bluuebunny/crossref_metadata_2025 huggingface dataset:
Time to First Shock in Implantable Cardioverter Defibrillator (ICD) Patients with Chagas Cardiomyopathy
Authors: RABINOVICH RAFAEL , MURATORE CLAUDIO , IGLESIAS RICARDO , GONZALEZ MIGUEL , DARÚ VÍCTOR , VALENTINO MARIANA , LIPRANDI ALVARO SOSA , LUCERI RICHARD
Published: July 2006

The time to first ICD shock has been extensively studied in patients with coronary artery disease (CAD). However, there are no published data on ICD shocks in patients with Chagas cardiomyopathy (ChC). The occurrence of the first appropriate ICD shock during the first 6 months of follow‐up in 20 patients with ChC (group 1) and 35 CAD patients (group 2) was analyzed retrospectively. All patients had received a third‐generation pectoral ICD for ventricular tachycardia or fibrillation (VT/VF). Indications for ICD implantation were refractoriness to drug therapy or noninducibility of VT/VF at EPS in cardiac arrest survivors. Results: The mean age, left ventricular ejection fraction (LVEF), and sex in groups I and II were 57.4 ± 7 years versus 64 ± 9 (P < 0.01), 30.9%± 10% versus 32.9%± 10% (P = NS), and 10 men versus 31 women (P < 0.005), respectively. Six months after ICD implantation, 85% (17/20) group I patients received appropriate ICD shocks versus 51 % (18/35) in group 2, a statistically significant difference (P < 0.02, RR: 1.65, OR: 5.35). Conclusions: The incidence of appropriate ICD shocks within the first 6 months postimplantation was significantly higher in ChC patients than in CAD patients. ChC patients were younger and more often women than CAD patients.
Improved Clinical Efficacy of External Cardioversion by Fluoroscopic Electrode Positioning and Comparison to Internal Cardioversion in Patients with Atrial Fibrillation
Authors: MEHDIRAD ALI A. , CLEM KELLEY L. , LOVE CHARLES J. , NELSON STEVEN D. , SCHAAL STEPHEN F.
Published: July 2006

Background: Despite using different electrode positions, “conventional” external DC cardioversion in patients with atrial fibrillation is ineffective in 6%–50% of cases. An alternative when DC cardioversion is not successful is low energy internal cardioversion, which is performed at increased risk. We tested the hypothesis that optimization of electrode pad position under fluoroscopy to encompass as much atrial muscle as possible might improve the success rate of external cardioversion and thus minimize the need for internal cardioversion. Methods: Fifteen (9 males, 6 females) patients (age: 54 ± 15 years, weight: 124 ± 35 kg) with chronic atrial fibrillation (> 8 weeks) who had undergone unsuccessful conventional external cardioversion entered the study. Repeat conventional external cardioversion with electrodes in standard (right anterior and left posterior) positions was followed by “optimized” external cardioversion by positioning electrodes under fluoroscopy (using metallic markers). In case of failure, internal cardioversion was performed. Results: All 15 patients had undergone unsuccessful conventional external cardioversion with 360‐J shocks. Eight patients (group A) reverted to sinus rhythm with one or two 360‐J shocks using fluoroscopy‐guided pad placement (53%). Six of the remaining 7 (86%) patients (group B) had successful internal cardioversion with biphasic shocks (12 ± 3 J). The body weight and body mass index were statistically lower in group A vs group B (106 ± 27 vs 145 ± 33 kg, p = 0.03 and 35 ± 8 vs 45 ± 8 kg/m2, P = 0.48, respectively). There was no statistically significant in age, height, body surface area, duration of atrial fibrillation, amiodarone therapy, ejection fraction, or underlying heart disease. Conclusion: Unsuccessful external DC cardioversion, in some patients, is in part due to suboptimal conventional positioning of electrode pads that can be improved under fluoroscopic guidance by achieving the best possible vector encompassing the right and left atria. The optimized external cardioversion technique may minimize the need for internal cardioversion, which remains an effective approach when external cardioversion fails.
Low Energy Internal Atrial Cardioversion in Atrial Fibrillation Lasting More Than a Year
Authors: BORIANI GIUSEPPE , BIFFI MAURO , PERGOLINI FRANCESCO , ZANNOLI ROMANO , BRANZI ANGELO , MAGNANI BRUNO
Published: July 2006

The aim of this study was to evaluate the efficacy of low energy internal atrial cardioversion in restoring sinus rhythm (SR) in patients with chronic atrial fibrillation (AF) persisting > 1 year. Fifteen patients with chronic AF lasting > 1 year (from 13–48 months, mean 24 ± 13 months) were studied. R wave synchronized 3/3 ms biphasic shocks were delivered between right atrial and coronary sinus (left pulmonary artery in five patients) electrodes. Sedatives or anesthetics were administered only at the patient's request. Results: Stable SR was restored in 14 (93%)of 15 patients after shocks with a mean leading edge voltage of 377 ± 77 V (range 260–500) and a mean delivered energy of 7.3 ± 3.4 J (range 2.6–12.9). The procedure was performed without anesthesia in 6 (40%) patients. All successfully cardioverted patients were treated with flecainide, sotalol, or amiodarone. During a follow up of 7.7 ± 7.9 months (range 1–24) AF recurred in five (36%) patients. Three of five AF recurrences occurred within 3 days after conversion to SR. Conclusion: Internal low energy atrial cardioversion is highly effective in restoring SR even in patients with AF lasting > 1 year. The long‐term results from the standpoint of freedom from AF recurrences, are satisfactory, although additional antiarrhythmic treatment is required, particularly in the first days after conversion.
Clinical Follow‐up After Cessation of Chronic Electrical Neuromodulation in Patients with Severe Coronary Artery Disease: A Prospective Randomized Controlled Study on Putative Involvement of Sympathetic Activity
Authors: JESSURUN GILLIAN A.J. , DEJONGSTE MIKE J.L. , HAUTVAST RAYMOND W.M. , TIO RENÉ A. , BROUWER JAN , VAN LELIEVELD STEVEN , CRIJNS HARRY J.G.M.
Published: July 2006

