bluuebunny/crossref_metadata_2025 huggingface dataset:
Implantable Cardioverter Defibrillator Lead Technology: Improved Performance and Lower Defibrillation Thresholds
Authors: LANG DOUGLAS J. , HEIL JOHN E. , HAHN STEPHEN J. , LINDSTROM CURT C. , DERFUS DEAN L.
Published: July 2006

The performance of an ICD system depends, in part, on the effectiveness with which the lead system functions. Engineering trade‐offs are made during the design of a lead to optimize one or more performance characteristics: e.g., lead handling, fatigue life, size, and optimized therapy delivery. To assure low defibrillation thresholds, careful attention must be taken during the design process to prevent these trade‐offs from hampering the lead's therapy effectiveness. Four basic design rules are described that capture many of the engineering concepts that will enhance a lead's efficacy: (1) minimize electrode pullback, (2) deliver current to the apex, (3) minimize energy loss in the lead, and (4) use large, efficient electrodes. These rules speak to optimizing delivery of current to the heart and efficiency of the lead and electrode interface. When the lead performs its function well, the complete ICD system of the heart, lead, and implantable pulse generator will provide optimal safety margins for device implant and an increased number of patients that can be implanted with a single‐lead system.
Signal‐Averaged Electrocardiography of the Sinus and Paced P Wave in Sinus Node Disease
Authors: KEANE DAVID , STAFFORD PETER , BAKER STEPHANIE , LEWIS SUSIE , JACKSON GRAHAM , VINCENT RICHARD
Published: July 2006

The detection of paroxysmal atrial fibrillation (AF) in patients requiring a permanent pacemaker for sinus node disease may influence the choice of both pacemaker and programmed mode. While signal‐averaged ECG of the P wave (SAEP) during sinus rhythm may detect patients with paroxysmal AF, the value of SAEP in the presence of sinus node disease is unknown. We therefore evaluated SAEP in patients with sinus node disease during sinus rhythm and atrial pacing. We investigated 10 patients with sinus node disease alone (SND), 10 with sinus node disease and paroxysmal AF (SND‐PAF), and 20 normal controls (NC) using a P wave specific, signal‐averaging system. In sinus rhythm, duration and energy were greater in SND‐PAF than in SND and NC (mean [SEM] duration: 153 [4] msec, 140 [4] msec, and 134 [2] msec, P < 0.001; energy from 20–150 Hz: 76 [18] μV2‐sec, 48 [7] μV2‐sec, and 36 [3] μV2‐sec, P = 0.006). Atrial pacing in SND‐PAF produced an 11% prolongation of atrial activation but little further abnormality in P wave characteristics. In SND, atrial pacing caused a 20% prolongation of the P wave and increased P wave energy to a greater extent than in SND‐PAF. We conclude that in patients with SND, atrial activation appears similar to normal controls during sinus rhythm but changes significantly on pacing. In patients with SND‐PAF, atrial activation is abnormal during sinus rhythm with little further change when the atrium is paced. SAEP may be useful in detecting a predisposition to paroxysmal AF in the presence of sinus node disease and might help optimize pacemaker prescription.
Comparison of Biphasic and Monophasic Pulses: Does the Advantage of Biphasic Shocks Depend on the Waveshape?
Authors: NATALE ANDREA , SRA JASBIR , KRUM DAVID , DHALA ANWER , DESHPANDE SANJAY , JAZAYERI MOHAMMAD , AXTELL KATHY , DEGROOT PAUL , VanHOUT WARREN L. , AKHTAR MASOOD
Published: July 2006

With present implantable defibrillators, the ability to vary the defibrillation technique has been shown to increase the number of patients suitable for transvenous system. As newer waveforms become available, the need for a flexible device may change. In addition, although it has been shown that the option of biphasic waveform may increase the defibrillation efficacy, this may depend upon the shape of the biphasic waveform used. Thirty patients undergoing transvenous defibrillator implant were included in the study. In 20 patients (group I), defibrillation efficacy of simultaneous monophasic, sequential monophasic, and biphasic waveform with 50% tilt was determined randomly. Similarly, in ten patients (group II) testing of simultaneous monophasic shocks and biphasic waveforms with 65% and 80% tilt was performed in random order. The electrode system used consisted of two transvenous leads and a subcutaneous patch in all 30 patients. In group I, 50% tilt biphasic waveform consistently provided similar or better defibrillation efficacy compared to monophasic waveforms (biphasic 7.5 ±5.1 joules vs simultaneous 17 ± 7.8 joules, P < 0.01; and vs sequential 17 ± 8.4 joules, P <0.01). In group II, 65% tilt biphasic pulse required less energy for defibrillation as compared with simultaneous monophasic shocks (9.6 ± 4.5 joulesvs 15.6 ± 5.1 joules, P = 0.04). No significant difference was observed in terms of defibrillation threshold between 80% tilt biphasic shocks and simultaneous monophasic pulses (11.8 ± 6 joules vs 15.6 ±5.1 joules, P = NS). Biphasic shocks with smaller tilt delivered using a triple lead system more uniformly improved defibrillation threshold over standard monophasic waveforms.
Diurnal Fluctuations in Human Ventricular and Atrial Refractoriness
Authors: HUIKURI HEIKKI V. , YLI‐MÄYRY SINIKKA , LINNALUOTO MARKKU K. , IKÄHEIMO MARKKU J.
Published: July 2006

