How can we identify the best implantation site for an ECG event recorder?

The aim of this study was to show how to find the preferable implantation site for an ECG event recorder (ECG-ER). We compared the quality of bipolar ECG recordings (4-cm electrode distance, vertical position) in 65 patients at the following sites: left and right subclavicular, left and right anterior axillary line (4th-5th interspace), left and right of the sternum (4th-5th interspace), heart apex, and subxyphoidal. The results were compared to the standard ECG lead II. In 30 patients, an additional comparison between vertical and horizontal ECG registrations was done using the same sites. ECG signals in five patients were compared positioning the electrodes towards the skin with turning them towards the muscle during ECG-ER implantation. The best ECG quality (defined as highest QRS amplitude, best visible P wave and/or pacemaker spike, best measurable QRS duration, and QT interval) and best agreement with the standard lead II was found in 68% on the left of the sternum, significantly less often (P < 0.001) on the right of the sternum (14.1%), left subclavicular (6.9%), apical (5.5%) and subxyphoidal (4.2%). A significantly higher QRS amplitude was measured and the P wave was more often visible in the vertical electrode position than in the horizontal position. In all five ECG-ER patients, there was a good agreement between the bipolar surface ECG at the implantation site and ECG-ER stored signals. A significant noise signal occurred in all five patients when the ECG-ER was implanted with electrodes towards the muscle. A P wave was visible in only three of those patients, but there was an insignificantly higher QRS amplitude than in ECG-ERs implanted with electrodes towards the skin. From these results, it can be concluded that the best implantation site for an ECG-ER is right or left of the sternum, positioning the electrodes vertically and towards the skin.

[Hidden intracardiac conduction disturbances and their spontaneous course in patients with progressive muscular dystrophy]. / 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 (9 m, 3 f, 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 +/- 18 ms), and in 10 pts an infrahisian conduction disturbance was found (HV max. 156 +/- 4 ms). 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.

[Where should the implantable ECG event recorder be placed?]. / An welcher Stelle soll ein implantierbarer EKG-Event-Recorder plaziert werden?

Aim of our study was the comparison of bipolar ECG quality (with a 4 cm 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 axilla (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.

[Is ICD-programming for double intraoperative defibrillation threshold energy safe and effective during long-time follow-up? Results of a prospective randomized multicenter study (Low-Energy Endotak Trial--LEET)]. / Ist eine ICD-Programmierung auf eine Schockenergie der doppelten intraoperativen Defibrillationsschwelle im Langzeitverlauf sicher effektiv? Ergebnisse einer prospektiven randomisierten Multizenterstudie (Low Energy Endotak Trial-LEET).

The aim of this prospective and randomized study was to evaluate the safety and efficacy of a reduced shock strength in transvenous implantable defibrillator therapy. So far clinical data concerning the safety margin of the shock energy in ICD therapy do not exist. The shock energy tested during long-term follow-up in this study was twice the intraoperatively measured defibrillation threshold (DFT). A total number of 176 consecutive patients representing a typical cohort of ICD patients were evaluated. All patients received a non-thoracotomy lead system (CPI, Endotak 0070, 0090) and a biphasic cardioverter-defibrillator with the ability to store episodes (Cardiac Pacemakers Inc., Ventac TM PRx II, PRx III). The intraoperative defibrillation threshold (DFT) was evaluated in a step-down protocol (15, 10, 8, 5 J) and had to be < or = 15 J for inclusion into the study. The lowest effective energy terminating induced ventricular fibrillation had to be confirmed and was defined as DFT+ augmented defibrillation threshold. The DFT+ value was tested immediately after successful implantation, at discharge, and after a follow-up period of one year. Prior to implantation the patients were randomized into two groups. The energy of the first shock in the study group was programmed at twice DFT+ and in the control group at the maximum energy output (34 J). The efficacy of the first shock and its reproducibility in DFT testings and in spontaneous episodes during long-term follow-up of the study group were compared to those in the control group. A DFT+ value was found to be < or = 15 J in 166 of 176 patients (94%). The DFT+ in the study group was 9.6 +/- 3.2; in control group 10.1 +/- 3.5 J. The prohability of successful defibrillation at DFT+ level after one year was 84%. The success rate of the first shock meant to terminate induced ventricular fibrillation (VF) was 99.5% in the study group (217 of 218 episodes) and 99% in the control group (201 of 203 episodes). During follow-up of 24 +/- 9 months spontaneous episodes in the study group, 83/86 (96.5%) monomorphic ventricular tachycardias (MVT) and 38/40 (95%) VF-episodes were converted successfully by the 2x DFT+ shock. In the control group the first shock was successful in 151/156 (96.8%) spontaneous MVTs and in 30/33 (91%) VF episodes. The efficacy of the first shock was not influenced by clinical data such as the underlying cardiac disease, left ventricular function, ongoing antiarrhythmic therapy with amiodarone, or the number of spontaneous episodes per day or by the DFT itself. At a mean follow-up of two years there was no significant difference between the two groups concerning the incidence of sudden cardiac death (2.4% in the study group vs. 3.8% in the control group). In conclusion programming the first shock with the ICD lead system used in this study at 2x DFT+ is as efficient as a shock energy of 34 J in order to terminate induced and spontaneous episodes of VT/VF. Thus, the safety of ICD-therapy is not impaired when programming the shock energy at the 2x DFT+ value.