The present study assessed the reoccurrence of myocardial ischemia after withholding electrical neurostimulation. After randomization, in the study or withdrawal group, spinal cord stimulation (SCS) was set active during the first 4 weeks, followed by 4 weeks of withholding stimulation. In the control group, SCS was switched off during 4 weeks before the end of the study. The control group had no crossover period. Measurements were done at baseline, then after 4 and 8 weeks. The first periods at 4 weeks of each sequence of both groups were compared. In addition, a comparison of clinical variables was performed between the study group 4 weeks after withholding stimulation and the control group 4 weeks following randomization. A total number of 24 patients with refractory angina and an implanted spinal cord stimulator were included in the study (n = 12) and control group. Angina pectoris complaints, nitroglycerin intake, ischemia, and heart rate variability using 48‐hour ambulatory electrocardiographic monitoring were assessed. In addition, neurohormonal status and symptom‐limited aerobic capacity were evaluated. There was no increase of anginal complaints or ischemia after withholding stimulation. Neurohormonal levels and aerobic capacity were not altered. We conclude that there is no adverse clinical rebound phenomenon after withholding neurostimulation in patients with refractory angina pectoris.
Circadian Variability of Late Potential Analysis in Holter Electrocardiograms
Authors: STEINBIGLER PETER , HABERL RALPH , JILGE GERHARD , STEINBECK GERHARD
Published: July 2006

Appearance of ventricular tachycardia, ventricular fibrillation, and sudden cardiac death has diurnal variations. We retrospectively studied, using digital Holter electrocardiogram, whether a time course in the appearance of late potentials may be associated with malignant ventricular arrhythmias. The 24‐hour recordings in 200 patients after myocardial infarction (50 patients with documented, sustained, monomorphic and reproducibly inducible ventricular tachycardia (< 270/min) (group I), 50 patients resuscitated from ventricular fibrillation (group II), and 100 patients without ventricular arrhythmias (group III) were divided into 24 segments, 60 minutes each. Late potential analysis was performed using the Simson method in the time domain in each segment and compared to a conventional short‐term registration. Late potential analysis in conventional short‐term recordings during arbitrarily chosen daytimes revealed late potentials in 80% of patients in group I, 38% of patients in group II, and in 16% of patients without ventricular arrhythmias. In at least one 60‐minute segment late potentials were found in group I in 92%, in group II in 88% (P < 0.05 vs conventional analysis), and in group III in 19%. Interestingly, in patients with a history of ventricular fibrillation late potentials appeared significantly more often during morning hours (6–12 am: 82% vs 26% at 12 am–6 pm, 30% at 6 pm–12 pm, and 42% at 12 pm–6 am, P < 0.05), especially during phases with heart rate accelerations. Late potential analysis for risk stratification in conventional short‐term recordings is feasible for patients prone to ventricular tachycardia, but patients prone to ventricular fibrillation would be more effectively stratified using 24‐hour registrations with detection of circadian variations of late potential appearance.
External Exponential Biphasic Versus Monophasic Shock Waveform: Efficacy in Ventricular Fibrillation of Longer Duration
Authors: YAMANOUCHI YOSHIO , BREWER JAMES E. , DONOHOO ANN M. , MOWREY KENT A. , WILKOFE BRUCE L. , TCHOU PATRICK J.
Published: July 2006

Ventricular fibrillation (VF) duration may be a factor in determining the defibrillation energy for successful defibrillation. Exponential biphasic waveforms have been shown to defibrillate with less energy than do monophasic waveforms when used for external defibrillation. However, it is unknown whether this advantage persists with longer VF duration. We tested the hypothesis that exponential biphasic waveforms have lower defibrillation energy as compared to exponential monophasic waveforms even with longer VF duration up to 1 minute. In a swine model of external defibrillation (n = 12, 35 ± 6 kg), we determined the stored energy at 50% defibrillation success (E50) after both 10 seconds and 1 minute of VF duration. A single exponential monophasic (M) and two exponential biphasic (B1 and B2) waveforms were tested with the following characteristics: M (60 μF, 70% tilt), B1 (60/60 μF, 70% tilt/3 ms pulse width), and B2 (60/20 μF, 70% tilt/3 ms pulse width) where the ratio of the phase 2 leading edge voltage to that of phase 1 was 0.5 for B1 and 1.0 for B2. E50 was measured by a Bayesian technique with a total of ten defibriilation shocks in each waveform and VF duration randomly. The E50 (J) for M, B1, and B2 were 131 ± 41, 57 ± 18* and 60 ± 26* with 10 seconds of VF duration, respectively, and 114 ± 62, 77 ± 45* and 72 ± 53* with 1 minute of VF duration, respectively (*P < 0.05 vs M). There was no significant difference in the E50 between 10 seconds and 1 minute of VF durations for each waveform. We conclude that (1) the E50 does not significantly increase with lengthening VF durations up to 1 minute regardless of the shock waveform, and (2) external exponential biphasic shocks are more effective than monophasic waveforms even with longer VF durations.
Transvenous Catheter Ice Mapping and Cryoablation of the Atrioventricular Node in Dogs
Authors: DUBUC MARC , ROY DENIS , THIBAULT BERNARD , DUCHARME ANIQUE , TARDIF JEAN‐CLAUDE , VILLEMAIRE CHRISTINE , LEUNG TACKKI , TALAJIC MARIO
Published: July 2006