The relative significance of the direct and indirect effects ofautonomic tone on diurnal fluctuations in human ventricular and atrial refractoriness are not well known. In this study, the circadian rhythms of ventricular and atrial effective refractory periods (ERPs) were measured by noninvasive programmed stimulation in ten patients (mean age 62 ± 10 years) who had a permanent dual chamber pacemaker for complete atrioventricular (AV) block. The ERP was measured at 4‐hour intervals during spontaneous sinus rhythm with ventricular pacing (day 1)and during constant‐rate dual chamber pacing (day 2). Cosinor analysis showed the ventricular ERP to have a significant diurnal rhythm in sinus rhythm (amplitude, 12 msec; 95% confidence intervals 1–24 msec) but not during constant‐rate pacing (amplitude, 4 msec; 95% confidence intervals ‐3–12 msec). The atrial ERP had a significant rhythm at times of both spontaneous sinus rate (amplitude, 19 msec; confidence intervals 13–24 msec) and constant heart rate (amplitude, 11 msec; confidence intervals 1–21 msec) with acrophase during the sleeping hours. The increase in heart rate during dual chamber pacing resulted in a more marked decrease in the average 24‐hour ERP in the ventricle than in the atrium (46 ± 9 msec vs 12 ± 6 msec, P < 0.01). Thus, refractoriness is more rate dependent in the ventricle than in the atrium, and autonomic influences on ventricular refractoriness are mainly indirect, via fluctuations in the sinus rate, but atrial refractoriness is also affected by direct neural influences and/or other rate independent factors.
The “Low Intensity Treadmill Exercise” Protocol for Appropriate Rate Adaptive Programming of Minute Ventilation Controlled Pacemakers
Authors: LEW ALTER THORSTEN , MacCARTER DEAN , JUNG WERNER , BAUER TORSTEN , SCHIMPF RAINER , MANZ MATTHIAS , LÜDERITZ BERNDT
Published: July 2006

The objective of rate adaptive pacemakers that measure minute ventilation by tmnsthoracic impedance is to simulate the physiological relationship of the sensed signal to the sinus node response during exercise, thus achieving an appropriate matching of heart rate with patient effort. The purpose of this study was to determine the physiological relationship between heart rate and minute ventilation (HR/VE) during peak exercise testing in order to develop a database for appropriate rate adaptive slope programming of minute ventilation controlled pacemakers. Due to several clinical limitations of peak exercise testing, it was additionally determined whether the 35‐watt “low intensity treadmill exercise” (LITE) protocol can be used as a substitute for peak exercise test using the “ramping incremental treadmill exercise” (RITE) protocol in order to assess the correct HR/VE slope below the anaerobic threshold. The stress tests were performed on a treadmill with the collection of breath‐by‐breath gas exchange. Linear regression analysis was used to determine the HR/VE slope below and above the anaerobic threshold and during the early, dynamic phase of low intensity exercise with the RITE and LITE protocols, respectively. The results of this testing in 41 healthy subjects demonstrated that the HR/VE relationship throughout treadmill exercise using the RITE protocol was not linear but curvilinear in nature, with a steeper HR/VE slope of 1.54 ± 0.51 below versus 1.15 ± 0.37 above the anaerobic threshold (P < 0.005). The HR/VE slope determined during the early, dynamic phase of the LITE protocol (1.58 ± 0.88) did not differ from the HR/VE slope from rest to anaerobic threshold obtained using the peak exercise RITE test (1.54 ± 0.51; P = 0.79), Rate adaptive pacing should simulate the curvilinear relationship between heart rate and minute ventilation from rest to peak exercise. The HR/VE slope determined during the early, dynamic phase of low intensity exercise represents the HR/VE slope derived from the RITE protocol below the anaerobic threshold. According to the peak exercise database, the slope above anaerobic threshold can easily be calculated as a percentage of the slope below the anaerobic threshold. The LITE protocol can, therefore, be effectively performed as a substitute for peak exercise stress tests to determine the correct pacemaker rate response factor in order to obtain a physiological heart rate to minute ventilation relationship for the appropriate matching of paced heart rate with patient effort.
Radiofrequency Catheter Ablation of Atriofascicular Accessory Pathways Guided by Discrete Electrical Potentials Recorded at the Tricuspid Annulus
Authors: BRUGADA JOSEF , MARTÍNEZ‐SÁNCHEZ JUAN , KUZMICIC BORIS , FIGUEIREDO MARCIO de O. , MATAS MARIONA , PAVA LUIS F. , NAVARRO‐LÓPEZ FRANCISCO
Published: July 2006

Background: The purpose of this study was to test the feasibility of using the recording of discrete electrical potentials to guide radiofrequency catheter ablation of atriofascicular accessory pathways with Mahaim‐like properties. Methods and Results: Four patients (3 females, 1 male) who fulfilled criteria for having atriofascicular accessory pathways with Mahaim‐like properties and preexcited reciprocating tachycardia underwent radiofrequency catheter ablation. The mean age was 35 years (range 27–47). Symptoms were present for a mean of 10.5 years (range 6–18). Recording of discrete electrical potentials of the atriofascicular pathway was attempted by mapping the tricuspid annulus in sinus rhythm, during atrial pacing, and during reciprocating tachycardia. During atrial pacing, a mean of seven radiofrequency pulses (range 1–14), delivered to the tricuspid annulua at the area where electrical potentials were recorded, eliminated conduction through the atriofascicular accessory pathway in all patients. No complications occurred. Tachycardia did not reoccur during a mean follow‐up of 5 months (range 3–9). Conclusions: Recording of discrete electrical potentials at the tricuspid annulus identifies an optimal ablation site where radiofrequency current can safely eliminate conduction through atriofascicular accessory pathways with Mahaim‐like properties.
Reproducibility of Electrophysiological Testing During Antiarrhythmic Therapy for Ventricular Arrhythmias Unrelated to Coronary Artery Disease
Authors: FERRICK KEVIN J. , MAHER MICHAEL , ROTH JAMES A. , KIM SOO G. , FISHER JOHN D.
Published: July 2006

