Stefan Rosocha

Proarrhythmic Effect of Pacemaker Stimulation in Patients With Implanted Cardioverter-Defibrillators

Background—We sought to determine the potential of right ventricular VVI backup pacing to induce ventricular tachyarrhythmias in patients with implanted cardioverter-defibrillators. Methods and Results—All consecutive patients presenting exclusively with pacemaker-induced tachycardias (PITs) were included in a prospective study using a crossover protocol. Patients were randomized to either group 1 (augmentation of the baseline frequency of the pacemaker to 60 bpm) or group 2 (pacemaker turned off) and were followed up for 1 year and then crossed over to the other programming, looking for reoccurrence of PIT. Of 150 consecutive patients, 39 (26%) had PIT, 13 of them exclusively (8.6%). Forty of 1063 analyzed tachyarrhythmias of all the patients were PIT (3%). Before inclusion in the study, the patients had 2.7±0.9 PITs in 11±6.5 months with their pacemakers programmed empirically at 42.3 bpm. During the study phase, no PIT occurred while the pacemaker was turned off, whereas programming to 60 bpm led to the recurrence of PIT in 5 of 6 patients (1.4±0.6 per patient). At the end of the study, 9 patients underwent a prolonged follow-up with their pacemakers turned off, resulting in spontaneous episodes of ventricular tachycardia/fibrillation in 5 patients, but PITs were no longer observed. Conclusions—This crossover protocol proves the potential proarrhythmic effect of pacemaker stimulation in implantable cardioverter-defibrillator patients. Resulting PITs led to clinical symptoms and antitachycardia therapy by the implantable cardioverter-defibrillator. Thus, in patients presenting with PIT but without a pacemaker indication, the pacemaker feature should be turned off, or, alternatively, the longest possible escape interval should be programmed.

IS THERE A RISK FOR INTERACTION BETWEEN MOBILE PHONES AND SINGLE LEAD VDD PACEMAKERS

Mobile phones may cause pacemaker interference. Patients with a single lead VDD pacemaker might be at special risk, since the atrial sensitivity is often programmed to low (high sensitivity) threshold values and the majority of patients are pacemaker dependent due to the underlying high degree AV block. We evaluated 31 patients with three types of single lead VDD pacemakers: 12 Unity, 292–07 (Intermedics, Inc.); 10 Thera VDD, 8948 or 8968i (Medtronic, Inc.); and 9 Saphir 600 (Vitatron, Inc.) for interference from a cellular mobile phone with a power of 2 W (D‐net). For this purpose, atrial and ventricular sensitivity settings were programmed to their most sensitive values (A: 0.1–0.25 mV; V: 1.0 mV) and ventricular sensing was programmed to unipolar. With the ECG continuously monitored, the phones extendable antenna was brought in direct contact with the patients skin at the right sternal border, with the tip of the antenna in skin contact just below the clavicle, within 5 cm of the pacemaker connector. Then multiple phases of phone calls were performed, and the effects on the pacemakers recorded. In our group of patients with three different types of single lead VDD pacemakers, no interference could be detected using a 2‐W mobile phone in the digital D‐net. The programmed values remained unchanged after the interference test. Therefore, the risk of interference seems to be low for the VDD pacemakers tested, although our study design does not allow to entirely exclude the possibility of interference from a mobile phone.

Verborgene intrakardiale Leitungsstörungen und deren spontaner Verlauf bei Patienten mit progressiver Muskeldystrophie

