bluuebunny/crossref_metadata_2025 huggingface dataset:
Syncope Is Predicted by Neuromonitoring in Patients with ICDs
Authors: SINGER IGOR , DAWN BUDHA , EDMONDS HARVEY , STICKLAND TED J.
Published: July 2006

Decisions regarding ability of ICD patients to function in the work environment or at home are based primarily on subjective judgement. We have described noninvasive neuromonitoring techniques that are capable of characterizing cerebral blood flow and cerebral oxygen saturation in conscious patients during ventricular tachycardia (VT). Upright tilt testing (HUT) was used to predict the hemodynamic response to VT in the upright and recumbent posture. Sixteen patients (66 ± 8 years) with pace‐terminable VT and implanted ICD were tested during HUT with continuous measurement of arterial pressure, transcranial Doppler of the middle cerebral artery (TCD), and cerebral venous oxygen saturation (CVOS) determined noninvasively by applying a cutaneous patch with two infrared sensors from which a weighted venous percent oxygenated hemoglobin is continuously measured using INVOS 3100 (Somanetics). VT was induced via the implanted ICD and automatically terminated by ATP or cardioversion by the ICD, using the best treatment algorithm. HUT accentuated changes in cerebral blood flow and oxygen saturation and helped identify patients likely to experience syncope, whereas supine testing did not. These results suggest that HUT testing with noninvasive neuromonitoring is useful to predict ICD patients who are likely to remain conscious during VT.
Initial Experience with a New Balloon‐Guided Single Lead Catheter for Internal Cardioversion of Atrial Fibrillation and Dual Chamber Pacing
Authors: PLEWAN A. , VALINA C. , HERRMANN R. , ALT E.
Published: July 2006

Background: Based on the observation that internal cardioversion (IntCV) of atrial fibrillation is effective with electrodes in the right atrium and pulmonary artery, a new balloon‐guided catheter and external defibrillation device with optional dual chamber pacing was evaluated. Methods: IntCV was attempted in 27 patients (age: 57 ± 10 years, duration: 14 ± 18 months, left atrial diameter 56 ± 8 mm) using a new defibrillation device (Alert, EP MedSystems, Inc., NJ, USA) that allows the delivery of biphasic shocks (0.5–15 J, variable tilt), atrial and ventricular pacing, and online signal recording. Pacing and defibrillation shocks were applied via a 7.5 Fr balloon‐guided catheter (EP MedSystems, Inc.). Pacing, sensing, and triggering were established through the proximal atrial array and an electrode ring between both defibrillation arrays and a single ventricular electrode ring. Catheters were inserted from the antecubital vein. Results: In 25 of 27 patients sinus rhythm was restored with a mean energy of 6.7 ± 4.5 J. In five patients, atrial postshock pacing was required for bradycardia and atrial premature beats. The mean fluoroscopy time was 2.0 ± 1.3 minutes. Conclusion: The high success rate, ease of application, and backup dual chamber pacing suggest that this system is an alternative to established methods of cardioversion. In certain indications, such as failure of prior external cardioversion and situations in which a standard pulmonary balloon catheter is needed, this system would be advantageous.
Transvenous Atrial Cardioversion Threshold in Patients with Implantable Cardioverter Defibrillator: Influence of Active Pectoral Can
Authors: HEISEL ARMIN , JUNG JENS , NIKOLOUDAKIS NIKOLAUS , FRIES ROLAND , SCHÄFERS HANS‐JOACHIM , SCHIEFFER HERMANN
Published: July 2006

Recent studies have shown that transvenous atrial cardioversion is feasible with lead configurations primarily designed for implantable cardioverter defibrillators (ICD). The purpose of this study was to examine the influence of an active pectoral ICD can on the atrial cardioversion threshold (ADFT). Forty consecutive patients received a transvenous single lead system (Endotak DSP 0125, CPI, St. Paul, MN, USA) in combination with a left subpectoral ICD (Ventak Mini, CPI) for treatment of malignant ventricular tachyarrhythmias. Patients were randomized into two groups: 21 received a Hot Can 1743 and 19 patients a Cold Can 1741. Step‐down testing of the ventricular defibrillation threshold (VDFT) was performed intraoperatively and evaluation of the ADFT for induced atrial fibrillation (AF) at predischarge. After testing, each patient received a 2‐J shock and was asked to quantify discomfort on a numerical scale ranging from 0 to 10. Both groups were comparable with regard to all clinical parameters studied. The mean VDFT in patients with a Hot Can device was significantly lower than in patients with a Cold Can (7.5 ± 2.3 J vs 9.8 ± 3.8 J; P < 0.03). The mean ADFT in the Hot Can group tended to be lower than in the group with Cold Cans (3.4 ± 1.4 J vs 4.5 ± 2.4 J; P = 0.07), and the proportion of patients in whom atrial cardioversion was accomplished at low energies (≤ 3 J) was higher in patients with active compared with patients with inactive pulse generators (57% vs 26%; P < 0.04). The mean discomfort reported after delivery of a 2‐J shock was comparable in both groups (Hot Can 5.2 ± 1.9; Cold Can: 5.3 ± 2.1; P = NS). We conclude that the inclusion of an active left subpectoral can in the defibrillation vector of a ventricular ICD seems to reduce the energy requirements for atrial cardioversion without increasing the discomfort caused by low energy shocks.
Double Pulse Transthoracic Defibrillation in the Calf Using Percent Fibrillation Cycle Length as Spacing Determinate
Authors: MCDANIEL WAYNE C. , SCHUDER JOHN C. , SWEENEY ROBERT J. , STOECKLE HARRY , ZHANG QIN , SULLIVAN MARK , HOGAN MARGARET C.
Published: July 2006

