bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneously Collected Monopolar and Discrete Bipolar Electrograms: Comparison of Activation Time Detection Algorithms
Authors: PIEPER CARL F. , BLUE RUSSELL , PACIFICO ANTONIO
Published: July 2006

Designation of the time of local activation is fundamental to electrophysiological mapping. In normal myocardium, the minimum slope in extracellular monopolar (MP) electrograms has been linked through simultaneous intraceliular and extracellular recordings to phase 0 of the action potential. However, no similar correlation has been demonstrated for a parameter from bipolar (BP) electrograms. now commonly used during electrophysiological studies and intraopera‐tive mapping. The purpose of this work is to compare the activation time, determined according to several common algorithms applied to BP electrograms, with the time of the minimum slope in MP electrograms. Simultaneous normal epicardial MP and BP electrograms were acquired from sub;ects undergoing surgery for Wolf‐Parlcinson‐White Syndrome and from dogs. The activation time in BP electrograms was defined by four algorithms; (1) peak (P); (2) greatest absolute slope (S); (3) zero crossing of the segment containing the greatest slope (FZC); and (4) morphological (M). Each was compared to the time of the minimum slope in the simultaneously recorded MP response. The incidence of outliers was tabulated. The distribution of activation times computed using each BP algorithm was statistically different from the distribution of activation times derived from MP electrograms. M performed best (absolute difference: 2.6 ± 2.9 msec; cor coef: 0.9925 in man). The M. P, FZC, and S algorithms produced 3.2%, 3.5%, 4.7% and 4.7% outliers, respectively. The overall performance of a morphologically based algorithm is superior fo simplistic BP algorithms hased only on slope or peak.
Anatomical Mechanisms Explaining Damage to Pacemaker Leads, Defibrillator Leads, and Failure of Central Venous Catheters Adjacent to the Sternoclavicular Joint
Authors: MAGNEY JEAN E. , FLYNN DAVID M. , PARSONS JONATHAN A. , STAPLIN DAVID H. , CHIN‐PURCELL MICHELLE V. , MILSTEIN SIMON , HUNTER DAVID W.
Published: July 2006

The literature suggests that approximately 93% of all pacemaker lead fractures occur in the segment of the lead lateral to the venous entry, and costoclavicular compression has been implicated. While blood vessels can be compressed by movements of the clavicle, our research suggests that lead and catheter damage in that region is caused by soft tissue entrapment rather than bony contact. Dissection of eight cadavers with ten leads revealed that two entered the cephalic vein, and were not included in the study. Of the other eight leads, four passed through the subclavius muscle, two through the costoclavicular ligament, and two through both these structures before entering the subclavian, internal jugular, or brachiocephalic vein. Anatomical studies demonstrated that entrapment by the subclavius muscle or the costoclavicular ligament could cause repeated flexing of leads during movements of the pectoral girdle. Cineradiology of patients with position dependent catheter occlusion confirmed entrapment by the subclavius muscle. Soft tissue entrapment imposes a static load upon leads and catheters, and repeated flexure about the point of entrapment may be responsible for damage previously ottributed to cyclic costoclavicular compression.
Isoproterenol Induced Cerebral Hypoperfusion in a Heart Transplant Recipient
Authors: NJEMANZE PHILIP C.
Published: July 2006

To determine the effect of tilt isoproterenol provocation on cerebral perfusion in a patient with denervated heart, transcranial Doppler sonography was used to assess changes in cerebral blood flow velocity during upright tilt test. A 51‐year‐old man with history of syncopal spells after heart transplantation was evaluated hy using upright tilt test with and without isoproterenol for 30 minutes, respectively, at 80± inclined. Mean cerebral blood flow was measured in the main stem of the right middle cerebral artery. Blood pressure and heart rate were noninvasively monitored. Tilt isoproterenol provocation but not tilt alone induced a significant reduction in cerebral blood flow velocity, without remarkable hypotension. There was no change in respiratory activity. This may indicate that vagal reflexes are not implicated in the mechanism of isoproterenol to induce cerebral hypoperfusion and hence neurally mediated syncope.
Drugs, gery, Cardioverter Defibrillator: A Decision Based on the Clinical Problem
Authors: CAPUCCI ALESSANDRO , BORIANI GIUSEPPE
Published: July 2006

These three therapeutic options are the basis of sudden cardiac death prevention: antiarrhythmic drugs, surgery, and automatic implantable cardioverter defibrillator. Each of these treatments has specific favorable and unfavorable indications. Antiarrhythmic drugs are mainly limited by the low therapeutic profile, proarrhythmic effects, complex pharmacokinetics and pharmacodynamics, possible negative inotropic effects, and the possible change of the organic substratum. Arrhythmia surgery may be limited by the need of a highly trained center, by a relatively high perioperative mortality (up to 15%), and by limited electrophysiological and clinical indications. The implantable cardioverter defibrillator is an expensive tool with a theoretically wide range of clinical indications, with already proven efficacy in converting ventricular fibrillation to sinus rliythm but with unproven efficacy on prolonging survivaJ because of a lack of controlled trials (which, we must admit, is also true for drugs and surgery). The results of the ongoing multicenter trials on this item will clarify this clinical point. The choice among these different therapeutic options is mainly based on hemodynamic status (ejection fraction], feasibility of a surgical treatment, and the electrophysiological characteristics of the ventricular arrhythmia.
Atrioventricular Nodal Reentry: Evidence Supporting an Intranodal Location
Authors: JOSEPHSON MARK E. , MILLER JOHN M.
Published: July 2006

