bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Gold Versus Platinum Electrodes on Myocardial Lesion Size Using Radiofrequency Energy
Authors: SIMMONS WALTER N. , MACKEY SEAN , HE DING SHENG , MARCUS FRANK I.
Published: July 2006

During radiofrequency (RF) catheter ablation of arrhythmias, temperatures that approach 100°C cause a coagulum to form on the ablation electrode that results in an increase in electrical impedance and prevents further energy delivery. Since gold has nearly four times the thermal conductivity as platinum, the metal commonly used, it was postulated that gold tip electrodes could deliver more power and produce deeper lesions because of its greater heat dissipation from the electrodetissue interface to the circulating blood. To test this hypothesis, RF energy was applied to fresh bovine ventricular myocardium using 6 French catheters with 2‐mm long distal electrodes made from gold or platinum. Similar studies were also conducted using 7 French catheters with 4‐mm long distal electrodes. Maximum lesion depth was defined as that produced with the level of energy just below that causing an impedance rise. A maximum lesion depth of 6.2 ± 0.7 mm (mean ± SD) was obtained with the gold 2‐mm electrode and 4.7 ± 0.5 mm with the platinum electrode (P = 0.003). The 4‐mm gold electrode produced a maximum lesion depth of 7.2 ± 1.4 mm, while a catheter with a 4‐mm platinum electrode caused a maximum lesion depth of 5.8 ± 0,7 mm (P = 0.05). We conclude that deeper lesions should be able to be made when RF energy is delivered to a gold rather than platinum tip electrode.
Effect of Beta Adrenergic Receptor Blockade on Cardiac Autonomic Tone in Patients with Chronic Stable Angina
Authors: BURGER ANDREW J. , KAMALESH MASOOR , KUMAR SHYLENDRA , NESTO RICHARD
Published: July 2006

Decreased heart rate variability, which may be due to increased sympathetic and decreased parasympathetic activity, has been shown to be a predictor of cardiac events after acute myocardial infarction. The present study was undertaken to analyze the effect of beta adrenergic blockade on cardiac autonomic system in patients with chronic stable angina. Nineteen patients (15 males and 4 females, age range 44–74 years) with chronic stable angina were enrolled. After stopping all cardiac medications, patients had two baseline treadmill tests with both reproducible angina and ST depression and a baseline 48‐hour ambulatory ECG recording. A long‐acting beta‐blocker (atenolol or betaxolol) was started and titrated to the maximal tolerated dose. After 1–2 months, a repeat 48‐hour ambulatory ECG recording on beta‐blocker therapy was obtained. Heart rate variability analysis was performed on the baseline and drug therapy ECG recordings. The average heart rate significantly decreased (P < 0.008), and the mean RR interval significantly increased (P < 0.0001). In the time‐domain analysis, the standard deviation, variance, ASDNN5, and SDANN5 were not significantly affected, although the PNN50 increased. In the frequency domain, the total power (P < 0.0001) and the low frequency (P < 0.001) components decreased, while the high frequency spectrum was unchanged. Thus, sympathetic activity significantly declined in patients with chronic stable angina on beta‐blocker therapy, while parasympathetic tone demonstrated a heterogenous response.
Ventricular Fibrillation Induction Using Nonsynchronized Low Energy External Shock During Rapid Ventricular Pacing: Method of Induction When Fibrillation Mode of ICD Fails
Authors: SANDERS WILLIAM E. , HAMRICK GEORGE L. , HERBST MARGARET C. , CASCIO WAYNE E. , SIMPSON ROSS J. , WHARTON J. MARCUS
Published: July 2006

Third‐generation implantable cardioverter defibrillators (ICD) are frequently implanted with non‐thoracotomy systems and provide noninvasive methods for electrical stimulation and ventricular fibrillation induction. These modalities facilitate postoperative testing of the ICD. Rapid right ventricular burst pacing via the defibrillator is commonly used for initiation of ventricular tachyarrhythmias. However, with the available third‐generation devices, ventricular fibrillation (VF) induction may be impossible in up to 19% of the patients. In these cases, transvenous placement of a right ventricular catheter has been required to generate VF and appropriately evaluate the device. We report a new technique of noninvasive induction of VF using a low energy external nonsynchronized shock delivered during ICD fibrillation induction pacing. In three patients, after all efforts to induce VF by the Ventritex Cadence V‐100 had failed, a 20 J nonsynchronized shock was delivered during rapid RV pacing. This resulted in VF on the first attempt in all patients. This noninvasive technique of VF initiation may provide a useful clinical approach to ICD testing that eliminates the costs and risks of an invasive procedure.
Salvage of Infected ICDs: Management Without Removal
Authors: LEE JAI H. , GEHA ALEXANDER S. , RATTEHALLI N. MURTHY , CMOLIK BRIAN L. , JOHNSON NANCY J. , BIBLO LEE A. , CARLSON MARK D. , WALDO ALBERT L.
Published: July 2006

During the 7‐year period from August 1986 to December 1993, 242 patients with malignant ventricular arrhythmias underwent 242 ICD implantations and 50 subcutaneous generator changes. Wound infections developed in 5 patients (1.7%): in 3 cases, after primary implantation (3/242 [1,2%]); and in 2 following a generator change (2/50 [4.0%]). This difference was not statistically significant. Infection developed at the generator pocket and became clinically manifest between 6 weeks and 40 months, postoperatively. Our treatment approach with the first patient consisted of simple debridement of the pocket and reimplantation of the existing generator. This led to recurrence, and the generator was safely explanted. In the remaining four patients, our approach has been that of local treatment, with wide debridement of the pocket, and placement of a closed irrigation system with continuous irrigation with a bacitracin, polymyxin, neomycin solution, and culture‐specific antibiotic therapy. We have successfully controlled the infection and salvaged the generator with this approach in all four patients, who are all alive and well at a mean follow‐up of 25.0 ± 17.3 months with no recurrence. The good results obtained in these patients suggest that the concept of total explantation of the infected ICD should be reassessed.
VDD(R) Pacing: Short‐ and Long‐Term Stability of Atrial Sensing with a Single Lead System
Authors: NAEGELI BARBARA , OSSWALD STEFAN , PFISTERER MATTHIAS , BURKART FELIX
Published: July 2006