Recent studies have found that when multiple pulses of energy are used for defibrillation with implantable electrodes, the spacing between these pulses is better determined as a percentage of the fibrillation cycle length (CL), rather than as a fixed function of time. Here, this concept is further tested in the transthoracic defibrillation of calves, which are approximately the size of heavy humans. Eleven 90–110 kg calves (101 ± 6 kg) were used in evaluating the effectiveness in achieving transthoracic ventricular defibrillation of ten double pulse waveforms (two 50 A 4‐ms rectangular monopulses) having leading edge‐to‐edge spacings of 4 ms (a 50 A 8‐ms rectangular monopulse) and 50, 60, 70, 80, 90, 100, 110, 120, 130 percent fibrillation CL, respectively. In each of these waveforms, the total time when 50 A current was flowing (on time) was 8 ms. Our results show an unequivocal adverse interaction between the pulses, when the spacing is around 60%–70% fibrillation CL; but that the two pulses combined to defibrillate as effectively as a single 8‐ms pulse when the spacing is around 110%–130% fibrillation CL. Electrocardiographic analysis suggests that the adverse interaction is due to a refibrillation phenomenon. This study confirms that double pulses can interact and have a negative effect on defibrillation efficacy. Our data suggests that the mechanism of this interaction involves the second pulse reinitiating fibrillation when the pulse separation is in a critical range of values. Our results are also compatible with the hypothesis that the spacing of multiple pulses is better determined as a percentage of the fibrillation CL than as absolute time, although more study is necessary to fully test this hypothesis.
Effects of Body Position and Exercise on Evoked Response Signal for Automatic Threshold Activation
Authors: SCHUCHERT ANDREAS , VENTURA RODOLFO , MEINERTZ THOMAS
Published: July 2006

The Autocapture function controls and optimizes the output of the ventricular pulse amplitude automatically. For this reason an automatic test has to be performed during follow‐up to measure the evoked response signal and lead polarization for the calculation of the appropriate evoked response sensitivity setting. The aim of the study was to assess whether body position and exercise influence the evoked response and polarization. Both parameters were determined in the supine and upright position and subsequently during supine and upright symptom‐limited ergometry. The study included 14 patients with the VVIR pacemaker Regency SR+ who bad received the ventricular pacing leads Membrane E 1450 T (n = 8), CapSure Z 5034 (n = 4), or SX 60 (n = 2). The evoked response signal was 7.4 ± 3.3 mV during supine and increased to 9.7 ± 5.6 mV (+ 35%) during upright position (P < 0.05). The exercise tests were terminated at 105 ± 36 W (supine) and 110 ± 34 W (upright). There was a gradual insignificant decrease of the evoked response during each exercise test with a mean decrease of ‐ 1.1 ± 0.9 mV(‐ 15%; supine) and ‐ 1.6 ± 2.1 mV (‐ 16%; upright). The evoked response increased within 5 minutes during recovery to the initial values. Polarization remained unchanged during both tests. The pacemaker did not recommend activating autocapture in four patients who all had received high‐ohmic pacing leads. In conclusions, the measurement of the evoked response in supine position seems to represent the worst case. Physical activities did not effect autocapture function in patients with the recommended lead, but the pacemaker did not always recommend Autocapture activation in some patients with high‐ohmic pacing leads.
AV Conduction with Atrial Rate Adaptive Pacing in the Bradycardia Tachycardia Syndrome
Authors: SCHWAAB BERNHARD , FRÖHLIG GERD , PISTORIUS CAROLINE , SCHWERDT HOLGER , SCHIEFFER HERMANN
Published: July 2006

AV conduction with atrial rate adaptive pacing (AAIR) during exercise was investigated in 43 patients (28 men, 15 female, mean age 68 ± 7 years) who were paced and medicated with antiarrhythmic drugs for the bradycardia tachycardia syndrome (BTS). Patients were included if they had no second‐ or third‐degree AV block, no complete bundle branch or bifascicular block, and a PQ interval ± 240 ms during sinus rhythm at rest. The interval between the atrial spike and the following Q wave (SQ) was measured in the supine position at rest (R) with maximum AAI pacing rate (Fmax) achieved below the Wenckebach point (SQ‐H‐Fmax). Bicycle ergometry was performed using the Chronotropic Assessment Exercise Protocol, and AAI pacing rate was increased stepwise by programming load‐adapted increments. Seven patients showed intrinsic rhythm during exercise. In those 36 patients who were atrially paced throughout ergometry (E), SQ was measured with 70 beats/min on the lowest CAEP stage (SQ‐E‐70) and with Fmax at maximum work load (SQ‐E‐Fmax). During exercise, no second‐degree AV block was observed, but 28 of 36 patients (78%) showed a nonphysiological increase of the SQ interval, and the average SQ‐E‐Fmax was significantly longer than SQ‐E‐70 (250 ± 31 versus 228 ± 32 ms, P < 0.01). There was only a weak correlation between SQ‐R‐Fmax and SQ‐E‐Fmax (r = 0.35824, P < 0.05). When Fmax obtained during exercise was kept during recovery, 14 patients (39%) developed a second‐degree AV block between 15 and 240 seconds after ergometry, 8 patients within 90 seconds. Patients who had exhibited a P on T wave in the ECG with Fmax at the end of exercise (11 of 36 patients) were reevaluated by Doppler echocardiography. Using the same exercise protocol and identical, load‐adapted rate increments, only 3 of 11 patients showed premature mitral valve closure. It is concluded that patients paced and medicated for BTS are prone to a nonphysiological prolongation of AV conduction with AAIR pacing during and after exercise. As this risk can hardly be predicted by rapid atrial pacing at rest, the pacing system should be dual chamber in this subset of patients. This especially applies to the patients in whom mechanical AV timing is affected by the conduction delay.
Optimal Cardiac Pacing After Heart Transplantation
Authors: MELTON IAIN C. , GILLIGAN DAVID M. , WOOD MARK A. , ELLENBOGEN KENNETH A.
Published: July 2006