While radiofrequency catheter ablation is very effective, it does not allow for prediction of success prior to full delivery of the energy. We investigated the use of cryoablation using a new catheter on the AV node to determine (1) if a successful site might be identified prior to the ablation itself, and (2) the parameters of cryoablation of the AV node using a new cryocatheter. In eight dogs, the cryoablation catheter was advanced to the AV node to produce transient high degree AV block by lowering the temperature to a minimum of −40°C (ice mapping). Transient high degree AV node block was obtained in seven of eight animals at a mean temperature of −39.9 ± 11.6°C. No significant pathological modification was found in all animals but one and, in all cases, electrophysiological parameters of the A V node measured before, 20 minutes, 60 minutes, and up to 56 days after cryoapplication were not significantly different. In the 12 other dogs, after ice mapping, cryoablation of the A V node was attempted with a single freeze‐thaw cycle in 6 dogs (group 1) and a double freeze‐thaw cycle in the other 6 dogs (group II). Chronic complete AV block was obtained in only one animal in group I compared to all animals in group II. Ablation of the A V node is effective with a double freeze‐thaw cycle using a percutaneous catheter cryoablation system. Ice mapping of the area allows for identification of the targeted site.
Percutaneous Cephalic Vein Approach for Permanent Pacemaker Implantation
Authors: SHIMADA HIROHIDE , HOSHINO KAZUO , YUKI MASAYOSHI , SAKURAI SHUMPEI , OWA MAFUMI
Published: July 2006

Implantation of permanent pacemaker leads into the cephalic vein within the deltopectoral groove is enhanced by introduction of a flexible guidewire into the brachial vein at the antecubital fossa, which is then advanced to the subclavian vein. The cephalic vein within the deltopectoral groove is easily found by incision with the guidewire as a marker. A pacing lead or leads can be inserted along the guidewire or by using a sheath advanced over the guidewire. The procedure was performed on 32 patients and the pacing leads of 28 procedures (DDD 15, VDD 9 and VVI 4) were inserted using the cephalic vein without complications.
Feasibility of Pacemaker Therapy After Dynamic Cardiomyoplasty
Authors: VAN DEN BERG MAARTEN P. , NAGELKERKE DICK , BROUWER RENE M.H.J. , MULDER HENK , DE BOER HANS , CRIJNS HARRY J.G.M.
Published: July 2006

A 54‐year‐old man presented with total atrioventricular (AV) block 3 months after dynamic cardiomyoplasty was performed because of heart failure due to idiopathic dilated cardiomyopathy. Though the cardiomyostimulator acted as a back‐up pacemaker, a DDDR pacemaker was implanted to optimize hemodynamics. During testing no cross‐sensing or cross‐stimulation between the pacemaker and the cardiomyostimulator was demonstrable. The synchronization delay, however, had to be adjusted.
Spurious Redetection of Sinus Rhythm by an Implantable Cardioverter Defibrillator During Spontaneous Ventricular Fibrillation
Authors: OTTO LYNN , MANN DAVID E. , KELLY PATRICIA A. , REITER MICHAEL J.
Published: July 2006

Implantable cardioverter defibrillator undersensing leading to delayed or aborted therapy delivery has been reported with induced arrhythmias and following failed defibrillator shocks. We describe a case in which spurious redetection of sinus rhythm during a spontaneous episode of ventricular fibrillation resulted in aborted device therapy.
Beat‐to‐Beat Repolarization Variability in LQTS Patients with the SCN5A Sodium Channel Gene Mutation
Authors: COUDERC JEAN‐PHILIPPE , ZAREBA WOJCIECH , BURATTINI LAURA , MOSS ARTHUR J.
Published: July 2006

Current techniques evaluating beat‐to‐beat variability of repolarization rely on accurate determination of T wave endpoints. This study proposes a T wave endpoint‐independent method to quantify repolarization variability in a standard 12‐lead ECG using a wavelet transformation. Our method was used to identify repolarization variability in long QT syndrome patients (LQTS) with the SCN5A sodium channel gene mutation. Using wavelet transformations based on the second Gaussian derivative, we evaluated repolarization variability in 11 LQTS patients with the mutation, 13 noncarrier family members, and 28 unrelated healthy subjects. Time‐domain repolarization variability parameters (SDRTo, SDRTm) and wavelet parameters describing temporal (beat‐to‐beat) variability of repolarization in time (TVT) and in amplitude (TVA) were analyzed. Reproducibility of wavelet parameters and relationship of wavelet‐based variability with heart rate and preceding RR interval were investigated. The wavelet‐based method quantified beat‐to‐beat variability of the entire repolarization segment (regardless of QT interval identification) providing insight into variability in repolarization morphology. Our method showed that SCN5A carriers have significantly increased repolarization variability in amplitude (23%± 14% vs 8 ± 4%, P < 0.001) and in time (14 ± 17 ms vs 3 ± 2 ms, P < 0.004) compared to noncarriers. Variability of repolarization amplitude was found to be heart rate dependent with variability decreasing with increasing heart rate. Relative error describing reproducibility of TVA and TVT was ± 5% and ± 10%, respectively. Our method quantifies repolarization variability in amplitude and in time without the need to identify T or U wave endpoints. Wavelet‐detected repolarization variability contributes to phenotypic identification of SCN5A carriers, with more pronounced beat‐to‐beat variability in repolarization amplitude than in time.
Intravenous Nitrates for Pharmacological Stimulation During Head‐Up Tilt Testing in Patients with Suspected Vasovagal Syncope and Healthy Controls
Authors: AERTS ARNAUD J. J. , DENDALE PAUL , DANIELS CATHY , MEYVISCH PAUL , KAUFMAN LEONARD , STROBEL GUNNAR , BLOCK PIERRE
Published: July 2006

