bluuebunny/crossref_metadata_2025 huggingface dataset:
The Influence of Elevated 50 Hz Electric and Magnetic Fields on Implanted Cardiac Pacemakers: The Role of the Lead Configuration and Programming of the Sensitivity
Authors: TOIVONEN LAURI , VALJUS JORMA , HONGISTO MIKKO , METSO RIITTA
Published: July 2006

The influence of the electromagnetic interference (EMI) on performance of 15 implanted cardiac pacemakers (12 generator models) was tested during exposure at a high voltage substation. All patients had an adequate spontaneous heart rate during the study. Tests were performed in the ventricular inhibited mode with unipolar sensing in all pacemakers and repeated with bipolar sensing in four pacemakers. The sensitivity was set to a regular, functionally proper level and then to the highest available level. Exposure was done to moderate (1.2–1.7 kV/m) and strong (7.0–8.0 kV/m) electric fields, which correspond to the immediate vicinity of 110 and 400 kV power lines, respectively. In moderate electric fields the output was inhibited in one pacemaker at regular sensitivity (1.7–3,0 mV) and in five pacemakers at the highest sensitivity (0.5–1.25 mV). In strong electric fields the output was inhibited in five pacemakers at regular sensitivity and several pacemakers converted to noise reversion mode at the highest sensitivity. In bipolar mode only one of four pacemakers at high sensitivity (0.5–1.0 mV) was inhibited in the strangest electric field, whereas all four did so in the unipolar mode. One pacemaker with unipolar sensitivity at 0.5 mV was interfered by 63 μT magnetic field. The results confirm that the programmed sensitivity level and the lead configuration markedly influence pacemakers' vulnerability to EMI. Bipolar sensing mode is rather safe in the presence of EMI, which is encountered in public environments. The programmable features of today's pacemakers permit individualized, less stringent safety measures to avoid electromagnetic hazards.
Atrioventricular Electrotonic Interaction in Complete Atrioventricular Block: An Experimental Model Using Radiofrequency Energy in the Rabbit Heart
Authors: SANCHIS JUAN , CHORRO FRANCISCO J. , LÓPEZ‐MERINO VICENTE , SUCH LUIS , AVELLANA JUAN A. , MARTÍNEZ‐MAS MARÍA LUZ
Published: July 2006

Provided the conditions for electrotonic transmission exist, an automatic focus surrounded by a block zone may be externally modu‐lated. The atrioventricular (AV) electrotonic interaction was studied in 16 perfused rabbit hearts with supra‐Hisian complete AV block induced using low radiofrequency energy doses (2.5 watts; 10 seconds). In nine experiments the sinus node was preserved (group I), whereas in seven it was removed maintaining an AV nodal rhythm (group II). The V‐V (ventricular cycle length) and V‐A (coupling of the intervening atrial beat) in both groups, and also the A‐A (atrial cycle length) and A‐V (coupling of the intervening ventricular beat) intervals in group II, were measured beat by beat after current delivery. The phase response curves V‐V versus V‐A, and A‐A versus A‐V showed AV interaction in five experiments from group I, and in four from group II, as follows: (1) accelerating phase response curve, characterized by a pacemaker acceleration (V‐V or A‐A abbreviation) at a critical V‐A or A‐V coupling interval; maximum acceleration could be progressively (phase response curve without rapid cross‐over) or briskly (phase response curve with rapid crossover) reached; from this point onwards acceleration decreased with a further increase in V‐A or A‐V coupling interval (acceleration slope). (2) Biphasic phase response curve, characterized by initial delaying and late accelerating phases. Maximum acceleration and the acceleration slope were both smaller in accelerating phase response curves without rapid cross‐over. On reverting complete block in two experiments, a progressive increase in maximum acceleration and acceleration slope was observed. Conclusions: (1) AV interaction in complete AV block can be manifested as accelerating or biphasic phase response curves; (2) transition from electrotonic interaction to conduction seems to be a continuum.
Radiation‐Induced Effects in Multiprogrammable Pacemakers and Implantable Defibrillators
Authors: RODRIGUEZ FABIO , FILIMONOV ALEXANDER , HENNING ALBERT , COUGHLIN CHRISTOPHER , GREENBERG MARK
Published: July 2006

Twenty‐three multiprogrammable pacemakers and four implantable cardioverter defibrillators (ICDs) containing either complementary metal‐oxide semiconductor (CMOS) or CMOS/Bipolar integrated circuit (IC) technology were exposed to 6‐MV photon and 18‐MeV electron radiation at various dose levels. Of the 17 pacemakers exposed to photon radiation eight failed before 50 Gy, whereas four of the six pacemakers exposed to electron radiation failed before 70 Gy. Photon scatter doses were well tolerated. For the ICDs detection and charging time increased with accumulated radiation dose, the charging time increased catastrophically at < 50 total pulses delivered when compared with the charging time of six implanted ICDs. Sensitivity and output energy delivered by the ICD pulse were constant during the test. It was found that devices using the shorter channel length IC technology (i.e., 3 p‐m CMOS) were per se harder to ionizing radiation than the devices using larger channel length IC technologies (i.e., either 8 μm CMOS or combined 5 μM CMOS/20 V Bipolar). In fact, none of the devices based on 3 μm CMOS IC technology failed before 76 Gy, which is above the highest dose level (70 Gy) normally used in radiation oncology treatments.
Influence of Time of Sampling Onset on Parameters Used for Activation Time Determination in Computerized Intraoperative Mapping
Authors: PIEPER CARL F. , BLUE RUSSELL , PACIFICO ANTONIO
Published: July 2006

