bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissociation of the Site of Origin from the Site of Cryo‐termination of Ventricular Tachycardia*
Authors: GESSMAN LAWRENCE J. , ENDO TAKAO , EGAN JOHN , GALLAGHER JOHN D. , HASTIE ROBIN , MAROKO PETER R.
Published: July 2006

We performed conventional electrogram mapping and cryomapping in dogs with one‐week‐old experimentally‐induced myocardial infarctions and programmed stimulation‐induced sustained ventricular tachycardias to assess whether there is a correlation between the “site of origin” and site of cryo‐termination of ventricular tachycardia (VT). Electrogram maps showed that 4 of 8 induced sustained VTs were due lo macro‐ and 4 of 8 tomicrore‐entry. Local cooling of the site of origin terminated 4 of 4 microre‐entrant VTs, but only 1 of 4 macrore‐entranf VTs. Jn the other 3 macrore‐entrant VTs, the sites of cryo‐termination were 2, 2,5, and 4 cm distant from the sites of origin. In contrast, cooling of the mid‐to‐late diastolic portions of the re‐entry loops terminated all 8 VTs. These data demonstrate a dissociation of the site of origin from the site of cryo‐termination of macrore‐entrant VT.
Amiodarone: Individualizing Dosage with Serum Concentrations
Authors: ROTMENSCH HESCHI H. , SWANSON BRIAN N. , GREENSPON ARNOLD J. , SHOSHANI DAVID , GREENSPAN ALLAN M.
Published: July 2006

The purpose of the present report is to review the available pharmacokinetic informaation on amiodarone with an emphasis on our own experience in monitoring serum amiodarone concentrations. We have found that 400 mg should be the maximal maintenance dose; if that treatment fails, careful addition of other antiarrhythmic agents is preferable over an increase in amiodarone dosage. Serum concentrations below 2.5 mg/L will significantly improve amiodarone's benefit‐to‐risk ratio.
Electrocardiographic Abnormalities Suggesting Myocardial Infarction in a Patient with Severe Cranial Trauma
Authors: BRUNNINKHUIS LEO G.H.
Published: July 2006

Serial electrocardiograms were done in a patient admitted to the hospital after a severe head injury. The electrocardiograms showed the development of Q‐waves and marked ST‐segment changes, suggestive of a myocardial infarction. At autopsy no abnormalities were found in the coronary arteries or myocardium.
Characteristles of Advanced Porous and Textured Surface Pacemaker Electrodes
Authors: HIRSHORN MICHAEL S. , HOLLEY LORAINE K. , SKALSKY MICHAEL , HOWLETT C. ROLFE , MUSGROVE ELIZABETH
Published: July 2006

Reduced stimulation thresholds, improved sensing and betler attachment have been claimed for totally porous and porous surfaced electrodes. In this study, the potential for clinical use of two new types of porous electrodes and a non‐porous, textured high microsurface area electrode, has been evaluated by comparison with equivalenf sized, smooth non‐porous controls. Eighteen sintered and seven laser drilled porous electrodes, seven non‐porous textured electrodes, and sixteen controls, were implanted singly in fhe right ventricles of sheep. Measurements of threshold, pacing, sensing and bulk impedances were taken at regular intervals for up to 180 days. At sacrifice, only three of the thirteen non‐porous confrols were attached. AU laser porous electrodes, apart from two which were dislodged, were attached, as were eieven of fifteen sintered porous, and five of seven textured non‐porous electrodes. Tissue ingrowth was found for both porous electrode types. Stimulation threshoJds were not statistically different for all electrode types (p < 0.05). Pacing and bulk impedances of the two porous and surface textured electrodes were significantly higher (p < 0.10, p < 0.05, respectively) than those of controls. The three new electrodes exhibited similar chronic sensing impedance vaJues, 30% less than equivalent non‐porous electrodes. The similar sensing performance of the porous and high microsurface area non‐porous electrodes indicates that the nature of the external surface, rather than internal porosity, determines sensing impedance. All three new electrode types showed improved attachment and sensing compared with similar smooth eJectrodes. The laser porous electrode, which permits fixation by tissue ingrowth and maintainssimplicity of construction, is promising for routine clinical use.
Bystander Accessory Pathway During AV Node Re‐entrant Tachycardia
Authors: SMITH WARREN M. , BROUGHTON ARCHER , REITER MICHAEL J. , BENSON D. WOODROW , GRANT AUGUSTUS O. , GALLAGHER JOHN J.
Published: July 2006

Between 1970 and July 1980, wide QRS tachycardia due to re‐entryconfined to the AV node with bystander involvement of an accessory atrioventricular pathway (AAV) was documented in three of 290 patients with the Wolff‐Parkinson‐White syndrome studied at Duke Medical Center. In each of the patients, at least one transition between wide and narrow QRS morphology was recorded without change in either the cycle length of tachycardia or the atrial activation sequence. Two of the three patients had a single left‐sided AAV (lateral, posterolateral) showing antegrade conduction only. The third patient had two right‐sided AAVs (free wall, septal), each capable of bidirectional conduction. Initiation and termination of repetitive concealed conduction into the ventricular insert of an AAV appeared to be one mechanism determining bystander AAV participation. Documentation of the retrograde sequence of atrial activation during tachycardia, and examination of the effects of interpolated premature depolarizations from both the ventricle and midline atrium are the most helpful features in resolving the differential diagnosis of wide QRS tachycardia in patients with W‐P‐W syndrome.
Dynamic Electrocardiography and Ventricular Pauses of 3 Seconds and More: Etiology and Therapeutic Implications
Authors: ECTOR H. , ROLIES L. , DE GEEST H.
Published: July 2006

