bluuebunny/crossref_metadata_2025 huggingface dataset:
Initial Experience with 1.5‐mm2 High Impedance, Steroid‐luting Pacing Electrodes
Authors: FOGEL RICHARD , PIRZADA FAROUK , CASAVANT DAVID , BOONE JOHN , BOWMAN ANTHONY , STEINHAUS DAVID , GILBERT MARCEL , VLIETSTRA RONALD , BELOTT PETER , PARSONNET VICTOR , TILTON GREGORY , WHITE MELVIN
Published: July 2006

In this human study, 21 atrial and 62 ventricular 1.5‐mm2 unipolar steroid‐eluting pacing electrodes were implanted in 64 patients. Pacing thresholds, lead impedance, and sensing measurements were measured via pacemaker telemetry within 24 hours postimplont, and at 1, 2, 3, 4, 6, 12. 24. and 52 weeks. Acute pacing impedances measured via a pacing systems analyzer were 1,039 ± 292 (atrial) and 1,268 ± 313 ohms (ventricular). A10%‐15% decline in the mean telemetered atrial and ventricular pacing impedances was observed at 1 week, but thereafter remained stable. Acute pacing thresholds at 0.5 ms were 0.5 ± 0.3 V (atrial) and 0.4 ± 0.1 V (ventricular). Filtered P and B wave amplitudes were 3.7 ± 2.3 mV and 14.9 ± 5.9 mV, respectively. In 21 patients, no complications related to the atrial electrode were observed. Of 62 patients with ventricular electrodes, 4 patients (6%) experienced complications and required surgical intervention. On these, causative factors included micro‐dislodgment (l patient), and perforation (l patient). Sudden unexplained exit block occurred late (> 6 weeks) in two patients. In the remainder of patients, pacing thresholds and sensed electrogram amplitudes remained stable throughout the 52‐week follow‐up period. Conclusions: The‐ present study validates that smaller surface (i.e., 1.5 mm2) steroid‐ eluting electrode designs offer excellent pacing and sensing performance with significantly higher pacing impedances. Although questions remain as to the cause of late exit block in two patients in this series, this relatively small surface electrode design offers promise toward achieving greater pacing efficiency and a theoretical 13%‐16% (minimum) enhancement in permanent pacemaker longevity.
Biphasic Defibrillation Using a Single Capacitor with Large Capacitance: Reduction of Peak Voltages and ICD Device Size
Authors: BLOCK MICHAEL , HAMMEL DIETER , BöCKER DIRK , BORGGREFE MARTIN , BUDDE THOMAS , ISBRUCH FRANK , SCHELD HANS H. , BREITHARDT GÜNTER
Published: July 2006

The volume of current implantable cardioverter defibrillators (ICD) is not convenient for pectoral implantation. One way to reduce the size of the pulse generator is to find a more effective defibrillation pulse waveform generated from smaller volume capacitors. In a prospective randomized crossover study we compared the step‐down defibrillation threshold (DFT) of a standard biphasic waveform (STD), delivered by two 250‐μF capacitors connected in series with an 80% tilt, to an experimental biphasic waveform delivered by a single 450μF capacitor with a 60% tilt. The experimental waveform delivered the same energy with a lower peak voltage and a longer duration (LVLDj. Intraopera‐tively, in 25 patients receiving endocardial (n = 12) or endocardial‐subcutaneous array (n = 13) defibrillation leads, the DFT was determined for both waveforms. Energy requirements did not differ at DFT for the STD and LVLD waveforms with the low impedance (32 ± 4Ω) endocardial‐subcutaneous array defibrillation lead system (6.4 ± 4.4 J and 5.9 ± 4.2 J, respectively) or increased slightly (P ‐ 0.06) with the higher impedance (42 ± 4 Ω) endocardial lead system (10.4 ± 4.6 J and 12.7 ± 5.7 /. respectively), However, the voltage needed at DFT was one‐third lower with the LVLD waveform than with the STD waveform for both lead systems (256 ± 85 V vs 154 ± 53 V and 348 ± 76 V vs 232 ± 54 V, respectively). Thus, a single capacitor with a large capacitance can generate a defibrillation pulse with a substantial lower peak voltage requirement without significantly increasing the energy requirements. The volume reduction in using a single capacitor can decrease ICD device size.
Influence of Different Conditioning Methods on Force and Fatigue Resistance in Chronically Stimulated Skeletal Muscles
Authors: KOLLER RUPERT , GIRSCH WERNER , HUBER LEOPOLD , RAB MATTHIAS , STOEHR HANS G. , SCHIMA HEINRICH , ALEXANDER M. , ROKITANSKY  , LOSERT UDO M. , WOLNER ERNST
Published: July 2006

A study was undertaken to compare different conditioning methods for the transformation of latissimus dorsi muscle into a fatigue resistant one for application in circulatory assist. In ten sheep four electrodes were sutured to the epineurium of the left thoracodorsal nerve for indirect electrical stimulation of the latissimus dorsi muscle. In six sheep a “carousel stimulation, ” a special multichannel stimulation, in combination with a recently developed conditioning protocol was used for muscle conditioning (multichannel method). In four sheep, a conventional stimulation protocol using single channel stimulation was applied for transformation of the muscle (single channel method). The final experiments were carried out when fatigue resistance was obtained. The maximum tetanic forces at different preloads were determined and fatigue resistance was tested during 20 minutes of continuous stimulation. Both conditioning patterns led to fatigue‐free chronic stimulation. Muscles conditioned by multichannel stimulation exhibited between 20% and 33% less force than the contralateral unconditioned muscles, whereas in the single channel group this loss was between 32% and 43%. Thus, the multichannel method revealed relatively superior in preserving muscle force for chronic stimulation.
Reproducibility of Electrophysiological Measurements in Cardiac Transplant Recipients
Authors: SCOTT CHRISTOPHER D. , HOLT NICOLA D. , DARK JOHN H. , McCOMB JANET M.
Published: July 2006