Safety and efficacy of implantable defibrillator therapy with programmed shock energy at twice the augmented step-down defibrillation threshold: results of the prospective, randomized, multicenter Low-Energy Endotak Trial.

Whether the safety and efficacy of implantable cardioverter defibrillator (ICD) therapy can be assured with lower output devices is an important question. The purpose of this study was to evaluate whether programming the device output at twice the augmented defibrillation threshold was as safe and effective as using the maximum energy. Patients indicated for ICD therapy, but without slow monomorphic ventricular tachycardia (MVT), who achieved an augmented defibrillation threshold (DFT plus) < or = 15 joules (J) with a single endocardial lead system and a biphasic defibrillator were included in the study. Prior to ICD implantation, patients were randomized into 2 groups. The shock energies in test group patient were set as follows: first shock at twice DFT plus, the second to fifth shocks at maximum output (34 J). In control group patients, all shocks were programmed at 34 J. The study population consisted of 166 consecutive patients (mean age 57.4 +/- 12.1 years, mean left ventricular ejection fraction 36.8 +/- 13.8%). Mean DFT plus was 9.6 +/- 3.2 J in test group patients and 10.1 +/- 3.5 J in control group patients (p = 0.36). During a mean follow-up of 24.2 +/- 9.6 months, 736 arrhythmia episodes were analyzed. The first shock efficacy was 98.3% in the test group patients versus 97.4% in the control group (p = 0.45). Total mortality was 6%, equally distributed in both study groups. The results of this study prove that the method of doubling the defibrillation energy at the DFT plus level provides an adequate safety margin in defibrillator therapy.

How reliable is atrial sensing in single-lead VDD pacing: comparison of three systems.

UNLABELLED: 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 Holters 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.

Is atrial sensing of ventricular far-field signals important in single-lead VDD pacing?

UNLABELLED: 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 used in patients with chronic paroxysmal atrial fibrillation and high degree AV block. Single-lead VDDR pacemakers have rarely used for this indication. The purpose of this study was to determine their reliability of atrial sensing during atrial fibrillation, the percentage of atrial 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 sinus rhythm. 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.

[Prognostic significance of analysis of heart rate variability inpatients with dilated cardiomyopathy]. / Die prognostische Bedeutung der Herzfrequenzvariabilitätsanalyse bei Patieten mit dilatativer Kardiomyopathie.

UNLABELLED: 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 males, 7 females, age 53 +/- 9 yrs) with dilated cardiomyopathy were included in the study. Analysis of heart rate variability assessed by time- and frequency-domain measures was determined from Holter recording. 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 mid-frequent 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 > or = 50 ms. No significant difference was found or high frequency 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.

[New aspects of electric defibrillation]. / Neue Aspekte der elektrischen Defibrillation.

Early defibrillation is the standard of care for patients with ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT). Technical developments aim at further miniaturization and simplification of defibrillators as well as adaptation of energy requirements to the patient's needs. Implantable Cardioverter-Defibrillators (ICD) and automated external defibrillators (AED) are based upon the same technology. Both devices analyze the ECG signal internally, followed by a "shock" or "no shock" decision. Use of automated devices is the prerequisite for defibrillation by non-physicians. Chest impedance measurements and use of alternative shock waveforms, such as biphasic, aim at adaptation of energy or current to the patient's individual needs and avoid application of unnecessarily high amounts of energy to the myocardium. Calculation of median frequency is a non-invasive method for analyzing the heart's metabolic and electrical state. It helps to determine the optimal moment for defibrillation during cardiopulmonary resuscitation (CPR). Developments concerning the structure of in-hospital emergency systems or pre-hospital emergency medical services (EMS) aim at further reductions in time from collapse of a patient until first defibrillation. Such developments include early defibrillation programs for emergency medical technicians (EMT), nurses, and fire or police department first responders as well as wide distribution of easy-to-operate defibrillators in public areas, as discussed during the American Heart Association's Public Access Defibrillation conferences. All programs of that kind have to be organized and supervised by a physician who is responsible for training and supervision of the personnel involved.

