bluuebunny/crossref_metadata_2025 huggingface dataset:
Unexpected Complete AV Block Following Transcatheter Ablation of a Left Posteroseptal Accessory Pathway
Authors: SEIDL KARLHEINZ , HAUER BERND , ZAHN RALF , SENGES JOCHEN
Published: July 2006

Radiofrequency catheter ablation is the procedure of choice for the nonpharmacological treatment of AV connections that are responsible for debilitating tachycardia. This article describes a patient with a manifest left posteroseptal accessory pathway and recurrent syncopes in whom a transient complete AV block occurred after transcatheter radiofrequency ablation of the left posteroseptal pathway. Three electrical abnormalities were present in this patient: AV infra‐Hisian block, a left posteroseptal accessory pathway, and an AV nodal reentry tachycardia. This case report reminds you that one should be prepared for all fall backs during catheter ablation.
Internal Cardioversion of Atrial Fibrillation with a Single Lead Configuration in a Patient with Massive Diaphragmatic Herniation
Authors: SCHNEIDER MICHAEL A.E , WEYERBROCK SONJA , HERRMAN ROBERT , ZRENNER BERNHARD , PLEWAN ANDREAS , ALT ECKHARD , SCHÖMIG ALBERT , SCHMITT CLAUS
Published: July 2006

An anatomically related circumstance is reported as indication for the internal low energy Cardioversion instead of an external approach. A new single lead electrode configuration is described.
Surgery Without Interventions?
Authors: GUIRAUDON GERARD M.
Published: July 2006

Cardiac surgeons took to the heart and claimed an exclusive privilege to intervene. The task of cardiologists was to identify “candidates” and feed the Great Surgical Machine. Recently catheter surgery has developed and fell into the hands of cardiologists, who became interventionists. Cardiac surgeons are concerned about losing interventions and their identity. The analysis of the current situation implies a revisitation of old concepts: surgery, intervention, therapy, patients, invasiveness etc… etc… and a review of our therapeutic philosophy. Therapeutic plans comprise three interrelated components: the target, the bullet (therapeutic agent), and the gun (the way of delivering the bullet on target). This description characterizes surgery as a way of delivering. If side effects are effects that do not affect the target, surgical procedures are mostly side effects, with significant morbidity. Future surgical rationales should reconcile target‐specific therapy and minimal collateral damages: Minimal Surgery! or to use a new buzz, less invasiveness. Cardiac surgery has focused too much on surgical practice and neglected the rest of cardiology, missing opportunities for new researches, new rationales, and new techniques. Surgeons must become again Renaissance Men, involved in the entire field of cardiology, with a special skill in surgical techniques. Cardiac surgeons should no longer confine their practice to the delivering end. This end does not, any more, justify the means.
Reduction in Energy Pacing Thresholds by Overlapping Biphasic Stimulation Versus Conventional Bipolar Pacing
Authors: LAZARUS A. , TASKIRAN M. , RITTER P. , GRAS D. , CAZEAU S. , MUGICA J.
Published: July 2006

Overlapping biphasic (OLBI) stimulation is a new pacing waveform consisting of two simultaneous monophasic pulses of opposite polarities applied to a bipolar electrode. The goal of this prospective study was to compare, using conventional pacing leads, the acute energy pacing thresholds, measured at 0.5‐ms pulse duration, associated with bipolar versus OLBI (mode 7 and mode 8) pulse delivery. Results: Thirty one leads were tested in 20 patients. Of these leads, 7 (23%) were implanted chronically, 12 (39%) were in atrial positions, and 19 (61%) in ventricular positions. Energy pacing thresholds were significantly lower (‐25.6 ± 25.6 %, P = 0.005) in OLBI mode 8 (1.30 ± 3.96 μJ) compared to bipolar (1.55 ± 4.37 μJ) pacing, regardless of the pacing site or length of service of the leads. In contrast, OLBI mode 7, which has an anodal component, at the tip electrode was associated with higher energy pacing thresholds (3.65 ± 6.48 μJ; +358.3 ± 219.4%, P = 0.002). Conclusions: Mode 8 OLBI pacing is associated with lower acute energy pacing thresholds when used with bipolar leads in contact with the myocardium. OLBI pacing may increase pacemaker longevity by reducing long‐term energy consumption.
Full Ventricular Capture Indicated by the QT Interval Function
Authors: GOTTFRIDSSON CHRISTER , WALLENTIN INGEMAR , DERNEVIK LEIF , VAN ROOIJEN HENK , VAN GROENINGEN CHRIS , EDVARDSSON NILS
Published: July 2006

The atrioventricular (AV) interval is critical in dual chamber (DDD) pacing in patients with hypertrophic obstructive cardiomyopathy (HOCM) to obtain full ventricular capture (FVC) with maximal reduction of the left ventricular (LV) outflow gradient and optimal LV diastolic filling. We studied the relationship of FVC, fusion, spontaneous AV conduction, and the QT interval. Methods: 11 patients with various cardiac diseases and stable AV conduction received a QT sensing Diamond (tm) Vitatron, DDD pacemaker. Software was downloaded into the pacemaker. In the DDD pacing mode, with the QT interval measured from the ventricular pacing stimulus to the end of the T wave, the AV interval was shortened from 400 ms, in 20‐ms steps, to 90 ms. At 90 ms the stimulation rate was increased by 30 beats/mm and the AV interval was increased stepwise. FVC and fusion was examined on the surface ECG, Results: At 400 ms interval, spontaneous AV conduction inhibited the pacemaker. Shortening the AV interval resulted in pacing with a short QT interval. Further reduction of the AV interval resulted in a longer QT interval up to a point where the QT interval became stable. This point, the bending point in the plot of measured QT interval versus shortened AV intervals, coincided with the point of FVC. The relation of the QT‐AV interval plot and the point of fusion was comparable when lengthening the AV interval at a 30 beats/mm faster stimulation rate. Conclusion: The bending point in the QT interval versus AV interval plots showed a good correlation with the FVC and fusion points observed on ECG. The results suggest that automatic discrimination between fusion and full capture using QT interval measurements may be feasible.
Dual Chamber Rate Responsive Pacing System Driven by Contractility: Final Assessment After 1‐Year Follow‐up
Authors: CLÉMENTY J. ,   THE EUROPEAN PEA CLINICAL INVESTIGATION GROUP
Published: July 2006