In patients with progressive muscular dystrophy (PMD) invasive electrophysiologic studies can detect hidden intracardiac conduction disturbances. The aim of this study was a long-term follow-up of these patients.    Twelve consecutive patients (9m, 3f, age 28±4 yrs) without cardiac symptoms and with normal echocardiographic findings were included in the study. They suffered from different stages of PMD type Erb (n=4), Becker-Kiener (n=4), Duchenne (n=2) and Landouzy-Déjerine (n=2). At the beginning of the study all patients underwent an invasive electrophysiologic study (EPS). The follow-up of 5.5 yrs included regular clinical visits, ECGs, and Holter recordings (every 3 months) as well as an echocardiography every 6 months. In 4 patients the EPS revealed a hidden interatrial conduction disturbance (AHRS-ACS 120±18ms), and in 10 pts an infrahisian conduction disturbance was found (HV max. 156±4ms). Conduction defects were seen independently from the type of PMD and the stage of the disease. During the follow-up the initially hidden interatrial conduction disturbance became evident in the surface ECG in 2 of 4 pts. One of them developed paroxysmal atrial fibrillation.    Five of 10 pts with an initially hidden infrahisian conduction disturbance developed an AV block grade I–III and in one case additionally a bundle branch block. Four of these pts – whose PMD showed progression or who developed congestive cardiomyopathy – needed pacemaker implantation because of a first-degree AV block + bifascicular bundle branch block (n=1), a Mobitz II second-degree AV block (n=1) or a third-degree AV block (n=2).    None of the pts with normal findings at the EPS showed abnormal p-waves, an AV block, or an intraventricular conduction disturbance during the follow-up.    We conclude that intracardiac conduction disturbances, especially infrahisian defects including high-degree AV blocks, are a common finding in pts with PMD. Therefore a regular cardiological screening including an ECG and a Holter recording is reasonable in these patients. Ziel dieser prospektiven Studie war die Beobachtung des spontanen Verlaufs invasiv dokumentierter verborgener intrakardialer Leitungsstörungen bei Patienten mit progressiver Muskeldystrophie (PMD).    12 konsekutive kardial asymptomatische und echokardiographisch unauffällige Patienten (9 Männer, 3 Frauen, Alter 28±4 J) mit PMD Typ Erb (n=4), Becker-Kiener (n=4), Duchenne (n=2) und Landouzy-Déjerine (n=2) mit unterschiedlichem Schweregrad der Muskelerkrankung wurden am Anfang der Studie invasiv elektrophysiologisch untersucht und im Langzeitverlauf über 5,5 Jahre klinisch und mittels EKG, Langzeit-EKG (alle 3 Monate) und Echokardiographie (alle 6 Monate) kontrolliert. Bei 4 Patienten (33%) wurde elektrophysiologisch eine verborgene interatriale Leitungsstörung (AHRA-ACS von 120±18ms) und bei 10 Patienten (83%) eine infrahissäre Leitungsstörung (HV maximal 156±54ms) gesichert. Intrakardiale Leitungsstörungen waren bei jeder PMD-Form und jedem PMD-Schweregrad nachzuweisen. Im Follow-up entwickelte sich bei 2 von 4 Patienten aus einer zunächst verborgenen eine im EKG manifeste interatriale Leitungsstörung, wobei bei 1 Patienten auch ein paroxysmales Vorhofflimmern auftrat. Bei 5 von 10 Patienten mit initial verborgener infrahissärer Leitungsstörung war im Langzeitverlauf ein AV-Block I-III Grades und außerdem ein Schenkelblock zu beobachten. 4 von diesen 5 Patienten, die auch entweder eine dilatative Kardiomyopathie oder eine Progredienz der Muskelerkrankung aufwiesen, wurde wegen eines AVB I° und bifaszikulären Blocks (n=1), AVB II° Typ Mobitz (n=1) oder AVB III° (n=2) ein Schrittmacher implantiert.    Bei keinem der Patienten mit normalem elektrophysiologischem Befund konnte im Follow-up eine verbreiterte P-Welle, ein AV-Block oder eine intraventrikuläre Leitungsstörung dokumentiert werden.    Somit sind intrakardiale, vor allem infrahissäre Leitungsstörungen bis hin zum höhergradigen AV-Block, bei Patienten mit progressiver Muskeldystrophie ein häufiger Befund. Diese Patienten sollten daher mittels regelmäßiger EKG- und Langzeit-EKG-Kontrollen auch von Kardiologen beobachtet werden.

How Reliable is Atrial Sensing in Single-Lead VDD Pacing: Comparison of Three Systems

This study evaluated the reliability of atrial sensing, expressed as AV synchronous stimulation, in three VDD systems with the atrial sensitivity (AS) programmed to a conventional value with a 2:1 safety margin compared to most‐sensitive values. We studied 34 sex‐ and age‐matched patients with 3 VDD systems: 14 with Unity 292–07, 10 with Saphir 600, and 10 with Thera VDD (5 model 8948 and 5 model 8968i). Two 24‐hour Hollers were performed on consecutive days. The AS was programmed in a randomized order to its most‐sensitive value or to a 2:1 safety margin. All other parameters were programmed identically. The patients underwent a myopotential oversensing test and a daily life activity protocol. A beat‐to‐beat analysis of the Holters was performed to determine AV synchrony. For the entire group AV synchrony with conventional AS was 98.63%± 2.57%, compared to 99.80%± 0.43% with most‐sensitive values (p = 0.002). There was no difference between the three systems with conventional AS. With the most‐sensitive AS, AV synchrony was: Unity 99.99%± 0.03%, Saphir 99.42%± 0.60% (P = 0.002), Thera 99.81 %± 0.35% (ns). In the Saphir system with an atrial blanking period of 150 ms, ventricular far‐field sensing could be demonstrated in 5 of 10 patients. This reduced the percentage of AV synchrony due to an unwanted mode‐switch to a nontracking mode. Myopotential oversensing was not detected in any patient. Conclusion: The VDD systems tested under identical conditions showed reliable P wave sensing at the most‐sensitive atrial sensing setting without myopotential oversensing. Ventricular far‐field sensing reduced AV synchrony and must be avoided by appropriate refractory periods.

