bluuebunny/crossref_metadata_2025 huggingface dataset:
Acute Hemodynamic Improvement by Pacing in Patients with Severe Congestive Heart Failure
Authors: AURICCHIO ANGELO , SALO RODNEY W.
Published: July 2006

Since the first report on dual chamber pacing for congestive heart failure (CHF) in 1991, a number of investigators have explored the topic with conflicting results. These conflicts may arise from an incomplete understanding of the mechanisms by which pacing improves cardiac function. Potential mechanisms include: (1) increase in filling time: (2) decrease in mitral regurgitation: (3) optimization of left heart mechanical atrioventricular delay (left heart MAVD); and (4) normalization of ventricular activation. One or more of these mechanisms may be operative in an individual patient, implying that patients may require individuol optimization. Acute pacing studies were conducted on nine CHF patients, NYHA Class II‐III to Class IV. Measurements of conduction times in sinus rhythm revealed: (1) normal interatrial conduction times (59 ± 5 ms) in all patients, with wide variations in interventricular conduction times (range, −15–105 ms); and (2) a wide range of left heart MAVD (range, 97–388 ms). While pacing the right, left, or both ventricles, measurement of high fidelity aortic pressure and mitral and aortic velocities revealed the following: (1) 6 of 9 patients increased mean pulse pressure over sinus value during RV orLV pacing at an optimal A V delay: (2) the maximum aortic pulse pressure was achieved when the atrium was not paced: an 8% increase over sinus pulse pressure with paced RV versus a 5% decrease for paced atrium and RV at optimum AV delay (paired Student's t‐test, P = 0.01), and a 0% increase over sinus with paced LV versus 7% decrease for paced atrium and LV at optimum AV delay, P < 0.05: (3) significant dependence on pacing site was noted, with 4 patients doing best with RV pacing. 3 patients achieving a maximum with LV pacing, and 2 patients showing no preference; and (4) 2 of 4 patients with restrictive filling patterns were converted to nonrestrictive patterns with optimum pacing. Patient hemodynamics appear to benefit acutely from individually optimized pacing. Increases in filling time, optimization of left heart MAVD, and normalization of intraventricular activation are the most significant mechanisms. Atrial pacing is inferior to atrial sensed modes if the patient has a functional sinus node.
Ventricular Fibrillation and Sudden Death After Radiofrequency Catheter Ablation of the Atrioventricular Junction
Authors: GEELEN PETER , BRUGADA JOSEP , ANDRIES ERIK , BRUGADA PEDRO
Published: July 2006

Two hundred thirty‐five patients underwent RF catheter abhtion of AV conduction for symptomatic drug refractoiy AF (84%), atrial flutter (9%), and atrial tachycardia (7%). In the first 100 patients, postahlation pacing was not prospectively set at any specific rate and was always ≤ 70 beats/min. In the next 135 patients, postabiotion pacing was prospectively set at 90 beats/min for 1–3 months. Six of the first 100 patients (6%) had VF or sudden death after the RF procedure and none (0%) of the next 135 patients did (P < 0.05). One of the six patients had recurrent VF 4 days after the ablation. Five patients were successfully resuscitated and one patient died. There were no statistically significant differences between patients with and without (aborted) sudden death or between the first 100 and the next 135 patients with respect to age, sex, underlying heart disease, EF, number of RF applications, or leftor right‐sided approach of the procedure. VF mostly occurred during episodes of slow ventricular escape rhythms or during slow ventricular pacing. We conclude that malignant ventricular arrhythmias and sudden death are possible complications of RF ablation of the AV junction. The mechanism of these complications could have a bradycardia dependent nature and it seems that the occurrence of malignant arrhythmias can be prevented by temporarily pacing the heart at relatively fast rates immediately after ablation.
Time Dependent Variations of Stimulus Requirements in Spinal Cord Stimulation for Angina Pectoris
Authors: ANDERSEN CLAUS
Published: July 2006

The aim of the study was to observe changes over time of the stimulation requirements in spinal cord stimulation (SCS). Of 60 patients treated with SCS, 25 patients were selected because they had neurostimulators capable of measuring impedance noninvasively, and had not experienced electrode displacement. All 25 patients had Medtronic Pisces Quad 3487A (Medtronic, Inc.) neuroelectrodes with the tip positioned in the thoracic epidural space. The accuracy of the neurostimulators impedance measuring circuit was investigated in a test circuit. The error was < 11%. Stimulus requirements and impedance were recorded at the implantation and at follow‐ups during a period of 24 months. During the first month after implantation, the stimulus requirements for satisfactory effect varied between +406% and ‐34%. After that period, only minor deviations were observed in most patients. To optimize the pain reducing effect of the spinal cord stimulation, frequent follow‐ups are recommended during the first month; later on, the follow‐up intervals can be extended. No tolerance development or pain resistance developed during SCS treatment
An Unusual Cause of High Threshold Values at Pacemaker Implantation
Authors: EMILSSON KENT , ODDSSON HJORTUR , ALLARED MATS , BRORSON LEIF
Published: July 2006

An 81‐year‐old man with third‐degree A V block and weakness underwent an unsuccessful attempt at DDD pacemaker implant caused by hypothyroidism. Administration ofthyroxin until he was euthyroid permitted implantation with normal stimulation thresholds.
Inadvertent But Asymptomatic Right Atrial Perforation with Epicardial Pacing in a Neonate: A Rare Complication of Temporary Transvenous Cardiac Pacing
Authors: REDDY S. CHANDRA BOSE , SAXENA ANITA , IYER KRISHNA S.
Published: July 2006