The aim of this study was to assess the long‐term performance of a new dual chamber rate responsive pacing system based on the dynamic measurement of the peak endocardial acceleration (PEA) index of cardiac contractility. Seventy patients who participated in the Multicenter European Clinical Evaluation were studied 1 year after implantation by continuously recording the PEA and the heart rate (HR) during exercise stress testing and during 24 hours of usual activities. A complete examination of standard parameters was also performed to assess the pacing/sensing lead characteristics. Statistical comparisons were performed with the data recorded with the same protocol at 1 month after implant for each patient. A linear correlation coefficient was calculated between PEA and sinus rate when the patient showed predominant atrial tracked rhythm. There were no significant differences between PEA values measured at 1 month and 1 year (PEA = 0.41 ± 0.26 g vs 0.45 ± 0.29 g at rest and PEA = 1.63 ± 0.77 g vs 1.72 ± 0.83 g during peak exercise). The correlation coefficient remained stable (0.67 ± 0.15 vs 0.65 ± 0.14 during daily life and 0.74 ± 0.14 vs 0.77 ± 0.11 during exercise). The PEA signal detected by the sensor was reliable and stable. No long‐term complications or adverse effects were observed, and the lead performance was comparable to that of a standard lead.
Evaluation of a Dual Sensor Rate Responsive Pacing System Based on a New Concept
Authors: BONNET JEAN‐LUC , GÉROUX LAURENCE , CAZEAU SERGE ,   THE FRENCH TALENT DR PACEMAKER INVESTIGATORS
Published: July 2006

The minute ventilation is known to be one of the most physiological indicators of exercise. A curvilinear relationship between VE and the normal sinus rhythm (NSR) has been demonstrated in healthy patients. The aim of this study is to show that a pacemaker based on a VE sensor can reproduce such a relationship. Eighty‐one patients received a Talent DR 213 (ELA Medical, Montrouge, France) pacemaker with a third‐generation rate responsive algorithm. At 1‐month follow‐up, the patients underwent a treadmill exercise test, after which three groups were defined: group 1 had 6 patients who were 100% paced throughout the exercise test; group 2 had 10 patients who maintained NSR throughout the test; and group 3 had 12 patients who had cardiopulmonary recording during the exercise test. In group 1 patients, the simulation function computed the simulated rate (sim‐rate), which was compared to the sensor‐driven rate (SDR). In group 2 patients, sim‐rate was compared to the NSR. In group 3 patients, cardiac and metabolic reserves were compared to determine the appropriateness of the rate response to exercise (HRR% vs MR%). The results showed that the mean correlation coefficient between sim‐rate and SDR was 0.983 ± 0.005 (P < 0.001); the mean correlation coefficient between NSR and SDR was 0.92 ± 0.07 (P < 0.001); and a linear relationship was found between HRR% and MR%, with a mean slope of 1.1 ± 0.2 that was significantly equal to the theoretical value of 1 (P = NS). In conclusion, combining an activity‐driven sensor with a physiological sensor allows the preservation of a physiological rate response during exercise.
A Software Sensor Using Neural Networks for Detection of Patient Workload
Authors: ANDERSSON J.L. , HEDBERG S‐E , HIRSCHBERG J. , SCHÜLLER H.
Published: July 2006

The morphology of intracardiac electrograms (IEGMs) was used for pacemaker patient workload estimation. The body posture also was studied as another characteristic. The IEGMs were obtained and recorded via temporary transcutaneous leads connected to the implanted pacemaker. IEGMs were recorded during exercise and at rest. Recordings at rest were performed in different body positions. The morphology was analyzed visually in order to observe changes due to workload and posture. The recordings were digitized and processed by a computer‐simulated neural network. The network was used as an automatic IEGM classifier based on the morphology. Our results show that the morphology of the IEGM may be used as an indicator of patient workload and body posture. The necessary information is found mainly in the ST segment. We conclude that neural networks seem to be useful in an active cardiac device.
Interindividual Comparison of Different Sensor Principles for Rate Adaptive Pacing
Authors: MALINOWSKI KLAUS
Published: July 2006

In recent years a multitude of rate adaptive sensor systems based on different sensor signals have been developed to adapt the pacing rate to the physical load of the patient. In contrast to those systems the closed loop stimulation (CLS) represents a new concept, which regards the pacemaker as part of the cardiocirculatory system. The pacemaker converts the regulating information of the circulatory center into a heart rate. This study compares the closed loop stimulation and the different sensor systems that evaluate external parameters for rate adaptive pacing with a control group. To this end, 27 patients and 15 patients with a healthy sinus node (control group) were subjected to physical and mental stress tests. The recorded results were analyzed with regard to the maximum rates reached during stress. The results show that none of the studied sensor‐controlled systems was able to determine an adequate pacing rate under all of the various load states. The dual sensor systems experience problems in balancing the input of the two sensor signals when calculating the pacing rate. The evaluation of a single external parameter, such as the acceleration of the upper body with the accelerometer, also failed to provide an adequate pacing rate in many stress situations. In contrast to all sensor systems, CLS achieved a heart rate in agreement with those of the reference group in all physical and mental stress situations.
Programmed Atrial Sensitivity: A Critical Determinant in Atrial Fibrillation Detection and Optimal Automatic Mode Switching
Authors: LEUNG SUM‐KIN , LAU CHU‐PAK , LAM CATHY TSE‐FUN , TSE HUNG‐FAT , TANG MAN‐OI , CHUNG FELSA , AYERS GREGORY
Published: July 2006