[Reproducibility of the effectiveness of defibrillation for terminating induced ventricular fibrillation using intraoperatively measured defibrillation threshold energy in patients with implanted cardioverter-defibrillator]. / Reproduzierbarkeit der Defibrillationseffektivität zur Terminierung von induziertem Kammerflimmern unter Verwendung der intraoperativ gemessenen Defibrillationsschwellenenergie bei Patienten mit implantierbarem Kardioverter-Defibrillator.

The aim of the present study was to assess the long-term reproducibility of the defibrillation efficacy of energies set at the intraoperatively measured defibrillation threshold using a modified testing protocol. Between December 1993 and January 1996, 83 patients receiving an implantable cardioverter-defibrillator (ICD) in combination with a non-thoracotomy lead system and having an intraoperatively measured defibrillation threshold (DFT) < or = 15 J were enrolled in a substudy of a prospective, randomized multicenter trial ("Low Energy Endotak Trial" (LEET)). Step-down DFT testing was performed intraoperatively (15, 10, 8, 5 J). It was mandatory to reproduce a successful conversion of ventricular fibrillation at the DFT energy during implantation (DFT+). At the end of implantation, at predischarge, and after one year, assessment of the defibrillation efficacy of DFT+ energy was repeated (first shock: DFT+, second shock: 2 x DFT+). Mean DFT+ at implant was 9.6 + 3.3 J. Immediately after implantation, successful conversion of induced ventricular fibrillation was achieved in 70/79 (89%) patients using DFT+ energies. In 7/8 (89%) patients only the second shock set at 2 x DFT+ and in one patient only the third shock set at maximum energy (34 J) was successful. At predischarge, defibrillation efficacy of DFT+ was reproducible in 61/77 (79%) patients. The remaining 16 patients were successfully converted using a second shock set at 2 x DFT+. One year after implantation, conversion of ventricular fibrillation was achieved at energies set at DFT+ in 52/62 (84%) patients and in the remaining 10 patients at energies set at 2 x DFT+. A total of 183/218 (84%) episodes of induced ventricular fibrillation were terminated successfully using DFT+ energies. There was no correlation between the intraoperatively determined DFT+ or the underlying cardiac disease and the defibrillation efficacy. These results demonstrate that the defibrillation efficacy for termination of induced ventricular fibrillation using DFT+ energies is reproducible at implantation, at predischarge, and one year after ICD insertion. Energies set at twice DFT+ seems to allow for reliable defibrillation within the first year after ICD implantation.

Implantable cardioverter-defibrillator therapy: influence of left ventricular function on long-term results.

The degree of left ventricular impairment in an acknowledged important prognostic marker of long-term outcome for patients being evaluated for implantation of cardioverter-defibrillators. Just how left ventricular function impacts freedom from all-cause mortality, as well as from sudden death and cardiac death, is a subject of current major debate, and is analyzed hereunder from a large, recent multicenter ICD patient cohort. The multicenter database consists of data from 361 patients receiving implantable cardioverter-defibrillators for standard indications, that is, documented episodes of ventricular fibrillation or sustained ventricular tachycardias with poor hemodynamic toleration. Data were collected from 1988 to 1995 at three centers in Germany. Two-hundred and three patients (56%) had a left ventricular ejection fraction (LVEF) > 0.30 (group I), and 158 patients (44%) had a LVEF < or = 0.30 respectively (group II). The mean follow-up was 23.9 months (range 3-98 months). Overall survival at 5 years for group II patients was lower, as expected, at 74.1% versus 94.2%, respectively (P < 0.0001). Mortality was higher for each different cause of death in group II patients than in Group I: sudden arrhythmic deaths, 5 versus 1 (P < 0.048); nonsudden cardiac deaths, 16 versus 5 (P < 0.002); noncardiac deaths, 7 versus 2 (P < 0.03). Group II patients received a higher rate of at least one presumably appropriate shock at 86 (54.4%) versus 89 (43.8%) in group I (P < 0.05). However (and somewhat surprisingly), neither the time from ICD implantation to death, comparing only the patients who died, nor the event-free probability of appropriate shocks due to very rapid, sustained ventricular arrhythmias (> 230 beats/min), including a presumed risk of sudden arrhythmogenic death, differed between groups I and II. Sudden cardiac death was only marginally affected by LVEF (group I, 1.5% actuarial, 5-year survival 99.5%; group II, 3.1% and 95.8%, respectively). Therefore, the lower overall survival in ICD patients with LVEF < or = 0.30 resulted mainly from causes of death that cannot be directly influenced by cardioverter-defibrillator therapy. However, because group II patients had a far higher incidence of at least one ventricular tachyarrhythmia terminated by ICD shocks than group I patients, they also probably derived benefit from ICD therapy.