Background: Recent studies have shown that the atrial signal can reliably be sensed for VDD(R) pacing via atrial floating electrodes incorporated in a single‐pass lead. However, there remains concern about the long‐term stability of atrial sensing and proper VDD function under real‐life conditions. This study investigated the long‐term reliability of atrial sensing and atrioventricular synchronous pacing using a new single lead VDD(R) pacing system. Methods and Results: In 20 consecutive patients (ages 71 ± 14 years) with normal sinus node function and high‐degree heart block, a single lead VDD(R) pacemaker (Unity(tm), Intermedics) was implanted, Atrial sensing was studied at implantation, at discharge, and at 1, 3, 6, 12, and 18 months of follow‐up. At implant, the measured P wave amplitude was 2.3 ± 1.2 mV. By telemetry, the atrial sensing threshold was 0.79 ± 0.41 mV at discharge, 0.75 ± 0.43 mV at 1 month, 0.73 ± 0.43 mV at 3 months, 0.76 ± 0.41 mV at 6 months, 0.79 ± 0.41 mV at 12 months, and 0.77 ± 0.35 mV at 18 months of follow‐up (P = NS). Appropriate VDD pacing was assessed by the percentage of correct atrial synchronization (PAS = atrial triggered ventricular paced complexes ± total number of ventricular paced complexes) during repeated Holters. PAS was 99.99%± 0.01 % at 1 month, 99.99%± 0.02% at 3 months, and 99.98%± 0.05% at 12 months of follow‐up (P = NS). No atrial oversensing with inappropriate ventricular pacing was observed, neither during isometric arm exercise testing nor spontaneously during Holier monitoring. Conclusion: The long‐term stability of atrial sensing with almost 100% correct atrial synchronous tracking and the lack of inappropriate pacing due to atrial oversensing make the new Unity VDD(R) system a highly reliable single lead pacing system. In view of the lower costs and the ease of single lead implantation, this system may offer an interesting alternative to DDD pacemakers in patients with normal sinus node function.
Decreased Heart Rate Variability in Patients with Congestive Heart Failure and Chronotropic Incompetence
Authors: FEI LU , KEELING PHILIP J. , SADOUL NICOLAS , COPIE XAVIER , MALIK MAREK , McKENNA WILLIAM J. , CAMM A. JOHN
Published: July 2006

Heart rate variability was studied in 41 patients (aged 48 ± 12 years) with congestive heart failure secondary to idiopathic dilated cardiomyopathy. All patients underwent a treadmill exercise test and 24‐hour Holter ECC monitoring. Chronotropic incompetence was defined as the failure to achieve > 80% of the predicted maximal heart rate response given by 220 – age (years) at peak exercise. Spectral heart rate variability was analyzed from 24‐hour Holter ECCs and was expressed as total (0.01–1.00 Hz), low (0.04–0.15 Hz), and high (0.15–0.40 Hz) frequency components. The standard deviation of all normal RR intervals (SDNN) was also computed. Chronotropic incompetence was observed in ten patients. Peak oxygen consumption was significantly lower in patients witb chronotropic incompetence compared with those without chronotropic incompetence. The total (5.11 ± 1.26 In [ms2] vs 6.41 ± 0.92 In [ms2]; P = 0.009) and low (3.38 ± 1.65 In [ms2] vs 5.45 ± 1.34 In [ms2];P = 0.003), but not the high (3.42 ± 1.04 In [ms2] vs 4.00 ± 1.12 in [ms2]; P = 0.249) frequency components of heart rate variability were significantly lower in patients with chronotropic incompetence, although there was no significant difference in mean heart rate (88 ± 20 beats/min vs 86 ± 15 beats/min; P = 0.831) or left ventricular ejection fraction (22%± 10% vs 24%± 10%; P = 0.619). SDNN was also significantly lower in patients with chronotropic incompetence compared witb those without chronotropic incompetence (64 ± 34 ms vs 102 ± 37 ms; P = 0.030). Conclusions: The observation that heart rate variability is significantly decreased in patients with congestive heart failure who have chronotropic incompetence suggests that chronotropic incompetence may relate to an abnormal autonomic influence on the heart in these patients.
The Effect of Biphasic Waveform Tilt in Transvenous Atrial Defibrillation
Authors: SRA JASBIR , BREMNER SIOBHAN , KRUM DAVID , DHALA ANWER , BLANCK ZALMEN , DESHPANDE SANJAY , BIEHL MICHAEL , LI HUAGI , JAZAYERI MOHAMMAD R. , AKHTAR MASOOD
Published: July 2006

Atrial defibrillation can be accomplished using low energy shocks and transvenous catheters. The biphasic waveform tilt required to achieve optimal atrial defibrillation thresholds (ADFTs) is, however, not known. The effect of single capacitor biphasic waveform tilt modification on ADFT was assessed in 20 patients. Following AF induction the defibrillation pulses were delivered between the catheters positioned in the coronary sinus and the right atrium.