The purpose of this work is to determine the sensitivity of the estimated time of peaks and maximum slopes, commonly used in activation time computations, to the instant at which sampling is initiated. Based on complex and quickly changing waveforms, 471 monopolar (MP) and bipolar (BP) epicardial responses in man were selected. These were decimated from 10 kHz to simulate sampling at frequencies ranging from 200 Hz to 2,000 Hz. The peak and maximum absolute slope for BP and the minimum slope for MP were computed repeatedly starting at successive 100 μsec intervals extending throughout the sampling period and compared with these parameters computed from the waveform sampled at 10 kHz. Slopes were estimated using each of four different algorithms. The average greatest shift (ACS) due to variations in sampling onset ranged from 11.2 ± 3.5 (200 Hz) to 0.3 ± 0.2 msec (2,000 Hz). For bipolar algorithms, the peak performed better than the slope algorithms (ACS: 5,9 ± 3,3 to 0.3 ± 1.0 msec). For MP algorithms, 2 point linear, and 3 and 5 point Lagrange slope estimates performed similarly (ACS: 5.6 ± 3.3 to 0.3 ± 0.2 msec); a 5 point least square fit algorithm performed poorly. Sampling MP and BP electrograms below 500 and 400, respectively, often caused maximum shifts > 4 msec. Thus, the resolution of the peak and estimated slope is not limited to the sampling period, variations in initiation of sampling can cause significant outliers especially at low sampling rates, and MP electrograms should be sampled faster than BP electrograms for comparable accuracy.
Impedance Monitoring During Radiofrequency Catheter Ablation in Humans
Authors: HARVEY MARK , KIM YOON‐NYUN , SOUSA JOÃO , EL‐ATASSI RAFEL , MORADY FRED , CALKINS HUGH , LANGBERG JONATHAN J.
Published: July 2006

Radiofrequency catheter ablation of accessory pathways and the atrioventricular junction often requires multiple applications of energy. The inability to determine the effects of any given application on the underlying tissue may contribute to this problem. In the present study, impedance was monitored in 20 patients undergoing radio/requency catheter ablation, and the relationship between an initial decrease in impedance and subsequent effects were examined. An initial fall in impedance of more than 10 Ω was 78% sensitive and 88% specific for predicting subsequent evidence of tissue heating (interruption of conduction or an abrupt rise in impedance due to coagulum formation). In contrast, initial values of voltage, current, or impedance did not distinguish between effective and ineffective applications of radiofrequency energy. Continuous monitoring of impedance may facilitate radiofrequency catheter ablation.
The Use of Implantable Sensors for the Control of Pacemaker Mediated Tachycardias: A Comparative Evaluation Between Minute Ventilation Sensing and Acceleration Sensing Dual Chamber Rate Adaptive Pacemakers
Authors: LAU CHU‐PAK , TAI YAU‐TING , FONG PING‐CHING , LI JOHN P‐S , CHUNG FELSA L‐W , SONG STELLA
Published: July 2006

The role of implantable sensors to control pacemaker mediated tachycardias was investigated in 16 patients with two different dual chamber rate adaptive (DDDR) pacemakers, which sensed either minute ventilation (DDDR‐Meta, nine patients) or body acceleration (Relay, seven patients). Successive atrial sensed events beyond a programmable rate occurring in the absence of detection of exercise by the sensors were considered to represent retrograde conduction or atrial arrhythmias, and the pacemakers responded by either a mode shift from DDDR to ventricular rate adaptive (VVIR) pacing (DDDR‐Meta) or by tracking at an interim rate, the so‐called conditional ventricular tracking limit (CVTL, Relay). In the unipolar atrial sensing mode, myopotential sensing (MPI) and external chest wall stimulations (CWS) at 250 beats/min were induced to be preferentially sensed by the atrial channel to simulate the conditions of atrial arrhythmias. In the DDD mode, these maneuvers resulted in ventricular responses of 88 ± 3 faeats/min and 110 ± 3 beats/min for MPI and CWS, respectively. The pacing rate was significantly reduced in the DDDR mode with the sensors correctly detecting and responding to the sensed abnormal atrial signals (68 ± 5 beats/mm during MPI and 71 ± 5 beats/min during CWS, P < 0.005 compared with the corresponding DDD rate). One patient with a Relay pacemaker developed spontaneous atrial flutter and the ventricular tracking responses were 140 and 85 beats/min in the DDD and DDDR pacing modes, respectively. Thus MPI and CWS are useful bedside testing methods to assess pacemaker response during atrial arrhythmias. The use of implantable sensors to judge the appropriateness of atrial rate is a new approach to the management of pacemaker mediated tachycardias.
Simultaneous Unipolar and Bipolar Recording of Cardiac Electrical Activity
Authors: SEVAPTSIDIS ELIAS , MASSÉ STÉPHANE , PARSON IAN D. , DOWNAR EUGENE , KIMBER SHANE
Published: July 2006

An analog mapping system using a true bipolar left ventricular balloon electrode array is described, which enables simultaneous unipolar and bipolar recordings. It is an adaptation of a previous clinical analog mapping system used in the investigation of ventricular arrhythmias. The bipolar balloon array consists of 112 electrode pairs, each having a 2‐mm separation. The signals from the electrodes are sensed in parallel by separate unipolar and bipolar amplifier units, which then drive a common multiplexer bus. The bipolar recording unit consists of high quality instrumentation amplifiers with adjustable gain and exhibits a full bandwidth minimum common mode rejection of 78 dB. Using this combination, it is possible to record local cardiac micropotentials while still retaining the advantages of unipolar electrograms to track overall cardiac activation.
Analysis of Deaths in Patients with an Implantable Cardioverter Defibrillator
Authors: EDEL THOMAS B. , MALONEY JAMES D. , MOORE STEPHEN L. , MCALLISTER HUGH , GOHN DOUGLAS , SHEWCHIK JEANNIE M. , ALEXANDER LORI , FIRSTENBERG MICHAEL S. , CASTLE LON W. , SIMMONS TONY W. , WILKOFF BRUCE L. , TROHMAN RICHARD
Published: July 2006