The exact site of the reentrant circuit in AV nodal reentry remains controversial. While recent ablative techniques have yielded information, the interpretation of which suggests that the atrium is required, other explanations for these interpretations are available. Prior pathophysiological studies with three‐dimensional reconstruction of the node suggest that it is a highly anisotropic structure and extends through Koch's Triangle. Data from humans suggesting the atria are not necessary include the presence of AV dissociation during supraventricular tachycardia (SVT), depolarization of atrial tissue surrounding the node without affecting SVT, pacing induced AH intervals exceeding those during SVT, and site dependency ofa critical AH interval (exceeding afrial refractoriness) that is required for initiation of AV nodal reentry.
Should Radiofrequency Therapy Be Performed in Every Symptomatic Patient with Supraventricular Tachycardia? (Pro Drug Position)
Authors: ANDRESEN DIETRICH , BEHRENS STEFFEN , BRÜGGEMANN THOMAS , SCHRÖDER ROLF
Published: July 2006

The indication for treatment of paroxysmal supraventricular tachycardia depends on the frequency and severity of the tachycardia attacks. If the tachycardia attacks are mildly symptomatic and occur only once or twice a year, there is no indication for either continuous drug therapy or radiofrequency oblation. The only therapeutic measure required is termination of each acute event. If symptoms occur frequently, long‐term antiarrhythmic drug therapy is then indicated and will be effective for chronic prophylaxis in most individuals with a low risk of proarrhythmic events. Only in patients with severe or life‐threatening symptoms or cases refractory to drug therapy would radiofrequency ablation possibly be justified.
The Complexity of Mechanisms in Ventricular Tachycardia
Authors: BRUGADA JOSEP , BOERSMA LUCAS , ALLESSIE MAURITS , NAVARRO‐LOPEZ FRANCISCO
Published: July 2006

Several pathophysiological substrates may be responsible for ventricular tachycardia (VT) occurring in the chronic phase of a myocardial infarction. Reentrant circuits can have anatomical or functional characteristics. Macroreentrant or microreentrant circuits have been described. Activation maps have shown that the circuit can be represented as a single loop or as a figure‐of‐eight reentrant pattern. All these different substrates have in common that they result in sustained monomorphic VT. The adequate treatment will probably be different for each one of them. In this article, some possible pathophysiological substrates of VT occurring in the chronic phase of a myocardial infarction are reviewed. Finally, we speculate on how catheter ablation may modify each one of the substrates.
The Defibrillation Threshold: A Comparison of Anesthetics and Measurement Methods
Authors: GILL ROBERT M. , SWEENEY ROBERT J. , REID PHILIP R.
Published: July 2006

In 18 open‐chested mongrel dogs (18.0 ± 1.7 kg) we compared three anesthetics and three methods for measuring the defibrillation threshold. Six animals were anesthetized with pentobarbital (30 mg/kg) and maintained with a pentobarbital infusion (4 mg/kg per hour). All other animals were anesthetized with sodium brevital (10 mg/kg) and maintained with either halothane gas (1.5%, N = 6) or isoflurane gas (1.8%, N = 6). In each dog. we measured the energy required for 50% successful defibrillation (E50) with: (A) a 3 reversal—up/down method; (B) a 15 shock—up/down method; and (C) a percent success method. Anesthetics and methods were selected in a balanced random order. Ventricular fibrillation was induced with 50 Hz electrical pacing. After 15 seconds, monophasic truncated exponential shocks were delivered by way of a spring‐patch electrode configuration. The animal was rescued (if needed) and fibrillation/defibrillation episodes were repeated at 3 minute intervals. After each determination of the E50, the E50 was delivered in ten successive defibrillation trials to determine its actual success rate. We found no significant difference in E50 among anesthetics; a significant difference (P < 0.05) in E50 between method C (9.7 ± 2.6 joules) and method B (8.2 ± 1.6 joules); no significant difference among anesthetics or methods for the actual success rate of the E50 (45 ± 21% successful); and method A required significantly fewer fibrillation episodes and number of shocks and less cumulative energy than the other methods. We concluded that the anesthetics tested had little effect on E50 but that the method used to determine E50 could have an effect. Also, the E50 estimated by all methods consistently produced an actual success rate lower than 50%.
Electrophysiological Effects of atrial Natriuretic Peptide on the Cardiac Conduction System in Man
Authors: CROZIER IAN , RICHARDS A. MARK , FOY STEPHAN G. , IKRAM HAMID
Published: July 2006

We assessed the effect of atrial natriuretic peptide (ANP) on electrophysiological parameters in man. Electrophysiological parameters were measured before, at 15, and at 30 minutes after the commencement of ANP or placebo infusions (six patients in each group). ANP levels were normal prior to infusion and rose with ANP to 159 ± 43 pmol/L, but were stable during placebo infusion. No change in heart rate or blood pressure occurred in either group. ANP infusion resulted in significant falls in intraatrial conduction time (60 ± 15 to 49 ± 15 msec), PR interval (170 ± 21 to 155 ± 16 msec), right atrial effective refractory period (232 ± 33 to 218 ± 33 msec), and ventriculoatrial refractory period (452 ± 148 to 393 ± 183 msec) while no change was seen with placebo. We conclude that ANP infusion appears to affect atrial refractoriness and velocity of conduction and atrioventricular nodal refractoriness. However, the mechanism of action and clinical significance of this observation remain to be determined.
Distribution of Significant Changes in QRST Area Compared to Supraventricular Complex
Authors: SUZUKI AKIRA , HIRAI MAKOTO , HAYASHI HIROSHI , ICHIHARA YOSHIO , ADACHI MASAYOSHI , OGUCHI SADAO , NISHIYAMA ATSUSHI , SHIMIZU SEIJI , WATARAI MASATO , SHIGA YUKIO , FURUTA TATSUJI , TAKATSU FUMIMARO
Published: July 2006

