bluuebunny/crossref_metadata_2025 huggingface dataset:
Koch's Triangle Sized Up: Anatomical Landmarks in Perspective of Catheter Ablation Procedures
Authors: INOUE SHIN , BECKER ANTON E.
Published: July 2006

Koch's triangle contains the compact part of the atrioventricular node and is anatomically delineated by the Eustachian ridge, the membranous septum, and the insertion of the tricuspid valve. In‐feriorly, Koch's triangle ends at the site of the OS of the coronary sinus and, in part, is continuous with the sub‐Eustachian pouch. Catheter ablation procedures for several types of reentrant tachycardias are based on identifying these anatomical landmarks. Variability in the dimensions of Koch's triangle thus may be clinically relevant. We examined 50 hearts. Anatomical landmarks measured were the Eustachian ridge, the tricuspid valve, the overall length between the membranous septum and the coronary sinus, the width of the coronary sinus, the Eustachian ridge in its roof and the distance to the tricuspid valve, and that of the sub‐Eustachian pouch. Individual variations were marked. The mean values (± SD) were: Eustachian ridge 29.4 ± 5.3 mm. tricuspid valve 28.9 ± 4.5 mm, coronary sinus 10.8 ± 2.2 mm, Eustachian ridge 3.7 ± 2.3 mm, space underneath coronary sinus 8.6 ± 3.4 mm, and sub‐Eustachian pouch 26.8 ± 3.3 mm. The overall length varied between 15 and 38 mm, with a mean of 26.3 ± 4.5. In conclusion, Koch's triangle shows considerable individual variations in size. Given the fact that the absolute figures for the range in size of the compact atrioventricular node is much less than that of Koch's triangle, these variations have implications for catheter ablation procedures.
QRS Duration Widening: Reduced Synchronization of Endocardial Activation or Transseptal Conduction Time?
Authors: MEHDIRAD ALI A. , NELSON STEVEN D. , LOVE CHARLES J. , SCHAAL STEPHEN F. , TCHOU PATRICK J.
Published: July 2006

Antegrade activation of the His‐Purkinje system (HPS) results in synchronized activation of the right ventricular (RV) and left ventricular (LV) endocardia forming normal, narrow QRS duration (QRSD). An alteration in septal activation and transseptal conduction time have been reported to be the causes for QRSD widening seen with bundle branch block. However, reduced synchronization of activation ofRVand LV endocardia as another potential mechanism for QRSD widening has not been systematically studied. Fifteen consecutive patients underwent radiofrequency ablation (RFA) for treatment of supraventricular tachycardia. After RFA, mean QRSD in normal sinus rhythm was 86 ± 8 ms with mean HV interval of 40 ± 5 ms. Right atrial (RA), coronary sinus (CS), simultaneous (S) RA‐CS, RVapex (RVA), LV apex (LVA), and SRVA‐LVA pacing were performed. Mean QRSD with RA, CS, SRA‐CS pacing was similar to normal sinus rhythm (87 ± 7, 87 ± 8 and 88 ± 8 ms respectively). Mean QRSD was significantly longer with SRVA‐LVA and either RVA or LVA pacing alone compared to normal sinus rhythm (106 t 8, 146 ± 12 and 157 ± 13 ms, respectively). However, QRSD was significantly shorter with SRVA‐LVA pacing compared to either RVA or LVA pacing alone (P < 0.0001). We conclude that shorter QRSD with SRVA‐LVA pacing compared to either RVA or LVA pacing alone is due to elimination of transseptal conduction delay; longer QRSD with SRVA‐LVA pacing compared to sinus or atrial paced rhythm is due to reduced synchronization of endocardial activation secondary to ectopic entry of impulses into the HPS network and inability to take advantage of the branching structure of the HPS. Therefore, in addition to transseptal conduction delay, reduced synchronization of endocardial activation is another potential mechanism for QRSD widening.
Human Precision of Operating a Digitizing Board: Implications for Electrocardiogram Measurements
Authors: MALIK MAREK , BRADFORD ANNE
Published: July 2006

To investigate the precision achieved by human measurement on a digitizing board, 100 healthy volunteers (46 women, mean age 36 ± 12 years) were asked to measure 15 times an artificial pattern composed of 15 points. A high precision digitizing board (programmed to the technical accuracy of ± 50 μm) was used, and mean and maximum errors in measuring the same distance repeatedly and re‐localizing the same point repeatedly were obtained for each volunteer. A median mean and maximum error of 0.2 mm and 1.0 mm were found for repeated distance measurement. When simulating QT dispersion measurement (measuring the same distance 12 times), median value of 20 ms was obtained for ECGs of 25 mm/s paper speed. The study concludes that human precision of operating a digitizing board is rather poor. A recommendation is given to use either a computer screen for manual measurement of ECGs or to provide an operator of the digitizing board with an immediate feedback of the precision and measurement stability achieved so that erroneous measurement can be actively rejected.
Extensive Variation in the Signal Amplitude of the Atrial Floating VDD Pacing Electrode
Authors: SUN ZHI‐HONG , STJERNVALL JOACHIM , LAINE PETRI , TOIVGNEN LAURI
Published: July 2006

