bluuebunny/crossref_metadata_2025 huggingface dataset:
A Method of Esophageal Electrogram Recording for Diagnostic Atrial and Ventricular Pacing
Authors: PROCHACZEK FRYDERYK , JERZY GAIECKA , STOPCZYK MARIUSZ J.
Published: July 2006

This study evaluates improvement of the electrogram sensed via an esophageal catheter with the sensing electrode adjacent to the stimulating electrode with and without a specialized artifact suppression system. In 100 patients (65 men and 35 women) aged 16–60 years (mean 48 years), esophageal recordings of left atrial activity were obtained during simultaneous transesophageal atrial pacing. Transesophageal ventricular pacing was performed in an additional 34 patients. Without the suppression system, ventricular paced activity, recorded from the esophagus, was not suitable for interpretation. About 10% of the atrial electrogram response could be recorded and evaluated during atrial pacing. With the stimulus artifact suppression system, interpretable recordings were obtained 300% of the time during atrial and ventricular recordings. The method described allows use of transesophageal diagnostic testing where previously only the intracardiac route was possible.
A Prospective Study of Right Ventricular Pulse Pressure and dP/dt to Discriminant‐Induced Ventricular Tachycardia from Supraventricular and Sinus Tachycardia in Man
Authors: WOOD MARK , ELLENBOGEN KENNETH A. , LU BIN , VALENTA HARRY
Published: July 2006

In the future, automatic implantable cardioverter defibrillators (AJCD) may incorporate sensors to differentiate hemodynamically stable from unstable ventricular tachycardias (VT). These sensors should also discriminate between ventricular and supraventricular tachycardias to avoid inappropriate responses from the device. Right ventricular pulse pressure (RVPP) and maximal systolic right ventricular dP/dt (dP/dt) were measured before, during and after 91 episodes of hemodynamically stable VT (VT), hemodynamically unstable VT (VTus), Supraventricular tachycardia (SVT) and sinus tachycardia (ST) induced in 49 male patients. The mean percent changes (mean ± S.E.M.) in RVPP from baseline (%Δ RVPP) during VTS and VTus were −35 ± 3% and −72 ± 3%, respectively (both P < 0.003). The %Δ RVPP during ST was +56 ± 11% (P < 0,01) and %Δ RVPP was unchanged from baseline during SVT(+2 ± 9%; P > 0.01). Mean % change in RVdP/dt from baseline was −20 ± 3% during VTS(P > 0.001), −36 ± 5% during VTus (P < 0.001), +15 ± 13% during SVT (P < 0.01), and +85 ± 23% during ST (P > 0.0l). The mean percent changes in RVPP were significantly different between each arrhythmia group (P < 0.01). The mean % changes in RV dP/dt were significantly different only between ST and VTS or VTUS and between SVT and VTUS. The range of values for %Δ RVPP during VTS overlapped considerably with the ranges of %Δ RVPP during VTuS and SVT. The ranges of %Δ RVPP overlapped minimally between VTus and SVT. Percent change RVPP separated each episode of VTS and VTUS from those of ST. The range of common values for %Δ dP/dt between all four groups was extensive. It is concluded that %Δ RVPP from baseline is significantly different between groups of patients during VTS, VTus, SVT, and ST, but that a large degree of overlap in the range of values for %Δ RVPP and RV dP/dt between different arrhythmias groups may limit the specificity of these hemodynamic variables in separating different arrhythmias.
Electrophysiological Effects of Monophasic and Biphasic Stimuli in Normal and Infarcted Dogs
Authors: WHARTON J. MARCUS , RICHARD VINCENT J. , MURRY CHARLES E. , DIXON ELLEN G. , REIMER KEITH A. , MEADOR JOHN , SMITH WILLIAM M. , IDEKER RAYMOND E.
Published: July 2006

Though some biphasic waveforms significantly decrease the energy required for defibrillation, little is known about the effect of biphasic stimulation on the determination of other electro‐physiological parameters in normal and infarcted hearts. To evaluate this, nine normal dogs and 12 dogs with myocardial infarction had activation threshold (AT), effective refractory period (EEP), strength‐interval curves, and ventricular fibrillation threshold (VFT) determined with constant current stimulation to a pair of right ventricular plunge electrodes, and upper limit of vulnerability (ULV) and defibrillation threshold (DFT) determined with truncated exponential shocks delivered to a pair of wire electrodes coiled to contour the right and left ventricular epicurdium. Each electrophysiological parameter was determined with a 5.5 msec monophasic and 5.5‐msec biphasic (3.5 msec first phase) waveform. Though AT and VFT were not significantly different for the two waveforms, the EttP was significantly longer, the strength‐interval curve shifted rightward, and the threshold for repetitive responses higher for biphasic stimuli. Compared to the monophasic waveform, the ULV and DFT were significantly decreased in a parallel fashion for the biphasic waveform. Neither the presence nor size of myocardial infarction significantly affected any of the measured electrophysiological parameters. In six additional dogs, sigmoid defibrillation probability curves were constructed from biphasic shocks of four energies including that of the DFT and ULV. The ULV energy predicted an effective dose that defibrillated 97% of the time (range 90%–100%). In conclusion, the increased defibrillation efficacy of the biphasic waveform is independent of its ability to activate fully repolarized myocardium and cannot be explained by a greater ability of biphasic waveforms to activate partially depolarized tissue. The parallel decrease in the ULV and DFT for biphasic stimulation and the finding that the ULV energy defibrillates with a high probability of success suggest similar underlying mechanisms for the ULV and defibrillation.
Infection of an Implantable Cardioverter Defibrillator: Management Without Removal of the Device in Selected Cases
Authors: TAYLOR ROBERT L. , COHEN DAVID J. , WIDMAN LAWRENCE E. , CHILTON ROBERT J. , O'ROURKE ROBERT A.
Published: July 2006