Nitrates may be used for pharmacological stimulation during tilt testing for the diagnosis of vasovagal syncope. In this study we assessed the diagnostic value of intravenous nitrates during tilt testing in patients with a typical history of vasovagal syncope. Twenty patients and 23 controls were tilted at 707° for a maximum duration of 30 minutes. After a 10‐minute baseline supine phase, the test started with a continuous nitrate infusion at 1 μg/kg/min and increased every 5 minutes by 1 μg/kg/min, to a maximum of 6 μg/kg/min at the end of the test. The test was ended if the subjects developed a positive response (syncope or presyncope). Nineteen patients (95%) and 17 (74%) of the controls had a positive response. At test end sensitivity was 95%, but specificity was 26% and accuracy was 58%. Receiver operator characteristics (ROC) analysis revealed a maximum accuracy of 79% at 18 minutes, with a sensitivity of 80% and a specificity of 78%. Intravenous nitrates during tilt testing in patients with typical clinical criteria of vasovagal syncope is highly effective in provoking vasovagal syncope. Based on the ROC analysis, a maximum accuracy of 79% was attained at 18 minutes (at a dose of 4 μg/kg/min), suggesting a good diagnostic performance when tilt duration is limited to this point. A positive result requiring more than 18 minutes of stimulated tilting should be interpreted with caution, due to the accompanying considerable decrease of specificity.
Stable Electrical Performance of High Efficiency Pacing Leads Having Small Surface, Steroid‐Eluting Pacing Electrodes
Authors: DESHMUKH PRAMOD , CASAVANT DAVID , ANDERSON KATHY , ROMANYSHYN MARY
Published: July 2006

Previous experience with steroid‐eluting small electrode designs have described their increased pacing efficiency, yet some reports have questioned their electrical stability. We report our experience with a new pacing lead design incorporating small surface (i.e. 1.2 mm2), high impedance pacing electrodes. Medtronic Model 5034 ventricular pacing leads were implanted by a single physician in 167 patients. Of those, 96 patients had an additional Model 5534 atrial lead implanted. All patients were followed for at least 9 months. Microdislodgment, as defined by a sudden increase in pacing threshold accompanied by radiographic stability, was observed in 6 of 263 (2.3%) leads implanted. Of the 4/167 (2.4%) ventricular leads that exhibited electrical instability, only 2 were sustained. Importantly, neither was significant enough to result in loss of capture. The other two cases of ventricular electrode instability manifested as a transient threshold rise with eventual return to near the original values. By comparison, the atrial lead model exhibited a sudden and sustained pacing threshold rise 5 which was evident in two patients (2.1%) with neither requiring invasive intervention. For all remaining chronic leads, clinically acceptable electrical performance profiles were demonstrated. We conclude that low microdislodgment rates and stable electrical performance profiles can be achieved with the small electrode steroid‐eluting pacing electrodes as long as careful lead positioning and securing techniques are followed during implantation. We further suggest that successful high impedance lead design is critically dependent on its stiffness and mass characteristics.
Early Recurrence of Atrial Fibrillation After External Cardioversion
Authors: YU WEN‐CHUNG , LIN YUNG‐KUO , TAI CHING‐TAI , TSAI CHIN‐FENG , HSIEH MING‐HSIUNG , CHEN CHIEN‐CHENG , HSU TSUI‐LIEH , DING YU‐AN , CHANG MAU‐SONG , CHEN SHIH‐ANN
Published: July 2006

Early recurrence of atrial fibrillation (AF) has been reported to occur in a significant number of patients after internal cardioversion. However, information about early recurrence of AF after external cardioversion has never been reported. The present study was conducted to investigate the clinical and electrophysiological characteristics of early recurrence of AF and its role in failure of cardioversion in patients with chronic AF. Methods and Results: The study included 50 consecutive patients, age 69 ± 9, with a history of chronic AF for more than 3 months duration and electrical cardioversion. They were divided into two groups according to the presence (group 1) or absence (group 2) of early recurrence of AF. There were 13 (26%) patients in group 1 and 37 (74%) patients in group 2. The age, gender, duration of AF, left ventricular function, left atrial dimension, and underlying heart disease were similar between group 1 and 2. Forty‐five patients were successfully converted to sinus rhythm with a mean energy of 158 ± 57 J. Among those who failed to be converted to sinus rhythm, 4 (80%) belonged to group 1 and 1 (20%) belonged to group 2. The early recurrences of AF were initiated with consecutive APDs; but the numbers of APD in the first 30 seconds after cardioversion were similar between group 1 and 2. However, the coupling interval of the second APD was shorter in group 1 than group 2 (188 ± 22 vs 324 ± 59 ms, P = 0.003). Nine of the 13 early recurrences were prevented by an increase of shock energy (n = 3) or intravenous amiodarone infusion (n = 6). There were no differences in duration of follow‐up, recurrence rate, and time interval to recurrence between group 1 and group 2. Early recurrence of AF occurred in 26% of chronic AF patients who underwent external electrical cardioversion and was a major cause of failure in cardioversion. Early recurrence of AF was initiated by APDs with decreasing coupling intervals and could be prevented with an increase of shock energy or amiodarone.
Midodrine Hydrochloride in the Treatment of Vasovagal Syncope
Authors: MITRO PETER , TREJBAL DUSAN , RYBÁR RAFAEL
Published: July 2006

Therapy of vasovagal syncope is still a subject of debate. Various pharmacotherapies were proposed. However, they are often not tolerated or ineffective. The purpose of this prospective, nonrandomized study was to evaluate the usefulness of alpha‐agonist midodrine hydrochloride in the treatment of vasovagal syncope. Forty‐one patients (mean age 34 years, 18 men) with history of recurrent syncope and positivity of head‐up tilt testing were included (28 patients with type 1, 10 patients with type 2, 3 patients with type 3 according to VASIS classification). In all patients oral therapy with midodrine was started. Initial dose was 2.5 mg two times daily. When necessary, the dose was increased to 5 mg two times daily. Efficacy of treatment was assessed by repeated head‐up tilt testing after 1–2 weeks of therapy and by long‐term follow‐up. After midodrine hydrochloride treatment, 39 of 41 patients (95%) had no inducible presyncope or syncope on repeated tilt table testing. Effective dose was 2.5 mg two times daily in 25 patients and 5 mg two times daily in 16 patients. During a mean follow‐up period 19 ± 9 months, 38 of 39 patients (97%) with negative repeated tilt table test remained free of syncope recurrence.
AV Node Ablation and Pacemaker Implantation After Withdrawal of Effective Rate‐Control Medications for Chronic Atrial Fibrillation: Effect on Quality of Life and Exercise Performance
Authors: NATALE ANDREA , ZIMERMAN LEANDRO , TOMASSONI GERY , NEWBY KEITH , LEONELLI FABIO , FANELLI RAFFAELE , BEHEIRY SALWA , PISANO ENNIO
Published: July 2006

