bluuebunny/crossref_metadata_2025 huggingface dataset:
Intramyocardial Electrogram Variability in the Monitoring of Graft Rejection After Heart Transplantation
Authors: GRASSER BARBARA , IBERER FLORIAN , SCHREIER GÜNTER , SCHAFFELLNER SILVIA , KASTNER PETER , PRENNER GÜNTHER , HIPMAIR GÜNTHER , WASLER ANDRE , PETUTSCHNIGG BERTHOLD , MÜLLER HELMUT , HUTTEN HELMUT , SCHALDACH MAX , TSCHELIESSNIGG KARLHEINZ
Published: July 2006

The ventricular evoked response is a well‐standardized electrophysiological signal that can be used for noninvasive, long‐term cardiac transplant monitoring. Rejection‐sensitive and infection‐specific parameters extracted from intramyocardial electrograms correlate with clinical results. The influences of pacing rate, transition from intrinsic to paced rhythm and positional changes on the diagnostic parameters were studied. Increasing the pacing rate shortened the ventricular evoked response and directly influenced the infection specific parameter. The rejection‐sensitive parameter remained stable at pacing rates between 100 and 120 beats/min. Measurements made immediately after the patient assumed a supine position and after switching to paced rhythm showed a decrease in the rejection‐sensitive parameter. A change in position from supine to upright did not influence the rejection‐sensitive parameter, but higher values were measured after returning to the supine position. In conclusion, noninvasive recordings of the ventricular evoked response for monitoring of cardiac allograft should be done at the same time of day, at the same pacing rate, and with the patient resting for at least 5 minutes before measurements are made.
T Wave Complexity in Patients with Hypertrophic Cardiomyopathy
Authors: YI GANG , PRASAD KRISHNA , ELLIOTT PERRY , SHARMA SANJAY , GUO XIAOHUA , MCKENNA WILLIAM J. , MALIK MAREK
Published: July 2006

The complexity of the T wave assessed by principal component analysis (PCA) has been proposed to reflect obnormal repolarization, which may be arrhythmogenic. To determine whether PCA can differentiate patients with hypertrophic cardiomyopathy (HCM) from normal subfects and whether PCA is of prognostic importance in HCM, 112 patients with HCM (41 ±14 years, 64 males) and 72 healthy subjects (39 ± 9 years, 41 males) were studied. Patients with sinus node dysfunction, AV conduction block, flat T waves, QRS > 140 ms, and those < 15 years were excluded from this study. Standard 12‐lead ECGs were recorded digitally using the MAC‐VU system (Marquette Medical Systems). PCA parameters were computed using the QT Guard software package by Marquette. PCA ratio was significantly greater in HCM patients than in normal controls (23.9%± 12.4% vs 16.1%± 7.6%, P < 0.0001) and was correlated with QT‐end dispersion (r = 0.24. P = 0.01) and QT peak (Q point to T peak) dispersion (r = 0.35, P < 0.0001). HCM patients with syncope (n = 23) had increased PCA ratios compared with those without syncope (29.1%± 11.5% vs 22.5%± 12.3%, P = 0.01). PCA ratio was similar in patients with and without nonsustained ventricular tachycardia on Holter (25.9%± 11.4% vs 22.7%± 12.1%, P = 0.2), as well as in patients treated with amiodarone or sotalol versus those not on therapy. In conclusion, assessment of the complexity of the T wave by PCA differentiates HCM patients from normal subjects. PCA ratio correlated with QT dispersion and an increased PCA ratio was associated with a history of syncope in HCM.
Correlation of Heart Rate Variability Parameters and QT Interval in Patients After PTCA of Infarct Related Coronary Artery as an Indicator of Improved Autonomic Regulation
Authors: SZYDLO KRZYSZTOF , TRUSZ‐GLUZA MARIA , DRZEWIECKI JANUSZ , WOZNIAK‐SKOWERSKA IWONA , SZCZOGIEL JAN
Published: July 2006

The purpose of this study was to determine if PTCA of the infarct related coronary artery (IRA) in the late phase of myocardial infarction (MI) can improve autonomic regulation of sinus rhythm and electrical stability of the myocardium measured by heart rate variability (HRV), QT, QTc, and its dispersion (QTd) and if any correlation exists among these measures. The study was performed in 25 patients (21 male, age: 50 ± 9 years, EF: 52%± 11%) in the late phase of MI (2.5 ± 1.5 months). HRV parameters were calculated automatically. QT, QTc, and QTd were measured manually from a 12‐lead surface ECG (50 mm/s). All measurements were made before and 3–5 days after PTCA. Day and night parameters of HRV were sampled over two periods: 2 pm to 10 pm (day) and 10 pm to 6 am (night). Parameters of HRV measured from whole recordings were significantly higher after successful PTCA: SDRR (116 31 vs 128 ± 38 ms), SD (55 ± 17 vs 62 ± 22 ms), rMSSD (30 ± 13 vs 36 ± 14 ms) and HF (246 ± 103 vs 417 ± 224 ms2). Significant differences were found during daytime for SD, rMSSD, and HF, and during nighttime for SDRR, SDANN. QT interval duration, QT corrected to the heart rate, and QT dispersion were significantly lower after PTCA (QTd: 54 ± 15 vs 39 ± 12 ms). There was no correlation between HRV and QT values before PTCA. High correlations were found after the procedure, particularly between QTd and nighttime HRV. Conclusions: PTCA of IRA in the late phase of MI enhances sympathovagal regulation of the cardiac rhythm and the electrical stability of the heart, which may be prognostically important.
Baroreflex Sensitivity and Heart Rate Variability in Coronary Disease Compared to Dilated Cardiomyopathy
Authors: MENZ VOLKER , GRIMM WOLFRAM , HOFFMANN JÜIRGEN , BORN STEPHAN , SCHMIDT CHRISTINA , MAISCH BERNHARD
Published: July 2006