A total of 2350 consecutive Holter recordings revealed that 53 patients had ventricular asystole of 3 seconds or more. The diagnoses based on the longest pauses were: sinus arrest in 19; AV block in 5; slow atrial fibrillation in 29. Symptoms occurred in 45 and were absent in 8 patients. Associated heart disease was present in only 33 cases. A pacemaker was implanted in 7 out of 8 asymptomatic patients. Ventricular asystole of 3 seconds or more is proposed as a definite indication for the implantation of a permanent pacemaker.
Horizontal and Longitudinal Dissociation of the A‐V Node During Atrial Tachycardia
Authors: ROY DENIS , WAXMAN HARVEY L. , BUXTON ALFRED E. , JOSEPHSON MARK E.
Published: July 2006

The co‐existence of horizontal and longitudinal dissociation of the atrioventricular (A‐V) node has not previously been reported. Analysis of ECG tracings from 4 patients with supra ventricular tachycardias showing an irregular ventricular rate suggest that such a mechanism was responsible for the irregular A‐V conduction pattern. His bundle recording was obtained in one patient and revealed the site of block to be located in the A‐V node. Multi‐level block and longitudinal dissociation of the A‐V node is probably not rare and should be included in the discussion of supraventricular arrhythmias displaying irregular ventricular rates.
Dual Accessory Nodoventricular Pathways: Role in Paroxysmal Wide QRS Reciprocating Tachycardia
Authors: BENDITT DAVID G. , EPSTEIN MICHAEL L. , BENSON D. WOODROW
Published: July 2006

Clinical electrophysiological study in an otherwise healthy 21 ‐year‐old male with paroxysmal wide QRS tachycardia (cycle length 300 ms. heart rate 200/min) suggested the presence of two nodoventricular (NV) bypass connections. The first NV connection pre‐excited the base of the interventricularseptum (NVs), as evidenced by a short HV interval during sinus rhythm (15–20 ms), with local ventricular activation occurring earlier at the septal base than at either the right ventricular apex or the base of the left vcntricle. The second NV connection appeared to connect the AV junction with the right ventricle (NVRV). Intracardiac recordings from a portion of the right‐bundle branch of the interventricular conduction system demonstrated right ventricular pre‐excitation by NVRV during both atrial pacing and reciprocating tachycardia. The latter finding supported participation of NVRV in the tachycardia. Further, following exclusion of atrial participation in the arrhythmia, premature depolarization of the right ventricle and interventricularseptum appeared to advance the tachycardia without altering the timing of His bundle depolarization, implicating NVS in the retrograde limb of a re‐entry circuit. Consequently, this study demonstrated the presence of two NV connections and provided further support to the concept that NV accessory bypass connections may comprise portions of a re‐entry pathway during reciprocating tachycardia in man.
Atrial Synchronized Ventricular Pacing: Contribution of the Chronotropic Response to Improved Exercise Performance
Authors: FANANAPAZIR LAMEH , BENNETT DAVID H. , MONKS PHILIP
Published: July 2006

In contrast to asynchronous ventricular pacing (VOO, VVI), alrial synchronized ventricular pacing (VAT, VDD, DDD) maintains the normal sequence of cardiac chamber activation and permits a chronotropic response to exercise. thereby improving exercise performance. To assess the separate contributions of these two factors to improved work capacity. 14 patients with implanted programmable VAT pacemakers were exercised according to the Bruce protocol, in three different pacing modes, selected in a random orderand on a double blind basis: (a) VAT: (b) chest wall stimulation triggered ventricular (V‐CWS‐T) pacing, during which the pacemaker was programmed to VAT mode but driven externally using chest wall stimulation at rates fractionally above the patients'atrial rate, thereby providing a chronotropic response to exercise without atrioventricular synchronization; and (c) VOO mode at 70 beats per minute. There was a significant improvement in exercise performance in all patients during both VAT and V‐CWS‐T pacing as compared to VOO mode; the average increase in work capacity being similar: VAT: 44 ± 31, (range, 12 to 140) percent and V‐CWS‐T; 40 ± 24 (range, 5 to 85) percent. It is concluded that in patients with adaptive pacing systems, the chronotropic response is the major determinant of any improvement in exercise performance.
Assessment of Atrial Capture in Committed Atrioventricular Sequential (DVI) Pacing Systems
Authors: LEVINE PAUL A. , BRODSKY SAMUEL J. , SELTZER JEFFREY P.
Published: July 2006

Two patients with committed dual unipolar AV sequential pacing systems are presented in whom alrial capture was unable to be demonstrated on the surface electrocardiogram. The bedside examination is proposed as a means of identifying the presence or absence of atrial capture with subsequent confirmation by M‐mode echocardiographs and jugular venous pulse tracings. Mode, rate, and output programmabilitymayaidin the evaluation of thesepacing systems. Intentional reduction of the ventricular output to subthreshold levels in pacemakers capable of this degree of programmabilily will permit the rapid bedside confirmation of atrial capture without the need for expensive and time‐consuming noninvasive tests.
Incessant Dual Supra ventricular Tachycardia in a Child
Authors: GREEN MARTIN , BRUGADA PEDRO , WELLENS HEIN J.J.
Published: July 2006