We assess whether AV node ablation and pacemaker implantation after discontinuation of effective rate‐control medical therapy for chronic atrial fibrillation had a positive impact on quality of life and exercise performance. To assess the possibility of a placebo effect following pacemaker implantation, the study included three groups of patients. Group 1 underwent an echocardiogram, treadmill exercise, and quality of life measurement 1 month prior to and 6 months following AV node ablation and pacemaker implantation associated with discontinuation of rate‐control medications. Group 2 underwent AV node ablation and pacemaker implantation without discontinuation of antiarrhythmic rate‐control drugs. Group 3 underwent pacemaker implantation without performing AV node ablation and continuing rate‐control medical therapy. At the 1‐ and 6‐month evaluation, the patients in group 1 showed a significant improvement of left ventricular ejection fraction, quality of life, and activity scores. The exercise duration and the maximal VO2 consumption, however, did not change significantly. A slight improvement of the quality of life and physical activity scores was observed in the group undergoing AV node ablation without withdrawal of medications. However, no significant changes were observed in the group receiving only the pacemaker without modification of medical therapy and with intact AV node conduction. In conclusion, in patients with chronic atrial fibrillation, discontinuation of effective rate‐control medical therapy followed by AV node ablation and permanent pacing appeared to improve quality of life and activity scores despite no change in exercise duration. The improvement observed does not seem to reflect a placebo effect.
Initial Clinical Experience with a Fully Automatic In‐Hospital External Cardioverter Defibrillator
Authors: MATTIONI THOMAS A. , NADEMANEE KOONLAWEE , BRODSKY MICHAEL , FISHER JOHN , RIGGIO DAVID , ALLEN BYRON , WELCH SUSAN , YBARRA RAUL A. , LIN DONGPING , DEAN EDNA
Published: July 2006

Sudden cardiac death due to ventricular tachyarrhythmia remains a significant problem in the in‐hospital setting. Although the probability of survival is closely correlated with the rapidity of a response by qualified personnel, response times can be prolonged, even in specialized care units. In an effort to decrease response time, a fully automatic external cardioverter defibrillator was recently devised. This device was evaluated in the in‐hospital setting to assess safety and efficacy. A total of 79 patients were studied in a multicenter trial. Patients were monitored with fully functional devices in the electrophysiology laboratory (51 patients) and in the cardiac care unit (28 patients). Performance of the device was assessed by comparing automatic responses to any sustained change in cardiac rhythm, either spontaneous or induced, to a retrospective review of stored ECG data and programmed parameters. During a total duration of 964 hours of monitoring, there were 99 episodes of sustained tachycardia. Therapy was appropriately delivered or advised in all episodes. Therapy was advised in one episode of supraventricular tachycardia. There were no episodes of inappropriate therapy delivery. There were no complications or adverse events. The device performed with a sensitivity of 100% and specificity of 98.8% with an average response time of 22 seconds. In conclusion, this automatic external defibrillator was safe, effective, and functioned as designed. Significant improvement in response time to life‐threatening ventricular tachyarrhythmia in the in‐hospital setting would be expected if this technology was widely adopted.
Tachycardia Induced Electrical Remodeling of the Atria and the Autonomic Nervous System in Goats
Authors: BLAAUW YURI , TIELEMAN ROBERT G. , BROUWER JAN , VAN DEN BERG MAARTEN P. , DE KAM PIETER J. , DE LANGEN CEES D.J. , HAAKSMA JAAP , GRANDJEAN JAN G. , PATBERG KORNELIS W. , VAN GELDER ISABELLE C. , CRIJNS HARRY J.G.M.
Published: July 2006

Atrial fibrillation (AF) shortens the atrial effective refractory period (AERP). To investigate the role of the autonomic nervous system during this so‐called electrical remodeling of the atria (ERA) and during recovery from ERA we analyzed heart rate variability (HRV). In 12 goats atrioventricular (300:150 beats/min) pacing was performed for 24 hours, interrupted at 4, 8, 16, and 24 hours for recording of 500 atrial (AA) intervals during sinus rhythm and measurement of the AERP430 msat 7.4 ± 0.6 sites. After 24 hours, pacing was stopped and the electrophysiological study and recording of the AA intervals was repeated at 4, 8, 16, and 24 hours after cessation of pacing. Time‐ and frequency‐domain parameters were computed from each 500 AA interval recording. After 24 hours of rapid pacing the AERP had shortened significantly (147 ± 5.6 to 102 ± 6.4 ms, P < 0.0001). No significant changes in HRV and dispersion of refractoriness (ΔAERP) (47 ± 7.1 to 44 ± 4.2 ms) were observed. After cessation of pacing, the AERP prolonged again (102 ± 6.4 to 135 ± 8.8 ms, P < 0.0001) and was paralleled by a significant increase in ΔAERP (44 ± 4.2 to 63 ± 7.1 ms, P = 0.01). Furthermore, HRV increased significantly. At each time point an inverse relation between the logarithmically transformed vagal parameter HF (InHF) and AERP was observed. We calculated the mean InHF for each goat using all time points and used the median value to divide the 12 goats into high and low vagal tone groups. We compared the degree of ERA and recovery from ERA for both groups. The AERP shortened 47.4 ± 6.5 versus 43.0 ± 5.0 ms (NS) for goats with high and low vagal tone, respectively. During recovery from ERA the AERP lengthened 23.6 ± 4.0 versus 42.5 ± 1.7 ms (P = 0.001) for goats with high and low vagal tone, respectively. Multivariate regression analysis indicated a short AERP as the single independent determinant of the inducibility of AF during ERA and recovery from ERA (P < 0.0001). During recovery from ERA, the AERP prolonged and vagal tone and ΔAERP increased. A high vagal tone during recovery from ERA was associated with a short AERP and an attenuated recovery of ERA.
“Optimum” Formulae for Heart Rate Correction of the QT Interval
Authors: HNATKOVA KATERINA , MALIK MAREK
Published: July 2006

