bluuebunny/crossref_metadata_2025 huggingface dataset:
Repolarization Aiternans: Techniques, Mechanisms, and Cardiac Vulnerability
Authors: MURDA'H MUSTAFA A. , MCKENNA W. J. , CAMM A. JOHN
Published: July 2006

Sudden cardiac death continues to be the leading cause of mortality in developed countries. Electrical alternans of the ST segment and the T wave on the surface ECG as a noninvasive marker of patients at risk is a phenomenon that was initially observed early in this century and was seen then to be associated with cardiac rhythm disturbances. Substantial evidence indicates that T wave aiternans (TWA) is related to myocardiai ischemic as a harbinger of malignant ventricular arrhythmias because it reflects dispersion and heterogeneity of repolarization. Recent data have demonstrated a significant correlation between TWA and vulnerability to ventricular arrhythmias in individuals with or without organic heart disease, it also predicts the results of eiectrophysioiogicai testing and arrhythmia‐free survival in patients with a variety of cardiac diseases. This article reviews the historical background of TWA and discusses the early experimental and recent clinical evidence implying an integral link between TWA and ischemia‐induced cardiac vulnerability.
Ventricular Arrhythmias in Dilated Cardiomyopathy
Authors: BRACHMANN JOHANNES , HILBEL THOMAS , GRÜJNIG EKKEHARD , BENZ ANDREAS , HAASS MARKUS , KÜBLER WOLFGANG
Published: July 2006

Although prognosis of dilated cardiomyopathy (DCM) has improved due to advances in diagnosis and therapy, still too many sudden cardiac deaths occur in DCM. Spontaneous ventricular ectopy is a very common finding in patients with DCM, but the prognostic significance of Holter monitoring remains controversial. Other noninvasive methods, e.g., late potentials and QT dispersion, have not yet contributed to the evaluation of prognosis for arrhythmogenic events in DCM. Programmed ventricular stimulation has been repeatedly used to stratify long‐term prognosis, yet satisfactory data are still missing as many deaths occur in patients without inducible arrhythmias. Several prognostic studies are still in progess, and preliminary data for the use of ICDs already appear to be promising. In patients with poor left ventricular function and ICDs in situ, prognosis is determined by progression of heart failure. Heart transplantation may be the ultimate therapeutic instrument for end‐stage heart failure patients. For patients with advanced DCM and increased risk for malignant arrhythmias who are unsuitable for orthotopic heart transplantation, the combined therapy with an ICD and dynamic cardiomyoplasty may be an alternative treatment.
An Approach to the Detection of Autonomic Neuropathy hy Use of Signal‐Averaged Electrocardiography
Authors: YAMADA TAKAHISA , FUKUNAMI MASATAKE , OHMORI MASAHARU , KUMAGAI KAZUAKI , ABE YASUSHI , NISHIKAWA NAGAHIRO , HORI MASATSUGU , KAMADA TAKENOBU , HOKI NORITAKE
Published: July 2006

The beat‐to‐beat variation of PR interval, which is thought to be a reflection of autonomic nervous system, is difficult to measure with accuracy because the variation is too subtle. However, R wave amplitude in the P wave triggered SAECG is easily attenuated in comparison to that in the R wave triggered SAECG, which might he due to PR interval fluctuation. To determine whether autonomic neuropathy could be detected by use of SAECG, two types of SAECGs triggered by P and R waves were recorded in 23 diabetics with autonomic neuropathy and 41 age matched controls. The peak voltage of filtered QRS complex was measured in the R wave and P wave triggered SAECGs. Percent attenuation of the filtered QRS voltage was calculated by dividing the difference between the voltages in the R wave and P wave triggered SAECGs by the voltage in R wave triggered SAECG. The percent attenuation of filtered QRS voltage was significantly smaller in diabetics with autonomic neuropathy than controls (4.6%± 4.9% vs 16.3%± 15.0%; P < 0.001). These results suggest that the degree of attenuation of filtered QRS voltage in the P wave triggered SAECG would be useful for the detection of autonomic neuropathy.
Failure of Automatic Mode Switching: Recognition and Management
Authors: ELLENBOGEN KENNETH A. , MOND HARRY G. , WOOD MARK A. , BAROLD SERGE S.
Published: July 2006

Dual chamher pacing is desirable to optimize AV synchrony and to potentially decrease the incidence of supraventricular tachyarrhythimas. Patients with alternating periods of both supraventricular tachyarrhythmias and bradycardia pose a difficult challenge when standard dual chamber pacemakers are implanted. The automatic mode switching algorithm was introduced to prevent tracking of paroxysmal supraventricular tachyarrhythimas and avoid the adverse hemodynamic and symptomatic consequences of a rapid ventricular response. In some cases, failure to mode switch may take place when the atrial signal during tachycardia is of insufficient amplitude to be sensed. Failure to mode switch way also occur when the atrial signal periodically occurs in the atrial blanking period(s). In this article, we describe failure to mode switch in seven patients with paroxysmal supraventricular tachyarrhythmias after a Telectronics Meta DDDR 1254 device was implanted. Each patient had paroxysmal atrial flutter and/or atrial fibrillation and presented with either repetitive episodes of oscillation between atrial tracking and mode switching to a nonatrial tracking pacing mode or complete failure to mode switch. Six of seven patients were taking antiarrhythmic drugs that resulted in slowing of the atrial cycle length. Pacemaker reprogramming was required in each case to restore reliable mode switching during subsequent recurrences of the atrial tachyarrhythmias. We conclude that careful pacemaker programming of patients with paroxysmal atrial flutter and the Telectronics Meta DDDR 1254 is necessary when patients are taking an antiarrhythmic drug that slows atrial cycle length.
Is There an Optimal Electrode Pad Size to Maximize Intracardiac Current in Transthoracic Defibrillation?
Authors: PAGAN‐CARLO LUIS A. , BIRKETT CLAYTON L. , SMITH ROBIN A. , KERBER RICHARD E.
Published: July 2006