The cause of death and clinical characteristics of 26 patients that died after impIantable Cardioverter defibril‐lator placement were reviewed and compared to the 145 patients still living after a mean follow‐up of 17 months. Operative mortality was 4% (7/171) and resulted from postoperative ventricular arrhythmias (four patients), heart failure (two patients), and respiratory failure (one patient). Operative mortality was significantly higher (1.7% vs 9.6%, P < 0.05) following concomitant surgical procedures. Total late mortality was 11% (18/171). Thirteen deaths (75%) occurred in‐hospital from progressive deterioration of left ventricular function (nine patients), arrhythmia (two patients), and noncardiac causes (two patients). Outpatient mortality was 3.5% (6/171) and resulted from presumed sudden cardiac death in five of six patients; two of the five had devices that were inactive, one had high defibrillation thresholds, and two had suspected baradyarrhythmic deaths. One postoperative death and one late in‐hospital death were also considered sudden cardiac deaths for a total of seven patients with defibrillation system failures. By multivariant analysis, preoperative clinical characteristics associated with a worse prognosis following defibrillator implantation were identified: presentation as ventricular tachycardia (P < 0.02), induction of sustained monomorphic ventricular tachycardia (P < 0.05), poor left ventricular performance (P < 0.01), poor functional status (P < 0.001), and the use of diuretics (P < 0.01). Frequent device discharges (P < 0.001) and concomitant antitachycardia pacing systems (P < 0.001) were markers for greater arrhythmia recurrence and were potent predictors of a worse prognosis and particularly sudden death.
Atrial Vulnerability and Electrophysiology Determined in Patients With and Without Paroxysmal Atrial Fibrillation
Authors: KÜHLKAMP VOLKER , HAASIS RAINER , SEIPEL LUDGER
Published: July 2006

For elucidation of atrial electrophysiology and vulnerability an electrophysiological study was performed in 45 patients with documented paroxysmal atrial fibrillation and a control group (n =46), Atrial vulnerability was assessed by programmed atrial stimulation with up to two extrastimuli during sinus rhythm and paced cycle lengths of 600 msec, 430 msec and 330 msec. Sustained atrial fibrillation or flutter was induced in 37/45 patients with paroxysmal atrial fibrillation in contrast to 9/46 patients in the control group (P < 0.001), Left atrial diameter (M‐mode echocardiogram), P wave duration, sinus cycle length, sinus node recovery time, and the effective refractory period of the right atrium were not significantly different between the two study groups. Intraatrial conduction time from the high right atrium (HRA) to the basal right atrium (A) and the functional refractory period of the right atrium were significantly longer in patients with paroxysmal atrial fibrillation.
Subxiphoid Approach for Implantable Cardioverter Defibrillator in Patients with Previous Coronary Bypass Surgery
Authors: BECKMAN DANIEL J. , CREVEY BARRY J. , FOSTER PETER R. , BANDY MARIA , EVANS MARIA
Published: July 2006

From February 1988 until August 1991, 28 patients with prior coronary artery bypass grafting (CABG) received implantable Cardioverter defibrillator (ICD) therapy via a subxiphoid approach. Only one patient required conversion to a median sternotomy incision. The mean defibrillation threshold was 11.9 ± 4.4 J. The mean R wave was 8.2 ± 3.7 mV. One perioperative death occurred due to heart failure (mortality rate 1/28 [3.50%]). No patient required reexploration for bleeding. The subxiphoid method for ICD electrode implantation is safe and reliable in patients with prior CABG surgery.
Suppression of Incessant Ventricular Tachycardia in Hypertrophic Cardiomyopathy Associated with Improvement of Severe Left Ventricular Dysfunction
Authors: MCAREAVEY DOROTHEA , FANANAPAZIR LAMEH
Published: July 2006

A 32‐year‐old black man presented with a history of palpitations since childhood and two syncopal episodes. He was found to have incessant ventricular tachycardia, impaired left ventricular contraction (ejection fraction 9%), and nonobstructive hypertrophic cardiomyopathy. Procainamide abolished the arrhythmia and the ejection fraction rose to 22% in sinus rhythm. Later treatment was switched to amiodarone, which suppressed the ventricular tachycardia but necessitated pacemaker implantation. He has remained well during the subsequent 2 years. Left ventricular ejection fraction has increased to 47% measured in paced rhythm. The improvement in left ventricular function has been attributed to suppression of the incessant ventricular tachycardia.
Modification of Late Potentials by Intracoronary Ethanol Infusion
Authors: DAILEY SHARON M. , KAY G. NEAL , EPSTEIN ANDREW E. , PLUMB VANCE J.
Published: July 2006

