bluuebunny/crossref_metadata_2025 huggingface dataset:
Pacemaker System Failure and Other Events in Children with Surgically Induced Heart Block
Authors: McGRATH LYNN B. , GONZALEZ‐LAVIN LORENZO , MORSE DRYDKN P. , LEVETT JAMES M.
Published: July 2006

Of 1,193 consecutive pediatric (< 18 years) patients undergoing intracardiac repair from 1975 to 1984, 38 (3.2%) developed surgically induced complete heart block and were treated by permanent pacemaker implantation. Anomalies included complete atrioventricular septal defect = 9 (24%), simple ventricular septal defect = 9 (24%), atrioventricular discordant connection = 8 (212), tetralogy of Fallot = 7 (182), and other complex anomalies = 5 (13%). There were no hospital deaths, follow‐up was 100% complete. There were six late deaths = 16%. Actuarial survival was 79 + 9% at 10 years. None of the late deaths were related to disturbance of cardiac rhythm or pacemaker system failure. Twelve patients (32%). required 27 reoperations for various types of pacemaker system failure. Indications for reoperation included: lead failure (44%). Pulse generator failure (44%), and wound sepsis (12%). Actuarial freedom from any pacemaker related reoperation was 50 + 36% at 46 months and 25 + 15% at 96 months. Only first reoperation was found to be an incremental risk factor for subsequent reoperation (p = 0.03). Surgical heart block has been neutralized as a risk factor for hospital death after repair of congenital cardiac defects. The risk of the development of surgical heart block now approaches zero, as indicated by a decreased incidence (I of 401 = 0.25%) in our institution from 1985 to 1987, as compared to the era 1975 to 1984 (p = 0.001).
Normal Myocardial Enzymes and Normal Echocardiographic Findings During Noninvasive Transcutaneous Pacing
Authors: MADSEN JAN KYST , PEDERSEN FLEMMING , GRANDE PEER , MEIBOM JØRGEN
Published: July 2006

Noninvasive transcutaneous pacing was performed for 30 minutes in 10 healthy volunteers. The pace rate was from 85 to 115 min, 1 and the threshold for pacing was from 38 to 70 mA, median 59 mA. Echocardiography before and during pacing showed no changes in left ventricular end‐diastolic diameter, in fractional shortening nor in contraction pattern. Also, hood pressure remained unchanged. Blood samples for determination of myoglobin, creatine phosphokinase, creatine kinase MB and lactate dehydrogenase were drawn prior to pacing and 1,2,3,4,6,8 and 24 hours after pacing. The serum concentrations were the same before and after pacing for all enzymes and myoglobin. We conclude that non‐invasive transcutaneous pacing for 30 minutes causes no muscular or myocardial injury and that the left ventricular function remains normal.
Therapeutic and Diagnostic Benefits of Intentional Crosstalk Mediated Ventricular Output Inhibition
Authors: LEVINE PAUL A. , VENDITTI FERDINAND J. , PODRID PHILLIP J. , KLEIN MICHAEL D.
Published: July 2006

Ventricular output inhibition due to crosstalk is generally considered unsafe and something that should be avoided. Special circuits have been incorporated in some dual chamber pacing systems to absolutely prevent this from happening. However, in patients with intact atrioventricular conduction, crosstalk mediated ventricular output inhibition can be beneficial to the evaluation and management of the patient. Utilizing this technique, one can achieve single chamber atrial paced rates which greatly exceed the rates allowed by lower rate limit programming to facilitate an assessment of the integrity of AV nodal conduction and to both convert and suppress some pathological tachyarrhythmias. The methods of achieving crosstalk and its utilization in four patients is discussed in this report.
The Usefulness of Head‐Up Tilt Testing and Hemodynamic Investigations in the Workup of Syncope of Unknown Origin
Authors: ABI‐SAMRA FREDDY , MALONEY JAMES D. , FOUAD‐TARAZI FETNAT M. , CASTLE LON W.
Published: July 2006

To enhance the clinical evaluation of patients suffering from recurrent syncope of unknown origin, the integrity of mechanisms controlling blood pressure was examined in 151 patients utilizing a screening tilt test. Ninety‐eight patients had an abnormal blood pressure and/or heart rate response to tilt testing, including provoked syncopal attacks in 63 patients. Whenever indicated, the screening tilt test was followed by blood volume and hemodynamic determinations, as well as autonomic nervous system testing to identify contributing pathophysiological abnormalities (hypovolemia, venous pooling, autonomic dysfunction). Detailed analysis of this battery of tests allowed us to conclude that: (1) The tilt test is commonly a provocative tool in the workup of patients with recurrent syncope due to vasovagal ‐ vasodepressor reactions and other abnormalities of blood pressure regulation; (2) Its usefulness is augmented by associated hemodynamic and blood volume evaluations; (3) The identification of contributory pathophysiological mechanisms of blood pressure control facilitates specific therapeutic interventions.
Electrocardiographic Manifestations of the Rapid Recharge Function of Pulse Generators After Sensing
Authors: BAROLD S. SERGE , KULKARNI HEMA , THAWANI A.J. , HAUSER ROBERT G. , DUFFIN EDWIN , BUYSMAN JOHN R.
Published: July 2006

In this report, we present our observations in three patients with Medtronic Spectrax™ VVI pulse generators that exhibited unususally clear electrocardiographic artifacts, due to the rapid recharge function upon sensing. Although many contemporary pulse generators contain rapid recharge circuits operative after the delivery of a pacemaker stimulus, only certain Medtronic Spectrax pulse generators also possess a rapid recharge capability after sensing. Rapid recharge upon sensing may produce electrocardiographic deflections that should not be misinterpreted as pacemaker malfunction.
Pacemaker Syndrome with AAI Rate Variable Pacing: Importance of Atrioventricular Conduction Properties, Medication, and Pacemaker Programmability
Authors: DEN DULK KAREL , LINDEMANS FRED W. , BRUGADA PEDRO , SMEETS JOEP L.R.M. , WELLENS HEIN J.J.
Published: July 2006

