Susanne Spehl

Incidence of ICD Lead Related Complications During Long‐Term Follow‐Up: Comparison of Epicardial and Endocardial Electrode Systems

The aim of this study was to evaluate the longterm stability of epicardial and endocardial lead systems for third‐generation cardioverter defibrillators (ICDs) and to assess the usefulness of diagnostic tools. One hundred forty patients with 61 epicardial (43.6%) and 79 nonthoracotomy systems (56.4%) were followed for 2 5 ± 19 months. A total of 18 (12.9%) lead related complications were documented. Complications of epicardial systems were detected in 10 patients (16.4%) during a follow‐up time of 36 ± 8 months: crinkling of patch electrodes in 6 patients (9.8%), insulation breakage of sensing electrodes in 2 patients (3.3%), and adapter defect in 2 patients (3.3%). Eight of the patients (10.1%) with transvenous‐subcutaneous systems had lead related complications during a 13 ± 6 months follow‐up: fracture of the subcutaneous patch lead in 2 patients (2.5%), dislodgment of the right ventricular lead in 2 patients (2.5%), dislodgment of the superior vena cava lead in 2 patients (2.5%), insulation breakage of sensing electrodes in 1 patient (1.3%), and connector defect in 1 patient (1.3%). There was no significant difference in the incidence of lead related complications between epicardial and endocardial systems (P > 0.05). Fractures, dislodgments, and crinklings were documented within the first 8 ± 5 months by regular chest X ray. Defects of insulation, adapter, or connector were detected 22 ± 10 months after implantation and were associated with delivery of multiple inappropriate ICD therapies. An operative lead revision was indicated for 4 epicardial (6.6%) and 6 endocardial (7.6%) lead systems. Conclusions: Endocardial lead systems offer a similar long‐term stability as compared to epicardial had systems. Chest X ray is the most useful tool to detect lead fracture, dislodgment. and patch crinkling. Marker recordings or real‐time electrograms have not been helpful in this series to identify patients with suspected lead defects prior to the experience of inappropriate ICD discharges.

Clinical efficacy of shock waveforms and lead configurations for defibrillation

A randomized, prospective comparison of the defibrillation efficacy of various shock waveforms and nonthoracotomy lead configurations was performed in five distinct patient groups undergoing implantation of a cardioverter defibrillator. In the first group using a bidirectional lead configuration, there was no significant difference in the mean defibrillation threshold (DFT) between simultaneous and sequential monophasic shocks (17.8 +/- 5.8 joules versus 17.3 +/- 2.7 joules). In the second group using a bidirectional lead configuration, the mean DFT was 21.9 +/- 7.3 joules with monophasic shocks and 14.9 +/- 5.0 joules with biphasic shocks (p < 0.001). In the third group using a unidirectional lead configuration, the mean DFT was significantly higher (p < 0.001) with monophasic shocks (22.1 +/- 4.2 joules) compared with biphasic shocks (15.0 +/- 5.4 joules). In the fourth group, an intraindividual comparison with monophasic shock waveforms showed no significant differences in DFT using either a bidirectional (21.3 +/- 5.8 joules) or a unidirectional (21.7 +/- 2.6 joules) lead configuration. In the fifth group, a simplified unipolar transvenous defibrillation lead system (active can) demonstrated significant lower DFTs (9.7 +/- 3.8 joules) compared with a standardized unidirectional lead configuration (18.0 +/- 6.8 joules). It is concluded that: (1) there seems to be no significant difference in the DFT between simultaneous and sequential monophasic shocks; (2) biphasic waveforms require significantly less energy for defibrillation than their corresponding monophasic waveforms; and (3) the unipolar single-electrode defibrillation system is easy to implant and provides DFTs at energies comparable with epicardial lead systems.

Inappropriate Implantable Defibrillator Discharge Caused by a Retained Pacemaker Lead Fragment

Introduction: Inappropriate discharge is still a major issue of implantable cardioverter defibrillator therapy. The diagnostic options of modern devices facilitate classification of the underlying abnormality.Methods and Results: A 65-year-old woman with depressed left ventricular performance received spurious shocks from an ICD, implanted for ventricular tachycardia. A lead fragment of an explanted VVI pacemaker system could be identified as cause of erroneous ventricular fibrillation detection by the ICD. The electrical noise caused by interaction between the lead remnant and the ICD lead was detectable even on the surface ECG.Conclusion: Based on our findings, removal of fragmented lead material should be considered prior to ICD implantation, to avoid potentially adverse and harmful interactions with ICD systems.