Automatic mode switching (AMS) prevents tracking of paroxysmal atria] fibrillation (AF) in dual chamber pacing. The correct detection of AF can be affected by the programmed atrial sensitivity (AS). We prospectively studied the relationship between AS, AF under‐sensing, an d AMS, using unfiltered bipolar in tracardiac atrial electrogram s recorded from 17 patients during sinus rhythm (SR) and in AF. Overall, 780 rhythms were recorded and replayed onto three dual chamber pacemaker models using different AMS algorithms (Thera DR 7940, Marathon DDDB 294–09, and Meta DDDH 1254), and the ventricular responses were measured. AS was randomly programmed in steps from the highest available AS to half of the mean atrial P wave amplitude (PWA), and the percentage of appropriate AMS responses (defined as a ventricular pacing rate at the expected AMS mode) were recorded. AMS efficacy was related to the programmed AS settings in an exponential manner. At low AS settings, a higher percentage of tests were associated with absence of, or with intermittent AMS and tracking of AF, whereas at higher AS, oversensing of noise during SR occurred. An optimal AS measured approximately 1.3 mV, representing about one‐third of the PWA measured during SR, although oversensing of SR and undersensing of AF continued to occur in 14% of tests and time, respectively, due to the high variation in PWA during AF. Thus, a fixed AS cannot eliminate AF undersensing without inviting noise oversensing, suggesting the need for automatic adjustments of AS, or the use of a rate‐limiting algorithm to prevent rate oscillation during intermittent AF sensing. In conclusion, AMS functions of existing pacemakers were significantly limited by the undersensing of AF and oversensing of noise. Proper adjustment of the AS is important to enable effective AMS during AF.
First Experience with an Automatic Sensing Algorithm in Single‐Lead VDD Stimulation
Authors: NOWAK BERND , FELLMANN PETER , MAERTENS STEVEN , MOLS ROLAND , DEMETZ KATHY , BRÜLS ANNETTE , GEIL STEPHANIE , VOIGTLÄNDER THOMAS , HIMMRICH EWALD , MEYER JÜRGEN
Published: July 2006

An “Autosensing” algorithm available in SSI(B) and DDD(R) pacemakers automatically adapts the device's sensitivity to changing intracardiac signals. The atrial sensing function of this algorithm was tested for the first time with a VDD pacing system in which large variations of the atrial signal may occur because the atrial electrodes float in the atrial blood pool. Methods: 15 patients with a VDD pacing system were studied (Unity 292–07, lead 425; Sulzer Intermedics). The atrial sensing threshold was measured, and the atrial sensitivity was programmed with a 2:1 safety margin. The autosensing algorithm and sensitivity profile were temporarily activated, and an ambulatory ECG with continuous marker annotation was recorded. All patients underwent a 30‐minute daily life activities protocol. A beat‐to‐beat analysis of the ambulatory ECG was correlated with the changes in atrial sensitivity. Results: The algorithm changed the baseline sensitivity from 0.57 ± 0.23 mV during the test to 0.39 ± 0.20 mV after the final rest period (P < 0.05). During the test 12.6 ± 10.2 adaptations of the sensitivity occurred (range 0–33). In eight patients atrial undersensing occurred in 4.4%± 7.5% of the cycles (4–458 unsensed P waves]. In these patients, the algorithm continuously adjusted the sensitivity towards more sensitive values, operating 19.1 ± 18.3 changes compared with 5.4 ± 7.3 changes in patients without undersensing (P = 0.009). Oversensing did not occur. Conclusion: The autosensing algorithm effectively optimized atrial sensitivity in VDD pacing. In patients with atrial undersensing the algorithm continuously remained near the most sensitive settings, thus reacting as intended. A faster sensitivity adjustment of the system would be desirable.
Is Atrial Sensing of Ventricular Far‐Field Signals Important in Single‐Lead VDD Pacing?
Authors: NOWAK BERND , KRAMM BERTHOLD , SCHWAIER HEIKE , MAIMAITIMING AILAITI , GEIL STEPHANIE , ZELLERHOFF CHRISTIAN , PRZIBILLE OLIVER , ROSOCHA STEFAN , LIEBRICH ANDREAS , MEYER JÜRGEN
Published: July 2006

In single‐lead VDD pacing the atrial sensitivity frequently is programmed to sensitive values. Atrial sensing of ventricular far‐field signals should be reduced by differential atrial sensing. The aim of the study was to evaluate the effectiveness of this approach. Methods: The study included 10 patients with a single‐lead VDD pacemaker (Thera 8948, Lead 5032). The atrial sensitivity was set to its most sensitive value of 0.18 mV and the telemetered intraatrial EGM was continuously recorded. After atrial tracked ventricular pacing, VVI pacing was performed with pacing rates from 100 to 160 beats/min in steps of 10 beats/min and up to 165 beats/min. The peak‐to‐peak amplitudes of P waves (P) and ventricular far‐field signals (VFFS) were measured from the recordings. The ratio P/VFFS that defines the atrial signal‐to‐noise ratio was calculated, and the time from stimulus to maximum of the far‐field signals amplitude (Tmax) was measured. Results: P measured 0.98 ± 0.76 mV. A VFFS was visible in the atrial channel in all patients with an amplitude of 0.45 ± 0.25 mV (range 0.01–1.0 mV), independent of the pacing rate. The ratio P/VFFS was 3.9 ± 4.2 (range 0.9–21.0). Tmax measured 99.4 ± 15.2 ms during sinus rhythm. A rate dependent shortening of Tmax to 92.7 ± 11.2 ms at 140 beats/min was observed (P = 0.001). At rates above 140 beats/min no further shortening occurred. Conclusion: Ventricular far‐field signals are measurable in the atrial channel of VDD systems and may reach considerable amplitudes, which are not rate dependent. Although differential sensing provides favorable P waves to ventricular far‐field signal ratios, refractory periods are needed to avoid far‐field sensing. The rate dependent shortening of the ventricular signal can be detected in the atrial channel in VDD pacing.
Radiographic Assessment of Atrial Dipole Position in Single Pass Lead VDD and DDD Pacing
Authors: BONGIORNI MARIA GRAZIA , MORACCHINI PIER VITTORIO , NAVA ANDREA , CAPRIOLI VINCENZO , GASCÓN DAMIAN , MORRA ANTONIO , DI GREGORIO FRANCO ,   THE MULTICENTER STUDY GROUP
Published: July 2006