Achieving defibrillation depends on adequate intracardiac current. The purpose of this study was to determine, in advance of administering shocks, which parameters of body habitus can be used to select the electrode size that maximizes intracardiac current in transthoracic defibrillation. We administered direct current shocks to 18 mongrel dogs over a wide range of weight and size (weight 10–30 kg with chest circumferences 44–77 cm) using a damped sine wave defibrillator and self‐adhesive electrode pairs of various diameters (4 cm, 5.8 cm, 8 cm, and 10 cm), placed on the right and left lateral chest walls. The energy levels used were 50, 100, and 150 J. Intracardiac voltage gradient, a parameter of intracardiac current, was determined in three orthogonal planes using an intramyocardial electrode array placed in the interventricular septum. The relation between intracardiac voltage gradient magnitude [VG] and various parameters (body weight, heart weight, chest circumference, chest volume, chest radius, and heart weight divided by chest radius) was determined. The correlation (r) with the smallest P value was between [Va] and the heart weight divided by chest radius (HW/R) (r = ‐0.71). Intracardiac current was highest at intermediate pad sizes. The electrode pads that maximized [VG] tended to be large for the larger HW/R dogs, and smaller for the smaller HW/R dogs. In none of the HW/R groups did the largest electrode pads yield the highest intracardiac voltage gradient. We conclude that there is no simple way to determine in advance an electrode pad size that maximizes intracardiac current. The HW/R ratio influences but does not determine intracardiac current.
The Effect of Polarity of the Initial Phase of a Biphasic Shock Waveform on the Defibrillation Threshold of Pectorally Implanted Defibrillators
Authors: KEELAN EDWARD T. , SRA JASBIR S. , AXTELL KATHI , MAGLIO CHERYL , UNDERWOOD R. DENT , DESPHANDE SANJAY , BIEHL MICHAEL , DHALA ANWER , BLANCK ZALMEN , JAZAYERI MOHAMMAD R. , AKHTAR MASOOD
Published: July 2006

The effect of initial phase polarity on the DFT of two pectorally implanted biphasic ICDs was tested in a randomized, prospective manner at the time of implantation. Twenty‐two consecutive patients with VT or VF who received either the Medtronic PCD 7219C fewel device (10 patients) or PCD 7219D fewel device (12 patients) were studied. DFT testing was performed in a standard step‐down manner. Both initial phase polarities—initial defibrillation current flowing from active can/SVC coil (± subcutaneous patch) to the RV coil (RV‐) or from RV coil to active can/SVC coil (RV+)—were tested in random order. The mean DFT achieved with RV+ compared with RV‐ was lower for the 7219C patient group (6.6 ±3.1 vs 10.8 ± 5.5 J; P = 0.007). A similar trend was observed forthe 7219D group, though the difference did not reach statistical significance (12.0 ± 4.0 vs 16.3 ± 7.3 J; P = 0.07). Seven of the 10 patients in the 7219C group had a lower DFT with RV+, while the initial phase polarity made no difference in 3. In the 7219D group, 7 patients had a lower DFT using RV+, 2 patients had a lower DFT using RV‐, and the initial phase polarity made no difference in 3. In conclusion, this study demonstrates that changing the polarity of the initial phase of a biphasic shock wave form can have a significant impact on the DFT achieved at the time of ICD implantation.
Selective Dysfunction of Ventricular Electrode‐Endocardial Junction Following DC Cardioversion in a Patient with a Dual Chamber Pacemaker
Authors: DAS GOPAL , STAFFANSON D.B.
Published: July 2006

A patient with a dual chamber pacemaker received two transthoracic (anterior‐anterior paddle position) shocks for VF. Subsequent analysis of stimulation thresholds revealed a marked rise in the ventricular threshold only. Later, she received three additional shocks (anterior‐posterior paddle position) during electrophysiological study to terminate episodes of induced VT. Following these, the ventricular stimulation threshold was > 10 Vat 2.0 ms. The selective damage at the ventricular site in this patient led us to carry out in vitro studies that revealed a preferential shunting of high electrical energy into the ventricular lead, as compared to the atrial lead, following a DC shock. These observations may explain the selective pacing malfunction observed in our patient.
Contact Sensitivity to Polychloroparaxylene‐Coated Cardiac Pacemaker
Authors: IGUCHI NOBUO , KASANUKI HIROSHI , MATSUDA NAOKI , SHODA MORIO , OHNISHI SATOSHI , HOSODA SAICHI
Published: July 2006

Poly‐chloroparaxylene (parylene) is widely used as a material for cardiac pacemaker coating. Contact sensitivity to parylene was proven by patch test. Wrapping the pacemaker in a polytetrafluoroethylene sheet prior to implantation prevented further skin reactions.
Microfibrosis Produces Electrical Load Variations Due to Loss of Side‐to‐Side Cell Connections; A Major Mechanism of Structural Heart Disease Arrhythmias
Authors: SPACH MADISON S. , BOINEAU JOHN P.
Published: July 2006