A case is presented in which an implantable Cardioverter defibrillator (ICD) became infected in the abdominal wall pocket 5 weeks following implantation. There was no evidence clinically or by computed tomographic scan suggesting mediastinal extension of the infection. The infection was treated successfully by debriding the abdominaJ wall pocket followed by a combination of pocket irrigation with antibiotic solution, parenteraJ antibiotics, and long‐term oral antibiotics. This conservative therapy was and avoided removal of the device.
Infections in Implantable Cardioverter Defibrillator Patients
Authors: WUNDERLY DOUGLAS , MALONEY JAMES , EDEL THOMAS , McHENRY MARTIN , McCARTHY PATRICK M.
Published: July 2006

Implantable cardioverter de;fibrillators fICDsj have been documented as an effective modality in reducing arrhythmic mortality. A serious complication associated with implantation of the device is infection. Few studies have addressed this issue. Two hundred seven patients with refractory ventricular arrhythmias underwent 207 ICD implantations, and 56 subcutaneous generator changes at our institution. Eight patients developed wound infections, four following ICD implantation (4 out of 207 or 1.9%), and four following a generator change (4 out of 56 or 7.1%). Wound cultures most commonly revealed Staphylococcus aurous and Staphylococcus epidermidis. Infections treated with antibiotics alone, or with only generator removal, frequently recurred (four out of five attempts). There were no recurrences following total patch/lead and generator system removal. In jive patients, the same generator unit was successfully emplaned following ethylene oxide sterilization without infection recurrence. We conclude that treatment of device‐associated infection generally requires total generator and patch/lead system removal, and that generator units can be successfully reimplanted yielding substantial cost savings.
Endocardial Pacing Through a Prosthetic Tricuspid Valve
Authors: PERNENKIL R. , WRIGHT J.S.
Published: July 2006

We describe a patient in whom permanent endocurdial pacing was accomplished by passage of the electrode through a porcine bioprosthetic tricuspid valve, thereby obviating the need for a second thoroctomy. After 8 years of follow‐up, the patient continues to do well with satisfactory pacing and bioprosthetic valve function at the first change of pulse generator.
Acute Reversible Diffuse Conduction System Disease due to Lyme Disease
Authors: RUBIN DAVID A. , SORBERA CARMINE , BAUM SETH , MCALLISTER ANNEMARIE , NADELMAN ROBERT
Published: July 2006

During the acute phase of Lyme disease, a 56‐year‐old man without previous heart disease developed complete heart block with alternating left and right bundle branch block pattern QRS complexes. Electrophysiological study performed in the acute phase revealed marked HV prolongation, although the level of heart block was at the atrioventricular node. The heart block was mildly symptomatic and resolved (as did the bundle branch block) with antibiotic therapy. Lyme disease may cause reversible His‐Purkinje disease.
The Effects of Equitation (Horseback Riding) on a Motion Responsive DDDR Pacemaker
Authors: LAMAS GERVASIO A. , KEEFE JAMES M.
Published: July 2006

A graduated sensor indicated response to increased motion levels during equitation was observed in a patient in whom a motion‐detecting pacemaker was implanted. Programmable parameters affecting sensor function were preset according to the sensor response observed during the patient's own slow and fast walk. These parameters were generally appropriate for the variety of gaits the horse used while the patient was on horseback.
The Effect of Rate on Prolongation of Ventricular Refractoriness by Quinidine in Humans
Authors: ROSENHECK SHIMON , SOUSA JQAO , CALKINS HUGH , KADISH ALAN H. , MORADY FRED
Published: July 2006

In this study, the rate dependent effect of quinidine on the ventricular elective refractory period (VERP) was evaluated in 30 patients undergoing electropharmacological testing with quinidine. The VERPs were measured in the baseline state and after at least 2 days of treatment with 1,458–2,044 mg/day of quinidine gluconate (mean plasma quinidine concentration 2.2 ± 0.7 mcg/mL). In 20 patients, the VERP was measured using conventional basic drive trains of 8 beats and basic drive cycle lengths of 600, 500, 400, and 350 msec. In another 10 patients, the VERP was measured after 3 minutes of continuous ventricular pacing at cycle lengths of 600 and 400 msec, and compared to the VERPs measured at the same basic drive cycle lengths using basic drive train durations of 2 and 8 beats. In the baseline state and after treatment with quinidine, the VERP shortened progressively as the basic drive train cycle length decreased and as the drive train duration increased to 3 minutes (P < 0.001). Quinidine consistently prolonged the VERP by 9%–11% (P < 0.001 J, regardless of the basic drive train cycle length. Quinidine's effect was also not affected by the basic drive train duration. In conclusion, the effect of quinidine on VERP in humans is independent of the rate of the basic drive train, both when measured using conventional 8‐beat basic drive trains and when a three minute drive train duration is used in order to attain the maximum effect of the basic drive train cycle length on the VERP. Therefore, in contrast to quinidine's known rate dependent effect on conduction, it's effect on ventricular refractoriness at doses and basic drive train cycle lengths which are used clinically are not rate dependent.
Endocardial Pacing in Infants and Children 15 Kg or Less in Weight: Medium‐term Follow‐Up
Authors: TILL JANICE A. , JONES SUZANNE , ROWLAND EDWARD , SHINEBOURNE ELLIOT A. , WARD† DAVID E.
Published: July 2006