Atrial electrode position was determined by radiographic analysis in 160 patients paced in single‐lead VDD for second‐ or third‐degree A‐V block, implanted > 1 year with Phymos single pass leads and Phymos 3D pacemakers. The pacing lead features an atrial dipole with a 30‐mm electrode interspace. In 44% of patients, the upper atrial electrode was positioned within a band of 20 mm centered at the level of the superior vena caval insertion (junctional area) and was in the inferior vena cava or in the atrium in 35% and 21 % of cases, respectively. In spite of these different dipole locations, all patients had stable atrium‐driven pacing at routine follow‐up visits. With the electrode in the junctional area, unipolar stimulation of up to 5 V for 1 ms resulted in stable atrial capture in 63% and 59% of the patients in supine and upright positions, respectively. With the electrode in the atrium, corresponding success rates were 45% and 54%. In the atrium, however, the prevalence of diaphragmatic stimulation was significantly lower than at the junction (10% vs 42% in supine position; 21 % vs 47% upright). Though atrial sensing function proved adequate in a wide range of positions, these results suggest that the Phymos lead atrial dipole should be positioned within the atrium, as close as possible to the atrial wall, to maximize the number of VDD patients who might benefit from single‐lead DDD pacing.
Optimizing the Hemodynamic Performance of the DDD Pacemaker: Impact of the Atrioventricular Delay on the Pulmonary Venous Flow Pattern
Authors: DOUCHET M‐P. , QUIRING E. , VI‐FANE R. , BRONNER F. , MESSIER M. , PASCO A. , CHAUVIN M. , WIHLM J‐M , BRECHENMACHER C.
Published: July 2006

This study evaluated the impact of the atrioventricular delay (AVD) on the pulmonary venous flow pattern (PVFP). Methods: Transthoracic Doppler PVFP were obtained during atrial and ventricular pacing at a fixed rate of 70 beats/min in 20 patients equipped with a DDD pacemaker, diastolic dysfunction linked to an impaired relaxation, a mean ejection fraction of 49%, and AV block. Two subgroups were analyzed equally: group I: seven patients with a normal ejection fraction and group II: 13 patients with decreased ejection fraction. Three different AVDs were studied: short (50 ms), intermediate (150 ms), and long (250 ms). Results: As the AVD increased, the diastolic filling time and the peak atrial reverse flow wave decreased (P < 0.001). There was a decreasing D wave and no significant change in the peak velocity of the S wave. The S wave became biphasic in all patients at the longest AVD of 250 ms. The systolic (S) velocity time integral (VTI) of the pulmonary wave and the systolic/total PVF‐VTI ratio increased significantly (P < 0.001). A similar response was seen in both group of patients. Conclusions: These data correlated the AVD with PVFP, supplying critical systolic information completing the diastolic data obtained from mitral Doppler patterns. These systolic measurements were especially useful for patients with heart failure and a DDD pacemaker, in order to obtain the longest diastolic filling time at the lowest atrial pressure.
The Effect of DDD Pacing on Ergospirometric Parameters and Neurohormonal Activity in Patients with Hypertrophic Obstructive Cardiomyopathy
Authors: SIMANTIRAKIS EMMANUEL N. , KANOUPAKIS EMMANUEL M. , KOCHIADAKIS GEORGE E. , KANAKARAKI MARINA K. , PARTHENAKIS FRAGISKOS I. , MANIOS EMMANUEL G. , MARKIANOS EMMANUEL , VARDAS PANOS E.
Published: July 2006

This study examined the acute and long‐term effects of DDD pacing on ergospirometric parameters and neurohormonal activity in patients with hypertrophic obstructive Cardiomyopathy (HOCM). We studied eight patients (five males), aged 56 ± 7 years, with HOCM refractory to drugs. In all patients a DDD pacemaker was implanted and programmed with an atrioventricular (AV) delay that insured full ventricular activation. The patients underwent echocardiographic examination and exercise stress testing before and 3 days, 3 months, and 12 months after pacemaker implantation. Oxygen consumption was measured at the anaerobic threshold (VO2AT) and peak exercise (pVO2). Atrial natriuretic peptide (ANP) and cyclic adenosine monophosphate (c‐AMP) levels were measured concomitantly. Left ventricular outflow tract (LVOT) pressure gradient decreased significantly from 70 ± 18 to 25 ± 12 mmHg (P < 0.05) 3 days after pacing and remained unchanged at 3 and 12 months. pVO2 and VO2AT increased significantly, from 20.1 ± 3 to 23.4 ± 3 mL/kg/min and from 16 ± 3 to 17.8 ± 2 mL/kg/min, respectively (P < 0.05). This improvement continued up to 3 months, and then remained stable until the end of the 12‐month follow‐up period. ANP levels decreased at 3 days from 85.4 ± 5.7 to 75.4 ± 7.3 fmol/mL (P < 0.05), and remained unchanged over the 12 months. c‐AMP levels did not change significantly after the onset of pacing. DDD pacing in patients with HOCM not only reduces the LVOT pressure gradient but also causes a significant early and long‐term improvement in exercise capacity and neurohormonal profile.
Application of Pulsed‐Doppler Tissue Imaging in Patients with Dual Chamber Pacing: The Importance of Conduction Time and AV Delay on Regional Left Ventricular Wall Dynamics
Authors: GESSNER MARTIN , BLAZEK GERHARD , KAINZ WALTER , GRUSKA MICHAEL , GAUL GEORG
Published: July 2006