This study was designed to compare baroreceptor sensitivity and heart rate variability as measures of cardiac autonomic tone in patients with coronary disease (CAD, n = 49) and idiopathic dilated Cardiomyopathy (IDC, n = 130). Time domain heart rate variability, including SDNN, SDANN, and pNN50, was determined during 24‐hour Holter ECG. Baroreflex sensitivity was analyzed nonivasively using the phenylephrine method. Baroreflex sensitivity and heart rate variability were comparable between patients with CAD versus IDC (baroreflex sensitivity: 6.1 ± 3 vs 6.9 ± 5 ms/mmHg; SDNN: 97 ± 40 vs 114 ± 41 ms; SDANN: 83 ± 33 vs 99 ± 41 ms; pNNSO: 3.9 ± 4 vs 9.6 ± 13 ms, P = NS for all comparisons). Likewise, a subgroup analysis of patients with a left ventricular ejection fraction (LVEF) ≤ 30% showed no significant difference in baroreceptor sensitivity and heart rate variability between IDC and CAD patients. Patients with CAD and an LVEF > 30% had a decreased heart rate variability but not a decreased baroreflex sensitivity compared to patients with IDC and LVEF > 30 % (baroreflex sensitivity: 6.4 ± 4 vs 8.3 ± 6 ms/mmHg, P = NS; SDNN: 98 ± 19 vs 128 ± 42 ms, P < 0.05; SDANN: 86 ± 21 vs 112 ± 43 ms, P < 0.05; pNN50: 4.2 ± 3 vs 12.3 ± 8 ms, P < 0.05). Patients with a markedly depressed LVEF show comparable alterations in cardiac autonomic tone whether they have CAD or IDC. Patients with CAD and preserved LV function, however, have a decreased heart rate variability compared to patients with IDC and preserved LV function. The prognostic significance of these findings will be determined prospectively in a large patient cohort at our institution.
Catheter Ablation of Ventricular Tachycardia in Patients with Right Ventricular Dysplasia: Identification of Target Sites by Entrainment Mapping Techniques
Authors: HARADA TOMOO , AONUMA KAZUTAKA , YAMAUCHI YASUTERU , IGAWA MASAYUKI , HACHIYA HITOSHI , OH JUNG‐CHA , TOMITA YASUSHI , SUZUKI FUMIO , NAKAGAWA TAKEMASA
Published: July 2006

Objective: To identify target sites for radiofrequency ablation of ventricular tachycardia (VT) by entrainment mapping techniques in patients with arrhythmogenic right ventricular dysplasia. Methods: Entrainment mapping and radiofrequency ablation of eight VTs was performed in seven patients. Radiofrequency ablation was applied at 31 reentry circuits sites that were classified based on findings during entrainment. Results: By entrainment criteria the 31 sites were classified as: exit sites (n = 12), proximal sites (n = 6), and outer loop sites (n = 13). Radiofrequency current application terminated VT at 7 of 31 sites: 2 of 12 exit sites (17%), 4 of 6 proximal sites (67%), and 1 of 13 outer loop sites (8%). Conclusion: Radiofrequency ablation terminated VTs most often at sites proximal to the exit as opposed to outer loop sites and exit sites (P = 0.05). The critical isthmus for ablation of VT in right ventricular dysplasia often may be distant to the exit.
Noninvasive Arrhythmia Risk Stratification in Idiopathic Dilated Cardiomyopathy: Design and First Results of the Marburg Cardiomyopathy Study
Authors: GRIMM WOLFRAM , GLAVERIS CHRISTINA , HOFFMANN JÜRGEN , MENZ VOLKER , MET NADJA , BORN STEPHAN , MAISCH BERNHARD
Published: July 2006

The Marburg Cardiomyopathy Study (MACAS) is a prospective, observational study designed to determine the value of the following potential noninvasive arrhythmia risk predictors in at least 200 patients with idiopathic dilated Cardiomyopathy (IDC) over a 5‐year follow‐up period: NYHA‐class, left ventricular ejection fraction (LVEF), left ventricular end‐diastolic diameter, left bundle branch block and atrial fibrillation on ECG, QT/JT dispersion on 12‐lead ECG, signal‐averaged ECG, ventricular arrhythmias and heart rate variability (HRV) on 24‐hour Hotter ECG, baroreflex sensitivity, and microvolt T wave alternans during exercise. This article describes the findings among the first 159 patients with IDCs enrolled in MACAS until May 1998 (40 women, 119 men;age:49 ± 12 years; LVEF: 32 ± 10%). Twenty‐nine patients (18%) had atrial fibrillation and 130 patients (82%) were in sinus rhythm. Patients with sinus rhythm were further stratified according to LVEF < 30% (n = 54) versus LVEF ≥ 50% (n = 76). Compared to patients with LVEF ≥ 30%, patients with LVEF < 30% more often had left bundle branch block (43% vs 25%, P < 0.05), nonsustained VT (44% vs 22%, P < 0.05), decreased HRV (SDNN: 95 ± 39 vs 128 ± 42 ms, P < 0.01), decreased baroreflex sensitivity (5.6 ± 4 vs 8.3 ± 6 ms/mmHg, P < 0.01), and T wave alternans (59% vs 37%, P < 0.05). The prognostic significance of these findings will be determined by multivariate Cox analysis at the end of a 5‐year follow‐up. Primary endpoints in MACAS are overall mortality and arrhythmic events (i.e., sustained VT or VF, or sudden cardiac death).
Spinal Cord Stimulation for the Treatment of Refractory Angina Pectoris: A Two‐Year Follow‐Up
Authors: GRECO SALVATORE , AURITI ANTONIO , FIUME DARIO , GAZZERI GIOVANNI , GENTILUCCI GIUSEPPE , ANTONINI LANFRANCO , SANTINI MASSIMO
Published: July 2006