The single capacitor biphasic waveform shocks, delivered over the same pathways, consisted of 65% tilt (65/65 biphasic waveform) to produce an overall tilt of 88%, or 50% tilt (50/50 biphasic waveform) to produce an overall tilt of 75%. Although 65/65 biphasic waveform delivers more energy, the shorter duration 50/50 biphasic waveform reduced stored energy ADFT 21%, from 1.34 ± 0.82 J with 65/65 biphasic to 2.06 ± 0.81 J. These differences were not statistically significant. Nine patients had lower ADFT with 50/50 biphasic waveform while five patients had lower ADFT with 65/65 biphasic waveform. Equivalent reduction in ADFT was seen in the remaining six patients. The ADFT was 0.83 ± 0.65 J when both tilts were considered. In conclusion, biphasic waveform tilt modification may affect the ADFT in an individual patient. The optimal biphasic waveform for ADFT is not known.
Psychiatric Morbidity and Depressive Symptomatology in Patients with Permanent Pacemakers
Authors: AYDEMIR ÖMER , ÖZMEN EROL , KÜEY LEVENT , KÜLTUR SAVAŞ , YEŞIL MURAT , POSTACI NURSEN , BAYATA SERDAR
Published: July 2006

Implantation of a permanent pacemaker requires a psychological effort on the patient's part for adaptation in the acute term, and chronically, it restricts activities of the patient and may cause some psychiatric disturbances. To investigate psychiatric morbidity and depressive symptomatology of the patients with permanent pacemakers, 84 pacemaker patients were diagnosed using the DSM‐III‐R criteria and depressive symptoms were determined by modified Hamilton Depression Rating Scale (mHDRS). Sixteen (19.1 %) patients had been given a psychiatric diagnosis. The most frequent diagnoses were adjustment disorder (5.9%) and major depressive episode (4.7%). Nine patients (10.7%) were diagnosed as having clinical depression (mHDRS ≥ 17). The mean score of mHDRS was 7.57 ± 7.46, and the severity of depression was significantly higher in females. The most frequent symptoms are difficulties in work and activities (53.6%), psychic anxiety (48.8%), loss of energy (42.9%), and hypochondriasis and insomnia (39.3%). Depressed mood, psychic anxiety, loss of energy, loss of interest, insomnia, and hypochondriasis were significantly more frequent in females. Uneducated patients had a more significant loss of energy than educated patients. Depressed mood, psychic anxiety, and somatic concerns and symptoms were more frequent in patients with permanent pacemakers than in the general population. These symptoms, resembling mixed anxiety‐depression disorder, were related to fears of having a permanent pacemaker, since our series were composed of uneducated patients who did not have enough knowledge about the device.
Use of Serotonin Re‐Uptake Inhibitors as Primary Therapy for Carotid Sinus Hypersensitivity
Authors: DAN DAN , GRUBB BLAIR P. , MOUHAFFEL ASSAD H. , KOSINSKI DANIEL J.
Published: July 2006

Carotid sinus syndrome (CSS) is a well‐recognized cause of unexplained syncope in older patients, and may lead to significant morbidity related to trauma suffered during falls. Dual chamber pacing has been demonstrated to be efficacious in relieving symptoms due to bradycardia, but not the accompanying vasodepressor response. We report three patients with recurrent syncope due to a mixed type of CSS, who were treated with serotonin re‐uptake inhibitors (SSRIs) alone, and were symptom‐free after 4–5 weeks of therapy. The patients have remained symptom‐free after more than 13 months of treatment. We conclude that SSRIs may be potentially useful in the treatment of CSS, and that the central mechanisms involved in CSS may be similar to those that resalt in neurocardiogenic syncope.
Immediate and Short‐Term Reproducibility of the P Wave Signal‐Averaged Electrocardiogram
Authors: EHLERT FREDERICK A. , ZAMAN NAJAMUZ , STEINBERG JONATHAN S.
Published: July 2006

While abnormalities in the P wave SAECG have been associated with the occurrence of AF, its reproducibility has never been documented. The purpose of this study was to evaluate the immediate and short‐term reproducibility of measurements from the P wave SAECG. P wave SAECGs were obtained using well‐described techniques that utilize the QHS complex as the trigger and the P wave as template for averaging. In 28 subjects (8 controls, 11 with cardiac disease, 9 with prior AF), 3 P wave SAECGs were obtained: an initial study; an immediate reacquisition; and reacquisition after 4–5 days. Vector duration and RMS voltage of the terminal 20 ms of the P wave SAECG were measured and compared. The mean P wave duration was 152 ± 14 ms on initial SAECG, 152 ± 14 ms and 152 ± 15 ms at immediate and short‐term reacquisitions, respectively (both P = NS vs initial). The mean terminal BMS voltage was 6.4 ± 6.0 mcV on initial SAECG, 6.4 ± 5.9 mcV and 6.5 ± 5.8 meV at immediate and short‐term reacquisitions, respectively (both P = NS vs initial). Linear regression analysis showed high reproducibility for both P wave duration (r = 0.94 for immediate and r = 0.96 for short‐term reacquisition vs initial) but slightly less for terminal RMS voltage (r = 0.92 for immediate and r = 0.84 for short‐term reacquisition vs initial). In subgroup analysis, P wave duration measurements were highly reproducible in controls, in subjects with cardiac disease, and in those with a history of AF. P wave duration was also reproducible for both males and females, as well as for subjects age > 65 years (r = 0.96 and 0.89 for immediate and short‐term reacquisition, respectively). Terminal RMS voltage measurements were reproducible for controls, but less reproducible in other subgroups. In conclusion, P wave duration measurements on SAEGG are reproducible when evaluated at immediate and short‐term reacquisition regardless of age, sex, cardiac disease, or prior AF. Terminal RMS voltages were less reproducible, especially in patients with cardiac disease and/or prior AF. These findings may explain conflicting observations regarding the clinical utility of terminal P wave measurements.
Spontaneous Accelerated Junctional Rhythm: An Unusual but Useful Observation Prior to Radiofrequency Catheter Ablation for Atrioventricular Node Reentrant Tachycardia in Young Patients
Authors: EPSTEIN MICHAEL R. , SAUL J. PHILIP , FISHBERGER STEVEN B. , TRIEDMAN JOHN K. , WALSH EDWARD P.
Published: July 2006