Antiarrhythmic drugs have no consistent effects on the signal‐averaged electrocardiogram (ECG) while successful surgical ablation of ventricular tachycardia is known to abolish late potentials. Ten patients with prior myocardial infarction had successful ablation of recurrent sustained ventricular tachycardia by selective ethanol infusion into a small coronary vessel supplying the tachycardia origin. Signal‐averaged ECGs were performed before and after initially successful ablation in patients without pacemaker dependence or infra‐ventricular conduction delay to assess the effects on late potentials and to determine if the signal‐averaged EGG could predict ventricular tachycardia recurrence. Only four of ten patients were eligible for study and all four had late potentials prior to ethanol ablation. Late potentials were abolished in one patient who has not had an arrhythmia recurrence in 25 months. One patient with sudden death and another patient with ventricular tachycardia recurrence had persistent late potentials post procedure that were modified by a reduction in terminal voltage and lengthening of terminal low amplitude signal. The fourth patient who receives chronic amiodarone had no arrhythmia recurrence in spite of persistent but modified late potentials. Thus, the abolition of late potentials after ethanol ablation may predict freedom from arrhythmia recurrence.
Radiofrequency Catheter Ablation of the AV Node to Improve the Function of an Antitachycardia Implantable Defibrillator
Authors: PITNEY MARK R. , DAVIS MICHAEL J. , MAY CATHERINE D.
Published: July 2006

A case of coexisting atrial fibrillation and ventricular tachycardia in a patient with an implantable cardioverter defibrillator is described. Despite careful reprogramming, the device was not always able to distinguish between the two arrhythmias and continued to deliver inappropriate antitachycardia therapy including DC shocks. Attempts to pharmacologically control the atrial fibrillation were unsuccessful so radiofrequency ablation of the atrioventricular node was performed. Following successful ablation, there have been no further false detections nor episodes of further ventricular tachycardia.
Effects of An Acute Increase in Atrial Pressure on Atrial Refractoriness in Humans
Authors: CALKINS HUGH , EL‐ATASSI RAFEL , KALBFLEISCH STEVEN , LANGBERG JONATHAN , MORADY FRED
Published: July 2006

Contraction‐excitation feedback has been studied extensively in mammalian ventricles. In contrast, little is known about contraction‐excitation feedback in mammalian atria. The objective of this study was to investigate the effect of acute alterations in atrial pressure, induced by varying the atrioventricular (AV) interval, on atrial refractoriness. Twenty patients without structural heart disease participated in the study. In each patient the atrial effective (ERP) and absolute refractory periods (ARP) were measured during AV pacing at a cycle length of 500 msec and an AV interval of 120 msec. Acute increases in atrial pressure were induced by pacing the atrium and ventricle simultaneously for the final two beats of the drive train. The ERP was defined as the longest extrastimulus coupling interval that failed to capture with an extrastimulus current strength of twice the stimulation threshold. The ARP was defined in a similar manner with an extrastimulus current strength of 10 mA. The ERP and ARP were determined using the incremental extrastimulus technique. A subset of patients had the pacing protocol performed during autonomic blockade. As the AV interval of the final two beats of the drive train was shortened from 120 msec to 0 msec, the peak right atrial pressure increased from 7 ± 3 mmHg to 15 ± 5 mmHg (P < 0.001). The increase in atrial pressure associated with simultaneous pacing of the atrium and ventricle resulted in shortening of the atrial ERP and ARP by 7.3 ± 5.2 and 6.2 ± 3.5 msec, respectively (P < 0.0011). Similar results were obtained during autonomic blockade. These findings confirm the presence of contraction‐excitation feedback in normal human atria.
A Unique Preexcitation Pattern Related to an Atypical Anteroseptal Accessory Pathway
Authors: TEO WEE SIONG , GUIRAUDON GERARD , KLEIN GEORGE J. , LEITCH JAMES W. , YEE RAYMOND
Published: July 2006

Accessory atrioventricular pathways have traditionally been classified by anatomical Jocation to four areas, namely anteroseptal, posteroseptal, and right and left free walls. Each of these have been associated with a relatively distinct preexcitafion pattern electrocardiographically. We describe a patient with a unique EGG pattern suggesting preexcitation to the right ventricular outflow region, Preoperative and intraoperative electrophysioJogicaJ testing confirmed the presence of an accessory pathway with an atrial insertion site near the His bundle, decremental anterograde conduction, and a ventricular insertion site in the upper part of the interventricular septum. Operative ablation near the atrial insertion site eliminated preexcitation.
The Hemodynamic Importance of Atrial Systole: A Function of the Kinetic Energy of Blood Flow?
Authors: LINDE‐EDELSTAM CECILIA M. , JUHLIN‐DANNFELT ANDERS , NORDLANDER ROLF , PEHRSSON S. KENNETH
Published: July 2006

The relative importance of atrial systole on left ventricular filling was investigated at rest and during exercise in 25 patients with dual chamber pacemakers. The mean blood flow velocity over the atrial valve, the velocities of the rapid filling phase (E), the active filling phase (A), and the E/ A ratio were determined for pulsed Doppler‐echocardiography. The patients were first examined at rest during AV sequential pacing (DVI) at 70 and 104 beats/mm. The investigation was subsequently repeated during atrial synchronous pacing (VDD) at rest and during supine submaximal exercise at workloads adjusted to achieve heart rates corresponding to those during DVI pacing. The mean blood flow velocity at rest did not differ between DVI and VDD pacing at 70 beats/mm (0.46 vs 0.49 m/sec). When (he resting heart rate was increased to 104 beats/min (DVI) the mean blood flow velocity increased to 0.56 msec (P < 0.001). At a corresponding heart rate during exercise (VDD) the velocity increased to 0.70 msec (P < 0.001). At a resting heart rate of 70 beats/min the E/A ratio (n = 14) did not differ significantly between DVI and VDD pacing. With an increased resting heart rate (DVI) the E/A ratio decreased from 0,94 ± 0.45 to 0.78 ± 0.18; NS. When the heart rate increased during exercise (VDD) the E/A ratio increased from 0.75 ± 0.14 to 0.97 ± 0.16; P < 0.001. There was a positive correlation between the increase of the mean blood flow velocity and the increase of the E/A ratio during exercise (r = 0.69, P < 0,01). No such correlation was found when the heart rate was changed at rest. Thus, the importance of atrial systole on ventricular filling diminishes during exercise in accordance with increasing blood flow velocity, which by physical principles is related to the kinetic energy. The relative importance of atrial systole is hence inversely correlated to the kinetic energy of the blood flow.
Autonomic Nervous System Controlled Closed Loop Cardiac Pacing
Authors: PICHLMAIER A.M. , BRAILE D. , EBNER E. , GRECO O.T. , HUTTEN H. , von KNORRE G.H. , NIEDERLAG W. , RENTSCH W. , VOLKMANN H. , WEBER D. , WUNDERLICH E. , SCHALDACH M.
Published: July 2006