Incidence and Rate Characteristics of Atrial Tachyarrhythmias in Patients with a Dual Chamber Defibrillator

Atrial tachyarrhythmias play an important role in the treatment of patients with malignant ventricular tachyarrhythmias not only with respect to inappropriate discharges but also to left ventricular function and stroke risk. A combined dual chamber defibrillator provides separate therapies for atrial and ventricular tachyarrhythmias. To assess the incidence of atrial tachyarrhythmias in patients with this dual chamber implantable defibrillator, 40 patients with ventricular tachyarrhythmias and concomitant atrial tachyarrhythmias and/or AV conduction disturbances were included in a prospective study. During a mean follow‐up of 25 ± 11 months , 26 of 40 patients had a total of 1,430 recurrences of atrial tachyarrhythmias. The vast majority of the atrial tachyarrhythmias with regular atrial cycles had a mean median atrial cycle length of 235 ± 37 ms and a mean duration of 34 ± 144 minutes . Atrial tachyarrhythmias with irregular atrial cycles exhibited a median atrial cycle length of 198 ± 31 ms and had a mean duration of 246 ± 1,264 minutes . In addition, 67% of 375 tachyarrhythmias, in which the median ventricular cycle length during the ongoing episode could be documented, had a ventricular rate <100 beats/min. Continuous atrial arrhythmia detection with a dual chamber ICD reveals a high incidence of atrial tachyarrhythmias with a predominantly short duration of paroxysmal recurrences <1 hour in the vast majority of episodes. (PACE 2003; 26:1691–1698)

Case Report: Inappropriate Discharge of an Implantable Cardioverter-Defibrillator Caused by the Combined Count Criterion

We describe a rare case of an inappropriate defibrillator discharge during a sinus tachycardia with single fast sensed beats fulfilling the ventricular fibrillation rate criterion, activating the “combined count criterion,” although the prevalent sinus tachycardia was inside a ventricular tachycardia rate zone, programmed to monitor only mode. The “combined count criterion” is a safety feature that ensures defibrillation therapy in case of a tachyarrhythmia inside the ventricular tachycardia detection zone, that is temporarily crossing the ventricular fibrillation detection rate. This case reports shows that there is a low but unpredictable risk of device therapy even in a zone programmed to monitor only mode. This phenomenon should be considered when a monitor only zone is installed for revelation of slower tachyarrhythmias.

Initial experience with the implantable atrial and combined atrioventricular defibrillator