The purpose of this article is to demonstrate how adaptive changes in myocardial microstructure provide mechanisms for emergent new conduction disturbances that initiate reentrant arrhythmias. The mechanisms are based on discontinuous conduction phenomena produced by increases in cellular hading; these increases result from changes in the normal distribution of the gap junctions. Recent studies indicate that at a microscopic level propagation in normal mature cardiac muscle is stochastic. For example, the nonuniform and irregular distribution of the gap junctions in such normal muscle produces load variations that are associated with changes in Vmax inside individual cells during both longitudinal and transverse propagation. The stochastic nature of normal propagation at a microscopic level offers considerable protection against arrhythmias by reestablishing the general trend of wavefront movement after small variations in excitation events occur. If such microscopic diversity is decreased, large fluctuations in load develop that are distributed over more cells than usual. The decrease in diversity may be caused by loss of side‐to‐side coupling between fibers, which produces relatively isolated groups of cells with microfibrosis. With loss of side‐to‐side fiber coupling, the myocardial architecture may fail to reestablish a smoothed wavefront at the macroscopic level. Spatial nonuniformities of electrical loading then give rise to conduction block and reentry.
The Cardiac Vulnerable Period and Reentrant Arrhythmias: Targets of Anti‐ and Proarrhythmic Processes
Authors: STARMER C. FRANK
Published: July 2006

Because sudden cardiac death is usually preceded by a reentrant arrhythmia, the precipitating arrhythmia must be multicellular in origin. Therefore clinicians seeking to reduce the incidence of reentrant arrhythmias in their patients with antiarrhythmic drugs that alter propagation may reasonably question the applicability of drug classification schemes (e.g. Sicilian Gambit) that are based on measurements in single cells. This raises a major question: are measures of a drug's anti‐and proarrhythmic potential in single cells predictive of its anti‐ and proarrhythmic properties in tissue? The problem is as follows. From single cell measurements, one expects Class I drugs to reduce excitability, thereby attenuating the occurrence of PVCs. Similarly, one expects Class III drugs to prolong refractoriness and reduce the occurrence of PVCs. We have found in simple models of cardiac tissue that sodium channel blockade (the target of Class I drugs) extends the vulnerable period of a propagating excitation wave, whereas potassium channel blockade (the target of Class III drugs) destabilizes the reentrant path in a manner that amplifies the likelihood of polymorphic tachyarrhythmias. Using analytical, numerical, and experimental studies, we determined that sodium channel blockade was proarrhythmic. In fact, we found that any intervention that slowed conduction was proarrhythmic because slowed conduction increases the vulnerable period and reduces the spatial requirements for sustained reentry. We also found that when obstacles were placed in the path of a propagating wave, reentry occurred when the conduction velocity was less than a critical value. Once reentry was established, we observed that the ECG displayed monomorphic QRS complexes when the reentrant path did not vary from cycle to cycle. Moreover, when the reentiy path did vary from cycle to cycle, the ECG displayed polymorphic QRS complexes. The cycle‐to‐cycle variation in QRS morphology was caused by the spatial variability of the reentry path. The variability of reentry paths (and hence the degree of polymorphic variation in QRS complexes) was amplified by Class III agents. The results presented here show that multicellular proarrhythmic effects are derived from the same mechanisms that exhibit antiarrhythmic properties in single cells.
Atrial Arrhythmias During Chronic Follow‐Up of Surgery for Complex Congenital Heart Disease
Authors: KANTER RONALD J. , GARSON ARTHUR
Published: July 2006

After surgery for complex congenital heart disease, clinically important atrial tachyarrhythmias have a higher than normal incidence if sufficiently large regions of conduction block occur within the atria, especially in the presence of hemodynamic alterations. Sinus bradycardia may result from direct damage to the sinus node and its blood supply. Historical data have identified patients who have undergone the Mustard or Senning operations for dextrotransposition of the great vessels and the Fontan operation in cases of functional single ventricle as being at great risk for atrial tachyarrhythmias. These arrhythmias are especially poorly tolerated when there are co‐existing hemodynamic alterations and are an important source of morbidity and mortality. Until recently, treatment strategies have been limited to antiarrhythmic drugs, bradycardia pacing, and—in suitable patients—antitachycardia pacing, often in combination. Amiodarone has been the most efficacious drug, but has only been of moderate value because of extracardiac side effects. Radiofrequency ablation of the atrial regions critical to reentrant circuits, which was discovered to be of value in patients with atrial flutter and a normal heart is being applied to this diverse group of patients. Early results are promising, but the Fontan operation patients are especially challenging because of early recurrences of apparently new reentrant circuits. Progress in this area will likely come from newer surgical techniques that prevent the milieu for atrial reentry and from multidimensional mapping systems for our current patients.
Neurally Mediated Syncopal Syndromes: Pathophysiological Concepts and Clinical Evaluation
Authors: BENDITT DAVID G.
Published: July 2006

The neurally mediated syncopal syndromes encompass a number of apparently related disturbances of reflex cardiovascular control characterized by transient inappropriate bradycardia and/or vasodilation of various arterial and venous beds. Certain of these syndromes (e.g., carotid sinus syndrome, postmicturition syncope) are encountered occasionally in clinical practice, whereas others are quite rare (e.g., swallow syncope). On the other hand, vasovagal syncope occurs so frequently, that as a group, the neurally mediated syncopal syndromes are among the most important causes of syncope. The pathophysiology of the neurally mediated syncopal syndromes is incompletely understood, but can be considered in terms of four basic elements: (1) the afferent limb; (2) central nervous system (CNS) processing; (3) the efferent limb; and (4) feedback loops. The afferent limb consists of several peripheral and CNS trigger sites and the associated connections to medullary cardiovascular control centers. CNS processing and efferent signals result in both bradycardia, which may be marked or relative, and vasodilatation. Failure of baroreceptor feedback controls to prevent hypotension is important in facilitating development of symptomatic hypotension. Head‐up tilt table testing has become the diagnostic technique of choice for clinically assessing susceptibility to neurally mediated syncope, particularly of the vasovagal type. Most studies suggest that such testing discriminates relatively well between symptomatic patients and asymptomatic control subjects, of whom 10%–15% have a false‐positive test result. Sensitivity of tilt table testing is more difficult to evaluate because there is no accepted diagnostic gold standard. However, sensitivity (measured against a classic presentation) has been estimated to range from 32%–85%, with most reports favoring the higher end of this range. Treatment strategies for neurally mediated syncope remain controversial. Many single episodes do not warrant treatment unless physical injury has occurred, or a high risk occupation or avocation is involved. Tilt test exposure alone may prove beneficial in educating patients with recurrent syncope to recognize warning signs of an imminent faint. Large controlled clinical studies have not been performed to test the efficacy of pharmacological therapy (e.g., β‐adrenergic blockers, disopyramide, serotonin reuptake blockers, vasoconstrictors) or pacing therapy. Such studies may be difficult to undertake due to the variable frequency of spontaneous symptoms and apparent long periods of remission. Nonetheless, many investigators and clinicians have come to rely on these agents, and on tilt testing to guide treatment decisions. Studies employing careful correlation of long‐term clinical follow‐up with results of early and perhaps later repeat tilt studies are still needed.
Unipolar Pectoral Defibrillation Systems
Authors: REDDY RAMAKOTA K. , BARDY GUST H.
Published: July 2006