A multicenter clinical study is presented, which focuses on the reestablishment of closed loop cardiac control in patients with chronotropic insufficiency. Using the information about sympathetic tone contained in the myocardial contractility, it is possible to reconnect the heart rate to the physiological control mechanisms. Intracardiac impedance is measured with the ventricular electrode and the ventricular inotropic parameter (VIP) is derived from that. The VIP serves directly as input to the control of heart rate by the pacemaker. Over 200 patients have received autonomic nervous system (ANS) controlled pacemakers. The patientpacemaker system was investigated in different ways. This included standard exercise tests, long‐term studies of every day activities over 24 hours, psychological, and pharmacological challenges. To prove the validity of the approach we specifically looked at (1) the appropriateness of changes in paced heart rate with sympathetic tone during exercise, (2) the correlation between heart rate and sinus rate, if detectable, and (3) the correlation between the echocardiographically determined preejection period (PEP) and the VIP controlled heart rate.
External Vibration Interference of Activity Based Rate Responsive Pacemakers
Authors: SNOECK JOS , BERKHOF MARC , CLAEYS MARC , VRINTS CHRIS , BOSMANS JOHAN , DECOSTER HANS , HEUTEN HILDE
Published: July 2006

The change of the pacing rate in response to external vibration interference was assessed in four rate responsive pacemakers with a piezoelectric crystal (Medtronic Activitrax 8403, Siemens Sensolog 3, Biotronik Ergos 01, and Medtronic Legend 8417) and one with an accelerometer (CPI Excel VR 1119). They were tested in the laboratory. External vibration was simulated in vitro by exposing the different pacemakers to a controlled sinusoidal vibration force generated by a Millar pressure vibration amplifier type MGM‐30 (Millar Instruments, Inc., Houston, TX, USA). All pacemakers were programmed at standard settings. Two types of vibration forces were applied: (1) one with varying amplitude but with constant vibration frequency; and (2) one with varying frequency but with constant vibration amplitude. In this manner curves of pacing rate versus vibration forces versus vibration frequency were obtained. High vibration forces and low vibration frequencies were associated with the highest pacing rate response. In this experimental setting, the pacemaker based on the accelerometer principle apparently was the least sensitive to high frequency vibrations, which are known to be related to environmental interference. It also seemed more appropriately responsive in the lower frequency range, which is more appropriate for the detection of true physiological activity.
Feasibility of Using Intracardiac Impedance Measurements for Capture Detection
Authors: ALT E. , KRIEGLER C. , FOTUHI P. , WILLHAUS R. , COMBS W. , HEINZ M. , HAYES D.
Published: July 2006

Energy consumption and longevity of modern pacemakers are determined by the controlling electronic circuitry and by the stimulation energy. While with technological progress the electronics' energy consumption has been reduced significantly, clinical practice shows that many cardiac pacemakers are programmed to suboptimal settings with regard to minimization of pacing energy consumption. Several methods for optimizing pacemaker output settings have been proposed in the past. The most promising concept is an output parameter optimizing pacemaker with automatic capture detection. We examined whether it is possible to distinguish between effective and ineffective pacemaker stimulus capture by analyzing high pass filtered intracardiac impedance signals that are derived from standard bipolar pacing leads. In one series of 11 patients undergoing replacement or implantation of chronic bipolar pacemakers, four patients during electrophysiology studies, and eight volunteers undergoing invasive electrophysiology trials, we examined intracardiac impedance signals obtained with various stimulation rates and output parameter settings. Additionally we analyzed a series of five patients with implanted pacemakers that can measure and telemeter intracardiac impedance signals. Several evaluation concepts have been analyzed regarding their ability to discriminate between effective and ineffective stimuli. We developed an adequate algorithm that detects capture or loss of capture at different output parameter settings based on intracardiac impedance analysis. The sensitivity is 98.5% and specificity is 91% to loss of capture for the currently investigated algorithm and this can be used to determine the optimal setting of pulse width and amplitude with regard to energy consumption. This concept is currently under realization in the external programmer and in the future an implementation of these algorithms within the pacemaker itself is intended.
Complications of Single Lead VDD Pacing in 35 Patients with AV Block
Authors: PARRAVICINI U. , ZANETTA M. , ZENONE F. , BIELLI M.
Published: July 2006

The implantation of a VDD system is comparable to that of a VVI system, but its management is associated with typical complications of dual chamber pacing. In 35 patients with symptomatic AV block and normal sinus node function, two different VDD pacing systems were implanted. Most of the complications described and their mode of resolution were common to VDD and DDD pacing; however, the VDD system eliminated the need for two separate leads. We, therefore, favor single lead VDD pacing in the treatment of complete AV block with normal sinus node function.
VDD Single Pass Lead Pacing; Sustained Pacemaker Mediated Tachycardias Unrelated to Retrograde Atrial Activation
Authors: SERMASI SERGIO , MARCONI MARCO
Published: July 2006