Although electrophysiological studies are commonly used in the management of patients with ventricular tachycardia (VT), the reproducibility of these studies during therapy has not been established in patients in whom VT is associated with conditions other than coronary artery disease. Therefore, we performed confirmation studies during drug therapy in 60 patients (mean age 48 ± 18 years; 41 male) with sustained ventricular arrhythmias induced during initial study to assess the reproducibility of drug effect. The stimulation protocol used included the serial introduction of up to three premature ventricular stimuli during sinus rhythm and with ventricular pacing at two pacing rates. Rapid ventricular pacing techniques were also used. Antiarrhythmic drug efficacy was confirmed in 78% of patients. Sustained VT was induced at repeat electrophysiological study in 18% of patients daring antiarrhythmic therapy that had been felt to be effective on the basis of a single drug study. We conclude that electrophysiological study results during antiarrhythmic therapy exhibit significant day‐to‐day variability. Sustained VT can be induced during antiarrhythmic therapy previously determined to be effective by electrophysiological techniques in many patients.
Plasma Catecholamines and Cyclic AMP Response During Head‐Up Tilt Test in Patients with Neurocardiogenic (Vasodepressor) Syncope
Authors: ABE HARUHIKO , KOBAYASHI HIDEYUKI , NAKASHIMA YASUHIDE , IZUMI FUTOSHI , KUROIWA AKIO
Published: July 2006

To examine hemodynamic, plasma Catecholamines, and cyclic AMP changes during tilt in patients with neurocardiogenic (vasodepressor) syncope, six patients underwent 80± head‐up tilt test for 10 minutes with isoproterenol infusion (1–3 μg/min). Venous blood was sampled in the supine position, at 3 minutes of tilt, and at the onset of vasodepressor reaction during tilt. AH patients had previous tilt studies in which vasodepressor syncope had been induced reproducibly (mean 3.3 episodes in each patient). Syncope was induced at 6.1 ± 0.4 minutes of tilt with an infusion of isoproterenol (mean 1.7 ± 0.3 fig/min). Although arterial pressure and heart rate did not change significantly between in the supine position and at 3 minutes of tilt, plasma norepinephrine increased significantly at 3 minutes of tilt (0.44 ± 0.10 ng/mL; P < 0.05) and at the onset of vasodepressor reaction (0.49 ± 0.12 ng/mL; P < 0.01) compared to the supine position with isoproterenol (0.34 ±0.10 ng/mL). Also, cyclic AMP (cAMP) increased significantly at 3 minutes of tilt (25.3 ± 2.0 pmol/mL; P < 0.005) and at the onset of vasodepressor reaction (29.6 ±1.7 pmol/mL; P < 0.005) compared to the supine position with isoproterenol (20.4 ±1.9 pmol/mL). After administration of selective beta1‐blocker, metoprolol (40 mg/day), plasma norepinephrine, and cAMP during tilt did not change significantly compared to baseline tilt. However, metoprolol prevented the syncope in 3 of 6 patients. After administration of beta1‐, beta2‐ blocker, propranolol (30 mg/day), cAMP at 3 minutes of tilt decreased significantly compared to the baseline tilt (16.9 ±1.4 pmol/mL vs 25.3 ± 2.0 pmol/mL; P < 0.05) and propranolol prevented the syncope in all six patients. We concluded that the increase of cAMP may play an important role for the induction of vasodepressor reaction in patients with neurocardiogenic (vasodepressor) syncope. The concentration ofcAMP showed more sensitive response to vasodepressor reaction than that of norepinephrine.
Inconsistent Response to Rapid Atrial Rhythms in a DDD Pacemaker with the Fallback Feature
Authors: JOHNSON NANCY J.
Published: July 2006

Dual chamber pacing may be problematic in patients with paroxysmal atrial arrhrfhmias. The fallback feature has been incorporated into some devices to avoid tracking of rapid atrial rhythms. A case is reported in which the initiation of fallback was inconsistent during paroxysms of atrial flutter. Evaluation of the ventricular output of an isolated device in response to various applied atrial rates revealed that fallback occurred consistently only when 2×TARP (ms) ≤ URL (ms).
Relationship Between Heart Rate and Oxygen Kinetics During Constant Workload Exercise
Authors: KAY G. NEAL , ASHAR MANISHA S. , BUBIEN ROSEMARY S. , DAILEY SHARON M.
Published: July 2006

Background: Oxygen uptake during constant workload exercise increases exponentially from its resting value before reaching a steady state. The difference between the actual rate of oxygen consumption at the onset of exercise and the steady state is an oxygen deficit. Similarly, the normal sinus node increases its rate at the onset of exercise before achieving a steady state, thereby producing a heart rate deficit. The purpose of this study was to test the hypothesis that elimination of the heart rate deficit by an instantaneous increase in heart rate at the onset of constant workload exercise to the steady‐state level would reduce the oxygen deficit and improve the perceived difficulty of exertion as compared with the chronotropic response of the normal sinus node. Methods and Results: Ten subjects with normal sinus node function who had DDD pacemakers implanted for A V block completed a symptom‐limited maximal treadmill exercise test using the Chronotropic Assessment Exercise Protocol (CAEP) to assess sinus node function, maximal heart rate, and VO2 max. The subjects then performed constant workload exercise tests (6‐min duration) at a workload equal to approximately 50% of metabolic reserve with the pacemaker randomly programmed to each of three patterns of chronotropic response: (1) DDD (lower rate 60 beats/ min); (2) Fast (lower rate abruptly programmed to the expected value at 50% metabolic reserve); and (3) Overpaced (lower rate at least 80% of the age predicted maximum). The oxygen deficit was lower with the fast chronotropic response (434 ± 238 ml O2) than with either the DDD (512 ± 233; P = 0.02), or overpaced chronotropic patterns (488 ± 238; P = 0.02 vs fast). The rate constant for change in VO2 was highest with the fast chronotropic pattern (2.85 ± 1.38) compared with either the DDD (2.25 ± 0.64; P = 0.01) or overpaced (2.38 ± 0.43; P = 0.02) patterns. The Borg perceived exertion rating was lowest with the fast chronotropic response (P = 0.02 vs DDD and P = 0.02 vs overpaced). Conclusions: The results of this study suggest that oxygen kinetics and exertional symptoms are improved by an abrupt increase in pacing rate at the onset of exercise to a value that is appropriate for metabolic demand as compared with the DDD pacing mode in patients with normal sinus node function. In contrast, an overly aggressive chronotropic response was not associated with improved oxygen kinetics or exertional symptoms.
Analysis of the Body Surface ECG Measured in Independent Leads During Ventricular Fibrillation in Humans
Authors: CLAYTON RICHARD H , MURRAY ALAN , CAMPBHLL RONALD W.F.
Published: July 2006