Over the past 15 years, the implantation of automatic defibrillators has evolved from an obscure, impractical, and often morbid procedure to nearly a routine therapy. Initial large abdominally implanted generators with multiple epicardial leads have given way to much smaller, pectorally implanted systems utilizing only a single lead. These systems are better accepted by physicians and patients and rival recent‐generation pacemakers in their implantation simplicity. Outcomes with single lead defibrillator implantation have been excellent. They are 99% effective at eliminating sudden death in large cohorts of patients, with overall survival of 94.4% at 18 months. Previously significant perioperative complications and mortality associated with epicardial systems have been virtually eliminated. Transvenous single lead systems now provide defibrillation efficacy at a level that makes epicardial leads unnecessary in most patients. Although inappropriate shocks are not a morbid complication, they still occur in approximately 15%–30% of patients. This is an area for improvement in defibrillator therapy, which, though invisible in total mortality statistics, is significant in terms of patient comfort and acceptance. Incremental improvements in pulse generator design and defibrillator lead technology are being made. Perhaps the most interesting new development will be the dual chamber device, incorporating an atrial electrode for sensing, pacing, and perhaps, atrial defibrillation. Such improvements will continue to make device therapy of all arrhythmias more versatile and improve patient comfort both in terms of device size and inappropriate shocks. It is unlikely, however, that further technological advances can further diminish the already small complication rate or improve the already excellent efficacy of current pectoral single lead systems. Defibrillator technology has already reached a maturity where technological improvements are less significant than efforts to better define the patient population who will benefit from the therapy.
Permanent Pacing in Ebstein's Anomaly
Authors: ALLEN MARVIN R. , HAYES DAVID L. , WARNES CAROLE A. , DANIELSON GORDON K.
Published: July 2006

Patients with Ebstein's anomaly present unique challenges to permanent pacing due to anatomical variations and tricuspid valve replacement. We retrospectively reviewed our experience with permanent pacing in patients with Ebstein's anomaly between 1976 and 1993. We identified 401 patients with Ebstein's anomaly, of whom 15 (3.7%) required permanent pacing (1 of the 15 was implanted elsewhere). Of the 15, there were 8 females and 7 males (mean age 32 years [range 7‐74]); the indications for pacing were AV block in 11 and sinus node dysfunction in 4. Eight patients were programmed with WI and seven with DDD. All VVI patients were paced epicardially. Two patients with DDD pacemakers had transvenous atrial and ventricular leads, 4 DDD patients had transvenous atrial leads and epicardial ventricular leads, and 1 patient had both epicardial and transvenous systems. Associated surgical procedures included tricuspid valve replacement in 14 of 15, atrial septal defect repair in 10 of 15, atrioplasty in 7 of 15, prior tricuspid annuloplasty in 4 of 15, pulmonary vein dilation in 1 of 15, and conduction system ablation in 2 of 15. Patients had a mean follow‐up of 35 months (range 1‐168 months). Complications requiring operative intervention occurred in four patients. One patient had displacement of a transvenous ventricular lead. A second patient had an epicardial lead failure. A third patient had a nonfunctioning atrial lead that displaced across the tricuspid valve, causing severe tricuspid regurgitation. The fourth patient had multiple epicardial and endocardial leads exit block with secondary diaphragmatic stimulation. Permanent pacemakers were required in 3.7% of patients with Ebstein's anomaly, with the indication being intrinsic conduction disease in the majority of patients. Ninety‐three percent of patients required tricuspid valve replacement, suggesting more severe manifestation of Ebstein's anomaly. Twenty‐seven percent had complications requiring surgical intervention. Thus, permanent pacing in patients with Ebstein's anomaly can be challenging and should be approached by an experienced physician. (PACE 1997;20[Pt. I]:1243‐1246)
PR Interval Adaptation in the Denervated Transplanted Heart
Authors: KOLLER‐STRAMETZ JEANETTE , KRATOCHWILL CHRISTOPH , GRABENWÖGER MARTIN , LAUFER GÜNTHER , PAGHER RIGHARD , GEMEINER NORA , GASIC SLOBODAN , HEINZ GOTTFRIED
Published: July 2006