The dependence of atrial signal amplitude on the site of the ntrial sensing dipole of a single‐pass lead was examined in 29 patients. The vertical location of the dipole was documented in supine fluo‐roscopy during quiescent and deep breathing and in upright chest roentgenogram, and was expressed as a proportion of the, right atrial height. As the group average, the atrial signal amplitude was equal when tested in supine, sitting, standing, and right‐ or left‐side positions in follow‐up determinations. The signal amplitude varied markedly between postures, showing a coefficient of variation of 45%± 24% within the group. Coefficient of variation within the 6‐month fallow‐up period in each tested position ranged from 31%−4 4%, Correlation between postures was weak (range of r = 0.53–0.81). Vertical location of the atrial dipole had no relationship to the signal amplitude. At least in one posture or test occasion the atrial signal amplitude was very low, ≤ 0.35 mV in 20 patients, and below detection limit (0.25 mV) in 5 patients. Programmed to high sensitivity, atrial undersensing was rare in ambulatory electrocardiography, ranging from 0–9,000 missed atrial beats (0%–8%), with a median of 100 beats/24 hours. In conclusion, temporary variation in atrial signal amplitude is extensive. Despite occasionally measured large signal amplitudes atrial sensitivity in single lead VDD pacemakers should be programmed high, and if poor atrial tracking is suspected, other methods besides routine sensitivity testing should be adapted.
Pacing in Distal Left Ventricular Hypertrophic Cardiomyopathy
Authors: HINTRINGER FLORIAN , NESSER HANS‐JOACHIM , NIEL JOHANNES , BAUMGARTNER GERTRAUD , AICHINGER JOSEF
Published: July 2006

We report the case of an 85‐year‐old woman with distal LV hypertrophy resulting in an intraventricular pressure gradient and incomplete systolic emptying who benefited from permanent DDD pacing. Our experience based on this case suggests that permanent dual chamber pacing might be a safe and effective therapy also in symptomatic patients with the rare form of hypertrophic cardiomyopathy with left mid‐ventricular obstruction resulting in incomplete emptying of the apical portion of the LV and a significant intraventricu‐ lar pressure gradient that was not responding to pharmacological therapy.
Unusual Features of Right and Left Idiopathic Ventricular Tachycardia Aholished hy Radiofrequency Catheter Ablation
Authors: CHILADAKIS JOHN A. , VASSILIKOS VASSILIS , MAOUNIS THEMOS , COKKINOS DENNIS V. , MANOLIS ANTONIS S.
Published: July 2006

Two unusual cases are presented with idiopathic right and left ventricular tachycardia(IVT) with intriguing clinical and electrophysiological characteristics. The first patient with a sustained IVT of right ventricular outflow tract origin, and an electrophysiological mechanism suggesting reentry, had been resuscitated from cardiac arrest. The second patient had an IVT with a left bundle branch block morphology, which originated from the basal‐septal region of the left ventricle(left ventricular outflow tract tachycardia). Both patients were cured with radiofrequency catheter ablation, guided by endocardial activation sequence and pace mapping.
Catheter Ablation for Ventricular Tachycardia from a Diverticulum at the Right Ventricular Outflow Tract
Authors: YAMAUCHI YASUTERU , NOGAMI AKIHIKO , NAITO SHIGETO , TSUCHIO YASUHIRO , AONUMA KAZUTAKA , IESAKA YOSHITO , HIROE MICHIAKI
Published: July 2006

A case is presented of a 73‐year‐old man with drug resistant ventricular tachycardia that originated from the right ventricular outflow tract. A right ventriculogram showed a diverticulum in the interventricular septum at the right ventricular outflow tract. Low energy radiofrequency catheter ablation within the diverticulum was performed successfully and safely.
Electrophysiological Effects of Intrapericardial Infusion of Endothelin‐1
Authors: GELLÉR LÁSZLÓ , MERKELY BÉLA , SZOKODI ISTVÁN , SZABÓ TAMÁS , VECSEY TIBOR , JUHÁSZ‐NAGY ALEXANDER , TÓTH MIKLÓS , HORKAY FERENC
Published: July 2006

Recently, extremely high levels of endothelin‐1 (ET‐1) were detected in the pericardial fluid of patients undergoing open‐heart surgery. ET‐1 has been suggested to have direct arrhythmogenic effect on myocardium. The aim of the present study was to examine the putative arrhythmogenic effect of intrapericardial infusion of ET‐1 in anesthetized dogs (n=15).

In preliminary experiments, ET‐1 (0.125–1.0 nmol/min, n=7) was infused into the closed pericardial sack for 40 min. ET‐1 induced non‐sustained and/or sustained ventricular tachyarrhythmias in all but the lowest dose. For detailed arrhythmia analysis in addition to standard ECG ventricular endocardial and epicardial monophasic action potentials (MAP) were recorded. ET‐1 (0.250 nmol/min, n=7) induced mono‐ and polymorphic ventricular tachycardias, which (degenerated into ventricular fibrillation in two instances. Moderate if any ischemic signs could be detected before the onset of arrhythmias. The arrhythmias spontaneously disappeared in all instances with the exception when ventricular fibrillation terminated the experiment. QT interval (260±23ms vs. 317±31ms, P < 0.05), and endo‐ and epicardial MAPD90 (at 300 ms cycle length) prolonged significantly (in average 182±12ms vs. 224±25ms, P < 0.05). Using MAP recording afterdepolarizations were detected in three instances. In control animals (n=3) arrhythmias were not observed and all electrophysiological parameters remained unchanged.

The present results show that intrapericardial administration of ET‐1 can induce ventricular arrhythmias in dogs. The arrhythmogenic effect of ET‐1 may be based on prolongation of MAP duration and development of afterdepolarizations. However, the elucidation of the precise mechanism needs further investigation.
The Patient Alert System ‐ Pilot Study of Built‐in Warning Systems for Pacemakers
Authors: FAHRAEUS THOMAS , STOTTS LARRY , PRUTCHI DAVID , MAERTENS STEVEN , WOODSON DRURY , COOKE DANIEL
Published: July 2006

