[Device therapy after acute coronary syndrome]. / Device-Therapie nach akutem Koronarsyndrom.

Acute coronary syndromes are seldom accompanied by high degree AV blocks. Implantation of a permanent pacemaker is rarely necessary.There is a high incidence of ventricular tachyarrhythmias during the acute phase of myocardial infarctions. Sustained VT or VF beyond 48 hours of the infarction indicate the need for an implantable cardioverter-defibrillator. If left ventricular ejecion fraction remains ≤35 % for >40 days an ICD might be indicated for primary prophylaxis.If early after infarction a device implantation becomes necessary, biventricular stimulation should be used if ventricular pacing is necessary or LBBB with markedly increased QRS-duration is present.

Effect of the atrial blanking time on the detection of atrial fibrillation in dual chamber pacing.

Patients with paroxysmal atrial fibrillation (PAF) and dual chamber pacemakers frequently have short postventricular atrial blanking times and sensitive atrial sensing thresholds used to provide reliable detection and mode switching during AF. However, short atrial blanking times increase the risk of atrial sensing of ventricular far-field signals. We evaluated if the length of the atrial blanking time influences the detection of AF. The study included ten patients with a VDDR (n = 7) or DDDR system (n = 3), who presented with AF at 18 follow-up visits. Bipolar atrial sensing was programmed to the most sensitive value. Atrial blanking times were programmed from 100 to 200 ms in 25-ms steps in each patient. Using marker annotation, the following parameters were measured at ten consecutive ventricular beats: VAF = the interval between ventricular stimulus and first sensing of AF; AFS = the number of atrial-sensed events between two ventricular events; and XAF = the interpolated number of atrial-sensed events during atrial blanking time. The intervals between ventricular events and between atrial-sensed event markers showed no significant differences for the five blanking times tested. There was no significant influence of the atrial blanking time onto the measured parameters (least square means +/- standard error) with VAF between 281 +/- 12 and 300 +/- 12 ms (P = NS), AFs between 3.4 +/- 0.2 and 3.6 +/- 0.2 beats (P = NS) and XAF between 1.84 +/- 0.12 and 2.03 +/- 0.12 beats (P = NS). At ventricular rates < 100/min, the atrial sensing of AF in dual chamber pacemakers demonstrated no evidence for deterioration by an increase of the atrial blanking time from 100 to 200 ms. Thus, the risk of ventricular far-field sensing may be reduced without compromising atrial sensing.

[Support of spontaneous atrioventricular conduction in patients with DDR(R) pacemakers: effectiveness and safety]. / Unterstützung der spontanen atrioventrikulären Uberleitung bei Patienten mit DDD(R)-Schrittmachern. Effektivität und Sicherheit.

AIM: In a prospective and randomized multicenter study using a cross-over protocol we compared the efficacy and the safety of the ELA medical mode-switch algorithm (DDD/AMC = DDD to AAI) to conventional DDD stimulation in patients with spontaneous AV conduction. PATIENTS AND METHOD: Forty-eight patients with a mean age of 67 +/- 13 years were included. Underlying heart disease was present in 54%. Pacemaker indications were paroxysmal AV block (21%), sick-sinus syndrome (46%), paroxysmal AV block + sick-sinus syndrome (31%) and tachycardia-bradycardia syndrome (8%). Patients were excluded from the study in case of a permanent 1st to 3rd degree AV block, a right bundle-branch block with QRS > 120 ms, severe coronary heart disease or idiopathic cardiomyopathy. The programming of the pacemaker was randomized to either DDD/AMC or DDD and was crossed over after 1 month. The AV interval (AVI) which was programmed in conventional DDD pacing was calculated as AVI = PR (or AR) + 30 ms at rest or as AVI = PR (or AR) - 50 ms during exercise. When the DDD/AMC mode was programmed, the AV interval was calculated automatically. We analyzed the AV interval, the frequency of ventricular pacing, the number of pacemaker-induced tachycardias, the number of atrial tachyarrhythmias, and the final programming which was left to the physician's choice. RESULTS: The AV interval after conventional DDD stimulation was 201 +/- 38 ms vs 195 +/- 28 ms with DDD/AMC (p = ns). Ventricular stimulation was significantly less often in the DDD/AMC mode than in the DDD mode (15 +/- 17% vs 48 +/- 37%, p < 0.001). Thereby the DDD/AMC algorithm led to a 69% reduction of ventricular pacing which means an approximately 5.5 months prolongation of the battery lifetime. There was no significant difference in the incidence of pacemaker-induced tachycardias. At the end of the study 77% of the physicians programmed the DDD/AMC mode. CONCLUSION: The analyzed DDD/AMC mode-switch algorithm leads to a significant reduction of ventricular pacing in patients with spontaneous AV conduction or with only paroxysmal AV block. Thereby the battery lifetime is prolonged and the incidence of complications due to ventricular pacing can be reduced.

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.

First experience with an automatic sensing algorithm in single-lead VDD stimulation.

UNLABELLED: An "Autosensing" algorithm available in SSI(R) and DDR(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.

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.