Between May 1990 and March 1995, 5 of 29 young patients (ages 4.2–25 years; median 14.1 years) undergoing RF ablation for atrioventricular node reentrant tachycardia (AVNRT) presented with spontaneous accelerated junctional rhythm (AJR) (CL = 500–750 ms), compared to 0 of 58 age matched controls undergoing RF ablation for a concealed AV accessory pathway (P = 0.004). In 3 of the 5 patients with AVNRT and AJR, junctional beats served as a trigger for reentry. During attempted slow pathway modification in the five patients with AVNRT and AJR, AVNRT continued to be inducible until the AJR was entirely eliminated or dramatically slowed. These 5 patients are tachycardia‐free in followup (median 15 months; range 6–31 months) with only 1 of the 5 patients continuing to experience episodic AJR at rates slower than observed preablation. Episodic spontaneous AJR is statistically associated with AVNRT in young patients and can serve as a trigger for reentry. Successful modification of slow pathway conduction may be predicted by the elimination of AJR or its modulation to slower rates, suggesting that the rhythm is secondary to enhanced automaticity arising near or within the slow pathway.
A Patch in the Pectoral Position Lowers Defibrillation Threshold
Authors: KARASIK PAMELA , SOLOMON ALLEN , VERDINO RALPH , MOORE HANS , RODAK DAVID , HANNAN ROBERT , FLETCHER ROSS
Published: July 2006

Implantable pacemaker cardioverter defibrillators are now available with biphasic waveforms, which have been shown to markedly improve defibrillation thresholds (DFTs). However, in a number of patients the DFT remains high. Also, DFT may increase after implantation, especially if antiarrhythmic drugs are added. We report on the use of a subcutaneous patch in the pectoral position in 15 patients receiving a transvenous defibrillator as a method of easily reducing the DFT. A 660‐mm2 patch electrode was placed beneath the generator in a pocket created on the pectoral fascia. The energy required for defibrillation was lowered by 56% on average, and the system impedance was lowered by a mean of 25%. This maneuver allowed all patients to undergo a successful implant with adequate safety margin.
Dual Device Therapy in the Setting of Changing ICD Technology: Device‐Device Interaction Revisited
Authors: SHEAHAN RICHARD G. , DORIAN PAUL , POLUDNIKIEWICZ MARY , NEWMAN DAVID
Published: July 2006

This case report concerns an adverse device‐device interaction between a replacement ICD and a dual chamber rate responsive pacemaker. It was observed that subtle changes in the design of sensing circuits between an older first‐generation ICD and the newer third‐generation ICD device led to unexpected and dramatic changes in the interactive behavior of a dual device system. The new ICD was connected to chronically implanted hardware. The sensing behavior of the newer ICD included a shorter time constant in the decay of the automatic gain control function, resulting in triple sensing of both the atrial and ventricular paced stimuli and the evoked QRS complex. Physicians should be aware of new design changes in the future so as to anticipate such interactions. In the setting of rapidly changing technology, extra caution must be exercised when choosing to implant two devices in the same patient.
Computation Modes of Multivariate Positive Predictive Characteristics
Authors: MALIK MAREK , CHURCH TIMOTHY R.
Published: July 2006

Multivariate receiver operator characteristics (ROCs) and positive predictive characteristics (PPCs), based on a combination of two or more clinical variables, are usually computed by varying dichotomy limits for each variable independently. This approach has a similar number of degrees of freedom (i.e., uses the same number of programmable parameters) as the approach which defines test positive cases based on a linear combination of all the clinical variables involved. Either approach can be implemented without any assumption about the underlying probability distributions by using an exhaustive computer search. Both approaches were compared in a demonstration study of predicting 2‐year all‐cause mortality after acute myocardial infarction, based on applying various time‐ and spectral‐domain indices of signal‐averaged ECGs from a research survey. The results showed that the optimum mode for the computation ofROCs and PPCs depends on the character of the particular data used. Therefore, in order to increase the precision of the retrospective multifactoral studies, both approaches to ROC and FPC computation should be used and compared in each individual investigation.
Right Ventricular Radiofrequency Ablation of Ventricular Tachycardia After Myocardial Infarction
Authors: MENZ VOLKER , DUTHINH VUONG , CALLANS DAVID J. , SCHWARTZMAN DAVID , GOTTLIEB CHARLES D. , MARCHLINSKI FRANCIS E.
Published: July 2006

Radiofrequency transcatheter ablation of ventricular tachycardia in the setting of a prior myocardial infarction is typically performed with application of energy to the left ventricular endocardium. In this article, two cases are described in which successful radiofrequency transcatheter ablation of ventricular tachycardia occurred with energy delivery to the right ventricular septum after failed ablation attempts from the left ventricle. Both patients had tachycardias with a left bundle branch block morphology and markedly presystolic activity recorded from the right ventricular septum. Right ventricular septal activation mapping during ventricular tachycardia should be performed in patients with left bundle branch block tachycardia morphology and coronary artery disease to maximize efficacy of the catheter ablation procedure.
Unusual Placement of a Pacemaker Pocket
Authors: MAZZETTI HECTOR ALFREDO , TENTORI MARIA CRISTINA
Published: July 2006

Because of infection and extensive radiation injury to the skin of the chest wall, a dual chamber pacemaker was implanted deep to the clavicle. The wound has been stable and comfortable for 1 year and pacemaker programming has been unimpaired.
Comparison of Sensitivity and Specificity of Tilt Protocols with and without Isoproterenol in Children with Unexplained Syncope
Authors: ALEHAN DURSUN , LENK MUSTAFA , ÖZME ŞENCAN , ÇELIKER. ALPAY , ÖZER SEMA
Published: July 2006