Pacemaker mediated tachycardias (PMTs) are a well known complication of P synchronous pacing. Although the initiating mechanisms are severel, all of them are associated with retrograde atrial activation, which is sensed by the atrial sensing channel, resulting in ventricular pacing. In 19 patients suffering from symptomatic AV conduction disturbances and normal sinus node function, a VDD pacing system connected to a single pass ventricular lead with dual chamber electrodes was implanted. The bipolar atrial electrode, floating in the right atrium, was used to detect endocardial atrial electrograms that were differentially processed within the pacemaker for optimal discrimination and filtering of undesirable signals. The widely programmable atrial sensitivity (amplitude and filtering) allowed stable P synchronized ventricular pacing in all patients, but in five of them, sustained PMTs not related to retrograde atrial activation was documented during the follow‐up. The common mechanism for the onset and maintenance of these PMTs was traced to the abnormal sensing of the terminal forces of ventricular activation and for of the T wave. The possibility of interferences between ventricular and atrial electrodes (crosstalk) was also considered, The reduction of atrial channel sensitivity represented in all cases the only effective procedure to prevent this type of PMT. In conclusion, the best signal to noise ratio is an important endpoint (o assure the proper function of a single lead VDD pacing system. Furthermore, using the differential amplifier built within the pacemaker, consideration should be given to the optimal mode of rejection of the terminal forces of the QRS and T wave.
Evaluation by Cardiopulmonary Exercise Test of DDDR Versus DDD Pacing
Authors: CAPUCCI ALESSANDRO , BORIANI GIUSEPPE , SPECCHIA SALVATORE , MARINELLI MASSIMO , SANTARELLI ANDREA , MAGNANI BRUNO
Published: July 2006

In eight patients (age 62 ± 6 years) a DDDR pacemaker was implanted for sick sinus syndrome (three cases) or second‐ and third‐degree AV block (five cases). In five subjects chronotropic incompetence (maximal heart rate on effort < 110 beats/min) was present before implantation. One month after implantation the patients were randomized to DDDR or DDD pacing for 3 weeks each, with subsequent crossover, and at the end of each period a symptom limited Cardiopulmonary exercise test (25 watts/2 min) was performed and the patients were requested to fill a symptoms questionnaire. Results: DDDR pacing, compared to DDD, was associated with higher maximal heart rates (127 ± 20 vs 110 ± 27 beats/min, P < 0.02), higher (VO2 max (25.4 ± 6.1 vs 21.5 ± 7.8 mL/kg/per min, P < 0.03) and higher VO2 at the anaerobic threshold (20.3 ± 5.0 vs 15.8 ± 4.9 mL/kg per min, P < 0.03), without significant differences in mean exercise time (526 ± 193 vs 472 ± 216 sec, NS). The increase in VO2 max obtained in DDDR versus DDD was significantly related to the increase in maximal heart rate (r = 0.72, P < 0.05) and the increase in VO2 at the anaerobic threshold obtained in DDDR versus DDD was related to the increase in heart rate at the anaerobic threshold (r = 0.81, P < 0.02). In patients with chronotropic incompetence the improvement obtained in DDDR versus DDD was even more significant (VO2 max = 22.7 ± 5.9 vs 16.1 ± 4.4 mL/kg per min, P < 0.03; VO2 at the anaerobic threshold = 18.4 ± 5.1 vs 13.2 ± 2.8 mL/kg per min, P < 0.05; exercise time = 438 ± 132 vs 352 ± 150 sec, P < 0.02). In the population as a whole, no significant differences were found relative to subjective symptoms, meanwhile in patients with chronotropic incompetence a better subjective tolerance was apparent with DDDR than with DDD pacing. In conclusion, DDDR pacing induces a significant improvement of exercice capacity, in comparison to DDD pacing, related to the ability to reach higher heart rates during exercise. This phenomenon is particulary evident in patients with chronotropic incompetence in whom DDDR pacing also is subjectively better tolerated.
Aerobic Capacity in Rate Modulated Pacing
Authors: LEMKE BERND , DRYANDER STEFAN V. , JÄGER DETLEF , MACHRAOUI ABDERRAHMAN , MAcCARTER DEAN , BARMEYER JURGEN
Published: July 2006

Whether heart rate or AV synchrony is the most important factor for an increase in aerobic capacity was evaluated in a comparative study between sinus bradycardia, VVIR, DDD, and DDDR stimulation. Sixteen patients (mean age 67 years) with chronotropic incompetence and impJanted DDDR pacemaker (Telectronics META 1250) were randomly studied by cardiopulmonary exercise testing. All patients were exercised to their anaerobic threshold (ATJ with the following heart rates: DDD 84 ± 3, WIR 110 ± 5, and DDDR 116 ± 6 beats/min. Mean oxygen uptake (VO2, mL/kg per min) at AT was 7.4 ± 0.3 in DDD and WIR modes. A 12% increase was measured in DDDR mode (8.3 ± 0.4). Compared to VVIR work capacity in the DDDR mode was improved by 17% (41 vs 48 W/min). In patients with isolated sinus node disease (n = 9) the increase of VO2 and work capacity at AT during DDDR mode was more pronounced (16% and 20%, respectively, compared to VVIR). In patients with intermittent second or third degree AV block (n = 7) the differences between the pacing modes were not significant. This might partly be due to a lesser degree of chronotropic incompetence in this subgroup. In conclusion only the conjunction of heart rate increase and preservation of AV synchrony provides a significant improvement in aerobic capacity during exercise.
Comparison of Intrinsic Versus Paced Ventricular Function
Authors: JUTZY ROY V. , FEENSTRA LINDA , PAI RAMDAS , FLORIO JOSEPH , BANSAL RAMESH , AYBAR RANDALL , LEVINE PAUL A.
Published: July 2006