The transplanted heart is characterized physiologically by autonomic denervation, chronotropic incompetence, intermittent episodes of allograft rejection, and frequently by diastolic dysfunction. Sinus node dysfunction resulting in bradycardia is common in the early postoperative period following standard orthotopic cardiac transplantation. Bradycardia tends to remit spontaneously but there are no factors that accurately identify patients who will need long‐term pacing. Patients in whom bradycardia persists beyond the second postoperative week despite treatment with theophylline require permanent pacemaker implantation. It has been observed that chronotropic incompetence and diastolic dysfunction are important determinants of exercise capacity following heart transplantation. Pacing that restores chronotropic competence improves exercise capacity, confirming the importance of impaired heart rate response. As in other settings, pacing that preserves atrioventricular (AV) synchrony results in increased cardiac output. For these reasons when pacing is necessary we recommend the DDDR mode (AAIR if intact AV nodal conduction is present) so that the 30%–50% of patients who remain pacemaker‐dependent long‐term obtain maximal benefit from their transplant.
Left Atrial Tachycardia After Right Atrial Separation for Chronic Atrial Fibrillation with Atrial Septal Defects
Authors: SUEDA TAIJIRO , IMAI KATSUHIKO , NAGATA HIDEYUKI , ORIHASHI KAZUMASA , MATSUURA YUICHIRO
Published: July 2006

A right atrial separation procedure was performed for the ablation of chronic atrial fibrillation in four cases, concomitant with the repair of the atrial septal defect. After the operation, chronic atrial fibrillation disappeared in three of them and left atrial tachycardia occurred in the other one. Left atrial tachycardia is an arrythmia encountered after a right atrial separation procedure.
Repetitive Monomorphic Ventricular Tachycardia of Left Coronary Cusp Origin
Authors: SADANAGA TSUNEAKI , SAEKI KIMIKO , YOSHIMOTO TATSUJI , FUNATSU YOKO , MIYAZAKI TOSHIHISA
Published: July 2006

Repetitive monomorphic ventricular tachycardia with a morphology of inferior axis and left bundle branch block pattern in patients without structural heart disease commonly originates from the right ventricular outflow tract. We report the case of a 22‐year‐old man with an incessant, monomorphic ventricular tachycardia with a similar morphology originating from the left coronary cusp, which was confirmed by perfect pace mapping, local ventricular activation preceding the onset of QRS by 25 mse, and eliminated by a single delivery of low‐energy (11 W) radiofrequency currents.
Neuromuscular Function of the Latissimus Dorsi Muscle in Goats After Dynamic Cardiomyoplasty
Authors: MONNET ERIC , ORTON E. CHRISTOPHER , CHILD GEORGINA , GETZY DAVID , JACOBS GORDON , METELMAN LISA
Published: July 2006

Skeletal muscle deterioration is emerging as a limitation to long‐term cardiac assist by dynamic cardiomyoplasty. Chronic electrical stimulation of in situ skeletal muscle showed that ischemia, decreased muscle preload, muscle overuse, and chronic electrical stimulation are factors for muscle deterioration. Transposition around the heart has been associated with signs of muscle denervation after chronic electrical stimulation. To evaluate latissimus dorsi muscle neuromuscular function after long‐term dynamic cardiomyoplasty, we performed neuromuscular functional analysis and histology on the latissimus dorsi muscle and thoracodorsal nerve of six normal goats and six goats after 6 months of dynamic cardiomyoplasty. Electromyographic analysis showed positive sharp waves and fibrillation potentials in the latissimus dorsi of three goats from the dynamic cardiomyoplasty group. Conduction velocity of the thoracodorsal nerve of goats from the dynamic cardiomyoplasty group (58.32 ± 9.80 m/s) was reduced compared to the goats from the control group (71.48 ± 5.71 m/s, P = 0.02). Histologic changes in skeletal muscle were compatible with denervation. Loss of myelin sheaths, collapse of endoneurial connective tissue, and solitary foci of axonophagia and myelinophagia further documented severe injury to the thoracodorsal nerve in goats from the dynamic cardiomyoplasty group. The latissimus dorsi muscle wrap was denervated after long‐term dynamic cardiomyoplasty. Traction on the neurovascular pedicle at each contraction of the transposed muscle may induce afferent axonal injury of the thoracodorsal nerve resulting in diminished muscular function.
Effects of Ischemia on P Wave Dispersion and Maximum P Wave Duration During Spontaneous Anginal Episodes
Authors: DILAVERIS POLYCHRONIS E. , ANDRIKOPOULOS GEORGE K. , METAXAS GERASIMOS , RICHTER DIMITRIS J. , AVGEROPOULOU CATHERINE K. , ANDROULAKIS ARISTIDES M. , GIALAFOS ELIAS J. , MICHAELIDES ANDREAS P. , TOUTOUZAS PAVLOS K. , GIALAFOS JOHN E.
Published: July 2006

P wave dispersion (P dispersion), defined as the difference between the maximum and the minimum P wave duration, and maximum P wave duration (P maximum) are electrocardiographic (ECG) markers that have been used to evaluate the discontinuous propagation of sinus impulses and the prolongation of atrial conduction time, respectively. To study the effects of myocardial ischemia on P dispersion and P maximum, 95 patients with coronary artery disease (CAD) and typical angina pectoris and 15 controls with anginalike symptoms underwent 12‐lead surface ECG during and after the relief of pain. During pain and during the asymptomatic period, P maximum and P dispersion were calculated from the averaged complexes of all 12 leads. P dispersion increased significantly during spontaneous angina (45 ± 17 ms) compared to the asymptomatic period (40 ± 15 ms), P < 0.001 only in the patient group. Both P maximum and P dispersion showed higher values during angina in those patients who developed diffuse ischemia, as estimated with ST segment changes in multiple ECG leads. P dispersion showed higher values during the anginal episode in patients with left ventricular dysfunction, independently of the presence of a previous myocardial infarction. Atrial conduction abnormalities, as estimated with P maximum and particularly P dispersion, are significantly influenced by myocardial ischemia in patients with CAD and spontaneous angina.
Recurrent Atrial Electrode Displacement Complicating a Single Lead VDD Pacing System
Authors: WALKER BRUCE D. , THORBURN CHARLES W. , KUCHAR DENNIS L.
Published: July 2006