In the present study, the dynamic PR response upon standardized treadmill exercise was investigated in 21 transplant recipients (recipient age 48 ± 17 years, donor age 31 ± 12 years, > 1 year after transplantation). MR and PR interval were measured at rest and at the end of each 25‐Wincrease in workload till peak exercise. In 17 cases norepinephrine (NE) was assessed at rest, and at the end of each workload the MR increased from 99.3 ± 14 to 143.4 ± 25 beats/min at individual peak exercise, and NE increased from 1.307 ± 1,163 to 3.688 ± 2.036 pg/mL. while the PR interval shortened from 149.2 ± 13 to 119.3 ± 20 ms. On average. PR decreased by 3.4 ms for a 10‐beat increase in HR, and the HR‐PR interval relationship was described by a linear regression (y = 176.8–0.3469x, P = 0.0001). One patient who was unable to increase his NE levels upon exercise showed virtually no decrease in the PR interval and no HR increase. Both recipient age and donor age were moderately and significantly related to the minimum PR interval achieved at peak exercise (r = 0.6. P = 0.008 and r = 0.51. P = 0.049, respectively). These data show the following: (1) adaptation of the PR interval upon exercise does occur in the denervated transplanted heart; (2) the HR‐PR relation is similar to that reported in the innervated heart; (3) the overall decline in PR interval is blunted, since denervated patients start at shorter resting PR intervals and achieve relatively longer PR intervals at peak exercise when compared to their innervated counterparts; (4) these exercise induced changes of the PR interval may be explained by circulating NE; and (5) NE levels achieved at peak exercise and the sensitivity of the AV node to NE seem to be age related. (PACE 1997; 20[Pt. I]:1247‐1251)
Predictors of Permanence of Successful Radiofrequency Lesions Created with Controlled Catheter Tip Temperature
Authors: LAOHAPRASITIPORN DUANGMANEE , WALSH EDWARD P. , SAUL J. PHILIP , TRIEDMAN JOHN K.
Published: July 2006

Transient interruption of accessory pathway (AP) conduction is often encountered during creation of HF lesions, with return of conduction after seconds to weeks. Maximum catheter tip temperature (Tmax) bas not been shown to be a good predictor of successful RF ablation. However, other indices related to catheter tip temperature (T) may predict permanent AP interruption. Ninety‐one successful RF applications in 58 patients (mean age 11.9 ± 5.5 years, 38 WPW syndrome, 18 concealed AP, 2 both) were reviewed retrospectively. Forty‐two HF applications were transiently successful, with a median time of AP conduction recurrence of 120 seconds (sec: range, 1 sec to > 1 day). This group was compared with 49 permanently successful RF applications. T was measured and controlled using the Medtronic Atakr® system (San Jose, CA, USA). RF lesion duration, power output, rmax, and time to Tmax (tmax) were not significantly different between the two groups. By univariate analysis, each of the following indices was able to discriminate between the transient and permanent lesions, and highly correlated with one another; T at the moment of AP interruption (Tsucc; transient 55.0 ± 7.9°C vs permanent 49.8 ± 7.7°C, P = 0.0025), time to success (tsucc; transient 4.0 ± 3.0 sec vs permanent 1.8 ± 1.3 sec, P = 0.0001), ratio of Tsucc/Tmax (transient 0.76 ± 0.23 vs permanent 0.57 ± 0.27, P = 0.0007) and ratio of tsucc/tmax (transient 0.91 ± 0.69 vs permanent 0.41 ± 0.41, P = 0.0001). By logistic regression analysis, no single variable or combination of variables was superior to tsucc for prediction of outcome, with a breakpoint of 2.3 seconds having a sensitivity of 74% and a specificity of 65%. During temperature controlled RF application, indices of time and temperature were well‐correlated with permanent elimination of AP conduction. Time to interruption of AP conduction < 2.3 seconds after the onset of RF application was predictive of the permanence of successful RF applications. Known relations between HF lesion volume and catheter tip temperature suggest that early conduction block may be an indicator of anatomical proximity of the catheter tip and the AP. These data suggest that, in conjunction with electrogram criteria, selection criteria for optimal sites for RF application may continue to be refined after the onset of RF application, and support the practice of terminating RF application if AP conduction is not rapidly interrupted. (PACE 1997; 20[Pt. I):1283‐1291)
Long‐Term Survival and Complications in Patients With Malignant Ventricular Tachyarrhythmias: Treatment With a Nonthoracotomy Implantable Cardioverter Defibrillator With or Without a Subcutaneous Patch
Authors: JAFAR M. ZUBAIR , SCHLOSS EDWARD J. , MEHDIRAD ALI AKBAR , KEIM STEPHEN , RIST KEVIN , SIDDIQUI SAADI , TCHOU PATRICK J
Published: July 2006

The Endotak lead system and ICD has been used to treat patients with malignant ventricular arrhythmias. We analyzed The clinical characteristics of 1,053 patients who underwent implantation of The Endotak lead system with or without a subcutaneous patch. Group A consisted of 567 patients receiving The Endotak lead with a subcutaneous patch: group B consisted of 486 patients receiving The Endotak lead alone. The 2‐year survivals from sudden death, cardiac death, and total death in groups A and B were 97.6%/98.2% (P = 0.38), 88.6%/92.7% (P = 0.09), and 84.7%/86.8% (P = 0.06). respectively. Minimum tested effective defibrillation energy at implantation was 17.2 ± 5.2 J for group A and 15.8 ±5.1 J for group B (P < 0.01). The operative mortality was 1.8% in group A and 0.6% in group B (P = 0.09). The incidence of lead dislodgment, malfunction, and infection was 6,7% for group A and 3.5% for group B (P < 0,01), Sudden death survival was excellent in both groups with less lead complications in group B. The Endotak lead alone may be The preferred choice of lead configuration in those patients who have adequate defibrillation thresholds at implant. (PACE 1997: 20[Pt. I]:1305‐1311)
The Ongoing Influence of Staff Training on the Performance of Radiofrequency Catheter Ablation
Authors: ROSENHECK SHIMON , ROSE MICHAL , SHARON ZEHAVA , WEISS TEDDY A. , GOTSMAN MERVYN S.
Published: July 2006