The clinical usefulness of certain electrophysiological measurements, particularly those of sinus node function, is limited by variation in autonomic tone resulting in poor reproducibility. The denervated transplanted heart is not susceptible to direct autonomic control and, therefore, electrophysiological measurements may be more reproducible in this group. To our knowledge, this hypothesis has not previously been systematically evaluated. Ten adult recipients underwent serial electrophysiological studies between 10–18 days after cardiac transplantation. Five studies were performed at 2‐hour intervals during a single day, between 9:00 a.m. and 5:00 p.m. Spontaneous cycle length (SCL) was recorded. Sinus node recovery time (SNRT), sinoatrial conduction time (SACT), and atrioventricular (AV) Wenckebach cycle length were measured using standard techniques. The effective refractory periods of the complete AV conducting system (AVERP), atrium (AERP), and ventricle (VERP) were measured. Corrected maximal SNRT was normal in all subjects. Mean coefficients of variation (Cv) for SCL, corrected maximal SNRT, and SACT were 2.8%, 7.4%, and 3.5%, respectively. AVERP was less than AERP in seven subjects, limiting further analysis. The mean Cv for AV Wenckebach cycle length was 2.1%. The mean coefficients of variation for AERP were 3.6% and 3.7%, and for VERP 3% and 3.3%, at 600‐ and 400‐ms drive cycle lengths, respectively. Previous studies report much greater variation in innervated subjects particularly of indices of sinus node function. Thus, the reproducibility of electrophysiological measurements of sinus and AV node function in the transplanted heart is better than in normal subjects. This may have important implications for the reliability of electrophysiological testing in transplant recipients.
Perforation of the Right Ventricle by Transvenous Defibrillator Leads: Prevention and Treatment
Authors: MOLINA J. ERNESTO
Published: July 2006

A series of 78 consecutive implants of the transvene PCD (Medtronic, Inc.) defibrillator system is presented and the occurrence of right ventricular perforation in 4 patients reported (5.2%). Diagnosis of perforation is made using four signs: (1) decrease in arterial blood pressure without any other explanation; (2) decrease in pulsatility of the cardiac silhouette as monitored by fluoroscopy; (3) increased size of the cardiac silhouette; and (4) abnormal position of the transvenous lead too far out toward the left ventricle along the pericardial outline. Perforation causes rapid and dramatic cardiac tamponade due to the large diameter and stiffness of the coil carrier lead. Immediate drainage of the hemopericardium must be carried out using the transxiphoid approach. The use of a thin blue‐coded lead stylet (0.014‐inch gauge) is recommended over the stiffer maroon‐coded stylet. Since treatment must be carried out immediately, it is advised that a surgeon either perform, assist, or be immediately available whenever one of these systems is implanted.
Demonstration of Syncope in Patients After Pacemaker Implantation: Role of Head‐Up Tilt Test to Distinguish Neurocardiogenic Vasodepressor Syncope From Pacemaker Syndrome
Authors: ABE HARUHIKO , KUROIWA AKIO
Published: July 2006

It is important to distinguish clinically neurocardiogenic syncope from pacemaker syndrome in patients after pacemaker implantation. We report two syncopal patients with AV sequential physiological pacemakers who displayed neurocardiogenic Vasodepressor syncope (VDS) during head‐up tilt (HUT) testing. Neurocardiogenic VDS, as a cause of syncope in patients following pacemaker implantation, might be involved in these patients as well as pacemaker syndrome. HUT is a useful diagnostic test in distinguishing neurocardiogenic VDS from pacemaker syndrome in patients with syncope following pacemaker implantation. Careful evaluations for diagnosis of pacemaker syndrome are needed in these patients.
Clinical Application of a Microcomputer System for Analysis of Monophasic Action Potentials
Authors: YUAN SHIWEN , WOHLFART BJÖRN , OLSSON S. BERTIL , BLOMSTRÖM‐LUNDQVIST CARINA
Published: July 2006

Computerized analysis of monophasic action potentials (MAPs) has rarely been reported in clinical setting. We developed a computer system featuring on‐line acquisition and user‐monitored automatic measurement of multichannel MAPs with the capability of manual corrections. This system has been used in 34 patients in whom two‐channel MAPs and 1‐lead ECG were digitized during sinus rhythm, pacing, and programmed stimulation (PS). In total, 41,413 MAPs in 212 data files were measured. The correct determination rate was 100% for MAP onset and plateau, 99.78% (95.76% during PS) for MAP baseline, and 99.96% (54.29% during PS) for QRS onset. The comparison between the computerized and manual measurements in 292 MAPs showed that the former highly agreed with the latter, with the limits of agreement, defined as mean difference ± 2 SD, being from ‐4.8‐4.9 ms for activation time and from – 4.1‐6.0 ms for MAP duration measurements. Using this system, two‐channel MAPs of more than 300 consecutive beats can be measured in a few minutes, which made it possible to determine the steady state of MAP duration individually, and evaluate the MAP changes during intervention in detail. The clinical routine procedure for testing the effective refractory period and several new MAP parameters were also evaluated using this system. Conclusion: The MAP measurement using this computer system is reliable, rapid and accurate; it can therefore replace the manual method and provide more useful information for clinical research.
Time‐ Versus Frequency‐Domain Analysis in Predicting Cycle Length of Inducible Ventricular Tachycardia After Myocardial Infarction
Authors: NOGAMI AKIHIKO , IESAKA YOSHITO , YAMAUCHI YASUTERU , GOYA MASAHIKO , TAKAHASHI ATSUSHI , KOIKE AKIRA , ITO HIROSHI , AONUMA KAZUTAKA , HIROE MICHIAKI
Published: July 2006