The degree of myocardial electrical organization during ventricular fibrillation remains unknown. The aim of this study was to compare the characteristics of the surface ECG on three independent and approximately orthogonal leads. Ten recordings of ventricular fibrillation. each induced at electrophysiology study and successfully terminated by direct current shock, were analyzed. Each recording was divided into 1‐second epochs for analysis. Frequency analysis using the Fast Fourier Transform showed that the frequency of the dominant spectral peak increased significantly from a mean of 4.1 ±0.8 Hz to 5.2±0.7 Hz during the first 5 seconds of ventricular fibrillation. In 95% of the epochs analyzed, a similar dominant frequency was observed on either two or three ECG leads. Frequency agreement tended to increase as ventricular fibrillation evolved. This study shows that the rate of ventricular fibrillation increases rapidly during the first 5 seconds but only gradually thereafter, and that similar signal characteristics are observed on independent ECG leads. These findings are not compatible with the traditional view of incoherent myocardial activity during ventricular fibrillation.
Effects of Initial Polarity on Defibrillation Threshold with Biphasic Pulses
Authors: NATALE ANDREA , SRA JASBIR , DHALA ANWER , JAZAYERI MOHAMMAD , DESHPANDE SANJAY , AXTELL KATHI , AKHTAR MASOOD
Published: July 2006

Background: Previous studies have shown that the polarity of epicardial patches significantly affects the defibrillation efficacy of monophasic shocks. Howevar, whether this improvement can he extended to different pulsing methods and lead systems, such as biphasic shocks using endocardial defibrillating electrodes, is unknown. Methods: Twenty consecutive patients undergoing testing and permanent implant using an Endotak lead system with a biphasic device were included in the study. In each patient the defibrillation threshold was determined delivering biphasic pulses with the distal coil as the cathode and the proximal coil as the anode during the positive phase and with the polarity reversed. The initial electrode polarity tested was chosen randomly. The defibrillation threshold was defined as the lowest pulse amplitude that effectively terminated ventricular fibrillation induced with 60‐Hz alternating current. For each biphasic pulse peak voltage, pulse duration, resistance, and stored energy were recorded. Results: Of the 20 patients, 12 (60%) had lower defibrillation threshold when the proximal coil was negative, whereas only 2 patients had a lower defibrillation threshold when the distal coil was negative. In four patients a subcutaneous patch would have been required if only the biphasic pulse with the distal coil as negative had been tested. The mean stored defibrillation threshold energy was lower with the configuration using the proximal coil as cathode (16.3 ±8.8 J vs 21.5 ±11 J; P < 0.01). Conclusion: Change in the initial polarity of biphasic shocks may influence defibrillation efficacy and should, therefore, be assessed in each patient to achieve a more satisfactory safety margin and minimize the use of more invasive lead configurations.
Catheter Aided Repositioning of a Displaced Permanent Pacemaker Lead
Authors: S̄OCHMAN JAN , LEFFLEROVÁ KATER̄INA , VRBSKÁ JANA , KOVÁC̄ JOSEF
Published: July 2006

A 91‐ year‐old woman, who had a pacemaker implanted in 1977, underwent replacement of a pulse generator and lead in 1995 because of recurrent syncope. The new lead dislodged the next day and migrated to the pulmonary artery. Because of her dependence on continued pacing, repeated resuscitation was required. Considering her advanced age and the impact of cardiopulmonary resuscitation on her general condition, we attempted catheter aided repositioning of the pacemaker lead. The procedure was technically successful: lead position was stable and optimal pacing parameters were attained. She was discharged in good condition.
Influence of Malpositioned Transvenous Leads on Defibrillation Efficacy With and Without a Subcutaneous Array Electrode
Authors: USUI MASAHIRO , WALCOTT GREGORY P. , KENKNIGHT BRUCE H. , WALKER ROBERT G. , ROLLINS DENNIS L. , SMITH WILLIAM M. , IDEKER RAYMOND E.
Published: July 2006

Some patients cannot receive a transvenous lead system because of high defibrillation thresholds (DFTs). We hypothesized that a right ventricular (RV) catheter electrode not extending as far as possible into the RV apex could cause high DFTs, Recently, a subcutaneous array (SQA) electrode has been shown to lower DFTs substantially. We compared the influence of a malpositioned RV catheter electrode on defibrillation efficacy for endocardial lead systems with and without a SQA. In eight anesthetized pigs, defibrillation catheters were placed in the RV apex and near the junction of the superior vena cava (SVC) and right atrium. SQA, formed by three elements, each 20 cm in length, was placed in the left thorax. DFTs were determined for a biphasic waveform using an up/ down protocol with the RV catheter at the apex and with it repositioned 1‐cm and 2‐cm proximal to the apex. The mean DFT energies for the configurations with a SQA were less than those without a SQA for every catheter position. The placement of the RV catheter away from the apex caused an increase in defibrillation energy for the configurations without a SQA (apex: 17.1 ± 3.8 J [mean ± SD]; 1 cm: 20.1 ± 4.6 J; 2 cm: 27.6 ± 9.5 J; P ± 0.05), but not for the configurations with a SQA (apex: 12.2 ± 2.2 J; 1 cm: 12.3 ± 2.9 J; 2 cm: 12.1 ± 0.9 J: P= NS). These results suggest that a malpositioned RV catheter electrode, at the time of implantation or by late dislodgment, significantly elevates DFTs for a total endocardial system but not for a system that includes a SQA.
Adverse Pacemaker Hemodynamics Evaluated by Pulmonary Venous Flow Monitoring
Authors: STIERLE ULRICH , KRÜGER DIETMAR , MITÜSCH ROLF , POTRATZ JÜRGEN , TAUBERT GUNNAR , SHEIKHZADEH ABDOLHAMID
Published: July 2006