Malfunction of a pacing system can be life‐threatening for a pacemaker‐dependent patient. It would be desirable for implantable pulse generators to have a built‐in automatic warning system capable of alerting the patient m soon as a potentially dangerous disorder is detected. In this study, seven patients (mean age, 72.6 ± 10.7 years) with slow, chronic atrial fibrillation underwent implantation of a dual‐chamber pulse generator with a atstom‐made “alert electrode” connected to the atrial port of the pulse generator to stimulate the underlying pectoral muscle. The muscle was temporarily stimulated while the pacemaker was in VVIR mode. The lowest amplitude sufficient to alert the patient (perception threshold) was 1.6 ± 0.58 V at 0.45 ms during implantation and 1.2 ± 0.5 V at 0.45 ms chronically. In a second phase, alerts outside of the office were issued using a special software routine capable of delivering stimuli at programmable date and time.
Temperature Controlled RF Ablation in Canine Ventricle and Coronary Sinus using 7 Fr or 5 Fr Ablation Electrodes
Authors: MEHDIRAD ALI , GAISER JOHN , BAKER PETER , WEST SCOTT , LEHMKUHL LINDA , YONG PAT , MEIMER JOHN , NELSON STEVEN
Published: July 2006

The safety and lesion volume of temperature controlled radiofrequency ablation (TCRFA) in the right ventricle (RV), left ventricle (LV), and coronary sinus (CS) comparing long 5 Fr to standard tip electrodes have not been previously reported In 1O canines, TCRFA was delivered at a 70°C set point for 30 seconds. Lateral and septal RV lesions were made with either a 5 Fr/5 mm or 7 Fr/4 mm tip. Lateral and septal LV lesions were made with either a 5 Fr/7 mm or 7 Fr/4 mm tip. Proximal and distal CS lesions were made with either a 7 Fr/4 mm, 5 Fr/5 mm or 5 Fr/7 mm tip. Gross and histologic examination of the lesions was completed. Lesion size, tip temperature and power required are related to electrode surface area (SA) when ablating in the RV, LV or CS. 5 Fr/7 mm tips (SA = 36 mm2) tended to create larger lesions than 7 Fr/4 mm tips (SA = 29 mm2) in the LV. 7 Fr4 mm tips tended to create larger lesions than 5 Fr/5 mm tips (SA ‐ 26 mm2) in the RV. 7 Fr/4 mm LV lesions exceeded 7 Fr/4 mm RV lesions due to thicker LV walls. In the CS, 5 Fr/7 mm tips tended to create the largest lesions. In the RV, LV and CS, tips with larger SA tended to have lower temperatures and require higher power. No high temperature or high impedance shutdowns were observed. In conclusion, varying 5 Fr tip length can safely produce larger or smaller lesions compared to those created with 7 Fr/4 mm tips.
DDD Pacing with Rate Drop Response Function Versus DDI with Rate Hysteresis Pacing for Cardioinhibitory Vasovagal Syncope
Authors: AMMIRATI FABRIZIO , COLIVICCHI FURIO , TOSCANO SALVATORE , PANDOZI CLAUDIO , LAUDADIO MARIA TERESA , DE SETA FRANCESCO , SANTINI MASSIMO
Published: July 2006

Background: The effectiveness of cardiac pacing in preventing vasovagal syncope remains controversial. However, DDI pacing with rate hysteresis has been reported to prevent the recurrence of Cardioinhibitory vasovagal syncope in up to 35% of affected subjects and to reduce the overall incidence of syncopal episodes in the others. Recently, DDD pacing with a new promising rate drop response function (Medtronic Thera‐I model 7960) has become available in clinical practice. Aim of the study: The aim of the present open trial was to test the effectiveness of this new pacing modality in patients with Cardioinhibitory vasovagal syncope. Study population and methods: The study population included 20 patients (12 males and 8 females; mean age 61.1 ± 14 yrs) with recurrent syncope (mean number of prior episode = 6.8, range 5–11) and Cardioinhibitory responses during two head‐up tilt tests: the first diagnostic and the second during drug therapy with either β‐blockade or etilephrine. The study patients were randomized to receive either DDI pacing with rate hysteresis (8 patients) or DDD pacing with rate drop response function (11 patients). The head‐up tilt test performed 1 month after pacemaker implantation was positive in 3 of 12 patients (25%) with DDD pacing with rate drop response function and in 5 of 8 patients (62.5%) with DDI pacing with rate hysteresis. The mean duration of follow‐up was 17.7 ± 7.4 months. During follow‐up no patients with a DDD pacemaker with rate drop response function had syncope, while 3 of 8 patients with a DDI pacemaker with rate hysteresis had recurrence of syncope (P < 0.05). Conclusions: These data suggest that DDD pacing with rate drop response function is effective in Cardioinhibitory vasovagal syncope and may be preferable to DDI pacing with rate hysteresis.
Activity‐Controlled Circadian Base Rate
Authors: PARK EULJOON , WEILENMANN DANIEL , BLOCH KONRAD , KUEFFNER JOSEF , BORNZIN GENE , CANDINAS RETO , LEVINE PAUL A.
Published: July 2006

The current pacing rates are clustered around a fixed base rate since pacemaker patients are usually sedentary, resting, or sleeping most of the time. This fixed base rate is either too low for daytime hemodynamic support or too high for nighttime rest and recovery. Multiple Holter studies involving normal individuals have suggested that the resting base rate fluctuates during the course of the day. The circadian base rate (CBR) algorithm was designed to provide patients with a circadian change in paced resting rate and a normal rate distribution. The CBR algorithm, using a sophisticated accelerometer sensor, was developed and tested using the downloaded activity data from patients implanted with Trilogy DR+ pacemakers. Twenty‐five patients (19 men, 6 women, age 72 ± 9 years) were studied. Trilogy DR+ is able to record the detailed sensor and system behavior data for a week. During outpatient visits, the pacemaker was interrogated and the data accumulated in the pacemaker memory were downloaded. The CBR algorithm was applied to the activity variance histogram to calculate the base rate and to construct its histogram. The base rates in the CBR histogram are generally below 100 ppm with a distribution that mimics the natural sinus rate distribution of normal subjects. The CBR algorithm provides the highest daytime rates for hemodynamic support and the lowest nighttime rates for cardiac recovery, with a smoothly changing base rate modeling the normal circadian variation in heart rate.
Atrial Septal Pacing to Synchronize Atrial Depolarization in Patients with Delayed Interatrial Conduction
Authors: KATSIVAS APOSTOLOS , MANOLIS ATHANASIOS G. , LAZARIS EUSTATHIOS , VASSILOPOULOS CHARIS , LOUVROS NIKOLAOS
Published: July 2006

