bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural and Unnatural History of Patients with Severe Carotid Sinus Hypersensitivity: A Preliminary Study
Authors: BRIGNOLE MICHELE , MENOZZI CARLO , LOLLI GINO , SARTORE BRUNO , BARRA MAURO
Published: July 2006

Natural history of patients with symptomatic severe carotid sinus hypersensitivity is not clearly known. In order to evaluate the effectiveness of pacing therapy in these patients we performed a randomized treatment/no‐treatment prospective study in 35 patients. They were randomly assigned to two groups: 19 patients received no therapy, 16 patients received a VVI (# 11) or DDD (#) pacemaker implant. During the 8.4 ± 4.3 month follow‐up period patients receiving no therapy had recurrence of syncope in 9 cases (47%) and minor symptoms in 13 (68%); at the 16th month, actuarial curve showed absence of syncope in 36% of patients and of any symptoms in 30%. During the 7.2 ±4.1 month follow‐up period, the patients receiving the pacemaker implant had no recurence of syncope, minor symptoms in three (19%); at the 16th month, actuarial curve showed absence of syncope in 100% of patients and of any symptoms in 78%. During follow‐up, 12 patients in no‐treatment group received a pacemaker implant because of the recurrence of severe symptoms; successively they had a strong reduction of symptoms. In conclusion, this study definitively demonstrates that patients with severe symptomatic carotid sinus hypersensitivity had a high rate of recurrence of spontaneous symptoms and that in these patients cardiac pacing is a useful therapy.
Atrioventricular Conduction in Sick Sinus Syndrome
Authors: CARISMA MA. BELEN O. , MANALO JUANCHO M. , CHUA WILLIAM T.
Published: July 2006

With the increasing recognition of the pacemaker syndrome and with the availability of newer methods of pacing therapy, the status of the atrioventricular (AV) conduction in patients with Sick Sinus Sydrome (SSS) becomes crucial in the choice of mode of pacing. At the Philippine Heart Center, from April 1983 to November 1986, the sinus and AV node function studies of 46 patients who, by electrophysiological studies had sinus node dysfunction (SND)‐SN recovery time (SNRT) >1400 msec, were reviewed. These were arbitrarily classified according to duration of SNRT into: Group A—borderline SND, SNRT from 1,401 to 1,499 msec (n = 4); Group B—mild SND, SNRT from 1,500 to 2,499 msec fn = 25); Group G—moderate SND, SNRT from 2,500 to 3499 msec fn = 6); Group D— severe SND, SNRT of 3,500 m and above (n = 11). Out of the 46, 14 (30%) had concomittant AVN dysfunction (AVND)—antegrade block rate < 130 beats per minute (BPM). The percentage occurrence of AVND was noted as follows: Group A—25% (1/4); Group B—28% (7/25); Group G—50% (3/6); Group D—27% (3/11). Out of the 14 patients with concomittant AVND, 5(35%) had antegrade block rate < 100 BPM, 3 in Group R and 2 in Group D. The study shows that AVND occurs in only 30% of SSS patients. Its occurrence and severity has no bearing on the degree of SND. In these, antegrade block was at a rate higher than 100 BPM in the majority of patients. The data suggest that most of SSS patients may benefit from atrial demand pacemaker which therapeutically is of more advantage over the ventricular demand type inasmuch as AV synchrony is retained, thus pacemaker syndrome is prevented.
Assessment of VVI Diagnostic Pacing Mode in Patients with Cardioinhibitory Carotid Sinus Syndrome
Authors: MENOZZI CARLO , BRICNOLE MICHELE , PAGANI PAOLO , LOLLI GINO , CASALI GIUSEPPE
Published: July 2006

In this study, we used Holter pacemakers in a group of 13 patients affected by severe carotid sinus syndrome in order to evaluate its evolution. All the patients had one to three syncopal episodes and frequent other symptoms such as fainting, dizziness, lightheadedness and pre‐syncope interferring with their daily activity so that pacemaker therapy was considered necessary. Patient selection criteria were: presence of the isolated cardioinhibitory type, absence of associated sinus dysfunction and absence of symptomatic WI pacemaker effect. All the patients received a Micropacer 1 device; among special functions, bradycardia events counter was activated and programmed so that each sequence of three consecutives beats at a cycle length 1.5 sec (i.e., 4.5 sec total interval) could he recognized and stored in its memory. The follow‐up lasted 13±7 months. Brady events occurred in eight out of 13 patients (62%), during this period. Syncope and major symptoms disappeared in ail the patients; mild dizziness recurred rarely in two patients and were not linked to brady‐events recording. In conclusion, disappearance of severe symptoms observed after pacemaker implant in cardioinhibitory carotid sinus syndrome seems to depend from pacing therapy, in most cases, yet from the benign natural course of the disease in some other cases.
Transesophageal Programmed Atrial Pacing as a Method of Selecting Patients with Sick Sinus Syndrome for Permanent Atrial Pacing
Authors: ŚWIĄTECKA GRAŻYNA , LUBIŃSKI ANDRZEJ , RACZAK GRZEGORZ , STANKE ANDRZEJ , JUZWA ALICJA , KUBICA JACEK
Published: July 2006

Many recent studies have shown transesophageal programmed atrial pacing (TP) as a very practical, safe and convenient way for assessment of sinus node function and AV conduction. On the other hand, permanent atrial pacing is known to be superior to ventricular pacing due to arrhythmogenic and hemodynamic reasons. This is the reason why we decided to use TP as a method of choosing patients with sick sinus syndrome (SSS) for permanent atrial pacing. Sixty‐three patients with symptomatic (58) and asymptomatic (5) SSS in a variety of clinical situations were examined in this way. The following electrophysiological features were examined: sinus cycle length, sinus node recovery time as well as corrected time, secondary pause after overdrive stimulation, sinoatrial conduction time, Wenckebach point, induction of supraventricular arrhythmias by S1, S2, S3 programmed stimulation and burst pacing. Patients with abnormal parameters were examined once more after intravenous atropine 0.2 mg/kg to evaluate parasympathetic component. Standard 12‐lead ECG was performed in ail, and Holter monitoring in most of patients.