Twenty‐four children 15 kg or less in weight (range 2.8–15 kg) underwent implantation of a permanent pacemaker using the transvenous technique of lead placement. During a follow‐up period of 2 months to 6 years 1 month (median 3 years 6 months) eight children suffered complications, six of which necessitated reoperation. These included: lead fracture in two, infection in two, transient myocardml dysfunction in one, generator migration in one, premature battery depletion in one, and threshold rise in one. A loop of redundant ventricular lead positioned in the atrium at the time of implant is successfully unravelling in all children. One child died during the follow‐up period of a pneumonia unrelated to her pacemaker. The other children are growing and developing normally and the cosmetic appearance has proved acceptable in all cases.
Effects of Increasing Heart Rate Induced by Efferent Sympathetic Neuronal Stimulation, Isoproterenol or Cardiac Pacing on Myocardial Function and Oxygen Utilization
Authors: GARDNER MARTIN J. , JOHNSTONE DAVID E. , JANES RONALD D. , KLASSEN GERALD A. , ARMOUR J. ANDREW
Published: July 2006

The effects of increasing heart rate by six different methods on cardiac /unction were investigated in 17 open‐chest anesthetized dogs. Heart rate was increased approximately 30% by (1) right interganglionic nerve stimulation, (2) atrial pacing, (3) ventricular pacing, (4) atriovenfricular sequential pacing, (5) right stellate ganglion stimulntion, and (6) isoproterenoi administration. During heart rate increases induced by atrial pacing left ventricular intramyocardial pressure, coronary Wood flow, oxygen delivery per unit of myocardial oxygen consumption, and myocardial efficiency were unchanged. Ventricular pacing reduced left ventricular cavity and septal intramyocardial pressure, while circumflex coronary flow increased, resulting in reduced oxygen delivery relative to myocardial oxygen consumption. Similarly, atrioventricu‐lar sequential pacing increased circumflex coronary artery flow and myocardial oxygen consumption, and decreased septal intramyocardial pressure and oxygen delivery per unit of myocardial oxygen consumption. Right stellate ganglion stimulation and isoproterenol increased left anterior descending and circumflex coronary artery blood flow, intramyocardial pressure, and myocardial oxygen consumption. Estimated myocardial efficiency (left ventricle) was decreased by ventricular pacing and isoproterenol, and was unchanged by atrial pacing and right interganglionic nerve stimulation. Increases in heart rate induced by right interganglionic nerve stimulation did not alter myocardial oxygen consumption, or the index of cardiac efficiency. It is concluded that augmentation of heart rate by either ventricular or atrioventricular pacing impairs myocardial function so that there is a decrease of left ventricular efficiency, and isoproterenol augments chronotropism and myocardial force relative to cardiac external work so there is a reduction in cardiac efficiency. In contrast, atrial pacing or right interganglionic nerve stimulation augments chronotropism such that myocardial oxygen consumption and efficiency are unchanged.
Computer‐Enhanced Mapping of Activation Sequences in the Surgical Treatment of Supraventricular Arrhythmias
Authors: BUCKLES DAVID S. , HAROLD MARK E. , GILLETTE PAUL C. , CASE CHRISTOPHER L. , CRAWFORD FRED A.
Published: July 2006

Surgical treatment of accessory pathways and ectopic foci requires accurate information on the physical locations of the arrhythmogenic substrates. AJthough electrophysiology studies during cardiac catheterization frequently provide accurate and reliable data, the physical locations of the sites to be ablated must be verified in situ by electrical activity mapping. We have developed a microcomputer‐based system that facilitates creation of electrical activity maps, supplanting the manual method formerly used. Signals produced by mapping and reference electrodes, as well as cardiac diagrams with grid coordinates and times, are presented on a monitor in formats that are easily interpreted by the surgeon and cardiologist. The system is rapid, accurate, and reliable, and has reduced the time required to localize conduction abnormalities from 30 to 45 minutes for the manual method, down to an average of 12 minutes per case. The system is simple to operate, requiring only minimal training. All of the components of the system are commercially available; no specialized hardware is required.
Vasovagal Syncope: Diagnostic Role of Head‐Up Tilt Test in Patients with Positive Ocular Compression Test
Authors: JAEGER FREDRICK J. , SCHNEIDER LORI , MALONEY JAMES D. , CRUSE ROBERT P. , FOUAD‐TARAZI FETNAT M.
Published: July 2006

We investigated the relative merits of the ocular compression test and the head‐up tilt test to aid differentiation of syncope and seizures in young patients. Sixteen patients (10 males and 6 females) with a mean age of 14 ± 4.7 (SD) years (range 7–22 years) underwent graded head‐up till (15°, 30°, and 45° for 2 minutes each, then 60° for 20 minutes) following positive ocular compression testing defined as precipitation of asystole for at least 3 seconds (mean 5 seconds ± 2 seconds, range 3–12 seconds). Each patient presented with recurrent unexplained loss of consciousness (mean number of episodes 30 ± 45, mean duration of illness 52 ± 40 months), and seven patients were receiving anticonvulsant medications, three of these had normal EEGs. Eleven patients (69%) developed vasovagal syncope during head‐up tilt, reproducing their clinical episodes (systolic blood pressure decreased from 105 ± 10 mmHg to 84 ± 13 mmHg, diastolic blood pressure from 75 ± 9 to 22 ± 25 mmHg, and heart rate from 89 ± 13 beats/mm to 37 ± 20 beats/min). Asystole occurred in two patients during vasovagal syncope lasting 11 seconds in one and 16 seconds in the other, and, it was associated with myoclonic movements in both (convulsive syncope). Based on these findings, and given the perceived potential hazards of the ocular compression test, the head‐up tilt test may be a safer procedure that adds useful information to the diagnostic evaluation of these patients.
The Fundamental Law of Electrostimulation and its Application to Defibrillation
Authors: IRNICH WERNER
Published: July 2006