Pulsed‐Doppler tissue imaging (pDTI) is able to measure myocardial wall velocities (systolic: S; early diastolic: E; late diastolic: A) and their timings. Relationships have been demonstrated between the preelection period and indexes of left ventricular systolic function. This study was designed to examine with pDTI the effects of variations in atrioventricular delay (A VD) (100 ms, 150 ms, 200 ms) on myocardial dynamics and on their timings at the basal interventricular septum (IVS) from an apical approach and at the posterior wall (PW) from the parasternal view. These data were compared with stroke volume measurements recorded from the left ventricular outflow tract. Seventeen patients with dual chamber pacemakers (7 because of complete heart block, 10 with sick sinus syndrome and first‐degree AV block) were studied; full atrial and ventricular capture was present at any AVD. These data were also compared with those obtained in 10 age‐matched healthy volunteers with comparable heart rates. Results: Optimal atrial contribution to left ventricular filling and, consequently, best systolic performance were achieved when AVD was programmed such that a mean interval of 77 ms was allowed between the end of the A wave and the beginning of the S wave, similar to what was measured in the healthy control group by pDTI. Conclusion: The noninvasive measurement of timings of the cardiac cycle by pDTI is helpful to determine the optimal AVD in individual patients.
Angiographic Anatomy of the Coronary Sinus and Its Tributaries
Authors: GILARD MARTINE , MANSOURATI JACQUES , ETIENNE YVES , LARLET JEAN‐MARIE , TRUONG BERNARD , BOSCHAT JACQUES , BLANC JEAN‐JACQUES
Published: July 2006

Permanent left ventricular pacing has been shown to imporve the hemodynamic and clinical status of patients with severe heart failure. To pace the left ventricle, the electrode is implanted in tributaries of the coronary sinus (CS). However, the anatomy of cardiac veins with this purpose in mind has not been described in detail. Methods: One hundred consecutive patients admitted for coronary angiography had a simultaneous coronary venography performed after the injection of 8 to 10 mL of contrast material into the left coronary artery. Cardiac veins were analyzed in antero‐posterior, left anterior oblique 60±, and right anterior oblique 30± views by three different observers. The number, dimension, angulation, and position of the coronary sinus and of its tributaries were studied. Results: Two veins are consistently present: the middle cardiac vein (mean diameter 2.62 ± 1.26 mm) and the great cardiac vein (mean diameter 3.55 ± 1.24 mm). The left posterior vein(s) (LPV) (mean diameter 2.25 ± 1.2 mm) is (are) variable in number (ranging from 0 to 3), size, and angulation. The absence of LPV limits the ability to pace the left ventricle endovenously. The diameter of the vein (< 2 mm) and its angulation may also complicate the insertion of the lead. Conclusion: Angiographic analysis of dimensions, tortuosity, number, and angulation of venous tributaries of the CS seems to allow the insertion of commercially available pacing leads in approximately 85% of cases. An increase in this percentage hinges on the development of new, dedicated leads.
Exercise Response of the Recipient Atrial Remnant After Orthotopic Cardiac Transplantation: Implications for Recipient Atrial Triggered Pacing
Authors: HOLT NICOLA D. , BRADY STEVEN , DARK JOHN H. , McCOMB JANET M.
Published: July 2006

The assumption that the recipient atrial remnant in the cardiac transplant recipient is normal has led to the suggestion that it is an appropriate trigger for permanent pacing in transplant recipients who need pacing or to restore chronotropic competence and/or mechanical synchrony of the composite atrium. We examined the chronotropic response to exercise in 12 orthotopic cardiac transplant recipients (mean age 49 years) at a mean time of 17 months posttransplantation. Recipient and donor atrial rates were noted and compared and chronotropic competence determined. Two of 12 recipient atrial remnants were in atrial fibrillation. Only six of the remaining 10 recipient atria exhibited chronotropic competence. Seven of 10 recipient atria had rates higher than that of the donor. Only four of ten recipient atria in sinus rhythm satisfied both criteria. Two of these had abnormally high atrial responses early into exercise. Of the remaining two, only one recipient atrial remnant demonstrated a ≥ 20% increase in heart rate above that of the donor at peak exercise. Hence only 1 of 12 (8.3%) transplant recipients potentially could benefit from recipient atrial triggered pacing. While recipient atrial triggered pacing is an attractive theoretical concept for restoring chronotropic competence following orthotopic cardiac transplantation, it may rarely be practical because the recipient atrial remnant displays rhythm abnormalities, chronotropic incompetence, and abnormalities in its exercise response.
Noninvasive Rejection Monitoring of Cardiac Transplants Using High Resolution Intramyocardial Electrograms: Initial US Multicenter Experience
Authors: BOURGE ROBERT , EISEN HOWARD , HERSHBERGER RAY , KELLER ANDREW , RADOVANCEVIC BRANISLAV , SCHREIER GÜNTER , KASTNER PETER , HUTTEN HELMUT , WERY SHAWN , MEHTA NAWZER
Published: July 2006