Twenty‐six patients were candidates for permanent AAI pacing. Failures occurred in eight patients usually due to low P wave amplitude and electrode instability. Eighteen patients received AAI pacing systems: eight with brady‐tachycardia syndrome, nine with brady‐arrhythmia and one with sinoatrial block. In the follow‐up of 5–28 months in one patient occurred high degree AV block (11°) during digitalis therapy. Reduction of doses made this block disappear. Examination of Wenckebach point and possibility of inducation of supraventricular lachyarrhythmias in cases of atrial overexcitability are particularly useful in selecting patients for AAI pacing. (PACE, Vol 11 November Part II 1988)
Noninvasive Diagnosis and Treatment of Atrial Flutter Utilizing Previously Implanted Dual Chamber Pacemaker
Authors: HASSETT JAMES A. , ELROD PAMELA A. , ARCINIEGAS JOAQUIN G. , MACLEAN WILLIAM A.H. , DUNCAN JAMES L.
Published: July 2006

Patients with previously implanted dual chamber pacemakers (PM) may develop atrial flutter (AFL). The Siemens‐Pacesetter AFP and Genesis PM have the capability of noninvasively synchronizing to a standard external electrophysiology (EP) stimulator. Any arrhythmia termination or induction protocol may be used with a refractory period limitation of approximately 127 msec (472 ppm). The PM stimulation sequence is directly controlled by the APS Model 370EP Programmer which acts as an interface between the PM and EP stimulator. All testing is conducted with the PM functioning in a single chamber mode. The external EP stimulation is detected by the programmer and a 37 KHz coded radio frequency transmission is used to control the PM stimulation in a 1:1 fashion. Real‐time intracardiac electrograms (IEG) can be recorded from either the atrial (A) or ventricular lead. The IEG can be used for: (1) hard‐copy for diagnosis and cycle length determination; (2) monitoring during and after the procedure; and (3) a synchronization signal to the EP stimulator. Two patients presented with three episodes of AFL with A rates ranging from 220–290 bpm. An A‐IEG was obtained in each case to document the exact rhythm and rate. Rapid A pacing from 300–340 ppm was accomplished using a standard external rapid A pacemaker in concert with the 370EP programmer and PM. In two episodes, the AFL accelerated to transient A fibrillation followed by spontaneous conversion to sinus rhythm (SR). In the other episode, the AFL converted directly to SR. We conclude that: (I) AFL can be easily terminated noninvasively utilizing this system; (2) IEG telemetry (particularly of A activity) via PM is valuable in the diagnosis of rhythm disturbances; and (3) this system allows the utilization of standard stimulation protocols to assess AV conduction and interrupt tachyarrhythmias.
Noninvasive Measurement of Retrograde Conduction Times in Pacemaker Patients
Authors: MARCO DAVID D. , GALLAGHER DIANE
Published: July 2006

Retrograde, or ventriculoatrial conduction (VAC) has been measured in 67% of pacemaker patients with SSS and 25% of patients with 3° block.1 DDD pacers use the postventricular atrial refractory period [PVAHP] to prevent sensing VAC. If the PVARP is too short, a pacer‐mediated tachycardia (PMT) could occur. If too long, rapid atrial rates may not be sensed. To accurately set the PVARP, VAC must be measured. Five noninvasive methods are described: (1) Surface ECG during WI pacing; (2) Atrial intracardiac electrograms during WI pacing; (3) Initiating a PMT with long pacemaker AV interval; (4) Initiating a PMT at the maximum tracking rate; (5) DDI mode with electronic calipers. The description of these methods is intended to enable a physician to detect and measure VAC in patients with any manufacturer's DDD or VDD pacemaker.
Prevention and Termination of Pacemaker‐ Mediated Tachycardia in a New DDD Pacing System (Siemens‐Pacesetter Model 2010T)
Authors: DUNCAN JAMES L. , CLARK MARTHA F.
Published: July 2006

The clinical incidence of Pacemaker‐Mediated Tachycardia (PMT) has been substantially reduced with the availability of wide range postventricular atrial refractory period (PVARP) programmability in most current technology DDD pacemakers. However, patients may still he at clinical risk for PMT if the PVARP must be reduced to allow higher atrial tracking capability or VA conduction (VAC) is not periodically assessed to ensure adequate PVARP selection. A new DDD pacer (Siemens‐Pacesetter Model 2010T) incorporates programmable responses to a sensed PVC to prevent PMT induction due to VAC following a PVC. In each of these responses, the PVAHP is automatically extended to prevent detection of the retrograde P wave, thus preventing the PMT. Additionally, should a PMT occur for reasons other than a PVC, the selected PVARP extension algorithm is periodically invoked to terminate the PMT. This study was conducted to evaluate the operation and clinical benefit of these PVC response functions and PMT termination capabilities. The exact timing operation of the pacer during these responses is also reviewed.
Automatic Refractory Period
Authors: BEGEMANN MALCOLM J.S. , BOUTE WIM
Published: July 2006