Twenty‐three patients affected by severe, refractory angina were submitted to permanent spinal cord stimulation (SCS) and then followed in our outpatient clinic for 24 months. During the follow‐up period, the number of weekly angina episodes drastically dropped from 9.2 (preimplant) to 1.8 in the 3rd, 2.5 in the 6th, 4.5 in the 12th, and 4.2 in the 24th month, with a statistically significant difference (P < 0.01) between the first and last values. A significant increase in the average exercise time from 320 ± 120 seconds (in baseline condition) to 410 ± 115 seconds (during SCS) was observed at the treadmill stress test (P < 0.01). SCS was well tolerated by all the patients. However, 7 patients died during follow‐up (3 myocardial infarctions, 2 noncardiac deaths, and 2 sudden deaths). Three generators were replaced because of battery depletion after 15, 17, and 21 months. No serious complication was observed. In conclusion, in patients with otherwise intractable angina or already submitted to myocardial revascularization, SCS is very effective in reducing the number of angina episodes. The time of the work during exercise stress test is also significantly prolonged.
Steroid Eluting High Impedance Pacing Leads Decrease Short and Long‐Term Current Drain: Results from a Multicenter Clinical Trial.
Authors: ELLENBOGEN KENNETH A. , WOOD MARK A. , GILLIGAN DAVID M. , ZMIJEWSKI MATT , MANS DAN ,   THE CAPSURE Z INVESTIGATORS
Published: July 2006

Pacemaker lead technology has changed considerably over the past decades. The widespread use of low polarization highly porous electrodes and steroid elution electrodes has resulted in low chronic pacing thresholds, as well as a decrease in the incidence of exit block. Efforts to develop pacing leads with high impedance might theoretically lead to lower lead current drain, which is a component of battery capacity. Pulse generator longevity can be increased without sacrificing pacemaker capabilities if pacing current drain can be decreased. Decreasing the size of the stimulation electrode results in increased pacing impedance, and if pacing thresholds are unchanged, a decreased current drain is predicted by Ohm's law (I = V/R). There is limited data available on the pacing characteristics of large numbers of patients with high impedance leads, despite their recent general availability and increasing widespread use. This multicenter, controlled trial examined the differences in performance between standard steroid‐eluting pacing leads in the atrium (Medtronic model 5524) and ventricle (Medtronic model 5024), and new high impedance steroid‐eluting pacing leads in the atrium (Medtronic model 5534) and ventricle (Medtronic model 5034). Measurements of bipolar pacing thresholds at 2.5 V, pacing impedance, and sensing thresholds were determined within 24 hours of pacemaker implantation, and at 0.5, 1, 3, 6 and 12 months after pacemaker implantation in 609 patients. Pacing and sensing thresholds were similar for the control and high impedance leads at all times except for a slightly larger R wave with the high impedance leads at implantation and 12 months. The mean impedance of the high impedance pacing leads in the atrium and ventricle at 12 months was 992 ± 175 and 1,080 ± 220 Ω, compared to 522 ± 69 and 600 ± 89 Ω for the standard pacing leads in the atrium and ventricle (P ≤ 0.001 for the high impedance leads compared to standard leads in each chamber). The mean atrial lead current (measured at 2.5 V) at 12 months was 2.6 ± 0.5 mA with the high impedance lead, and 4.9 ± 0.7 mA with the standard lead in the atrium (P ≤ 0.001). In the ventricle, the mean lead current at 12 months was 2.4 ± 0.4 mA with the high impedance pacing lead and 4.3 ± 0.6 mA with the standard lead (P ≤ 0.001). High impedance leads are associated with lower lead current drain than standard pacing leads in the atrium and ventricle for up to 1 year. No clinically important differences in sensing characteristics was noted with the high impedance leads in the atrium or ventricle compared to standard pacing leads. High impedance leads may result in increased pulse generator longevity.
The Dynamic Behavior of the Diastolic Slope of Monophasic Action Potential Can be Related to the Occurrence and Maintenance of Delayed Afterdepolarization Dependent Arrhythmias
Authors: DE GROOT S.H. MARIEKE , VOS MARC A. , GORGELS ANTON P.M. , LEUNISSEN JET D.M. , HERMANS MARC , DOHMEN LEON R.B. , WELLENS HEIN J.J.
Published: July 2006

We have described the value of the diastolic slope of the MAP recording at the end of a pacing train as a qualifying marker for the induction of delayed afterdepolarization (DAD) dependent arrhythmias. In the present study (1) the behavior of the slope at different time points during a pacing train was quantified and related to the arrhythmogenic outcome (group A) and (2) termination of DAD dependent VT was related to changes in the slope steepness (group B). In dogs with chronic complete AV block, a MAP was recorded during (1) ventricular pacing, before and after ouabain administration (group A) and (2) 6 spontaneous and 6 lidocaine induced VT terminations (group B). During control (group A), the slope at the end of pacing train was 5 ± 3 mV/s (mean ± SD), independent of the pacing duration. During ouabain, this increased to 20 ± 15 mV/s (P < 0.05), varying with the duration of pacing. The slope was steeper after pacing for 4 seconds, compared to 20 seconds (26 ± 12 mV/s vs 16 ± 13 mV/s, P < 0.05) which corresponded with more frequent VT induction. In spontaneously terminating VTs (group B), CL increased from 353 ± 54 ms at the start to 434 ± 78 ms (P < 0.05) before VT termination. This corresponded with a decreasing steepness of the slope from 19 ± 10 mV/s to 6 ± 5 mV/s (P < 0.05). In lidocaine induced VT termination, the CL and the steepness of the slope showed an identical behavior. There is a dynamic variation in the steepness of the diastolic slope during pacing, which depends on the duration of pacing and predicts arrhythmogenic outcome. Furthermore, a decrease in steepness of the slope during DAD dependent VT can be used to predict VT termination.
Automatic Capture Verification by Charge‐Neutral Sensing
Authors: KADHIRESAN VEERICHETTY A. , OLIVE ART , MGORNICK CHARLES , SPINELLI JULIO , VILLALTA DON
Published: July 2006