A patient who received an AAI Activitrax rate variable pacemaker for treatment of symptomatic sinus bradycardia is described, disopyramide prolonged the anterograde effective refractory period of the fast conducting atrioventricular (AV) nodal pathway to such an extent, that conduction switched to the slow AV nodal pathway at low atrial pacing rates. This gave rise to symptoms of the pacemaker syndrome during moderate exercise because the paced atrial event was conducted with a long, spike to Q interval with occurrence of the paced atrial event just after the preceding QRS complex. A change of medication solved this problem. Programming a bipolar electrode configuration avoided sensing of far‐field QRS signals with the associated problems of resetting the basic pacing interval as well as the upper rate interval. AAI rate variable pacing requires careful evaluation of AV conduction properties, AV conduction intervals as well as the influence of medication to be given. The use of multiprogrammable pacemakers with marker channel capability will significantly facilitate the understanding and resolution of anomalous behavior.
Theoretical Evaluation of the Rosenblueth Hypothesis
Authors: MALIK MAREK , WARD DAVID , CAMM A. JOHN
Published: July 2006

Rosenblueth's hypothesis states that atrioventricular (AV) nodal conduction delay and Wenckehach periodicity of AV transmission are not due to overall decremental conduction within the AV node but are due to a single step delay which is caused by a special element or layer of the AV nodal tissue. This paper discusses some theoretical considerations which allow detailed evaluation of the original hypothesis. Two artificial conduction structures which incorporate the Rosenblueth phenomenon are presented and tested by theoretical experiments that consider the potential of these structures to produce (a) basic pattern of Wenckebach periods, (b) decremental shortening of RR intervals during Wenckebach periods. These experiments are also employed to test whether or not the Rosenblueth concept can be used to explain (c) appropriate dependence of AV conduction changes on the prematurity of atrial depolarizations, and of (d) alternating cycle lengths such as may be seen with atrioventricular reentrant tachycardia. The results of the theoretical considerations show that the original concept of the Rosenblueth hypothesis is sufficient to explain (a) but it cannot be used for realization of(b), (c) and (d). A modification of the original concept complying with both (a) and (b) is proposed. This modified structure can also reproduce (c), but not simultaneously with (b). The experiments show that anisotropy of intra AV nodal conduction may create an electrophysiological mechanism of single‐step delay. Different anisotropic conduction structures have to be considered to reproduce phenomenon (d).
Electrical Ablation with a Balloon Electrode Array: Chronic Electrophysiologic Response
Authors: HARRIS LOUISE , MICKLEBOROUGH LYNDA L. , SHAIKH NISAR , PARSON IAN , DOWNAR EUGENE , CHEN THOMAS , GRAY GORDON
Published: July 2006

An intraoperative endocardial array of electrodes which permits simultaneous recordings from multiple sites in the intact ventricle is currently in clinical use and has provided the opportunity for exploring electrical ablation as an alternative to standard surgical ablative techniques requiring a ventriculotomy. A variation of the electrical ablative procedure adapted for this intraoperative purpose was studied in seven dogs to determine its long‐term electrophysiologic and structural effects on ventricular myocardium. With the dogs on cardiopulmonary bypass, a mesh‐covered latex balloon was introduced into the left ventricle via an atriotomy. Five damped sinusoidal discharges (4 of 200 J per 2 electrodes, one of 100 J to the remaining electrode) were delivered to nine silver bead electrodes sutured at 1 cm intervals onto the mesh and arranged in a 2 × 2 cm2 array. At 5–8 weeks following the ablation, no ventricular arrhythmias could be induced in any of the dogs using standard stimulation techniques. The scar produced by the ablation consisted of dense fibrous tissue, and was well demarcated from surrounding normal myocardium. Cellular electrophysiology confirmed that no action potentials could be recorded within the scarred area while at distances of 1 mm from the scar border, normal responses could be elicited from both muscle cells and Purkinje fibers. The adaptation of the described electrical ablative procedure produces an electrophysiologically inert scar.
Physiological Sensitivity of Respiratory‐Dependent Cardiac Pacing: Four‐Year Follow‐Up
Authors: ROSSI PAOLO , PRANDO MARIA DOMENICA , MAGNANI ANDREA , AINA FRANCO , ROGNONI GIORGIO , OCCHETTA ERALDO
Published: July 2006