[Late potentials in the diagnosis of post-infarction patients: arrhythmogenic risk and clinical symptomatology]. / Die Spätpotentialanalyse in der Diagnostik nach akutem Myokardinfarkt: Risikomarker für den Arrhythmie-gefährdeten und klinisch symptomatischen Patienten.

A prospective study was performed of the correlation of ventricular late potentials (LP) and clinical parameters in patients after acute myocardial infarction. To evaluate the prognostic significance of the signal-averaged-electrocardiogram (SAECG) in risk stratification of sudden cardiac death and arrhythmogenic events, the clinical characteristics of these post-infarction patients were performed in a follow-up-period. 243 consecutive patients underwent SAECG for detection of late potentials in the second week after acute myocardial infarction. After a mean follow-up of 9 months the patients were asked a standardized questionnaire. Late potentials are independent of age, sex, left ventricular ejection fraction, peak activity of MB fraction of creatine kinase, and the cardiovascular risk factors in postinfarction patients. In patients, who received thrombolytic therapy, the incidence of late potentials is lower (p < 0.05) and in patients with posterior wall infarction it is significantly higher (p < 0.04). In the follow-up period patients with abnormal SAECG show a significantly higher rate of angina pectoris, palpitations, dizziness, and syncope. By way of contrast, postinfarction patients with normal SAECG feel mainly comfortable in the follow-up (p < 0.01). The mortality was even in both groups. Sudden cardiac death in the late postinfarction period shows a significant correlation with the finding of late potentials in SAECG in the early myocardial infarction period (p < 0.01). The SAECG for detection of late potentials as a non-invasive investigation in the early postinfarction period characterizes patients with an arrhythmogenic risk, especially sudden cardiac death, independent of other conventional methods. Furthermore, the impaired patient with clinical symptoms in the late postinfarction period is hereby identified.

Holter recordings with continuous marker annotations: a new tool in pacemaker diagnostics.

UNLABELLED: 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 patient's 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 VDDR 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.

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 phone's extendable antenna was brought in direct contact with the patient's 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.

A simple method for preoperative assessment of the best fitting electrode length in single lead VDD pacing.

For single lead VDD pacing, electrodes with various distances between the lead tip and the floating atrial dipole (AV distance) are available. Using different AV distances allows positioning of the atrial dipole in the mid- to high right atrium, regardless of the size of the right heart. In this position, reliable atrial sensing and rejection of ventricular far-field potentials can be expected. A simple test for the preoperative assessment of the best fitting AV distance in the individual patient was tested. We studied 24 consecutive patients prior to implantation of a VDD pacemaker. With the patient in supine position, a test electrode with an AV distance of 13 cm was taped onto the thorax. Under fluoroscopic control, it was moved until its course and projection onto the heart was equal to that of a ventricular lead. If fluoroscopy then showed a projection of the atrial dipole onto the mid- to high right atrium, a lead with a similar AV distance of 13 or 13.5 cm was used for implantation. If the atrial dipole projected itself too high or too low, a shorter or longer lead had to be implanted. The maximum time for the test was 2 minutes, and the maximum fluoroscopy time was 15 seconds. According to the test, a lead with an AV distance of 13 or 13.5 cm was implanted in 18 of 24 patients, and a lead with an AV distance of 15.5 or 16 cm was implanted in 6 of 24 patients. The atrial dipole could easily be positioned in the mid- to high right atrium in all patients, demonstrating a correct preoperative assessment of the best fitting AV distance. Intraoperatively, a P wave amplitude of 3.5 +/- 3.0 mV was measured. The described test allows a fast and reliable assessment of the best fitting electrode length in single lead VDD pacing.