We describe an unusual complication of single‐lead VDD pacing: recurrent advancement of the atrial bipole into the right ventricle. As a consequence, the patient experienced symptomatic pacemaker‐mediated tachycardia and underwent two revision operations to achieve adequate fixation of the lead.
Left Posteroseptal Mahaim Fiber Associated with Marked Longitudinal Dissociation
Authors: TADA HIROSHI , NOGAMI AKIHIKO , NAITO SHIGETO , OSHIMA SHIGERU , TANIGUGHI KOICHI , KUTSUMI YASUNORI
Published: July 2006

We report a patient who underwent radiofrequency catheter ablation of a left posteroseptal atrioventricular (AV) Mahaim fiber with a marked longitudinal dissociation. During atrial pacing, Wenckebach‐type atrioventricular block over the accessory pathway was observed with progressive preexcitation and no change in polarity of the delta waves. The AV conduction curve was discontinuous, with a distinct “jump‐up” in local AV conduction time of 84 ms. The earliest ventricular activation was recorded from the posteroseptal portion of the mitral annulus, and the unipolar electrogram from a distal electrode had a high, steep deflection with uniphasic QS‐like activity with 62 ms of local AV conduction time.
Influence of the Pacing Rate on the Atrioventricular Conduction Time During Aerobic and Anaerobic Exercise: Basic Concepts for a Dromotropically Controlled Rate Responsive Pacemaker
Authors: MEINE MATHIAS , HEXAMER MARTIN , WERNER JÜRGEN , ISRAEL CARSTEN W. , MÜGGE ANDREAS , LEMKE BERND , BARMEYER JÜRGEN
Published: July 2006

The dromotropic pacemaker concept needs a rate responsive algorithm in which the pacing rate is controlled by the atrioventricular conduction time (AVCT). To develop basic concepts for such a rate responsive algorithm, the influence of the pacing rate on the AVCT was investigated. Seven patients (62 ± 7.8 years) with sick sinus syndrome and intact atrioventricular conduction underwent two cardiopulmonary exercise tests (CPX) on a treadmill. According to the determination of the anaerobic threshold (AT) and the patients maximum capacity in the first incremental CPX the work rate for two exercise levels below and above the AT were chosen for the second constant workload CPX. The calculation of the optimal pacing rate (HRopt) was based on the oxygen uptake (VO2) during exercise after reaching steady‐state conditions. According to the increase of the V2 from 14.8 ± 2.3 mL/min per kilogram during aerobic work (38.3 ± 16.0 W) to 19.4 ± 4.7 mL/min per kilogram during anaerobic work (80.6 ± 32.3 W), the HRopt was calculated to be 98.6 ± 6.9 beats/min and 116.4 ± 4.7 beats/min. Starting from HRopt, the pacing rate was increased (overpacing) and decreased (underpacing) by about 5 beats/min every minute. At optimal pacing rate the AVCT decreased significantly from 233.0 ± 30.5 ms during aerobic work and to 226.4 ± 27.3 ms during anaerobic work (P < 0.05). Whereas overpacing induced a significant prolongation of the AVCT during aerobic work (4.17 ± 1.78 ms per 10 beats/min) and anaerobic work (3.84 ± 1.60 ms per 10 beats/min), underpacing yielded a significant shortening of the AVCT by about 4.49 ± 2.64 ms per 10 beats/min during aerobic work and 4.75 ± 1.87 ms per 10 beats/min during anaerobic work (P < 0.01). The slopes of the regression lines of the relationship between AVCT and pacing rate were not significantly different. Based on the reciprocal relationship of heart rate (HR) and AVCT, basic concepts may be established for a dromotropic rate responsive algorithm.
Impact of Chronic DDD Pacing on Time‐Domain Indexes of Heart Rate Variability in Patients with Hypertrophic Obstructive Cardiomyopathy
Authors: SIMANTIRAKIS E.N. , KOCHIADAKIS G.E. , KANAKARAKI M.K. , MARKETOU M.E. , PARTHENAKIS F.I. , KANOUPAKIS E.M. , VARDAS P.E.
Published: July 2006

The aim of this study was to examine whether DDD pacing affects time‐domain indexes of heart rate variability (HRV) in patients with hypertrophic obstructive cardiomyopathy (HOCM). We studied 11 patients (7 men, age 52 ± 8 years) with HOCM refractory to drugs. In all patients a DDD pacemaker was implanted and the atrioventricular delay was programmed to ensure a full ventricular activation sequence. Time‐domain indexes of HRV (mean NN, SDANN, SDNN, SD, rMSSD, pNN50) were determined from 24‐hour Holter recordings 3 days before and 1 year after pacemaker implantation. The pacemaker was turned off during the second recordings. The same indexes were determined in ten healthy controls at the same time points. The controls showed no significant differences in any of the measured parameters between the two time points. The HOCM patients showed an increase in SD (from 27 ± 13 to 41 ± 13 ms, P < 0.001), rMSSD (from 18 ± 5 to 32 ± 8 ms, P < 0.001), and pNN50 (from 1.03 ± 1.06 to 8.52 ± 4.84%, P < 0.0001). As a result, the values of these three parameters, which were lower in the HOCM patients than in the controls before pacing, were restored to normal levels by the end of the study. In conclusion, our findings indicate that long‐term pacing in HOCM patients restores the sympathovagal balance in the heart by increasing vagal activity.
Atrioventricular Dissociation as a Cause of Syncope Determined by Head‐Up Tilt Test
Authors: KATAOKA HAJIME
Published: July 2006

This report describes a patient with syncopal attacks in a sitting position on a reclining seat, in whom atrioventricular dissociation due to accelerated ventricular rhythm was determined to be the cause by recording of the electrocardiogram, blood pressure, and mitral and aortic Doppler flow during a 60± head‐up tilt test.
Variability of Atrial Sensing During Exercise in a Patient with a Dual Chamber ICD Caused Inappropriate ICD Discharges
Authors: GLOTZER TAYA V. , RADOSLOVICH GLAUCO A. , NEGLIA JOHN , ZIMMERMAN JOHN M.
Published: July 2006