Around the turn of the last century, there was an intensive discussion among physiologists as to whether there is a law describing the phenomena of electrostimulation and which formula may best approximate it mathematically. J.L. Hoorweg found in 1892 that the voltage at which a capacitor must be charged to elicit an excitation, was a function of the capacitance in an inverse correlation. G. Weiss reported in 1901 that according to his investigations a linear relationship existed between the duration of a pulse and the corresponding quantity of electricity applied and called it “formule fondamentale.” We are now able to give the “fundamental formula” a physical interpretation that yields, as result, the electric field produced by the electrode acting on the excitable membrane. The electric field in the extracellular space is transformed by the cell geometry ratio: cell length to membrane thickness yielding a high transmembranefield capable of reducing the inherent electric field to its threshold level. The consequences drawn from this hypothesis are remarkable and (should) have an influence on all applications of electrostimuiation including the discussions on defibrillation. The application of the stimulation theory to defibrillation yields as results: (1) The basic engineering principle of defibrillation is to produce an electric field within the ventricles of 400 V/m or more. An orthogonal pulse application may reduce the energy requirements, as more fibers are longitudinally reached by the electric field; (2) The shape of the defibrillation pulse and its polarity plays no role. Consequently it follows that biphasic pulses must be less efficient than monophasic pulses, if they are close to the chronaxie; and (3) The most serious disadvantage in today's defibrillation practice is its dose characterization in “energy”; but this physical quantity cannot be justified in the light of the fundamental law of electrostimulation.
Monitoring the Radiation Dose to a Multiprogrammable Pacemaker During Radical Radiation Therapy: A Case Report
Authors: MULLER‐RUNKEL R. , ORSOLINI G. , KALOKHE U.P.
Published: July 2006

Multiprogrammable pacemakers, using complimentary metaloxide semiconductor (CMOS) circuitry, may fail during radiation therapy. We report about a patient who received 6,400 cGy for unresectable carcinoma of the left lung. In supine treatment position, arms raised above the head, the pacemaker was outside the treated area by a margin of at least 1 cm, shielded by cerrobend blocking mounted on a tray. From thermoluminescent dosimeter (TLD) measurements, we estimate that the pacemaker received 620 cGy in scatter doses. Its function was monitored before, during, and after completion of radiation therapy. The pacemaker was functioning normally until the patient's death 5 months after completion of treatment. The relevant electrocardiograms (ECGs) are presented.
Stimulation Characteristics of a Steroid‐Eluting Electrode Compared with Three Conventional Electrodes
Authors: KLEIN HERMANN H. , STEINBERGER JOSEF , KNAKE WIGAND
Published: July 2006

Stimulation thresholds of a steroid‐eluting electrode (Medtronic CapSure 4003, 9 patients) were compared with three conventional electrodes (carbon‐tipped lead, Siemens‐Elema 423 S/60, 10 patients; Elgiloy‐tipped lead, Cordis Encor, 10 patients; platinum‐tipped lead, Telectronix Laserdish 030–276, 9 patients). Voltage thresholds were determined during implantation, 1–3 days, 6 weeks, and 6 months postimplantation. No significant difference among the four electrodes was found in regard to stimulation and sensing behavior during implantation. Compared to intraoperative measurements, mean increase in voltage threshold and absolute voltage thresholds were substantially Jess for the steroid‐eluting electrode than for the other tested electrodes 6 weeks and 6 months after implantation. The rheobasechronaxie product, a parameter of the stimulation performance of electrodes, underlined the superior pacing characteristics of the steroid‐eluting electrode. To achieve low chronic stimulation threshold by pharmacological means is an attractive direction for future electrode technology.
The Mechanism of Flutter Interval Alternans
Authors: WAXMAN MENASHE B. , KIRSH JOEL A. , CAMERON DOUGLAS A. , WALD ROBERT W.
Published: July 2006

The mechanism of atrial flutter alternans was investigated by observing the effects of ventricular systole on gutter intervals in a patient with atrioventricular dissociation. Interval measurements were made both from atrial electrograms recorded from an esophageal electrode, and from surface ECG recordings. Flutter cycle intervals that occurred during a well‐defined period subsequent to ventricular systole were consistently prolonged by up to 30 msec relative to the baseline flutter cycle interval. This prolongation was observed in two vastly different electrode configurations, implying that motion artifact was not predominantly responsible. We concluded that, by altering the characteristics of the flutter reentry circuit, transient increases in atrial volume and/or pressure arising during ventricular systole were responsible for the lengthening of the flutter cycle intervals.
Rate Responsive Pacing with a Minute Ventilation Sensing Pacemaker during Pregnancy and Delivery
Authors: LAU CHU‐PAK , LEE CHIN‐PENT , WONG CHEUK‐KIT , CHENG CHUN‐HO , LEUNG WING‐HUNG
Published: July 2006

A minute ventilation sensing rate responsive pacemaker was implanted in a 29‐week pregnant woman with symptomatic complete atrioventricular (AV) block under echocardiographic and electrocardiographic (EGG) guidance. Satisfactory rate responses during a submaximal treadmill exercise test and daily activities were achieved. The course of pregnancy and cesarean section is discussed. During the cesarean section and after the delivery of the baby, changes in the ventilator settings confirmed that the pacing rate was closely correlated with both the tidal volume (r = 0.94, P<0.02) and the respiratory rate (r = 0.93, P < 0.05).
Two Accessory Pathways, Dual AV Nodal Conduction, and 1:2 Ventriculoatrial Conduction in a Patient with Multiple Supraventricular Tachycardias
Authors: ROSENFELD LYNDA E. , BATSFORD WILLIAM P.
Published: July 2006

