defibriilation threshold between 40% tilt and the two tilts of 50% and 65%. However, as in Part I, 50% tilt provided a significant reduction of the energy to defibrillate as compared to 65% tilt (6.3 ± 3.6 J vs 9.0 ± 4.8 J; P < 0.01). The 50% tilt resulted in better defibrillation efficacy than 65% tilt independent of the lead system used for testing (Medtronic Transvene and CPI Endotak‐C). Conclusions: Biphasic shocks with 50% tilt required less energy for defibrillation than 40%, 65%, and 80% tilts. However, in the clinical setting a programmable tilt may be preferable to account for some patient‐to‐patient variability.
Transesophageal Echocardiographic Guidance of Transseptal Left Heart Catheterization During Radiofrequency Ablation of Left‐Sided Accessory Pathways in Humans
Authors: TUCKER KELLY J. , CURTIS ANNE B. , MURPHY JAMES , CONTI JAMIE B. , KAZAKIS D. JAMES , GEISER EDWARD A. , CONTI C. RICHARD
Published: July 2006

Radiofrequency ablation (RFA) of left‐sided accessory pathways can be achieved using catheters introduced by a retrograde or transseptal approach. Transesophageal echocardiography (TEE) has previously been demonstrated to be safe and efficacious in guiding transseptal puncture in patients during mitral valvuloplasty (MV). This study was undertaken to assess the feasibility, safety, and clinical utility of TEE during transsepta! puncture and RFA of left‐sided accessory pathways. Methods: TEE was performed during transseptal puncture in 30 patients (41 ± 12 years, 19 females), 15 patients during attempted RFA of a left‐sided accessory pathway and 15 patients during attempted balloon MV. Results: There was no difference in age, sex distribution, or procedural complications when MV patients were compared to RFA patients. At baseline, left atrial dimension was increased and congestive heart failure was more common when MV patients were compared to RFA patients (P < 0.05) Adequate baseline two‐dimensional and Doppler TEE images were obtained in all patients. One patient sustained mild esophageal bleeding during the TEE, Positioning of the transseptal catheter in the fossa ovalis was facilitated and confirmed by TEE in 29 of 30 cases. One case of cardiac perforation occurred and was associated with inadequate TEE localization of the fossa ovalis. Thrombus was detected on the transseptal catheter by TEE in two cases prior to systemic heparinization. In both cases, thrombus was removed without embolic event. Conclusions: TEE safely guides transseptal puncture in patients undergoing RFA of left‐sided accessory pathways. TEE markers of the fossa ovalis facilitate puncture and may reduce the risk of cardiac perforation particularly in patients with a normal size left atrium. TEE may be especially valuable for identifying thrombus during transseptal puncture.
Dependence of Atrial Sensing Function on Posture in a Single‐Lead Atrial Triggered Ventricular (VDD) Pacemaker
Authors: TOIVONEN LAURI , LOMMI JYRI
Published: July 2006

The influence of body posture on atrial sensing was examined in a single‐lead VDD pacemaker in 16 patients. At implantation, a position was searched for the floating atrial bipolar sensor to obtain an adequate atrial signal amplitude. After 1–12 months the atrial signals were measured by programming the sensitivity in five postures: supine, sitting, and standing and lying on the right and left sides. The group mean amplitudes of the atrial signal were equal in all postures, and comparable to the supine value (1.01 ± 0.51 mV), However, the values within each individual varied considerably according to position, by a range of 0.46 ± 0.41 mV on average. Testing only supine did not always predict decent sensing when upright, e.g., in 3 patients the atrial signal decreased more than 0.5 mV. In 24‐hour ambulatory electrocardiography, with the sensitivity (0.15–0.30 mV) set to cover all postures, atrial beats were undersensed not at all in 4 patients, < 0.01% in 6 patients, and < 0.1% in the remaining 6 patients. Thus, with a floating atrial electrode, sensitivity testing in various postures is advisable to ascertain proper sensing function.
Atrioventricular Block Occurring Late After Heart Transplantation: Presentation of Three Cases and Literature Review
Authors: CATALDO RENZO , OLSEN STEPHANIE , FREEDMAN ROGER A.
Published: July 2006

Sinus node dysfunction is a well‐known occurrence following orthotopic heart transplantation, but atrioventricular block is rarely described. We compare the incidence and clinical presentation of atrioventricular block and sin us node dysfunction among the first 200 consecutive patients receiving heart transplantation at the University of Utah. Two of 200 patients (1%) required pacemaker implantation for symptomatic atrioventricular block compared to 13 of 200 (6.5%) who required pacemaker for symptomatic sinus node dysfunction. Of the patients with atrioventricular block, one had intermittent Mobitz II second‐degree atrioventricular block and one had high grade atrioventricular block without ventricular escape. The most striking difference between the patients with atrioventricular block and those with sinus node dysfunction was the interval between transplantation and pacemaker implantation; time to pacemaker implantation in the atrioventricular block patients was 955 and 810 days compared to a median time of 26 days for sinus node dysfunction patients (P = 0.037). The patients requiring permanent pacemaker implantation were similar to those not requiring pacemaker implantation with respect to age, sex, ischemic time, and donor age. None of the patients requiring permanent pacemaker implantation was on amiodarone therapy within 2 months of transplant.
Spontaneous Reversal of a Cardiomyostimulator to Asynchronous Mode
Authors: PETEIRO JESUS , STRUBLE CHESTER , VAZQUEZ NICOLAS , CASTRO‐BEIRAS ALFONSO
Published: July 2006

A patient who underwent dynamic cardiomyoplasty at our institute‐ 10 months earlier was recently found to have asynchronous function of his Cardiomyostimulator (model SP1005A, Medtronic, Inc.). This patient had been exposed to metal detection equipment 3 months earlier at an airport security gate, and this equipment was deemed responsible for this change in device programming. Despite the asynchronous function of the device, the patient did not suffer any functional impairment during this 3‐month period. Moderate electromagnetic interference is capable of resetting the SPl 005A Cardiomyostimulator to the asynchronous mode of operation. Muscle stimulation, therefore, will not precisely occur during the systolic phase of the cardiac cycle and systolic augmentation may be lost. Despite asynchronous muscle stimulation, no impairment of this patient's functional Class was observed. This stability may be credited purely to the effect of the muscular wrap around the ventricles in which ventricular wall stress is decreased.
Two Cases of Ventricular Parasystole Associated with Ventricular Tachycardia
Authors: ITOH EIICHI , AIZAWA YOSHIFUSA , WASHIZUKA TAKASHI , UCHIYAMA HIROHIDE , KITAZAWA HITOSHI , KUSANO YORIKO , NAITOH NAOKI , SHIBATA AKIRA
Published: July 2006

In two patients, ventricular pamsystole (VP) was associated with ventricular tachycardia (VT), and in one patient, catheter ablation was successful. In patient 1, with dilated cardiomyopathy, VP led to VT, which converted to ventricular fibrillation. In patient 2, VP led to symptomatic nonsustained polymorphic VT. The origin of parasystolic focus was determined byendocardial mapping, and a radiofrequency current was delivered to patient 2. Both VP and VT disappeared immediately, and no recurrence has been observed during a follow‐up of 8 months. Catheter ablation to the parasystolic focus was effective and a relationship between VP and VT was strongly suggested.