A 5‐year‐old boy was studied because of incessant supra ventricular tachycardia. He was shown to have two forms of supravenlricular tachycardia each of which could be incessant. The interplay between the two tachycardias caused interesting periodic sequences in the surface electrocardiogram. Ourstudy illustrates the value of careful analysis of the surface P wave morphology and the usefulness of programmed electrical stimulation of the heart in determining the mechanism of tachycardia.
Pacemaker Runaway Following Intermittent Output Failure
Authors: RUBENSTEIN JOEL J. , LAFORET EUGENE G.
Published: July 2006

A case with a mixed pattern of pacemaker failure is presented, “Runaway” pacemaker with ventricular capture at 250 beats per minute occurred three days after the development of syncope associated with intermittent loss of pacing artifact. Presumed protection by placement of a temporary pacemaker upon admission was unfounded. This case argues for rapid diagnosis of pacemaker failure, followed by prompt surgical exploration and repair of the pacing system.
Extraction of Chronically Infected Transvenous Pacemaker Leads: Report of an Unusual Problem
Authors: COLOSIMO LEE R. , LAWRIE GERALD M. , ROEHM JOHN O.F. , DEBAKEY MICHAEL E.
Published: July 2006

This is a report of a patient with an impacted, chronically infected transvenous pacemaker lead whose management was complicated by the presence of a functioning contralateral transvenous pacemaker. Treatment included sustained traction on the infected lead, a left subcostal thoracofomy for placement of new sutureless epicardial leads, and retrograde right iliac vein cannula‐tion for final snare removal of the mobilized lead. The patient is currently free of infection, and has normal pacemaker function.
Trans‐Esophageal Pacing
Authors: ANDERSEN H.R. , PLESS P.
Published: July 2006

new lead‐electrode for trans‐esophageal pacing of the human heart has been developed. The heart can be paced from the esophagus using currents of the same intensity as those for temporary pacing electrodes. The lead allows the electrodes to be positioned properly in the esophagus with a gastric balloon without use of additional equipment. Non‐invasive atrial for veniricular pacing can thus be established quickly, even by non‐specialized physicians. The method has been tested on a group of 13 healthy volunteers. Both atrial and ventricular pacing were performed without discomfort. The method opens new diagnostic and therapeutic possibilities with trans‐esophageal pacing techniques.
Reversible EOL‐Indicator: A New Cause for Low Pacemaker Rate
Authors: SCHEIBELHOFER W. , KALIMAN J. , LACZKOVICS A. , MAYR H. , WEBER H. , KAINDL F.
Published: July 2006

se is presented in which a newcause for decrease in pacemaker rate was encountered: six months after implantation of a Medtronic 5967 pacemaker, the first routine check‐up revealed a rate of 62.5 ppm instead of 70 ppm. After application of a magnet, al1 measurements returned to normal. The cause for this phenomenon, which could not be attributed to battery depletion or over sensing, was probably a change of state of the flip‐flop which is responsible for the sudden rate drop of 10% which serves as the end‐of‐life (EOL)‐indicator in this pacemaker. This change of state may result from a very short decrease of power supply voltage during shipment or at the time of implant, and is fully and permanently reversible by performance of the magnet test. In order to prevent unnecessary pacemaker explains, future pacemaker circuits should be redesigned to eliminate the effect of very short voltage changes. Meanwhile, a routine magnet test should be performed immediately after implantation.
Electrophysiologic Findings in Carotid Sinus Massage
Authors: PROBST PETER , MÜHLBERGER VOLKER , LEDERBAUER MONIKA , PACHINGER OTMAR , KALIMAN JOSEF , STEINBACH KONRAD
Published: July 2006

Thirty patients with carotid sinus syndrome were electrophysiologically studied. In 14 patients carotid sinus massage was performed during atrial and ventricular stimulation, and the conduction times were measured. The AH‐time was prolonged by more than 120ms in 6 patients(20%); the HV‐time was prolonged in 6 patients by more than 55 ms (20%); 5 patients had bundle branch block (16.7%); The sinus node recovery time was prolonged in 7 out of 27 patients (26%). Ten patients (33%) did not have additional electrophysiologic abnormalities. There was a predominance of carotid sinus syndrome on the right side. During carotid sinus massage there was a significant increase of the AH‐time, but there were no significant changes of the HV‐time or the width of the QRS‐complexes. Twenty‐one patients developed an atrial asystole and 9 patients an atrial bradycardia and an additional AV‐block. There was a longer AH‐time and a longer prolongation of the AH‐time in the patients who developed an AV‐block. Twelve out of 14 patients (85.7%) developed an AV‐block during carotid sinus massage and atrial pacing. During ventricular pacing 5 of 14 patients (35.7%) revealed a complete retrograde block before carotid sinus massage and 5 of the remaining 9 patients developed a total retrograde block during carotid sinus massage. Consequently, in 71.4% of the patients with carotid sinus syndrome complete retrograde conduction block and atrial asystole can be expected during attacks of ventricular asystole and simultaneous ventricular pacing. In conclusion, there is a high incidence of additional disturbances of the sinus node function and AV‐conduction in patients with carotid sinus syndrome. AAI pacemakers are contraindicateddue to the common development of additional A V‐block during carotid sinus massage. Physiologic pacing might contribute to better hemodynamics, particularly in patients with the mixed type of carotid sinus syndrome.
An Unusual Mechanism of Initiation of Circus Movement Tachycardia in a Patient with Concealed Wolff‐Parkinson‐White Syndrome
Authors: STEVENSON WILLIAM G. , WEISS JAMES
Published: July 2006