Hintergrund: Vorhofflimmern ist die häufigste anhaltende Herzrhythmusstörung im Erwachsenenalter. Nach der Framingham-Studie liegt die Prävalenz von Vorhofflimmern in der Allgemeinbevölkerung um 0,4% und nimmt mit höherem Lebensalter stetig zu. Mehrere Untersuchungen an Patienten haben gezeigt, daß die intraatriale Kardioversion von Vorhofflimmern ein sicheres und wirksames Therapieverfahren darstellt, das insbesondere nach erfolgloser externer Kardioversion erwogen werden sollte. Der niedrigste Energiebedarf ist mit biphasischen Schockformen und einer Elektrodenkonfiguration zu erreichen, bei der eine Elektrode im Sinus coronarius und eine zweite Elektrode im rechten Vorhof plaziert wird. Die konsequente Weiterentwicklung der intraatrialen Kardioversion von Vorhofflimmern stellt der implantierbare atriale Defibrillator dar. Methoden: Bei dem atrialen Elektroschocksystem handelt es sich um ein innovatives Behandlungskonzept für eine ausgewählte Patientengruppe mit symptomatischem, medikamentös therapierefraktärem Vorhofflimmern. Der implantierbare atriale Defibrillator, MetrixTM Modell 3000 oder 3020, ist ein multiprogrammierbares Gerät zur Detektion und Therapie von rezidivierendem Vorhofflimmern. Kürzlich wurde ein atrioventrikulärer Defibrillator, Modell 7250 Jewel AF AMD, zur Behandlung von Patienten mit malignen Kammerarrhythmien und Vorhofflimmern in die klinische Erprobungsphase eingeführt. Dieses System verfügt über eine ventrikuläre „backup“ Defibrillation in dem sehr seltenen Fall einer Schock-induzierten malignen Kammertachyarrhythmie. Die Verfügbarkeit des neuen kombinierten Vorhofkammerdefibrillators hat die Diskussionen um die Sicherheit eines „reinen“ Vorhofdefibrillators reaktiviert. Ergebnisse: Ausgewählte Patienten mit symptomatischen, lang anhaltenden Episoden von Vorhofflimmern, die mit einer Häufigkeit zwischen einmal pro Woche bis zu einmal alle drei Monate auftreten, stellen mögliche Kandidaten für ein atriales Defibrillationssystem dar. Die ersten Erfahrungen aus der multizentrischen Untersuchung belegen eine zuverlässige Detektion von Vorhofflimmern ohne den Nachweis einer fehlerhaften R-Zacken Synchronisierung sowie eine große Sicherheit bei der Termination von Vorhofflimmern ohne das Auftreten von proarrhythmischen Ereignissen bei mehr als 3500 abgegebenen Schocks. Bis zum Mai 1998 erhielten weltweit 170 Patienten das MetrixTM-Defibrillationssystem. Bei der chronischen Behandlung mit dem atrialen Defibrillator sind die folgenden Aspekte zu berücksichtigen: die Wirksamkeit und Sicherheit, die Akzeptanz des Verfahrens, das potentielle Risiko einer Thromboembolie, die Lebensqualität sowie die Kosten-Nutzen-Relation dieser neuen Behandlungsmethode. Schlußfolgerungen: Der klinische Stellenwert des implantierbaren atrialen Defibrillators im Armamentarium der uns gegenwärtig zur Verfügung stehenden Therapieverfahren in der Behandlung von rezidivierendem Vorhofflimmern bleibt abzuwarten, da neben dem offensichtlich sehr geringen Risiko einer potentiellen Induktion ventrikulärer Proarrhythmien vor allem der Patientenakzeptanz und somit der Lebensqualität eine entscheidende Bedeutung für die Verbreitung dieses innovativen elektrotherapeutischen Verfahrens zukommt. Erste Erfahrungen mit dem implantierbaren atrialen Defibrillator haben gezeigt, daß Vorhofflimmern zuverlässig erkannt wird und bisher keine maligne Herzrhythmusstörung durch die Elektroschockabgabe induziert wurde. Erste klinische Ergebnisse mit dem kombinierten atrioventrikulären Defibrillator zeigen eine hohe Sensitivität für maligne Herzrhythmusstörungen bei einer signifikant verbesserten Spezifität zur Vermeidung inadäquater Schocktherapien bei supraventrikulären Tachyarrhythmien. Dieses Elektrosystem kommt vor allem für Patienten in Betracht, die sowohl an supraventrikulären als auch an ventrikulären Tachyarrhythmien leiden. Bei der Auswahl der geeigneten Therapieform sollte bei jedem einzelnen Patienten eine sorgfältige Nutzen-Risiko-Abwägung vorgenommen werden.Background: The promising results achieved with internal atrial defibrillation have facilitated the development of an implantable atrial defibrillator. Methods: For any new therapy, it is imperative to demonstrate safety, efficacy, tolerability with improvement in quality of life, and cost-effectiveness compared to already available therapeutic options. Most importantly, the efficacy and safety rates with a new therapy should be better or at least as good than those observed with previously available means. Maintenance of sinus rhythm or prolonged duration in arrhythmia-free intervals should be clearly demonstrated with an implantable atrial defibrillator, the MetrixTM system. Recently, a new dual-chamber defibrillator (7250 Jewel AF AMD) has entered clinical evaluation. The most important new features of the 7250 AMD system include: dual-chamber pacing, a new dual-chamber detection criterion for rejection of supraventricular tachycardias, detection and treatment modalities of atrial arrhythmias, prevention strategies for atrial arrhythmias. The dual-chamber detection criterion is constantly monitoring the rhythm in the ventricle as well as in the atrium. This new dual-chamber detection algorithm is used to improve discrimination of ventricular tachycardia from supraventricular tachycardia by applying pattern recognition methods based on different P-wave positions within RR sequences. The detection algorithm can be used to withhold inappropriate ventricular therapies. Results: Initial clinical experience with the MetrixTM system indicates stable atrial defibrillation thresholds, appropriate R-wave synchronization markers, no shock induced ventricular proarrhythmia, and excellent detection of atrial fibrillation with a specificity of 100%. Ventricular proarrhythmia has not been reported for correctly R-wave synchronized low energy shocks when closely coupled RR intervals and long-short cycles are avoided. The first results with the 7250 Jewel AF device suggest a high sensitivity for induced ventricular tachyarrhythmias and an increased specificity for reduction of inappropriate therapies.