Automatic capture verification can prolong pulse generator longevity and increase patient safety. However, the detection of evoked response following pacing is complicated due to afterpotentials caused by polarization of electrodes. This study describes a new capture verification scheme, which neutralizes the charges between the pacing electrodes. The hypothesis of the charge‐neutral sensing is that the afterpotentials in the ring and the tip are opposite in polarity when pacing in a bipolar mode between ring and tip. Summing the unipolar signals sensed at the tip and the ring should effectively cancel the afterpotentials. This scheme was implemented in an external computer based system and tested during pacemaker implant/replacement on 23 patients during VVI pacing (17 acutely implanted leads and 6 chronic leads). Surface ECG was recorded to provide a marker for capture and noncapture. The pacing voltage was gradually decreased until a noncapture beat was noted. To avoid fusion beats, the pacing rate was programmed ˜50% higher than the intrinsic rate. The evoked response was high pass filtered and the integral average was calculated for both capture and noncapture beats. The system signal to noise ratio (SNR) was expressed as ratio of the minimum integral average of all capture beats to the maximum integral average of all noncapture beats. The system SNR was 8.6 ± 1.3 (mean ± S.E.M; range 1.5–22.8), indicating that the charge‐neutral sensing method has, on average, a ninefold safety margin in providing capture verification. Further, evaluation is needed to fully assess this feature in patients with chronic leads.
Controlled Ventilation Enhances Catheter Stability During Radiofrequency Ablation
Authors: VAZIR‐MARINO FRANAH , YOUNG MING‐LON , KOHLI VIKAS , BARRON MICHAEL , WOLFF GRACE S.
Published: July 2006

Variations in the amplitude of the atrial and ventricular depolarization waves of the intracardiac electrogram occur during different phases of respiration. Therefore, we tested whether controlled ventilation would reduce ablation attempts and increase the rate of success in patients undergoing radiofrequency ablation with general anesthesia. Thirty‐eight children were divided into two groups: (1) controlled and (2) noncontrolled or cyclic ventilation. In the controlled ventilation group, the mapping electrogram was recorded during sustained inspiration, sustained expiration, and cyclic ventilation. Ablation was done in the phase of ventilation that had the least variability in atrial and ventricular amplitudes. Seventeen patients in the controlled ventilation group had tracings adequate for review. In eight patients, ablation was done during sustained inspiration with the percentage change of atrial and ventricular amplitudes (15%± 16% and 13%± 16%, respectively) being < that during sustained expiration (38%± 27%, P = 0.04 and 20%± 21 %) or during cyclic ventilation (57%± 27%, P < 0.01 and 54%± 26%, P = 0.003). In nine patients, ablation was done during sustained expiration with the percentage change of atrial and ventricular amplitudes (5%± 5% and 5%± 2%) being less than that during sustained inspiration (21%± 14%, P = 0.01 and 11%± 6%, P = 0.01) or during cyclic ventilation (68%± 23%, P < 0.001 and 48 ± 26%, P = 0.001). We achieved success with each patient in both groups, but the number of ablation attempts were less in the controlled ventilation group 1 (3 ± 2), as compared to the cyclic ventilation group 2 (8 ± 8; P < 0.02). We concluded that controlled ventilation reduced the number of ablation attempts and facilitated the ablation procedure.
Management of Pacing System Related Complications in Patients Undergoing Dynamic Cardiomyoplasty
Authors: LORUSSO ROBERTO , STRUBLE CHESTER , BIANCHETTI FEDERICO , MARCHINI ANNA , CURNIS ANTONIO , ALFIERI OTTAVIO
Published: July 2006

Integrity of the electrical circuit is a necessary requirement for appropriate heart/wrapped skeletal muscle interaction to be achieved in cardiomyoplasty. This article describes the management of two different complications after a cardiomyoplasty procedure involving the electrical system (infection of the abdominal cardiomyostimulator pocket and intramuscular lead fracture). Minimal approaches were carried out, which ensured the successful treatment of the infective and of the mechanical insult, and represent useful strategy for solving such uncommon problems.
Irregular Ventricular Stimulation in the DDI Mode of a Dual Chamber Pacemaker With Atrial‐Based Lower Rate Timing
Authors: BAROLD S. SERGE , DOUARD HERVÉ , BROUSTET JEAN PAUL , CLEMENTY JACQUES
Published: July 2006

This report describes two patients with atrial fibrillation in whom an implanted CHORUS DDD pacemaker programmed to the DDI mode produced an irregular ventricular stimulation rate. The lower rate timing of these devices is atrial‐based only when an atrial event opens an AV interval shorter than the programmed AV delay. In the DDI mode, if Api represents the time when an atrial paced event (Ap) would have occurred if it had not been inhibited by a previous atrial sensed event (As), then Api‐Vp constitutes the implied AV interval where Vp is a paced ventricular event. Although the As‐Vp interval (As‐Api+Api‐Vp) generates an atrial refractory period during its entire duration, the pacemaker can sense an atrial event (Ar) during the implied AV interval. Ar cannot start another AV delay, but it can initiate the atrial‐based lower rate interval. This timing mechanism can cause irregular prolongation of Vp‐Vp intervals to a value longer than the programmed lower interval with a maximal extension equal to the programmed AV delay. Such behavior of the CHORUS pacemaker should not be interpreted as malfunction.
Successful Radiofrequency Ablation of an Accessory Pathway During Pregnancy
Authors: DOMÍNGUEZ ALBERTO , ITURRALDE PEDRO , HERMOSILLO ANTONIO G. , COLIN LUIS , KERSHENOVICH SERGIO , GARRIDO LUIS M.
Published: July 2006