Clinical and physiological data on long‐term follow‐up of 143 patients with respiratory‐dependent pacemakers (RDP3) are reported; 121 patients received ventricular (VVI‐RD) and 22 patients atrial (AAI‐RD) respiratory‐dependent stimulation. Functional evaluation was based on the exercise testing (130 pts) with oxygen uptake V̇O2, ventilation, ECG and arterial pressure monitoring and the dynamic Holter electrocardiogram (95 pts). In each patient, the stimulation rate curve selected was that which produced the best work tolerance and moved the anaerobic threshold to the right. Respiratory levels were assessed by telemetry verifying proper sensing of tidal volume variations and absence of interference and artefacts. In patients with VVIR or AAIR stimulation, exercise tolerance, oxygen uptake and anaerobic threshold increased significantly in comparison with VVI or AAI pacing respectively. The physiological sensitivity of the stimulation system (i.e., a linear relationship of the pacing rate with metabolic requirements) was excellent (up to exhaustion) in 70%, very good (up to anaerobic threshold) in 20% and erratic (no relationship between pacing rate and VE/V̇O2) in 10% of patients. In dynamic electrocardiographic monitoring, the automatic pacing rate was always predominant during the night and during rest periods; the pacing rate increased properly with daily activity; myopotential inhibition (none longer than 3,500 ms) was observed in 38 patients, but without subjective complaints. The incidence of the RDP3 malfunction was less than 8%; it may have stemmed from the pacing system itself, or from other clinical conditions. Oversensing of impedance system pulses has not been recorded in the last 3 years. Partial respiration undersensing results from incorrect accessory lead position, pulmonary emphysema, marked obesity or other causes. Respiratory sensing becomes erratic at the anaerobic threshold point in such patients, but functions well at submaximum exercise levels. In patients with left ventricular failure, exercise tolerance was improved by setting a lower ratio between the pacing rate and respiration, which prevented the occurrence of excessive pacing rates.
Atrioventricular Nodal Conduction and Refractoriness Following Abrupt Changes in Cycle Length
Authors: SHENASA MOHAMMAD , LACOMBE PIERRE , GODIN DIANE , SADR‐AMELI MOHAMMAD‐ALI , FAUGÈRE GERARD , NADEAU RÉGINALD A.
Published: July 2006

The properties of the atrioventricular (AV) nodal conduction and effective refractory period in man are generally evaluated at a constant basic cycle length (CL) and, in most cases, they demonstrate an inverse relationship to the drive cycle. The response of AV node to abrupt change in CL is less defined. We therefore studied the effects of abrupt changes in CL on AV nodal conduction time and refractoriness in 18 patients. AV nodal conduction time, and effective and functional refractory periods were measured during; (1) a constant long CL. (2) a constant short CL. and (3) after an abrupt increase in CL just prior to the introduction of extrastimuli. In 10 of the 18 patients a constant long CL of 600 ms, a constant short CL of 400 ms and a sudden short‐to‐long change in CL (400 to 600 ms) were tested. AV nodal conduction times (A2H2) were measured at the shortest and longest comparable A1A2 intervals. The mean value of the shortest A2H2 intervals for constant CL of 600 ms was 144 ± 18 ms; for a constant CL of 400 ms it was 162 ± 17 ms: after a sudden short‐to‐long change in CL (400 to 600 ms) it was 142 ± 14 ms. The mean value of the longest A2H2 intervals at a constant CL of 600 ms was 185 ± 18 ms; at a constant CL of 400 ms it was 236 ± 26 ms (p < 0.01) and after a short‐to‐long change in CL (400 to 600 ms) 199 ± 21 ms. AV nodal effective refractory periods measured at the same three CLs had mean values of 279 ± 13 ms; 300 ± 15 ms and 294 ± 13 ms, respectively. Similar results were obtained when other CLs such as 700 to 900, 500 to 900, and 400 to 700 ms were tested. The data suggest that after abrupt short‐to‐long changes in CL, AV nodal function curves shift from long constant CL toward short constant CL as the coupling intervals decrease, indicating a cumulative pattern. Although the return to baseline conduction time after the fast basic rate is known to be slow, the limitation of this effect to the very early premature beat in the human has not been reported previously.
Mesothelioma of the AV Node: Potential Utility of Pacing
Authors: STRAUSS WILLIAM E. , ASINGER RICHARD W. , HODGES MORRISON
Published: July 2006

Mesothelioma of the atrioventricular node are rare benign tumors with well‐described potential for resulting in sudden death. The presentations have varied: the majority of patients have been predominantly female aged 15 to 40, dying suddenly; however, other patients have had documented heart block for many decades and a noncardiac cause of death. A 19‐year‐old female expired after presenting with ventricular fibrillation and was subsequently discovered to have a mesothelioma involving the AV node. Although high degree heart block is present in many patients, most episodes of sudden death probably are secondary to ventricular tachyarrhythmias. Either form of dysrhythmia may potentially benefit from ventricular pacing.
Entrainment of Ventricular Tachycardia in Postoperative Tetralogy of Fallot
Authors: KREMERS MARK S. , WELLS PETER J. , BLACK WILLIAM H. , SOLODYNA MARTHA A.
Published: July 2006

The mechanism of ventricular tachycardia (VT) in postoperative tetralogy of Fallot has been ascribed to both reentry and triggered automaticity. We performed electrophysiologic studies on a patient with this condition and induced sustained uniform ventricular tachycardia by programmed extrastimulation. Pacing during the tachycardia at multiple cycle lengths from the right ventricular apex (RVA) and outflow tract (RVOT) produced constant but progressive fusion between the paced and tachycardia QRS. With termination of pacing, the last captured complex was unfused but coupled at the paced cycle length and then the tachycardia resumed at its intrinsic rate. Therefore, the VT was entrained. In addition, an area of slow conduction between the RVOT and RVA was demonstrated. These findings support a reentrant mechanism of this arrhythmia.
Influence of Ventricular Fibrillation Duration on Defibrillation Energy in Dogs Using Bidirectional Pulse Discharges
Authors: ECHT DEBRA S. , BARBEY JEAN T. , BLACK JAMES N.
Published: July 2006