Pacemakers have become more and more complex over the years, whereby technological advances were used to create more and new possibilities in existing pacemaker applications. As a result a demand has grown for more automatic functions to reduce the time to program the pacemakers and eleviate follow‐up procedures. One of the parameters which can he adjusted automatically is the refractory period. We measured the pacing threshold as a function of coupling interval between the stimulus and the previous paced complex and related this to the morphology of the paced evoked T‐wave. When the stimulus fails far away from the T‐wave the pacing threshold is constant. When it approaches the T‐wave the threshold reduces slightly (superconductivity) and at the peak of the T‐wave there is a sharp increase of the pacing threshold. The refractory period coincides with the period from the stimulus until the top of the T‐wave (stim‐T interval). This result is used in the Rhythmyx pacemaker where the stim‐T interval is used to automatically adjust the pace refractory period. Automatically adjusting the refractory period has the extra advantage of higher allowable pacing rates as the refractory period shortens with increasing heart rates. Future applications will include use antitachycardia pacing where the stim‐T interval can be used to prevent pacing in the refractory period or in the vulnerable zone.
Morphology of Endocardial T‐Waves of Fusion Beats
Authors: BOUTE W. , CALS G.L.M. , DEN HEIJER P. , WITTKAMPF F.H.M.
Published: July 2006

Recently developed stimulation techniques are capable of eliminating polarization afterpotentials caused by the emitted stimulus. A well‐controlled study method was developed to initiate various degrees of fusion and to monitor changes in the morphology of the endocardial signal. The study was performed on two dogs. The zone during which fusion could be provoked was less than 30 ms in both dogs. In addition, the results show a significant decrease in the endocardial T‐wave amplitude as soon as fusion was noticed, while the QT interval then slightly lengthened. Furthermore, the evoked R‐wave duration shortened during fusion, while the stimulus to R‐wave interval lengthened. These results have consequences for pacemakers that use evoked endocardial signal characteristics for driving a pacemaker function.
The Combined Use of Hysteresis and Holter Functions Improves Diagnosis and Therapy in Patients with Sick Sinus Syndrome
Authors: STANGL K. , WIRTZFELD A. , SICHART U. , SEIDL K.F. , BLÖMER H.
Published: July 2006

We used the Holter functions of an implantable pacemaker in 12 patients with sino‐atrial disease suffering from Adam‐Stokes attacks to analyze the effects of hysteresis programming. The basic pacing rate of 50 ppm combined with a programmed hysteresis value of 10 to 20 ppm led to a drastic reduction in competition between paced and spontaneous beats: the percentage of paced beats decreased from 20.1% without hysteresis to 1.4% using 10 ppm hysteresis and the switches from sense to pace decreased from 2.0% to 0.06%. On the other hand, with hysteresis, no decrease in either the exercise tolerance or general well‐being of the patients was observed.
Association Between Stimulated QT Interval and Ventricular Rhythm Disturbances: Influence of Autonomic Nervous System
Authors: KOCOVIC DUSAN , VEUMIROVIC DUSAN , DJORDJEVIC MILAN , PAVLOVIC SINISA , SAVIC DRAGUTIN , STOJANOV PETAR
Published: July 2006

To examine the association between ventricular rhythm disturbances and changes in the pacemaker‐induced stimulated T interval (STIM‐T interval), we compared findings from monitoring of two patient groups. The first group consisted of 15 patients with QTX microprocessor pacemakers and the second group consisted of 198 patients with documented ventricular rhythm disturbances and coronary artery disease (CAD). In the first group, which was free of ventricular rhythm disturbances and manifest coronary artery disease, the STIM‐T interval was measured every 4 hours over a 36‐hour period at four pacemaker frequency settings (70, 80, 90, and 100) in order to observe the circadian variation of the STIM‐T interval as a function of changes in autonomic nervous system (ANS) tone. The second group was comprised of patients with CAD and over 30 VES/hrs (Lown grade classification 1–5), and taking no antiarrhythmic medication. These patients were followed using 24‐hour Holter monitoring over a minimum of 23 hours and with less than 5% artifact/recording. Information regarding mean hourly heart rate, total number of VES, VES pairs, VT runs, and ischemic episodes in this group was compared with changes in the STIM‐T interval in the first group. The STIM‐T interval was found to be shorter during the day and longer at night at all heart rate settings. The total frequency of VES, of VES pairs, VT runs, and ischemic episodes in the second group varies in a similar circadian fashion. The greatest total number of VES, of VES pairs, VT runs, and ischemic episodes was recorded in the waking hours, at the same time when the STIM‐T interval is the shortest, while this number was significantly lower during sleep, when the STIM‐T interval of the first group is the longest. This coincidence of circadian variation pattern between STIM‐T interval in group I, and ventricular arrhythmias and ischemic episodes in group II, suggests that alterations in ANS tone reflected in the STIM‐T interval may be an important factor in the occurrence of these untoward events.
Differentiation of Arrhythmias in the Dog by Measurement of Activation Sequence Using an Atrial and Two Ventricular Electrodes
Authors: WALSH CHRISTINE A. , SINGER LEWIS P. , MERCANDO ANTHONY D. , FURMAN SEYMOUR
Published: July 2006