To assess the effects of right ventricular (RV) pacing on body surface QRST distributions, we recorded QRST isointegral mops (I‐maps) during sinus rhythm and RV pacing in 25 patients with anterior myocardial infarction (MI), 19 with inferior MI, and 14 without MI. The QRST values at each lead point recorded during sinus rhythm and RV pacing with an 87‐lead system were analyzed with a paired t‐test in each patient. An abnormal decrease in the QRST value of the I‐map was assessed by the difference map, which indicated a −“2SD area,” where the QRST integral value was less than the normal range (mean – 2SD) caiculated from 608 normal individuais. The I‐maps were similar during the two activation sequences in patients with and without MI. However, during RV pacing, QHST values significantly decreased over the upper right anterior chest and increased over the lower left anterior chest and back. The ΣDMs (sum of QRST integral vaiues beiow the normal range) for both activation sequences were strongly correlated in patienis with anterior MI and with inferior MI (r = 0.91 and r = 0.92, respectively; P < 0.001). Although small but significant changes in QRST values were detected, the distribution of the “‐2SD area” and the ΣDM were similar during both activation sequences in patients with prior MI. Thus, these findings demonstrate that an altered activation sequence produces small but significant changes in QRST values but that I‐maps still provide information that is useful for the diagnosis of MI during RV pacing.
Voltage Dip in Pacemaker Battery Supply: A New Cause of Pacemaker Mediated Tachycardia
Authors: STROOBANDT ROLAND , VANDENBULCKE FILIEP , FALLEYN HERMAN , SINNAEVE ALFONS
Published: July 2006

A new cause of pacemaker medialed tachycardia was observed in a patient equipped with a Vitatron® Quintech 931 DDD pacemaker. In this type of pacemaker the microprocessor is switched off during the atrial refractory period. Beyond the recommended replacemenl lime, the internal resistance of the battery may increase to such an extent that switching on and off the microprocessor may cause voltage dips. Those voltage dips are erroneously interpreted as P waves hy the atrial sensing amplifier, which may cause self‐triggering of the pacemaker and initiate a pacemaker mediated tachycardia.
The Effects of Rate Responsive Pacing on Exercise Performance in the Postoperative Univentricular Heart
Authors: PARIDON STEPHEN M. , KARPAWICH PETER P. , PINSKY WILLIAM W.
Published: July 2006

Following the Fontan operation for definitive palliation of the univentricular heart, sinus node dysfunction, and/or atrioventricular block requiring pacemaker therapy is common. In previous studies ventricular rate responsive pacing (VVI, R) resulted in improved exercise performance over VVI pacing in anatomically normal hearts with either sinus node disease or atrioventricular block. In this study, the usefulness of both VVI, R and DDD, R pacing are evaluated in the postoperative univentricular heart following the Fontan operation. Eight postoperative Fontan patients with sinus node disease or atrioventricular block underwent exercise testing using a treadmill protocol. Six patients had single chamber ventricular pacemakers and two patients had dual chambered rate responsive pacemakers. Median age at exercise testing was 14 years. Patients were tested in the VVI, VVI, R, and DDD, R modes acting as their own controls. Heart rate, work rate, oxygen consumption, and respiratory exchange ratio were monitored continuously. Heart rate was significantly increased in the rate responsive modes compared to the VVI mode. In spite of the significant increase in heart rate, there was no change in maximal work rate or oxygen consumption. There was also no significant change in oxygen consumption at ventilatory anaerobic threshold. From these data we would conclude that VVI, R pacing in postoperative univentricular hearts does not result in improved exercise performance and that further study with DDD, R pacing is needed to determine its usefulness in this group of patients.
Detection of Atrial Activation By Intraventricular Electrogram Morphology Analysis: A Study to Determine the Feasibility of P Wave Synchronous Pacing From a Standard Ventricular Lead
Authors: GREENHUT SAUL E. , SVINARICH J. THOMAS , RANDALL NIGEL J. , HEALD SPENCER C. , NAPPHOLZ TIBOR A.
Published: July 2006

The detection of atrial activation from a standard ventricular pacing lead with standard ventricular electrodes would provide patients with VVI and VVIR pacing systems atrial rate response and atrial synchrony. In addition to potentially increasing cardiac output appropriately in these patients at rest and during moderate exercise, P wave sensing with such a device could help reduce pacemaker syndrome. In this study, unipolar signals from distal and proximal intraventricular electrodes were recorded from the right ventricular apex in 20 patients. Unipolar eJectrograms from 16 patients were recorded using temporary electrophysiology catheters and in four patients using permanent pacemaker leads. Approximately 3 minutes of data per patient were acquired and analyzed. After selection of a P wave template, the difference in baseline normalized area between the template and signal was calculated on a point‐by‐point basis. The percent of atrial depolarizations correctly detected was determined for each patient and lead configuration at the optimal threshold. Far‐field P wave accuracy was better at the proximal electrode (74 ± 25%) than at the distal electrode (57 ± 34%) (P < 0.025). At the proximal electrode, 15/20 (75%) patients had > 70% accuracy and 11/20 (55%) patients had > 80% accuracy. At the distal electrode, 10/21 (48%) patients had > 70% accuracy and 7/21 (33%) patients had > 80% accuracy. In conclusion, far‐field detection of atrial activation at the ventricular proximal electrode appears possible with sufficient accuracy to provide periods of atrial rate response and synchrony in patients with a single standard lead.
Automatic Atrial and Junctional Tachycardias in the Pediatric Patient: Strategies for Diagnosis and Management
Authors: CASE CHRISTOPHER L. , GILLETTE PAUL C.
Published: July 2006