The pacemaker syndrome refers to symptoms and signs in the pacemaker patient caused by an inadequate timing of atrial and ventricular contractions. The lack of normal atrioventricular synchrony may result in a decreased cardiac output and venous cannon A waves. The objective of this study was to define the left atrial and pulmonary venous flow response to ventricular pacing in a group of 14 unselected consecutive patients with total heart block and sinus rhythm. Pulmonary venous flow was assessed by transesophageal pulsed Doppier echocardiography in the VVI and ODD pacing modes. An inappropriate atrial timing caused a marked augmentation of the normally small pulmonary venous z wave in all patients (“negative atrial kick” peak z wave in DDD pacing 14.5 ± 4.6 cm/s, VVI pacing 51.8 ± 15.0 cm/s). Restoration of AV synchrony (DDD pacing, AV interval 100 ms) abolished these “cannon z waves” in all patients, and a normal pattern of pulmonary venous flow was achieved. Abnormal pulmonary venous flow characteristics were observed in 2 of 14 patients during DDD pacing with short AV intervals (100 ms). The Doppier pattern was similar to the findings seen in VVI pacing. Assessment of pulmonary venous flow by transesophageal pulsed Doppier echocardiography may provide a simple, sensitive, and relatively noninvasive technique to evaluate patients with suspected pacing induced adverse hemodynamics.
Efficacy of Antitachycardia Pacing in Patients Presenting with Cardiac Arrest
Authors: MITRA RAMAN L. , HSIA HENRY H. , HOOK BRUCE G. , CALLANS DAVID J. , FLORES BELINDA T. , MILLER JOHN M. , JOSEPHSON MARK E. , MARCHLINSKI FRANCIS E.
Published: July 2006

The efficacy of antitachycardia pacing (ATP) incorporated into implantable cardioverter defibrillators (ICDs) was assessed in 29 consecutive survivors of cardiac arrest, not attributable to acute myocardial infarction, ischemia, or drug and electrolyte effects. The cohort included 25 men and 4 women with a mean age of 65 years and a mean left ventricular ejection fraction of 29%. Seventeen patients had coronary artery disease, 11 had nonischemic dilated cardiomyopathy, and 1 had long QT syndrome. Programmed stimulation yielded monomorphic ventricular tachycardia (VT) in 17 patients, polymorphic VT in 6, and no inducible VT in 6. During a mean follow‐up of 22 months, a total of 91 episodes of monomorphic VT occurred, 73 of which were successfully pace terminated (83%). Monomorphic VT amenable to pace termination recurred only in the group that had this arrhythmia inducible. The recurrent arrhythmias in the 12 patients having either no inducible VT or polymorphic VT were all rapid VTs, having a cycle length < 220 ms; and therefore, not amenable to pace termination. These results suggest that ATP incorporated into ICDs is useful in survivors of cardiac arrest and may significantly reduce the number of shocks that these patients would otherwise receive. Programmed stimulation may also help to define those patients who would receive the maximum benefit from ATP.
Incidence of ICD Lead Related Complications During Long‐Term Follow‐Up: Comparison of Epicardial and Endocardial Electrode Systems
Authors: KORTE THOMAS , JUNG WERNER , SPEHL SUSANNE , WOLPERT CHRISTIAN , MOOSDORF RAINER , MANZ MATTHIAS , LÜDERITZ BERNDT
Published: July 2006

The aim of this study was to evaluate the longterm stability of epicardial and endocardial lead systems for third‐generation cardioverter defibrillators (ICDs) and to assess the usefulness of diagnostic tools. One hundred forty patients with 61 epicardial (43.6%) and 79 nonthoracotomy systems (56.4%) were followed for 2 5 ± 19 months. A total of 18 (12.9%) lead related complications were documented. Complications of epicardial systems were detected in 10 patients (16.4%) during a follow‐up time of 36 ± 8 months: crinkling of patch electrodes in 6 patients (9.8%), insulation breakage of sensing electrodes in 2 patients (3.3%), and adapter defect in 2 patients (3.3%). Eight of the patients (10.1%) with transvenous‐subcutaneous systems had lead related complications during a 13 ± 6 months follow‐up: fracture of the subcutaneous patch lead in 2 patients (2.5%), dislodgment of the right ventricular lead in 2 patients (2.5%), dislodgment of the superior vena cava lead in 2 patients (2.5%), insulation breakage of sensing electrodes in 1 patient (1.3%), and connector defect in 1 patient (1.3%). There was no significant difference in the incidence of lead related complications between epicardial and endocardial systems (P > 0.05). Fractures, dislodgments, and crinklings were documented within the first 8 ± 5 months by regular chest X ray. Defects of insulation, adapter, or connector were detected 22 ± 10 months after implantation and were associated with delivery of multiple inappropriate ICD therapies. An operative lead revision was indicated for 4 epicardial (6.6%) and 6 endocardial (7.6%) lead systems. Conclusions: Endocardial lead systems offer a similar long‐term stability as compared to epicardial had systems. Chest X ray is the most useful tool to detect lead fracture, dislodgment. and patch crinkling. Marker recordings or real‐time electrograms have not been helpful in this series to identify patients with suspected lead defects prior to the experience of inappropriate ICD discharges.
Anatomical Findings in Patients Having Had a Chronically Indwelling Coronary Sinus Defibrillation Lead
Authors: JONES GREGORY K. , SWERDLOW CHARLES , REICHENBACH DENNIS D. , LONES MARK , POOLE JEANNE E. , LEE DOLACK G. , KUDENCHUK PETER J. , BARDY GUST H.
Published: July 2006