Holter Recordings with Continuous Marker Annotations: A New Tool in Pacemaker Diagnostics

Pacemakers provide marker annotations to facilitate the interpretation of pacemaker electrocardiograms (ECGs) and can be used in cases of suspected pacemaker malfunction or to understand pacemaker behavior. Due to the need for a programmer, only short‐term evaluations are possible. We evaluated a prototype Telemetry Data Logger (TDL) designed to continuously transfer markers from the pacemaker to a conventional Holter recorder. A miniaturized telemetry receiving coil was attached to patients skin above the pacemaker, which was programmed to transmit markers continuously. The TDL, which receives and converts markers into eight positive and eight negative deflections, ranging from ‐2.5 to +2.5 mV in amplitude, was connected to one channel of a conventional Holter recorder (Tracker 2). We performed 20 Holters in 13 patients who had implanted VDDB or DDDR devices from the same manufacturer and evaluated three versions of software. Marker transmission was possible in all patients, producing Holter ECGs with complete marker annotations. Artifacts occurred < 4 % of the time. A 50‐ms rectangular pulse was optimal for marker interpretation. The device, which was easy to use and well accepted by the patients, assisted in the diagnosis of inappropriate pacemaker programming, even when the surface ECG seemed to show regular pacemaker function. In the presence of low quality surface ECGs, marker annotations allowed the assessment of pacemaker function. The capability to annotate the onset of special algorithms, like tachycardia termination algorithms or mode switching, facilitates interpretation of pacemaker behavior, enabling a reliable assessment of the appropriateness of such algorithms. Conclusion: The TDL effectively enables pacemaker markers to be inscribed onto a conventional Holter recording, facilitating the interpretation of pacemaker ECGs and the diagnosis of inappropriate pacemaker programming even when not discernible from the surface ECG alone.

An welcher Stelle soll ein implantierbarer EKG-Event-Recorder plaziert werden?