The automatic implantable defibrillator device typically discharges 5–30 seconds after detection of ventricular fibrillation. To investigate the importance of the duration of ventricular fibrillation on defibrillation, the effects of ventricular fibrillation durations of 5, 15, and 30 seconds on the energy requirements for successful internal defibrillation were compared in 15 dosed chest dogs with internal electrodes. The electrode configuration utilized a transvenous right heart catheter with two electrodes and a precordial subcutaneous patch electrode, with a single bidirectional pulse discharged between the distal catheter electrode and the proximal catheter and patch electrodes. Curves of energy vs. percentage of successful defibrillation were constructed and logistic regression was used to derive 90% and 50% successful energy doses (ED90 and ED50). The mean ventricular fibrillation activation interval just prior to defibrillation was determined from discrete RV endocardial electrograms. Four dogs died during testing, all because of inability to defibrillate after 30 s of ventricular fibrillation. In the remaining 11 dogs, the ED90 increased from (mean ± SD) 27 ± 13J at 5 s to 41 ± 14J at 30 s (p < .01). The mean ventricular fibrillation activation interval decreased from 107 ± 21 ms at 5 s to 95 ± 18 ms at 30 s (p < .01). In conclusion, the energy required for internal defibrillation in dogs using this electrode configuration increases with longer durations of ventricular fibrillation, and is associated with more rapid ventricular fibrillation activation intervals.
Concealed Paroxysmal Atrioventricular Block: Diffuse Congenital Atrioventricular Conduction System Disorder with Nonpropagated His Bundle Depolarizations
Authors: DICK MACDONALD , BEEKMAN ROBERT H. , KASTEN‐SPORTES CAROL H.
Published: July 2006

A 2 1/2‐year‐old girl with bradycardia and left bundle branch block at birth began to experience “night cries” when deeply asleep. Electrophysiological study demonstrated congenital diffuse atrioventricular conduction disease with concealed paroxysmal atrioventricular block, nonpropagated His bundle depolarizations, severe sinus node abnormality, and a low atrioventricular junctional escape rhythm with probable reciprocation. After pacemaker implant, the “night cries” ceased.
Electrocardiographic Characteristics of the Escape Rhythm in Transient Complete Atrioventricular Block Induced by Transcatheter Electrical Ablation of the Atrioventricular Junction
Authors: LACOMBE PIERRE , LÉVY SAMUEL , METGE MARC , COINTE ROLAND , BRU PAUL , GERARD RAYMOND
Published: July 2006

The electrocardiographic characteristics of spontaneous escape rhythm during complete heart block induced by transcatheter ablation of the atrioventricular junction was prospectively studied in 21 patients by periodically interrupting temporary pacing. The data derived from 13 of these 21 patients, in whom conduction recurred after the procedure, were analyzed. An escape rhythm was present in 12 patients 8.2 ± 5.8 minutes after shock delivery at a cycle length of 1985 ± 974 ms. The escape QRS had a configuration of right bundle branch block with left axis deviation in 9 patients, of right bundle branch block with normal axis in 1, of left bundle branch block with left axis deviation in 2, and 2 distinct morphologies in the remaining patient. After resumption of conduction, the conducted complexes were identical to the escape complexes in six patients, different only in axis in four patients, and different in morphology in two patients. This suggests that in the majority of patients the escape rhythm seen during transient heart block, induced by transcatheter ablation of the atrioventricular junction, presents a right bundle branch morphology with or without a left axis deviation, and most likely originates from an area above, or close to, the site of the anatomical damage.
Computer Simulation of Cardiac Pacing
Authors: ÅHLFELDT H. , TANAKA H. , NYGARDS M.‐E. , FURUKAWA T. , WIGERTZ O.
Published: July 2006

A mathematical model of the cardiac conduction system, including external pacemakers, has been developed. The heart is modeled as a network in which the impulse propagation is described by differential equations; several arrhythmia‐generating mechanisms, such as modulated parasystole, reflection, macro and micro re‐entry and block, can be simulated. Different kinds of pacemaker modes have been incorporated in the model, thus making it possible to simulate the interaction between the heart and the pacemaker. The model can be tuned by the user according to electrophysiological data so that pacemaker programs can be tested under different underlying conditions. During a simulation, the program generates ECG signals and pacemaker diagnostic diagrams. This model can be used for training and testing, and also as a support system when searching for the optimal pacing therapy for a particular patient.
Octapolar Electrocatheter for His Bundle Recording and Sequential Bedside Electrophysiologic Testing
Authors: CINCA JUAN , MOYA ANGEL , BARDAJÍ ALFREDO , FIGUERAS JAIME , RIUS JORGE
Published: July 2006

To reduce the number of electrocatheters required for an electrophysiologic study and to facilitate prolonged monitoring of the electrical properties of the heart, an octapolar electrocatheter was designed and tested in 45 consecutive patients undergoing routine electrophysiologic studies. The electrocatheter introduced into the right ventricle served far: (a) right ventricular pacing; (b) recording of low lateral and low septal right atrial electrograms; (c) recording of the His bundle potential in 39 out of the 45 patients (86%); (d) 24‐hour monitoring of the AV conduction intervals and refractory periods at the patients’ bedsides. The octapolar electrocatheter reduced the number of probes required for studying the mechanisms of reciprocating tachycardia and allowed 24‐hour bedside electrophysiologic monitoring.
Comparison of Unipolar and Bipolar Active Fixation Atrial Pacing Leads
Authors: KAY G. NEAL , EPSTEJN ANDREW E. , PLUMB VANCE J.
Published: July 2006