To determine whether time‐ and frequency‐domain analyses differ in their ability to predict sustained ventricular tachycardia (VT) induced by programmed ventricular stimulation, 60 consecutive patients with myocardial infarction and 30 healthy control subjects were evaluated. Programmed ventricular stimulation using three extrastimuli and signal‐averaged ECG recordings were performed in patients with myocardial infarction. Of the 60 patients, sustained monomorphic VT (SMVT) with cycle length (CL) ± 250 ms (slow SMVT) was inducible in 9, and SMVT with CL < 250 ms (fast SMVT) was inducible in 9. The durations of the filtered QRS (f‐QRS) at each high‐pass filter (25, 40, and 80 Hz) and the low amplitude signal (LAS) at 25‐Hz high‐pass filtering were significantly longer in the slow SMVT group than in the fast SMVT, no VT, or normal control group. The root‐mean‐ square voltages at 25‐Hz and 8Q‐Hz high‐pass filters in the slow SMVT group were significantly lower than in the fast SMVT, no VT, or normal control group. There was no significant difference in time‐ domain variables among fast SMVT, no VT, and normal control groups. The CL of the induced sustained VT was significantly correlated with the durations of f‐QRS and LAS, Concerning frequency‐domain variables (area ratio and factor of normality), there was no significant difference between slow and fast SMVT groups. Both the slow and fast SMVT groups had a significantly higher area ratio and a significantly lower factor of normality than the group with no VT or the normal control subjects. In conclusion, there were significant correlations between time‐domain variables and CL of SMVT, while there was no correlation when using frequency‐domain parameters.
Earlier Activation of the Distal than the Proximal Site of the Coronary Sinus May Represent Retrograde Conduction Through AV Node: Significance of Recording of Far Distal Coronary Sinus
Authors: SUZUKI FUMIO , TOSAKA TOSHIMASA , ASHIKAWA HIDENOBU , ASAMI KOHICHI , NAWATA HIROKO , ISHIHARA NAOKO , TERAI TOMOKO , MOTOKAWA KATSUHIKO , HIRAO KENZO , KAWARA TOKUHIRO , HIEJIMA KAZUMASA
Published: July 2006

During retrograde conduction through an accessory pathway (AP) or the atrioventricular (AV) node, earlier activation of the distal recording site than a more proximal site of the coronary sinus (CS) generally indicates retrograde conduction via a distally located AP. Thus, after successful ablation of a left‐sided AP, if the distal CS recording site is activated earlier than a more proximal site retrogradely, it is considered to suggest—in the absence of His‐bundle recording or more frequently in the setting of poor recording of the low septal right atrial electrogram—a conduction via a second AP (located more distally), and not conduction via the AV node. Yet, we hypothesized that retrograde conduction through the AV node may activate the far distal site of the CS (CSD) earlier than a more proximal site, as the anterior atrial wavefront, coming retrogradely from the AV node and traveling along the anterior mitral annulus, could reach the CSD earlier than a more proximal site. To test this we studied 18 patients with intact retrograde conduction via the AV node, but without evidence of an AP. The CSD was recorded by means of a quadripolar catheter (interelectrode distance of 2–5 mm); retrograde activation sequence at the distal (CSD1–2) versus proximal (CSD3–4) bipolar recording site was determined during ventricular stimulation. In 12 of 18 patients the CSD1–2 recording site was activated 5–10 ms earlier than the CSD3–4 recording site, in 3 of 18 patients the CSD1–2 site was activated 5 ms later than the CSD3–4 site; in the remaining 3 patients both recording sites were depolarized simultaneously. The results indicate that the CSD was often depolarized earlier than a more proximal site by impulses that conducted to the atria retrogradely via the AV node while the quadripolar recording catheter was placed at the CSD. This observation, al‐ though not well documented previously, suggests that the sequence of retrograde atrial activation in the CS should be studied carefully in consideration of the actual location of the mapping catheter in order to correctly diagnose the presence or absence of conduction via an AP.
Correlation Between Time‐Domain Measures of Heart Rate Variability and Scatterplots in Postinfarction Patients
Authors: COPIE XAVIER , HEUZEY JEAN‐YVES lE , ILIOU MARIE‐CHRISTINE , KHOURI RIDA , LAVERGNE THOMAS , POUSSET FRANÇOISE , GUIZE LOUIS
Published: July 2006

Heart rate variability (HRV) is usually measured in time or frequency domains. Beat‐to‐beat variability, which cannot be assessed by frequency‐domain analysis, and can only be assessed globally by time‐domain analysis, provides information concerning the nonlinear behavior of heart rate. This beat‐to‐beat variability can be displayed on Scatterplots, where each RR interval is plotted against the preceding RR interval. However, the relationship between Scatterplots and other measures of HRV is unknown. We studied the correlations between time‐domain measures and scatterplot length, width, and area in 50 postinfarction patients. Scatterplot length and width were measured after printing. Scatterplot area was calculated from length and width, assimilating the plot to an ellipse. Long‐term variability indexes (SDNN and SDANN) were strongly correlated with scatterplot length (r > 0.9, P < 0.0001), and short‐term variability parameters (pNN50 and variability index) with scatterplot width (r > 0.9; P < 0.0001). Scatterplots are, therefore, a simple way of providing information concerning long‐ and short‐term HRV. Furthermore, measurement of scatterplot width at different given RR intervals could be an approach to the evaluation of short‐term HRV for different heart rates. This could provide a simple way of assessing cardiac parasympathetic modulation at different heart rates.
Two Hearts Beating as One: Radiofrequency Ablation of the His Bundle in a Heterotopic Heart Transplant Patient
Authors: FENELON GUILHERME , GOETHALS MARC , BRUGADA PEDRO
Published: July 2006