Aim of our study was the comparison of bipolar ECG quality (with a 4cm lead distance) at different sites within the anterior thorax to find the preferable implantation site for an ECG event recorder (ECG-ER). In 70 patients a bipolar ECG with a short electrode distance and in the vertical position was registered at the following sites: left and right subclavicular, left and right parasternal (4th–5th ICR), left and right anterior axillar (4th–5th ICR), at the heart apex and subxiphoidal. Then it was compared to the standard lead II. In 34 patients, an additional comparison between vertical and horizontal ECG registration was performed at the above mentioned sites. During implantation of an ECG-ER in 5 patients, ECG signals were compared with electrodes placed towards the skin or towards the muscle. The best ECG quality (greatest QRS amplitude, visible P-wave and pacemaker spike, measurable QT period and bundle-branch block) and the best agreement with standard lead II was found in 67% left parasternal, significant less often (p<0.001) right parasternal (14.3%), left subclavicular (7.1%), apical (5.7%), and subxiphoidal (4.3%). In a vertical electrode position a significantly higher QRS amplitude and a more often visible P wave was found in comparison to a horizontal electrode position. In all cases, there was good agreement between bipolar surface ECG at the implantation site and ECG-ER stored signals. When the ECG-ER is positioned with electrodes towards the muscle, significant noise-signal occurred in all 5 patients. Only in 3 patients was a P wave visible, but with a slightly greater QRS amplitude than in ECG-ERs positioned with electrodes towards the skin. From these results, it is recommended to implant ECG-ERs vertically with electrodes towards the skin and in the parasternal position. Ziel dieser Untersuchung war der Vergleich der EKG-Qualität an verschiedenen Stellen des vorderen Thorax bei einer bipolaren Ableitung mit einem Elektrodenabstand von 4 cm. Bei 70 Patienten (Mittleres Alter 48±7 J, 36 Männer, 22 Übergewicht, 17 Untergewicht, 57 Sinusrhythmus oder AAI-Stimulation, 27 Schenkelblock, 22 davon VVI oder VAT-Stimulation) wurde ein bipolares EKG mit kurzem Elektrodenabstand links und rechts subclaviculär, links und rechts parasternal (4.–5. ICR), im Bereich der linken und rechten anterioren Axillarlinie (4.–5. ICR), im Bereich der Herzspitze und subxiphoidal bei vertikaler Anlage der Elektroden registriert und mit der Standardableitung II verglichen. In 34 Fällen ist zudem zum Vergleich das EKG an o.g. Stellen sowohl bei vertikaler als auch bei horizontaler Anlage der Elektroden dokumentiert worden. Während der Implantation eines EKG-Event-Recorders (EKG-ER) bei 5 Patienten wurde ein EKG bei Plazierung des Gerätes mit den Elektroden zur Haut und zum Muskel aufgezeichnet und die Signale verglichen. Die beste EKG-Qualität (größte QRS-Amplitude, sichtbare P-Welle und SM-Impuls, meßbare QT-Zeit und Schenkelblockmorphologie) und Übereinstimmung mit dem Standard-EKG wurde in 67% der Fälle links parasternal, viel seltener (p<0,001) rechts parasternal (14,3%), links subclaviculär (7,1%), im Bereich der Herzspitze (5,7%) und subxiphoidal (4,3%) erzielt. Bei vertikaler Anlage der Elektroden konnte eine signifikant größere QRS-Amplitude und in den parasternalen Ableitungen viel häufiger eine P-Welle im Vergleich zur horizontalen Anlage der Elektroden dokumentiert werden. Diese Ergebnisse waren unabhängig vom Körpergewicht. Das bipolare Oberflächen-EKG am Implantationsort stimmte in allen Fällen mit den vom implantierten EKG-ER aufgezeichneten Signalen sehr gut überein. Bei Plazierung des EKG-ER mit den Elektroden zum Muskel wurde bei jedem der 5 Patienten ein deutliches Störsignal und nur in 3 Fällen eine sichtbare P-Welle, jedoch eine etwas größere QRS-Amplitude im Vergleich zu der Plazierung des Gerätes mit den Elektroden zur Haut registriert. Aufgrund dieser Ergebnisse sollte EKG-Event-Rekorder vertikal, mit den Elektroden zur Haut und in der Regel parasternal implantiert werden.

Is Atrial Sensing of Ventricular Far-Field Signals Important in Single-Lead VDD Pacing?

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.

Paroxysmal Atrial Fibrillation and High Degree AV Block: Use of Single-Lead VDDR Pacing with Mode Switching

Dual chamber rate responsive pacing incorporating a mode switching option is increasingly listed in patients with chronic paroxysmal atrial fibrillation and high degree AV block. Single‐lead VDDR pacemakers have been rarely used for this indication. The purpose of this study was to determine thnir reliability of atrial sensing during atrial fibrillation, the percentage of at rial synchronous ventricular pacing, and the behavior of the sinus rate outside the phases of atrial fibrillation. We studied ten patients with a single‐lead VDDR pacemaker implanted for this indication. Follow‐up visits were performed at predischarge and after 1, 3, 6, 12. 18, and 24 months. During the mean follow‐up period of 18.9 ± 6.9 months, the atrial sensing thresholds in sinus rhythm remained stable. Atrial synchronous ventricular stimulation was achieved in 68,7 ±31.2% (median 82.5%) of the whole follow‐up time. All patients showed an adequate atrial rate response during sin us rhfthm. Atrial fibrillation was detected by the pacemakers in 24.0 ± 29.8% of time. In 3 of 10 patients the duration of atrial fibrillation showed a steady increase from visit to visit. The sensed amplitudes of atrial fibrillation ranged from 0.1–1.0 mV. A programmed atrial sensitivity of 0.1 mV was necessary to achieve complete sensing of atrial fibrillation. None of the patients experienced tachycardias with optimized pacemaker programming. Single‐lead VDDR pacing incorporating a mode‐switching option is useful in patients with high degree AV block and paroxysmal atrial fibrillation, since it provides atrial synchronous ventricular pacing in more than two‐thirds of follow‐up time. In a subgroup of patients, a progressive increase of the time during atrial fibrillation was demonstrated. A reliable detection of paroxysmal atrial fibrillation requires the programming of the atrial sensitivity to its most sensitive value.