The preexcitation syndrome is a rare entity during pregnancy. We present a 20‐week pregnant patient with Wolff‐Parkinson‐White syndrome and recurrent episodes of tachycardia with hemodynamic compromise refractory to medical treatment that required electrical cardioversion several times. Due to the poor evolution we performed a successful radiofrequency ablation of a right posteroseptal accessory pathway using 70 seconds of total fluoroscopy time without complications. We consider this is an alternative and safer treatment in those cases in which the tachyarrhythmias compromise the hemodynamic state during pregnancy.
Defibrillation Efficacy of Different Electrode Placements in a Human Thorax Model
Authors: DE JONGH AMY L. , ENTCHEVA EMILIA G. , REPLOGLE JANICE A. , BOOKER ROBERT S. , KENKNIGHT BRUCE H. , CLAYDON FRANK J.
Published: July 2006

The objective of this study was to measure the defibrillation threshold (DFT) associated with different electrode placements using a three‐dimensional anatomically realistic finite element model of the human thorax. Coil electrodes (Endotak DSP, model 125, Guidant/CPI) were placed in the RV apex along the lateral wall (RV), withdrawn 10 mm away from the RV apex along the lateral wall (RVprox), in the RV apex along the anterior septum (RVseptal), and in the SVC. An active pulse generator (can) was placed in the subcutaneous prepectoral space. Five electrode configurations were studied: RV → SVC, RVprox→ SVC, RVSEPTAL→SVC, RV →Can, and RV →SVC+Can. DFTs are defined as the energy required to produce a potential gradient of at least 5 V/cm in 95% of the ventricular myocardium. DFTs for RV → SVC, RVPROX→ SVC, RVseptal→ SVC, RV → Can, and RV → SVC + Can were 10, 16, 7, 9, and 6 J, respectively. The DFTs measured at each configuration fell within one standard deviation of the mean DFTs reported in clinical studies using the Endotak leads. The relative changes in DFT among electrode configurations also compared favorably. This computer model allows measurements of DFT or other defibrillation parameters with several different electrode configurations saving time and cost of clinical studies.
Impact of Transvenous Lead Position on Active‐Can ICD Defibrillation: A Computer Simulation Study
Authors: AGUEL FELIPE , EASON JAMES C. , TRAYANOVA NATALIA A. , IEKAS GREG , FISHLER MATTHEW G.
Published: July 2006

Optimizing lead placement in transvenous defibrillation remains central to the clinical aspects of the defibrillation procedure. Studies involving superior vena cava (SVC) return electrodes have found that left ventricular (LV) leads or septal positioning of the right ventricular (RV) lead minimizes the voltage defibrillation threshold (VDFT) in endocardial lead→SVC defibrillation systems. However, similar studies have not been conducted for active‐can configurations. The goal of this study was to determine the optimal lead position to minimize the VDFT for systems incorporating an active can. This study used a high resolution finite element model of a human torso that includes the fiber architecture of the ventricular myocardium to find the role of lead positioning in a transvenous LEAD→can defibrillation electrode system. It was found that, among single lead systems, posterior positioning of leads in the right ventricle lowers VDFTs appreciably. Furthermore, a septal location of leads resulted in lower VDFTs than free‐wall positioning. Increasing the number of leads, and thus the effective lead surface area in the right ventricle also resulted in lower VDFTs. However, the lead configuration that resulted in the lowest VDFTs is a combination of a mid‐cavity right ventricle lead and a mid‐cavity left ventricle lead. The addition of a left ventricular lead resulted in a reduction in the size of the low gradient regions and a change of its location from the left ventricular free wall to the septal wall.
The Effect of Shock Configuration and Delivered Energy on Defibrillation Impedance
Authors: OLSOVSKY MARY R. , SHOROFSKY STEPHEN R. , GOLD MICHAEL R.
Published: July 2006

Shock impedance is an important determinant of defibrillation efficacy. Lead configuration, shock polarity, and delivered energy can affect shock impedance, but these variables have not been studied in active can lead systems. The present study was a prospective evaluation of 25 patients undergoing initial transvenous defibrillator implantation. In all patients, a dual coil lead and pectoral emulator were placed and three lead configurations were tested in random order: Lead (distal to proximal coil), unipolar (distal coil to can), and triad (distal coil to can + proximal coil). Shock energies of 0.1‐ to 15‐J shock were evaluated. Impedance increased a mean of 21% as delivered energy was decreased (P < 0.001), an effect independent of lead configuration. At all delivered energies, impedances in the unipolar configuration were about 40% higher than triad, while the lead configuration was about 20% higher than triad (ps < 0.001). Polarity did not affect impedance. These results indicate that transvenous lead configurations and delivered energy, but not polarity, significantly influence shock impedance. The magnitude of the increase of impedance at low energies is independent of the shocking pathway. This effect has important implications for low energy shocks used to terminate atrial fibrillation or ventricular tachycardia.
Clinical Significance of Consecutive Shocks in Patients with Left Ventricular Dysfunction Treated with Implantable Cardioverter Defibrillators
Authors: ENDOH YASUHIRO , OHNISHI SATOSHI , KASANUKI HIROSHI
Published: July 2006

The purpose of the present study was to determine the clinical significance of consecutive automatic shocks delivered by implantable cardioverter defibrillators (ICDs). Sixty‐four patients who received ICDs at our institution between January 1990 and July 1997 were included in this study. There were 53 men and 11 women with a mean age of 50 ± 14 years. During a follow‐up period ranging between 0.2 and 73 months (mean 23 ± 21 months), 17 patients received consecutive shocks (group A), 29 patients received single shocks (group B), and 18 patients received no ICD therapy (group C). Clinical characteristics, episodes of ICD therapy, and prognosis were compared among the three groups. There were no significant differences among the three groups with regard to clinical characteristics, time to first ICD therapy, number of antitachycardia pacing episodes, or frequency of inappropriate discharges. The mortality rate was higher in group A than in groups B and C (P = 0.0021). The sensitivity of consecutive shocks in predicting death was 70%, the specificity was 88%, and the predictive accuracy was 81% in patients with left ventricular ejection fractions < 35%. In summary, consecutive shocks are a clinically important event in patients with ICDs. Specifically, patients who receive consecutive shocks and have a depressed left ventricular function should be considered particularly high risk.
Complications of Third‐Generation Implantable Cardioverter Defibrillator Therapy
Authors: GRIMM WOLFRAM , MENZ VOLKER , HOFFMANN JÜRGEN , TIMMANN UWE , FUNCK REINHARD , MOOSDORF RAINER , MAISCH BERNHARD
Published: July 2006