We describe a 54‐year‐old man with heterotopic heart transplantation, who had severe exertional angina and dyspnea related to native heart ischemic disease. Because of drug resistant atrial fibrillation and atrial flutter of the native heart with fast ventricular response (130 beats/ min), right‐sided radiofrequency ablation of the His bundle was undertaken, followed by permanent pacemaker linkage of donor and native hearts. The procedure was successful and uneventful. Remarkable relief of symptoms was achieved.
Defibrillator Twiddler's Syndrome Causing Device Failure in a Subpectoral Transvenous System
Authors: CROSSLEY GEORGE H. , GAYLE DAVID D. , BAILEY JOHN R. , HAISTY WESLEY K. , SIMMONS TONY W. , FITZGERALD DAVID M.
Published: July 2006

Twiddler's syndrome is well described as a complication of cardiac pacing. Defibrillator twiddler's syndrome has been recently reported with abdominal implantations of epicardial and transvenous defibrillator systems. We report a case of a patient with a transvenous defihrillator system implanted with the pulse generator placed in the Subpectoral plane. The patient developed twiddler's syndrome, which resulted in retraction of both leads. This caused inappropriate shocks due to sensing both the atriai and ventricular electrograms. While the Subpectoral position leaves the generator deeper and more difficult for the patient to access, it may not lessen the chance of twiddler's syndrome. It is possible that the Subpectoral position may actually predispose the patient to this malady.
Influence of Age, Lead Axis, Frequency of Arrhythmic Episodes, and Atrial Dimensions on P Wave Triggered SAECG in Patients with Lone Paroxysmal Atrial Fibrillation
Authors: MICHELUCCI ANTONIO , PADELETTI LUIGI , CHELUCCI ANDREA , MEZZANI ALESSANDRO , PORCIANI MARIA C. , CARUSO FEDERICO , LEBRUN EMANUELE , BACCI FRANCESCA , MARTELLI MOIRA , GENSINI GIAN FRANCO
Published: July 2006

Signal‐averaged P wave of 42 patients with lone paroxysmal atrial fibrillation (PAF) and 29 normal subjects (N) were recorded, using three orthogonal leads and analyzed in the time and frequency (entire P wave or a 100‐ms segment ranging from 75 ms before to 25 ms after the end of P wave) domains. PAFs were divided into a group of 12 having ≥ 2 attacks a month (HF) and a group of 30 having ≤ 2 attacks a year (LF). Statistically significant differences were absent with regard to ages of PAF and N; ages of HF, LF, and N at the time of signal‐averaged ECG; ages of HF and LF at the time of the first arrhythmic episode; and elapsed times from the first episode. Length of P wave and some frequency‐domain parameters were found to be significantly correlated with age. PAF showed a significantly longer duration of P wave in the frontal plane using the time‐domain analysis. Frequency analysis was found to be useful in evaluating the influence of attack frequency. HF showed significantly higher values of some frequency‐domain parameters than LF and N, while the three groups did not differ for time‐domain analysis. P wave duration and frequency content of the three orthogonal leads proved to be significantly different in PAF and N. Right and left atrial echocardiographic dimensions proved to be higher (even if within normal limits) in HF than in LF and N. Results suggest that frequency analysis should be performed on the entire P wave.
A Critical Appraisal of Quantitative Spectro‐Temporal Analysis of the Signal‐Averaged ECG:Predicting Arrhythmic Events After Myocardial Infarction
Authors: BLOOMFIELD DANIEL M. , SNYDER JONATHAN E. , STEINBERG JONATHAN S.
Published: July 2006

The objective of this study was to determine if spectra‐temporal analysis of the signal‐averaged ECG (SAECG) predicts spontaneous sustained ventricular tachyarrhythmias and sudden death in patients prospectively followed after myocardial infarction (MI). A SAECG was recorded in 177 patients 9 ± 5 days after MI. Spectro‐temporal analysis of the SAECG involved incrementing a Hanning window every 3 ms beginning 20 ms before the end of the QRS complex and extending into the ST segment. Quantitative analysis was performed using a cross‐correlation function to create a normality factor. A normality factor < 0.3 was deemed abnormal. The SAECG was abnormal in 41 % of patients using time‐domain analysis and 44% of patients using spectra‐temporal analysis. There was no correlation between an abnormal SAECG in the time domain and the frequency domain. Patients with inferior wall MI were more likely to have an abnormal spectra‐temporal map (odds ratio 2.26, P < 0.05). Time‐domain analysis of the SAECG (relative risk (RE) 2.6) was a statistically significant univariate predictor of arrhythmic events. Spectra‐temporal analysis of the SAECG was only weakly (RR 1.8) and not significantly (P = 0.15) associated with the spontaneous occurrence of these arrhythmias. When both time‐domain analysis and spectra‐temporal analysis of the SAECG were abnormal, the relative risk for an arrhythmic event was increased by 3.3‐fold. Quantitative spectra‐temporal analysis of high frequency signals within the SAECG cannot by itself predict the occurrence of spontaneous ventricular arrhythmias in patients after MI.
Lead Extraction in Young Patients With and Without Congenital Heart Disease Using the Subclavian Approach
Authors: A.FRIEDMAN RICHARD , VAN ZANDT HEIDI , COLLINS ELIZABETH , LEGRAS MARC , PERRY JAMES
Published: July 2006