We report a case of an asymptomatic right atrial perforation due to temporary cardiac pacing in a neonate.
Delayed Pinpoint Exposure of a Pacemaker Following Seat Belt Trauma
Authors: SAKAKIBARA YUZURU
Published: July 2006

A case of late pinpoint exposure of a pulse generator due to seat belt trauma is reported. This unusual complication indicates that the implant site of a pacemaker should be decided after consideration of where the patient usually sits in his car and what type of seat belt is used.
Heterogeneity in K+ Channel Transcript Expression Detected in Isolated Ferret Cardiac Myocytes
Authors: BRAHMAJOTHI MULUGU V. , MORALES MICHAEL J. , RASMUSSON RANDALL L. , CAMPBELL DONALD L. , STRAUSS HAROLD C.
Published: July 2006

The molecular basis of the potassium ion (K+) channels that generate repolarization in heart tissue remains uncertain, in part because of the molecular diversity of the voltage‐gated K+ channel family. In our investigation, we used fluorescent labeled oligonucleotide probes to perform in situ hybridization studies on enzymatically isolated myocytes to determine the identity, regional distribution, and cellular distribution of voltage‐gated K+ channel, a‐subunit mRNA expressed in ferret heart. The regions studied were from the sinoatrial node (SA), right and left atrium, right and left ventricle, and interatrial and interventricular septa, Kv1.5 and Kv1.4 were the most widely distributed K+ channel transcripts in the ferret heart (present in approximately 70%–86% and approximately 46%–95% of tested myocytes, respectively), followed byKv1.2, Kv2.1, and Kv4.2. In addition, many myocytes contain transcripts for Kv1.3, Kv2.2, Kv4.1, Kv5.1, and members of the Kv3 family, Kv1.1, Kv1.6, and Kv6.1 were rarely expressed in working myocytes, but were more commonly expressed in SA nodal cells. Two other transcripts whose genes have been implicated in the long QT syndrome, erg and KvLQT1, were common in all regions (approximately 41%–58% and 52%–72%, respectively). These results show that both the diversity and heterogeneity of K+ channel mRNA in heart tissue is greater than previously suspected
Spirals, Chaos, and New Mechanisms of Wave Propagation
Authors: CHEN PENG‐SHENG , GARFINKEL ALAN , WEISS JAMES N. , KARAGUEUZIAN HRAYR S.
Published: July 2006

The chaos theory is based on the idea that phenomena that appear disordered and random may actually be produced by relatively simple deterministic mechanisms. The disordered (aperiodic) activation that characterizes a chaotic motion is reached through one of a few well‐defined paths that are characteristic of nonlinear dynamical systems. Our group has been studying VF using computerized mapping techniques. We found that in electrically induced VF, reentrant wavefronts (spiral waves) are present both in the initial tachysystolic stage (resembling VT) and the later tremulous incoordination stage (true VF). The electrophysiological characteristics associated with the transition from VT to VF is compatible with the quasiperiodic route to chaos as described in the Ruelle‐Takens theorem. We propose that specific restitution of action potential duration (APD) and conduction velocity properties can cause a spiral wave (the primary oscillator) to develop additional oscillatory modes that lead to spiral meander and breakup. When spiral waves begin to meander and are modulated by other oscillatory processes, the periodic activity is replaced by unstable quasiperiodic oscillation, which then undergoes transition to chaos, signaling the onset of VF. We conclude that VF is a form of deterministic chaos. The development of VF is compatible with quasiperiodic transition to chaos. These results indicate that both the prediction and the control of fibrillation are possible based on the chaos theory and with the advent of chaos control algorithms.
Mechanisms of Action of Antiarrhythmic Drugs: From Ion Channel Blockage to Arrhythmia Termination
Authors: GRANT AUGUSTUS O.
Published: July 2006

Over the past decade, the strategies for arrhythmia management have been in transition. Physical methods to treat arrhythmias, such as ICDs and RF ablation, have undergone considerable refinement and wider application. Ischemic heart disease and congestive heart failure have been identified as clinical situations in which antiarrhythmic drugs have a significant proarrhythmic potential. However, drugs retain an important role in arrhythmia management. Strategies to mitigate the structural and functional changes that occur in hypertrophy, ischemia, and infarction have not been thoroughly explored. Membrane ion channels and receptors are the targets for the action of currently available drugs. The cloning and sequencing of these ion channels and receptors should improve the efficacy and specificity of drug design. Cardiac Na+, Ca2+, K+, and nonspecific cation channels have a clearly defined role in the generation of the normal action potential. Their specific roles in the various clinical arrhythmias is less certain. There are sufficient data to associate specific ionic channels with normal and abnormal automaticity and with reentry occurring in specific regions of the heart. A rational choice of antiarrhythmic drugs can be made when an arrhythmogenic mechanism and the putative underlying membrane currents can be identified based on the clinical characteristics of the arrhythmia. For a majority of clinical arrhythmias, this ideal has not been achieved. When a particular drug is used to treat an arrhythmia, the full complement of its actions will depend on which multiple ion channels or receptors are blocked and the kinetics of drug interaction with these sites.
Atrioventricular Node Reentry: Physiology and Radiofrequency Ablation
Authors: PRYSTOWSKY ERIC N.
Published: July 2006