Die prognostische Bedeutung der Herzfrequenzvariabilitätsanalyse bei Patienten mit dilatativer Kardiomyopathie

Der plötzliche Herztod ist eine der Haupttodesursachen bei Patienten mit dilatativer Kardiomyopathie. Die Abschätzung des individuellen Arrhythmierisikos ist hingegen nach wie vor schwierig. Die Analyse der Herzfrequenzvariabilität bietet hierbei einen neuen Ansatzpunkt. Methodik: 25 Patienten (18 Männer, 7 Frauen, Alter 53±9 J.) mit dilatativer Kardiomyopathie wurden untersucht. Die Analyse der Herzfrequenzvariabilität wurde durch Auswertung von Langzeit-EKG-Bändern im Zeit- und Frequenzbereich durchgeführt. Der anschließende Beobachtungszeitraum betrug 18±5 Monate. Ergebnis: 6 der Patienten verstarben (5× plötzlicher Herztod, 1× Pumpversagen), 1 Patient mit implantiertem Defibrillator erhielt einen lebensrettenden Schock. Patienten mit letaler Arrhythmie bzw. Schockereignis (n=6) wiesen in den Parametern, die durch niedrig- bis mittelfrequente Schwingungen der Herzfrequenz beeinflußt werden, signifikant niedrigere Werte auf als die anderen Patienten (n=19). Insbesondere war der Parameter s.d.RR geeignet, eine Hochrisikogruppe zu erkennen. Alle Patienten mit plötzlichem Herztod/ICD-Schock wiesen eine s.d.RR <50 ms auf, die anderen Patienten hingegen lagen alle oberhalb dieses Grenzwertes. Kein signifikanter Unterschied zeigte sich bei den hochfrequenten, parasympathisch dominierten Patienten. Schlußfolgerung: Die Bestimmung der Herzfrequenzvariabilität ist bei Patienten mit dilatativer Kardiomyopathie von prognostischer Bedeutung. Die s.d.RR ist besonders geeignet, ein Risikokollektiv zu erkennen. Sudden cardiac death is frequent in patients with dilated cardiomyopathy. To assess the risk of an arrhythmic event is still difficult. Here the analysis of the heart rate variability offers new possibilities. Method: 25 patients (18 male, 7 female, age 53±9 yrs) with dilated cardiomyopathy were included in the study. Analysis of heart rate variability assessed by time- and frequencydomain measures was determined from Holter recordings. The mean follow-up was 18±5 months. Results: 6 patients died (5 of sudden cardiac death, 1 of heart failure), 1 patient with an implanted defibrillator received an adequate shock. Parameters influenced by low- and midfrequent oscillations of the heart rate were significantly lower in patients who died suddenly or had adequate shocks. The best predictive parameter was the s.d.RR: all patients with an s.d.RR <50 ms had lethal arrhythmias whereas the s.d.RR of the surviving patients was ≥50 ms. No significant difference was found for highfrequency parameters, which are mainly influenced by parasympathetic activity. Conclusion: The analysis of heart rate variability is of prognostic relevance in patients with dilated cardiomyopathy. Especially the s.d.RR is able to identify patients with a high risk of a sudden cardiac death.

Is there a risk for interactions between mobile phones and single-lead VDD pacemakers?

Mobile phones may cause pacemaker interference. Patients with a single lead VDD pacemaker might be at special risk, since the atrial sensitivity is often programmed to low (high sensitivity) threshold values and the majority of patients are pacemaker dependent due to the underlying high degree AV block. We evaluated 31 patients with three types of single lead VDD pacemakers: 12 Unity, 292-07 (Intermedics, Inc.); 10 Thera VDD, 8948 or 8968i (Medtronic, Inc.); and 9 Saphir 600 (Vitatron, Inc.) for interference from a cellular mobile phone with a power of 2 W (D-net). For this purpose, atrial and ventricular sensitivity settings were programmed to their most sensitive values (A: 0.1-0.25 mV; V: 1.0 mV) and ventricular sensing was programmed to unipolar. With the ECG continuously monitored, the phones extendable antenna was brought in direct contact with the patients skin at the right sternal border, with the tip of the antenna in skin contact just below the clavicle, within 5 cm of the pacemaker connector. Then multiple phases of phone calls were performed, and the effects on the pacemakers recorded. In our group of patients with three different types of single lead VDD pacemakers, no interference could be detected using a 2-W mobile phone in the digital D-net. The programmed values remained unchanged after the interference test. Therefore, the risk of interference seems to be low for the VDD pacemakers tested, although our study design does not allow to entirely exclude the possibility of interference from a mobile phone.