[DDD versus DDDR pacemaker stimulation: comparison of cardiopulmonary performance, incidence of atrial arrhythmias and quality of life]. / DDD- versus DDDR-Schrittmacherstimulation: Vergleich der kardiopulmonalen Leistungsfähigkeit, der Häufigkeit von Vorhofarrhythmien und der Lebensqualität.

The purpose of this study was to assess cardiopulmonary exercise capacity, variation in heart rate during everyday activities, frequency of atrial arrhythmias and quality-of-life during accelerometer-based rate modulated dual-chamber pacing. Nine chronotropically incompetent and 14 chronotropically competent patients (mean age 51 years) were randomly assigned to DDD and DDDR mode and evaluated by a semisupine bicycle exercise testing exceeding the anaerobic threshold, 24-h Holter monitoring and a quality-of-life questionnaire. In the subgroup of patients with chronotropic incompetence, defined by a HR/VO2-ration, 2 beats/ml/kg, during DDDR pacing, compared to DDD, maximum heart rate increased from 83 +/- 13 to 132 +/- 7 beats/min (p < 0.01), maximum oxygen uptake from 12.7 +/- 3.1 to 15.3 +/- 3.2 ml/kg/min ( p < 0.05) and the VO2/WR-ratio from 8.1 +/- 1.0 to 9.0 +/- 0.9 ml/min/watts (p < 0.05). Exercise duration lengthened from 252 +/- 59 to 301 +/- 96 s (p < 0.05). During the 24-h Holter recordings the average maximum heart rate rose form 69 +/- 7 in the DDD mode to 78 +/- 9 beats/min in the DDDR mode significantly (p < 0.05). DDDR pacing did not result in an increased number of atrial salvos (2.6 atrial events/24 h) when compared to DDD pacing (2.5 atrial events/24 h, N.S.). These objective results were confirmed by the quality-of life assessment due to a symptom questionnaire. The symptom score declined from 20 +/- 10 in the DDD mode to 16 +/- 7 in the DDDR mode (p < 0.01). In the patients with chronotropic competence, however, cardiopulmonary exercise capacity did not improve in the DDDR mode: maximum heart rate was 120 +/- 21 versus 130 +/- 24 beats/min (N.S.), maximum oxygen uptake 17.7 +/- 5.9 versus 16.8 +/- 5.9 ml/kg/min (N.S.), The VO2/WR-ratio 9.8 +/- 2.3 versus 9.2 +/- 2.5 ml/min/watts (N.S.) and the exercise duration 407 +/- 159 versus 406 +/- 165 s (N.S.). The average maximum heart rate was 80 +/- 15 in the DDD mode and 83 +/- 16 beats/min in the DDDR mode (N.S.). Significantly more atrial arrhythmias occurred in the DDDR pacing mode: 1.6 atrial salvos per 24 h in the DDD mode versus 4.8 atrial salvos per 24 h in the DDDR mode (p < 0.05). This patient subgroup experienced a significant worsening of his quality-of-life. The symptom score rose from 20 +/- 9 in the DDD mode to 28 +/- 11 in the DDDR mode (p < 0.05). In conclusion, DDDR pacing improved cardiopulmonary exercise capacity, normalized heart rate variation over 24 h and increased quality-of-life in patients with chronotropic incompetence. On the contrary, since the DDDR pacing more could not improve cardiopulmonary exercise capacity, increased atrial arrhythmias and worsened the patient's quality-of-life, patients with chronotropic competence should not be programmed in the DDDR pacing mode.

[Results of radiologic follow-up of patients with automatic implantable cardioverter-defibrillators]. / Ergebnisse der radiologischen Nackontrolle von Patienten mit automatischen implantierbaren Kardioverter-Defibrillatoren (AICD).

In the follow-up of patients with automatic implanted cardioverter defibrillators (AICD), the serial radiographs give us important information concerning the cardiac function, signs of cardiac insufficiency may be a first sign of a dysfunction of the implanted aggregate or of the system of electrodes. Not only the short term but also the radiographs over a long period of time are important. The estimation of the correct positions of the electrodes is important too, for dislocation or disconnection of the electrodes lead to a misfunction of the AICD. On the other hand a kinging or a disconnection of the marker-stripe of plain-surfaced electrodes needs no correction for they do not lead to a misfunctioning AICD. Beside the serial radiographs, radioscopy is important because a disconnection of the electrodes often is not visible except by radiography.