Infranodal conduction delay is an uncommon mechanism of initiation of circus movement tachycardia in the Wolff‐Parkinson‐White syndrome. A patient with a concealed left free wall atrioventricular accessory pathway who underwent electrophysiological study is presented. During alrial extrastimulus testing, a pattern ofalter‐nating bundle branch block was observed and was most marked after the administration of intravenous procainamide. Conversion from right bundle branch block to left bundle branch block was reproducibly associated with the initiation of circus movement tachycardia utilizing the normal conducting system anfegradely and the accessory pathway retrogradely. Initiation of tachycardia was critically related to the increase in the HV interval associated with left bundle branch block. Of interest, conduction in the right bundle branch became progressively slower as the prematurity of the atrial extrastimulus increased, whereas conduction time through the left bundle branch remained fixed prior to block. Implications of these findings are discussed. To our knowledge, this is thefirst report of alternating bundle branch block during atrial extrastimulus testing as a mode of initiation of circus movement tachycardia in the Wolff‐Parkinson‐White syndrome.
A New Atrial Lead with Improved Stability and P‐Wave Detection
Authors: HUGHES HOWARD C. , BERTOLET ROY D. , BROWNLEE ROBERT R.
Published: July 2006

A new segmented polyether polyurethane atrial pacemaker lead has been developed and tested acutely and chronically in dogs. This lead was constructed so that its tip could q uick‐ly and accurately be positioned in close proximity to the S‐A node and provide long‐term stability without the use of active fixation devices such as tines or screws. The acute intrinsic P‐wave potentials seen at the S‐A node area (9.7 ± 4.7 mV) were superior to those defected in the appendage (4.7 ± 2.8 mV) and coronary sinus (6.8 ± 4.1 mV). There were no significant differences in pacing thresholds between sites. In long‐term studies, transvenous (juguiar) leads maintained their position for over three months without dislodgment in active unrestrained dogs with only a 25% decrease in intrinsic P‐wave potentials. The chronic pacing thresholds for this lead were similar, or superior, to those reported for other pacemaker lead placement sites. The polyurethane coating material produces no adverse tissue reaction or thrombosis.
Ventricular Refractory Periods in Relation to Rate and Test‐Site VT Intervals in Anesthetized and Conscious Dogs: A Canine Model for Conscious State Measurements
Authors: SARMA JONNALAGEDDA S.M. , BILITCH MICHAEL , MELINTE SERGIU G.
Published: July 2006

The functional relationship of ventricular effective refractory period (ERP) with basic cycle length (BCL) of stimulated ventricular depolarization and VT intervals of test‐site unipolar ventricular eJectrograms were studied in five conscious and eight anesthetized (sodium pentobarbital, 30 mg/kg) open‐chested dogs. The range of BCLs studied was 300 to 1000 ms, achieved through ventricular stimulation following chemically‐induced complete A V block. In the conscious animal model developed for this study, two‐to‐four ventricular electrode Jeads were exteriorized and the ventricular rate was maintained by an implanted programmeble VVI pacemaker. In all animals studied, the BCL‐ERP relation was closely represented by the empirical equation ERP = A‐B.Exp(‐k.BCL), and the VT‐ERP relation over the same range of BCLs was linear: ERP = C+D. VT. The correlation coefficients were in the range of 0.991 to 0.999. The mean values of the parameters in the above equations determined by the appropriate non‐linear or linear regression analysis showed significant differences between the two groups of animals studied. In three conscious animals a strong linear correlation between the test‐site VT intervals and simultaneously measured QT intervals measured from the lead II surface electrogram was demonstrated (r = 0.993 to 0.998). For a fixed site of stimulation, the morphology of ventricular depolarization complexes as well as the corresponding T‐waves remained essentially unaltered with BCL for both myocardial and surface eJectrograms. The possible applications of developed canine model and the results of the present study include: (1) the study of the rate‐dependent effects of cardioactive drugs on ventricular electrophysiology and, (2) the improved design of electronic refractory periods of rate programmable pacemakers.
Orthogonal Ventricular Electrogram Sensing
Authors: GOLDREYER BRUCE N. , BRUESKE ROSCOE , KNUDSON MARK B. , CANNOM DAVID S. , WYMAN MILFORD G.
Published: July 2006

Inappropriate demand pacing is most commonly due to improper ventricular electrogram sensing. Filters and programmable sensitivities improve eleclrogram sensing of conducted beats, but paced electrograms cannot be sensed by conventional unipolar or bipolar systems. A permanent pacing lead with a standard tip electrode and three orthogonal 0.8 mm2 sensing electrodes located circumferentially 2 cm proximal to the pacing tip was tested in 22 patients. The tip electrode was placed in the right ventricular apex in standard pacing position. Orthogonal electrodes were not in contact with ventricular myocardium. Orthogonal ventricular eleclrograms from 54 electrode pairs were compared with unipolar tip electrograms during conducted rhythms and paced beats. Tip ventricular electrograms averaged 12.8 mV with 3.04 mVT waves. Orthogonally recorded ventricular electrograms during conducted beals averaged 8.86 mV with T waves of 1.57 mV. During pacing, tip ventricular electrograms were obscured by the stimulus artifact and repolarization events. Orthogonal ventricular electrograms, however, demonstrated small discrete stimuli of 1.99 mV followed by discrete ventricuJar electrograms of 9.19 mV and T waves of 1.9 mV. Orthogonal ventricular electrograms compared favorably with contacting tip electrograms during conducted beats and provided a redundant sensing capability. During pacing, orthogonal ventricular electrograms allowed the capability for capture verification. A new pacing catheter allows for improved ventricuJar electrogram sensing and capture verification.
The Electrophysiologic Basis for the Use of Amiodarone for Treatment of Cardiac Arrhythmias
Authors: HAMER ANGAS W.F. , MANDEL WILLIAM J. , ZAHER CAROL A. , KARAGUEUZIN HYRAR S. , PETER THOMAS
Published: July 2006