Multiple Supraventricular tachycardias were induced in a patient with two left posterior accessory pathways and dual afrioventricular nodal conduction. One of the accessory pathways conducts slowly and exhibits decremental conduction. A “double retrograde response” (2:1 ventriculoatrial conduction) due to simuJtaneous retrograde propagation of a single ventricular depolarization over two longitudinally dissociated pathways plays a role not only in tachycardia initiation, but in the maintenance of a unique, irregular tachycardia.
Chronotropic Response to Exercise in Patients with Atrial Fibrillation
Authors: CORBELLI RICHARD , MASTERSON MARTIN , WILKOFF BRUCE L.
Published: July 2006

The exercise chronotropic response of patients with chronic atrial fibrillation requiring pacemaker therapy for bradycardia was assessed to characterize the chronotropic response and identify patients who would potentially benefit from a rate adaptive pacemaker. The population consisted of all patients who received a VVI pacemaker between January 1980 and November 1987 who underwent exercise tolerance testing (n = 130) and were in atrial fibrillation (n = 19). There were 11 males and 8 females with a mean age of 62 ± 14 years. Left ventricular function was normal in eight patients, mildly impaired in three, and severely impaired in two. Long‐term medications were continued until the morning of the test; digoxin 73%, beta blockers 21%, calcium channel blockers 26%, and nitrates 21%. Maximal exercise tolerance tests were performed. Parameters assessed were: (a) heart rate at rest, the end of each stage, and at peak exercise; (b) percent heart rate reserve per stage; and (c) percent metabolic reserve per stage. Results were compared to 100 normal subjects on no medications and without evidence of medical illness or cardiac disease. Heart rates were depressed in 58% of the study patients (21% early, 53% late) and elevated in 74% (74% early, 32% late). All 19 (100%) patients had abnormal heart rate responses at some point during the exercise test. Only four patients (21%) had a response within one standard deviation from the mean of the normal population during either the early or late segment of the exercise test. Patients in chronic atrial fibrillation requiring pacemakers for bradycardiac support at rest have an abnormal chronotropic response to exercise. Analysis of the heart rate response identifies disproportionately rapid and/or slow heart rates during exercise. Seventy‐four percent exhibited the need for more extensive medical therapy and 58% showed the need for additional chronotropic pacemaker support.
An Automatic Microcomputer System for Analysis of Monophasic Action Potentials
Authors: KANAAN NABIL , JENKINS JANICE , KADISH ALAN
Published: July 2006

A computer system for rapid measurement and analysis of monophasic action potentials (MAPs) recorded in vivo was developed. MAPs recorded from the epicardium of mongrel dogs using a contact electrode were digitized by analog‐to‐digital conversion at a sampling rate of 1 kHz per channel for computer data acquisition. Activation time was detected using a sliding 10‐point window at the location where the average positive dV/dT exceeds an adjustable threshold value in order to eliminate spurious detection due to baseline variability or motion artifact. Action potential duration fAPDJ was determined at 50% and 90% (APD50, APD90) repolarization levels at the first sample point below these defection levels. In addition, a tangent algorithm (APD,tan) that detects peak negative dV/dT during repolarization was developed. APDtan was determined from the location of onset of activation to the intersection of the tangent and baseline. APDtan allowed estimation of APD in the presence of subsequent premature beats when APD80 was not measurable. To validate activation time measurements, 4,600 action potentials were analyzed during fixed rate pacing. Over a range of paced coupling intervals from 200 to 1000 msec, an R2 value of 0.99968 and a slope of 0.9959 were obtained by linear regression between paced and calculated intervals. To validate APD measurements, 5035 action potentials were analyzed in five animals during fixed rate pacing (longer than 3 minutes) when action potential duration should be constant. Average coefficients of variation of 1.25%, 1.65%, and 1.14% were obtained for APD50, APD90, and APDtan, respectively. This algorithm provides a rapid and accurate method to analyze MAP activation and duration for basic physiological studies such as the determination of initiation of arrhythmias.
Cardiac Pacing in Unilateral Left Superior Vena Cava: Evaluation by Digital Angiography
Authors: VILLANI GIOVANNI QUINTO , PIEPOLI MASSIMO , QUARETTI PIETRO , DIECI GIOVANNI
Published: July 2006

In a patient with complete heart block and chronic lymphocytic leukemia a pacemaker lead could not be introduced from either the right or left subclavian vein. Digital subtraction angiography excluded a neoplastic inediustinal mass, demonstrated a unilateral left superior vena cava and defined the best route for lead insertion.
Effects of Transcatheter Cardioversion on Chronic Lone Atrial Fibrillation
Authors: KUMAGAI KOICHIRO , YAMANOUCHI YOSHIO , HIROKI TADAYUKI , ARAKAWA KIKUO
Published: July 2006

The effectiveness and safety of internal transcatheter Cardioversion on chronic lone atrial fibrillation were examined in ten patients resistant to external electrical (400 joules) and pharmacological Cardioversion. Transcatheter Cardioversion was performed by pulling back the atrioventricular junction catheter just inferior to the site of the His‐bundle recording and delivering the shock between a proximal electrode (cathode) and backplate (anode). Transcatheter Cardioversion restored sinus rhythm in all of the ten patients. The only complication observed was transient atrioventricular block after the shock and this was treated by temporary pacing. However, atrial fibrillation recurred in five patients at 30, 27, 52, 1, and 6 days, respectively. A second attempt at transcatheter Cardioversion was performed in those patients and was successful in three patients. During a follow‐up period ranging from 12 to 22 months, eight patients continued in sinus rhythm. Thus, transcatheter Cardioversion is considered effective and safe in selected patients with chronic lone atrial fibrillation in whom external Cardioversion was unsuccessful.
A Method for Analysis of the Local Atrial Evoked Response for Determination of Atrial Capture in Permanent Pacing Systems
Authors: CURTIS ANNE B. , MAAS STEVEN M. , DOMIJAN ALEXANDER , KEIM STEPHEN G. , DURAN AURELIO
Published: July 2006