Timing of atrioventricular activation and ventricular dispersion identifies and discriminates between beats of different origin. In eight dogs, three bipolar epicardial electrodes recorded left atrial and left and right ventricular depolarizations simultaneously during arrhythmias induced by programmed electrical stimulation and coronary artery occlusion and release. The interval between the left atrial and left ventricular intrinsic deflections (V1‐V2) and between the left ventricular and right ventricular intrinsic deflections (V1‐V2) of each heat was measured. Recordings were of normal sinus rhythm (NSR) (mean of five beats in 8/8 dogs), atrial flutter (AFL) (five beats of one episode), atrial fibrillation (AF) (144 beats in 29 episodes in 7/8), monomorphic ventricular tachycardia (MVT) (24 beats with six morphologies in 2/8), polymorphic ventricular tachycardia (PVT) (63 beats in 15 episodes in 5/8) and premature ventricular contractions (PVC) (29 beats with 29 morphologies in 5/8). Supraventricular rhythms can be differentiated from ventricular rhythms by V1‐V2 timing. The mean difference in V1‐V2 during AFL and AF vs NSR was 1 ms (range of 0–3 ms). The change from sinus during MVT ranged from 38 to 43 ms (m 31 ms) and during PVC 10 to 75 ms (m 38 ms). Thirty‐five of 35 of these ectopic ventricular morphologies exhibited 10 ms or more timing difference compared to corresponding beats of NSR. PVT was consistently distinguished from supraventricular rhythms and MVT by the variability of V1‐V2,A‐V1 intervals can be used to distinguish supraventricular arrhythmias from sinus rhythm; a 32 ms difference existed for AFL. AF could be detected by the variability in AV1. One atrial and two ventricular leads can provide a means of differentiating normal sinus rhythm from supraventricular and ventricular arrhythmias that may be applicable to implantable antitachycardia devices.
Clinical Experience with New Leads
Authors: MUGICA J. , DUCONGE B. , HENRY L. , ATCHIA B. , LAZARUS B.
Published: July 2006

Recent developments in cardiac pacemaker electrodes have resulted in significant benefits to the group of pacemaker patients as a whole. The results of analysis of 2,818 chronic pacemaker electrodes are presented. These electrodes are divided into major categories according to their particularities: platinum iridium, elgiloy, carbon‐tip, anodized platinum and granulated iridium‐platinum. All leads were in the ventricular position. The results of acute and chronic threshold measurements reveal that carbon‐tipped electrodes appear to have the most favorable overall characteristics. This will have a major influence on long‐term pacing practices.
Studies of the Tissue Reaction Induced by Transvenous Pacemaker Electrodes. I. Microscopic Examination of the Extent of Connective Tissue Around the Electrode Tip in the Human Right Ventricle
Authors: BEYERSDORF FRIEDHELM , SCHNEIDER MARKWARDT , KREUZER JOACHIM , FALK STEFAN , ZEGELMAN MAX , SATTER PETER
Published: July 2006

The purpose of this study was to investigate the extent of connective tissue of the human right ventricle induced by cardiac pacing electrodes. Between January 1984 and July 1987, 34 consecutive patients with VVI‐pacing systems were autopsied in the Department of Pathology at the University of Frankfurt/M. The surrounding tissue of these 34 electrodes (17 Siemens Elema 412 S, five Medtronic 6957, one Medtronic 6959, one Medtronic 4011, three Biotronik D2K, three Biotronik K10, two Osypka FY 62, one Biotronik N, and one Siemens Elema 588) in the right ventricle were investigated histologically. The tissue was stained with Giemsa and the thickness of the connective tissue layer was measured. Stimulation threshold data at various times were known in four of eight screw‐in electrodes, in seven of 17 vitreous carbon electrodes and in two of seven smooth surface electrodes. Electrode surface area, implantation time, age of the patient and cause of death were comparable for all three electrode groups. However, a significant difference was found in the extent of connective tissue between the porous surface and screw‐in electrodes (128 ± 55 VS 397 ± 269 μm, P 0.01) and porous surface and smooth surface electrodes (128 ± 55 vs 307 ± 117 μm, P 0.01). No relation (r = 0.106) was found between the duration of implantation and the extent of connective tissue for the vitreous carbon electrodes (Siemens Elema 412 S). The lowest chronic stimulation thresholds were measured in the latter type of electrodes (0.5 ± 0.3 V) as compared to the screw‐in (0.75 ± 0.30 V) and smooth surface electrodes. We conclude from this study, that vitreous carbon electrodes induce only a small amount of connective tissue around the insertion site in the human right ventricle, as compared to other smooth surface or screw‐in electrodes. Chronic stimulation threshold data parallel those morphological results.
Composite Electrode Tips Containing Externally Placed Drug Releasing Collars
Authors: BREWER GREGORY , MATHIVANAR RANJINI , SKALSKY MICHAEL , ANDERSON NEIL
Published: July 2006

We have developed a composite electode tip based on a new concept whereby the electrode is combined with a polymeric collar containing dexamethasone sodium phosphate (DSP). The collar is positioned immediately adjacent to the electrode. Initial evaluation of this concept employed the Telectronics Laserpor electrode and a collar containing approximately 1.8 mg of DSP (LPD). Conventional Telectronics Laserpor (LP) electrodes were used as controls. Further evaluation was performed using a DSP (< 0.5mg) eluting collar and a new 4 mm2 mushroom shaped electrode with a high microsurface Pt/Ir coating (MD). Data for conventional Telectronics Laserdish (LD) electrodes were used for comparison. Unipolar ventricular leads were implanted transvenously in the right ventricular apex of sheep. Voltage thresholds, pacing (5V, 0.5ms) and sensing (50/100 mVRMS, 50 Hz) impedances were measured during the subchronic phase (< 6 weeks) and in the case of LD and MD for 6 months. The steroid eluting electrodes were elective in eliminating (2 weeks vs. Impl., N.S.) the 2 week threshold peaking seen with the control leads (2 weeks vs. Impl., P < 0.005). The small area MD electrode thresholds remained stable and low for up to 6 months (0.38 ± 0.09 (10) c.f. 0.46 ± 0.11(6); 14 and 180 days, respectively, N.S.). The composite electrode tips with steroid releasing collars thus show great potential for a substantial reduction in stimulation energy.
Atrial Capture Detection with Endocardial Electrodes
Authors: LIVINGSTON A.R. , CALLAGHAN F.J. , BYRD C.L. , HEEMELS J.P. , HOLLANDER P. , VAN MEGHELEN R. , GHAPPIN J.J.M.L.
Published: July 2006