Head‐up tilt testing with or without isoproterenol is extensively used in the evaluation of patients with unexplained syncope. However, sensitivity and specificity of tilt protocols with and without isoproterenol have not been clarified in children, due to lack of age matched control subjects. This study was designed to assess and to compare the sensitivity and specificity of tilting alone and tilting in conjunction with isoproterenol. Thirty children with unexplained syncope (group I) and 15 age‐matched control subjects (control group I) underwent successive 60° head‐up tilts for 10 minutes during infusions of 0.02, 0.04, and 0.06 μg/kg/min of isoproterenol, after a baseline tilt to 60° for 25 minutes. Also, 35 children (group II) with unexplained syncope and 15 healthy control subjects (control group II) were evaluated by head‐up tilt to 60° for 45 minutes without an infusion of isoproterenol. In response to tilt protocol with graded isoproterenol, 23 (76.6%) of the patients in group I and 2 of the 25 (13.3%) control subjects developed syncope. Accordingly, the sensitivity of tilt testing with isoproterenol was 76.6%, and its specificity was 86.7%. Tilt testing without isoproterenol was positive in 17 (48.5%) of the patients in group II but in only 1 of the 15 (6.6%) control subjects. Thus, sensitivity and specificity of tilt testing without isoproterenol were 48.5% and 93.4%, respectively. The mean heart rate and systolic blood pressure decreased significantly (P < 0.001) in all tilt positive patients during syncope. In conclusion, the head‐up tilt test is a valuable diagnostic test in the evaluation of children with unexplained syncope, and isoproterenol is likely to increase the sensitivity of the test without decreasing its specificity.
Comparison of Electrical Characteristics Between a Steroid‐Eluting Single‐Pass VDD Lead and a Standard Steroid‐Eluting Ventricular Lead
Authors: SCHUCHERT ANDREAS , VAN LANGEN HERMAN , MICHELS KOEN , MEINERTZ THOMAS ,   on behalf of the THERA PACEMAKER STUDY GROUP
Published: July 2006

Compared to regular ventricular leads, single‐pass VDD leads have two additional floating electrodes proximal to the ventricular tip, which enables them to detect atrial signals. Because of the latter, VDD leads are thicker than ventricular leads, which could affect ventricular pacing. The purpose of the present study was to compare ventricular pacing of a steroid‐eluting single‐pass VDD lead (CapSure VDD, Medtronic; n = 107) with the same steroid‐eluting regular lead (CapSure SP, Medtronic; n = 39) implanted in the ventricle; both leads were connected to the same types of pacemakers. At implantation, pacing thresholds were measured at 0.5‐ms pulse duration and impedance by means with the PSA. At discharge, as well as after 1 and 3 months, pulse duration thresholds were determined at 2.5 V pulse amplitude and impedance by telemetry. At implantation, pacing thresholds and impedance were not different in the VDD (0.38 ± 0.16 V; 691 ± 122 Ω) and ventricular lead group (0.44 ± 0.17 V; 648 ± 150 Ω). During follow‐ups, no differences in pulse duration threshold were detected between the two groups neither at discharge (VDD = 0.05 ± 0.03 ms; ventricular 0.05 ± 0.02 ms), nor after 1 (VDD = 0.05 ± 0.02 ms; ventricular 0.08 ± 0.07 ms) and 3 months (VDD = 0.06 ± 0.03 ms; ventricular 0.09 ± 0.10 ms). There were also no significant differences for impedance at discharge (VDD = 675 ± 113 Ω; ventricular = 594 ± 113 Ω), after 1 (VDD = 678 ± 131 Ω,; ventricular = 627 ± 112 Ω) and 3 months (VDD = 652 ± 99 Ω; ventricular = 628 ± 105 Ω). Pacing thresholds and impedance were neither significantly different at implantation nor during follow‐ups between patients with steroid‐eluting VDD leads and patients with an equivalent ventricular lead indicating that the thicker VDD lead does not affect ventricular pacing.
Mode Switching Anomalies: A Patient Who Remained Symptomatic During Paroxysmal Atrial Tachyarrhythmias Despite A Mode Switching Pacemaker
Authors: GIUDICI MICHAEL C. , ORIAS DAVID W.
Published: July 2006

A patient with an automatic mode switching pacemaker continued to experience discomfort during the onset of paroxysmal supraventricular tachyarrhythmias. Investigation revealed that the patient was sensing abrupt rate changes as the ventricular paced rate tracked the tachycardia during onset and detection phases. Her pacemaker was replaced with a new device with both mode switching and rate smoothing capabilities with resultant elimination of symptoms.
Longitudinal Dissociation in the His Bundle: A Possible Mechanism of Two Distinct Cycle Lengths in Atrioventricular Reentrant Tachycardia
Authors: AKIYAMA JUNICHI , AONUMA KAZUTAKA , OGAHARA SHIGEKO , OKAMOTO YOSHIHIRO , UMEZAWA SHIGEO , INADA MIHOE , KORENAGA MASAYOSHI , NOGAMI AKIHIKO , HIROE MICHIAKI , MARUMO FUMIAKI , IESAKA YOSHITO
Published: July 2006

Two wide QRS tachycardias with identical morphology but different cycle lengths (CLs) developed in a 63‐year‐old man. Electrophysiological study demonstrated inducible atrioventricular reentrant tachycardia (AVRT) due to a concealed left posterior accessory pathway (AP), which was successfully ablated by radiofrequency application. Neither dual AV nodal pathways nor other APs were documented. Splitting of the His‐bundle electrogram was shown, and programmed stimulation induced sudden prolongation of intra‐hisian conduction time. These results suggest longitudinal dissociation in the His bundle may be responsible for two distinct CLs in AVRT without dualAV nodal physiology.
Ion Channels, the QT Interval, and Arrhythmias
Authors: WILDE ARTHUR A.M. , VELDKAMP MARIEKE W.
Published: July 2006