The purpose of this investigation was to compare the acute pacing and sensing characteristics of a new bipolar active fixation atrial pacing lead with those of a unipolar atrial lead of similar design. Pacing threshold voltage and current, lead impedance, and atrial electrogram amplitude and slew rate were measured at the time of surgery in 28 consecutive patients undergoing DDD pacing system implantation. Eleven patients received a Medtronic 6957J–58 unipolar active fixation atrial lead and 17 patients were given a Medtronic 4016–58 bipolar lead. Both leads are polyurethane‐insulated with the distal electrode being a platinum alloy screw‐helix with a surface area of 8.0 mm2. There were no significant differences in the threshold voltage (1.01 V unipolar versus 1.05 V bipolar) or current (1.93 mA unipolar versus 1.78 mA bipolar) of the two leads. The mean impedance of the bipolar active fixation lead was 618 ohms compared to 479 ohms for the unipolar lead (p = 0.02). The mean amplitude of the atrial electrogram was 4.64 mV for the bipolar lead and 3.11 mV for the unipolar lead (p = 0.02). The atrial electrogram exceeded 5 mV in 10 of 17 patients with the bipolar lead but zero of 11 with the unipolar lead. There was no significant difference in the mean slew rate of the leads (1.09 V./s bipolar versus 0.73 V/s unipolar; p ‐ 0.18). Over a follow‐up period of up to 10 months, all patients remained in either the DDD or DDI modes with no episodes of atrial sensing or pacing failure. Bipolar active fixation atrial leads have pacing characteristics similar to unipolar leads of similar design but may be superior for sensing of the atrial electrogram.
Reassessment of AV and VA Conduction and AV Junctional Reentry in the Normal Dog Heart: The Role of Altered Autonomic Tone
Authors: HUNT GERALDINE B. , ROSS DAVID L.
Published: July 2006

The effects of isoproterenol, atropine, and metoprolol on atrioventricular [AV] and veniriculoatrial (VA) conduction were studied in 30 normal dogs under pentobarbital anesthesia using percutaneously introduced catheters. The inducibility of AV junctional reentry was also assessed before and after drug administration. Resting AV conduction was normal in all dogs, but VA conduction ivas present in only 57%. Isoproterenol facilitated both antegrade and retrograde conduction, with a preferential effect on retrograde conduction. VA conduction was demonstrated after isoproterenol in 91% of dogs. After testing all drugs, VA conduction was demonstrable in at least one study in 97% of dogs. Atropine had less effect than isoproterenol, suggesting that basal vagal tone was not high in this model. Dual AV nodal pathways were detectable in the antegrade direction in four (13%) dogs, and in the retrograde direction in an additional four (13%) dogs. Single AV junctional echoes were inducible with atrial stimulation in one dog with dual antegrade pathways, but were inducible with ventricular stimulation in at least one study in 83% of dogs with intact retrograde conduction. Sustained AV Junctional reentry was never induced before or after drug administration. In conclusion, VA electrical continuity is almost always intact in the normal dog, but its demonstration is significantly modified by the autonomic nervous system. Tsoproterenol has preferential effects on retrograde conduction and may have selective influence on distal AV nodal conduction. Twenty‐six percent of normal dogs have evidence of dual AV nodal pathways. Single AV junctional echoes are inducible with ventricular stimulation in the majority of dogs and are a normal finding. Sustained AV junctional reentry is not inducible in the normal intact dog heart.
Internal Cardiac Defibrillation: Single and Sequential Pulses and a Variety of Lead Orientations
Authors: JONES DOUGLAS L. , KLEIN GEORGE J. , RATTES MAX F. , SOHLA ANAND , SHARMA ARJUN D.
Published: July 2006

A sequential pulse system for internal cardiac defibrillation incorporating catheter and patch electrodes with two current pathways has been shown to reduce defibrillation threshold in comparison to the single pulse technique. The relative advantage of the sequential pulse over the single pulse technique with other lead systems is not known. We compared defibrillation thresholds using sequential and single pulses delivered to a variety of lead orientations with the same electrode surface areas, when possible. Defibrillation threshold totals determined in halothane‐anesthetized open‐chest pigs averaged: For the single pulse shock passed between (1) superior vena cava (SVC) and Jeff ventricular apical patch (LVAJ, 27.2 ± 9.1 joules (J) and (2) LV epicardial patch (IVE) to right ventricular epicardial (RVE) patch leads, 16.5 ± 2.1 J; and for the sequential pulse shock with two pulses passed between: (1) the SVC to RV intracavitary apex (RVAJ and a quodripolar catheter in the coronary sinus to the RVA, 11.6 ± 1.0); (2) the SVC to IVA and the LVE to RVE, 9.6 ± 1.3) and (3) the SVC to RVA and the LVE to RVA, 8.9 ± OA J. Defibrillation thresholds for sequential pulse shocks were all significantly lower than either of the defibrillation thresholds for single pulse shocks (p < 0.001). We conclude that the sequential pulse system provides a substantial reduction in defibrillation threshold over the single pulse regardless of the lead system when the surface area and pulse characteristics are controlled. Sequential pulse technique may be valuable in the design of an implantable automatic defibrillator. Furthermore, the finding that defibrillation thresholds using two intravascular catheters did not differ from other thresholds with sequential shocks suggests that an automatic defibrillator may be implanted in patients without a thoracotomy or sternotomy.
Computer Discrimination of Atrial Fibrillation and Regular Atrial Rhythms from Intra‐Atrial Electrograms
Authors: SLOCUM JANET , SAHAKIAN ALAN , SWIRYN STEVEN
Published: July 2006