The aim of this study was to assess whether the performance of RF catheter ablations continues to improve by further staff training once an initial success rate of > 90% has been achieved. Two hundred and ninety‐five procedures of SVT catheter ablation using RF energy were studied. Atrial tachycardia and atrial flutter substrate ablations were not included. The procedures were performed during a 4‐year period by the same physician and nurse, who had previous training in these procedures. The 4‐year period was subdivided into four consecutive 1‐year periods in which 69, 72, 68, and 86 procedures were performed. The outcome, recurrence rate, and duration of the curative procedure were compared among the four periods. There was no significant difference in the initial success rate among the four periods. The recurrence rate decreased from 21.74% to 13.95% (P < 0.05). The duration of the curative procedure decreased from 93.7 ± 78.4 minutes to 39.1 ± 32.2 minutes (P < 0.001), and the fluoroscopic time decreased from 25.5 ± 22.3 minutes to 11.3 ± 8.2 minutes (P < 0.001). These results were similar when accessory pathway and selective AV nodal pathways ablations were separately evaluated. Following the initial staff training, during which the expected 80%‐90% success rate is achieved, additional training will reduce the recurrence rate and the duration of the procedures at a similar level of success. (PACF 1997; 20[Pt. I]:1312‐1317)
Atrial Electrophysiological Features in Patients with Wolff‐Parkinson‐White and Atrial Fibrillation: Absence of Rate Adaptation of Intraatrial Conduction Time Parameters
Authors: RICCARDI RICCARDO , CAITA FIORENZO , CIUSTETTO CARLA , CARDIOL SILVIA
Published: July 2006

Clinical electrophysiology has not yet clearly defined atrial features that can predict spontaneous occurrence of atrial fibrillation (AF). The aim of this work was to identify atrial electrophysiological features that can distinguish Wolff‐Parkinson‐White patients with spontaneous AF from those without this arrhythmia. Sixty‐nine patients with Wolff‐Parkinson‐White were divided into three groups: group I (16 patients) with spontaneous AF; group II (35 patients) with reciprocating tachycardia but not AF; and group III (18 patients) asymptomatic without documented arrhythmias. Atrial effective refractory periods (ERPs) and intraatrial conduction times in response to premature extrastimuli were analyzed. The latter were evaluated as the A1A2 interval minus the correspondent S1S2 interval (A1A2‐S1S2), S2A2 and the interval A1A2 following the shortest S1S2 producing atrial activation (FRP'). All the parameters have been evaluated in two atrial sites and at two atrial pacing cycle lengths (600 and 400 ms). For all the parameters, the difference (“gradient”) was calculated between the values of the same parameter measured at the atrial pacing cycle length of 600 ms and that found at the atrial pacing cycle length of 400 ms in the same recording site in each patient was calculated. Atrial FRP did not differ significantly in the three groups. Intraatrial conduction parameters, evaluated in the high right atrium (HRA), were longer when measured at an atrial pacing of 400 ms and showed a lack of rate adaptation in patients with spontaneous AF. In group I patients in particular, FRP’became longer with the increase of atrial rate, while in groups 2 and 3, it usually shortened. The mean gradient of HRA FRP’was ‐15.0 ± 19 ms in group I as compared to 5.7 ±13 ms in group II and 6.4± 13 ms in group III (P < 0.001); sensitivity. specificity, and negative predictive value of a negative gradient in the identification of patients with spontaneous AF, were, respectively, 83%, 75%, and 93%. Patients from groups 2 and 3 did not differ in any of the analyzed parameters. Patients with Wolff‐Parkinson‐White and spontaneous AF showed prolonged intraatrial conduction times and a different behavior in response to modification of heart rate. (PACE 1997;20[Pt. I]:1318‐1327)
Toward Optimizing a Preshaped Catheter and System Parameters to Achieve Single Lead DDD Pacing
Authors: BROWNLEE ROBERT R. , SWINDLE M. MICHAEL , BERTOLET ROY , NEFF PAUL
Published: July 2006

P wave electrogram amplitudes and atrial stimulation thresholds were determined in eight Hanford miniature swine using a preshaped catheter with an “S” curve in the SVC, and a major lobe in the atrium to enhance electrode contact with the atrial wall. The catheter was designed for pacing and sensing in the DDD mode. P wave amplitudes were also ascertained with two commercially available VDD leads and compared to the data from the experimental catheters. The preshaped catheter used two 6‐mm2 platinum iridium atrial electrodes with a 7‐mm separation. Both atrial electrodes are on the same side of the catheter, facing outward on the major atrial lobe formed in the catheter. The P wave amplitudes were tested only in the differential bipolar configuration. For the eight preshaped catheters, the mean was 6.6 ± 3.8 mV while for the conventional leads it was 2.9 ± 1.6 mV. The mean atrial stimulation thresholds ranged from 1.1 t 0.2 V to 2.3 ± 1.2 V, with still lower thresholds of 0.9‐1.3 V when using the parallel unipolar atrial electrode configuration, in which both parts of the bipolar atrial electrode are configured as a unipolar electrode. The data suggest that bipolar stimulation may be effective if sequential reverse polarity pulses are used to achieve cathodal stimulation from each electrode of the bipolar pair, on a beat‐to‐beat basis. (PACE 1997; 20[Pt. I]:1354‐1358)
Surgical Interruption of a Left Inferior Vena Cava Following the Transfemoral Implantation of a Permanent Pacing Lead
Authors: TRIGANO ALEXANDRE J. , PAGANELLI ERANCK , ALIMI YVES , JUHAN CLAUDE
Published: July 2006