To determine the incidence of complications of third‐generation implantable cardioverter defibrillator (ICD) therapy, 144 patients were prospectively studied who underwent first implant of third‐generation devices (i.e., ICD systems with biphasic shocks, ECC storage capability, and nonthoracotomy lead systems). During 21 ± 15 months of follow‐up, 41 (28%) patients had one or more complications. No patient died perioperatively (30 days) and no ICD infection was observed during follow‐up. Complications included bleeding or pocket hematoma (hemoglobin drop > 2 g/dL) in 5 (3%) patients, prolonged reversible ischemic neurological deficit in 1 (1%) patient, postoperative deep venous thrombosis of leg in 1 (1%) patient, pneumothorax in 2 (1%) patients, difficulty to defibrillate ventricular fibrillation intraoperatively in 2 (1%) patients, generator malfunction in 1 (1%) patient, arthritis of the shoulder in 3 (2%) patients, and allergic reaction to prophylactic antibiotics in 2 (1%) patients. A total of seven lead related complications were observed in six (4%) patients including endocardial lead migration in four (3%) patients. Twenty‐three (16%) patients received inappropriate shocks for supraventricular tachyarrhythmias (n = 13), non‐sustained ventricular tachycardia (VT) (n = 7), or myopotential oversensing (n = 3). We conclude that serious complications such as perioperative death or ICD infection are rare in patients with third‐generation ICDs. Lead‐related problems and inappropriate shocks during follow‐up are the most frequent complications of third‐generation ICD therapy. Recognition of these complications should promote advances in ICD technology and management strategies to avoid their recurrence.
Patient Discomfort Following Pectoral Defibrillator Implantation Using Conscious Sedation
Authors: BOLLMANN ANDREAS , MARX ALEXANDRA , SATHAVORN CHARN , MERA FERNANDO , DELURGIO DAVID , WALTER PAUL F. , LANGBERG JONATHAN J.
Published: July 2006

Background: The miniaturization of implantable cardioverter defibrillators (ICDs) has made pectoral implantation possible. However, postoperative pain following the procedure has not been systematically studied. The aim of the current study was to prospectively assess patient discomfort and identify factors influencing pain perception during follow‐up. Methods: Pain related to device implantation was quantified in 21 consecutive patients (age, 61 ± 11 years; 17 men and 21 women; 16 of 21 had coronary artery disease; left ventricular ejection fraction, 32%± 15%) undergoing pectoral ICD implantation with conscious sedation (fentanyl 118 ± 72 μg, midazolam 14 ± 9 mg). Patients completed the Visual Analogue Scale (VAS, 0–100) and the McGill Pain Questionnaire 24 hours and 1 month postoperatively. Regression analysis was used to define clinical and procedure related variables affecting patient discomfort and frequency of postoperative analgesic use. Results: The mean VAS score was 34 ± 20 24 hours postoperatively. A single (4.8%) patient described postoperative pain as severe. Pain was reported to be moderate by 10 (47.6%) patients and mild by 10 (47.6%) patients. Intraoperative fentanyl requirement was a predictor of postoperative pain (R = 0.51, P = 0.036), and procedural duration was a strong predictor of postoperative analgesic use (R = 0.75, P < 0.001). Pain at 1 month decreased to a VAS score of 19 ± 18 (P = 0.002 vs 24 hours) and was rated to be severe, moderate, and mild by 1, 3, and 17 patients, respectively. Late pain was related to a VAS score at 24 hours (R = 0.67, P = 0.004). Conclusions: (1) Pectoral ICD implantation using conscious sedation is well tolerated. (2) Postoperative discomfort correlates with longer procedural times and larger intraoperative narcotic requirements.
Clinical Significance of Sleep‐Related Breathing Disorders in Patients with Implantable Cardioverter Defibrillators
Authors: FRIES ROLAND , BAUER DIRK , HEISEL ARMIN , JUHASZ JANOS , FICHTER JOACHIM , SCHIEFFER HERMANN , SYBRECHT GERHARD W.
Published: July 2006

The prevalence and clinical significance of sleep‐related breathing disorders (SRBDs) in patients with cardiac disease and a history of life‐threatening ventricular tachyarrhythmias is unclear. Forty consecutive recipients of implantable cardioverter defibrillators (ICDs) with cardiac disease and a documented history of spontaneous, life‐threatening, ventricular tachyarrhythmias underwent full night polysomnography. SRBDs were diagnosed if the apnea/hypopnea index was > 10. SRBD were diagnosed in 16 of 40 patients (40%): central sleep apnea (CSA) was present in 9 of these 16 patients (56%), 8 of whom had associated Cheyne‐Stoke respiration. Seven of the 16 patients with SRBD (44%) had obstructive sleep apnea (OSA). Patients with and without SRBDs were comparable with respect to left ventricular ejection fraction, NYHA classification, underlying heart disease, ICD indications, and concomitant antiarrhythmic drug and beta‐blocker therapy. Patients were followed prospectively for 2 years. ICD‐treated ventricular tachyarrhythmias occurred in 10 of 24 patients (42%) without SRBD, in 4 of 9 patients (44%) with CSA, and in 3 of 7 patients (44%) with OSA (NS). The numbers and circadian distributions of episodes recorded during follow‐up in patients without SRBD versus with CSA or OSA were not significantly different (14 ± 25, median = 4 vs 4 ± 5, median = 2.5 vs 15 ± 15, median = 7, respectively). The 2‐year mortality, which was entirely attributable to nonsudden cardiac events, was highest in patients with CSA (4/9 [44%], vs 0/7 [0%] with OSA, vs 3/24 patients (12.5%) without SRBD; P < 0.05).
Effect of Increased Parasympathetic and Sympathetic Tone on Internal Atrial Defibrillation Thresholds in Humans
Authors: BAROLD HELEN S. , SHANDER GREGG , TOMASSONI GERY , SIMONS GRANT R. , WHARTON J. MARCUS
Published: July 2006