Aberrations in genes encoding for ion channels have been shown to underlie a number of cardiac arrhythmia syndromes, hitherto classified as idiopathic. These aberrations, inherited and congenital, may lead to dysfunction of channels with resultant abnormal current characteristics. In addition, a variety of stimuli may cause altered expression of these genes. Because prolongation of the action potential (and the QT‐interval) is often the result, patients are at risk for the occurrence of arrhythmias based on reentry and the development of abnormal impulse initiation. Molecular dissection of the inherited syndromes hus led to rapid progress in our understanding of basic knowledge about ion channel function and its relation to channel structure. This progress is undoubtly of benefit for the understanding of the repolarization changes in more common conditions and will become of benefit to many more patients who suffer from therapy resistant arrhythmias.
Molecular Biology of the Long QT Syndrome: Impact on Management
Authors: PRIORI SILVIA G. , NAPOLITANO CARLO , PAGANINI VINCENZO , CANTÙ FRANCESCO , SCHWARTZ PETER J
Published: July 2006

The long QT syndrome (LQTS) is a familial disease characterized by prolonged ventricular repolarization and high incidence of malignant ventricular tachyarrhythmias often occurring in conditions ofadrenergic activation. Recently, the genes for the LQTS linked to chromosomes 3 (LQT3), 7 (LQT2), and 11 (LQTl) were identified as SCN5A, the cardiac sodium channel gene and as HERG and KvLQTl potassium channel genes. These discoveries have paved the way for the development of gene‐specific therapy for these three forms of LQTS. In order to test specific interventions potentially beneficial in the molecular variants of LQTS, we developed a cellular model to mimic the electrophysiological abnormalities of LQT3 and LQT2. Isolated guinea pig ventricular myocytes were exposed to anthopleurin and dofetilide in order to mimic LQT3 and LQT2, respectively. This model has been used to study the effect of sodium channel blockade and of rapid pacing showing a pronounced action potential shortening in response to Na+channel blockade with mexiletine and during rapid pacing only in anthopleurin‐treated cells but not in dofetilide‐treated cells. Based on these results we tested the hypothesis that QT interval would shorten more in LQT3 patients in response to mexiletine and to increases in heart rate. Mexiletine shortened significantly the QT interval among LQT3 patients but not among LQT2 patients. LQT3 patients shortened their QT interval in response to increases in heart rate much more than LQT2 patients and healthy controls. These findings suggest thatLQT3 patients are more likely to benefit from Na+ channel blockers and from cardiac pacing because they are at higher arrhythmic risk at slow heart rates. Conversely, LQT2 patients are at higher risk to develop syncope under stressful conditions, because of the combined arrhythmogenic effect of cate‐cholamines with the insufficient adaptation of their QT interval. Along the same line of development of gene‐specific therapy, recent data demonstrated that an increase in the extracellular concentration of potassium shortens the QT interval in LQT2 patients suggesting that intervention aimed at increasing potassium plasma levels may represent a specific treatment for LQT2. The molecular findings on LQTS suggest the possibility of developing therapeutic interventions targeted to specific genetic defects. Until definitive data become available, antiadrenergic therapy remains the mainstay in the management of LQTS patients, however it may be soon worth considering the addition of a Na + channel blocker such as mexiletine for LQT3 patients and of interventions such as K+ channel openers or increases in the extracellular concentration of potassium for LQTl and LQT2 patients.
Clinical Management of Patients with the Long QT Syndrome: Drugs, Devices, and Gene‐Specific Therapy
Authors: MOSS ARTHUR J.
Published: July 2006

The familial long QT syndrome (LQTS) is now recognized as a genetic cbannelopatby with a propensity to arrhythmogenic syncope and sudden death. Three genetic mutations have been identified that involve the slow and fast delayed potassium rectifier currents and the sodium current. Distinctive ECG T wave phenotypes are associated with each of the tbree genotypes. Current day therapy includes: β‐adrenergic blocking drugs; pacemakers; left cervicothoracic sympathetic ganglionectomy; implanted cardioverter defibrillators; and possibly, drugs that improve mutant ionic cbannel dysfunction. LQTS bas provided unique insight into the complex relationsbip between ionic cbannel dysfunction and ventricular tacbyarrbytbmias.
Ventricular Tachycardia in Neonates
Authors: PERRY JAMES C.
Published: July 2006

Infant VT can be a devastating arrhythmia, with high mortality for those presenting with myocarditis, long QT syndrome, or cardiovascular collapse with rapid VT due to tumors. While management of these patients can be challenging and discouraging, other infants with wide QRS rhythms tend to follow a more benign course. These latter patients have accelerated idio‐pathic ventricular rhythm or aberrant forms of infant supraventricular tachycardia. Distinguishing these forms of wide QRS tachycardia from the more lethal forms is paramount to institution of appropriate therapies.
Polymorphous Ventricular Tachyarrhythmias in the Absence of Structural Heart Disease
Authors: COUMEL PHILIPPE
Published: July 2006

Polymorphous ventricular tachyarrhythmias (PVTA) in the absence of structural heart disease form a particularly important target for comprehensive research. They occur in young, healthy children and young adults and most probably cover several underlying electrophysiological abnormalities. We individualized two syndromes, namely catecholaminergic ventricular tachyarrhythmias, and torsade de pointes (TDP) with a short coupling interval, but these two entities certainly represent only a part of the problem of id‐iopathic ventricular fibrillation. Having the implanted defibrillator as a therapeutic umbrella for those patients who were fortunate enough to escape from sudden death is not sufficient. Too often in modern cardiology the therapeutic achievements tend to precede the process of diagnosis and comprehension. At least, the former should not preclude the latter, a situation that can be observed, for instance, when the favorable effect of a drug is evidenced before its mode of action was understood. At best, both progress together, provided we pay attention to adequately exploit the resources of modern technology.
Radiofrequency Ablation of Accessory Pathways Associated with Congenital Heart Disease
Authors: VAN HARE GEORGE F.
Published: July 2006