We present the case of a patient with a dual chamber implantable cardioverter defibrillator (ICD) who experienced inappropriate ICD discharges during exercise. Interrogation of the ICD revealed intermittent atrial undersensing during exercise that was responsible for the erroneous classification by the ICD of sinus tachycardia as ventricular tachycardia. Monitoring of the intracardiac electrograms and Marker Channels during an exercise test confirmed a marked decrease in P wave amplitude during exercise. By increasing the atrial sensitivity setting the problem was resolved.
Pacing Lead Adhesions After Long‐term Ventricular Pacing Via the Coronary Sinus
Authors: ROSENTHAL ERIC , COOK ANDREW
Published: July 2006

Left ventricular pacing via the coronary sinus is being increasingly used. There is little data to guide possible lead extractions that might be required in the future. Significant adhesions to the coronary veins were found 12 years after placing a pacing lead in the posterolateral coronary vein in a man with double inlet left ventricle and severe subpulmonary stenosis who had undergone a Fontan operation. The appearances suggest that percutaneous extraction from the proximal coronary sinus may be feasible but that difficulty may be encountered if the lead tip is placed into the distal coronary veins.
Is Ventricular Fibrillation Interval an Indicator of Electrical Defibrillation Threshold?
Authors: MURAKAWA YUJI , YAMASHITA TAKESHI , KANESE YUKIHIRO , SEZAKI KAZUNORI , OMATA MASAO
Published: July 2006

To clarify whether peak‐to‐peak interval of the fibrillation wave (VF interval) during VF is an independent indicator of defibrillation efficacy, we measured the transcardiac DFT, VF intervals of the surface and local ECGs (lead II and the right ventricle), and the ERP in 82 open‐chest dogs. Both VF intervals showed a negative correlation with heart weight (surface: r =−0.358 [P < 0.005];local: r = ‐0.349 [P < 0.005]). DFT was 2.0 ± 0.7 A and positively correlated with heart weight (r = 0.453 [P < 0.0001]). ERP did not show a significant correlation with heart weight. DFT was negatively correlated with VF interval (vs surface VF interval: r= ‐0.568 [P < 0.0001]; vs local VF interval: r = ‐0.504 [P < 0.0001]), but showed only a weak negative correlation with ERP (r = ‐0.314 [P < 0.005]). Even after allowing for the dependency of DFT and VF intervals on heart weight (normalized to a 100‐g heart), the correlation between VF interval and DFT was still significant (vs surface VF interval: r =−0.487 [P < 0.0001]; vs local VF interval: r = ‐0.414 [P < 0.0002]). These results suggest that VF interval is an indicator of DFT in intact hearts that have not received pharmacological intervention.
Hemodynamic Effect of Rapid Atrial Pacing in Fetal Lambs
Authors: SHIRAISHI HIROHIKO , KIKUCHI YUTAKA , MOMOI MARIKO Y. , YANAGISAWA MASAYOSHI
Published: July 2006

To determine the threshold at which rapid atrial pacing brings on fetal circulatory failure, we made a fetal supraventricular tachyarrhythmia model and measured the central venous pressure, aortic pressure, and right and left ventricular outputs in five fetal lambs. Under maternal anesthesia, the uterus was opened, and under local anesthesia, polyvinyl catheters were inserted into the fetal superior vena cava and ascending aorta through a neck incision. Pacing leads (Medtronic model 6492) were then sutured onto the fetal right atrial appendage via right thoracotomy. Ventricular output was estimated using a Toshiba SSH‐65A echocardiography by a transuterine approach. Fetal hemodynamics were observed without pacing (control), and at the atrial pacing rates of 200, 300, 350. and 400/min. Central venous pressure (CVP) increased and the aortic pressure decreased when the right atrium was paced at 350/min or more. Right ventricular output decreased when the right atrium was paced at 300/min or more. The left ventricular output, however, remained constant. The right ventricular output was 382 ± 106 mL/kg/min at control, and 391 ± 117 mL/kg/min when paced at 200/min, but decreased to 210 ± 138 mL/kg/min when paced at 300/min, to 223 ± 102 mL/kg/min when paced at 350/min. and to 186 ± 86 mL/kg/min when paced at 400/min. Fetal circulatory failure occurred when the right atrium was paced at 300/min or more.
Successful Radiofrequency Ablation of a Slow Atrioventricular Nodal Pathway on the Left Posterior Atrial Septum
Authors: JAÏS PIERRE , HAÏSSAGUERRE MICHEL , SHAH DIPEN C. , COSTE PIERRE , TAKAHASHI ATSUSHI , BAROLD S. SERGE , CLÉMENTY JACQUES
Published: July 2006

RF catheter ablation is highly effective in eliminating atrioventricular nodal reentrant tachycardia by targeting the slow pathway in the posteroinferior part of Koch's triangle in the right atrium. We report here a patient in whom “slow‐fast” atrioventricular nodal reentrant tachycardia was eliminated only by ablation of the slow pathway in the left atrial posteroseptal region at the level of the mitral annulus after unsuccessful attempts at the traditional site on the right side.
Implantation of Permanent Dual Chamber Pacemaker in a Pregnant Woman by Transesophageal Echocardiographic Guidance
Authors: ANTONELLI DANTE , BLOCH LEV , ROSENFELD TIBERIO
Published: July 2006

A 37‐year‐old woman complained of fatigue and dizziness because of intermittent sinus arrest and asystole up to 5.2 seconds. She was 3 months into her pregnancy and a dual chamber permanent pacemaker was implanted by transesophageal echocardiographic guidance.
Preliminary Clinical Results of a Biphasic Waveform and an RV Lead System
Authors: MEHDIRAD ALI A. , LOVE CHARLES J. , STANTON MARSHALL S. , STRICKBERGER S. ADAM , DUNCAN JAMES L. , KROLL MARK W.
Published: July 2006