Prospective evaluation of the quality and long-term stability of atrial signals in non-thoracotomy defibrillation electrodes: comparison of four different endocardial electrograms.

Documentation of atrial signals in stored endocardial electrograms of modern implantable cardioverter-defibrillators (ICD) is a useful tool to classify the underlying arrhythmia leading to device therapy. Newest generations of ICD provide near- and far-field electrograms derived between various endocardial electrodes. The aim of this prospective study was to assess the quality and long-term stability of atrial signals in different far-field configurations including the active can housing.Methods and Results:A total of 300 real-time endocardial electrogram recordings in 60 consecutive patients with a modern ICD in subpectoral position were analysed at the time of implant, pre-hospital discharge, 1, 3 and 12 months<%0> follow-up. Four different configurations were evaluated: right ventricular coil to can housing, can housing to pace/ sense ring, right ventricular coil to pace/sense tip, and pace/ sense tip to pace/sense ring. The best visibility of p-waves at an ECG-resolution of 0.5 mV/mm was seen in the can to coil configuration (77% of the patients). In the can to pace/sense ring electrogram p-waves could be observed in 58% of the patients. No p-waves were visible to pace/sense tip to pace/ sense ring. At a resolution of 1.0 mV/mm p-waves were only visible in 10% of all patients exclusively in the can housing to right ventricular coil configuration. The results were stable (100% of the patients) over a follow-up of one year.Conclusions:Endocardial far-field electrograms, derived from the can housing and the right ventricular coil provide a p-wave visibility in 77% of the patients and demonstrate a long-term stability over at least one year, provided that the ECG-resolution is set at 0.5 mV/mm. Since the electrogram resolution of stored electrograms depends on the EGM-range, and the ECG-resolution at an EGM-range of 15 mV would be 1 mV/mm, the EGM-range is recommended to be programmed to 7.5 mV to ensure an ECG-resolution of at least 0,5 mV/mm for stored electrograms.

What Is the Best Algorithm to Discriminate Between Supraventricular and Ventricular Tachyarrhythmias

Single-chamber ventricular defibrillator implantation has been shown to be an effective and safe treatment for patients with malignant ventricular tachyarrhythmias and to significantly reduce the incidence of sudden cardiac death. However, the high incidence of inappropriate implantable cardioverter defibrillator (ICD) therapy due to supraventricular tachycardias (SVT) is a major challenge and has been reported to affect up to 25% of patients [1, 2]. Enhanced detection criteria such as rate stability, sudden onset, and morphology assessment improve the specificity of ICD therapy, but may place the patient at risk of underdetection of ventricular tachycardia (VT) [3–7]. Recently, it has been shown that algorithms using dual-chamber sensing may significantly improve differentiation between SVT and VT [8–10]. Another beneficial effect of dualchamber ICD may be the opportunity not only to sense in the atrium, but also to pace in this chamber. Although the beneficial effects of DDD pacing are well known, most of the currently available ICDs provide only fixed ventricular antibradycardia pacing. In a recent retrospective study the need for antibradycardia pacing was analyzed in a consecutive series of 139 ICD patients [11]. The findings of this report indicate that up to 18% of the ICD patients are in need of antibradycardia pacing, with up to 80% of these patients having an indication for DDD pacing. These results are supported by an independent analysis from our center [12].

Detektionsalgorithmen zur Diskriminierung supraventrikulärer und ventrikulärer Tachykardien

ZusammenfassungNeben der QRS-Breite und der QRS-Morphologie als Detektionsalgorithmus in Einkammersystemen existieren bereits Zweikammersysteme, bei denen atriale Signale mit in die Therapieent-scheidung einbezogen sind. In ersten Studien konnte eine Verbesserung (1, 2) vor allem für die Erkennung von Sinustachykardien und Vorhofflattern nachgewiesen werden. Inadäquate Therapien bei tachyarrhythmischem Vorhofflimmern mit regelmäßiger Überleitung auf die Ventrikel können deutlich reduziert, nicht jedoch gänzlich vermieden werden. Alle Algorithmen zu Erhöhung der Spezifität bedürfen einer sorgfältigen individuellen Prüfung, um eine sichere Detektion ventrikulärer Tachyarrhythmien zu gewährleisten.

[Circadian variation of ventricular tachyarrhythmias in patients with an implantable cardioverter-defibrillator].