Pacemaker lead removal using interlocking stylets and dilator sheaths has greatly reduced the need for major surgical intervention when lead extraction is required. Previous reports have shown the utility of this method in older patients, most of whom have anatomically normal hearts. The purpose of this study is to report the results of this technique in young patients with and with‐out congenital heart disease. There were 13 patients (M:F = 7:6) aged 9–26 years (median 13). Congenital heart disease was present in 8 of 13 patients. A total of 17 leads required removal; they had been implanted for 54 ± 24 months (range 19–94). Leads were removed from the left subclavian vein (13) or right subclavian vein (4) only. Seventeen of 18 leads were completely removed and one partially retained in the left subclavian vein. New leads were implanted from the same vein in 11 of 13 patients. Interlocking stylets and metal or flexible dilator sheaths were used in all cases except two. There was one surgical complication: a late wound dehiscence, which was easily managed. No patient required a transfusion, and there was no structural damage noted in any patient on the postoperative echocardiogram. We conclude that lead removal using interlocking stylets and dilator sheaths from the subclavian approach is an effective technique that can be used in young patients, including those with congenital heart disease.
Prospective Evaluation of Infrahisal Second‐Degree AV Block Induced by Atrial Pacing in the Presence of Chronic Bundle Branch Block and Syncope
Authors: PETRAČ DUBRAVKO , RADIĆ BERISLAV , BIRTIĆ KREŠIMIR , GIUROVIĆ JOSIP
Published: July 2006

The value of nonfunctional infrahisal second‐degree atrioventricular (AV) block induced by incremental atrial pacing was prospectively examined in 192 patients with chronic bundle branch block (BBB) and syncope. We compared 174 (91 %) patients with normal response to atrial pacing (Group I) to 18 (9%) patients with atrial pacing induced nonfunctional infrahisal second‐degree AV block (Group II). Patients in group I had higher incidence of organic heart disease, ventricular tachycardia induction, and retrograde ventriculoatrial conduction (P < 0.001, P < 0.05, P < 0.01, respectively), while patients in group II had higher incidence of primary conduction disease and prolonged H‐V intervals (P < 0.001, P < 0.01, and P < 0.001). During mean follow‐up period of 65 ± 34 months for group I, and 68 ± 35 months for group II, a development of spontaneous second‐ or third‐degree AV block was higher in group II (14/18 [78%]), than in group I (15/174 [9%]) (P < 0.001). The site of AV block was infrahisal in all patients in group II, and in 10 of 15 patients in group I. Because of the prophylactic pacing in all patients in group II, the incidence of sudden death was similar among the two groups, but patients in group I had higher incidence of cardiac death (P < 0.05). Conclusion: In patients with chronic BBB and syncope, a nonfunctional infrahisal AV block induced by incremental atrial pacing identified patients with particularly high risk of development of spontaneous infrahisal AV block. Therefore, permanent cardiac pacing is absolutely indicated in these patients.
Acute and Chronic Changes in Atrial Natriuretic Factor Induced by Ventricular Pacing: A Self Controlled Clinical Trial
Authors: CABELLO JUAN B. , BORDES PASCUAL , MAURI MONTSERRAT , VALLE MARIA , QUILES JUAN A.
Published: July 2006

A self controlled clinical trial was carried out to study the acute and chronic effects of ventricular pacing (VVI) on the atrial natriuretic factor (ANF). Eleven people were selected from a pool of 20 DDD paced patients. Pacemakers were programmed to the VVI mode for 1 month and their effectiveness tested by ECG at rest and after an effort test. ANF was measured by radioimmunoassay at baseline, after 15 minutes, and again 1 month after programming. The reliability of the radioimmunoassay was confirmed using the coefficients of variation between (12.5%) and within assay (9.7%). Data analysis was done using Wilcoxon's test. Our results showed that the onset of WI pacing led to a sudden sharp rise in ANF in all patients (P < 0.0001). During VVI pacing, three patients were dropped from the study (2 were withdrawn because of symptoms and 1 voluntarily withdrew). After 1 month of WI pacing, a significant increase of ANF above the baseline was observed (P < 0.05). The results showed that ventricular pacing led to an immediate rise in ANF and, that with long‐term VVI pacing, there was an increase in ANF levels as well. The role of these findings in the pathophysiology of the pacemaker syndrome calls for further research.
Overnight Heart Rate and Cardiac Function in Patients with Dual Chamber Pacemakers
Authors: CHEW PAUL H. , BUSH DAVID E. , ENGEL BERNARD T. , TALAN MARK I. , ABELL R. TRACY
Published: July 2006

Animal data indicate that chronic, overnight pacing at normal evening heart rates impairs cardiac function. We examined the relationship of pacing rate and cardiac function in nine patients with dual‐chamber pacemakers. We investigated two, 3‐week pacing regimens (80 and 50 ppm: DDD mode) in a cross‐over design. Doppler echocardiograms were performed at 1700 hours (PM) and 0600 hours (AM) at the end of each regimen. Ventricular function and preload decreased overnight (PM vs AM) with both pacing regimens. Compared to the morning values, the ratio of preejection to ejection time (PEP/ET) rose (0.43 vs 0.46), while the mean velocity of circumferential fiber shortening (Vcf) fell (1.16 cm/s vs 1.11 cm/s). Stroke volume (SV) (61 mL vs 53 mL) and ejection fraction (EF) also fell (0.56 vs 0.53) in the morning, End‐diastolic volume (EDV) (94 mL vs 88 mL) decreased in the morning, as did the ratio of passive to active filling (E/A) (1.06 vs 0.96). Iscvolumic relaxation time(91 msvs 101 ms) increased overnight at both pacing rates. Systolic function decreased at 80 ppm relative to 50 ppm at both times of day. SV fell (54 mL vs 61 mL), while both EDV (92 mL vs 90 mL) and end‐systolic volume (ESV) increased (43 mL vs 40 mL). Contractility measured by Vcf(1.09 cm/s vs 1.18 cm/s) and PEP/ET (0.49 vs 0.41) was reduced at 80 ppm. The heart needs to rest at night by slowing its rate of contraction. Pacing at 80 ppm impairs systolic and diastolic ventricular function compared to 50 ppm. Longer term consequences of ostensibly physiological pacing rates merit inquiry, particularly in those with preexisting cardiac dysfunction.
Atrial Flutter Mapping and Ablation I
Authors: COSIO FRANCISCO G. , ARRIBAS FERNANDO , LÓPEZ‐GIL MARÍA , PALACIOS JOSÉ
Published: July 2006