Unlike supraventricular arrhythmias secondary to reentry, automatic rhylhm disturbances in children are rare and more resislant to standard pharmacological therapy. This article reviews strategies for the diagnosis and managemenl of two of the more common pediatric auto‐matic rhylhm disliirbances, that is, atrial ectopic tachycardia, and junlional ectopic tachycardia. The place of nevver nonpharmacological therapy, such as catheter ablation, in the treatment of these entities is beginning to be explored, yet has not been fully delineated. Despite these iimitalions, there is enough experience ivith these difficult tachycardias in the pediatric age group to formulate some strategies for optimal diagnosis and management.
Low‐Energy DC Catheter Ablation of Left Atrial Ectopic Tachycardia That Had Resulted in Reversible Cardiomyopathy
Authors: KATRITSIS DEMOSTHENES , LEATHAM EDWARD , PUMPHREY CHARLES , REDWOOD DAVID , ROWLAND EDWARD
Published: July 2006

Catheter ablation of automatic atrial tachycardia has been previously reported in a small number of adult cases in which the ectopic focus was predominantly located in the right atrium. We report on a patient with atrial automatic tachycardia originating in the left atrium, in whom successful low‐energy DC catheter ablation was performed via a transseptal puncture. The patient presented wth severe congestive cardiac failure that resolved following the procedure. Catheter ablation in such cases is feasible, it can reverse tachycardia induced ventricular function impairment, and should be attempted before resorting to open heart surgical ablation.
Cardiopulmonary Responses to Exercise in Children with Activity Sensing Rate Responsive Ventricular Pacemakers
Authors: CABRERA MARCO E. , HANISCH DEBRA G. , COHEN MARK H. , MURTAUGH RICHARD , SPECTOR MICHAEL L. , LIEBMAN JEROME
Published: July 2006

The physiological benefits of activity sensing rate responsive ventricular pacing)VVIR) over fixed rate pacing)VVI) were investigated in 14 children during incremenlal cycle exercise. Based on their heart rhythm response during exercise, children were divided into two groups. Group I patients)13 ± 4 years) remained in a paced‐only rhythm when exercised. Group II patients)16 ± 7 years) were paced at rest but converted to sinus rhythm with exercise. In Group I patients, the significant physioJogicol benefits of VVIR over VVI pacing were evidenced hy a 51% increase in peak heart rate)HRmax) and a 16% increase in exercise duration and maximum oxygen uptake)VO2max). Additionally, a 27% reduction in peak oxygen pulse)O2Pmax) was found, reflecting a similar decrease in stroke volume. The cardiorespiraiory responses of Group I and 11 patients were compared in terms of percent of predicted normal values. Although Group I patients in the VVIR mode attained a better exercise performance than in the VVI mode and a normal O2Pmax)108% pred). their HRmax)62% pred) and VO2max)70% pred) fell far below normal values. In comparison. Group II patients, who went into sinus rhythm, achieved normal values for HRmax)84% pred), VO2max)90% pred), and O2Pmax)97% pred). The higher pacing rates attained by Group I patients in the VVIR mode may have allowed them to reach not only a higher cardiac output but also a more normal stroke volume at peak exercise than in the VVI mode. However, the overall exercise performance of children paced in the VVI and VVIR modes were significantly diminished compared to the performance of children who went into sinus rhythm with exercise.)
Are We Being Driven to Two Sensors?: Clinical Benefits of Sensor Cross‐Checking
Authors: COWELL RICHARD , MORRIS‐THURGOOD JAYNE , PAUL VINCENT , ILSLEY CHARLES , CAMM A. JOHN
Published: July 2006

Sensor cross‐checking within dual sensor rale responsive pacemakers is designed to reduce the incidence of inappropriate rate response. We describe a patient in whom sensor cross‐checking prevented the occurrence of angina during automotive transport.
Evaluation of Temporary Atrial Pacing Leads
Authors: SCOTT WILLIAM A. , LEMLER MATTHEW , FARLEY LINDA , ZEHR ROBIN
Published: July 2006

Thirty‐five patients were randomized to receive either the Medtronic 6500 or one of two braided multifilament temporary pacing leads in the atrium following open heart surgery. Sensing performance was judged by amplitude, slew rate, and the proportion of patients with an adequate sensing threshold. Pacing performance was assessed with measures of impedance, threshold voltage, current, and energy. The Medtronic 6500 demonstrated superior sensing and lower energy consumption compared to braided multifilament leads. This type of lead may offer advantages when using atrial synchronous temporary pacing systems.
The Effect of Left Ventricular Intracavitary Volume on the Unipolar Electrogram
Authors: BELZ MICHAEL K. , WISE ROBERT M. , HSIA PENG‐WIE E. , COHEN NERI M. , ALLEN CYNTHIA A. , DAMIANO RALPH J.
Published: July 2006