The purpose of this report is to review the gross and histological cardiac anatomical findings in patients with chronically indwelling coronary sinus leads at the time of autopsy or cardiac transplantation. Transvenous cardioverter defibrillators offer effective protection against sudden death. The use of a coronary sinus electrode has been shown in some patients to decrease the defibrillation threshold. The anatomical consequences of chronically indwelling coronary sinus cardioversion /defibrillation electrodes in patients having transvenous implantable cardioverter defibrillators is unknown. The hearts of seven patients with chronically indwelling coronary sinus electrodes were evaluated following autopsy (n= 2) or cardiac transplantation (n= 5), The coronary sinus electrode in each case was a 6.5 French silicon lead with a 5‐cm long defibrillation coil (Medtronic CS lead model 6933) that was positioned as distally as possible within the coronary sinus at the time of implantable cardioverter defibrillator surgery. The seven hearts examined were derived from patients whose age ranged between 49 and 69 (mean 56 ± 7 years). Six had coronary artery disease and one had idiopathic dilated cardiomyopathy. The time from implant to death or cardiac transplantation was 8 ± 6 months, range 1–18 months. In all seven patients, there was no evidence of any significant damage from the presence of the coronary sinus lead. The only finding in each case was the scattered presence of a thin white fibrous sheath over the lead that intermittently adhered to the coronary sinus endothelium and, in the two patients transplanted 1–3 months after implantable cardioverter defibrillator insertion, a mild inflammation reaction adjacent to the leads in the coronary sinus endothelium. There was no evidence of coronary sinus occlusion, adjacent coronary artery injury, coronary sinus perforation, coronary sinus burn, or myocardial injury adjacent to the lead. Cause of death was due to end‐stage congestive heart failure and thrombotic stroke, respectively, in the two patients examined at autopsy. Coronary sinus defibrillation leads can be used safely without harmful anatomical effect.
Instantaneous Lead Entrapment: An Unusual Complication of Nonthoracotomy Implantation of an Endocardial Defibrillation Lead
Authors: PARSONNET VICTOR , BERNSTEIN ALAN D. , OMAR ARIF M. , ROTHBART STEPHEN T. , SCHOENFELD RICHARD
Published: July 2006

Nonthoracotomy implantation of implantable cardioverter defibrillators is performed with transvsnous leads that are similar to pacemaker leads and are subject to the same potential problems. We report an unusual complication of lead placement in which an electrode immediately became entrapped in the superior rim of the tricuspid valve, resisting all efforts at removal.
Successful Long‐Term Ventricular Pacing Via the Coronary Sinus After the Fontan Operation
Authors: ROSENTHAL ERIC , QURESHI SHAKEEL A. , CRICK JONATHAN C. PITTS
Published: July 2006

A man with double inlet left ventricle and severe subpulmonary stenosis underwent a Fontan operation at the age of 29 years. Eight years later he developed atrial flutter with complete heart block. To avoid a further thoracotomy, a unipolar carbon tipped electrode was placed into the posterior cardiac vein via the coronary sinus. More than 8 years after implantation of the original lead, and after two generator changes, telemetric thresholds remain between 1.8–2.1 volts. Percutaneous transvenous ventricular pacing via the coronary sinus can produce an excellent long‐term result and should be the initial approach of choice after a Fontan‐type operation.
Abnormal Response to Exercise, Face Immersion, and Isoproterenol in Children with the Long QT Syndrome
Authors: KATAGIRI‐KAWADE MAYUMI , OHE TOHRU , ARAKAKI YOSHIO , KURITA TAKASHI , SHIMIZU WATARU , KAMIYA TETSURO , ORII TADAO
Published: July 2006

The present study was performed to observe the change of QT interval by sympathetic stimulations in patients with the long QT syndrome (LQTS). The study group consisted of 6 children with LQTS and 6 healthy children without QT prolongation. All LQTS patients had syncopal episodes. The QTc and ΔQTc% ([QTC interval after examination ‐ QTc interval at rest]/QTc interval at rest × 100) by treadmill testing, face immersion, and isoproterenol were examined. One minute after peak exercise of treadmill testing, the changes in the QTr, interval were not significant in either group, but ΔQTC% was larger in the LQTS group than in the control group (+ 11.0 ± 12.1% vs ‐2.6 ± 3.2%;P= 0.02). The QTc interval at the shortest RR interval during face immersion was prolonged in the LQTS group (0.47 ± 0.01 s to 0.51 ± 0.04 s; P = 0.02), but there were no significant changes in the control group (0.40 ± 0.03 s to 0.41 ± 0.03 s; P = NS). ΔQTC% was larger in the LQTS group than in the control group (+ 10.0 ± 7.3% vs +1.1 ± 5.5%; P = 0.04). In the LQTS group, the RR interval was shortened (P = 0.009) and QTc interval was prolonged (P = 0.0008) after isoproterenol infusion. These sympathetic stimulations amplified the TU abnormality in the LQTS group. By observing the TU changes caused by face immersion, we hoped to find a possible new method with which to diagnose LQTS. The combination of these examinations may be helpful in screening the borderline cases of TU abnormalities.
Long‐Term Clinical Outcome of Right Bundle Branch Radiofrequency Catheter Ablation for Treatment of Bundle Branch Reentrant Ventricular Tachycardia
Authors: MEHDIRAD ALI AKBAR , KEIM STEPHEN , RIST KEVIN , TCHOU PATRICK
Published: July 2006