The electrophysioiogic basis for the use of amiodarone in the treatment of cardiac arrhythmias is outlined, with reference to studies in isolated cardiac tissues, whole animal, and human studies. Amiodarone appears fo have the distinctive property of directly prolonging action potential duration (and hence refractory periods) in nearly all cardiac tissues. Independenf of ifs effects on refrac‐toryperiods, conduction may also be impaired in the His‐Purkinje system, possibly due to depression of phase of the action potential. Sinus node and atrial automaticity, as well as that arising from diseased Purkinje fibers, may be depressed, Normal ventricular escape pacemakers appearrelatively unaffected, however. A nonspecific anti‐andrenergic action may contribute to its observed effects. These electrophysiological effects are more obvious and predictable after several weeks of oral treatment than after intravenous administration, suggesting a time‐dependent mechanism of action. The drug appears well suited to the prevention of enhanced automaficity in the ventricle and reentry throughout the heart. and its frequent clinical success in a broad spectrum of cardiac arrhythmias attests lo this. Unwanted side effects include sinus node depression, His‐Purkinje conduction delay or block, and ventricular arrhythmias enhanced by QT prolongation. However, the frequency of clinically significant examples of unwanted arrhythmic effects appears to be acceptably low.
Doppler Echocardiographic Studies in Sequential Atrioventricular Pacing
Authors: NANDA NAVIN C. , BHANDARI ANIL , HAROLD SERGE S. , FALKOFF MICHAEL
Published: July 2006

Six patients with sequential atrioventricular pacemakers were studied by Doppler echocardiography. A commercially available continuous wave system (transcutaneous aortovelography) was used and the transducer was placed in the suprasternal notch and angled to obtain peak aortic arch blood flow velocity. Changes in Doppler peak velocity have been previously shown to correlate closely and reliably with changes in hemodynamically measured stroke volume/cardiac output in the same patients following interventions, In all patients, the pacemaker was programmed from DVI mode to VVI (heart rate was kept constant) and then back to DVI, with the Doppler transducer held in a fixed position all the time, and peak velocities measured after the patient had been in any particular mode for at least 1 minute. Five of 6 patients showed reduction in peak velocities ranging from 13–25% (mean 18.4%) when the pacing mode was switched from DVI to VVI. Doppler peak velocity remained unchanged in 1 patient. Doppler echocardiography represents a simple, noninvasive method for estimating increments in stroke volume/cardiac output obtained with sequential AV pacing.
Total Venous Obstruction Following Atrioventricular Sequential Pacemaker Implantation
Authors: FLAKER GREG C. , MUELLER KARL J. , SALAZAR JOHN F. , MADIGAN NIALL P. , CURTIS JACK J.
Published: July 2006

We describe a case of a 79‐year‐old woman who developed pain and pitting edema of the upper right extremity due to total venous obstruction following the implantation of an atrioventricular sequential pacemaker. She was treated by arm elevation and anticoagulation after which the pain and edema subsided. To our knowledge, this is the first reported case of this complication occurring following implantation of a dual‐chamber pacing system. We recommend that venographic studies be done after implantation if apparent arm swelling occurs, and that anticoagulant therapy be instituted if thrombosis is present.
Detachment of Pacemaker Active Fixation Helix
Authors: DAWKINS KEITH D. , JONES SUZANNE , WARD DAVID E.
Published: July 2006

The introduction of active fixation electrodes has been a major advance in permanent atrial and ventricular endocardial pacing. We report here an important complication in the use of one such device, the Medtronic transvenous unipolar screw‐in ventricular lead (Model 6959).
Two Mechanisms of Arrhythmia Induction by a DDD Pacemaker: A Case Report
Authors: KERR CHARLES R. , COOPER JOCELYN A. , WALLACE TOM , TYERS G. FRANK O.
Published: July 2006

A 68‐year‐old man with sick sinus syndrome and a history of intermittent atrial fibrillation was treated by implantation of a DDD pacemaker. He subsequently developed recurrent episodes of shortness of breath and tachycardia. Investigation revealed two different arrhythmias, both induced by the pacemaker: (1) a tachycardia in which the dual‐chamber pacemaker system provided the antegrade limb and the AV node provided the retrograde limb and (2) a triggered, ventricularly paced tachycardia caused by the pacemaker sensing atrial fibrillation waves. Both rhythms were abolished by reprogrammingto the DVI mode.
Latent Sinoatrial Conduction Disturbances in Symptomatic Patients with Wolff‐Parkinson‐White Syndrome
Authors: RAKOVEC PETER , RODE PRIMOẐ , JAKOPIN JAPEC , HORVAT MATIJA
Published: July 2006

Sinoatrial conduction abnormalities were studied in fourteen patients with Wolff‐Parkinson‐White (WPW) syndrome and frequent attacks of supraventricular paroxysmal tachycardia. Sinoatrial conduction time (SACT), obtained by the method of constant atrial pacing, was prolonged in all but two patients. The mean value was 277 ± 56 ms (mean ± SD). SACT was measured in the same way in sixteen patients without signs of pre‐excitation or Sinoatrial disease; SACT was significantly shorter (p < 0.001) than in the WPW group of patients. The prolongation of SACT in patients with WPW syndrome was confirmed by measuring SACT by the alternative method of programmed atrial stimulation. SACT was found to be prolonged in eight patients (mean ± SD = 239 ± 47 ms). Whether our results should be attributed to WPW syndrome or frequent supraventricular tachycardias—both being a characteristic feature of our patients—remains uncertain. The results of this study, however, indicate that in symptomatic patients with WPW syndrome and frequent episodes of supraventricular tachycardia, Sinoatrial conduction is frequently impaired. Slackening of the sinoatrial conduction is a possible predisposing factor for initiation of tachycardias in the WPW syndrome.
Atrioventricular and Ventriculo‐Atrial Conduction in Patients with Symptomatic Sinus Node Dysfunction
Authors: VAN MECHELEN ROB , HAGEMEIJER FRANS , DE BOER HANS , SCHELLING ADRI
Published: July 2006