The coexistence of significant congenital cardiac disease with accessory pathways is not uncommon, and presents a number of issues for clinical management. These issues include the propensity of such patients to have poorly tolerated tachycardia; the difficulties in choosing appropriate medical management given potential problems with preexisting sinus node disease, poor contractility, and the possibility of proarrhythmia; the need to seriously consider ablation prior to, or at the time of, intracar‐diac repair of congenital cardiac defects; and finally, the difficulties that complex anatomy may pose to the interventional electrophysiologist. Definitive management requires expertise both in electrophysiology and in pediatric cardiology. Success can usually be achieved with a careful, anatomically precise approach, combined with imagination and persistence. Because of the difficulties with medical management, catheter ablation may be the most attractive modality for control of accessory pathway tachycardia in this patient population.
The Asymptomatic Patient with the Wolff‐Parkinson‐White Electrocardiogram
Authors: WELLENS HEIN J. , RODRIGUEZ LUZ MARIA , TIMMERMANS CARL , SMEETS JOEP L.
Published: July 2006

Sudden death can be the first manifestation of the Wolff‐Parkinson‐White (WPW) syndrome. The underlying mechanism being atrial fibrillation with a very high ventricular rate, because of a short anterograde refractory period of the accessory atrioventricular pathway (AP), deteriorating into ventricular fibrillation. Information on the anterograde refractory period of the AP is therefore important to recognize asymptomatic people with the WPW ECG at risk for dying suddenly. Several noninvasive tests are available to identify the low risk patient. Decision making when to interrupt the AP in asymptomatic WPW patients not at low risk requires an invasive study to document the electrophysiological properties of the AP and to determine its exact location.
Natural History of Congenital Complete Atrioventricular Block
Authors: MICHAELSSON MAGNUS , RIESENFELD TOMAS , JONZON ANDERS
Published: July 2006

An update of studies onthena tural history of congenital complete A V block is presented. A risk for heart failure, syn ‐cope, and sudden death is present at any age including fetal life. Unfavorable prognostic signs in utero are low and decreasing ventricular rate (VR), hydrops, AV valve regurgitation, and low aortic flow velocity. Indications for pacing in infancy are congestive heart failure, ventricular rate < 55 beats/min in isolated block and < 65 beats/min with associated disease, prolonged QTc, syncope attacks, frequent ventricular ectopic beats, and alternating ventricular pacemakers. Indications for immediate pacing in childhood and adult life are syncope, presyncope, VR rates lower than median for age, periods ofjunc‐tional exit block, prolongation of QTc and mitral regurgitation, and change of ventricular pacemaker. Pacing is recommended to all patients older than 15 years.
Radiofrequency Ablation of Intraatrial Reentrant Tachycardia after Surgery for Congenital Heart Disease
Authors: SAUL J. PHILIP , TRIEDMAN JOHN K.
Published: July 2006

Intraatrial reentry tachycardia is a common cause of both morbidity and mortality after surgery for a variety of congenital heart defects. Despite an armamentarium of arrhythmia management tools, including drug therapy, antibradycardia, and antitachycardia pacing, and catheter ablation, management of these arrhythmias remains a challenge. This report briefly reviews the problem, assesses the current successes and failures of radiofrequency catheter ablation for treating it, and discusses a number of ongoing developments that may improve both early and late outcome.
Antitachycardia Pacing
Authors: GILLETTE PAUL C.
Published: July 2006

Patients who have attempted repair of congenital heart disease often develop bradycardia and tachycardias postoperatively. The two dysrhythmias each make treatment of the other more difficult. Pacing is the only modality that addresses both brady‐ and tachycardias, without adversely influencing the other. Most postoperative tachycardias are reentrant, and thus uniquely susceptible to overdrive pacing. Usually an atrial single lead system is used. The patients most commonly encountered are those with extensive atrial surgery, such as atrial septal defect [ASD] repair. Mustard and Senning repair of d‐transposition, and the various types of Fontan operations. The results are excellent for ASD repair and postoperative transposition, but only fair for postoperative Fontan patients.
Clinical Evaluation of a Thin Bipolar Pacing Lead
Authors: BREIVIK KJELL , DANILOVIC DEJAN , OHM OLE‐JØRGEN , GUEROLA MODESTO , STERTMAN WILHELM ALFRED , SUNTINGER ANTON
Published: July 2006

The main disadvantages of bipolar pacing leads have traditionally been related to their relative thickness and stiffness compared to unipolar leads. In a new “drawn filled tube” plus “coated wire” technology, each conductor strand is composed of MP35N tubing filled with silver core and coated with a thin ETFE polymer insulation material. This and parallel winding of single anode and cathode conductors into a single bifilar coil resulted in a bipolar lead (ThinLine, Intermedics) with a body diameter and flexibility similar to unipolar leads. The lead is tined. polyurethane. with the cathode and the anode made of iridium‐oxide‐coated titanium (IROX). The slotted 8‐mm2 cathode tip is coated with polyethylene glycol. a blood soluble material. We present the clinical evaluation results from four pacemaker clinics, where 47 leads (23 atrial‐J model 432–04 and 24 ventricular model 430–10) were implanted in 25 patients and followed for up to 2 years. The lead handling characteristics were found to be very satisfactory. Electrical parameters of the leads were measured at implant and noninvasively on postoperative days 1, 2, 21, 42. and months 3, 6, 12, and 24. Mean chronic pulse width thresholds at 2.5 V were 0.14 ± 0.05 ms in the atrium and 0.10 ± 0.02 ms in the ventricle, pacing impedances 443 ± 104 Ω and 520 ± 241 Ω. while median electrogram amplitudes were ≥ 3.5 mV and ≥ 7 m V, respectively. Pacing impedances and thresholds were found to be slightly but statistically significantly higher in unipolar than in bipolar configuration—the findings are explainable bv the lead construction. One of 47 leads failed 3 weeks after implant; the conductors were short circuited due to an error during the manufacturing process. We conclude that the new lead thus far has demonstrated appropriate mechanical and electrical characteristics.
Slow AV Nodal Pathway Ablation Utilizing a Unique Temperature Controlled Radiofrequency Energy System
Authors: EPSTEIN LAURENCE M. , JUNG SAMUEL , LEE RANDALL J. , LESH MICHAEL D. , EISENBERG SUSAN J. , SCHEINMAN MELVIN M. , FITZPATRICK ADAM P.
Published: July 2006