The study investigated the performance of several generic QT/RR regression models in a dataset of QT and RR intervals obtained from resting electrocardiograms of 1,100 healthy subjects (913 male, mean age 33 ± 12 years). All the investigated models have three degrees of freedom and included the hyperparabolic and hyper‐hyperbolic models, algorithmic models, negative exponential models, and models involving inverse tangent, hyperbolic tangent, and inverse hyperbolic sign functions. For each generic model, the combination of parameters leading to the lowest regression residuum was found. The results of the study show that the goodness of the optimum fit is practically independent of the generic form of the regression model and that different datasets lead to different combinations of the numerical values of parameters of the corresponding regression models. The study concludes that the search for a universally applicable QT/RR regression model that would provide the best fit in all circumstances is most likely fruitless. Rather, individual studies such as those investigating drug related QT prolongation might benefit from establishing a best‐fit regression that would provide the optimum model for each particular dataset.
Video‐Assisted Endoscopic Removal of Infected Endocardial Pacemaker Lead with Large Floating Vegetation
Authors: CHU JAW‐JI , LIN PYNG JING , CHANG CHAU‐HSIUNG , WANG CHUN‐CHIEH , TAN PETER P.C.
Published: July 2006

The best management of pacemaker lead related endocarditis is complete surgical or percutaneous removal of the pacemaker system. Although the traditional surgical approach is via median sternotomy, we present two cases in which the lead and vegetations were removed using a video‐assisted endoscopic technique through a limited right submammary incision. In each case the patient was supported by partial extracorporeal perfusion. Additional tricuspid valve repair and atrial septal defect closure was performed in one case. The postoperative courses were uneventful, illustrating that, when compared to the conventional open heart surgical approach, the less invasive approach can be a safe and effective way to remove an infected foreign body from the right heart with increased comfort, fast recovery, and a better cosmetic result.
Pseudofracture of an ICD Lead
Authors: CAMOUS JEAN PIERRE , RAYBAUD FLORENCE , JOURDAN JACQUES
Published: July 2006

A proximal pseudofracture of a Medtronic 6936 defibrillating lead adjacent to the ICD pulse generator was found on X ray. At this site, the multifilar metallic connector joins the stimulating lead before coiling around it. Conventional X ray of the abdomen does not visualize this connection. During ICD replacement, lead impedance should be routinely measured.
Interelectrode (Accufix) Lead Fracture
Authors: TRIGANO ALEXANDRE J. , JULIENNE JEAN , FERRACCI ANGE , PAGANELLI FRANCK , FEKHAR SAMIR , RICARD PHILIPPE
Published: July 2006

An interelectrode fracture was diagnosed 7 years after the implantation of an AccufixTM lead. The lead body separated from the tip with the helix screwed into the atrial wall. The retention wire was intact and may have contributed to the lead rupture.
Arrhythmia Vulnerability Assessment Using Magnetic Field Maps and Body Surface Potential Maps
Authors: STROINK GERHARD , MEEDER ROBERT J.J. , ELLIOTT PHIL , LANT JOHN , GARDNER MARTIN J.
Published: July 2006

Magnetic field maps and body surface potential maps can be used to measure cardiac activity. The ability of magnetic and potential body surface maps to identify patients' vulnerable to recurrent sustained ventricular arrhythmia (VA) were compared. Magnetic field maps (MFM) and body surface potential mapping (BSPM) were obtained from 76 normal (N) subjects, 15 myocardial infarct (MI) patients, and 15 VA patients. QRST integral maps were calculated for each subject and nondipolar content was determined using Karhunen‐Loeve transform eigen‐maps. Although differences in nondipolar content were significant between the normal and patient groups (P = 2.4 × 10−5 for BSPM and P = 6.0 × 10−8 for MFM), differences in nondipolar content between MI and VA patients using QRST integral BSPM and MFM maps were not significant. The trajectory of the location of the maxima and minima on the map area during the QRS and ST‐T intervals were also constructed. Discrimination between MI and VA patients was based on intergroup differences in the amount of fragmentation of the trajectory plots. The ST‐T trajectory plots were significantly more fragmented (P < 0.0001 and P < 0.05 for MFM and BSPM, respectively) for VA than for MI patients. The ST‐T interval MFM and BSPM trajectory plots enabled separation of MI and VA patients with accuracies of 83% and 73%, respectively. These results suggest that repolarization MFM and BSPM extrema trajectory plots can be used effectively as a means of identifying patients at risk for VA.
Increase in Heart Rate Precedes Episodes of Ventricular Tachycardia and Ventricular Fibrillation in Patients with Implantable Cardioverter Defibrillators: Analysis of Spontaneous Ventricular Tachycardia Database
Authors: NEMEC JAN , HAMMILL STEPHEN C. , SHEN WIN‐KUANG
Published: July 2006