Endocardial mapping has led to a detailed knowledge of reentry mechanisms in atrial flutter. Multipolar and deflecting tip catheters allow recording local electrograms from multiple areas of the right atrium, and from the coronary sinus. In common flutter, with the typical “sawtooth” pattern, there is circular activation of the right atrium in a “counterclockwise” direction, descending in the anterior and lateral walls, and ascending in the septum and posterior wall. Superior and inferior vena cava, linked by a “line” of functional block in the posterolateral wall, make the central obstacle for circular activation. The cranial and caudal turning points are the atrial “roof,” and the isthmus between the inferior vena cava and the tricuspid valve. Complex conduction patterns, probably including slow conduction are detectable in the low septal area, around the coronary sinus. Atypical flutter, without the sharp negative deflections of common flutter, sometimes shows circular activation in the right atrium, rotating in the opposite direction of common flutter (clockwise). Other atypical flutters show no circular right atrial activation, and only partial data from coronary sinus activation, combined with the response to atrial stimulation (entrainment) allow the diagnosis of left atrial reentry, without a precise delimitation of the circuits. In patients having undergone cardiac surgery, atypical flutter may be based on reentry around surgical scars. To our knowledge, the mechanism of type II flutter has not been disclosed in humans.
Internal Cardioversion in Two Patients with Atrial Fibrillation Refractory to External Cardioversion
Authors: COOPER RANDOLPH A.S. , JOHNSON ERIC E. , KANTER RONALD J. , MERRILL JAMES J. , SORENTINO ROBERT A. , WHARTON J. MARCUS
Published: July 2006

A‐26year‐old man underwent an electrophysiological study for evaluation of a history of congenital heart disease, presyncope, and wide complex tachycardia. During the study the patient developed sustained atrial fibrillation with a rapid ventricular response. A 17‐year‐old man with a history of sick sinus syndrome developed sustained atrial fibrillation. Both patients failed four attempts at external Cardioversion with a maximum delivered energy of 360 J. Low energy Cardioversion was successful in both patients using biphasic waveforms and internal transvenous defibrillation electrodes. Internal Cardioversion using a transvanous electrode system can be successful in patients with atrial fibrillation refractory to external Cardioversion.
Signal‐Averaged ECG Prior to and Serially After Thrombolytic Therapy for Acute Myocardial Infarction
Authors: BEAUREGARD LOU‐ANNE M. , WAXMAN HARVEY L. , VOLOSIN ROSEMARY , VOLOSIN KENT J. , KURNIK PETER B.
Published: July 2006

Signal averaging has been performed to evaluate late potentials following infarction and the administration of thrombolytic therapy. Most studies have recorded signal‐averaged electrocardiograms (SAECGs) at least 12 hours after the onset of the infarction. In this study, SAECGs were recorded before thrombolytic therapy and serially over 7–10 days following infarction in 21 patients. The high frequency QRS duration was significantly shortened at 1 and 24 hours compared to presentation (96.8 ± 11.3 ms and 93.4 ± 8.0 ms vs 103.3 ± 14.3 ms, respectively, P < 0.05) and there was an increase in the terminal voltage over time, significant at 1 hour and 3 days (57.3 ± 29.1 μV and 58.6 ± 44.7 μV vs 44.4 ± 35.5 μV, respectively, P < 0.01). Five patients met criteria for ventricular late potentials on at least one SAECG. The prevalence of late potentials was higher in patients with Q wave infarctions, or with occluded infarct related arteries. These changes in myocardial activation may be related to ischemia and reperfusion, and may not correlate with the development of a fixed substrate for reentry.
Benefits and Limitations of Rate Adaptive Pacing Under Laboratory and Daily Life Conditions in Patients with Minute Ventilation Single Chamber Pacemakers
Authors: OSSWALD STEFAN , LEIGGENER CHRISTOPH , BUSER PETER T. , PFISTERER MATTHIAS E. , BURCKHARDT DIETER , BURKART FELIX
Published: July 2006

Rate adaptive pacing has been shown to improve hemodynamic performance and exercise tolerance during acute testing. However, there remain concerns about its benefit in daily life and possible complications incurred by unnecessary pacing. This double‐blind crossover study compared the benefit of rate adaptive (SSIR) versus fixed rate (SSI) pacing under laboratory and daily life conditions in 20 rate incompetent patients with minute ventilation single chamber pacemakers (META II). The heart rate (HR) response during three different exercise tests (treadmill, bicycle ergomctry, walking test) was correlated with the Holler findings during daily life in either pacing mode. The maximal HR was significantly higher in the SSIR‐mode compared to the SSI‐mode, both during laboratory testing (treadmill: 123 ± 15 vs 93 ± 29 beats/min: ergometry: 118 ± 15 vs 89 ± 27 beats/min; walking test: 127 ± 9 vs 95 ± 26 beats/min, all P values < 0.01) as well as during daily life (Holter: 126 ± 13 vs 103 ± 24 beats/min, P < 0.01). On Holter, the average HR (71 ± 14 vs 71 ± 8 beats/min) and the percentage of paced rhythm (54 % vs 62%, SSI‐ vs SSIR‐mode, P = NS) were not different in either mode. However, despite a 30% rate gain in the SSIR‐mode, the exercise capacity remained unchanged, and only 38% of patients preferred the SSIR‐mode. Minute ventilation pacemakers provide a physiological rate response to exercise. Irrespective of the protocol used, the findings of laboratory testing are comparable to those during daily life. However, patient selection for rate adaptive single chamber pacing should be made with caution, since the objective benefit of restoring normal chronotropy may subjectively be negligible for most patients.
Asymptomatic Brady arrhythmias as a Marker for Sleep Apnea: Appropriate Recognition and Treatment May Reduce the Need for Pacemaker Therapy
Authors: STEGMAN SUSAN S. , BURROUGHS JEFFERSON M. , HENTHORN RICHARD W.
Published: July 2006