The current method of pacing the right atrium from the appendage or free wall is often the source of delayed intraatrial conduction and discoordinate left and right atrial mechanical function. Simultaneous activation of both atria with pacing techniques involving multisite and multilead systems is associated with suppression of supraventricular tachyarrhythmias and improved hemodynamics. In the present study we tested the hypothesis that pacing from a single site of the atrial septum can synchronize atrial depolarization. Five males and two females (mean age 58 ± 6 years) with drug refractory paroxysmal atrial fibrillation (AF) were studied who were candidates for AV junctional ablation. All patients had broad P waves (118 ± 10 ms) on the surface ECG. Multipolar catheters were inserted and the electrograms from the high right atrium (HRA) and proximal, middle, and distal coronary sinus (CS) were recorded. The atrial septum was paced from multiple sites. The site of atrial septum where the timing between HRA and distal CS (d‐CS) was ≤ 10 ms was considered the most suitable for simultaneous atrial activation. An active fixation atrial lead was positioned at this site and a standard lead was placed in the ventricle. The interatrial conduction time during sinus rhythm and AAT pacing and the conduction time from the pacing site to the HRA and d‐CS during septal pacing were measured. Atrial septal pacing was successful in all patients at sites superior to the CS os near the fossa ovalis. During septal pacing the P waves were inverted in the inferior leads with shortened duration from 118 ± 10 ms to 93 ± 7 ms (P < 0.001), and the conduction time from the pacing site to the HRA and d‐CS was 54.3 ± 6.8 ms and 52.8 ± 2.5 ms, respectively. The interatrial conduction time during AAT pacing was shortened in comparison to sinus rhythm (115 ± 18.9 ms vs 97.8 ± 10.3 ms, P < 0.05). In conclusion, simultaneous activation of both atria in patients with prolonged interatrial conduction time can be accomplished by pacing a single site in the atrial septum using a standard active fixation lead placed under electrophysiological study guidance. Such a pacing system allows proper left AV timing and may prove efficacious in preventing various supraventricular tachyarrhythmias.
Atrial Fibrillatory Electrogram Measurement Allows Atrial Lead Placement in Patients Who Develop Atrial Fibrillation During Permanent Dual Chamber Pacemaker Implantation
Authors: WOLFHARD ULRICH F. , EICHSTAEDT HARALD C. , SACK STEFAN , DAGRES NIKOLAOS , KNOCKS MICHAEL , SCHMID MICHAEL , SPLITTGERBER FRED H.
Published: July 2006

The benefit of DDD(R) pacing is proven even in patients with intermittent atrial fibrillation. Atrial fibrillation developing during dual chamber pacemaker implantation creates a difficult problem. Maneuvers to reestablish a stable atrial rhythm often are required if atrial fibrillation sets in. This study was performed to determine if atrial lead placement can be performed with acceptable long‐term results in the presence of atrial fibrillation. Twenty‐one patients in whom atrial fibrillation developed during permanent pacemaker implantation were included in this study. In 12 patients, episodes of intermittent atrial fibrillation had been documented before the procedure. Screw‐in leads were used in 15 patients and J‐shaped passive fixation leads in 6 patients. AH leads were bipolar. The intraoperative atrial fibrillation electrogram amplitudes ranged from 0.9 to 3.2 mV (mean 1.8 ± 0.6 mV). One patient required lead revision due to a high atrial pacing threshold after conversion to SR. One patient remained in atrial fibrillation at 3‐month follow‐up. The other 20 patients converted to SR, 11 of whom had intermittent atrial fibrillation with successful mode switch activation. P wave amplitudes were 2.8 ± 6 mV (range 1.4 to 4.0 mV) after conversion to SR. The mean atrial pacing threshold was 1.1 ± 0.5 V (range 0.5 to 3.5 V). Placement of atrial leads in patients who develop atrial fibrillation during pacemaker implantation is feasible; fibrillatory electrogram amplitudes showed a good correlation with the atrial signal after conversion to an organized atrial rhythm (r = 0.698). Acceptable atrial pacing thresholds can be expected as well.
Learning Curve Characteristics of Pacing Lead Extraction with a Laser Sheath
Authors: BRACKE FRANK A. , MEIJER ALBERT , VAN GELDER BERRY
Published: July 2006

The learning curve characteristics of lead extraction with a laser sheath were examined in 19 patients. Forty‐two leads were removed: five leads were removed by traction alone, five required a femoral approach as a primary procedure and a laser sheath was used in 32 lead extraction attempts. Primary laser success was achieved in 26 attempts (81 %). A femoral approach was successfully applied as a back‐up procedure in five of the failures. Overall, 26% of the leads were removed by the femoral approach. The overall success rate was 98% (41 of 42 leads). No variables related to the patients, leads, or extraction techniques were significantly related to failure of laser sheath extraction. There was a distinct learning curve with all but one failure occurring in the first half of our cases. All failures occurred with leads implanted from the right subclavian vein. In four, a sharply angled curve at the subclavian vein‐superior vena cava junction could not be passed with the laser sheath. The ability to smooth this curve improved the results during the learning curve. All procedures were performed in the operating room for safety reasons. This precaution was lifesaving in a case of acute tamponade after laser extraction of an atrial lead. In another case the left internal mammary artery was torn after laser sheath extraction, causing the formation of a false aneurysm. New pacing leads were introduced in nine patients during the same procedure. The mean procedure time was 255 ± 110 min. reflecting the complexity of these procedures.
Characteristics of the Signal‐Averaged P Wave in Orthotopic Heart Transplant Recipients
Authors: VOLGMAN ANNABELLE S. , WINKEL ELAINE M. , PINSKI SERGIO L. , FURMANOV SERGEY , COSTANZO MARIA R. , TROHMAN RICHARD G.
Published: July 2006