Patients with heart disease and decreased heart rate variability (HRV) have an increased risk of all‐cause mortality as well as arrhythmic death. The question of acute changes in HRV immediately preceding arrhythmic events remains unanswered. We analyzed data from patients with implantable cardioverter defibrillators who had ventricular tachycardia (VT) or ventricular fibrillation (VF) detected by the device. The device stores 1,000 consecutive RR intervals preceding the arrhythmic event detection and before device interrogation. Compared to this control segment, the mean heart rate (HR) increased prior to the arrhythmic event for both VT (88.5 vs 72.7 beats/min, P < 0.0005) and VF (85.4 vs 73.3 beats/min, P < 0.05) patients. No difference in HRV (as analyzed by a time‐domain, frequency‐domain [fast Fourier transform], and a nonlinear technique) has been detected. We estimated the amount of ectopic beats from the number of RR intervals that differed from the preceding RR interval by > 10%. The frequency of such beats was significantly higher in the prearrhythmic data segments than in the control segments for VT(10.7 vs 6.6/50 beats, P < 0.05) although not for VF(9.8 vs 6.1/50 beats, NS). We conclude that the HR and frequency of ectopic beats are higher prior to onset of the arrhythmic events, although HRV does not change markedly. These results are consistent with sympathetic activation being the predominant autonomic change prior to VT/VF onset in this patient population.
Electrophysiological Properties of the Left Atrium Evaluated by Coronary Sinus Pacing in Patients with Atrial Fibrillation
Authors: ISHIMATSU TAKASHI , HAYANO MOTONOBU , HIRATA TETSUYA , ILIEV IVAN I , KOMIYA NORIHIRO , NAKAO KOUJIRO , IWAMOTO KEIJI , TSUKAHARA KIMIO , SAKAMOTO RYOUJI , UEYAMA CHIAKI , YANO KATSUSUKE
Published: July 2006

Repetitive atrial firing (RAF), marked fragmentation of atrial activity (FAA), and interatrial conduction delay (CD) have been shown to be electrophysiological features of the atrium in patients with atrial fibrillation (AF). Moreover, it has been observed that atrial extrastimuli are more likely to induce AF when delivered from the right atrial appendage (RAA) than from the distal coronary sinus (CSd). We examined the electrophysiological properties of the atrial muscle by CS and RAA stimulation in patients with paroxysmal AF. Patients were divided into two groups: group I, consisting of 18 patients with clinical paroxysmal AF; and group II, consisting of 22 patients with various cardiac arrhythmias in which the substrate does not exist in the atrium. In group I, the following values of electrophysiological parameters of the atrium indicated that AF was more likely to be induced during RAA pacing than CSd pacing: atrial effective refractory period (RAA vs CSd: 201 ± 28 ms vs 240 ± 35 ms, P < 0.001), RAF zone (16 ± 25 ms vs 0 ± 0 ms, P < 0.03), FAA zone (38 ± 37 ms vs 5 ± 19 ms, P < 0.01), maximum interatrial conduction time (144 ± 19 ms vs 93 ± 19 ms, P < 0.0001) and CD zone (53 ± 21 ms vs 9 ± 18 ms, P < 0.0001). The values of the electrophysiological parameters of the atrium evaluated by CSd pacing in group I patients were not significantly different from those in group II patients. In conclusion, when coronary sinus stimulation is performed, electrophysiological properties of the atrium in patients with AF show a significant decrease in atrial vulnerability compared to stimulation from RAA and also show similar values to those in patients without AF. It might be suggested that the left posterior or posterolateral atrium is electrophysiologically stable even in patients with paroxysmal AF.
Reliability of Single‐Lead VDD Atrial Sensing and Pacing During Exercise
Authors: GUYOMAR YVES , GRAUX PIERRE , CARLIOZ ROLAND , MOULIN CORINNE , DUTOIT ALBERT
Published: July 2006

If atrial sensing ability of a single‐lead VDD pacemaker is well accepted at rest, the detection quality by atrial floating electrodes remains less recognized during exercise. The aim of this study was to verify, during tread‐mill test and a continous telemetry, the atrial tracking performance using four different leads technologies. From November 1994 to July 1997, 21 patients (71.3 ± 6.3 years old. 7 female, cardiopathy: 57%) were paced for isolated high degree (permanent: 13, paroxystic: 8) AV block. The implanted devices were the Vitatron Saphir/Brillant lead (13 patients), Intermedics Unity/425/04–13 lead (5 patients), Pacesetter Addvent (2 patients), and Biotronik Eikos (1 patient). The acute atrial signal amplitude was 1.66 ± 0.75 mV. The treadmill test used the chronotropic assessment exercise protocol after pacemaker reprogramming to detect atrial undersensing (AV delay ≤ 120 ms, no hysteresis, no flywheel, upper rate increase). The mean delay was 31.1 weeks (range 1–100). The testing duration was 6.1 ± 2.3 minutes, the number of steps was 3.3 ± 1.3 per patient, and the peak exercise rate was 135 ± 19 beats/min. At rest, complete atrial tracking was complete in 90% of the patients, and during testing in only 23.8% of the patients, while AV synchronization > 95% was present in 57.1%, > 90% in 71.4%, and > 85% in 90.4% of patients (Vitatron 13/13, Intermedics 3/5, Biotronik 1/1, and Pacesetter 1/2). During the recovery period synchronization was always > 95%. The mean P wave amplitude at rest was 1.1 ± 0.5 mV; during the first step, 1.04 ± 0.61 mV; second step, 0.94 ± 0.53 mV; third step, 0.82 ± 0.58 mV; fourth step, 0.67 ± 0.39 mV; and during recovery, 1.13 ± 0.67 mV. The mean P wave decrease signal at peak of exercise is 0.21 mV (from ‐1.31 to +0.5). In fact, P wave variations have several patterns: a decrease was measured in 7 patients, an increase in 2 patients, and no significant change in 7 patients. Single‐lead VDD P wave identification during exercise was almost accurate. However, often there was progressive lowering of atrial sensing with transient loss of AV synchrony.
Improved Efficacy of Anodal Biphasic Defibrillation Shocks Following a Failed Defibrillation Attempt
Authors: ROBERTS PAUL RICHARD , ALLEN STUART , SMITH DAVID CHARLES , URBAN JON FREDRIC , EULER DAVID EMERSON , KALLOK MICHAEL JOHN , MORGAN JOHN MARK
Published: July 2006