Atrioventricular (A V) node reentry has heen recognized as a clinical arrhythmia for many years. Earlier basic investigations identified a dual AV conduction system, and atrial echo beats occurred when the refractory period of the slow conduction pathway was shorter than the fast pathway. Subsequent studies in humans confirmed the concept of dual AV node physiology and AV node reentry. Slow‐fast AV node reentry (anterograde conduction over the slow pathway and retrograde conduction over the fast pathway) occurs most frequently. The fast‐slow and intermediate varieties are much less common. A high (> 95%) cure rate occurs with radiofrequency catheter ablation with experienced electrophysiologists. Most electrophysiologists prefer the posterior approach, which results in absence or very poor conduction over the slow AV node pathway; the PR interval is minimally changed. This approach is highly successful for all three forms of AV node reentry and associated with a 1%–2% incidence of heart block in most experienced laboratories.
Right Ventricular Outflow Tract Pacing
Authors: BUCKINGHAM THOMAS A.
Published: July 2006

“He who expresses an opinion should not voice it as correct and right but set it forth as a contribution to the consensus of opinion, for the light of reality becomes apparent when two opinions coincide. A spark is produced when flint and steel come together. Man should weigh his opinions with the utmost serenity, calmness, and composure. Before expressing his own views he should carefully consider the views already advanced by others. If he finds that a previously expressed opinion is more true and worthy, he should accept it immediately and not willfully hold to an opinion of his own. By this excellent method he endeavors to arrive at unity and truth.”—Abdu'l‐Bahá1
Temperature Guided Radiofrequency Catheter Ablation of Myocardium: Comparison of Catheter Tip and Tissue Temperatures In Vitro
Authors: KONGSGAARD ERIK , STEEN TORKEL , JENSEN ØYSTEIN , AASS HALFDAN , AMLIE JAN P.
Published: July 2006

Temperature monitoring during RF ablation has been proposed as a means of controlling the creation of the lesion. However, in vivo studies have shown poor correlation between lesion size and catheter tip temperature. Thus, we hypothesized a difference between catheter tip and tissue temperatures during RF catheter ablation, and that this difference may depend on flow passing the ablation site, tip electrode length, and catheter‐tissue orientation. In vitro studies were performed using four different ablation catheters (tip electrode length: 2, 4. or 6 mm) with a thermistor or a thermocouple as temperature sensor. Set temperature was 70°C and pulse duration was 30 seconds. Pieces of porcine left ventricle were immersed in a bath of isotonic saline‐dextrose solution at 37°C. The ablation catheters were positioned perpendicularly, obliquely, or parallel to the endocardium. A temperature sensor was inserted from the epicardial side and positioned 1 mm beneath the catheter‐tissue interface. Experiments were made with a flow of 200 mL/min passing the ablation site or with no flow. The catheter tip and tissue temperatures differed significantly (P < 0.0001) during ablation. This difference increased with time, with flow passing the ablation site, with the length of the tip electrode, and when the catheter was positioned perpendicularly or obliquely to the endocardium as compared to the parallel catheter‐tissue orientation (P < 0.05), In conclusion, the tissue temperature may far exceed the catheter tip temperature, and intramyocardial superheating resulting in steam formation and popping may occur despite a relatively low catheter tip temperature. (PACE 1997; 20[Pt. I]:1252‐1260)
Modification of Atrioventricular Nodal Electrophysiology by Selective Radiofrequency Delivery on the Anterior or Posterior Approaches
Authors: CHORRO FRANCISCO J. , SANCHIS JUAN , SUCH LUIS , ARTAL LEANDRO , LLAVADOR JUAN J. , LLAVADOR ESTEBAN , MONMENEU JOSE V. , LOPEZ‐MERINO VICENTE
Published: July 2006

An analysis was made in 14 isolated and perfused rabbit hearts of the electrophysiological effects of selective radiofrequency (RF) delivery in the anterior (group I, n = 7) or posterior zone (group II, n = 7) of the Koch triangle, with the aim of modifying atrioventricular nodal (AVN) conduction without suppressing 1:1 transmission. After opening the right atrium, RF was delivered (0.5 W) with a 1‐mm diameter unipolar electrode positioned in the selected zone until a prolongation of no less than 15% was obtained in the Wenckebach cycle length (WCL). Before and after (30 min) RF, anterograde and retrograde AVN refractoriness and conduction were evaluated, stimulating from the crista terminalis (CT), the interatrial septum (IAS), and from the RV epicardium. After RF, the fallowing percentage increments were observed in group I: AH(CT) = 36%± 9%, AH(IAS) = 38%± 11%, WCL(CT) = 28%± 8%, WCUIAS) = 22%± 6%. functional refractory period (FRP) of the AVN(CT) = 13%±11%, FRP‐AVN(IAS) = 13%± 8%, retrograde WCL = 20%±19%. and retrograde FRPVA = 13%± 16%. The increments observed in group II and the significances of the differences with respect to group I were: AH(CT) = 11%± 14% (P < 0.01), AH(IAS) = 19%± 32% (NS), WCL(CT) = 42%± 14% (P < 0.05), WCL(IAS) = 42%± 16% (P<0.01), FRP‐AVN(CT) = 28%± 28% (NS). FRP‐AVN(IAS) = 21 %± 19% (NS), retrograde WCL = 35%± 24% (NS), and retrograde FRP = 16%± 13% (NS). In both groups, the AH interval variations were not correlated with those of the rest of the parameters analyzed. Truncated nodal function curves suggestive of a dual A V nodal path way were obtained in three experiments, though in only one of them was this observed under basal conditions. In the other two experiments with dual AV nodal physiology only after RF (one from each group), AV nodal reentrant tachycardias were triggered with atrial extrastimulus at coupling intervals equal to or shorter than at those that cause a sudden lengthening of the AH interval. RF delivered in the anterior and posterior zones of the Koch triangle produced effects of different magnitude on the AH interval and Wenckebach cycle length. In the anterior zone the AH interval was prolonged to a greater extent, while in the posterior zone the effects were greater on the Wenckebach cycle length. No correlation existed between the variations in AH interval and Wenckebach cycle length, regardless of where RF was delivered. The evaluation of anterograde AV nodal refractoriness was similar when stimulating from the crista terminalis or from the interatrial septum. By delivering RF, it was possible to induce dual AV nodal physiology and reentrant tachycardias. (PACE 1997; 20[Pt. I]:1261‐1273]
Ambulatory Electrocardiography for the Detection of Pacemaker Lead Failure
Authors: GILLIS ANNE M. , HILLIER KAREN R. , ROTHSCHILD JOHN M. , MCDONALD MARGOT , SIMPSON CLIFFORD A. , WYSE D. GEORCE , FAUCHON BEVERLEY J.
Published: July 2006