Reliable detection of atrial fibrillation from intra‐atrial data is an important requirement for automatic implantable anti‐tachycardia devices. Simultaneous filtered and unfiltered intra‐atrial electrograms were recorded from patients in regular rhythms (12 sinus rhythms and six regular atrial tachycardias) and atrial fibrillation (nine rhythms). Each rhythm was broken down into consecutive 4‐second data segments for analysis by atrial rate calculation, power spectrum analysis and amplitude probability density function generation. Significant differences were found between regular rhythms and atrial fibrillation for atrial rate, for the percentage of the total power in the 4–9 hertz band and for amplitude probability density close to the isoelectric region. There was no overlap for any of these three parameters. For each method of analysis, algorithms were generated to discriminate individual data segments from regular rhythms and atrial fibrillation with high sensitivity and specificity. Comparable results were found when sinus rhythm was excluded from the analysis. Characteristics of intra‐atrial recordings during atrial fibrillation were remarkably similar to previously published reports of intra‐ventricular recordings during ventricular fibrillation. Each of the three methods of analysis may provide an algorithm for accurate detection of atrial fibrillation by anti‐tachycardia devices.
Diagnosis of Atrial Fibrillation Using Electrograms from Chronic Leads: Evaluation of Computer Algorithms
Authors: JENKINS JANICE , NOH KI HONG , GUEZENNEC ALAIN , BUMP THOMAS , ARZBAECHER ROBERT
Published: July 2006

This study compares the performance of three detection algorithms for the recognition of atrial fibrillation in chronic pacing leads. Multiple serial recordings were obtained of wideband and filtered electrograms from chronic atrial and ventricular leads in dogs for a period up to 55 days following implantation. Each dog was recorded in sinus rhythm and induced atrial fibrillation. Four days were chosen for processing: The day of implantation and a day in the first, second or third, and fifth weeks. Three signal processing methods were assessed for performance in detection of atrial fibrillation: software recognition of rate with automatic threshold control, amplitude distribution, and frequency spectral analysis. A software trigger for rate determination was adjusted to thresholds of 10, 20, and 30% of maximum baseline‐to‐peak amplitude. At 10%, a rate boundary anywhere between 420 and 560 beats per minute (bpm) perfectly separated atrial fibrillation from sinus rhythm even though atrial electrograms were contaminated with large QRS deflections and double‐sensing was present. At 20% and 30%, a rate boundary around 300 bpm could be used, but sensitivity and specificity were reduced to 90%. In amplitude distribution analysis, a percent of time within a baseline window provided perfect separation of atrial fibrillation from sinus rhythm. In all cases, the signal was within this window Jess than 43% of the time in atrial fibrillation, and more than 43% in sinus rhythm. In spectral analysis, frequency bands were examined for power content. In the 6 to 30 Hz band atrial fibrillation contained the greater power. Choosing 58% of total power as a discriminant, sensitivity and specificity of atrial fibrillation detection were 100% and 95% respectively.
Sinus Rhythm Mapping in a Canine Model of Ventricular Tachycardia
Authors: PAGÉ PIERRE L. , CARDINAL RENé , SAVARD PIERRE , SHENASA MOHAMMAD
Published: July 2006

The relationship between electrograms recorded during sinus rhythm and the activation sequence during ventricular tachycardia induced by programmed stimulation was investigated in a canine model of myocardial infarction. Thirteen dogs were studied 3 days (n = 10) or 14 days (n = 3] after coronary occlusion. Sixty‐three unipolar electrograms were simuitaneously recorded with a sock electrode array connected to a digital recording system, and analyzed by computer. Bipolar electrograms were recorded sequentially from the same sites with an analog recorder. Categories of unipolar electrograms were defined with reference to the QRS complex during sinus rhythm as follows: Class A included electrograms with an intrinsic deflection inscribed within the QRS complex, class B included those which did not exhibit any intrinsic rs deflection, and class C included those with an intrinsic deflection inscribed later than QRS. The epicardial distribution of each class of electrograms was significantly different between the preparations with, and those without inducible tachycardia (72% versus 63% of electrograms being in class A, 20% versus 35% in class B, and 8% versus 2% in class C; p < 0.005). When tachycardia was inducible, class C epicardial electrograms were located in an area extending across the region of infarction, which corresponded to the common reentrant pathway of figure‐of‐eight patterns mapped during tachycardia, When ventricular tachycardia was not inducible, class B electrograms were recorded all over this region. The morphology of bipolar electrograms had no predictive value in identifying the common reentrant pathway. These results support the view that the inducibility of reentrant tachycardia is dependent upon critically located delayed activity detected during sinus rhythm by unipolar recordings.
Electrical Safety During Electrophysiological Testing
Authors: RUBIN STANLEY A. , NALOS PETER C. , SOLINGEN SIMON , WHITING JAMES , GANG ELI
Published: July 2006

This report describes the inadvertent induction of non‐sustained atrial and ventricular arrhythmias due to the malfunction of a programmable cardiac stimulator. The malfunction occurred when line power resumed after a brief municipal power outage (“blackout”) during an invasive eiectrophysiological study. The stimulator spontaneously delivered very high frequency pulses through the electrode catheter to the myocardium which resulted in atrial and ventricular arrhythmias. During bench testing, the stimulator delivered a continuous train of high frequency output pulses (≥1 mA) when line voltage resumed normal level after it had dropped below 65 VAC. Electrical safety during electrophysiological testing requires a stimulator design which is immune to altered operating conditions, and which shuts down if abnormal operating or output conditions are detected.
The Effect of Metal Detector Gates on Implanted Permanent Pacemakers
Authors: COPPERMAN YITSCHAK , ZARFATI DIZA , LANIADO SHLOMO
Published: July 2006

The effect of metal detector security gates, such as are used in airports, was tested in 103 nonselected pacemaker patients. Various types of single and dual chamber units were examined, using telemetry during the test. Pulse rate and duration were measured immediately before and after the procedure. No ill effect was seen on any of the units tested, pacemaker inhibition was not observed, and programmability was not affected. Metal detector security gates have no effect on imp/anted permanent pacemakers.
P‐Wave Sensing in VVI Pacemakers: Useful or a Problem?
Authors: VAN GELDER L.M. , GAMAL M.I.H. EL , TIELEN G.H.J.
Published: July 2006