A new method of evoked response detection, previously demonstrated in the ventricle, has been studied in the atrium at the time of routine pacemaker implant in 16 patients. The atrial evoked response was readily detectable in all patients due to excellent recovery from poststimulus polarization. In six patients, as experimental threshold‐ tracking pacemaker was used to automatically verify atrial capture and to generate strength‐duration curves. It is concluded that this pacing technique is both simple and reliable, and that automatic atrial threshold tracking is feasible.
Reliability of Atrial Screw‐in Leads
Authors: MARKEWITZ ANDREAS , WENKE KLAUS , WEINHOLD CHRISTIAN
Published: July 2006

The aim of this study was to investigate long‐term performance of a carbon coated atrial screw‐in lead. During implantation of 247 leads of this type we measured an average stimulation threshold of 0.74 V(range: 0.2–1.6 V) at 1 ms pulse width. Mean lead impedance came to 446 ohms (range: 263–1000 ohms) resulting in an arithmetical energy consumption of 1.51 μJ(range: 0.1–7.21 μJ). Average P wave amplitude was 3.9 mV (range: 1.3–11 mV). After a mean follow‐up of 16.4 months (range; 3–60 months) we found excellent threshold results in 76% of the patients permitting a safety programming al half of nominal value. An additional 14% nominal settings could be retained. With regard to chronic lead impedance of 488 ohms (range: 315–1327 ohms) we calculated an average chronic energy consumption of 10.83 μJ (range: 1.62–22.78 μJ) during safety programming. This made up 34.6% of the corresponding energy consumption during nominal programming. Eighty percent of the patients showed chronic P waves above 2 mV; nearly half of them (n ‐ 94 = 38%) showed a proper sensing function even when programmed to minimal sensitivity settings or above 4 mV. In 19 leads (8%) we observed unsatisfying threshold results requiring high output programmings. All threshold increases occurred within the first year, 84% (n = 16/19) within the first 3 postoperative months. An additional five leads (2%) were found to have a loss of capture, and one (0.5%) a loss of sensing. These complications required reoperation as well as one dislocation (0.5%) resulting in a low complication rate of 3% as compared to the total complication rate of all implanted atrial leads which was substantially higher (n = 48/652 = 7.5%). With regard to our results we consider the carbon coated atrial screw‐in lead to have proven long‐term reliability.
Design and Evaluation of a Low Threshold, Porous Tip Lead with a Mannitol Coated Screw‐In Tip (“Sweet Tip”™)
Authors: ORMEROD D. , WALGREN S. , BERGLUND J. , HEIL R.
Published: July 2006

A screw‐in transvenous lead has been developed for permanent atrial or ventricular pacing that makes insertion of a fixed helix lead smoother and less complicated. The helix has a mannitol coating that protects the helix during insertion and dissolves in the blood stream allowing the fixation of the helix by screwing it into the endocardium. The Sweet Tip™ lead features a porous tip mesh electrode designed to improve pacing and sensing thresholds, and HP silicone insulation of previously demonstrated reliability.
In Vitro Estimation of the Electrical Performance of Bipolar Pacing Electrode Systems
Authors: WALTON CHRISTOPHER , ECONOMIDES APOLLO P.
Published: July 2006

With the current interest in bipolar stimulation, there is a need for greater understanding of the electrical contributions of the two electrodes in this type of pacing. This has been investigated using a specially designed cell in which an electrode under test was immersed in a buffered saline solution (pH 7.42) at 37–38°C. Four electrode types were studied: a single stimulating electrode (6 mm2 dish tip, Pt‐black coated) and three indifferent electrodes. The indifferent electrodes were a 41 mm2 polished Pt ring, a Pt‐black coated version of the same electrode, and a titanium pacemaker enclosure which was included to allow comparison with the unipolar situation. These electrodes were tested individually against a chlorided silver reference electrode of negligible (1–2Ω) impedance, the results being processed in such a way as to allow estimation of the properties of the stimulating electrode taken in combination with each of the indifferents. Constant current pulses (1–10 mA amplitude, 0.5 and 1.0 ms duration) were applied and measurements made from the resulting voltage waveforms. These were V1 and V2, the potential at the leading and trailing edge of the pulse, and Va, the post‐pulse potential at 20 ms following the trailing edge. The potential V1 ‐ V2 is electrode dependent and allows the determination of the energy loss due to polarization to be calculated. Sinusoidal AC signals (0.1 Hz‐10 kHz, 20 μA maximum amplitude) were also employed, allowing determination of sensing impedance. Under all conditions, the calculated performance of the stimulating electrode with the coated ring was nearly equivalent to that with the pacemaker enclosure. The performance with the uncoated ring was in all respects markedly inferior, displaying almost double the energy loss on pulsing, post‐stimulus potentials an order of magnitude larger and sensing impedance increased by a factor of up to 8.
Introduction of an Automatic QT Interval Driven Rate Responsive Pacemaker
Authors: BOUTE W. , GEBHARDT U. , BEGEMANN M.J.S.
Published: July 2006