The suboptimal performance of some polyurethane bipolar pacing leads has highlighted concern about the optimal method of monitoring pacemaker lead performance. Since the manifestations of premature lead failure may be initially intermittent, we hypothesized that ambulatory electrocardiography (AECG) would be a more sensitive tool for the detection of pacing lead failure compared to increased pacemaker clinic surveillance. Since the Medtronic safety alerts on the 4012, 4082, and 4004 leads, we have followed 261 patients by serial AECG and 165 patients by increased pacemaker clinic surveillance. Lead failures were identified in 75 patients: 68 in the AECG group (31 %) and 7 in the clinic group (4%, P < 0.001). Repeat AECG confirmed the lead failure in 38 (97%) of 39 patients in which it could be done. Pacing lead failure documented by AECG could be confirmed by a subsequent clinic assessment in only 15 (25%) of 60 patients evaluated (P < 0.001). The actuarial survival of the 4012 lead was significantly lower in the AECG group compared to the clinic group (56% vs 87% survival at 8 years, P < 0.002). Similar trends were observed for the 4082 and 4004 leads. AECG is a more sensitive method of surveillance for pacemaker lead function compared to pacemaker clinic assessment. AECG should be incorporated into the routine follow‐up of pacemaker patients. (PAGE 1997; 20[Pt. I]:127 4‐1282)
An Up‐Down Bayesian, Defibrillation Efficacy Estimator
Authors: COMPOS ALIKI T. , MALKIN ROBERT A. , IDEKER RAYMOND E.
Published: July 2006

In both the clinic and the laboratory, efficacy estimators are used to estimate the shock strength required to achieve a given defibrillation success rate. In the clinic, efficacy estimators are used to estimate highly effective doses (i.e., the shock strength that defibrillates 95% of the time), in order to choose the setting for an ICD. Efficacy estimators are used in the laboratory to compare defibrillation techniques and configurations. Current efficacy estimators are inadequate because they are either difficult to use, can only estimate the shock strength that defibrillates 50% of the time, or do not yield desirable accuracy (low RMS error). This article presents a Bayesian estimation technique that forces the difference between successive test shock strengths (step‐size) to be a fixed value after each measurement. Constraining the difference dramatically reduces the computational complexity of the up‐down Bayesian method. This new, up‐down Bayesian protocol can be used with up to 15 measurements to estimate the shock strength for any given success rate. Simulations show that the added constraint (fixed step‐size) only slightly increases the rms error, as compared to the optimum Bayesian protocol. Our simulations also show that protocols can be generated for shock strengths rounded to the nearest 1, 10, or 50 V, without a great increase in RMS error. Experimental results from a subset of all the simulations are reported from six animals, showing a < ‐2.4% difference between the simulated and measured errors. (PACE 1997; 20[Pt. I]:1292‐1300)
Dual Sensor Pacemakers in Children: What is the Choice of Sensor Blending?
Authors: ÇELIKER ALPAY , TOKEL KÜRŞAD , LENK M. KORAY , ÖZME ŞENCAN
Published: July 2006

Dual sensor pacemakers were developed to obtain more appropriate responses to activity. We evaluated ten children with dual sensor pacemakers in different sensor blending circumstances using exercise testing to assess which ratio was optimal. Ten patients with several bradydysrhythmias (ages 6‐16 years; mean 10.1 years) were included in the study. Eight patients had WIR pacemakers (Vitatron Topaz), models and two patients had VDD pacemakers implanted via the transvenous route. All patients were in a paced rhythm (98.5% pacing). Accurate T wave sensing ranged from 81%‐100%; mean 92%, median 95%. Voluntary exercise testing with a CAEP protocol was performed using a treadmill with the pacemaker in WIR mode. Medium activity threshold with three sensor blending ratios (QT = ACT, QT > ACT, and QT < ACT) were done in all patients. The mean duration of exercise was not statistically different among the three sensor blending ratios. After 90 seconds of exercise, the mean pacing rate had increased by 12%, 3%, and 5%, respectively, in the three groups. At maximal exercise, the increases were 45%, 42%, and 54%. Mean HRs during exercise in each of the three ratios were not significantly different, although we found a statistically significant increase in HR during the first two stages of rest period in the QT = ACT sensor blending ratio compared to the QT > ACT ratio. No difference was observed after the second stage. In conclusion: (1) there is no difference between the QT = ACT, QT < ACT, and QT > ACT sensor blending ratios; and (2) each child has to be evaluated by exercise testing to program a correct sensor blending ratio. (PACE 1997; 20[Pt. I]:1301‐1304)
Inappropriate Management of Self‐Terminating Ventricular Arrhythmias by Implantable Cardioverter Defibrillators Despite a Specific Reconfirmation Algorithm: A Report of Two Cases
Authors: HURST TANJA M. , KRIEGLSTEIN HOLGER , TILLMANNS HARALD , WALDECKER BERND
Published: July 2006