In order to examine the effects of ventricular distention on the unipolar electrogram (UEG), an isolated rabbit heart modified Langendorff preparation was utilized. Left ventricular (LV) volume was adjusted using ionically permeable (PB = 9 hearts) or ionically impermeable balloons (IB = 4 hearts). LV UEGs, LV end‐diastolic pressure (EDP), and LV minor axis dimension (MAD), as measured by ultrasonic transducers, were recorded. Three hundred twenty‐five eiectrograms were digitized and analyzed with customdesigned software, In the PB group, a significant inverse linear relationship was found between UEG amplitude and changes in MAD (P < 0.0001). For each animal, this relationship had an R value > 0.8 and a P value < 0.0001. There was also a significant inverse linear relationship between UEG slope and changes in MAD (P < 0.01). UEG amplitude and slope also exhibited a significant inverse relationship to changes in LV EDP, which were best described by a third order polynomial function. In the IB group, no significont relationship was found between either UEG amplitude or slope and MAD or EDP. In this study, intracavitary volume exerted a profound and significant influence on UEG amplitude and slope. This effect was due to increases in conductive intraventricular volume and not to myocardial stretch
Serum Electrolytes and Catecholamines After Cardioversion From Ventricular Tachycardia and Atrial Fibrillation
Authors: SALERNO DAVID M. , KATZ ADRIANA , DUNBAR DAVID N. , FJELDOS‐SPERBECK KARIN
Published: July 2006

We have observed hypokalemia after cardioversion from spontaneous out‐of‐hospital ventricular fibrillation and induced ventricular tachycardia. To test the hypothesis that the hormone response to the hemodynamic stress of the arrhythmia initiated the change in potassium, we compared the electrolytes and hormones in three groups of patients. We observed a decrease in serum potassium and magnesium after cardioversion from ventricular tachycardia induced by programmed Stimulation but not after normal programmed stimulation of the ventricle or after cardioversion from stable atrial fibrillation. These changes were preceded first by a rise in norepinephrine and epinephrine then a rise in glucose, followed by a rise in insulin. The stimulus for these changes was probably the hypotension associated with ventricular tachycardia. The sequence of changes suggests that the decrease of potassium and magnesium after ventricular tachycardia was due to a shift of the electrolytes into cells related to the insulin‐mediated movement of glucose from the blood into cells.
Left Ventricular Transvenous Electrode Dislodgement After Mustard Repair for Transposition of the Great Arteries
Authors: KANTOCH MICHAL J. , McKAY ROXANE , TYRRELL MICHAEL J.
Published: July 2006

An 11‐year‐old girl who underwent Mustard's operation for complete transposition of the great arteries in infancy, developed Mobitz type II second‐degree AV block 81/2 years later. A transvenous, active fixation left ventricular lead was inserted and connected to a rate responsive pacemaker. Two years later the lead dislodged due to the child's growth. A new active fixation electrode was positioned in the left ventricle below the pulmonary valve, leaving an electrode loop in the ventricle. Such an approach may prevent lead dislodgement due to growth after intraatrial repair for transposition of the great arteries, but regular radiological or echocardiographic follow‐up of lead position is recommended in these patients.
Efficacy of Type 1C Antiarrhythmic Agents for Treatment of Resistant Atrial Fibrillation
Authors: GREY ELIZABETH , SILVERMAN DAVID I.
Published: July 2006

In order to determine the efficacy of type lC agents (flecainide, encainide, propafenone) in patients with atrial fibrillation who have failed to maintain sinus rhythm with type 1A agents (quinidine, procainamide, disopyramide), 147 patients, that were admitted into the John Dempsey Hospital with new or recurrent atrial fibrillation between 1987–1991, were studied retrospectively. Out of the total, 29 patients converted spontaneously to sinus rhythm, 14 patients were left in atrial fibrillation, and 104 patients were given a type 1A antiarrhythmic. Sixty‐five of these patients remained in sinus rhythm (54% converted on drug alone, 46% required electrical cardioversion) for at least 6 months. Of the remaining 39 patients, 28 were given a type 1C antiarrhythmic; 13 were successfully converted (61% chemical, 39% electrical) to and remained in sinus rhythm for at least 6 months; the remaining 15 either failed to convert or reverted to atrial fibrillation. New onset atrial fibrillation had a significantly lower incidence of congestive heart failure (10%) than recurrent atrial fibrillation (33%; P < 0.01). No differences in digoxin, beta blocker use, or other clinical characteristics were seen either between type 1A or type 1C successes or failures. Similarly, echocardiographic dimensions did not predict success or failure with either class of agent. In conclusion, type lC antiarrhythmics for suppression of recurrent atrial fibrillation represent a reasonable therapeutic alternative for suppression of atrial fibrillation in patients who have failed type lA agents. Prognostic factors predicting success or failure remain undetermined.
Return to Arc Welding Following Defibrillator Implantation
Authors: EMBIL JOHN M. , GEDDES JOHN S. , FOSTER DARLENE , SANDEMAN JEFE
Published: July 2006

A male arc welder who was fitted with an impianfabie defibrillator wished to return lo his former employment. Device testing and ambient magnetic field measurements were performed at his place of work. During welding, artifacts were seen on the intracardiac electrogram but there was no resulting disturbance of sensing function. Measured field strengths were too low to result in device inactivation. The patient resumed his work without incident. This appears to be the first reported case of a patient with an implanlable defibrillator returning to this “electrically hostile” environment following thorough screening.
A Randomized Comparison of a Bipolar Steroid‐Eluting Electrode and a Bipolar Microporous Platinum Electrode: Implications for Long‐Term Programming
Authors: GILLIS ANNE M. , ROTHSCHILD JOHN M. , HILLIER KAREN , FUDGE WILMA , KIESER TERESA M. , MAITLAND ANDREW
Published: July 2006