ZusammenfassungEine zirkadiane Variabilität konnte für den plötzlichen Herztod und den akuten Myokardinfarkt in zahlreichen Studien nachgewiesen werden. Diese Studien basierten in der Hauptsache auf Notfallprotokollen, Augenzeugenberichten und der Auswertung medizinischer Archive. Seit der Einführung implantierbarer Kardioverter-Defibrillatoren (ICD) ist es möglich, die tageszeitliche Verteilung plötzlicher Herztodesfälle über einen Langzeitverlauf systematisch zu evaluieren. Mit Hilfe integrierter Speicherfunktionen der neuesten Generationen dieser Aggregate wie RR-Intervalle, Uhrzeitspeicher und zuletzt endokardiale Elektrogramme können die dokumentierten Arrhythmien liegen für verschiedene kardiale Grunderkrankungen vor. Bei Patienten mit dilatativer Kardiomyopathie scheint ein Maximum ventrikulärer Tachyarrhythmien am Abend vorzuherrschen. Für Koronarkranke wurde in der Mehrzahl der vorliegenden Studien ein Häufigkeitsgipfel in den Vormittagsstunden ermittelt. Im Hinblick auf den Einfluß von β-Blockern und anderer antiarrhythmischer Substanzen konnte in den bisherigen Untersuchungen an diesem Hochrisikokollektiv bisher kein signifikanter Effekt auf die tageszeitliche Variation von Arrhythmieepisoden gefunden werden. Subgruppenanalysen zu den zirkadianen Verteilungsmustern für schnelle und langsame Tachykardien ergaben unterschiedliche Resultate. Einige Untersuchungen konnten eine höhere Variabilität für schnelle Tachykardien ermitteln. Andere kamen zu vergleichbaren Verteilungsmustern für langsame und schnelle Tachyarrhythmien. Bei einer höhergradigen Herzinsuffizienz ist die zirkadiane Variabilität weniger ausgeprägt. Erste Ergebnisse deuten darauf hin, daß berufstätige und jüngere Patienten eher einer ungleichen Verteilung arrhythmischer Episoden über den Tag unterliegen als Patienten mit einem reduzierten Aktivitätsniveau In Zukunft sollte der Einfluß antiarrhythmischer Substanzen auf die zirkadiane Verteiling maligner Tachyarrhythmien und deren Triggerfaktoren geprüft werden, um präventive Maßnahmen einleiten zu können.SummaryFor the acute myocardial infarction and sudden cardiac death a circadian variation can be observed. There are several, mostly epidemiological studies that demonstrate this non-uniform distribution of events in different day-time periods. These studies are in the vast majority based on eye-witness reports, medical documents and retrospective evaluation of the timing of the event. Moreover, they represent only singular observations in a heterogeneous population. With the introduction of implantable cardioverter-defibrillators which provide extensive diagnostic features such as stored RR-intervals, endocardial electrograms of each episode and internal time storage, an exact analysis of the circadian variation of malignant ventricular tachyarrhythmias became feasible. Ventricular tachyarrhythmias follow a different circadian distribution with increased number of events at certain day-time periods. For patients with a coronary artery disease a significantly higher risk to experience a potentially fatal arrhythmia could be shown for the mid-morning hours and a secondary peak occurrence for the late afternoon and the early evening. Patients with idiopathic dilated cardiomyopathy tend to have a higher probability of events in the evening hours. With respect to β-blockers and other antiarrhythmic drugs most of the studies failed to confirm a blunting influence on the degree of variability for fast arrhythmias. Others showed similar patterns for fast and slow tachycardias. Another clinical parameter, the degree of congestive heart failure was in some studies found to influence the pattern in the sense of causing a distinct difference in occurrence frequency. A higher vairation was determined for lower NYHA classes < III. Other studies were contrary to these findings. The activity level before the onset of arrhythmias has yet been only insufficiently analyzed regarding the day-time-variability. But first results make believe, that patients younger than 50 years and still involved in the working process seem to follow a more varying circadian distribution. More substudies will have to be performed to compare working and nonworking patients and patients with different structural heart diseases. Furthermore ther influence of antiarrhythmic agents on the day-time-variation of ventricular tachyarrhythmias should be assessed. Finally, there, should be systematic prospective studies that evaluate the influence of drug administration on triggers of ventricular tachyarrhythmias such as sympathoadrenergic activity, premature ventricular beats, reduction of heart rate variability and others with respect to their day-time-variability.