Algorithms that attempt to reconfirm the presence of an arrhythmia prior to definite treatment have been implemented in ICDs to prevent inappropriate shock therapy due to self‐terminating ventricular arrhythmias. Nevertheless, in two patients, clinically inappropriate shocks were delivered after spontaneous conversion of the arrhythmia despite the use of a specific reconfirmation algorithm. Reconfirmation criteria were met due to a premature ventricular complex causing a short cycle in the first patient and a long postextrasystolic pause in the second patient. To avoid inappropriate shock therapy due to self‐terminating ventricular arrhythmias, further improvement of detection algorithms is required. (PACE 1997; 20[Pt. I]:1328‐1331)
Autonomic Nervous System Activity During Tilt Testing in Syncopal Patients, Estimated by Power Spectral Analysis of Heart Rate Variability
Authors: KOCHIADAKIS GEORGE E. , ORFANAKIS ALEXANDROS , CHRYSSOSTOMAKIS STAVROS I. , MANIOS EMMANUIL G. , KOUNALI DAPHNE K. , VARDAS PANOS E.
Published: July 2006

Spectral analysis of heart rate variability (HRV) was used to assess changes in autonomic function before and during postural tilt in 28 syncopal patients: 14 (group A) with positive and 14 (group B) with negative tilting test, and 14 normal controls (group C). Frequency‐domain measurements of the high (HF) and low (LF) frequency bands and the ratio LF/HF were derived from Holter recordings, computed by Fast Fourier analysis for 4‐minute intervals immediately before tilt testing, immediately after tilting, and just before the end of the test. In group A, the mean values of LF and HF decreased slightly in response to tilting while the LF/HF ratio increased, though these changes were not statistically significant. All parameters showed a statistically significant increase just before the onset of syncope. In group B, there were no significant changes in the parameters measured throughout the test. In group C. there was an increase in the LF and LF/HF ratio and a decrease in the HF immediately after tilting. There were no further significant changes in any of the parameters during the test. Syncopal patients have a different pattern of response to the orthostatic stimulus, in that they do not show the increase in sympathetic tone observed in normal individuals immediately after tilting. In the patients with a positive tilt test, there is a shift in the balance of ANS activity towards the sympathetic system shortly before the onset of syncope. (PACE 1997; 20[Pt. I]:1332‐1341)
Dissimilar Right Atrial Rhythms: A Case Report
Authors: BHAGWAT AJIT R. , MARKEL MICHAEL L. , ABDALLA ISMAILE S.
Published: July 2006

Dissimilar atrial rhythms are generally defined by the coexistence of atrial fibrillation in one atrium and a more regular rhythm in the other atrium, and are reported with left atrial enlargement and/or digitalis toxicity. We report a unique case of dissimilar atrial rhythms controlling two different parts of the same atrium without interfering with one another. The mechanism of the dissociation of two foci is not clear; however, scarring due to previous surgery remains a possibility. (PACE 1997; 20[Pt. I]:1363‐1364)
Accidental Atrial and Ventricular Stimulation by Pacemaker Event Marker
Authors: BÖHM ÁDÁM , PINTER ARNOLD , PRÉDA ISTVÁN
Published: July 2006

A case of both atrial and ventricular stimulation by the sense event marker during external chest wall stimulation of a DDDR pacemaker is reported. This unusual phenomenon might produce pacemaker‐mediated tachycardia.
VDDR Pacing after His‐Bundle Ablation for Paroxysmal Atrial Fibrillation: A Pilot Study
Authors: BUYS EUGENE M. , Van HEMEL NORBERT M. , JESSURUN EMILE R. , KELDER JOHANNES C. , BAKEMA LEX , KINGMA J. HERRE
Published: July 2006

His‐bundle ablation followed by pacemaker implantation is today a widely accepted therapeutic choice when drug refractoriness of symptomatic AF is evident. The selection of pacing mode in patients suffering from paroxysmal AF is still controversial. Preservation of AV synchrony is an attractive option in patients with paroxysmal AF who undergo His‐bundle ablation. The purpose of this study was to examine prospectively the contribution of VDDR pacing for preservation of AV synchrony. After His‐bundle ablation a VDDR pacing system was implanted in 17 patients with paroxysmal AF, and all antiarrhythmic drugs were withdrawn. The endpoint of the study was defined as the onset of chronic AF. To document the onset of chronic AF 48‐hour Holter recordings were made every 6–8 weeks. After a mean followup of 18.2 (range 14–21) months, VDDR pacing is still operative in 13 patients (77%). Four patients developed chronic AF after a mean follow‐up of 6 months. Of several baseline characteristics, only the intraatrial P wave at implantation was significantly smaller in patients developing chronic AF than in patients in whom the VDDR mode is still operative. This pilot study suggests that VDDR pacing is an attractive pacing method for patients with paroxysmal AF after His‐bundle ablation. A low intraatrial P wave electrogram at implant was associated with a higher risk for the development of chronic AF.
Reliability of an Automatic Sensing Test with Beat‐to‐Beat Display of the Signal Amplitude
Authors: LAZARUS ARNAUD , CAZEAU SERGE , RITTER PHILIPPE , GRAS DANIEL , MUGIGA JAGQUES
Published: July 2006