In 14 patients with symptomatic sinus node dysfunction—sinus bradycardia, sino‐atrial exit block, or sinus arrest—electrophysiological studies were performed before implantation of a pacemaker. In 8 patients incremented high right atrial pacing showed AV‐nodal Wenckebach at pacing rates equal to or above 130/min (group I); in 6 patients AV‐nodal Wenckebach was reached at pacing rates Jess than 130/min (group II). During ventricular pacing at a rate 10–15% faster than the existing sinus rate, ventriculo‐atrial (VA) conduction was present in all patients of group I, while VA conduction was present in only 2 patients of group II (p < 0.05). Patients with symptomatic sinus node dysfunction but with intact AV conduction frequency show VA conduction during ventricular pacing and thus are particularly at risk for developing a pacemaker syndrome when a ventricular demand (VVI) pacemaker is implanted. This complication can be avoided by atrial demand (AAI) pacing or A V sequential (DVI) pacing. When adequate experience has been gathered with A V universel (DDD) pacemakers, the indications for selection of a pacemaker in patients with symptomatic sinus node dysfunction will probably change.
Erosion of an Epicardial Pacemaker Secondary to Postpericardiotomy Syndrome
Authors: WANG R.Y.C. , MOK C.K.
Published: July 2006

This report describes an unusual case of postpericardiotomy syndrome and pulse generator erosion following subxiphoid insertion of an epicardial pacemaker.
Atrial Tachycardia Facilitating Initiation of Ventricular Tachycardia
Authors: ROY D. , BRUGADA P. , WELLENS H.J.J.
Published: July 2006

A 17‐year‐old male was studied because of clinically documented tachycardias showing narrow and wide QRS complexes. He was found to suffer from an atrial and a ventricular tachycardia. It was demonstrated that initiation of ventricular tachycardia occurred on reaching a critical ventricular rate during atrial tachycardia. Our study illustrates the value of electrophysiological studies in patients suspected of suffering from double or multiple tachycardias. It also shows that the occurrence of one type of tachycardia may be critically related to another type of tachycardia.
Mechanism and Clinical Significance of Atrial Repetitive Responses in Man
Authors: COSÍO FRANCISCO G. , LLOVET ALFREDO , VIDAL JOSÉ M.
Published: July 2006

We have studied the electrophysiological correlates of atrial repetitive responses, induced by single extrastimuli, in a group of 25 patients undergoing electrophysiologic studies for a variety of supraventricular and ventricular arrhythmias. The incidence of repetitive responses was not related to a previous history of atrial tachyarrhythmias. Repetitive responses were observed only when the extrastimulus elicited a significant intra‐atrial conduction delay, as measured from the extrastimulus artifact, to two or three points in the atria. This condition was fulfilled only when the basic atrial rhythm was paced, and it was also facilitated by increasing atrial rate, which shortened the atrial effective refractory period. Atrial pacing thus seemed to facilitate the production of atrial repetitive responses by both promoting intra‐atrial conduction delays during extrastimulation, and by shortening the atrial refractory period. Alrial repetitive responses are probably a nonspecific phenomenon, unrelated to a tendency towards atrial tachyarrhythmias; their mechanism is probably local re‐entry, related to slow conduction of impulses during incomplete repoiarization, and under favorable conditions they may precipitate atrial flutter or fibrillation in predisposed patients.
The Induction of Atrial Flutter and Fibrillation and the Termination of Atrial Flutter by Esophageal Pacing
Authors: KERR CHARLES R. , GALLAGHER JOHN J. , SMITH WARREN M. , STERBA RICHARD , GERMAN LAWRENCE D. , COOK LAURA , KASELL JACK H.
Published: July 2006

In patients with Wolff‐Parkinson‐White syndrome (WPW), it is important to assess the ventricular response during atrial flutter or fibrillation since conduction across the accessory pathway during these atrial rhythms may cause hemodynamic impairment or life‐threatening ventricular arrhythmias. We have recently reported the effective use of an esophageal electrode in pacing the atrium. In this study we praspectively assessed the ability to induce atrial flutter and fibrillation by esophageal pacing in 23 patients with WPW or other electrophysiological abnormalities. An esophageal bipolar electrode with 29 mm interelectrode distance was positioned in the esophagus to record the most rapid and largest esophageal electrogram (mean distance of 36.6 ± 2.9 cm (SD) from the nares). Pacing was performed at cycle lengths of 40–340 ms (mean 166 ± 72), pulse durations of 7.0–9.9 ms, and currents of 10–25 mA. Atrial flutter alone was induced in 6 patients, fibrillation alone in 11 patients, and both arrhythmias in 5 patients, In one patient neither flutter nor fibrillation was induced by esophugeal pacing, and fibrillation was induced only with difficulty using intracavitary pacing. Of the 11 patients with flutter, the arrhythmia was terminated in 8 by esophageal pacing at cycle lengths of 160–220 ms fmean 176 ± 18 ms). All patients tolerated the procedure well with only mild to moderate discomfort. Therefore, esophageal pacing appears to offer an effective, well tolerated method of initiating atrial fibrillation and flutter and terminating atrial flutter and offers a potentially useful noninvasive method of following patients serially.
Notation System and Overlay Diagrams for the Analysis of Paced Electrocardiograms
Authors: BERNSTEIN ALAN D. , PARSONNET VICTOR
Published: July 2006