This study assessed the long‐term outcome of patients undergoing radiofrequency ablation of the right bundle for bundle branch reentrant ventricular tachycardia. Bundle branch reentrant tachycardia was diagnosed in 16 patients (ejection fraction 31%± 15%) who underwent electrophysiology study in our laboratory. All patients had His‐Purkinje system conduction delay with mean HV interval of 68 ± 8 ms. After ablation, right bundle branch block developed in 15 patients. One patient developed complete heart block, which was anticipated. One patient died of heart failure 9 months after ablation. Two patients were successfully bridged to heart transplantation 0.5 and 13 months, respectively, after ablation. Two patients received implantable defibrillators for other ventricular tachycardias. One patient had syncope 11 months after ablation, but there was no evidence of ventricular tachycardia or heart block in repeat electrophysiology study. This patient died suddenly 29 months after ablation. The remaining nine patients were alive and well for a mean follow‐up of 19 ± 10 months. Radiofrequency ablation of the right bundle branch is an effective therapy for treatment of bundle branch reentrant ventricular tachycardia. Survival is excellent provided that other types of ventricular tachycardia, when present, are treated as well. This technique maybe helpful in management of patients who have unacceptable frequent shocks from their implanted defibrillators and may be helpful in avoiding implantation of such a device completely in others. In some patients with terminal heart failure and incessant ventricular tachycardia, this procedure can function as a bridge to cardiac transplantation.
AV Node Reentry Tachycardia in Infants
Authors: CROSSON JANE E. , HESSLEIN PETER S. , THILENIUS OTTO G. , DUNNIGAN ANN
Published: July 2006

The purpose of this study was to determine the frequency of atrioventricular (AV) node reentry tachycardia in infants undergoing transesophageal electrophysiological study for paroxysmal tachycardia. The records of all 52 infants < 1‐year‐old with structurally normal hearts who underwent transesophageal study for paroxysmal tachycardia over a 3‐year period were reviewed. Those with a diagnosis of AV node reentry tachycardia underwent complete data review, and follow‐up of > 12 months was obtained. Six of 52 infants had a diagnosis of the common type of AV node reentry tachycardia. Tachycardia was diagnosed at a mean age of 2.1 months (range 1 day to 10 months), and 3 of 6 underwent transesophageal study within the first month. Although no patient had structural heart disease, three patients had significant noncardiac disease. Follow‐up of 15–38 months (mean 24 ± 7.8) revealed recurrences in 2 of 6 patients. The mean tachycardia cycle length was 240 ms (range 200–310 ms), and the transesophageal ventriculoatrial intervals ranged from < 30 to 55 ms. All patients had an inducible reentrant tachycardia with a ventriculoatrial interval that remained constant even when tachycardia cycle length increased following verapamil or adenosine administration, or decreased following isoproterenol infusion. Five of 6 had evidence for discontinuous AV node conduction curves. In our patients the substrate for AV node reentry tachycardia was present early in life, and AV node reentry tachycardia can be a clinical problem even in the newborn period.
Heart Rate During Spontaneous and Induced Paroxysmal Supraventricular Tachycardia
Authors: HAMER MARK E. , WILKINSON WILLIAM E. , McCARTHY ELIZABETH A. , PAGE RICHARD L. , PRITCHETT EDWARD L.C.
Published: July 2006

It is generally assumed that paroxysmal supraventricular tachycardia (PSVT) induced during invasive electrophysiological study reproduces the patient's spontaneous, clinical arrhythmia. Even in the absence of antiarrhythmic drugs, however, there may be significant differences in characteristics of the induced and spontaneous arrhythmias. We compared the heart rate of PSVT in 38 patients who had undergone electrophysiological study with induction of PSVT who also had a spontaneous episode of PSVT documented by transtelephonic ECG monitoring during a period when all antiarrhythmic drugs were withheld. The heart rate during spontaneous PSVT was faster than the heart rate of PSVT induced during electrophysiological study; the mean difference was 16 beats/min (P < 0.001). We conclude that heart rate of PSVT induced during electrophysiological study generally underestimates the heart rate of spontaneous PSVT in the antiarrhythmic drug‐free state. This may be due to differences in the autonomic and hemodynamic states during spontaneous and induced arrhythmias.
The JT Interval as a Depolarization Independent Measurement of Repolarization: Lessons from Catheter Ablation of the Wolff‐Parkinson‐White Syndrome
Authors: SALIM MUBADDA A. , CASE CHRISTOPHER L. , GILLETTE PAUL C.
Published: July 2006

In patients with Wolff‐Parkinson‐White syndrome (WPW), preexcitation precludes accurate assessment of the ventricular repolarization by the QTC. In patients with long QT syndrome, it has been demonstrated that the JTC does not change when depolarization abnormalities develop. We hypothesized that this phenomenon should also be applicable to WPW patients. To test this, we assessed the surface ECG of 29 patients (16 males, 13 females) with WPW pre‐ and postablation. The QRS, QT, and JT intervals were measured pre‐ and postablation at 50 mm/s paper speed in leads II and V2. QTC and JTC were calculated according to Bazett's formula. The average age was 12.8 ± 4.9 years (range 1.5–21). All patients had no residual preexcitation on postablation ECG. Early and late follow‐up ECGs were obtained at 32 ± 34 days and 388 ± 197 days postablation, respectively. Both the QRS and the QTC intervals shortened significantly on the postablation versus preablation ECGs (QRS: 115 ± 23 ms vs 89 ± 15 ms, respectively; P < 0.0001), (QTC: 454 ± 26 vs 423 ± 23, respectively; P < 0.0001). The preablation JTC interval did not change, postablation (319 ± 21 vs 323 ± 23, respectively; P > 0.2). Also, the JTC interval did not change between early and late follow‐ up, postablation. JTC: is an independent measure of repolarization, not related to depolarization. JTC may be a useful tool in assessing repolarization in patients with WPW and other depolarization abnormalities.
Pacemaker Inhibition Due to Anodal Ring Electrode Contact
Authors: HENDERSON DAVID , MAKER MICHAEL , JOHNSON DELOS
Published: July 2006