Rejection remains the Achilles heel of Orthotopic cardiac transplantation (OHT). Reliable non‐invasive markers of rejection are desirable for timely therapy and to reduce risks and costs. Changes in atrial electrophysiology may precede ventricular changes during acute rejection. Although P wave duration in the signal‐averaged ECG reflects atrial conduction, the feasibility of such measurement and the range of its values in OHT patients in absence of rejection is uncertain. This study compared the filtered P wave duration in 15 hypertensive OHT patients free of rejection with that in 15 age‐matched hypertensive controls. All OHT patients had biatrial anastomoses. Two electrophysiologists interpreted the tracings independently. Three tracings (2 OHT, 1 control) could not be interpreted by either reader. An adequate P wave signal‐averaged ECG was obtained in the remaining patients, despite the frequent presence of dissociated P waves (recipient and donor atria) on standard ECG in OHT patients. There was good interobserver agreement in the measurement of filtered P wave duration (r = 0.91; P < 0.0001). Conclusions: The filtered P wave duration was significantly shorter in the OHT patients (112 ± 15 ms versus 128 ±14 ms; P= 0.008). Filtered P wave duration can be measured in most OHT. Filtered P wave duration is shorter in OHT patients than in hypertensive controls, possibly as a result of the reduced mass of the truncated donor atria. Further studies are needed to determine whether the signal‐averaged P wave can be useful to predict acute cardiac rejection.
Declining Need for Pacemaker Implantation After Cardiac Transplantation
Authors: PARRY G. , HOLT N.D. , DARK J.H. , McCOMB J.M.
Published: July 2006

The need for permanent pacemaker implantation was retrospectively reviewed in 436 consecutive cardiac transplant recipients at our center between 1985 and 1998. The incidence of pacemaker implantation was examined in three arbitrarily defined periods: period 1, 1985–1990, before a review of pacemaker implantation policy; period 2, 1991–1995, after a change in policy to delay pacemaker implantation resulting from the review; and period 3, 1996–1998, after audit of this policy change, and the introduction of a change in surgical technique, from the standard atrial anastomosis to the bicaval anastomosis. Pacemaker implantation was not required in any recipient after the change in surgical technique, suggesting that the bicaval technique preserves sinus node function much better than does the standard atrial anastomosis.
QT Interval and QT Dispersion Measured with the Threshold Method Depend on Threshold Level
Authors: BATCHVAROV VELISLAV , YI GANG , GUO XIAOHUA , SAVELIEVA IRINA , CAMM A. JOHN , MALIK MAREK
Published: July 2006

Various computerized methods with multiple parameter options for measurements of the QT interval now are available. The optimum parameter setting for most algorithms is not known. This study evaluated the influence of the threshold level applied on the T wave differential on the QT interval and its dispersion measured in normal and abnormal electrocardiograms (ECGs). Seven hundred sixty ECGs recorded in 76 normal subjects and 630 in 63 patients with hypertrophic cardiomyopathy (HCM) (10 consecutive recordings in each individual) were analyzed. In each lead of each ECG, the QT interval was measured by the threshold method applied to the first differential of the T wave. The threshold level was varied between 5% and 30% of the T wave maximum in 1% steps, resulting in 26 different choices of QT measurements. With each choice the maximum QTc and the QT dispersion (QTd, standard deviation of the QT in all 12 leads) were obtained for each recording. The maximum QTc was significantly longer in HCM patients than in normal subjects (P < 0.001) at all threshold levels except between 5% and 7%. The QTd was significantly greater in HCM patients at all threshold levels. The QTc and QTd changed significantly with the threshold level. The maximum QTc varied up to 60 ms in normal subjects and up to 70 ms in HCM patients, depending on the threshold level. Thus, the QT intervai and its dispersion measured with the threshold method applied to the first T wave differential depended significantly on the threshold level in both normal and diseased hearts. All programmable options of available automatic instruments should be examined carefully before any study, and all algorithmic details should be systematically presented.
Assessment of Intersignal Variability for Discrimination of Atrial Fibrillation from Atrial Flutter
Authors: JUNG JENS , STRAUSS DANIEL , SINNWELL THOMAS , HOHENBERG GREGOR , FRIES ROLAND , WERN HARALD , SCHIEFFER HERMANN , HEISEL ARMIN
Published: July 2006

The analysis of endocardial signals obtained from an electrode located in the right atrium enabled by new dual chamber implantable cardioverter defibrillators may be helpful to provide additional therapies such as overdrive pacing or low energy atrial cardioversion for the treatment of concomitant atrial flutter (AFL) or atrial fibrillation (AF). Algorithms for discrimination of atrial tachyarrhythmias based on rate counting are of limited efficacy. The aim of this study was to assess the intersignal variability by using fast discrete wavelet transforms (FDWT) as a new method of discrimination of AF from AFL. Patients with spontaneous episodes of AF/AFL or patients who developed AF/AFL during an electrophysiological study were studied. The endocardial signals were recorded from the high right atrium using a transvenous 5 Fr bipolar electrode catheter (interelectrode spacing: 1 cm). The signals were digitized (2 kHz, 12‐bit resolution) after amplification and filtering (40–500 Hz). Within data segments of 10‐second duration, 25 consecutive signals were selected and normalized and FDWT was applied. Standard deviations of the wavelet coefficients (SD) from coarse scales (scale 4–8) were calculated. A total of 94 data segments (AF: 52, AFL: 42) from 28 patients were analyzed. SD at each considered scale was higher for AF than for AFL (P < 0.001). SD at scale 8 discriminated between AF from AFL with 100% sensitivity and specificity. We conclude that assessment of intersignal variability of bipolar endocardial recordings using FDWT is an effective method for the discrimination of AF from AFL. The implementation of this tool in a discrimination algorithm of an implantable device may help provide the appropriate differential therapy for atrial tachyarrhythmias.
Electrical Atrial Remodeling Assessed by Monophasic Action Potential and Atrial Refractoriness in Patients with Structural Heart Disease
Authors: LUBINSKI ANDRZEJ , KEMPA MACIEJ , LEWICKA‐NOWAK EWA , KRÓLAK TOMASZ , RACZAK GRZEGORZ , SWIATECKA GRAZYNA
Published: July 2006