With the advent of adaptive dual‐chamber pacing, the interaction between the pacemaker and the heart is becoming increasingly complex and the interpretation of paced electrocardiograms more difficult. We have developed a set of notation conventions for use in teaching and rhythm‐atrip analysis. Easily‐drawn symbols delineate successful, unsuccessful, and inhibited pacing and sensing events as well as refractory and blanking periods. Another application is to generate movable transparent overlays after programming a pacemaker, to be used in interpreting subsequent rhythm strips.
Electrocardiographic Recognition of Variant Angina During Permanent Pacing
Authors: MANYARI DANTE E. , KLEIN GEORGE J. , KOSTUK WILLIAM J.
Published: July 2006

We present a patient with a permanent venlricular pacemaker who was investigated for episodes of chest pain associated with syncope. Ambulatory electrocardiographic monitoring showed essentially paced rhythm. ST segment elevation of the paced beats was observed during spontaneous chest pain, but the significance of this finding was initially unclear in the context of the abnormal repolarization associated intrinsically with paced rhythm. At angiography, coronary spasm was demonstrated after ergonovine, and this was associated with ST segment elevation during paced rhythm and with chest pain. We conclude that ST segment elevation may indicate myocardial ischemia even when observed in the face of abnormal repolarization associated with paced rhythm.
Delayed Termination of Re‐Entrant Atrioventricular Nodal Tachycardia
Authors: ROSS DAVID L. , BRUGADA PEDRO , VANAGT EDDY J.D.M. , BAR FRITS W.H.M. , WELLENS HEIN J.J.
Published: July 2006

Termination of atriovontricular nodal (A VN) re‐entrant tachycardia by one or two induced premature beats generally occurs within one tachycardia cycle from the last premature beat. Two cases are described in which programmed stimulation during sustained re‐entrant AVN tachycardia caused delayed termination in the second or third tachycardia cycle following the extrastimuli. The site of block was the antegrade pathway in one case and the retrograde pathway in the other. The most likely mechanism was induced second degree block in one limb of the tachycardia circuit. Delayed termination provided evidence for concealed penetration of the tachycardia circuit in one case. We conclude that delayed termination of tachycardia is not an indicator of the underlying mechanism of tachycardia. Delayed termination may reveal concealed penetration of the tachycardia circuit. Lastly, in unusual cases programmed stimulation may fail to cause immediate termination of re‐entrant tachycardia but may perturb the tachycardia circuit enough to cause termination in subsequent tachycardia cycles.
Experimental and Clinical Study of a New Permanent Myocardial Atrial Sutureless Pacing Lead
Authors: BOGNOLO D. , STOKES K. , WIEBUSH W. , VIJAYANAGAR R. , ECKSTEIN P. , JEFFREY D.
Published: July 2006

A new permanent lead has been developed for atrial epicardial use. Early clinical evaluation (26 human implants) following thorough canine studies indicates that the new lead is safe, effective, and reliable. Canine thresholds and P‐wave amplitudes as a function of implant time are similar to those of transvenous alrial “J” leads. Human thresholds at implant are higher than canine, but change less with time. Implant and acute repositioning were found to be easy. There have been no lead‐related operations.
Resetting of Tachycardia Cycle by Single and Double Ventricular Extrastimuli in Recurrent Sustained Ventricular Tachycardia
Authors: INOUE HIROSHI , INOUE KIYOSHI , MATSUO HIROSHI , KUWAKI KEIICHI , SHIRAI TETSURO , MURAO SATORU
Published: July 2006

In two cases with recurrent sustained ventricular tachycardia (VT) due to re‐entry, the response pattern to extrastimuli during the tachycardia was studied. In each case, right ventricular extrastimuli with longer coupling intervals during VT were followed by fully compensatory pauses and with shorter coupling intervals reset the tachycardia cycle. In one case, a plateau was produced by a single extrostimulus, resembling that seen in the response curve of sinus node automaticity as well as ectopic atrial tachycardia. Two successive stimuli produced three definite zones, i.e., fully compensatory, reset producing a plateau, and progressive prolongation zones with shortening of the coupling intervals between the two stimuli, and terminated the tachycardia with further shortening of the coupling intervals. In conclusion, resetting phenomenon was confirmed on two cases with re‐entrant VT. This phenomenon cannot be used as a criterion to determine the mechanism responsible for VT.
AV Universal (DDD) Pacemaker‐mediated Reentrant Endless Loop Tachycardia Initiated by a Reciprocal Beat of Atrial Origin
Authors: JOHNSON CHARLES D.
Published: July 2006

An AV universal (DDD) pacemaker‐mediated, reentrant, endless loop tachycardia initiated by a reciprocal beat is described. Pacemaker‐mediated tachycardias are discussed and addressed in the light of their growing frequency and importance in patients with physiological pacemakers.
Transtelephonic Monitoring of a Tachycardia‐terminating Pacemaker
Authors: LYONS CHALMERS , SCHROEDER PAUL , SHANKAR K. , BRODINE W.
Published: July 2006