Endomyocardial biopsy (EMB) remains the mainstay for the diagnosis of acute cellular rejection in cardiac transplant patients. A noninvasive alternative that would supplant or reduce the number of EMBs would be a highly desirable and cost‐effective tool. To evaluate one potential alternative, a pacemaker with high resolution telemetry capabilities and two fractally coated epimyocardial leads were implanted in 30 patients at five transplant centers during the heart transplant procedure. Ventricular electrograms were recorded during intrinsic and paced activity and digitized to a laptop‐based data acquisition device. Electrograms were recorded at frequent intervals and systematically on days when EMBs were performed. The electrogram data were then transferred via the Internet to a central data processing site. Clinical patient management was blinded to the electrogram results and varied considerably among the five centers. Using EMB together with clinical assessment of the transplant revealed 18 cases of clinically significant rejection beyond postoperative day 27 that required antirejection therapy. The normalized parameter values extracted from the electrogram recordings during pacing (the ventricular evoked response) that were associated with significant rejection were statistically lower (86%± 16% versus 96%± 22%, P < 0.005). The application of a single‐threshold diagnosis model to the parameter values allowed detection of significant rejection with a negative predictive value of 98%. This analysis also showed that as many as 55% of the routine surveillance EMBs could have been eliminated had the pacemaker monitoring technique been used as a screening tool prior to EMB. A prospective study should further define the role of this technique in the detection and management of cardiac transplant patients.
Hospital Pager Systems May Cause Interference with Pacemaker Telemetry
Authors: DURU FIRAT , LAUBER PETER , KLAUS GEORG , CANDINAS RETO
Published: July 2006

Electromagnetic interference (EMI) is a well‐known cause of pacemaker dysfunction. The communication between pacemakers and programmers, enabled by telemetry, is also susceptible to EMI. We have observed that hospital pager systems have the potential to interfere with pacemaker telemetry. Measurements in our pacemaker clinic and in a technical laboratory have shown that inductive pager systems may disturb telemetry in the form of inaccurate battery voltage, current and impedance measurements, disturbances In intracardiac electrogram tracings, or total interruption of telemetric communications. The reason for EMI was an overlap of carrier frequencies of some pacemaker programmers (32–37 kHz) with those of our inductive pager system (36.11 kHz). Radiofrequency pager systems using higher frequencies (in MHZ range) are unlikely to cause such interference. Awareness of this interference potential may have practical implications in choosing the carrier frequencies of inductive hospital pager systems, as well as pacemaker programmers, and in planning the location of pacemaker clinics.
Transmembane Potential Properties of Atrial Cells at Different Sites of a Spiral Wave Reentry: Cellular Evidence for an Excitable but Nonexcited Core
Authors: KARAGUEUZIAN HRAYR S. , ATHILL CHARLES A. , YASHIMA MASAAKI , IKEDA TAKANORI , WU TSU‐JUEY , MANDEL WILLIAM J. , CHEN PENG‐SHENG
Published: July 2006

Transmembrane action potentials (TAPs) were recorded during simultaneous mapping of a reentrant wavefront induced in canine isolated atria. The activation pattern was visualized dynamically using a high resolution electrode catheter mapping system. During functional reentry (spiral wave), cells in the core of the spiral wave remained quiescent near their resting membrane potential. Cells away from the core progressively gained TAP amplitude and duration, and at the periphery of the spiral wave the cells generated TAPs with full height and duration. During anatomical reentry, when the tip of the wavefront remained attached to the obstacle (a condition of high source‐to‐sink ratio), the TAP near the obstacle had normal amplitude and duration. However, when the tip of the wavefront detached from the obstacle (condition of lowered source‐to‐sink ratio) the TAP lost amplitude and duration. These results are consistent with the theory that the source‐to‐sink ratio determines the safety factor for wave propagation and wave block near the core. With decreasing source‐to‐sink ratio, TAP progressively decreases in amplitude and duration. In the center of the core, the cells, while excitable, remain quiescent near their resting potential. This decrease reflects a progressive decrease in the source‐to‐sink ratio. TAP vanishes in the core where cells remain quiescent near their resting potential. Functional and meandering reentrant wavefronts are compatible with the spiral mechanism of reentry where block at the rotating point is provided by the steep curvature of the wave tip.
A Computer Model of Cardiac Electrical Activity for the Simulation of Arrhythmias
Authors: VIRAG NATHALIE , VESIN JEAN‐MARC , KAPPENBERGER LUKAS
Published: July 2006

Modern computer power allows development of models of the heart that may be helpful for the understanding of arrhythmia mechanisms if, based on realistic physiological parameters, such models can display phenomena difficult to study in nature. Therefore, a two‐dimensional model of the cardiac tissue has been implemented, where the modeling of each cell is based on membrane ionic channels (Beeler‐Reuter and Luo‐Rudy models). In addition, an ECG was computed based on the ionic currents simulated. This model allows us to observe the propagation of the action potentials Vm across the cardiac tissue, the evolution of Vm for any of the cardiac cells, and the underlying ionic currents. The computation of the ECG makes it possible to relate this information with an often‐used diagnostic tool. Simulations of normal and pathological phenomena such as functional and anatomic reentry have been performed. Our simulation results show that the applied computer model based on ionic currents seems accurate and realistic when compared with biological models and offers a new approach to study the origin, prevention, and termination of arrhythmias.
Comparative Reproducibility of QT, QT Peak, and T Peak‐T End Intervals and Dispersion in Normal Subjects, Patients with Myocardial Infarction, and Patients with Hypertrophic Cardiomyopathy
Authors: SAVELIEVA IRINA , YAP YEE GUAN , YI GANG , GUO XIAOHUA , CAMM A. JOHN , MALIK MAREK
Published: July 2006