The present study was performed to assess the effect of induced atrial fibrillation (AF) on atrial monophasic action potentials (MAPs) and atrial refractory period (ERP) in patients with structural heart disease. An electrode MAP catheter was placed in the right atrium to continuously measure atrial potential duration (APD90) in 13 patients (coronary artery disease, 10 patients; dilated cardiomyopathy, 2 patients; hypertrophic cardiomyopathy, 1 patient) without spontaneous AF episodes. AF was induced by rapid atrial stimulation (300–1500/min). If sinus rhythm returned within 10 minutes, AF was reinduced. The atrial ERP was measured during atrial pacing at a basic cycle length of 550 ms before AF induction and after its conversion. Results: The mean atrial ERP and the atrial APD90 before AF was 242 ± 34 ms and 256 ± 23 ms, respectively. ERP and APDgo shortening was observed after 3 minutes of AF. After 11 ± 0.5 min (10 min 20 s‐13 min 10 s) of AF, ERP and APD90 reached their minimal values of 72%± 13% and 71%± 10% of baseline, respectively. ERP and APD90 returned to their initial values within 10 minutes after conversion of AF. A tendency toward longer duration of consecutive AF episodes and facilitation of their induction was observed. Conclusion: The present study confirms that short episodes of AF modify the electrophysiological properties of the atria in humans. In patients with structural heart disease, induced atrial fibrillation shortens the atrial ERP as well as the atrial APD90. The changes were reversible within 10 minutes after arrhythmia termination.
Nonfluoroscopic Localization of an Amagnetic Catheter in a Realistic Torso Phantom by Magnetocardiographic and Body Surface Potential Mapping
Authors: FENICI RICCARDO , PESOLA KATJA , MÄKIJÄRVI MARKKU , NENONEN JUKKA , TEENER UWE , FENICI PETER , KATILA TOIVO
Published: July 2006

This study was performed to evaluate the accuracy of multichannel magnetocardiographic (MCG) and body surface potential mapping (BSPM) in localizing three‐dimensionally the tip of an amagnetic catheter for electrophysiology without fluoroscopy. An amagnetic catheter (AC), specially designed to produce dipolar sources of different geometry without magnetic disturbances, was placed inside a physical thorax phantom at two different depths, 38 mm and 88 mm below the frontal surface of the phantom. Sixty‐seven MCG and 123 BSPM signals generated by the 10 mA current stimuli fed into the catheter were then recorded in a magnetically shielded room. Non‐invasive localization of the tip of the catheter was computed from measured MCG and BSPM data using an equivalent current dipole source in a phantom‐specific boundary element torso model. The mean 3‐dimensional error of the MCG localization at the closer level was 2 ± 1 mm. The corresponding error calculated from the BSPM measurements was 4 ± 1 mm. At the deeper level, the mean localization errors of MCG and BSPM were 7 ± 4 mm and 10 ± 2 mm, respectively. The results showed that MCG and BSPM localization of the tip of the AC is accurate and reproducible provided that the signal‐to‐noise ratio is sufficiently high. In our study, the MCG method was found to be more accurate than BSPM. This suggests that both methods could be developed towards a useful clinical tool for nonfluoroscopic 3‐dimensional electroanatomical imaging during electrophysiological studies, thus minimizing radiation exposure to patients and operators.
Magnetocardiographic Pacemapping for Nonfluoroscopic Localization of Intracardiac Electrophysiology Catheters
Authors: FENICI RICCARDO , PESOLA KATJA , KORHONEN PETRI , MÄKIJÄRVI MARKKU , NENONEN JUKKA , TOIVONEN LAURIE , FENICI PETER , KATILA TOIVO
Published: July 2006

The purpose of the study was to validate, in patients, the accuracy of magnetocardiography (MCG) for three‐dimensional localization of an amagnetic catheter (AC) for multiple monophasic action potential (MAP) with a spatial resolution of 4 mm2. The AC was inserted in five patients after routine electrophysiological study. Four MAPs were simultaneously recorded to monitor the stability of endocardial contact of the AC during the MCG localization. MAP signals were band‐pass filtered DC‐500 Hz and digitized at 2 KHz. The position of the AC was also imaged by biplane fluoroscopy (XR), along with lead markers. MCG studies were performed with a multichannel SQUID system in the Helsinki BioMag shielded room. Current dipoles (5mm; 10mA), activated at the tip of the AC, were localized using the equivalent current dipole (ECD) model in patient‐specific boundary element torso. The accuracy of the MCG localizations was evaluated by: (1) anatomic location of ECD in the MRI, (2) mismatch with XR. The AC was correctly localized in the right ventricle of all patients using MRI. The mean three‐dimensional mismatch between XR and MCG localizations was 6 ± 2 mm (beat‐to‐beat analysis). The coefficient of variation of three‐dimensional localization of the AC was 1.37% and the coefficient of reproducibility was 2.6 mm. In patients, in the absence of arrhythmias, average local variation coefficients of right ventricular MAP duration at 50% and 90% ofrepolarization, were 7.4% and 3.1%, respectively. This study demonstrates that with adequate signal‐to‐noise ratio, MCG three‐dimensional localizations are accurate and reproducible enough to provide nonfluoroscopy dependant multimodal imaging for high resolution endocardial mapping of monophasic action potentials.
Effect of Radiofrequency Catheter Ablation on Parasympathetic Denervation: A Comparison of Three Different Ablation Sites
Authors: UCHIDA FUMIYA , KASAI ATSUNOBU , OMICHI CHIKAYA , FUJII EITARO , TERAMURA SHINOBU , YASUDA MASAKI , NAKANO TAKESHI
Published: July 2006