Biphasic defibrillation waveforms have provided a reduction in defibrillation thresholds in transvenous ICD systems. Although a variety of biphasic waveforms have been tested, the optimal pulse durations and tilts have yet to be identified. A multicenter clinical study was conducted to evaluate the performance of a new ICD biphasic waveform and new RV active fixation steroid eluting lead system. Fifty‐three patients were entered into the study. Mean age was 63 years with a mean ejection fraction of 36.8%. Primary indication for implantation was monomorphic ventricular tachycardia alone (54.7%). Forty‐eight patients (90.6%) were implanted with an RV shocking lead and active can alone as the anodal contact. The ICD can was the cathode. In four cases (7.5%), an additional SVC or CS had was used due to a high DFT with the RV lead alone. In an additional case, a chronic SVC lead was used although the RV‐Can DFT was acceptable. DFT for all cases at implant was 9.8 ± 3.7 J. Repeat testing at 3 months for a subset of patients showed a reduction in DFT (7.4 ± 3.0 J), P value = 0.03. Sensing and pacing characteristics of the RV lead system remained excellent during the study period (acute 0.047 ± 0.005 ms at 5.4 V and 9.9 ± 6.2 mV R wave; chronic 0.067 ± 0.11 ms at 5.4 V and 9.3 ± 5.4 mV R wave). It is concluded that this lead system provides good acute and chronic sensing and pacing characteristics with good DFT values in combination with this waveform.
Electromagnetic Interference of Digital and Analog Cellular Telephones with Implantable Cardioverter Defibrillators: In Vitro and In Vivo Studies
Authors: BARBARO V. , BARTOLINI P. , BELLOCCI F. , CARUSO F. , DONATO A. , GABRIELLI D. , MILITELLO C. , MONTENERO A.S. , ZECCHI P.
Published: July 2006

The present study examines the potential electromagnetic interference effects induced by cellular telephones on ICDs. We developed ad hoc protocols to conduct both in vitro and in vivo trials on most of the implantable cardioverter defibrillators available on the international market. Trials were conducted with three cellular telephones: two GSM (Global System for Mobile Communication) and one TACS (Total Access Communication System). A human trunk simulator was used to carry out in vitro observations on six ICDs from five manufacturers. In vivo tests were conducted on 13 informed patients with eight different ICD models. During the trials in air, GSM telephones induced interference effects on 4 out of the 6 cardioverter defibrillators tested. Specifically, pulse inhibition, reprogramming, false ventricular fibrillation, and ventricular tachycardia detections occurred, which would have entailed inappropriate therapy delivery had this been activated. Effects were circumscribed to the area closely surrounding the connectors. When the ICD was immersed in saline solution, no effects were observed. Three cases of just ventricular triggering with the interfering signal were observed in vivo.
Effect of Different AV Delays on Left Ventricular Diastolic Function and ANF Levels in DDD Paced Hypertensive Patients During Daily Activity and Exercise
Authors: PANOU FOTIS K. , KAFKAS NICKOLAS V. , MICHELAKAKIS NICKOLAS A. , MATSAKAS EVAGELOS P. , DOUNIS GEORGE B. , KOUVOUSIS NICKOLAS M. , PERPINIA ANASTASIA S. , ZACHAROULIS APOSTOLOS A.
Published: July 2006

Fifteen hypertensive patients (13 men) with left ventricular hypertrophy, mean age 69 6 5 years, having complete heart block and paced in the DDD mode, were studied by two‐dimensional and Doppler echo in 100 and 200 ms atrioventricular delays. ANF plasma levels were measured at rest and at peak exercise, during pacing with the two different atrioventricular delays. ANF plasma levels were significantly higher at pacing with long atrioventricular delays (200 ms), at rest (152.47 6 12.38 pg/mL vs 119 6 12.38 pg/mL, P, 0.001) and at exercise (180.93 6 11.51 vs 123.67 6 16.24 pg/mL, P, 0.0001). ANF plasma levels were significantly increased at exercise, compared to those at rest during pacing with the two different atrioventricular delays, but we found a more pronounced increase of ANF levels (from 152.47 6 10.49 pg/mL to 180.93 6 11.51 pg/mL), when the atrioventricular delays was set to 200 ms (P, 0.0001). A significant decrease of isovolumic relaxation time (from 123.33 6 20.5 to 105.33 6 11.06 ms, P, 0.001) was observed, during pacing with the short atrioventricular delays. Moreover, the peak early (E) to peak atrial (A) velocity ratio (E/A) was declined (from 0.89 6 0.7 to 0.57 6 0.18, P, 0.05). We also noticed that patients with small left ventricles exhibit greater increase in ANF plasma levels during DDD pacing with long atrioventricular delays (r 5 20.792, P 5 0.000). In conclusion, left ventricular diastolic function of our patients seems to be improved during DDD pacing with short (100 ms) atrioventricular delays, as it was expressed by echocardiographic and hormonal measurements.
What is the Relationship of Atrial Flutter and Fibrillation?
Authors: ROITHINGER FRANZ X. , LESH MICHAEL D.
Published: July 2006

Animal models and human studies of atrial activation mapping and entrainment have considerably enhanced our understanding of the anatomical substrate for atrial flutter and created the basis for a definite cure with radiofrequency catheter ablation. As atrial flutter has now become a curable arrhythmia, emphasis is shifting to understand the most common arrhythmia: atrial fibrillation. Furthermore, from clinical observation, it is apparent that there is a relationship between atrial fibrillation and atrial flutter in patients with atrial arrhythmias. Techniques that have informed our understanding of the anatomical basis of atrial flutter may also be useful in understanding the relationship between atrial fibrillation and flutter, including animal models, clinical endocardial mapping, and intracardiac anatomical imaging. Thus, atrial anatomy and its relationship to electrophysiological findings, and the role of partial or complete conduction barriers around which reentry can and cannot occur, may be of importance for atrial fibrillation as well. Ultimately, the relationship between atrial fibrillation and atrial flutter may inform our understanding of the mechanisms of atrial fibrillation itself, and help to develop new approaches to device, catheter‐based, and pharmacological therapy for atrial fibrillation.
Nicorandil, a Potassium Channel Opener, Abolished Torsades de Pointes in a Patient with Complete Atrioventricular Block
Authors: WATANABE OTSU , OKUMURA TARO , TAKEDA HIROSHI , NAKAMURA WAKO , SEGAWA KAZUHIKO , ITO HIROYUKI , YOSHIMOTO NOBUO
Published: July 2006