Abnormal repolarizaiion is associated with arrhythmogenesis. Because of controversies in existing methodology, new computerized methods may provide more reliable tools for the noninvasive assessment of myocardial repolarization from the surface electrocardiogram (ECC). Measurement of the interval between the peak and the end of the T wave (TpTe interval) has been suggested for the detection of repolarization abnormalities, but its clinical value has not been fully studied. The intrasubject reproducibility and reliability of automatic measurements of QT, QT peak, and TpTe interval and dispersion were assessed in 70 normal subjects, 49 patients with acute myocardial infarction (5th day; MI), and 37 patients with hypertrophic cardiomyopathy (HC). Measurements were performed automatically in a set of 10 ECCs obtained from each subject using a commercial software package (Marquette Medical Systems, Milwaukee, WI, U.S.A.). Compared to normal subjects, all intervals were significantly longer in HC patients (P < 0.001 for QT and QTp; p < 0.05 for TpTe); in MI patients, this difference was only significant for the maximum QT and QTp intervals (P < 0.05). In both patient groups, the QT and QTp dispersion was significantly greater compared to normal subjects (P < 0.05) but no consistent difference was observed in the TpTe dispersion among all three groups. In all subjects, the reproducibility of automatic measurement of QT and QTp intervals was high (coefficient of variation, CV, 1%‐2%) and slightly lower for that of TpTe interval (2%–5%; p < 0.05). The reproducibility of QT, QTp, and TpTe dispersion was lower (12%–24%, 18%–28%, 16%–23% in normal subjects, MI and HC patients, respectively). The reliability of automatic measurement of QT, QTp, and TpTe intervals is high but the reproducibility of the repeated measurements of QT, QTp and TpTe dispersion is comparatively low.
QT Variability Before and After Episodes of Nonsustained Ventricular Tachycardia in Patients with Hypertrophic Cardiomyopathy
Authors: MEZILIS NICK E. , PARTHENAKIS FRAGISKOS I. , KANAKARAKI MARINA K. , KANOUPAKIS EMMANOUEL M. , VARDAS PANOS E.
Published: July 2006

This study examined the changes in QT dynamics occurring during 5‐minute intervals sampled immediately before and 1 hour after episodes of nonsustained ventricular tachycardia (VT) in patients with hypertrophic cardiomyopathy (HCM). Twenty‐four hour Holter recordings were performed in 10 patients with HCM in the absence of antiarrhythmic medications and processed by the ELA Medical QT analysis software. All sinus complexes were averaged over 30‐second segments and 2,880 templates were created. For each template, a mean corrected QTec (time interval between the onset of QRS and the end of the T wave) and QTac (time interval between the onset of the QRS and the peak of the T wave) were calculated, with their standard deviations (SDQTe and SDQTa) taken as indices of QT variability. The slopes of the regression line for the QTe and QTa against the corresponding RR also were calculated. Forty 5‐minute segments were analyzed immediately before (sample A) and 1 hour after (sample B) 20 episodes of nonsustained VT. QTac was significantly longer in group A than in group R (321 ± 20 vs 312 ± 22, P < 0.0001) and SDQTa was significantly lower (2.8 ± 1.2 vs 4.7 ± 3.7, P < 0.03). There were no significant differences in QTec, SDQTe, QTe/RR and QTa/RR before and after the episodes. Our data indicate that in patients with HCM, the averaged QTac is significantly longer and the QTa variability significantly lower before episodes of nonsustained VT.
Absence of Effects of Short‐Term Estrogen Replacement Therapy on Resting and Exertional QT and QTc Dispersion in Postmenopausal Women with Coronary Artery Disease
Authors: SBAROUNI EFTIHIA , ZARVALIS ELIAS , KYRIAKIDES ZENON S. , KREMASTINOS DIMITRIOS TH.
Published: July 2006

Women, on average, have a longer QT interval on the electrocardiogram and are at higher risk of developing torsade de pointes from antiarrhythmic therapy than men. Although endogenous estrogen may play a role in these sex differences, the effect of estrogen replacement therapy has not been examined. Ten women, 65 ± 7 years of age, wit/i stable angina pectoris, positive exercise test, and angiographically proven coronary artery disease (at least one ≥ 70%) stenosis were studied. All women had been postmenopausal for at least 1 year, and none had ever received hormone replacement therapy (HRT). The patients received standard dose HRT (0.625 mg/day oral conjugated estrogen) or matching placebo for 4 weeks in random order, with crossover after a 4‐week washout period. Exercise testing using the standard Bruce protocol was performed at the end of the first and third months of the study. Antianginal medications remained unchanged throughout the study period. Compared to placebo, HRT caused a significant increase in plasma estradiol levels from 5.55 ± 1.66 to 31.11 ± 14.95 pg/mL (P = 0.001). QT and QTc, as well as QT and QTc dispersion, did not differ at rest and at peak exercise between the two exercise tests. Likewise, other test results, including angina score, exercise time, ST‐T changes, blood pressure, heart rate, and double product were unchanged. Short‐term HRT did not alter cardiac repolarization at rest and during exercise in postmenopausal women with known coronary disease.
Assessment of the Coupling Between RTapex and RR Interval as an Index of Temporal Dispersion of Ventricular Repolarization
Authors: LOMBARDI FEDERICO , COLOMBO ANDREA , PORTA ALBERTO , BASELLI GIUSEPPE , CERUTTI SERGIO , FIORENTINI CESARE
Published: July 2006

To evaluate the dynamic characteristics of the relationlship between the RT and RR intervals we analyzed the RR/RTapex variability interaction with a dynamic parametric model whose parameters can be directly estimated from the beat‐to‐beat series RR and RTopex intervals. The model is designed to separate the fraction of RTapex variability driven by RR changes from that independent of RR variations and to quantify the gain and phase of the relationship between RR and RTapex intervals. The percentage of RTapex variability driven by RR variability was significantly greater in young normal subjects in comparison with postmyocardial infarction patients as well as with agematched control subjects. This new approach based on the quantification of the RTapex variability dependent and independent of beat‐to‐beat RR interval changes could be used to quantify the degree of uncoupling between the two signals thus providing a new and noninvasive index of temporal dispersion of ventricular repolarization.
Autonomic Effects of Dipyridamole Stress Testing on Frequency Distribution of RR and QT Interval Variability
Authors: THERES HEINZ , ROMBERG DIETRICH , LEUTHOLD THOMAS , BORGES ADRIAN C. , STANGL KARL , BAUMANN GERT
Published: July 2006