Radiofrequency (RF) catheter ablation of supraventricular tachycardias (SVT) has been shown to result in local parasympathetic denervation. The purpose of this study was to estimate the correlation between RF cumulative energy and parasympathetic denervation at three different ablation sites. Methods: 45 patients who underwent RF ablation of 36 AV reentrant tachycardias and 9 AV nodal reentrant tachycardias were studied. Twenty patients had left free‐wall accessory pathways (group L), 8 patients right free‐wall accessory pathways (group R), and 17 patients septal accessory path ways (n = 8) or slow pathways (n ‐9)(groupS). Time and frequency domain analysis of heart rate variability on 24‐hour ambulatory ECG recordings was performed before and after RF ablation, pNN50 and the high frequency (0.15 to 0.40 Hz, HF) component were measured to examine the effects on parasympathetic nerve activity. The values of Δ pNN50 and Δ HF were expressed as the percent change of pNN50 and HF that occurred after versus before RF ablation. Results: Both pNN50 and HF significantly decreased after RF ablation in all three groups. In group S, there was a significant correlation between RF cumulative energy and Δ pNN50r = 0.66, P < 0.01) or Δ HF (r = 0.58, P < 0,05). In contrast, there was no correlation between RF cumulative energy and Δ pNNSO or Δ HF in either group L or group R. Conclusion: These data suggest that RF ablation produces parasympathetic denervation at all three sites along the mitral or tricuspid annulus and that parasympathetic fibers may be located predominantly in the septal area.
Improved Efficacy of Mode Switching During Atrial Fibrillation Using Automatic Atrial Sensitivity Adjustment
Authors: LAM CATHY T.F. , LAU CHU‐PAK , LEUNG SUM‐KIN , TSE HUNG‐FAT , AYERS GREGORY
Published: July 2006

Automatic mode switching (AMS) during atrial fibrillation (AF) in a dual chamber pacemaker is dependent on the accurate detection of an atrial electrogram. As atrial amplitude is often reduced during AF compared with sinus rhythm, this may result in failure of the AMS and a rapid ventricular response. In addition, undersensing of AF may result in competitive atrial pacing that sustains AF. We hypothesize that the use of automatic atrial sensitivity adjustment (ASA) may enhance AF sensing in a dual chamber pacemaker. We studied the AMS response with and without ASA of the Marathon DDDR (model 294–09, Intermedics, Inc.) pacemaker in 10 patients with paroxysmal AF. Intracardiac atrial electrograms during sinus rhythm and induced AF were recorded onto an analog tape recorder. They were replayed into the pacemaker to assess the AMS response at various starting atrial sensitivities from 3.5 to 0.8 mV with ASA activated and without. Atrial amplitude was reduced during AF. The higher the initial atrial sensitivity, the better is the AMS response and the lower the incidence of AF undersensing. The percentage of AMS before ASA ranged from 2.1% at an atrial sensitivity 3.5 mV to 95.6% at highest sensitivity of 0.5 mV (P < 0.05). After 10 minutes of ASA, the AMS response was improved from 1.7% to 50.6% and from 9.5% to 50.9% at starting atrial sensitivities of 3.5 mV and 2.5 mV, respectively (P < 0.05 in both instances). Undersensing during AF was also significantly reduced after ASA from 70% to 10% at a sensitivity of 3.5 mV and from 33.8% to 10.8% at 2.5 mV. There was no increase in oversensing. In four patients with paroxysmal AF with an implanted pacemaker, ASA improved AMS response in patients with a low implant atrial amplitude. In conclusion, efficacy of mode switching and AF sensing are dependent on the programmed atrial sensitivity, which can be enhanced with the use of ASA, particularly when P wave sensing during AF is borderline.
Rate and Time Dependent Effects of D‐Sotalol on the Monophasic Action Potential After Sudden Increase of the Heart Rate
Authors: MELICHERCIK JURAJ , BRACHMANN JOHANNES , SCHÖLS WOLFGANG , HILBEL THOMAS , BEYER THORSTEN , KÜBLER WOLFGANG
Published: July 2006