A 66‐year‐old female with recurrent supraventricular tachycardia which worsened progressively was treated with an implanted tachycardia‐terminating pacemaker after treatment with antiarrhythmic drug therapy had failed. The pacemaker had the capacity to detect and respond to tachyarrhythmias. Reliable sensing and termination of the patients tachycardia was accomplished in over 100 inductions of the tachyarrhythmia. Use of this tachycardia‐terminating pacer has given us several new insights that may be important in the care and follow‐up of all pacemaker patients.
Myopotential Interference with a DDD Pacemaker—Report of a Case
Authors: QUINTAL ROBERTO , DHURANDHAR RAJA W. , JAIN RAJENDRA K.
Published: July 2006

This case report describes myopotential interference with an automatic AV sequential pacemaker (DDD) producing repetitive firing of the ventricular channel up to a rate of 160 and occasional suppression of the ventricular output. A silastic boot which covered the pacemaker did not prevent sensing of electromyopotentials. The problem was partially corrected by decreasing the sensitivity of the ventricular channel. The ventricular response to myopotentials sensed by the atrial channel was limited by decreasing the maximum programmed rate to 120/minute.
Non‐invasive Recording of His Bundle Activity in Patients with Wolff‐Parkinson‐White Syndrome
Authors: ABBOUD SHIMON , BELHASSEN BERNARD , PELLEG AMIR , LANIADO SHLOMO , SADEH DROR
Published: July 2006

Ten patients with Wolff‐Parkinson‐White syndrome underwent external His bundle recording using an advanced signal‐averaging technique. Surface ECG waveforms were recorded and digitized at 1.28 kHz (10 bit resolution) and then averaged with GDC‐6600 computer. A cross‐correlation function, operating in the frequency domain (using the Fast Fourier Transform algorithm) was employed to extract fiducial synchronizing marks for the waveform alignment. Using this technique, reliable His bundle activity could be recorded in nine of ten patients. There was a good correlation between the HQ and HV intervals obtained during external and internal His bundle recordings, respectively, in seven patients who underwent both recordings. Administration of ajmaline enabled to obtain the His bundle activity using a digital filter with low frequency cut‐off of 30 Hz as compared to the cut‐off of 150 Hz which was necessary during control to reduce the electrical activity of the delta wave. We conclude that using a computerized cross‐correlation signal‐averaging technique enables the external His bundle recording in patients with WPW syndrome.
Nine‐year Experience during 1973–1982 with 1,060 Pacemakers in 805 Patients
Authors: HANSON JOHN S. , GRANT MICHAEL E.
Published: July 2006

Our experience with over one‐thousand pacemaker implantations resulting in almost 28,000 patient pacing months is reviewed. Data are presented regarding changing indications for pacing, experience with numerous pacemaker types, patient survival, comparative mortality of sick sinus syndrome and complete heart block, and telephone surveillance. Consistent with some previous reports, there were high one‐ and two‐year post‐implant mortality rates, and advanced age at implant was associated with decreased survival. Males had a significantly higher mortality rate. The period reported covers the transition from utilization of mercury‐zinc batteries to lithium power cells and other new technology; significant differences were observed in device reliability and patient mortality when comparing these eras. Certain patients evidenced disparate survivals, the most notable difference being seen in those who received their primary implants prior to 1976 and subsequent implants of more modern units.
The Isotopic Cardiac Pacer: A Ten‐Year Experience
Authors: SMYTH NICHOLAS P.D. , MILLETTE MARY L.
Published: July 2006

In the past, the battery has been the main cause of pacemaker failure. The isotopic‐powered cardiac pacemaker theoretically should provide greater reliability and longevity than pacemakers powered by chemical batteries. We studied 79 isotopic pacemakers in 75 patients for up to 10 years. Four types of Plutonium 23S powered pacemakers were studied. They included 5 VOO, 51 VVI, 14 VVIP, and 9 VVIM pacemakers. A more diverse group of 93 VVI, VVIP and VVIM pacemakers, powered by chemical batteries, were studied as controls. During the course of study the mercury zinc battery has become obsolete. The increased longevity of the lithium battery, at first very promising, has been compromised by the demands firstly of smaller size, and later of more complex circuits. The longevity and reliability of the isotopic pacemakers has been found to be superior to pacemakers powered by chemical batteries. The isotopic fuel cell, because of its greater longevity, may be needed for the increasingly complex circuits required for dual chamber pacemakers, functioning for the control of bradyarrhythmia alone, or combined with tachyarrhythmia control.
Experience with 407 Transvenous, Finned Pacing Leads with a Sintered Porous‐surfaced Electrode
Authors: FANANAPAZIR LAMEH , MARTIN TONY S. , MARTIN VALERIE , SLAVEN YVONNE , WILKINSON KERRY , BLANE JULIE , BENNETT DAVID H.
Published: July 2006

Experience with 407 transvenous ventricular finned pacing leads with a sintered porous‐surfaced electrode is reported. A low complication rate was encountered: 97% of patients were free from lead‐related complications. Four patients (1%) required re‐operation: two for lead displacement, one for failure to sense spontaneous ventricular activity and one for exit block. A further patient developed exit block which resolved spontaneously. The vast majority of patients had low chronic stimulation thresholds; for example at six months after implantation, the mean threshold for a group of pacemakers with a pulse duration of 0.5 ms was 1.4 ± 0.7 V and for another group with a pulse duration of 0.8 ms it was 1.9 ± 0.7 mA. However, six patients developed a transient high stimulation threshold during the month after implantation, and a high threshold developed in another patient at five months and persisted. Mean acute stimulation and sensing thresholds were satisfactory: 0.7 ± 0.2 V at 0.5 ms pulse duration and 7.6 ± 2.4 mV, respectively.