Although changes in autonomic tone affect ventricular defibrillation, little is known about the effect of increased parasympathetic or sympathetic tone on the atrial defbrillation threshold. Methods: To evaluate the effect of reflexly increased parasympathetic and increase α‐ and β‐adrenergic tone on the atrial defibrillation threshold (ADFT), atrial fibrillation was induced in 14 patients. ADFTs, right atrial refractory period (RARP), and monophasic action potential duration (MAPD) were determined before and after autonomic intervention. ADFTs were determined with a step‐up protocol using 3/3‐ms biphasic shocks delivered through decapolar catheters in the right atrial appendage and coronary sinus. Two groups were studied. Group I (N = 8) had ADFTs determined at baseline, after receiving phenylephrine (PE), and with PE plus atropine (A). Group 2 (N = 6) had ADFTs determined at baseline and after receiving isoproterenol (ISO). Results: Group I: PE significantly increased sinus cycle length (SR‐CL) compared to baseline (742 ± 123 to 922 ± 233 ms) without significantly changing RARP, MAPD, or ADFT (2.3 ± 1.3 J vs 2.3 ± 0.8 J). With PE + A, SR‐CL significantly decreased (529 ± 100 ms vs 742 ± 123 ms) and MAPD shortened (231 ± 41 ms vs 279 ± 49 ms) without altering RARP or ADFT (1.94 ± 0.9 J vs 2.25 ± 1.25 J). Group 2: ISO decreased SR‐CL (486 ± 77 ms vs 755 ± 184 ms) and MAPD (169 ± 37 ms vs 226 + 58 ms) but not RARP or ADFT (2.25 ± 1.21 J vs 2.33 ± 1.75 J). Conclusions: Increasing parasympathetic, α‐, or β‐adrenergic tone does not affect the ADFT despite causing significant electrophysiological changes in the atria.
Detection of Atrial Fibrillation During Sinus Tachycardia Induced by Exercise in Patients with Implantable Atrial Defibrillators
Authors: TSE HUNG‐FAT , LAU CHU‐PAK , AYERS GREGORY M.
Published: July 2006

Accurate detection of atrial fibrillation (AF) is essential for appropriate operation of an implantable atrial defibrillator (IAD). However, during episodes of sinus tachycardia, distinction between AF and sinus rhythm (SR) using the “quiet interval” and “baseline crossing” analysis in the detection algorithm of the IAD may be difficult. The efficacy of this AF detection algorithm was tested in five patients implanted with an IAD (MFTRIX, Model 3000 or 3020, InControl Inc.) during treadmill exercise testing. The IADs were programmed to Monitor Mode with a wake up cycle of 1 minute for AF detection using the device nominal parameters or modified parameters, and to mark rhythms appropriate for shock delivery. A mean peak heart rate of 137 ± 26 beats/min was reached during maximum exercise, and one patient developed transient AF. Seventy‐eight (75 in SR, 3 in AF) and 91 (89 in SR, 2 in AF) runs of AF detection were performed using the nominal and modified parameters, respectively. The IAD detected AF and SR accurately, except for one episode of false‐positive AF detection during sinus tachycardia at the nominal settings, but inappropriate shocks were prevented by minimum RR interval criteria that limited discharge at high heart rate. These results indicate that the AF detection algorithm in the IAD may become more vulnerable to false‐positive AF detection during sinus tachycardia, which were avoided by reprogramming the Quiet Interval and minimum RR interval criteria for AF detection. Exercise testing appeared useful to program optimal settings of the IAD in preparation for daily activities.
Inhibition of Ventricular Stimulation in Patients with Dual Chamber Pacemakers and Prolonged AV Conduction
Authors: BODE FRANK , WIEGAND UWE , KATUS HUGO A. , POTRATZ JUERGEN
Published: July 2006

Episodes of repetitive P wave undersensing have been described in dual chamber pacemakers due to automatic extension of the postventricular atrial refractory period (PVARP). Pacemaker stimulation was completely inhibited despite the presence of adequate P waves. This study sought to determine whether cycles of repetitive P wave undersensing occur even in the absence of PVARP extension. Two‐hundred fifty‐five patients were investigated after DDD or VDD pacemaker implantation for intermittent atrioventricular (AV) block. Forty‐six episodes of repetitive atrial undersensing were found during 24‐hour Holter ECG in nine patients. Pacemaker syndrome‐like symptoms occurred. Episodes were elicited by atrial or ventricular premature contractions when (1) native AV conduction was present but considerably prolonged, (2) intrinsic sinus rate exceeded pacemaker intervention rate, and (3) native AV interval plus PVARP exceeded sinus cycle length. Programming of a particularly short AV interval and PVARP helped to reduce the incidence of repetitive P wave undersensing. Patients with dual chamber devices and prolonged native AV conduction are prone to develop episodes of output inhibition. Standard timing cycles may be inappropriate in these patients.
Impact of the ECG for Detection of Intraatrial Conduction Block after Atrial Flutter Ablation
Authors: WEISS CHRISTIAN , WILLEMS STEPHAN , HOFFMANN MATTHIAS , MEINERTZ THOMAS
Published: July 2006