In contrast to testing of the capture threshold, the reliability of sensing tests has been little studied. This study was performed to test the automatic sensing algorithm included in the Biotronik pacing systems. The automatic measurements made by the devices were compared with the direct manual measurements made of 271 atrial (72%) or ventricular (28%) electrograms recorded in ten patients. A high correlation(r = 0.995, P < 0.0001) was found between the two types of measurements. The use of this function should facilitate the verification of accurate sensing during the long‐term follow‐up of pacemaker patients, and offers a tool to analyze the variations in amplitude of intracardiac signals.
Radiofrequency Catheter Ablation of Septal Accessory Pathways within the Triangle of Koch: Importance of Energy Titration Testing Other than the Local Electrogram Characteristics for Identifying the Successful Target Site
Authors: LIN JIUNN‐LEE , HUANG SHOEI K. STEPHEN , LAI LING‐PING , CHENG TING‐FU , TSENG YUNG‐ZU , LIEN WEN‐PIN
Published: July 2006

Radiofrequency (RF) catheter ablation of accessory atrioventricular (AV) connections in the proximity of His bundle or AV node is at high risk of developing complete heart block. A safe and effective protocol has not been well established. Nineteen consecutive patients with 19 septal accessory pathways within the triangle of Koch underwent a protocol with power‐titrated RF energy testing to identify the target site for successful catheter ablation. At every potential target site preselected by local electrogram characteristics, RF energy was started at 5 W for 10 seconds, with an increment of 5 W (duration remained at 10 s) until maximally 30 W or the observation of transient interruption of accessory pathway conduction. By this stepwise RF energy testing, we successfully localized and ablated 18 (94.7%) of the 19 septal accessory pathways, 10 close to His bundle (zone I) and 8 away from it (zone II). The test‐effective RF power was 20 W or less in 9 of all 11 septal accessory pathways in zone I, and 5 of the 8 in zone II (P = 0.68). Meanwhile, the final RF power for successful ablation was 30 W or less in 9 of the 10 zone I and 6 of the 8 zone II septal accessory pathways (P = 0.83). One patient with an accessory pathway in zone I was complicated with complete AV block after final ablation at 30 W. None of the local electrogram characteristics except continuous electrical activity during retrograde mapping was helpful in the prediction of ablation outcome. Careful RF energy titration testing could effectively help identify the target site for successful RF catheter ablation of septal accessory pathways within the triangle of Koch. The dependence on local electrogram manifestations could be frustrated by a low probability of success.
Comparison of Arrhythmogenicity of Atrial Pacing at Several Right Atrial Pacing Sites: Evaluation of Canine Atrial Electrograms During Atrial Pacing and Arrhythmogenicity for Atrial Fibrillation
Authors: NIWANO SHINICHI , YAMAURA MASAYUKI , WASHIZUKA TAKASHI , TANABE YASUTAKA , FURUSHIMA HIROSHI , TANEDA KOJI , AIZAWA YOSHIFUSA
Published: July 2006

The changes in the duration of atrial electrograms and the appearance of AF during atrial pacing were compared among five atrial pacing sites in dogs to clarify the arrhythmogenicity of atrial pacing at different atrial pacing sites. In seven mongrel dogs (15–20 kg), the right atrial surface was exposed by right thoracotomy. Atrial electrograms were recorded via bipolar electrodes with an interelectrode distance of 1.2 mm at four right atrial sites: (1) the high right atrium (HRA), (2) the mid‐right atrium (MRA), (3) the low right atrium (LRA), and (4) the center of the pectinate muscle (PM). The duration of the atrial electrograms at these four recording sites were measured during atrial pacing with fixed cycle lengths of 200, 150, and 120 ms delivered at five atrial sites: (1) the HRA, (2) the inferior vena cava (IVC), (3) the right atrial appendage (RAA), (4) Bachman's bundle (BB), and (5) the atrial septum (AS). In each dog, the atrial pacing with the 120‐ms cycle length was performed five times at each pacing site to evaluate the in‐ducibility of AF. When AF was induced, the atrial recording site which first showed a fragmented atrial electrogram was considered the initiation site of the AF. AF was induced during 9 of 35 episodes of atrial pacing at the HRA site, 11 of 35 at the IVC site, 5 of 35 at the RAA site. 3 of 35 at the BB site, and none at the AS site. The initiation site of AF was in the HRA site in 11 of 28 episodes of induced AF, in the MRA site in 9 of 28, and in the LRA site in 8 of 28. At each recording site, the shorter the paced cycle length, the longer the duration of the atrial electrogram regardless of the pacing site. During the atrial pacing with the 200‐ms cycle length, the HRA pacing resulted in the shortest duration of the atrial electrogram at each recording site in comparison with the other pacing sites. However, during atrial pacing at the two shorter paced cycle lengths, the duration of the atrial electrogram was shorter during the pacing at the BB or AS sites in comparison with the other three pacing sites, i.e., the HRA, IVC, and RAA sites. These results were the same for all atrial recording sites, but the prolongation of the atrial electrogram was most prominent at the HRA and MRA recording sites, which are most likely initiation sites of the induced AF. In the canine atria, (1) the initiation sites of AF were likely to be the HRA, MRA, or LRA sites in comparison with the PM site; and (2) the atrial pacing at the BB or AS sites was considered less arrhythmogenic for AF than the pacing at the HRA, LRA, or RAA sites.
Magnetocardiographic QT Interval Dispersion in Postmyocardial Infarction Patients with Sustained Ventricular Tachycardia: Validation of Automated QT Measurements
Authors: OIKARINEN LASSE , PAAVOLA MIKA , MONTONEN JUHA , VIITASALO MATTI , MÄKIJÄRVI MARKKU , TOIVONEN LAURI , KATILA TOIVO
Published: July 2006