Differences in acute and chronic pacing thresholds were compared in patients receiving either the Medtronic Model 4004 steroid‐eluting lead or the Medtronic Model 4012 microporous platinum lead. Patients (n = 35) were randomized at the time of implant to receive either a steroid‐eluting (n = 17) or a microporous (n = 18) lead. Pacing thresholds were determined within 24 hours and at 2, 4, 6, 12. 24, and 52 weeks postimplant. By 2 weeks postimplant. pacing thresholds measured at 0.8, 1.6, 2.5, 3.3, and 4.2 V were significantly lower in the steroid lead group compared to the microporous Jead group (P < 0.05). At 24 weeks, the voltage threshold at 0.3 msec was 0.8 V in 88% of patients with a steroid lead whereas this threshold was only observed in 33% of patients with the microporous lead (P < 0.01). At 52 weeks the pacing energy measured at 1.6 V, twice pulse duration threshold, was significantly lower in the steroid lead group (0.81 ± 0.59 μJ) compared to the microporous lead group (1.25 ± 0.60 μJ, P < 0.05). Thirteen patients in the steroid lead group and 9 patients in the microporous lead group have been programmed at a pulse amplitude of 1.6 V since the 24‐week follow‐up visit. These patients have been followed for a minimum of 6 months without documented failure to capture. This study shows that pacemaker/lead systems with stable chronic low thresholds can be safely programmed to low pulse amplitude settings. This practice will prolong the longevity of pulse generators.
Effects of Coronary Artery Bypass Grafting on Ventricular Arrhythmias: Results with Electrophysiological Testing and Long‐Term Follow‐Up
Authors: MANOLIS ANTONIS S. , RASTEGAR HASSAN , ESTES N.A. MARK
Published: July 2006

Myocardial revascularization was performed in 56 patients with coronary artery disease who presented with ventricular tachycardia (VT) (n = 39) or ventricular fibrillation (n = 17). There were 46 men and 10 women, aged 65 ± 10 years. Three vessel (n = 42) or left main disease (n = 4) was present in 82%. Left ventricular ejection fraction averaged 36%± 11%. Electrophysioiogical studies were performed preoperatively in all patients; 50 (89%) had inducible ventricular arrhythmias. Sustained monomorphic VT was induced in 40 patients (cycle length 284 ± 61 msec). Reproducible symptomatic nonsustained VT was induced in four patients and ventricular fibrillation in six patients, while six patients had no inducible arrhythmia. Preoperatively the patients with inducible VT failed 3.3 ± 1.2 drug trials during electrophysiological studies. In addition to coronary bypass, 22 patients also received an automatic implantable cardioverter defibrillator (ICD), 26 patients received prophylactic ICD patches, and 1 patient had resection of a false aneurysm. There were no perioperative deaths. Postoperative electrophysiological studies were performed in all 56 surgical survivors. Ventricular tachyarrhythmia could not be induced in the six patients who had no inducible VT preoperatively and in 13 of 40 (33%) with preoperatively inducible sustained VT or in 19 of 50 (38%) patients with any previously inducible ventricular arrhythmia, thus a totaJ of 25 patients (45%) had no inducible VT postoperatively. Of the remaining, 11 patients were treated with antiarrhythmic drugs alone, 11 had already received an ICD (combined with drugs in 7), and another 9 received the ICD postoperatively (combined with drugs in 4). At a mean foJJow‐up of 28 ± 21 months there were 11 deaths (20%): 2 sudden, 5 nonsudden cardiac, and 4 noncardiac deaths. There were 16 nonfatal VT recurrences (29%): 14 among patients with persistently inducible arrhythmias, and onJy 2 among those with no inducible arrhythmia postoperatively (P = 0.004); 13 occurred in patients with an ICD (P = 0.01). Thus among these patients with malignant ventricular arrhythmias who underwent revascuJarization, 45% had no inducible arrhythmia postoperatively with 33% of those with preoperatively inducible sustained VT apparently rendered noninducible by revascularization, while the majority (70%) remained free of major arrhythmic events during long‐term follow‐up. We conclude that myocardial revascularization alone can result in no ventricular arrhythmia induction in selected patients with VT inducible prior to surgery. Long‐term follow‐up of such patients indicates a low sudden death and arrhythmia recurrence rate. Furthermore, in patients with persistently inducible ventricular tachyarrhythmias after coronary revascuJarization, the sudden death rate is low despite a high frequency of nonfatal arrhythmia recurrence when antiarrhythmic medications are guided by programmed stimulation or an ICD is used.
Importance of an Individually Programmed Atrioventricular Delay at Rest and on Work Capacity in Patients with Dual Chamber Pacemakers
Authors: FRIELINGSDORF JÜRGEN , GERBER ANDREAS E , DÜR PETER , VUILLIOMENET/ ANDRÉ , BERTEL OSMUND
Published: July 2006

Despite higher costs, expenditure, and the necessity of repeatedly reprogramming of dual chamber pacemakers, they are increasingly implanted to achieve an optimal work capacity. The influence of an individually programmed atrioventricular (AV) delay hetween 100–250 msec on physical work capacity in 12 patients (68 ± 16 years) with dual chamher pacemakers implanted for high degree AV block was studied. During radionuclide ventriculography at rest the “optimal AV delay” with the maximal achieved left ventricular ejection fraction and the “most unfavorable AV delay” with the least achieved ejection fraction were determined. The ejection fraction at rest with the “optimal AV delay” was 5t ±14% and with the “most unfavorable AV delay” 45 ± 15% (P < 0.001). In random order each patient was assigned to either AV delay and a spiroergometry was performed to determine maximum oxygen uptake (max VO2). which correlates best with work capacity, at a respiratory quotient of 1.1. The results show neither a difference in maximum oxygen uptake (1,262 ± 446 mUmin with the optimal AV delay, 1,248 ± 400 mL/min with the most unfavorable AV delay, respectively) nor in heart rate, blood pressure, exercise duration, maximal workload, and minute ventilation. Thus, an individually programmed AV delay affects left ventricular ejection fraction at rest. In contrast, an individually programmed A V delay has no influence on physical work capacity in patients with a dual chamber pacemaker.
Performance of a 3.2‐mm to 6‐mm Adaptor
Authors: SWEESY MARK W. , FORNEY RICHARD C. , ERICKSON STEVE , BATEY ROBERT L.
Published: July 2006