QT driven rate responsive pacemakers have been implanted since 1981. The more than 6 years experience and additional knowledge gained during several clinical studies have culminated in the design of an automatic rate responsive pacemaker. The adjustment of the rate responsive function to each individual patient is carried out automatically by the pacemaker, which therefore performs several measurements both at rest and during exercise. The results of these measurements are used to adapt the rate responsive parameters in order to optimize the rate response, even under changing circumstances.
A New Principle of Rate Adaptive Pacing in Patients with Sick Sinus Syndrome
Authors: IRNICH W. , CONRADY JÜRGEN
Published: July 2006

The most “natural” rate adaptive pacemaker is VDD for patients with AV block. Nothing equivalent exists for patients with sick sinus syndrome (SSS). Even if they are paced in the AAI mode, the AV synchrony is often lost under exercise if nodal rhythms develop which cause the atria to contract against closed valves by retrograde conduction. We tried to develop a concept of rate adaptive pacing which is applicable in SSS patients by guaranteeing AV synchrony. It is known that AV delay shortens with increasing rate under exercise in normal subjects. Three AAI paced patients were evaluated to find out whether a similar correlation is valid between exercise and AV delay with constant rate. A nonconventional ECG was registered during the whole procedure by using an analog tape recorder. The pacing rate was changed with and without exercise on a bicycle to determine its influence on AV delay and by calculating the AV delay averaged over the last 8 beats. In all three patients a reproducible correlation existed between exercise and shortening of the AV delay. This effect was already detectable after 10 s. Increasing the pacing rate above “physiological” rates caused prolongation of the AV delay (over‐stimulation phenomenon). We, therefore, concluded that measuring the AV delay in atrial paced patients with SSS by means of a ventricular electrode can be used as a fast parameter for rate adaptive pacing with AV synchrony. The “over‐stimulation” phenomenon can additionally be utilized for controlling “physiological” rates depending on individual needs.
Which Patient is Most Likely to Benefit from a Rate Responsive Pacemaker?
Authors: HEINZ M. , WÖRL H.H. , ALT E. , THERES H. , BLÖMER H.
Published: July 2006

In order to provide information about indications for rate responsive pacing, we examined the exercise capacity of a typical collective of pacemaker patients. One hundred seven patients participated in the study, 50/107 (46.8%) suffered from sick sinus syndrome, 37/107 (34.6%) showed complete AV block, 12/107 (11.2%) had bradyarrhythmia and 8/107 (7.4%) had other diseases. Ali patients underwent treadmill exercise with increasing workloads up to the individual's maximum workload. We monitored heart rate, respiratory rate, workload, the subjective perception of stress according to the Borg scale, and the reason for the termination of exercise. Calculation of oxygen uptake was done according to an equation given by Givoni. During the tests, all implanted pacemakers have been programmed to VVI 70 mode. We found that all pacemaker patients showed a reduction of their exercise capacity compared to the age‐related normal values. Particularly in patients with AV block or bradyarrhythmia, the maximum achievable workload often did not even reach levels of everyday activities such as going upstairs; patients with sick sinus syndrome showed slightly better exercise capability, probably due to the higher increase of average heart rate. Despite objective differences of maximum workload, all patients had the same subjective perception at the end of the tests; the course of respiratory rate indicated that ail persons finished the tests in the range of individual maximum exercise capacity. We assume that patients who had to terminate exercise because of stenocardia. claudication, or joint pain even in the VVI 70 mode will not benefit much from rate adaptation. The effect of rate increase upon occurrence of dizziness is difficult to validate. Those who terminated the tests because of dyspnea, exhaustion, or muscular fatigue probably will benefit from rate adaptation during physical work. This group of patients represented 69% of ail examined patients; by excluding patients with AV block (who can be treated optimally by DDD pacemakers), about 46% of all pacemaker patients might benefit from rate responsive pacing.
Physiological Benefits of a Pacemaker with Dual Chamber Pacing at Low Heart Rates and Single Chamber Rate Responsive Pacing During Exercise
Authors: FRENCH WILLIAM J. , HASKELL RICHARD J. , WESLEY GEORGE W. , FLORIO JOSEPH
Published: July 2006

Dual chamber rate responsive pacing may be an ideal mode but may result in high current drain and premature battery depletion. To minimize battery drain during exercise, this study compared a combination pacing mode of IDDD and ventricular rate responsive pacing (WIR). Nine patients were studied who had complete heart block, sinus rhythm, DDD pacemakers, and a reduced mean left ventricular ejection fraction of 44%. Patients were exercised in DDD, WIR, and a combination of DDD at low heart rates and WIR at mean heart rates over 89 bpm. Blood pressure, heart rate, exercise duration, work rate, oxygen uptake, anaerobic threshold, and oxygen pulse were measured. There was no difference in symptoms or in mean cardiopulmonary function indices including exercise duration 10.7. 10.3. 10.3 minutes; heart rate 127. 133. 136 bpm; oxygen uptake 1.4. 1.5. 1.5 L/minute; or anaerobic threshold 5.6, 5.5, 5.7 minutes (p > 0.05) in any mode. A pacemaker that provides atrioventricular synchrony at low heart rates with ventricular rate responsiveness at high heart rates may be an alternative mode for some patients.
Heart Rate Correlation, Response Time and Effect of Previous Exercise Using an Advanced Pacing Rate Algorithm for Temperature‐Based Rate Modulation
Authors: FEARNOT NEAL E. , LEE EVANS MERRY
Published: July 2006