T dispersion is a measure of heterogeneity in ventricular repolarization. Increased ECG QT dispersion is associated with life‐threatening ventricular arrhythmias. We studied if magnetocardiographic (MCG) measures of QT dispersion can separate postmyocardial infarction patients with and without susceptibility to sustained VT. Manual dispersion measurements were compared to a newly adapted automatic QT interval analysis method. Ten patients with a history of sustained VT (VT group) and eight patients without ventricular arrhythmias (Controls) were studied after a remote myocardial infarction. Single‐channel MCGs were recorded from 42 locations over the frontal chest area and the signals were averaged. QT dispersion was defined as maximum — minimum or standard deviation of measured QT intervals. VT group showed significantly more QT and JT dispersion than Controls. QTapex dispersions were 127 ± 26 versus 83 ± 21 ms (P = 0.004) and QTend dispersions 130 ± 37 versus 82 ± 37 ms (P = 0.013), respectively. Automatic method gave comparable values. Their relative differences were 9% for QTapex and 27% for QTend dispersion on average. In conclusion, increased MCG QT interval dispersion seems to be associated with a susceptibility to VT in postmyocardial infarction patients. MCG mapping with automated QT interval analysis may provide a user independent method to detect nonhomogeneity in ventricular repolarization.
Atrial Vulnerability in Patients with Paroxysmal “Lone” Atrial Fibrillation
Authors: ZIMMERMANN MARC , ADAMEC RICHARD , METZGER JACQUES
Published: July 2006

Little is known about the electrophysiological properties of the atrium predisposing to paroxysmal atrial fibrillation (AF), especially in patients without structural heart disease. This study was conducted to analyze intraatrial conduction, atrial refractoriness, and arrhythmia inducibility in patients with lone paroxysmal AF. An electrophysiological study was performed in 24 patients with a documented history of lone paroxysmal AF but in sinus rhythm at the time of the electrophysiological study. Twelve patients without any history of atrial arrhythmias served as controls. The patients with lone paroxysmal AF showed a significant prolonged local conduction time S1A1 (70 ± 21 ms vs 36 ± 12 ms, P < 0.0001), a lack of rate adaptation of the functional refractory period (FRP changes/cycle length changes < 10% in 15 of 24 patients with lone paroxysmal AF vs 1/12 controls, P = 0.002) and a higher incidence of inducible AF with only one extrastimulus (13/24 vs 0/12, P = 0.0014). The total P wave duration in the surface ECG (89 ± 14 ms vs 83 ± 8 ms, P = 0.15), the intraatrial conduction time (36 ± 14 ms vs 28 ± 8 ms, P = 0.07), the presence of a fragmented atrial electrogram (16/24 vs 7/12, P = 0.62), the absolute value of the effective refractory period (204 ± 28 ms vs 212 ± 23 ms, P = 0.42), and the vulnerability index (3.0 ± 1.5 vs 3.6 ± 1.5, P = 0.26) were not statistically different between the two groups. The presence of a prolonged (> 50 ms) S1A1 and/or the presence of a lack of rate adaptation of the FRP and/or the presence of inducible AF identified patients with spontaneous lone paroxysmal AF with a sensitivity of 96%, a specificity of 67%, a positive predictive value of 85%, and a negative predictive value of 89%. In patients with lone paroxysmal AF. the electrophysiological study using conventional techniques allows not only to detect AF inducibility using a nonaggressive protocol, but also to reveal several electrophysiological abnormalities related to the atrial substrate itself. This atrial vulnerability may explain the high incidence of recurrences in patients with lone paroxysmal AF.
Anatomy‐Guided Linear Atrial Lesions for Radiofrequency Catheter Ablation of Atrial Fibrillation
Authors: SCHWARTZMAN DAVID , KUCK KARL‐HEINZ
Published: July 2006

The surgical atrial maze procedure has provided proof that atrial fibrillation can be cured by performing atrial incisions based on anatomical and electrophysiological principles. Preliminary reports of attempts at radio frequency catheter ablation of atrial fibrillation utilizing an anatomy‐based “linear incision” method have shown the feasibility of the method. However, postprocedural atrial fibrillation recurrence has been common and in addition new, uniform tachycardias have developed in some patients. Both of these outcomes may be in part due to incomplete or inconsistent lesion deployment. This article details the use of the CARTO system for deploying anatomy guided linear atrial lesions for the purpose of curing atrial fibrillation. The procedure is comprised of three phases, which are discussed in detail: (1) baseline map: (2) lesion deployment and; (3) lesion assessment. Using a single standard ablation electrode, lesions can be deployed safely, and complete lesions can be confirmed. Paradigms for right and left atrial incisions are proposed.
Pharmacological Stress Testing of the His‐Purkinje System in Patients with Bifascicular Block
Authors: ENCLUND ANDERS , BERGFELDT LENNART , ROSENQVIST MÅRTEN
Published: July 2006