This report describes the case of a patient in whom, after an unsuccessful attempt through the subclavian vein, a permanent pacing lead was inserted through the femoral vein and a left inferior vena cava with azygos continuation. The procedure was followed 4 months later by a pulmonary embolism complicating a right femoroiliac thrombosis. The patient was successfully treated by a percutaneous lead extraction procedure combined with an inferior vena caval surgical interruption. (PACE 1997; 20[Pt. I]:1365‐1366)
Is This the Natural History of the Retention Wire? A Case Report
Authors: LAU CHING , NISHIMURA SANDRA C. , OXORN DONALD , GOLDMAN BERNARD S.
Published: July 2006

We report on a 71‐year‐old man who had a dual chamber pacemaker implanted in 1991. A Class IV fracture of the Telectronics Accufix 330–801 atrial lead was observed on a chest X ray in December 1993. Serial chest X ray and fluoroscopy documented stable position of the migrated fractured f wire. The patient remained asymptomatic and a decision for conservative monitoring was made. A subsequent finding of a right atrial mass on echocardiography and evidence of pulmonary embolism on lung scan prompted a change of strategy. The patient underwent atriotomy, and a right atrial thrombus was discovered associated with the fractured J retention wire, both of which were extracted uneventfully. This case is illustrative that despite apparent stability of a Class IV fracture, it may result in endothelial injury with a thrombogenic nidus and resultant complications.
A Comparative Study of Activity and Dual Sensor: Activity and Minute Ventilation Pacing Responses to Ascending and Descending Stairs
Authors: ALT ECKHARD , COMBS WILLIAM , WILLHAUS RICHARD , CONDIE CATHERINE , BAMBL ERWIN , FOTUHI PARWIS , PACHE JÜLJRGEN , SCHÖMIG ALBERT
Published: July 2006

Previous studies with activity‐based rate; adaptive pacemakers have shown a somewhat paradoxical response when comparing ascending stairs to descending stairs. The objective of this investigation was to measure dual‐sensor rate response provided by activity and minute ventilation (MV) compared with activity alone, and with a control group, during ascending and descending stairs. For dual sensor mode, measured mean peak pacing rate with 72 (92) steps per minute was 111 ± 13 beats/min (124 ± 14 beats/min) ascending stairs and 81 ± 7 beats/mm (97 ± 13 beats/min) for descending. For activity mode alone, mean peak pacing rate was 90 ± 12 beats/min (108 ± 19 beats/min) ascending stairs and 97 ± 12 beats/min (123 ±17 beats/min) descending. The mean peak control group heart rate ascending stairs for a step rate of 72 (92J steps/min were 116 ± 11 beats/min (127 ±14 beats/min) ascending stairs and for descending 89 ± 12 beats/min (95 ± 11 beats/min). While for dual sensor controlled pacing there was a significant difference for ascending and descending stairs at both step rates, there was no difference between going upstairs and downstairs for activity mode alone. Rates with dual sensor did not significantly differ from respective rates of the control group. The mean correlation coefficient between MV and paced rate was 0.85. Pacing heart rates delivered by the dual sensor mode were appropriate for ascending and descending stairs. In contrast to activity mode alone, the peak heart rates for dual sensor mode are higher during ascending than during descending stairs.
Initiating Sequences in Exercise Induced Idiopathic Ventricular Tachycardia of Left Bundle Branch‐Like Morphology
Authors: GILL JASWINDER S. , PRASAD KRISHNA , BLASZYK KRZYSZTOF , WARD DAVID E. , CAMM A. JOHN
Published: July 2006

Initiating Sequences in Exercise Induced Idiopathic Ventricular Tachycardia of Left Bundle Branch‐Like Morphology. Initiating sequences for VT may infer the underlying arrhythmogenic mechanisms. This study examines the initiating sequences of exercise induced idiopathic VT of left bundle branch block‐like (LBBB‐like) morphology and makes an attempt to relate these to clinical aspects and the mechanisms of arrhythmia. Thirty‐two patients (mean age 33.4 ± 13.2 years; 18 men) with exercise induced VT in the absence of structural cardiac abnormality on history, clinical examination, and noninvasive and invasive investigations were divided into two groups on the basis of the initiating sequence of VT on exercise. Group I consisted of patients with long‐short sequence of RR intervals prior to the onset of VT (initiating/preinitiating cycle length ratio < 0.78). Group II consisted of patients without changes in cycle length prior to VT. Group I mechanism would suggest delayed afterdepolarizations (DADs) or reentry whereas group II mechanism triggered activity due to early afterdepolarizations. Fourteen patients (group I) had long‐short sequence and 18 patients (group II) were without cycle length changes prior to VT initiated during exercise. VT axis was inferior in all 18 patients in group II but only in 9 patients in group I (P = 0.02). In these predefined patient groups, sustained monomorphic VT could not be initiated by programmed stimulation in any patient in group I, whereas four patients in group II had inducible VT. Patients in group II also had higher incidence of sustained VT on ambulatory monitoring (P < 0.05). The two groups did not differ in other respects. This study demonstrates the existence of at least two possible mechanisms of initiation of exercise induced idiopathic VT of LBBB‐like morphology. VT initiated without cycle length changes is more common, more likely to have an inferior axis suggesting an outflow tract origin, and is probably related to triggered activity secondary to DADs. VT initiated with a long‐short sequence is more often nonsustained and may have a superior axis suggesting an origin from the body or septal region of the ventricle. The two groups, therefore, exhibit differences in electrophysiological characteristics that may aid classification and therapy of this arrhythmia.
Do the Effects of Antiarrhythmic Drugs on Defibrillation Efficacy Vary among Different Shock Waveforms?
Authors: MURAKAWA YUJI , YAMASHITA TAKESHI , KANESE YUKIHIRO , OMATA MASAO
Published: July 2006