Total inhibition of a bipolar VVI pacemaker was observed in an 84‐year‐oid female after programming the pulse generator to its highest sensitivity (0.6 mV). After a short period of observation it became obvious that P‐wave oversensing was responsible for this phenomenon. Frontal and lateral X‐rays showed a normal position of the ventricular lead. Although oversensing could easily be avoided by decreasing sensitivity, changing the pacing mode to VVT converted the VVI pacemaker to an atrial synchronous ventricular pacing system.
The Effect of Propranolol and Verapamil on External Pacing Threshold: A Placebo‐Controlled Study
Authors: FALK RODNEY H. , KNOWLTON ANNE A. , BATTINELLI NANCY J.
Published: July 2006

External transthoracic pacing is frequently used in situations where cardiac medications are administrated. In view of theoretical concerns of the effects of beta‐blocking and calcium channel blocking agents on pacing threshold, these agents were studied in six normal subjects over a 90 minute period during external cardiac pacing. Subjects received 10 mg propranolol, verapamil or identical placebo intravenously on 3 separate days in a double‐blinded trial with serial determination of pacing threshold. Neither placebo nor either active drug altered pacing threshold. It is concluded that propranolol and verapamil have no significant effect on the threshold required for external transthoracic pacing in normal subjects and concerns about a drug induced increase in threshold may be unfounded.
Apparent Undersensing Due to Oversensing of Low Amplitude Pulses in a Thoracic Impedance‐Sensing, Rate‐Responsive Pacemaker
Authors: WILSON JOHN H. , LATTNER STEPHEN
Published: July 2006

A case in which apparent undersensing was caused by detection of low amplitude impedance‐measuring pulses emitted by a thoracic impedance‐sensing rate‐modulated pacemaker is described. The detection of these high frequency pulses was interpreted as “noise” by the pacemaker and led to asynchronous pacing in the interference reversion mode. Increasing the sensitivity /ailed to correct the problem. Decreasing the sensitivity eliminated oversensing of the low amplitude pulses and the apparent undersensing. Recognition of (his phenomenon is important to prevent a misdiagnosis of undersensing.
Implantation of Double Screw‐in Leads
Authors: STIRBYS P.
Published: July 2006

Since 1978, 600 double screw‐in leads have been implanted, 320 in the ventricle and 280 in the atrium. Four episodes of cardiac perforation, one of which was lethal, have occurred during guide‐catheter insertion. The electrode is now coated with polyglycol which is blood soluble and covers the electrode hooks during introduction into the vascular system without a guide catheter. The electrode hooks are exposed and can be attached to the endocardium. Three atrial leads, 1.07% and one ventricular lead, 0.31%, have become dislodged. Total dislodgement has thus been 0.67%.
Some Recent Concepts Concerning the Mechanisms of Action of Antiarrhythmic Drugs
Authors: ROSEN MICHAEL R. , SPINELLI WALTER
Published: July 2006

The administration of antiarrhythmic drugs is determined largely on the basis of empiricism, and the experience of individual physicians and the results of clinical studies are probably the two major factors determining the approach to treatment. Although much effort has been expended in learning the mechanisms of action of antiarrhythmic drugs, the applicability to clinical treatment of the knowledge attained has been limited. Nonetheless, recent advances in our understanding of the biology of the cardiac cell, of the factors that predispose to arrhythmias and of drug‐receptor interactions, have not only provided new insights into the mechanisms whereby specific drugs exert their effects, but promise to provide means for designing and testing compounds whose actions will be more specific and more predictable than is presently the case. This paper will review some of the advances that have been made and will consider some of their implications.
Morphologic Differences of the Endocardial Electrogram in Beats of Sinus and Ventricular Origin*
Authors: TOMASELLI GORDON F. , NIELSEN ANTON P. , FINKE WILBUR L. , SINGUPTA LINA , CLARK JOHN G. , GRIFFIN JERRY G.
Published: July 2006

The lack of accurate arrhythmia detection and identification is one of the major obstacles to improvement in the efficacy of antitachycardia devices. We evaluated a method for detection of beats of ventricular origin compared to sinus rhythm based on the morphology of the endocardial electrogram. In order to compare mechanically induced ventricular beats to normal sinus beats, endocardial electrograms from a standard pacing electrode were recorded from eight open‐chested dogs. Time and frequency domain features analyzed included peak‐to‐peak amplitude (AMP), maximal slew rate (dV/dT). and frequency content (‐3 dB downpoint). Quantitative morphologic comparison of the waveforms was performed using standard correlation and by the absolute area of difference between the waveform and a sinus beat template. The AMP and dV/dT for a group of ventricular beats did not differ significantly from beats of sinus origin. In the unipolar configurution ‐3 dB for ventricular beats was significantly different from sinus beats (p = .01), but overlap occurred in three of eight cases. Conversely, using either method of assessment of morphological differences, all ventricular beats could be identified without overlapping the values for normal beats. We concluded that morphologic analysis of the endocardial electrogram by such methods may be a highly accurate means of distinguishing between beats of sinus and ventricular origins. This technique may also be applicable to the problem of automatic rhythm identification by implanted devices.
Role of Programmed Electrical Stimulation of the Heart in Risk Stratification Post‐Myocardial Infarction
Authors: GONZÁLEZ ROLANDO , ARRIAGADA DOMINGO , GORBALAN RAMON , GHAMORRO GASTON , FAJURI ALEJANDRO , RODRÍGUEZ JOSÉ A.
Published: July 2006