TdP is a serious complication of AV block. We report a case of complete AV block with QT prolongation who had bouts of TdP resistant to lidocaine and isoproterenol. Temporary pacing could not be performed, because insertion of a pacing lead triggered TdP that deteriorated into ventricular fibrillation. Nicorandil, a potassium channel opener, shortened the QT interval and abolished TdP. This may suggest that potassium channel opening drugs are clinically effective against TdP associated with bradycardia‐dependent QT prolongation.
Intermittent P Wave Sensing in a Patient with DDD Pacemaker
Authors: PARASKEVAIDIS STELIOS , MOCHLAS SOTIRIOS , HADJIMILTIADIS STAVROS , LOURIDAS GEORGIOS
Published: July 2006

We present the case of a patient with a DDD pacemaker and intermittent P wave sensing due to T wave oversensing by the ventricular lead. The T wave sensing caused initiation of an extended atrial refractory period and the P waves, falling within this period, were not sensed. The problem was solved by decreasing the ventricular sensitivity.
Epicardial, Biatrial Synchronous Pacing for Prevention of Atrial Fibrillation after Cardiac Surgery
Authors: KURZ DAVID J. , NAEGELI BARBARA , KUNZ MARTIN , GENONI MICHELE , NIEDERHÄUSER URS , BERTEL OSMUND
Published: July 2006

About 30% of patients develop AF after open heart surgery. Biatrial synchronous pacing (BSP) has been shown to promote sinus rhythm in patients with paroxysmal AF refractory to drug therapy. We conducted a prospective, randomized study to test the effect of BSP via epicardial electrodes on the incidence of AF after heart surgery, as compared to conventional therapy. To apply BSP, we attached two epicardial electrodes to the right and one to the left atrium. Immediately following surgery, BSP was initiated in the AAI‐Mode at a rate of 10 beats/min above the underlying rhythm (maximum 110 beats/min) and continued for 3 days, during which the rhythm was continually monitored. After 21 (age 63 ± 9 years) of the planned 200 patients, the study was prematurely aborted because of the proarrhythmic effect of BSP; 6 of the 12 patients treated with BSP developed sensing failure (P amplitude < 1 mV), which provoked AF in 5 of these 6 patients. BSP was discontinued due to diaphragmal stimulation in two patients and due to ventricular stimulation by a dislocated left atrial electrode in one patient. Two patients in the control group (n = 9) developed AF. Using the available standard technology, BSP via epicardial electrodes is not suitable to suppress AF after heart surgery, primarily due to postoperative deterioration of atrial sensing and its profibrillatory effect. In patients requiring atrial pacing after heart surgery, sensing thresholds must be closely monitored to prevent induction of AF.
Effects of Extracorporeal Shock Wave Lithotripsy on Tiered Therapy Implantable Cardioverter Defibrillators
Authors: CHUNG MINA K. , STREEM STEVAN B. , CHING ELIZABETH , GROOMS MIRIAM , MOWREY KENT A. , WILKOFF BRUCE L.
Published: July 2006

The effects of extracorporeal shock wave lithotripsy (ESWL) were tested on four advanced generation implantable cardioverter‐defibrillators (ICDs) in vitro and in vivo in two patients. During in vitro testing, advancement of nonsustained episode counters occurred in one device, and a set screw and power source cell loosened in another, which was connected to an external power source. No arrhythmias occurred during in vivo procedures, but programmed parameters were reset and elective replacement indicated after one procedure. ESWL can be performed safely in selected patients with ICDs, but testing should be performed afterwards to confirm satisfactory function and component continuity.
Atrial Flutter Ablation using a Technique for Detection of Conduction Block within the Posterior Isthmus
Authors: WILLEMS STEPHAN , WEISS CHRISTIAN , HOFFMANN MATTHIAS , MEINERTZ THOMAS
Published: July 2006

Catheter ablation orientated on the induction of a functional intraatrial block within the posterior isthmus of the tricuspid annulus has been shown to effectively abolish atrial flutter. In order to improve and simplify the current technique, a strategy based on an electrode catheter for combined right atrial and coronary sinus mapping and stimulation was explored prospectively. Twenty‐four consecutive patients referred for catheter ablation of recurrent type I atrial flutter were included. A steerable 7 Fr catheter (Medtronic/Cardiorhythm) composed of two segments with 20 electrodes was used for right atrial and coronary sinus activation mapping and stimulation. Multiple steering mechanisms allowing intubation and positioning of the distal part within the coronary sinus were incorporated into the device. Adequate positioning of the mapping catheter was achieved solely via a transfemoral approach in all patients after 7.7 ± 4.6 minutes, providing stable electrogram recordings during the entire ablation procedure. Radiofrequency current ablation (16.3 ± 9.6 pulses) caused a significant bidirectional increase of the mean intraatrial conduction times via the posterior isthmus irrespective to the stimulation interval. Significant changes of intraatrial conduction properties were induced during ablation in 22 of 24 patients (bidirectional block: n = 18, unidirectional block: n = 3, conduction delay: n = 1, unchanged conduction: n = 2). Following ablation atrial flutter was noninducible in all patients. Twenty‐two of 24 patients (92%) remained free of atrial flutter episodes during a follow‐up of 12.5 ± 5.7 months. Two of six patients without a bidirectional conduction block had a recurrence of atrial flutter. Atrial flutter ablation guided by the induction of an intraatrial conduction block can be effectively performed with this novel strategy for combined mapping of the posterior tricuspid isthmus, including coronary sinus and right atrial free wall. This transfemoral approach has a high accuracy with respect to the detection of radiofrequency current‐induced changes of intraatrial conduction patterns.
Optimized Pulse Durations Minimize the Effect of Polarity Reversal on Defibrillation Efficacy with Biphasic Shocks
Authors: SCHAUERTE PATRICK , SCHÖNDUBE FRIEDRICH A. , GROSSMANN MARIUS , MESSMER BRUNO J. , HANRATH PETER , STELLBRINK CHRISTOPH
Published: July 2006