This study was designed to extend our knowledge on how pharmacological modification of defibrillation efficacy is associated with shock waveform. In 35 anesthetized dogs, the baseline transcardiac DFT was determined using 12‐ms monophasic and three biphasic waveforms(10 ms‐2 ms, 8 ms‐4 ms, and 6 ms‐6 ms). Twenty‐eight dogs were then treated with either lidocaine (n= 7). mexiletine (n = 7), dofetilide (n = 7), or MS‐551 (n = 7), while 7 dogs were left untreated to confirm the reproducibility of DFT data. Subsequently, DFT measurements were repeated in all dogs. Waveform related differences of the baseline DFT were significant, and the monophasic DFT was higher than any of the biphasic DFTs. Lidocaine increased DFT by 11%± 12% (12‐ms monophasic), 20%± 20% (10 ms‐2 ms, P < 0.05), 13%± 20% (8 ms‐4 ms), and 12%± 10% (6 ms‐6 ms, P < 0.05). With infusion of mexiletine. the DFT increased by 17%± 16% (P < 0.05), 9% i 12%, 10%± 10% (P < 0.05), and 4%± 15%, respectively. Both dofetiiide and MS‐551 significantly decreased the DFT regardless of the pulse waveform (dofetiiide: from −18%± 19% to −24%± 19%, MS‐551: from −18%± ll% to −32%± 6%). In all drug groups, waveform related differences in DFT remained significant. These results support the view that the advantages of biphasic shock waveforms are not lessened by treatment with antiarrhythmic drugs.
Paroxysmal Atrial Fibrillation and High Degree AV Block: Use of Single‐Lead VDDR Pacing with Mode Switching
Authors: NOWAK BERND , VOIGTLA∘N∘DER THOMAS , ROSOCHA STEFAN , LIEBRICH ANDREAS , ZELLERHOFF CHRISTIAN , PRZIBILLE OLIVER , GEIL STEPHANIE , HIMMRICH EWALD , MEYER JÜRGEN
Published: July 2006

Dual chamber rate responsive pacing incorporating a mode switching option is increasingly listed in patients with chronic paroxysmal atrial fibrillation and high degree AV block. Single‐lead VDDR pacemakers have been rarely used for this indication. The purpose of this study was to determine thnir reliability of atrial sensing during atrial fibrillation, the percentage of at rial synchronous ventricular pacing, and the behavior of the sinus rate outside the phases of atrial fibrillation. We studied ten patients with a single‐lead VDDR pacemaker implanted for this indication. Follow‐up visits were performed at predischarge and after 1, 3, 6, 12. 18, and 24 months. During the mean follow‐up period of 18.9 ± 6.9 months, the atrial sensing thresholds in sinus rhythm remained stable. Atrial synchronous ventricular stimulation was achieved in 68,7 ±31.2% (median 82.5%) of the whole follow‐up time. All patients showed an adequate atrial rate response during sin us rhfthm. Atrial fibrillation was detected by the pacemakers in 24.0 ± 29.8% of time. In 3 of 10 patients the duration of atrial fibrillation showed a steady increase from visit to visit. The sensed amplitudes of atrial fibrillation ranged from 0.1–1.0 mV. A programmed atrial sensitivity of 0.1 mV was necessary to achieve complete sensing of atrial fibrillation. None of the patients experienced tachycardias with optimized pacemaker programming. Single‐lead VDDR pacing incorporating a mode‐switching option is useful in patients with high degree AV block and paroxysmal atrial fibrillation, since it provides atrial synchronous ventricular pacing in more than two‐thirds of follow‐up time. In a subgroup of patients, a progressive increase of the time during atrial fibrillation was demonstrated. A reliable detection of paroxysmal atrial fibrillation requires the programming of the atrial sensitivity to its most sensitive value.
Atrial Flutter with 1:1 Atrioventricular Conduction Caused by Propafenone
Authors: EL‐HARARI MOHAMED B. , ADAMS PHILIP C.
Published: July 2006

We describe a case of 1:1 atrial flutter in a patient with coronary disease taking propafenone. In atrial flutter, the atrial rate is usually about 300 beciis/min with 2:1 AV conduction and a ventricular rate of 150 beats/min. Class IA antiarrhythmic drugs, especially quinidine and disopyramide, may cause 1:1 AV response because they reduce atrial rate and are vagolytic. However, propafenone is a Class IC agent and has no anticholinergic properties, and the occurrence of 1:1 AV conduction at a rate of about 250 beats/min is an important side, effect that, although uncommon, should be recognized.
Inappropriate Shock Therapy for Nonsustained Ventricular Tachycardia in a Dual Chamber Pacemaker Defibrillator
Authors: MANN DAVID E. , KELLY PATRICIA A. , REITER MICHAEL J.
Published: July 2006

We report a patient who Received a CPI Ventak AV II DR ICD for ventricular tachycardia and complete heart block without an escape rhythm. During induced nonsustained ventricular tachycardia, the device, although programmed to deliver noncommitted shocks, acted like a committed device. This phenomenon is due to undocumented behavior that is likely to occur in any patient who is pacemaker dependent and has nonsustained ventricular tachycardia.
Electromagnetic Interference and ICD Discharge Related to Chiropractic Treatment
Authors: VLAY STEPHEN C.
Published: July 2006

Electromagnetic interference is well known to cause false sensing in ICDs. Sources may include instrumentation involved with acupuncture, arc welding, electrocautery, diathermy, electrolysis, and transcutaneous electric nerve stimulator units as well as power lines. Patients with ICDs are cautioned to avoid exposure to these sources.