We developed a method for detection and analysis of the local atrial evoked response. Eleven patients undergoing permanent dual chamber pacemaker implantations for standard clinical indications were included in the study. Using a pacing system emulator, charge balancing using a variable triphasic stimulus waveform to reduce polarization artifact amplitude was performed first. This could not be completed in one patient because of a poor signal‐to‐noise ratio. Subsequent analysis of the local atrial evoked response in the remaining ten patients showed the typical signal to be a biphasic waveform with an initial negative deflection followed by a positive deflection nearly equal in amplitude. The mean amplitude of the atrial evoked response was 3.1 ± 1.4 mV, while the intrinsic P wave amplitude in these same patients averaged 5.6 ± 3.0 mV. The summed evoked response, a parameter that is directly proportional to the area of the signal, was used to determine atrial pacing threshold. The median atrial pacing threshold determined by the algorithm was 1.00 V, There was no instance of failure to detect loss of capture, nor was loss of capture inaccurately determined when there was still successful atrial pacing. Atrial capture in permanent pacing systems can thus be determined using an algorithm to record and analyze the local atrial evoked response. This method could potentially be useful in the automatic determination of atrial pacing threshold.
Successful Catheter Fulguration of the His Bundle in a Postoperative Mustard Patient after Unsuccessful Fulguration of Ectopic Atrial Foci
Authors: GREENE CRAIG A. , CASE CHRISTOPHER L. , GILLETTE PAUL C.
Published: July 2006

Incessant supraventricular tachycardia (SVT) resistant to pharmacological agents may cause cardiac dysfunction requiring more aggressive therapy. We present the case of a 12‐year‐old postoperative Mustard patient who developed biventricular heart failure due to an atrial ectopic tachycardia resistant to amiodarone. Using endocavitary direct current figuration techniques, catheter ablation of the His bundle ivas successfully performed after unsuccessful attempts at ablation of the ectopic atrial foci. After placement of a permanent transvenous rate responsive ventricular pacemaker, the patient's clinical status and cardiac function improved. Endocavitary fulguration of the His bundle is technically feasible after the Mustard procedure and should be considered for treatment of selective cases of pharmacologically resistant SVT.
One‐Year Follow‐Up of Automatic Adaptation of the Rate Response Algorithm of the QT Sensing, Rate Adaptive Pacemaker
Authors: BAIG M.W. , BOUTE W. , BEGEMANN M. , PERKINS EJ.
Published: July 2006

Optimal functioning of a rate adaptive pacemaker depends upon reliable sensing of the sensor and appropriate programming of the rate response algorithm. QT sensing pacemakers use data derived from the endocardial electrogram in the programming of the rate response algorithm. In the latest versions of these pacemakers, programming of the rate response algorithm may be performed using either a semiautomatic Fast Learn (FLJ procedure or by using the newly developed, fully Automatic Slope Adaptation (ASA) mechanism. We report our experience in a prospective study of 17 patients in the first year postimplantation. ASA was characterized by significant changes only in the values of the slope settings at the lower rate limit (3.7 msec/msec at time 0 to 5.77 msec/msec at 2 weeks, P < 0.001) during the first 2 weeks after its enablement. Further adaptation between weeks 2 to 4 was observed (5.77 msec/msec to 6.4 msec/msec, P = 0.2) but this was not significant. The slope settings derived using the FL procedure were also checked at 2 and 4 weeks and were reproducible. They were closest in value to the values attained by the automated mechanism at 4 weeks. This suggests that the final value of the slope setting at the lower rate limit using ASA is reached between weeks 2 to 4. Both methods of slope determination result in satisfactory and similar rate response profiles but the time to achieve slope stability will necessarily be slower with ASA.
The Epidemiology of Pacemaker Implantations in Fyn County, Denmark
Authors: ANDERSEN GLAUS , GREEN ANDERS , MADSEN GUNNAR M. , ARNSBO PER
Published: July 2006

Throughout the last three decades the number of patients with pacemakers has increased. Registers of pacemakers and pacemaker patients have been established to monitor, for example, the battery life expectancy and patient data. We have analyzed the registry for Fyn county, Denmark, which includes data on incidence, prevalence, and mortality rates among patients with pacemakers during the period from 1964 to 1990. The analyses show that the prevalence rate is steadily increasing as a result of a combination of an increasing incidence rate and a stable mortality rate among the pacemaker patients. Based on the development in the first almost 30 years of pacemaker implantations, two trends of the future prevalence of pacemaker patients are projected. Provided constant mortality rates and expected incidence rates of 300 per million person years and 350 per million person years, respectively, the prevalence will reach a plateau of 2.7 per 1,000 persons and 3.1 per 1,000 persons, respectively, within the next 25 years.
DDIR Versus VVIR Pacing in Patients with Paroxysmal Atrial Tachyarrhythmias
Authors: VANERIO GABRIEL , MALONEY JAMES D. , PINSKI SERGIO L. , SIMMONS TONY W. , CASTLE LON W. , TROHMAN RICHARD G. , WILKOFF BRUCE L.
Published: July 2006