There are conflicting results on the effect of polarity change on the defibrillation efficacy of biphasic shocks possibly caused by different shock durations. The goal of the present study was to investigate the influence of polarity reversal on defibrillation efficacy for different biphasic shock durations in a porcine animal model. In eight anesthesized pigs using a transvenous/submuscular lead system DFTs for 4 phase 1 durations were determined: 8.1 ms, 6 ms, 3.8 ms and 1.7 ms. The phase 1/phase 2 ratio was constant at 60%/40%. For cathodal shocks, the defibrillation coil in the right ventricular apex was the cathode during phase 1 and for anodal shocks it was the anode. For both polarities, the strength‐duration curve revealed a DFT minimum at 3.8 ms (cathodal shocks: 21.3 ± 6.4 J, P < 0.001; anodal shocks: 21.9 ± 8 J, P = 0.05). For anodal shocks and phase 1 durations of 1.7, 3.8, and 6 ms there was no significant difference of the stored energy at the DFT compared to cathodal shocks. In contrast, significantly lower DFTs were observed for anodal shocks with a phase 1 duration of 8.1 ms (28.8 ± 6.4 J compared to 33.1 ± 5.9 J for cathodal shocks, P = 0.006). The effect of lower defibrillation energy requirements with polarity reversal depends on the total biphasic shock duration; for the pulse duration with the lowest DFT, polarity reversal does not increase defibrillation efficacy of biphasic shocks.
Inappropriate Implantable Cardioverter‐Defibrillator Therapy Due to the Detection of Premature Ventricular Complexes
Authors: GOLDBERGER JEFFREY J. , HORVATH GEORGE , CHALLAPALLI RAM , KADISH ALAN H.
Published: July 2006

Inappropriate shocks delivered by implantable cardioverter‐defibrillators may occur in 15%–40% of patients treated with these devices. This article describes a rare cause for inappropriate shocks. Two patients received inappropriate shocks due to the presence of premature ventricular complexes during attempted reconfirmation of ventricular fibrillation. Knowledge of device algorithms for detection and reconfirmation of ventricular fibrillation, designed to have a high degree of sensitivity and therefore lower specificity, allows for reprogramming to avoid further inappropriate shocks.
The Potential for Inappropriate Ventricular Tachycardia Confirmation Using the Intracardiac Electrogram (EGM) Width Criterion
Authors: DURU FIRAT , SCHÖNBECK MARIETTE , LÜSCHER THOMAS F. , CANDINAS RETO
Published: July 2006

The “Intracardiac Electrogram (EGM) Width Criterion,” the first digital signal processing feature used in an implantable cardioverter defibrillator (ICD), is a detection enhancement algorithm that intends to improve ventricular tachycardia (VT) detection specificity by rejecting inappropriately detected supraventricular tachyarrhythmias. The algorithm may be activated after setting the optimal EGM source, slew, and width thresholds based on EGM width testing during sinus rhythm. This study evaluates the accuracy of the ECM width measurements during exercise testing. Twenty‐one patients with Medtronic Micro Jewel II Model 7223 ICDs underwent treadmill exercise testing. EGM width testing was repeatedly performed during exercise and recovery to detect potential inappropriate measurements. In seven (33%) patients the EGM Width Criterion inappropriately confirmed VT detection. Eleven patients had inappropriately wide EGM width measurements, but did not satisfy the EGM Width Criterion. The causes of wide EGM width measurements were an actual increase in EGM width and/or inappropriate detection of the baseline irregularities as EGM onset or offset points. Based on our observations, we recommend to test the EGM Width Criterion during exercise testing for optimal ICD programming.
Relationship Between Atrioventricular Delay and Oxygen Consumption in Patients with Sick Sinus Syndrome: Relevance to Rate Responsive Pacing
Authors: MEINE MATHIAS , HEXAMER MARTIN , WERNER JÜRGEN , ISRAEL CARSTEN W. , LEMKE BERND , BARMEYER JÜRGEN
Published: July 2006

To develop a dromotropic‐controlled rate adaptive algorithm for patients with sick sinus syndrome (SSS) and intact AV conduction, 14 pacemaker patients with SSS underwent cardiopulmonary exercise testing (CPX). During exercise, the pacemaker was programmed in an AAT mode without rate adaptation, whereby 3 patients developed supraventricular arrhythmia and 11 patients kept sinus rhythm. Chronotropic incompetence (CI) at heart rate (HR) < 95 beats/min at the anaerobic threshold (AT) was found in five patients. In patients with chronotropic competence (CC), the HR increase was significantly greater than in CI patients (rest: 73.2 ± 12.6 vs. 64.2 ± 4.0 beats/min; AT:101.2 ± 6.2 vs. 82.0 ± 5.1 beats/min; peak: 135.2 ± 10.7 vs. 103.2 ± 10.9 beats/min). There was no significant difference in the AVD between CC and CI patients (rest: 167.7 ± 38.6 vs. 170.8 ± 22.5 ms, AT: 156.2 ± 30.7 vs. 163.6 ± 21.6 ms, peak: 144.7 ± 29.0 vs. 152.4 ± 15.0 ms). The correlation coefficient between HR increase and VO2 was +1.0 and between AVD decrease and VO2– 1.0 in both groups. An increase in pacing rate from 75 beats/min to 120 beats/min without exercise (overpacing) led to a prolongation of the AV interval of about 30.6 ± 14.2 ms. Based on this closed loop control with negative feedback, a dromotropic rate adaptive algorithm for patients with SSS and intact AV conduction could be developed.