A temperature‐based algorithm to produce pacing rate that resembles chronotropic response to activity was developed. Measurement criteria for the algorithm included workload dependent rate increases with activity and response time within 60 seconds of exercise onset. To evaluate the aigorithm, right ventricular blood temperature was recorded during rest and treadmill exercise in 25 patients with implanted Kelvin 500 pacemakers (Cook Pacemaker). Patients included 16 maies and nine femaies, ages 44–81 (mean 72). Indications for pacing were sinus node disease, atrioventricular block and atrial fibrillation with siow ventricular response. Temperature changes reflected physical activity as well as emotional stress. The algorithm was based on the rate of change (dT/dt), the relative change (AT) and the baseline history (T) of temperature. At exercise onset, a rapid, brie/drop in temperature (dT/dt) typically occurred due to peripheral vasodilation, causing prompt increase in pacing rate. As exercise continued, the increase in metabolic rate caused dT/dt as well as AT to increase, further increasing pacing rate. After exercise, temperature returned to resting level which correspondingly decreased the pacing rate. Sensitivity of the algorithm to temperature variations, and the upper and lower pacing rate limits were programmable to adapt to individual patient needs. The rates produced by the algorithm mimicked intrinsic rate response for various activity levels and produced a mean response time of 16 seconds from exercise onset. Previous exercise had no significant effect on response time. Correlation between normal chronotropic response and simulated pacing rate from five exercise tests was 0.92. These results show good specificity and refute the statement that blood temperoture yields a slow response.
Relationship Between Heart Rate and Minute Ventilation, Tidal Volume and Respiratory Rate During Brief and Low Level Exercise
Authors: VAI F. , BONNET J.L. , RITTER PH. , PIOGER G.
Published: July 2006

The correlation between heart rate (HR) and three respiratory parameters, minute ventilation (VE), tidal volume (Vt), and respiratory rate (RR), were studied. Four healthy subjects performed four exercise tests duration 30 seconds at 50, 100, 150, or 200 W), in random order. Cardio‐respiratory parameters were recorded respiratory cycle by respiratory cycle. The results of these low level exercise tests showed that oxygen consumption (VO2) was strongly correlated with VE (r = 0.91 ± 0.10; P < 0.01) (except in one test) and Vt (r =0.91 ± 0.07; P < 0.001) (except in one test). There was no significant correlation between VO2 and RR. At exercise onset HR, VE, and Vt were modified in a matter of a few heart beats while RR varied depending on the subject and the level of exercise. During exercise average HR, VE, and Vt were significantly higher than at rest in most cases; but RR was not significantly changed by exercise. The correlations between HR and VE, Vt and RR varied from one individual to another. Nevertheless, the correlation coefficients were positive for VE and Vt, while they were negative for RR. Sensing respiratory rate thus appears to be insufficient for responsive pacing of exercise onset, but sensing respiratory volumes (Vt, VE) should give satisfactory results.
Rate Responsive Pacing Using a Minute Ventilation Sensor
Authors: MOND HARRY , STRATHMORE NEIL , KERTES PAUL , HUNT DAVID , BAKER GEOFFREY
Published: July 2006

Minute ventilation, the product of respiratory rate and tidal volume, correlates directly with oxygen consumption, cardiac output, and heart rate. An implantable pacemaker has been developed which allows variation in pacing rate in response to measured changes in minute ventilation. This single chamber system measures transthoracic impedance between the tip electrode of a standard bipolar lead and the pulse generator case. Low amplitude current pulses (1 mA for 15 μsec) are generated each 50 msec between the ring electrode and the case. In the adaptive mode, the pulse generator calculates a rate response factor or slope after maximal exercise. This slope, which describes the relationship between pacing rate and minute ventilation together with the pacing rate limits are the only programmable rate responsive features. Minute ventilation rate responsive systems have been implanted in 12 patients (8/emales, 4 males), of mean age 63 years. Indications were His bundle ablation (6), acquired complete heart block (4), and sick sinus syndrome (2). At post‐implant exercise testing, pacing rate rose within the first minute. Peak rate and time to upper rate were dependent on workload. After exercise, pacing rate remained at peak for up to 2 minutes before a gradual fall to resting rate. Comparative studies of the minute ventilation and the activity sensor pacing systems in the same patients confirmed that the minute ventilation system more closely parallels normal sinus response to activity. The minute ventilation rate responsive pacing system is simple to programme, no special lead is required and the system is highly physiologic.
A New Mechanical Sensor for Detecting Body Activity and Posture, Suitable for Rate Responsive Pacing
Authors: ALT ECKHARD , MATULA MARKUS , THILO RUDOLF , THERES HEINZ , HEINZ MICHAEL , BLÖMER HANS
Published: July 2006

In the past, thought about rate responsive pacing mainly focused on rate increase with exercise but did not consider that a rate increase with postural changes also is mandatory in order to prevent orthostatic reactions. A nightly decrease in pacemaker rate when the body is at rest and in a supine position is a further advantage for the patient's sleep and recovery. Therefore, we developed a sensor that could detect not only rest and body activity but also discriminate between a supine and an upright position. This sensor is a muiticontact tilt switch containing a small mercury ball, as shown in the left panel of the figure below. The principle of discrimination between rest and low and high body activity is realized by the movement of the mercury ball resulting from body motion, which causes openings and closures within the sensor as the ball touches the numerous sensor contacts. In the upright position, a distinct number of contacts at the bottom of the tilt switch are closed. In the supine position, there is no closure of the bottom contacts and a postural discrimination can he achieved. We studied 12 volunteers and 10 pacemaker patients with this new device both at rest and during physical exercise. The right panel of the figure illustrates that the contacts per second correlate to the increase of physical exercise, such as walking on the treadmill. Further studies with an external pacemaker containing a small sensor suitable to fit into the pacemaker are in preparation.
First Clinical Experience with an Oxygen Saturation Controlled Pacemaker in Man
Authors: STANGL K. , WIRTZFELD A. , HEINZE R. , LAULE M.
Published: July 2006