There is increasing evidence supporting the benefits of providing optimum AV delay in cardiac pacing, though controversy exists regarding its value and the benefits of intrinsic versus paced ventricular activation. This study compared various AV delays at rest in patients whose native AV delays were 200 msec. Only patients with DDD pacemakers who had intact AV conduction and normal ventricular activation were included in the study. Nine patients were studied. Methods: Ten studies were performed. Evaluation was done in AAI and DDD modes at paced heart rates of 60/min or as close as possible to the intrinsic heart rate if this was > 60/min. Stroke volume (SV) and cardiac output (COJ were measured. Results: When AV sequential pacing in the DDD mode with an optimum AV delay was compared to AAI pacing with a prolonged AV interval, the average optimum AV delay in the DDD mode was 157 msec and ranged from 125 to 175 msec. The average AV interval in the AAI mode was 245 msec and ranged from 212 to 300 msec. In the DDD mode, there was an overall significant improvement in CO of 11% and SV of 9%. Patients with intrinsic AV conduction times of > 220 msec showed an overall significant improvement in CO of 13% and SV of 11%. In patients with intrinsic AV conduction times of < 220 msec, an improvement in CO of 6% and SV of 4% was seen. Conclusions: (1) An optimum AV delay is an important component of hemodynamic performance; and (2) AV sequential pacing at rest with an optimum AV delay may provide better hemodynamic performance than atrial pacing with intrinsic ventricular conduction when native AV conduction is prolonged > 220 msec.
Precision of Impedance Cardiography Measurements of Cardiac Output in Pacemaker Patients
Authors: OVSYSHCHER ILYA , GROSS JAY N. , BLUMBERG STEPHEN , FURMAN SEYMOUR
Published: July 2006

Objective hemodynamic assessment of pacemaker patients is necessary for gauging responses to changes in programming or other conditions that affect the circulation. Impedance cardiogrphy permits noninvasive, repetitive determinations of cardiac output at short intervals, but data regarding variability of this method in patients with pacemakers is unavailable. Thirty‐eight patients with implanted pacemakers (24 DDD, 14 VVI) and six normal subjects were studied, A computerized impedance cardiograph was used to calculate cardiac output from the product of the first derivative of the thoracic impedance signal (dZ/dt), the ventricular ejection time, and heart rate. Each patient was studied while supine after a period of at least 15 minutes of rest and repeated impedance measurements (about ten) were performed. Fourteen patients were studied in sinus rhythm, 24 were studied during DDD pacing, and 32 patients were studied during VVI pacing. Cardiac and stroke indices were calculated 706 times on the basis of 11,296 accepted beats. Variability was assessed by methods that analyzed serial measurements and variability between two consecutive and nonconsecutive measurements. The mean indices and coefficients of variation of two measurements and of serial measurements in sinus rhythm and during DDD pacing were 4%; in VVI it was 6%. The precision of impedance Cardiography in all pacing modes, as demonstrated by analysis of variability, indicates that detected changes of stroke volume and cardiac output > 7% on serial (two and more) measurements, performed by the same operator and during the same session, represent true hemodynamic alterations with 95% confidence. Conclusions are that the precision of impedance Cardiography may be comparable or superior to other commonly used techniques and that the data obtained by this technique is valuable investigationally and clinically.
Noninvasive Transcutaneous Cardiac Pacing: Modern Instrumentation and New Perspectives
Authors: TRIGANO JACQUES A. , BIRKUI PIERRE J. , MUGICA JACQUES
Published: July 2006

Perspectives. Noninvasive transcutaneous cardiac pacing has evolved from a simple stand aione unit with no ventricular sensing to a complete cardiac arrest resuscitation system combining synchronous pacing and defibrillation capabilities and using a single set of multifunction electrodes. In current instru‐mentation, four configurations exist including stand alone unit, modolar configuration, built‐in monitor and recorder, and built‐in monitor, recorder and defibrillator. In present day devices, ventricular sensing, extensive programmability, and large surface electrodes are general features. Capture monitoring requires specific integrated electrocardiographic capability. Future developments are expected to involve low threshold electrode technology, integrated mechanical monitoring, and interdevice electrode compatibility.
Prediction of Permanent Atrial Sensing by Preoperative Esophageal Atrial Wave Evaluation
Authors: VROUCHOS G. , KIUPELOGLOU G. , LAGUVARDOS P. , KONDOPODIS M. , FRAGIADULAKIS G.
Published: July 2006

Atrial undersensing is a common problem in permanent atrial and dual chamber pacing. The purpose of this study was to evaluate the relationship between transesophageal atrial wave (EsAW) and right atrial endocavitary (RA). Forty‐seven patients 72 ± 9.7 years of age, with symptomatic bradyar‐rhythmias were studied. The EsAW was filtered with a high pass filter of 10 Hz (Arzco preamplifier‐filter), using 1, 2, and 3 cm bipolar transesophageai catheters. Atrial bipolar floating 1, 2, and 3 cm electrograms from the high RA (HRA) and from the mid RA (MRA), as well as unipolar electrograms from the right auricle (RAUR) were recorded 1 day later. Comparison by paired t‐test showed no significant differences between EsAW and bipolar sensing in RA, but significant differences between EsAW and RAUR (P = 0.0001). The results of the Spearman correlation coefficient for sensing (mV) for EsAW, HRA, and MRA, respectively, were: 1 cm, 1.8 ± 0,9, 1.7 ± 0,9, and 1.9 ± 0.9 (z > 3.5; P < 0.0003); 2 cm, 2.2 ± 0.9, 1.9 ± 0.8, and 2.1 ± 0.9 (z > 2.3; P < 0.03); 3 cm, 2.1 ± 1, 2 ± 0.9, and 2.2 ± 1.0 (z > 2.9; P < 0.003); and the result for the monopolar RAUR was 3.0 ± 1.0 (z < 1.4; P > 0.17). These findings, if confirmed in more patients, indicate that preoperative EsAW recording could be useful in estimating the quality of bipolar floating electrograms from the RA but not of unipolar RAUR.
Termination of Tachycardias by Transesophageal Electrical Pacing
Authors: VOLKMANN HANS , DANNBERG GUDRUN , HEINKE MATTHIAS , KÜHNERT HELMUT
Published: July 2006