Sleep apnea is associated with many adverse cardiovascular sequelae, including hypertension, nocturnal angina, decreased cardiac output, and bradyarrhythmias. The purpose of this study was to determine if patients referred for pacemaker therapy with asymptomatic bradyarrhythmias have underlying sleep apnea as the etiology of their bradyarrhythmias. This study included eight patients (7 males, 1 female) referred to a cardiac electrophysiology practice for pacemaker therapy. Patients included had asymptomatic bradyarrhythmias that consisted of severe sinus bradycardia, second‐degree atrioventricular block, and complete heart block. In 7 of 8 patients, the bradyarrhythmias occurred at night or during the day while asleep. No patients were conditioned athletes. Symptoms often associated with bradyarrhythmias, such as lightheadedness and syncope, were not present. However, seven patients had at least one symptom suggestive of sleep apnea, such as excessive daytime fatigue, snoring, cessation of breathing during sleep (apnea), or frequent nighttime awakenings. Overnight polysomnography studies were obtained on patients who had one or more symptoms suggestive of sleep apnea. In this study 7 of 8 patients (88%) referred for pacemaker therapy with asymptomatic bradyarrhythmias were documented bv polysomnography to have sleep apnea. When treated with either sleep position modification, nasal continuous positive airway pressure (nasal CPAP), or tracheostomy, all seven patients had improvement in sleep apnea symptoms and remained asymptomatic from their bradyarrhythmias without pacemaker therapy over an average follow‐up period of 22 months. One patient without symptoms suggestive of sleep apnea declined pacemaker therapy and remained asymptomatic. From these results, we concluded that asymptomatic transient bradyarrhythmias may suggest a diagnosis of sleep apnea. The evaluation of a patient referred for pacemaker therapy with asymptomatic bradyarrhythmias should include questions related to sleep apnea symptoms. Establishing the diagnosis of sleep apnea may reduce the need for pacemaker therapy and permit appropriate treatment of the underlying cause of these bradyarrhythmias.
Safe Performance of Magnetic Resonance Imaging on Five Patients with Permanent Cardiac Pacemakers
Authors: GIMBEL J. ROD , JOHNSON DELOS , LEVINE PAUL A. , WILKOFF BRUCE L.
Published: July 2006

Five patients with permanent cardiar pacemakers (Pacesetter models 261. 283. 2020, 2022) underwent magnetic resonance imaging (MRI). Only one patient (underlying rhythm asystole) was pacemaker dependent. A variety of pacing configuration (single and dual chamber: unipolar and bipolar: sensor and nonsensor driven) were scanned. A thorough evaluation of each pacing system was performed before and after scanning including determination of pacing and sensing thresholds. During MRI the patient was monitored using either ECG, pulse oximetry, or direct voice contact. In four patients heavy dressings were applied over the pacemaker pocket site. Patients were asked to report any symptoms experienced during MRI. Results: The four nonpacemaker dependent patients remained in sinus rhythm throughout the MRI. During and after the MRI all pacemakers continued to function normally except for one transient pause of approximately 2 seconds (noted by pulse oximeter) toward the end of the scan. This occurred in pacemaker dependent patient with a unipolar dual chamber device programmed DOO. No patient experienced any lorque or heat sensation. Conclusion: When appropriate strategies are used our experience suggests that MRI may be performed when necessary with an acceptable risk‐benefit ratio to the patient. It is unclear whether the isolated pause that was observed was due to the effect of the MRI, an artifact with the monitoring system, or oversensing by the pacemaker. Appropriable patient selection, close monitoring during the scan, and follow‐up after MRI are of paramount importance. Further stydy is necessary to refine the appropriate stralegies that could be used to consistently perform MRI sately in a selected pacemaker population.
Electrophysiological Findings in Idiopathic Recurrent Ventricular Fibrillation: Special Reference to Mode of Induction, Drug Testing, and Long‐Term Outcomes
Authors: AIZAWA YOSHIFUSA , NAITOH NAOKI , WASHIZUKA TAKASHI , TAKAHASHI KAZUYOSHI , UCHIYAMA HIROHIDE , SHIBA MASAMI , SHIBATA AKIRA
Published: July 2006

Electrophysiological studies can be useful in the presence of idiopathic ventricular fibrillation (VF) and may be used when selecting antiarrhythmic drugs. However, the yield, the mode, and the long‐term reproducibility of the induction of VF have not yet been fully elucidated. Eight patients with idiopathic VF underwent electrophysiological study. The mean age (± SD) was 45 ± 17 years. Six were males and two were females. Diagnosis was done by exclusion. VF was induced in 6 (75%) of 8 patients using double extra stimuli at coupling intervals of 233 ± 39 and 191 ± 20 ms for the first and second extra stimuli, respectively. Of note, VF was induced by stimulation exclusively at the origin of the premature ventricular beat, which was the first complex of VF in two patients. In another patient, VF was initiated by two premature stimuli and also by a pause produced by rapid pacing. The inducibility of VF was reproduced 9–18 months after the first induction in all of the four patients studied. When the ability of antiarrhythmic drugs to suppress VF inducibility was confirmed, no recurrence was observed during the follow‐up period of 40–160 months, but a recurrence of VF was observed in one of two nonresponders. In one patient, amiodarone administration failed in preventing VF induction 9 months after initiation of therapy, and reassessment of long‐term drug‐efficacy might be indicated in some patients. In conclusion, idiopathic VF was highly inducible (75%) with double extra stimuli. In this study, it was induced from a specific site (2/8) or by a pause (1/8). Induction of VF seemed to be reproduced 9–18 months after the first study. The outcome was considered favorable when the inducibility of VF was suppressed by antiarrhythmic drugs.
Evaluation of Asynchronous Left Ventricular Relaxation by Doppler Echocardiography During Ventricular Pacing with AV Synchrony (VDD): Comparison with Atrial Pacing (AAI)
Authors: STOJNIĆ BOJAN B. , STOJANOV PETAR L. , ANGELKOV LAZAR , PAVLOVIĆ SINIŠ A U. , RADJEN GORAN S. , VELIMIROVIĆ DUŠAN B.
Published: July 2006