A study was undertaken to evaluate the performance of a 366–08 adaptor that adapts an in‐line bipolar 3.2‐mm connector to a 6‐mm pulse generator connector. A total of 14 adaptors were implanted in individual patients. Eight of the 14 adaptors failed, an additional failure is probable. Tbe average follow‐up time was 32.1 months. The most likely cause of failure was the spring‐loaded mechanism of the adaptor, which fatigues with time. All eight of the documented failures presented with loss of capture and were accompanied by increased measured lead impedances. In addition, some failed systems demonstrated loss of sensing. As a result, prophylactic replacement of ventricular lead systems incorporating this adaptor would be advisable. Otherwise, more frequent monitoring with lead impedance measurements may suffice.
Effect of Biphasic Waveform Pulse on Endocardial Defibrillation Efficacy in Humans
Authors: NEUZNER JOERG , PITSCHNER HEINZ FRIEDRICH , HUTH CHRISTOF , SCHLEPPER MARTIN
Published: July 2006

Several clinical studies have proved increased defibrillation efficacy for implantable cardioverter defibrillators with biphasic pulse waveforms compared to monophasic pulse waveforms. This difference in defibrillation efficacy depends on the type of defibrillation lead system used. The influence of biphasic defibrillation pulse waveforms on the defibrillation efficacy of purely endocardial defibrillation lead systems has not yet been sufficiently examined, we, therefore studied 30 consecutive patients with drug refractory ventricular tachyarrhythmias during the implantation of a cardioverter defibrillator. After implanting an endocardial “integrated” sensing/defibrillation lead we performed a prospective randomized comparison of the defibrillation efficacy of monophasic and biphasic defibrillation waveform pulses. For endocardial defibrillation with the biphasic waveform the mean defibrillation threshold was 12.5 ± 4.9 joules and for the monophasic waveform 22.2 ± 5.6 joules (P < 0.0001). There was a decrease in the required defibrillation energy of biphasic defibrillation in 29/30 patients. Thus considering purely endocardial defibrillation a statistically significant and clinically relevant increase in defibrillation efficacy can be demonstrated for biphasic defibrillation waveform pulses.
Role of Antitachycardia Pacing in Patients with Third Generation Cardioverter Defibrillators
Authors: TRAPPE HANS‐JOACHIM , KLEIN HELMUT , KIELBLOCK BIRGIT
Published: July 2006

The most effective antitachycardia pacing (ATP) mode is still a matter of debate. Randomized prospective testing of 3 different ATP modes was performed in B5 patients (pts) prior to and after cardioverter Defibrillator implantation (Ventak PHx 36 pts, Cadence V 100 29 pts). All 3 ATP modes included 4 stimulation attempts with 4–7 adaptive scanning burst pulses. Adaptive burst coupling interval was 75% in mode A, 81% in mode B and 69% in mode C. Autodecremental scanning within bursts was 8 msec in all, decremenial scanning between bursts was 8 msec in modes B and C. Each ATP mode had to be tested 3 times; all 3 ATP modes were randomly applied to each pt. During preoperative testing 91 of 133 VT episodes (68%) could be terminated by ATP. Termination was achieved in 68% with mode A, 68% with mode B and 73% with mode C, During predischarge testing, 251 VTs were induced and ATP was successful in 147 VTs (59%). Termination rate was 56% with mode A, 68% with mode B and 50% with mode C. During the mean follow‐up of 12 months, 2301 arrhythmia episodes (AE) occurred. ATP was performed in 2097 AE (91%) and successful in 1920 AE (92%). Acceleration of VT occurred in 65 AE (3%) and unsuccessful ATP was observed in 112 AE (5%). It is concluded that ATP in general is highly effective in pts with sustained VT. None of the tested ATP modes, however, proved to be superior to the other.
Evaluation of Outpatients Experiencing Implantable Cardioverter Defibrillator Shocks Associated with Minimal Symptoms
Authors: HAMER MARK E. , CLAIR WALTER K. , WILKINSON WILLIAM E. , GREENFIELD RUTH A. , PRITCHETT EDWARD L.C. , PAGE RICHARD L.
Published: July 2006

Patients receiving minimally symptomatic shocks from their implantable cardioverter defibrillators were studied prospectively using transtelephonic ECC loop monitoring. The time course to the first subsequent shock was evaluated. Twenty‐nine consecutive patients who received a shock preceded by mild palpitations or no symptoms were given a transtelephonic ECG loop monitor and instructed to activate the monitor if a subsequent shock occurred. Kaplan‐Meier analysis was used to quantitate the time to first shock during the study period. The point estimate ± standard error of patients receiving a shock during the study period was 31%± 9% at 30 days, 41%± 9% at 60 days, and 60%± 9% at 120 days. The ECG was successfully transmitted in 7 of 13 patients who had shocks in the 60‐day monitoring period, and demonstrated inappropriate shocks in 6 of 7. Determination of the cause of shock led to a change in subsequent management in all 7 patients. We conclude that the incidence of inappropriate shocks may be higher than estimated previously in patients with minimal symptoms prior to the shock. There are thousands of patients with implantable cardioverter defibrillators that have no storage function for treated tachycardias; transtelephonic ECG loop monitoring can determine the cause of implantable cardioverter defibrillator discharge in these patients, and the diagnosis is invaluable in their management.
Should Electrophysiological Studies Be Performed in Asymptomatic Patients Following Myocardial Infarction? A Pragmatic Approach
Authors: VISKIN SAMI , BELHASSEN BERNARD
Published: July 2006