To evaluate the therapeutic significance of noninvasive transesophageal pacing for termination of tachycardias the method of rapid atrial or ventricular transesophageal pacing was used in 233 patients with different tachycardiac arrhythmias. We were able to terminate atrial flutter in 136 of 162 patients by transesophageal rapid atrial stimulation (conversion to sinus rhythm in 75 cases, induction of atrial fibrillation in 61 cases). Atrial tachycardias were interrupted in 17 of 23 patients (sinus rhythm in 11 cases, atrial fibrillation in six cases). AV reciprocating/AV nodal supravenrricular reentry tachycardias were terminated in 62 of 63 patients (sinus rhythm in 58 cases, atrial fibrillation in four cases). By transesophageal rapid ventricular pacing ventricular tachycardias could be terminated in ten of 15 patients. The success rate of transesophageal pacing was influenced by the pacing rate, by the type of tachycardiac arrhythmia inclusive by the type of atrial flutter and by the tachycardia's cycle length. Because the success rates are comparable with invasive technique and the procedure is simpler, the noninvasive transesophageal antitachycardiac pacing should be respected as the method of the first choice in patients with supraven‐tricular tachycardias.
Atrial Stimulation by Means of Floating Electrodes: A Multicenter Experience
Authors: BONGIORNI MARIA GRAZIA , BEDENDI NICOLA ,   THE MULTIGENTER STUDY GROUP
Published: July 2006

It is well established that single lead VDD pacing is a physiological, reliable, and easy to use mode of pacing. The major limitation of VDD pacing is the need of a normal sinus node function, confirming its indication to patients with isolated atrioventricular conduction disturbances. The Phymos 830 pacing lead was originally designed for VDD pacing in association with the Phymos MPS pulse generator; it has a floating atrial dipole with an interelectrode distance of 3 cm; the distal electrode is 11, 13, or 15 cm proximal to the tip. As a result of the incidental observation of atrial captures occurring at very low pulse amplitudes delivered from the floating dipole of this lead, a 13‐center Italian study was initiated to test the systematic feasibility of this type of atrial pacing. Pacing parameters were set and strength‐duration curves were acquired with the PSA Master 470 external device. The investigation was performed at pacemaker implant in 114 patients in the supine position. The tip of the electrode was positioned at the right ventricular apex and the atrial dipole at the site of the highest endocavitary signal. Atrial bipolar pacing was performed with the proximal electrode as the cathode. Stable atrial capture was obtained in 108 of 114 patients (94.7%); pacing threshold was < 3.5 V with a pulse width of 1 msec in 85 of 108 patients. Results of voltage threshold were: 2,99 ± 1.25 and 2.59 ± 1.13 V at pulse widths of 0.5 and 1 msec, respectively. The mean value of atrial pacing impedance (5 V, 1 msec) was 601.2 ± 221 Ohm; the mean value of the endocavitary signal amplitude was 1.53 ± 0.48 mV. During deep breathing loss of capture was observed in only 8.3% of patients; these patients regularly had an atrial pacing threshold higher than 3.5 V. Diaphragmatic stimulation occurred in 19.2% of patients at an output of 5 V and 1 msec. Our results suggest that stable atrial pacing is possible with floating electrodes in a high percentage of patients; in 85/114 patients (74.5%) atrial capture was reliable at a satisfactory mean pacing threshold. This experience shows that single lead DDD pacing is possible and may be reliable in acute conditions; and supports the availability of this pacing mode in selected patients. It can be considered a starting point for improvements in techniques and materials.
Evaluation of an In‐Line Bipolar Polyurethane Ventricular Pacing Lead
Authors: SWEESY MARK W. , FORNEY CATHLEEN C. , HAYES DAVID L. , BATEY ROBERT L. , FORNEY RICHARD C.
Published: July 2006

A study was undertaken to evaluate the performance of the Medtronic 4012 polyurethane in‐line bipolar pacing electrode. One hundred twenty six patients implanted with the 4012 lead were followed by our clinic with 116 of these leads implanted at our institution. Patients were followed a minimum of every 4 months. Testing included the performance of stimulation thresholds, sensing thresholds, and provocative maneuvers to evaluate for myopotential inhibition testing a minimum of every eight months. There were 12 documented lead failures of the total 126 patients. Further analysis was limited to the ten failures occurring in the 116 leads implanted at our center. All ten failed leads utilized the suture anchoring sleeve. Six of the leads were left cephalic implants, three were right cephalic, and one was right subclavian. Manifestations of failure included: seven oversensing abnormalities, three undersensing, four loss of ventricular capture, one premature end of service, four lead impedance decreases to < 250 Ω and some presentations in combination. No leads were explanted for evaluation. The Kaplan‐Meier product limit method was used to estimate the time to lead failure. The probability of not experiencing a lead failure within the first 4 years of implant is estimated to be 0.9103 (SE = 0.0338). Pacemaker dependent patients implanted with the 4012 lead should be given special consideration for prophylactic replacement.