The effect of right ventricular pacing on left ventricular relaxation was studied in 13 patients (age 62 ± 3 years), with the atrial sensing ventricular pacing mode (VDD). A control group of similar age (64 ± 4 years) consisted of 11 patients with atrial pacing (AAI). The timing of events was determined in both groups at similar R‐R intervals (921 ± 77 ms vs 967 ± 37 ms). The loading conditions as estimated by peak systolic wall stress (afterload) and end‐diastolic left ventricular dimensions (preload) were approximately the same in both groups. The ratio of late to early filling velocities were similar in both groups. Dominant changes were: increased preejection period (142 ± 13 ms vs 95 ± 15 ms); and higher velocities of isovolumic relaxation flow (60 ± 34 cm/s vs 25 ± 4 cm/s) in patients with ventricular pacing. The isovolumic relaxation time was longer in patients with VDD pacing (127 ± 14 ms vs 108 ± 12 ms). Anterior systolic interventricular septal motion (paradoxal motion) was recorded in nine patients with VDD pacing and in none of the patients with AAI pacing. Isovolumic relaxation flow was detected during atrial pacing in five (45%) patients and in 13 (100%) patients during atrial sensing ventricular pacing, indicating asynchronous left ventricular relaxation. This data shows that VDD pacing compared to atrial pacing resulted in an altered activation pattern of the left ventricle, associated with delayed onset, asynchronous contraction with interventricular septal motion abnormalities and prolonged asynchronous left ventricular relaxation with abnormal motion manifested by the presence of isovolumic relaxation flow.
Effect of Changing Capacitors Between Phases of a Biphasic Defibrillation Shock
Authors: WALCOTT GREGORY P. , ROLLINS DENNIS L. , SMITH WILLIAM M. , IDEKER RAYMOND E.
Published: July 2006

Background: In this study, we examined the effect of changing capacitor values between phases of a biphasic waveform with the goal of lowering leading edge voltage (LEV), total delivered energy (TDE), and total stored energy (TSE). Methods: Defibrillation thresholds were determined in 18 open‐chest swine using epicardial patch electrodes. In part I, three combinations of capacitors were tested: 150:150 μF; 150:300 μF; and 300:150 μF. Waveform durations were 6/0, 6/2, 6/4, 6/6, and 6/8 ms. In part II, phase 1 capacitance was 150 μF. Three phase 2 capacitance values were used: 150 μF; 75 μF; and 37.5 μF. Phase 2 LEV was a multiple of phase 1 trailing edge voltage: × 0.5: × 0.75; × 1; × 2; × 3; and × 4. A 3.5/2.0 ms biphasic waveform was used. In part III, thresholds were determined for two sets of capacitor values, which can be created by switching a pair of capacitors from in parallel to in series, 150:37.5 μF and 300:75 μF, and nine waveform durations, 4/0, 4/2, 4/4, 6/0, 6/3, 6/6, 8/0, 8/4, and 8/8 ms. Results: In part I, the 300:150 μF system defibrillated with the lowest LEV. TDE and TSE were not different for any of the biphasic waveforms tested except for the 6/8 ms, which was higher. In part II, there was no difference in LEV among any of the three phase 2 capacitor values. LEV was lowest for the × 2, × 3, × 4 multipliers. Peak voltage was lowest for the × 1 and × 2 multipliers. TDE was lowest for the × 0.5, × 0.75, × 1, and × 2 multipliers. In part III, the 300:75 μF system defibrillated at a lower LEV than did the 150:37.5 μF system. The 150:37.5 μF system defibrillated at a lower total delivered energy than did the 300:75 μF. Conclusion: These results suggest that defibrillation can be accomplished with lower LEV, TDE, and TSE if two capacitors are switched from a parallel configuration to a series configuration between phases of the biphasic waveform.
Thoracoscopic Approach to Implantable Cardioverter Defibrillator Patch Electrode Implantation
Authors: OBADIA JEAN‐FRANÇOIS , KIRKORIAN GILBERT , RESCIGNO GIUSEPPE , EL FARRA MAZEN , CHASSIGNOLLE JEAN‐FRANÇOIS , TOUBOUL PAUL
Published: July 2006

Even if transvenous lead system for automatic implantable Cardioverter defibrillators (ICDs) has been one of the main surgical advances in the recent past, its major limitation is the high defibrillation thresholds in some cases. Thus, an additional patch may be required and implanted either in a subcutaneous position or in an epicardial position. We describe another possibility: the implantation of extrapericardial patch under video‐thoracoscopic control. This new technique allows a deep implantation of the whole material without thoracotomy. Seven patients were included in our preliminary experience. During defibrillation threshold evaluation, two patients required 34 J with the single transvenous lead system, and five patients were not defibrillated with the single lead system; therefore, they required a 300‐J external rescue shock. We decided to implant an additional patch in those seven patients with high defibrillation thresholds. This patch was inserted into the pleural cavity through a left subcostal incision. Under video thoracoscopy, it was positioned and stitched onto the pericardium. The defibrillation generator was then implanted through the left subcostal incision in a subdiaphragmatic space. As a result, pre‐operative defibrillation thresholds were significantly reduced (14.29 ± 3.45 J, mean ± SD) and remained stable during follow‐up controls (eighth day and second month). Long‐term follow‐up (14 ± 4.5 months) was uneventful, with an excellent tolerance for the patients. In conclusion, extrapericardial implantation of defibrillation patches under video thoracoscopy is an easy technique that allows low defibrillation thresholds.