We analyze the arguments commonly afforded by advocates of electrophysiological evaluation for patients with recent myocardial infarction. These argu ments are: (1) electrophysiological evaluation is useful for risk stratification of infarct survivors; and (2) it may be used for guiding drug therapy or to identify a group of asymptomatic patients who will benefit from implantation of an automatic cardioverter defibrillator. A positive electrophysiological study is ap parently the single best predictor of future arrhythmic events in infarct survivors. However, several nonin‐vasive tests combined may provide just as valuable information. Therefore, electrophysiological evalua tion should not be advised, to the majority of infarct survivors, for the mere purpose of risk stratification. Nevertheless, electrophysiological evaluation may be proposed to patients with impaired left ventricular function or high grade ventricular arrhythmias. Patients without inducible arrhythmias have a good prog nosis and may be spared the risk of long‐term treatment with antiarrhythmic drugs. However, before proceeding with invasive electrophysiological evaluation, both physician and patient should ask them selves if they are willing to go ahead with defibrillator implantation in case sustained monomorphic ventricular tachycardia is induced.
Influence of Filtering Techniques on the Time‐Domain Analysis, Diagnosis, and Clinical Use of Signal‐Averaged Electrocardiogram
Authors: HNATKOVA KATERINA , KULAKOWSKI PIOTR , STAUNTON ANNE , KEELING PHILLIP , YI GANG , CAMM A JOHN , MALIK MAREK
Published: July 2006

In order to investigate the effect of different filtering techniques on the time‐domain analysis of signal‐averaged electrocardiogram (SAECG), recordings of 1,192 subjects were analyzed using Butterworth and Del Mar filters, both set at 40–250 Hz high and low pass frequencies. The recordings were taken from six clinically defined groups: (a) survivors of acute myocardial infarction (n = 553); (b) patients with sustained symptomatic postinfarction ventricular tachycardia (n = 89); (c) patients with hyperthropic cardiomyopathy (n = 219); (d) patients with dilated cardiomyopathy (n = 76); (e) direct relatives of patients with dilated cardiomyopathy (n = 170); and (f) normal healthy volunteers (n = 85). The study investigated differences between the SAECG results reported with both filters in three individual aspects: (l) numerical values of individual time‐domain SAECG variables; (2) differences in SAECG findings of patients with postinfarction ventricular tachycardia and pair matched patients with uncomplicated follow‐up after acute infarction; and (3) the power of SAECG findings to predict high risk of arrhythmic complication (sudden death and/or sustained ventricular tachycardia) among survivors of acute myocardial infarction. Compared with the Butterworth filter, the Del Mar filter led to a systematic difference of + 8% in total QRS duration, was equally powerful in distinguishing between the pair matched patients with and without postinfarction ventricular tachycardia, and was statistically significantly more powerful in identifying those survivors of acute infarction who were at high risk of arrhythmic complications. The study concludes that the use of different filters may produce discordant results of SAECG analysis. Normal and abnormal values for various types of SAEGG recording and analysis have to be established individually for different equipment and different software settings. These optimal cut‐offs of SAEGG variables should also take into account the clinical characteristics of patient groups.
Intra‐His Bundle Block Corresponds with Interruption of the Branching Portion of the His Bundle
Authors: NAKAZATO YUJI , NAKATA YASURO , TOKANO TAKASHI , YASUDA MASAYUKI , OHNO YASUHIKO , HISAOKA TERUHIKO , SUMIYOSHI MASATAKA , OGURA SHUNSUKE , YAMAGUCHI HIROSHI , OHI HIROO , SHIMIZU MITSURU , KAWAI SACHIO , OKADA RYOZO
Published: July 2006

We compared His‐bundle electrograms with pathological findings of the atrioventricular conduction system in four patients with complete atrioventricular intra‐His block with narrow QRS complexes on ECG. Split His electrograms were recorded at the time of electrophysiological study. The patients died from noncardiac causes at 10 days, 1 year, 4 years, and 9 years, respectively, after the pacemaker implantation. Serial sections through the atrioventricular conduction system revealed strictly localized more than 50% reduction of conducting cells replaced by fibrosis at the branching portion of His bundle. The proximal portions of the bundle branches also exhibited decrease of the conducting cells showing a rough positive relation with the patient's age. Therefore, we considered that the H1 spikes seen on His‐bundle electrograms originated from the penetrating portion of His, which was virtually intact in our cases, and that the H2 spikes originated from the right side of the distal branching portion of His.
Radiofrequency Catheter Ablation of the Atrioventricular Junction by a Supravalvular Noncoronary Aortic Cusp Approach
Authors: CUELLO CARLOS , HUANG SHOEI K. STEPHEN , WAGSHAL ALAN B. , PIRES LUIS A. , MITTLEMAN ROBERT S. , BONAVITA GREGORY J.
Published: July 2006

Radiofrequency catheter ablation of the atrioventricular janction is usually achieved from either the right or left atrioventricular junction. We describe a new approach in which the atrioventricular junction was successfully ablated from the supravalvular region of the noncoronary cusp of the aortic valve in an unusual patient in whom conventional approaches were unsuccessful.