Induction of complete bidirectional conduction block via the posterior isthmus of the right atrium is introduced as a standard endpoint for catheter ablation of atrial flutter. The present study sought to investigate the impact of changes in P wave duration and morphology detected by the surface ECG during coronary sinus and posterolateral right atrial stimulation as a marker for conduction block. Morphology and duration changes of the paced P wave before and after radiofrequency catheter (RFC) ablation were estimated in 22 patients referred for ablation of atrial flutter. We looked for a morphology change of the terminal portion in the 12‐lead ECG and an increment of P wave duration. In 16 of 22 patients in whom atrial flutter ablation resulted in a complete bidirectional block, the conduction block was unidirectional in 4 patients and conduction times remained unchanged in 2 patients. After induction of complete bidirectional block a change of the terminal portion of the P wave towards a more positive morphology in one or more inferior leads was detected in 14 (88%) of 16 patients during coronary sinus stimulation and in 15 (94%) of 16 patients during posterolateral right atrial stimulation. These changes were predominantly observed in the inferior leads. Positive morphology changes of the terminal P wave portion in the inferior leads indicating conduction block with a sensitivity of 86% and a specificity of 100% were observed. An increment of 10 ms or more in P wave duration indicates conduction block with a specificity of 100% and a sensitivity of 67%. There was a significantly larger increment of P wave duration during coronary sinus (CS) stimulation compared to posterolateral right atrial stimulation (38 ± 21 vs 16 ± 21 ms). The analysis of P wave duration and morphology in the inferior leads of the surface ECG is a reliable tool to assess the intraatrial conduction after atrial flutter ablation. Different conduction during coronary sinus and pos‐terolateral right atrial pacing may cause a different P wave duration after ablation.
Evolution of QRS Duration after Myocardial Infarction: Clinical Consequences
Authors: BREMBILLA‐PERROT BÉATRICE , HOURIEZ PIERRE , CLAUDON OLIVIER , PREISS JEAN‐PHILIPPE , DE LA CHAISE ARNAUD TERRIER
Published: July 2006

The natural history of late potentials after acute myocardial infarction (AMI) has been studied in the first 2 years following myocardial infarction (MI). The purpose of the study was to assess the influence of some time delays since MI, including a time delay longer than 2 years on signal‐averaged ECG (SAECG). SAECG was recorded at 40‐Hz high pass filtering in 40 patients 10 days after acute MI (SAECG 1), then repeated 6–12 months later (mean 9 ± 3 months) (SAECG 2), and then, 2–4 years later (mean 3 ± 2 years) (SAECG 3). QRS duration, root mean square voltage of the last 40 ms of QRS (RMS 40), and low amplitude signal duration (LAS) were measured at the first (1), second (2), and third recording (3). Results: (***P < 0.001)

The analysis of individual results showed a lengthening QRS duration at the third recording only in patients who had a decreased left ventricular ejection fraction (LVEF) at the third recording. In 12 patients with LVEF > 40%, QRS duration did not change at the first and third recording (104 ± 15 vs 101 ± 12 ms). In all 28 patients, but one with LVEF < 40%, QRS duration increased from 107 ± 12 to 128 ± 18 ms*. There was no correlation between QRS duration and LVEF at the second recording and no correlation between QRS duration increase at the third recording and the presence or not of late potentials at the first recording. QRS duration lengthening at the third recording was significantly correlated with a left ventricular (LV) dilatation occurrence at the two‐dimensional echocardiogram. All arrhythmic events, but two, occurred in patients who developed a QRS duration prolongation and were significantly correlated (P < 0.01) to a mean longer QRS duration (132 ± 20 ms) than in patients without arrhythmic events (113 ± 17 ms). In conclusion, the patients with a LV impairment, and who developed a LV dilatation several months after AMI, presented a delayed lengthening of QRS duration noted only at least 2 years after infarction. These patients are at risk of arrhythmic events.
Comparison of Different Methods for Manual P Wave Duration Measurement in 12‐Lead Electrocardiograms
Authors: DILAVERIS POLYCHRONIS , BATCHVAROV VELISLAV , GIALAFOS JOHN , MALIK MAREK
Published: July 2006

To determine whether different methods for the manual measurement of P wave duration are mutually consistent, we evaluated the intraobserver and interobserver errors of P wave measurements obtained in three different ways: (1) by cursor on a high resolution computer screen (on screen), (2) by calipers and a magnifying glass (on paper), and (3) by a high resolution digitizing board (on board). The agreement between the methods was assessed in 30 normal subjects and 30 patients with a history of atrial fibrillation. The maximum P wave duration (P maximum), the minimum P wave duration (P minimum), mean P wave duration (P mean), P wave dispersion (P dispersion = P maximum ‐ P minimum), and the standard deviation of the P wave duration in all measured leads (P SD) were calculated from a 12‐lead electrocardiogram in each subject. Only P maximum, P mean, and P dispersion were significantly higher in patients than in controls with all three methods. Intraobserver and interobserver relative errors were significantly different among the three methods; the lowest errors were associated with the on‐screen measurement. The agreement between the three different methods was acceptable for P maximum, P mean, and P SD and rather poor for P minimum and P dispersion in both groups. The differences of the measurement by different methods did not consistently differ between the two groups. Hence, the on‐screen measurements are consistent with other manual methods and provide more stable results. Manual measurement of ECG patterns should be preferably performed with digital ECG recordings displayed on a high resolution computer screen.
Peripheral Pulmonary Migration of a Retained Pacemaker Lead
Authors: BÕHM ÁDÁM , KOMÁROMY KATALIN , PINTÉR ARNOLD , PRÉDA ISTVÁN
Published: July 2006

We report a case of lead migration into the right middle pulmonary lobe. The migrated electrode reached the pleura and produced severe pleural symptoms, therefore, surgical removal of the retained lead was required. This case report demonstrates the importance of a chest X ray in the follow‐up of patients with an implanted pacemaker to detect complications like lead fracture or migration.