This literature review, based mainly on the English‐language literature, focuses on pharmacological stress testing of the His‐Purkinje system as part of an invasive, electrophysiological study. The main target group for this investigation is patients with bifascicular block and syncope in which intermittent high grade AV block is suspected. Several drugs have been used for this purpose, mainly Class I antiairhythmic agents such as ajmalina, procainamide, disopyramide, and flecainide. Most studies, unfortunately, suffer from limited patient numbers, lack of adequate control groups, and/or adequate follow‐up. The sensitivity of the disopyramide stress test has been shown to be 75%–100% for prediction of impending high grade AV block. The specificity was > 90%. Studies on procainamide have shown a sensitivity of 60% but the specificity has not been assessed. There are no studies allowing a strict comparison of the diagnostic value of pharmacological provocation with different drugs. Based on the similarities of the electrophysiological effects on the His‐Purkinje system of the above Class I agents, it is reasonable to assume that all of them might be of diagnostic value in the present clinical context, provided atrial and ventricular stimulation after drug is included in the protocol.
Pacemaker‐Mediated Polymorphic Ventricular Tachycardia
Authors: GOLDMAN DANIEL S. , LEVINE PAUL A.
Published: July 2006

A patient with refractory bradycardia dependent polymorphic ventricular tachycardia (PMVT) underwent permanent pacemaker placement for suppression of her arrhythmia. Following implant, the patient had recurrent PMVT. Interrogation of the device revealed a factory programmed feature (+ PVARP on PVC) designed to prevent pacemaker‐mediated tachycardia that led to cycle length variability and subsequent arrhythmia recurrence. This feature was deactivated and the patient's arrhythmia did not recur.
Electromagnetic Interference from a Muscle Stimulation Device Causing Discharge of an Implantable Cardioverter Defibrillator: Epicardial Bipolar and Endocardial Bipolar Sensing Circuits Are Compared
Authors: GLOTZER TAYA V. , GORDON MARGARET , SPARTA MARK , RADOSLOVICH GLAUCO , ZIMMERMAN JOHN
Published: July 2006

This case report is about two patients with two different types of ICDs who underwent electrical muscle stimulation (EMS) therapy. In one patient with an ICD that has epicardial screw‐in bipolar sensing leads, electromagnetic interference (EMI) from the EMS device caused the delivery of an inappropriate ICD discharge. In a second patient with an ICD with endocardial true bipolar sensing, there was no evidence of EMI during the EMS therapy despite all of our attempts to reproduce it. The sensing circuits in the two different ICDs are compared.
Use of Atrial and Ventricular Electrograms from a Dual Chamber Implantable Cardioverter Defibrillator to Elucidate a Complex Dysrhythmia
Authors: GREENBERG RICHARD M. , DEGERATU FLORIN T.
Published: July 2006

Stored intracardiac electrograms provided by third‐generation ICDs have proved their use in the analysis of the mechanism of tachydysrhythmic events. There are cases in which the analysis of ventricular electrograms is insufficient for the elucidation of certain dysrhythmias. The availability of atrial electrograms provided by dual chamber ICDs improves the diagnostic capability of electrogram analysis and could prove most useful especially in complex dysrhythmias.
Concealed Mechanical Bradycardia: An Indication for Permanent Pacemaker Implantation
Authors: HAROLD HELEN S. , HESSELSON AARON B. , JOLLIS JAMES , WHARTON J. MARCUS , BAHNSON TRISTRAM D.
Published: July 2006

We report a 51‐year‐old man with severe ischemia cardiomyopathy and heart failure in whom incessant bigeminal ventricular ectopy failed to generate a detectable arterial pressure. This created a mechanical bradycardia despite an adequate electrical heart rate. Dual chamber pacing increased the effective heart rate and allowed discontinuation of an intraaortic balloon pump from which the patient could not otherwise be weaned.
Inappropriate Shocks Delivered by an ICD as a Result of Sensed Potentials from a Transcutaneous Electronic Nerve Stimulation Unit
Authors: PHILBIN DANIEL M. , MARIEB MARK A. , AITHAL KESHAVA H. , SCHOENFELD MARK H.
Published: July 2006

Although the potential for transcutaneous electronic nerve stimulation (TENS) units to interfere with appropriate function of cardiac pacemakers is well documented, an adverse interaction between a TENS unit and an ICD has never been reported. We describe a patient in whom a TENS unit created an electrical artifact that was interpreted by a transvenous ICD as ventricular fibrillation, leading to the delivery of inappropriate therapy. TENS units should be used with caution in patients with ICDs.
The Safety of Reusing Ablation Catheters with Temperature Control and the Need for a Validation Protocol and Guidelines for Reprocessing
Authors: BLOMSTRÖM‐LUNDQVIST CARINA
Published: July 2006

The objective of this study was to evaluate the safety of reusing ablation catheters with temperature control, which has not previously been reported. A review of previously conducted studies on the feasibility of reusing electrode catheters is also presented. From September 1994 to December 1997, 74 deflectable ablation catheters with temperature control (Cordis‐Websters and Osypkas) were used during mean 7.6 ± 8.0 ablation sessions. The catheter tests included visual inspection for surface defects using a magnification glass, impedance measurements, evaluation of the catheter deflection capability, and the integrity of the thermistor and thermocouple. The catheters were sterilized by Sterrad(tm) after each use. A total of 41 catheters were rejected after an average 9.1 ± 8.8 uses (range 1–31). The main reasons for rejection were inaccurate temperature measurements by the thermistor or thermocouple (19 %), breakage of or defect in the internal pulling wire (12%), loss or disturbance of electrogram (9%), and loss of deflection capability (8%). The reuse of the catheters has not resulted in any major catheter failures or any major adverse clinical complications. There were no local or systemic infections. It can be concluded that these types of ablation catheters will sustain repeated uses and resterilizations without untoward harm to the patient provided that a thorough validation protocol and guidelines for quality control and rejection of catheters are used. There seems to be no rational for setting a limit for the number of reuses, since most failures occurred at any time of reuse.