Transient myocardial ischemia and associated changes in the autonomic nervous system may influence heart rate and ventricular repolarization to variable degrees. This study evaluated the effect of dipyridamole (DIP) induced ischemia on the autonomic balance by spectral analysis of RR and QT intervals variability. Patients with coronary artery disease undergoing DIP stress echocardiography were studied. From high resolution ECG recordings, RR and QT interval measurements were performed by a dynamic template‐matching algorithm. A time‐variant analysis was used to estimate power in the LF (0.05–0,15 Hz) and in the HF (0.15–0.4 Hz) band of RR and QT interval spectra. Patients were grouped in ischemic and nonischemic subgroups based on the echocardiographic detection of wall‐motion abnormalities. In patients without ischemia (n = 28), DIP caused a decrease in LF power and an increase in HF power of the RR and QT interval variability, indicating concordant changes of both intervals. In contrast, patients with inducible ischemia (n = 11) showed a decrease in HF power of the RR interval spectra and an increase of HF power of QT interval spectra. Furthermore, LF power was increased for RR but decreased for QT interval spectra. Our study suggests that DIP induced ischemia causes a loss of autonomic coupling between heart rate and ventricular repolarization for sympathetic and parasympathetic activities. This lability in ventricular repolarization may constitute an arrhythmogenic substrate during acute ischemia in patients with coronary artery disease.
Heart Rate Variability During Head‐up Tilt Testing in Patients with Suspected Neurally Mediated Syncope
Authors: GRIMM WOLFRAM , WIRTHS ANDREAS , HOFFMANN JÜRGEN , MENZ VOLKER , MAISCH BERNHARD
Published: July 2006

The relation between heart rate variability (HRV) and outcome of head‐up tilt testing (HUT) in patients with neurally mediated syncope (NMS) was studied in 30 patients with presumed NMS (33 ± 13 years) and in 11 age‐matched controls. After 15 minutes of baseline supine observation, patients were tilted to 60± for 45 minutes or until syncope occurred. HRV parameters included RR intervals, standard deviation of normal‐to‐normal RR intervals (SDNN), and root mean square successive differences (RMSSD). HRV analysis was performed during 5‐minute intervals in the supine position immediately after onset of HUT and before syncope or after 30–35 minutes of tilt in patients without syncope. Syncope occurred after a mean tilt duration of 32 minutes in 14 (47%) of 30 patients with presumed NMS, whereas all controls had an uneventful HUT. In the supine position, RR intervals and RMSSD were comparable among HUT‐positive patients, HUT‐negative patients, and controls (RR intervals: 799 ± 92, 854 ± 137, and 818 ± 128 ms, P = NS; RMSSD: 43 ± 40, 36 ± 34, and 53 ± 42 ms, P = NS). Baseline SDNN was also comparable in HUT‐positive patients versus HUT‐negative patients with presumed NMS (50 ± 26 vs 52 ± 20 ms, P = NS). Within 5 minutes preceding syncope or after 30–35 minutes of tilt, RR intervals and RMSSD were shorter in HUT‐positive patients compared to HUT‐negative patients, or to controls (RR intervals: 606 ± 86 vs 710 ± 117 and 739 ± 123 ms, P < 0.05; RMSSD: 12 ± 5 vs 23 ± 19 and 40 ± 32 ms, P < 0.05). Thus, HRV analysis in the baseline supine position was not a predictor of HUT outcome in patients with suspected NMS. Syncope during HUT seemed to be preceded by increased sympathetic activity manifested by an increase in heart rate and by a decreased parasympathetic tone manifested by a decrease in RMSSD measured for 5 minutes before the event, in comparison with HUT‐negative patients and with controls.
Variable Cerebral Dysfunction During Tilt Induced Vasovagal Syncope
Authors: AMMIRATI FABRIZIO , COLIVICCHI FURIO , DI BATTISTA GIANCARLO , GARELLI FAUSTO FIUME , PANDOZI CLAUDIO , SANTINI MASSIMO
Published: July 2006

Electroencephalographic (EEG) monitoring was performed during head‐up tilt testing (HUT) in a group of 63 consecutive patients (27 males, 36 females, mean age 41.5 years) with a history of recurrent syncope of unknown origin despite extensive clinical and laboratory evaluation. Syncope occurred in 27/63 patients (42.8%) during HUT and was cardioinhibitory in 11/27 (40.7%) and vasodepressor in 16/27 (59.3%). All patients with a negative response to HUT had no significant EEG modifications. In patients with vasodepressor syncope a generalized high amplitude 4–5 Hz (theta range) slowing of EEG activity appeared at the onset of syncope, followed by an increase in brain wave amplitude with a reduction of frequency at 1.5–3 Hz (delta range). The return to the supine position was associated with brain wave amplitude reduction and frequency increase to 4–5 Hz, followed by restoration of a normal EEG pattern and arousal (mean total duration of syncope 23.2 s). In patients with cardioinhibitory syncope, a generalized high amplitude EEG slowing in the theta range was noted at the onset of syncope, followed by a brain wave amplitude increase and slowing in the delta range. A sudden reduction of brain wave amplitude ensued leading to the disappearance of electroencephalographic activity (“flat” EEG). The return to the supine position was not followed by immediate resolution of EEG abnormalities or consciousness recovery, both occurring after a longer time interval (mean total duration of syncope 41.4 s). EEG monitoring during HUT allowed the recording and systematic description of electroencephalographic abnormalities developing in the course of tilt induced vasovagal syncope.