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Description / Table of Contents: Summary 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.

Description / Table of Contents: Summary 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 hat to be ≤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 ≤15 J in 166 of 176 patients (94%). The DFT+ in the study group was 9.6±3.2; in control group 10.1±.35 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 2× 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 2× 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 2× DFT+ value.

Description / Table of Contents: Summary 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) ≤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×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×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×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×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.

Description / Table of Contents: Summary 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 signalaveraged-electrocardiogram (SAECG) in risk stratification of sudden cardiac death and arrhythmogenic events, the clinical characteristics of these postinfarction 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.