Although it is generally assumed that defibrillation becomes more difficult when the duration of VF is prolonged, after a failed defibrillation attempt, there is little information on the defibrillation efficacy of multiple shocks delivered at the same energy. The purpose of this study was to systematically examine the efficacy of a second shock delivered at the same or reversed polarity after a failed first shock. Defibrillation was attempted after 10 seconds of VF in 12 pigs (30–56 kg) using biphasic waveforms and a nonthoracotomy lead system. Shock energy was held constant for the first and second shocks at 50%–90% of the DFT. The second shock was delivered 10 seconds after a failed first shock. First and second shock polarity (first phase) was randomized to (+,+), (+,−), (−,−), (−,+). The incidence of successful defibrillation (for all polarities) was 12.3% for first and 49.1% for second shocks (P < 0.0001). Anodal first shocks had a 17.2% incidence of success as opposed to a 7.4% incidence of success with cathodal first shocks (P = 0.001). Anodal second shocks had a 55.5% incidence of success compared to a 42.7% incidence of success with cathodal second shocks (P = 0.008). There was no significant benefit from polarity reversal after a failed first shock (P = 0.29). In conclusion, less energy is required for successful defibrillation by a second shock after a failed first. The optimal configuration for first and second shocks is with the RV as anode. Polarity reversal of a second shock after a failed first does not affect the probability of second shock success.
Localization of Precise Origin of Idiopathic Ventricular Tachycardia from the Right Ventricular Outflow Tract by a 12‐Lead ECG: A Study of Pace Mapping Using a Multielectrode “Basket” Catheter
Authors: YOSHIDA YUKIHIKO , HIRAI MAKOTO , MURAKAMI YOSHIMASA , KONDO TAKAHISA , INDEN YASUYA , AKAHOSHI MAKOTO , TSUDA MAKOTO , OKAMOTO MITSUHIRO , YAMADA TAKUMI , TSUBOI NAOYA , HIRAYAMA HARUO , ITO TERUO , TOYAMA JUNJI , SAITO HIDEHIKO
Published: July 2006

Radiofrequency catheter ablation guided by pace‐mapping techniques has proven effective in eliminating idiopathic ventricular tachycardia (VT) originating from the right ventricular outflow tract (RVOT). A method for rapidly identifying the origin of VT from 12‐lead electrocardiogram (ECG) findings would be helpful for the catheter ablation procedure. The purpose of this study is to precisely localize the origin of idiopathic VT from the RVOT by a 12‐lead ECG from a study of multipoint pace mapping. In one patient with premature ventricular complex (PVC) and 3 with VT, a “basket” catheter was deployed in the RVOT for bipolar pacing from 56 sites in the endocardium of RVOT. Under fluoroscopy the pacing sites were classified into the septum and free wall. We investigated the QRS morphology in leads, I, II, and III; the depth of the QS wave in leads aVR and aVL; and the height of the initial r wave in leads V1 and V2. Pacing was captured in 30–47 of 56 sites (54%–84%). As the pacing sites changed from the anterior to posterior of the septum, the QS notch (‐) type in lead I shifted through rs to R, while a shift from R type to rR' or Rr' was noted in leads II and III. As the pacing sites changed from the anterior to posterior of the free wall, lead I showed a shift from the QS notch (+) type to R, while a shift from rR' to Rr'(or rR' unchanged) was found in leads II and III. The depth of the QS wave in leads aVR and aVL showed a tendency for aVR to be deeper than aVL toward the posterolateral attachment of both the septum and free wall, whereas aVL tended to be deeper than aVR toward the anterior attachment. The initial r waves in V1 and V2 became greater as the pacing site was positioned at a higher or more posterior location. These findings may provide more precise and clinically useful diagnostic information on the site of the origin of idiopathic VT originating from the RVOT by a 12‐lead ECG.
Interaction Between Autonomic Tone and the Negative Chronotropic Effect of Adenosine in Humans
Authors: KOU WILLIAM H. , MAN K. CHING , GOYAL RAJIVA , STRICKBERGER S. ADAM , MORADY FRED
Published: July 2006

Prior studies have demonstrated that sympathetic tone may influence the effects of adenosine on His‐Purkinje automaticity, and that enhanced vagal tone may influence its effects on the sinus node. However, the interaction between autonomic tone and the effects of adenosine on the sinus node in humans remains unknown. Therefore, this study was designed to investigate the interaction between different states of autonomic tone and the bradycardiac response of the sinus node to adenosine. In 11 patients without structural heart disease who underwent a clinically indicated electrophysiology procedure, the sinus cycle length was measured before and after a 12‐mg bolus of adenosine in the baseline state, during an infusion of 2 mcg/min of isoproterenol, after the administration of 0.2 mg/kg of propranolol, and again after the administration of 0.04 mg/kg of atropine. Adenosine significantly lengthened the sinus cycle length in the baseline state (760 ± 165 vs 909 ± 188 ms, P < 0.05), during isoproterenol infusion (516 ± 67 vs 766 ± 146 ms, P < 0.05), after propranolol (850 ± 153 vs 914 ± 143 ms, P < 0.05) and after the combination of propranolol and atropine (662 ± 76 vs 801 ± 121 ms, P < 0.05). The degree of lengthening in sinus cycle length was significantly greater (P < 0.05) during isoproterenol infusion (253 ± 157 ms, or 51%± 40%) than in the baseline state (149 ± 85 ms, or 20%± 12%), after propranolol (68 ± 53 ms, or 8%± 8%), and after propranolol and atropine (140 ± 110 ms, or 21%± 18%). The negative chronotropic effect of adenosine is influenced by autonomic tone. The effect of adenosine on the sinus node is accentuated by beta‐adrenergic stimulation and unaffected by beta‐adrenergic blockade or combined beta‐adrenergic and cholinergic blockade.