Patients with sinus node dysfunction (SND) in particular those with tachycardia‐bradycardia syndrome and patients undergoing atrioventricular nodal ablation procedures for refractory paroxysmal atrial tachyarrhythmias (PAT), are candidates for single chamber (VVIR mode) or dual chamber rate responsive (DDIR mode) systems. To evaluate the benefits and disadvantages of each pacing mode we retrospectively analyzed 33 patients with a history of frequent PAT who received a VVIR (22 patients); or a DDDR pacemaker (11 patients) programmed to the DDIR mode. The mean follow‐up time was 25 and 18 months, respectively. Preimplant left atrial diameter was significantly smaller in the DDIR group. Chronic atrial fibrillation developed in 54% of the VVIR patients and 27% of the DDIR group, but this difference was not significant. Complications of patients with VVIR pacemakers included new mitral and tricuspid insufficiency, stroke, pacemaker inlolerance and aggravated congestive heart failure. Patients with DDIR pacemakers had a lower incidence of symptoms and complications. However, this group received more antiarrhythmic medication, required a closer follow‐up, and their pacemakers needed frequent reprogramming. Our findings suggest that VVIR is a poor choice for patients with SND, congestive heart failure, and PAT, and that DDIR may be an acceptable alternative.
Undersensing as a Consequence of Lead Incompatibility: Case Report and a Plea for Universality
Authors: COSTEAS XENOPHON F. , SCHOENFELD MARK H.
Published: July 2006

Implantation of a single chamber bipolar pulse generator was complicated by transient Joss of ventricular sensing, caused by mechanical damage to the unipolar lead connected to the system. A perforation of the insulating sheath was found at the site of the proximal connector block, and undersen‐sing resolved after restoring its integrity with silicone adhesive. The ability to attach an unprotected univocal lead to a bipolar connector, shared by the Voluntary (VS‐1) and International (IS‐1) designs, invites the possibility of injury to the insulating sheath by accidental tightening of the proximal screw. There is thus an urgent need for the development and universal adoption of a robust interface standard in lead connector design.
The Role of Diastolic Outward Current Deactivation Kinetics on the Induction of Spiral Waves
Authors: KOGAN BORIS Y. , KARPLUS WALTER J. , BILLETT BRIAN S. , PANG ALEX T. , KHAN STEVEN S. , MANDEL WILLIAM J. , KARAGUEUZIAN HRAYR S.
Published: July 2006

The mechanism of induced reentry in an initially homogeneous repolurization matrix still remains undefined, In the present study we hypothesized that the slow deactivation rate of the delayed outward current (dIo/dt), which occurs during diastole after complete repolarizafion, can cause activation failure and facilitate reentry. We modeled the excitation‐recovery process using the modified FilzHugh‐Nagumo equations in a two‐dimensional medium of 128 by 128 cells using the Connection Machine (CM‐2), a massively parallel computer that is highly suitable for this class of problem. The model was one cell thick, uniformly excitable, and isofropic. When (he rate of Io deactivation was slowed to yield action potential duration (APD) restitution curves similar to experimentally observed arrhythmic ventricular muscle cells APD restitution curves, premature stimulation (S2) induced nonstationary double spiral waves (Figure 8 reentry). A decrease in d/o/dt increased the radius of the circle around which the iip of the spiral waves rotates and decreased its angular velocity. Wave fronts propagated through areas where the residual dia‐stolic Io was fully inactivated and blocked in areas where its amplitude was high. No such dynamics of wave front propagation could be induced when S2 was applied after the completion of lo deactivation. We conclude that the kinetics of deactivation of the Io during diastole has a profound influence on the dynamics of two‐dimensional wave front propagation. The similarities of the APD restitution curve implemented in the computer model with slow deactivation of Io and that observed in our canine model of quinidine induced ventricular fachyarrhythmias suggest that Io deactivation kinetics may play an important role in arrhythmogenesis in the intact ventricle.
A Massively Parallel Computer Model of Propagation Through a Two‐Dimensional Cardiac Syncytium
Authors: FISHLER MATTHEW G. , THAKOR NITISH V.
Published: July 2006

A computer model of electrical propagation through a two‐dimensional (2D) sheet of cardiac tissue has been developed to run on the massively parallel processor Connection Machine (CM‐2) computer. The transmembrane ionic currents in each of 16,384 (128 ± 128) 100 ± 100 μm2 patches of cardiac tissue are described by modified Beeler‐Reuter membrane equations. These equations, along with the parabolic differential equation derived from 2D cable theory, are solved in parallel to study normal and abnormal 2D propagation. The sheet is paced with planar waves at a basic cycle length of 500 msec (control). When a premature ectopic stimulus of sufficient strength and appropriate timing is then applied to a local region of the syncytium, one of two types of reentry is observed: (a) stable figure‐of‐eight reentry, or (b) unstable but self‐sustaining “fibrillation‐like” reentry. During this fibrillatory activity, action potential durations are 79.8 ± 36.8 msec (control = 244.9 ± 0.9 msec) and coupling intervals average 96,7 ± 31.3 msec (control ‐ 500 ± 0 msec). We also observed that passive eJectroluni‐cally‐induced depolarization of already refractory tissue extended the refractory period of that tissue, and that the duration of this extension depended on the magnitude of the electrotonic effect.
Effects of Procainamide on Refractoriness, Conduction, and Excitable Gap in Canine Atrial Reentrant Tachycardia
Authors: KUS TERESA , DERAKHCHAN KATAYOUN , BOUCHARD CAROLINE , PAGÉ PIERRE
Published: July 2006