Experimental and clinical data suggests that almost all Class III antiarrhythmic agents diminish their ability to prolong cardiac repolarization at fast heart rates. However, only limited data exists about the time course of efficacy decay of Class III agents after sudden increase of the heart rate. In the present study, we assessed both rate and time dependent changes of the efficacy of d‐sotalol in higher stimulation frequencies following an abrupt increase in heart rate. This might imitate the situation seen in the development of paroxysmal tachycardias. Monophasic action potentials were recorded from the right ventricular apex during sinus rhythm and constant stimulation with the paced cycle length (PCL) of 550 ms, 400 ms, and 330 ms in the baseline and 20 minutes after intravenous administration of d‐sotalol (2.5 mg/kg) in seven patients with documented life‐threatening ventricular tachyarrhythmias. D‐sotalol significantly prolonged monophasic action potential duration at different steady‐state heart rates (sinus rhythm: 21.1%± 3.6%; PCL 550 ms: 16.6%± 4.3%, 400 ms: 11.2%± 2.7%, 330 ms: 5.8%± 2.1%). The prolongation is significantly shorter in higher steady‐state pacing, confirming a pronounced reverse‐use dependent decrease of the efficacy of d‐sotalol at faster stimulation frequencies. After the abrupt increase in heart rate, the beat‐to‐beat adaptation of the postdrug action potential prolongation exhibits only slight reverse‐use dependent shortening. The decrease of the efficacy of d‐sotalol is insignificant for the first 20 consecutive beats at the stimulation frequency of the PCL of 400 msec (from 16.6% at PCL of 550 ms to 14.6% at the 20th beat of the PCL of 400 ms), and for the first ten consecutive beats at the stimulation frequency of the PCL of 330 ms (from 16.8% at PCL of 550 ms to 12.3% at the 10th beat of the PCL of 330 ms). This slow decay of action potential prolongation after an abrupt increase in heart rate might contribute to the antiarrhythmic action of d‐sotalol in cardiac tachyarrhythmias.
The Potential Usage of Dual Chamber Pacing in Patients with Implantable Cardioverter Defibrillators
Authors: BEST PATRICIA J.M. , HAYES DAVID L. , STANTON MARSHALL S.
Published: July 2006

Bradycardia support by ICDs has been limited to fixed rate, ventricular pacing. Concomitant placement of a pacemaker and an ICD exposes a patient to potentially life‐threatening device interactions. ICDs capable of dual chamber pacing have recently become available. The number of ICD recipients who stand to benefit from the addition of dual chamber pacing is debated, but no data have addressed this question. This retrospective study analyzed all patients who received nonthoractomy ICD system placement at the Mayo Clinic in Rochester, MN between March 1991 and October 1996 in order to determine the proportion of patients in whom a dual chamber pacing ICD may be indicated. Definitions: (1) Definitely indicated = pacemaker present at ICD implant or NASPE Class I pacing indication; (2) Probably indicated = NASPE Class II pacing indication, NYHA Functional Class III or IV, or history of systolic congestive heart failure; (3) Possibly indicated = history of paroxysmal atrial fibrillation or an ejection fraction ≤ 20%. The results were that nonthoracotomy ICDs were placed in 253 patients. A dual chamber ICD would have been definitely indicated in 11% of the study group, probably indicated in 28%, and possibly indicated in 14%. Chronic atrial fibrillation was present at ICD implant in 6.7% of patients and developed in 0.9%/yr during follow‐up. The addition of dual chamber pacing to ICDs stands to potentially benefit approximately half (53%) of ICD recipients. These data do not address all patients who may benefit from dual chamber sensing.
The Long QT Syndrome and Torsade De Pointes
Authors: EL‐SHERIF NABIL , TURITTO GIOIA
Published: July 2006

The LQTS is a prime example of how molecular biology, ion channel, cellular, and organ physiology, coupled with clinical observations, promise to be the future paradigm for advancement of medical knowledge. Both the congenital and acquired LQTS are due to abnormalities (intrinsic and/or acquired) of the ionic currents underlying cardiac repolarization. In this review, the continually unraveling molecular biology of congenital LQTS is discussed. The various pharmacological agents associated with the acquired LQTS are listed. Although it is difficult to predict which patients are at risk for TdP, careful assessment of the risk‐benefit ratio is important before prescribing drugs known to be able to cause QT prolongation. The in vivo electrophysiological mechanism of TdP in the LQTS is described using, as a paradigm, the anthopleurin‐A canine model, a surrogate for LQT3. In the LQTS, prolonged repolarization is associated with increased spatial dispersion of repolarization. Prolongation of repolarization also acts as a primary step for the generation of EADs. The focal EAD induced triggered beat(s) can infringe on the underlying substrate of inhomogeneous repolarization to initiate polymorphic reentrant VT, sometimes having the characteristic twisting QHS configuration known as TdP. The review concludes by discussion of the clinical manifestations and current management of both the congenital and acquired LQTS. The initial therapy of choice for the large majority of patients with the congenital LQTS is a beta‐blocking drug. This therapy seems to be effective in LQT1 and LQT2 patients, but may not be as effective in LQT3 patients. Other therapeutic options include pacemakers, cervicothoracic sympathectomy, and the implantable cardioverter defibrillator. Recent molecular genetic studies have suggested several genotype specific therapies; however, long‐term efficacy data are not available.
Spontaneous Termination of Ventricular Tachycardia with Variable Patterns and Variable Mechanisms?
Authors: PRAKASH V.S. , TAI CHING‐TAI , CHEN SHIH‐ANN
Published: July 2006

A 43‐year‐old man, with repeated episodes of postmyocardial infarction monomorpbic VT, had three forms of induced sustained VT in the electrophysiology lab. The three forms of VT had variable termination patterns with no change, decrease, or increase of cycle length.
Diagnostic Value of a Pacemaker High Rate Episode Counter When Programming the Ventricular Tachycardia Zone of an ICD
Authors: SCHAIN JILL S. , DEGERATU FLORIN T. , GREENBERG RICHARD M.
Published: July 2006

A 72‐year‐old man with an ICD and a pacemaker was presented with an episode of sustained VT that accelerated to VF. The ICD failed to detect the event and deliver therapy, despite a VT apparently within the VT detection zone. The ICD detected the event after degeneration to VF and delivered appropriate therapy. The high rate event feature of the pacemaker was useful in determining proper function of the ICD along with optimal programming of VT detection.
Use of an Implantable Cardioverter Defibrillator in an Eight‐Month‐Old Infant with Ventricular Fibrillation Arising from a Myocardial Fibroma
Authors: PARK JEANNY K. , POLLOCK MARC E.
Published: July 2006

We report our experience with use of a ICD in a 7‐month‐old infant who presented with VF. We utilized an epicardial patch and active generator in the abdomen. Development of mediastinitis required explantation and eventual replacement with a subcutaneous patch and active generator in the abdomen.