A 79‐year‐old patient with a permanent DDD pacemaker due to a complete AV block and severe bradycardia was seen with complaints of syncope. A surface ECG rhythm strip verified the loss of ventricular output with 6‐ second periods of asystole. Subsequent investigation using the pacemaker's annotated event markers and multiple polarity intracardiac eiectrograms indicated spurious signals arising from the anodal ring. On fluroscopic examination intermittent contact was observed between the anodal ring of the pacing had and the ring electrode of an abandoned lead. Reprogramming of the pulse generator's ventricular channel to the unipolar sensing configuration corrected the problem.
Conductive Properties of the Reentrant Pathway of Ventricular Tachycardia During Entrainment From Outside and Within the Zone of Slow Conduction
Authors: AIZAWA YOSHIFUSA , KITAZAWA HITOSHI , WASHIZUKA TAKASHI , TAKAHASHI KAZUYOSHI , SHIBATA AKIRA
Published: July 2006

Ventricular tachycardia (VT) was entrained with rapid ventricular pacing outside and within the zone of slow conduction (SCZ), and the conductive properties of the reentrant pathway were compared between the two pacing sites. Underlying heart diseases were old myocardial infarction (n = 2), postoperative tetralogy of Fallot (n = 1) or double outlet of the right ventricle (n = 1), dilated cardiomyopathy (n = 1), and pulmonary regurgitation of unknown cause (n = 1). Rapid pacing was continued for 5–10 seconds, and the time interval from paced stimulus to the entrained electrogram at the exit from SCZ (St‐Ex) or to the QRS complex (St‐QRS) was measured. Rapid pacing was performed at three or more cycle lengths after a decrement in steps of 10 msec. During rapid pacing outside of SCZ and entrainment of VT, constant fusion and progressive fusion were observed, and St‐Ex and St‐QRS showed the same response pattern: either a frequency dependent prolongation in 4 of 7 VTs or a constant time interval in the others VTs. When rapid pacing was attempted within SCZ, the response of the time intervals from paced site to the QRS (St‐QRS) was the same as those observed during pacing outside SCZ except for one VT. In VT with repaired tetralogy of Fallot, the frequency dependent prolongation was observed during pacing from outside of SCZ but not within SCZ. Diseased myocardium extending widely into the outflow tract of the right ventricle may be responsible for the frequency dependent prolongation of St‐Ex. In conclusion, the conductive property of the reentrant pathway might be assessed by observing the response patterns of St‐Ex or St‐QRS interval during transient entrainment of VT outside of SCZ, but exceptions may exist.
Optimal Truncation of Defibrillation Pulses
Authors: IRNICH WERNER
Published: July 2006

The statement that the optimal pulse for defibriliation has not yet been discovered implies that an ideal pulse exists, but that it is different in shape, duration, and energy as compared to pulses of today. The optimum pulse is that which can defibrillate with lowest energy. Reduction of energy can be reached twofold: by looking for a pulse duration with lowest energy threshold, and by finding the optimal truncation with lowest refibrillating effect. Assuming that there is also a rheobase in defibrillation below which no defibrillating but probably a refibrillating effect exists, the exponential pulse should be truncated if it intersects with the rheobase. Combining the fundamental law of electrostimulation with this boundary condition allows for the mathematical solution of the above problem of optimal energy. Defibrillation can be optimized with respect to pulse duration or tilt and to energy efficiency. The most important parameter in determining other optimized parameters such as output capacitor is the chronaxie. The calculations reveal that the “concept of constant energy” does not accurately describe defibrillation, that today's implantable cardioverter defibrillator devices possess refibrillating tilts, that pulse durations should he programmed to values between 4 and 10 msec, and that smaller output capacitors around 30 μF would minimize the energy requirements. Whether optimized monophasic pulses are inferior or equal to biphasic pulses needs further experimental studies.
Transvenous Cardioverter Defibrillators: Cost Implications of a Less Invasive Approach
Authors: VENDITTI FERDINAND J. , O'CONNELL MARK , MARTIN DAVID T. , SHAHIAN DAVID M.
Published: July 2006

To assess the economic impact of a transvenous lead system for an implantable Cardioverter defibrillator (ICD), we evaluated the hospital charges for two groups of patients: group I patients (n = 23) underwent implantation of an ICD generator with an epicardial lead system via a thoracotomy and group II patients (n = 25) underwent implantation of the same generator using transvenous leads. There was no difference in demographics between the two groups. There was a 15% decrease in total charges for the transvenous group compared to the thoracotomy group ($54,142 vs $63,359, P < 0.05). Evaluation of the component charges revealed that the decline could be attributed to a reduction in implant ($27,328 vs $29,285, P < 0.02) and convalescent charges ($7,703 vs $15,179, P < 0.01) for the transvenous group. There was a corresponding decrease in length of stay for the transvenous group (22 vs 29 days, P < 0.05) largely secondary to a 38% reduction in convalescent length of stay (8 vs 13 days, P < 0.05). We conclude that the use of transvenous lead systems for the ICD results in a significant reduction in hospital charges as well as hospital length of stay.
Intravenous Adenosine During Atrioventricular Reentrant Tachycardia: Induction of Atrial Fibrillation with Rapid Conduction Over an Accessory Pathway
Authors: TEBBENJOHANNS JÜRGEN , PFEIFFER DIETRICH , SCHUMACHER BURGHARD , JUNG WERNER , MANZ MATTHIAS , LUDERITZ BERNDT
Published: July 2006

Adenosine is considered to be a safe agent for termination of orthodromic atrioventricular reentrant tachycardia in patients with accessory pathways. A case with initially successful accessory pathway ablation and without preexcitation during sinus rhythm is presented, in which intravenous adenosine (6 mg) during orthodromic tachycardia was followed by atrial fibrillation and sudden onset of preexcitation with subsequent rapid ventricular response with moderate hemodynamic compromise.