This article describes the characteristics of a new implantable pacemaker controlled by right atrial oxygen saturation and reports the first clinical experience in man. During the observation period over 5 months, there was no evidence of malfunction due to tissue growth. The system's reaction to exercise changes proved to be quick (5 s to 17 s); decay times varied depending on the magnitude of the power previously performed. Under various exercise tests, the rate increase was linear to the stress load. Measurements of cardiac output showed the system's hemodynamic feedback and its potential self‐optimization of pacing rate.
Rate Response During Submaximal Exercise: Comparison of Three Different Sensors
Authors: ZEGELMAN MAX , CIESLINSKI GERD , KREUZER JOACHIM
Published: July 2006

Since 1983, 248 rate responsive pacemakers were implanted at our hospital. The main emphasis during clinical follow‐up has to be placed on (he adjustment and control of its rate adaption, to meet the requirements of the aged patient's daily life. Repeated submaximal exercise but not extreme strain, come to the fore. Kaltenbach's step test (individually by stencils defined normal ranges of the heart rate during a 6 minute submaximal exercise and a 6 minute recovery period; age and sex dependent work load relative to body surface area) is able to mimic everyday efforts in an easy and reliable way. Nineteen patients with QT‐related pacemaker, 12 patients with respiratory dependent pacemaker and 45 patients with body activity directed pm Activitrax were exercised using Kaltenbach's step test (mean wattage QT: 56 ± 14, HDP: 75 ± 29, Activitrax: 64 ± 20). Fifty‐two patients performed 3 rounds. In comparison, 42 patients with DDD‐pm underwent the same test (75 ± 28 Watt). The average curve [heart rate] with QT‐pm settled in the normal range of the step test but was distorted. Only 42% of the patients reached normal range in ail three rounds. The mean heart rate of the RDP‐group bordered on the basis of the normal range. The average curve (heart rate) of patients with Activitvax or DDD settled exactly in the desirable range. Problems with the rate response under repeated exercise did not occur either in the RDP or in the DDD group. The rate response behavior of the QT‐related pm, the RDP and the Activitrax was of different quality. The Activitrax, with all its limitations as a device witb a non physioiogical sensor, came off very well; even though modifications of the programmable gradings of the rate response (thresholds) should be considered. Kaltenbach's step test is an excellent method to adjust and control rate responsive pacemaker.
Pacemaker‐Mediated Tachycardia: Engineering Solutions
Authors: CALFEE RICHARD V.
Published: July 2006

This discussion summarizes the interaction of refractory periods and upper rate behaviors in modern dual‐chamber demand (DDD) devices, the data regarding and nine events initiating VA conduction and engineering solutions proposed and/or implemented to address the problem of pacemaker‐mediated tachycardia (PMT). Among the causes of PMT are premature atrial depolarization, loss of atrial capture, a return to the demand mode after asynchronous magnet mode pacing, programming from a mode that does not guarantee AV synchrony to a mode in which atrial tracking can occur, noise, certain situations involving Wenckebach behavior, loss of sensing, and the inability of a rate‐smoothing algorithm to allow a rapid change in ventricular rate. Engineering solutions to prevent the occurrence of PMT include a programmable postventricular atrial refractory period (PVARP), differential AV delay, adaptive AV delay, and the ability to discriminate between P waves of atrial origin and those resulting from retrograde conduction from the ventricle. Features such as the ability to lengthen the PVARP for one cycle after exiting the magnet or noise reversion modes or programming to a new mode, lengthen the PVARP for a single cycle following a PVC or revert to DVI pacing for one cycle following a PVC have been developed to recognize initiating events. A third solution. a tachycardia termination algorithm, can recognize and terminate PMT; varying the AV delay to determine whether P waves move in a corresponding manner and using a metabolic sensor to confirm the need for a fast heart rate are other possibilities in the detection of PMT. Diagnostic data features may also be used to evaluate the appropriateness of programmed settings. This discussion concludes that PMT is no longer a significant clinical entity when more advanced DDD pacemakers are utilized.
Long‐Term Follow‐Up of Patients Treated with VVI Pacing and Sequential Pacing with Special Reference to VA Retrograde Conduction
Authors: EBAGOSTI A. , GUEUNOUN M. , SAADJIAN A. , DOLLA E. , GABRIEL M. , LEVY S. , TORRESANI J.
Published: July 2006

The aim of this prospective study is comparing long‐term prognosis in patients implanted with a WI pacemaker (group A) with those implanted with a sequential pacing device, AAI or DDD, (group B). Both groups of 45 patients each, were comparable as regards to age, sex, pacing indications, underlying heart disease, and technical conditions of implantation and were followed‐up over 55 months. Atrial arrhythmias (A.A.) incidence was higher in group A: 24. 4% than group B: 8.8% (P < 0.05). Arterial embolisms (A.E.) occurred in group A patients only. Worsening or occurrence of exercise limitation was more frequent in group A: 35.6% as compared to group B: 13.3% (P < 0.05) and deaths related to these complications, occurred in seven cases in group A versus four cases in group B. In group A, all patients who experienced a worsening or occurrence of an A.A. or an A.E., had a ventriculoatrial condLction (VAC). No statistical difference was observed in worsening or occurrence of exercise limitation between patients with VAC and those without VAC: nine (42.8%) and seven (29.2%) but they respectively experienced at least one complication in 16 cases (76.2%) and seven cases (29.2%) (P < 0.01). In conclusion, Jong‐term prognosis in patients implanted with VVI pacing as compared to patients implanted with sequential pacing is poorer. The presence of VAC in patients treated with permanent WI pacing is a major factor for complications and deaths related to A.E. and cardiac failure. Thus WI pacing should be avoided in patients with VAC.