The effects of procainamide were studied in a model of atrial flutter around the tricuspid valve in seven open chest, chloralose‐anesthetized dogs (31 ± 3 kg). A Y‐shaped incision in the intercaval area extending to the right atrial appendage was made and five bipolar electrodes were sutured on the atrial epicardium around the tricuspid valve. Reentry tachycardia was induced in the absence and presence of drug by burst pacing. Procainamide (5 mg/kg bolus followed by 0.075 mg/kg/min infusion) produced stable plasma levels (38 ± 9μ) during the study. At a pacing cycle length of 200 msec, mean (± SD) diastolic threshold at the five sites increased from 1.6 ± 1,5 to 2,0 ± 1.7 mA and mean atrial effective refractory period from 128 ± 9 to 140 ± 16 msec on drug (P < 0.05). Procainamide prolonged the cycle length of atrial flutter from 144 ± 10 to 160 ± 13 msec and slowed conduction velocity during atrial flutter around the tricuspid valve from 73 ± 6 to 66 ± 6 cm/sec (P < 0.05). A reset response curve was determined by introducing premature stimuli during atrial flutter. Procainamide prolonged effective refractory period during atrial flutter from 101 ± 13 to 116 ± 17 msec but did not change the duration of the excitable gap (38 ± 9 vs 40 ± 18 msec). Although the reset response curve was predominantly increasing, in six of seven experiments there was present a flat portion at long coupling intervals approaching the atrial flutter cycle length that comprised 23%± 10% of the excitable gap. Procainamide shifted the reset response curve upward and to the right but did not change its slope or the duration of the flat portion. Thus, in the majority of experiments the reset response curve in atrial flutter about the tricuspid valve in vivo suggests that procainamide prolongs atrial flutter cycle length directly by slowing conduction through fully excitable tissue rather than indirectly by increasing refractoriness at the head of the wave front.
Nonphysiological Left Heart AV Intervals as a Result of DDD and AAI “Physiological” Pacing
Authors: CHIRIFE R. , ORTEGA D. F. , SALAZAR A. I.
Published: July 2006

DDD and AAI pacemakers are considered physiological, since they preserve atrioventricular (AV) synchrony. Artificial pacing, however, is performed largely from right heart chambers, causing aberrant depolarization pathways. Pacing at the right atrial appendage (RAP) is known to delay left atrial contraction due to interatrial conduction time (IACT), and right ventricular (RV) apical pacing (RVP) delays left ventricular (LV) contraction due to interventricular conduction time (TVCT). These delays may render the left heart AV intervals (LAV) either too short or too Jong, thus affecting LV systolic function. The purpose of this study was to evaluate the actual LAV intervals during conventional, right heart AAI and DDD pacing. Resulting LAV intervals were compared to programmed AV values during all DDD pacing modalities. Ten patients with DDD and six patients with AAI pacemakers were studied. IACT was measured from the atrial spike to the onset of left P wave, as recorded by an esophageal lead. Systolic time intervals were measured using either a carotid pulse tracing or a densitogram (photoplethysmography). LV function was appraised by measuring rate‐corrected LV ejection time (LVETc). IVCT was measured indirectly as the lengthening of LV preelection period (PEPJ caused by RV pacing, as compared to normal depolarization pathway. Intrinsic‘ACT and IVCT were considered zero. Right heart AV intervals (RAV) were measured from surface ECG and LAVs were calculated according to the following equations: Sinus Rhythm: LAV = RAV; Atrial Pace 4‐ Ventricular Sense: LAV= RAV − IACT; Atrial Sense + Ventricular Pace: LAV = RAV + IVCT; Sequential AV Pace: LAV = RAV − IACT + IVCT, Results: 1. IACT: mean = 73 msec, range: 35–130; IVCT: mean = 50 msec, range: 44–100. 2. Compared to RAVs, LAVs were either too short or too long (−130 to + 300 msec: P < 0.001 J in RAP 4‐ RVS and RAS + RVP. Conclusions: 1. LAV differed significantly from RAV during AP + VS and AS + VP. 2. “Physiological” RAV intervals in DDD and AAI may cause nonphysiological LAV, possibly affecting LV function. 3. IACT and IVCT should be accounted for when programming DDD PM to provide physiological LAV.
Applicability of the Stimulus‐T Interval for Antitachycardia Pacing
Authors: DULK KAREL den , LEERSSEN HENNY , VOS MARC , LEUNISSEN JET , DASSEN WILLEM , KERSEMAKERS JAN , ANN MALCOLM BEGEM , WELLENS HEIN
Published: July 2006

At (he onset of tachycardia, the refractory period (RP) changes together with the tachycardia terminal ion window. We evaluated dogs with total atrioventricular (AV) block lo determine if stimulus‐T interval (STJ) can be used to adjust the coupling interval(s) of an antitachycardia pacemaker in relation to changes in HP. Endocardial STI was recorded continuously together with six surface EGG leads. Steady‐state (> 2 miii) RP was determined for drive cycle lengths (DCL) 400 msec and 900 msec. The test pulse (TP) coupling interval, with DGL 900 msec, was chosen to be equal to (he RP of DCL 400 msec, DCL was then changed to 400 msec until TP captured. STI of DCL of beat before capture was gained was measured. DCL was then changed back to 900 msec and the interval determined when capture was lost. TP was then lengthened In 5 msec and the procedure repeated until TP captured immediately upon changing to DCL 400 msec. Results: The difference between RP at onset of pacing at DGL of 400 msec and RP when capture n us achieved with the shortest coupling interval was 35–50 (mean 40) msec. This required 35–90 (mean 62) seconds. The correlation coefficient RP to STI was > 0.95. Conclusions: (1) RP changed by as much as 35–50 msec at the: onset of an abrupt increase in rate in a 35–90‐second period; and (2) STI enables estimation of RP on a beat‐to‐beat basis. Capture can therefore be preditrd from the previous beat mid the coupling interval adjusted accordingly in an antitachycardia pacing mode.