Thirty‐nine consecutive patients with symptomatic AV nodal reentrant tachycardia (AVNRT) underwent temperature guided slow AV nodal pathway ablation (group 1). Forty‐three consecutive patients undergoing nontemperature guided slow AV nodal pathway ablation late in our experience compose the control population (group 2). Slow pathway ablation was achieved in all patients of both groups. The mean fluoroscopy and ablation times for group 1 were significantly shorter than for group 2 (26.1 ± 14.9 vs 33.9 ± 18.9 min, P < 0.05; 19.9 ± 12.1 vs 30.9 ± 23.3 min, P ≤ 0.02). There were no episodes of coagulum formation in group 1, while there were 15 episodes (7.1 % of energy applications) in group 2 (P = 0.0006) despite a significantly higher applied power in group 1 (53.4 ± 25.1 vs 35.6 ± 9.5W, P = 0.0001). Successful energy applications were associated with significantly higher temperatures than unsuccessful applications in group 1 (55.6 ± 5.8 C vs. 52.9 ± 6.8 C, P ≤ 0.03). The minimum temperature required for successful ablation was 48 C for two patients (5%) and was > 50 C for the remainder of patients (37/39 [95%]). The catheter ablation system used in this study was safe, effective, and prevented coagulum formation while delivering relatively high power. In addition, shorter ablation times and radiation exposure were seen with this system. Although successful energy applications and the production of junctional rhythm were associated with higher achieved temperatures, temperature alone did not predict either endpoint. Future prospective, randomized trials are needed to confirm these findings and further evaluate the value of temperature monitoring.
Pacemaker Induced Mitral Regurgitation: An Alternative Form of Pacemaker Syndrome
Authors: CANNAN CHARLES R. , HIGANO STUART T. , Jr. HOLMES DAVID R.
Published: July 2006

A patient in atrial fibrillation was referred for mitral valve replacement due to severe mitral regurgitation. A cardiac pacemaker had previously been implanted. Cardiac catheterization demonstrated large V waves in the wedge pressure tracing during ventricular pacing, which were not present during native conduction. A left ventriculogram demonstrated severe mitral regurgitation during ventricular pacing, but not during native conduction. This patient, in atrial fibrillation, had severe mitral regurgitation induced by ventricular pacing and not by native conduction. Pacemaker syndrome may be caused by mitral regurgitation that is probably not secondary to AV dissociation, but rather the result of dyssyn‐chronous ventricular contraction.
Adenosine Induced Polymorphic Ventricular Tachycardia in Adults Without Structural Heart Disease
Authors: SMITH JEFFREY R. , GOLDBERGER JEFFREY J. , KADISH ALAN H.
Published: July 2006

Adenosine has been reported to cause polymorphic VT in patients with congenital or acquired prolonged QT intervals and to cause pause dependent VT in a patient with a normal QT interval. There have been no previous reports of adenosine causing nonpause dependent polymorphic VT in patients without structural heart disease. We report two patients, with normal hearts and normal QT intervals, who developed nonsustained polymorphic VTthat was not pause dependent. Adenosine induced polymorphic VT does not appear to be a marker of the long QT syndrome, but may be an uncommon yet not unexpected pharmacological response to drug administration.
Neural Circulatory Control in Vasovagal Syncope
Authors: VAN LIESHOUT JOHANNES J. , WIELING WOUTER , KAREMAKER JOHN M.
Published: July 2006

The orthostatic volume displacement associated with the upright position necessitates effective neural cardiovascular modulation. Neural control of cardiac chronograpy and inotropy, and vasomotor tone aims at maintaining venous return, thus opposing gravitational pooling of blood in the lower part of the body. The present concept of the vasovagal response or “common faint” implicates the development of inappropriate cardiac slowing due to sudden augmentation of efferent vagal activity, and arteriolar dilatation by sudden reduction or cessation of sympathetic activity. The venous pooling associated with lasting orthostatic stress results in development of central hypovolemia. At a certain point during the ongoing reflex adaptation to the hypovolemia in progress, a depressor reflex is set in train. The depressor reflex input along this second “peripheral” afferent pathway is postulated to originate from various sites in the cardiovascular system but remains uncertain. The common faint in humans is of both vaso‐ and vagal origin; the pure vagal response is less common than its vasodepressor variant. There is strong evidence for an early loss of vasomotor tone in the majority of fainting subjects. Blocking the vagus nerve or cardiac pacing is not of much help in preventing vasovagal syncope; though atropine or pacing may prevent bradycardia in vasovagal fainting, they have never been proven to prevent hypotension. Baroreflex modulation of autonomic outflow remains present during the presyncopal stages until it becomes offset by an opposing depressor reflex with relative bradycardia and relaxation of arterial resistance vessels. The nature of the vasodilatation associated with the vasovagal response has still not been settled.