Programmed electrical stimulation (PES) of the heart was evaluated as a method of identifying patients at risk of sudden death post‐myocardial infarction (post‐MI). Eighty‐four patients (mean age, 56 ± 10 years) underwent PES 6 to 8 weeks post‐MI. PES was performed at the right ventricular apex at twice diastolic threshold. Prior to stimulation patients were studied with exercise stress testing, 24‐hour Holter monitoring and radionuclide ejection fraction. The patients were placed into two groups, according to their responses to electrical stimulation. Group 1: 65 patients in whom no arrhythmias were induced or who had repetitive responses that lasted Jess than six cycles; Group 2:19 patients in whom ventricular tachycardia was induced. At the end of follow‐up (20 ± 9 months) six patients from Group 1 had died. Complex ventricular ectopy and ventricular tachycardia were more frequently detected on Holter in Group 2 (9/19) than in Group 1 (14/65) (p < 0.03). The results of exercise testing and radionuclide ejection fraction did not correlate with the response to PES. However all but one of the patients who died had a left ventricular ejection fraction (LVEEJ under 40% and four out of six patients had ventricular tachycardia on Holter monitor. We draw the conclusion that PES did not contribute to the identification of high‐risk patients post‐MI, as none of the 19 patients in whom ventricular tachycardia was induced died during follow‐up. In addition, high‐risk patients were characterized by poor ventricular function and complex ventricular arrhythmias on Holter recording.
Percutaneous Pacemaker Lead‐Transsecting Catheter
Authors: WITTE JOACHIM , MUNSTER WOLFGANG
Published: July 2006

We describe the development and successful use of a percutaneous lead‐transsection catheter. It was used in two patients in whom removal of chronically implanted atrial pacing leads could not be accomplished by traction.
The Efficacy, Electrophysiologic and Electrocardiographic Effects of Intravenous Pirmenol, a New Class I Antiarrhythmic Agent, in Patients with Ventricular Tachycardia: Comparison with Procainamide*
Authors: GOLD ROBERT L. , FRUMIN HOWARD , HAFFAJEE CHARLES I. , KERIN NICHOLAS Z. , JARANDILLA RECINA
Published: July 2006

The electrophysiologic and electrocardiographic effects of intravenous pirmenol were compared with intravenous procainamide in 17 patients with symptomatic ventricular tachycardia. Pirmenol was found to prolong the PR interval, the QRS duration, the QTc interval, the HV interval, the atrial effective refractory period, and the ventricular effective refractory period. The sinus cycle length decreased following pirmenol administration. The sinus node recovery time, the PA interval, the AH interval, the Wenckebach cycle length, and the AV nodal ERP were unchanged. In patients whose ventricular tachycardias remained inducible on pirmenol, the cycle length was significantly prolonged compared to baseline. These changes were similar to those seen following the administration of procainamide. All 17 patients had sustained ventricular tachycardia inducible during programmed ventricular stimulation in the baseline state. In four patients the ventricular tachycardia was suppressed with both primenol and procainamide. In the remaining 13 patients ventricular tachycardia remained inducible on procainamide. Of these 13 patients, an additional two patients had their ventricular tachycardias rendered noninducible on pirmenol. In conclusion: (1) the electrophysiologic and electrocardiographic effects of pirmenol are similar to those of procainamide; (2) although ventricular tachycardia inducibility following procainamide was similar to that of pirmenol, an occasional patient with ventricular tachycardia inducible on procainamide had ventricular tachycardias suppressed on pirmenol.
A Case of Pacemaker Lead Fracture Associated with Thoracic Outlet Syndrome
Authors: SUZUKI YASUKO , FUJIMORI SHOKO , SAKAI MAKOTO , OHKAWA SHIN‐ICHIRO , UEDA KEIJI
Published: July 2006

A pacemaker lead fracture in the left subclavian vein was caused by compression of the clavicle and the first rib; subsequent coil elongation at the same site on the right side was observed in the replacement lead in a patient with thoracic outlet syndrome. Venography showed narrowing of the subclavian vein at the site where the lead abnormalities were observed. This case illustrates that a lead in the subclavian vein can be easily damaged when a patient has thoracic outlet syndrome.
Sensing Aberration by the Automatic Implantable Cardioverter Defibrillator During Intraoperative Testing
Authors: VLAY STEPHEN C. , MOSER SUZAN ANNE , SEIFERT FRANK
Published: July 2006

A 50‐year‐old man underwent replacement of his automatic implantable cardioverter defibrillator (AICD) because a magnet test revealed severe battery depletion. He had had his unit implanted 18 months previously after an episode of sudden cardiac death. He had documented torsades de pointes and inducible ventricular tachycardia, confirmed by electrophysiologic study. Before a new unit was implanted thresholds were measured by an external cardioverter defibrillator. Ventricular fibrillation (VF) was induced by alternating current through a standard, line‐operated battery charger with stimulation delivered to the epicardium via rate‐sensing electrodes. VF was allowed to continue for 10 seconds before shock was delivered. Termination o/VF required 15 joules, which was higher than that required at initial implantation 18 months earlier. The new pulse generator was activated/or testing and VF was again induced. The AICD discharged after 12.3 seconds. Prior to wound closing, the AICD was deactivated by magnet. Instead of R‐wave synchronous beeping tones during deactivation, double beeping tones were heard. Electrogram recordings revealed abnormalities of the T‐wave and ST segment of the rate‐sensing electrodes, which were the cause of the tone irregularities. Stabilization of the T‐wave and ST segment occurred within 8 minutes and the tones became normal. The procedure was then completed.