Optimal method to achieve consistently low defibrillation energy requirements.

Reduction of the defibrillation energy requirement offers the opportunity to decrease implantable cardioverter defibrillator (ICD) size and to increase device longevity. Therefore, the purpose of this prospective study was to obtain confirmed defibrillation thresholds (DFTs) of < or = 15 J in each patient with an endocardial dual-coil lead system incorporating an active pectoral pulse generator (TRIAD lead system: RV- --> SVC+ + CAN+). According to our previous clinical and experimental studies, we tried to lower DFTs that were > 15 J by repositioning the distal coil of the endocardial lead system in the right ventricle. A total of 190 consecutive patients requiring ICDs for ventricular fibrillation and/or recurrent ventricular tachycardia were investigated at the time of ICD implantation (42 women, 148 men; mean age 61.9 +/- 12.0 years; mean left ventricular ejection fraction 42.7 +/- 16.6%). Coronary artery disease was present in 139 patients; nonischemic dilated cardiomyopathy in 34 patients; and other etiologies in 17 patients; 47 patients had undergone previous cardiac surgery. Regardless of optimal pacing and sensing parameters, for patients having DFTs > 15, we repositioned the distal coil of the endocardial lead system toward the intraventricular septum to include this part of both ventricles within the electrical defibrillating field. In 177 of 190 patients, induced ventricular fibrillation was successfully terminated with < or = 15 J (group I) using the initial lead position. Repositioning of the endocardial lead was necessary in 13 patients whose DFT(plus) (DFT(plus) = second additional success at lowest energy level) were > 15 J (group II). In all patients, repositioning was successful within a 15 J energy level (100% success). The mean DFT(plus) was 7.3 +/- 3.5 J (group I) and 11.0 +/- 4.5 J (group II; p<0.005). The mean DFT(plus) of all patients enrolled in the study was 7.6 +/- 3.7 J (range: 2 to 15 J). In 87% of all patients, DFT(plus) of < or = 10 J was achieved. Repositioning of the endocardial lead in the right ventricle is a simple and effective method to reduce intraoperative high DFTs. As a result of this procedure, ICDs with a 20 J output should be sufficient for the vast majority (87%) of our patients. Furthermore, we were able to avoid additional subcutaneous or epicardial electrodes in all patients.

[Inflammation of the myocardium as an arrhythmia trigger]. / Entzündung des Myokards als Arrhythmietrigger.

In patients with acute or chronic myocarditis, arrhythmias are a common and often the only clinical symptom in the natural course of the disease. The potentially malignant tachy- and bradyarrhythmias are of particular significance in the differential diagnosis of sudden cardiac death in myocarditis. Factors responsible for the increased incidence of cardiac arrhythmias are structural changes, parameters of ventricular dynamics and vascular changes. On the one hand, inflammatory processes in the cardiac myocytes and interstitium can lead directly to fluctuations in membrane potential. Fibrosis and scarring of the myocardial tissue and secondary hypertrophy and atrophy of the myocytes favor the development of ectopic pacemakers, late potentials and reentry as a result of inhomogeneous stimulus conduction. Furthermore, parameters of ventricular dynamics such as increased wall tension, increased myocardial oxygen consumption and diminished coronary reserve in the case of disturbed systolic or diastolic left ventricular function also contribute to the increased incidence of arrhythmias. Lastly, vascular factors can further increase the arrhythmogenicity of the inflamed myocardium through the disturbance of micro- and macrovascular perfusion and the resulting myocardial ischemia. Non-invasive rhythmological evaluation by 24 h Holter ECG, measurement of ventricular late potentials and heart rate variability can be used for orienting risk stratification of the at-risk patient with myocarditis. Programmed atrial and ventricular electrophysiological stimulation also has a relatively high predictive value for spontaneous ventricular tachyarrhythmias. It should be emphasized that, at the present time, optimal electrophysiological parameters with a high predictive value do not exist. In a selected patient population, immunosuppressive therapy in addition to conventional antiarrhythmic therapy can lead to the reduction or complete suppression of spontaneous and inducible arrhythmias. Nevertheless, in the interim, further precautionary antiarrhythmic measures such as serial antiarrhythmic treatment, VT ablation and ACID implantation are necessary in patients with malignant cardiac arrhythmias. Right ventricular myocardial biopsy for demonstration or exclusion of myocarditis is an important additional examination which can improve the differential diagnosis and treatment of patients with cardiac arrhythmias of unclear etiology.

[14-year experience with implantable cardioverter/defibrillators: determination of prognosis and discharge behavior]. / 14 Jahre Erfahrung mit implantierbaren Cardioverter/Defibrillatoren: Determinanten der Prognose und des Auslöseverhaltens.

BACKGROUND: The treatment of life threatening ventricular arrhythmias with implantable cardioverter/defibrillators (ICD) has become the therapy of choice; the survival benefit of ICD treatment compared to drug therapy in patients with aborted sudden cardiac death (SCD) and hemodynamically unstable ventricular tachycardia has been proven. In addition for the primary prevention of SCD in high risk patients, ICD therapy is gaining growing acceptance. PATIENTS AND METHODS: We analyzed the long-term follow-up of 274 consecutive patients (211 male, 63 female, age 59 +/- 12 years, left ventricular ejection fraction 39 +/- 15%) provided with an ICD between 1984 and 1998. The aim of the study was to ascertain the survival rate in different subgroups and to discover determining factors of ICD discharge and prognosis. RESULTS: Long-term survival probability at 10 resp. 14 years was 84 resp. 65% for the total collective, and the freedom of event probability (neither shocks nor antitachycardiac pacing from the ICD) to 28% each. The risk to die from SCD was below 3% over time. The most pronounced differences regarding prognosis ensued from dividing the collective into heart insufficiency stages. Thus in NYHA class I and II versus III and IV, the cumulative event rate was 61% vs 82% at 5 years, and survival rate amounted to 94 vs 63% at 5 years and 87% vs 30% at 14 years (p < 0.001). Calculating the relative benefit of ICD therapy survival benefit provided by the ICD was shown to decrease significantly after 5 years for patients in NYHA class III/IV, while it increased progressively for patients in NYHA class I/II up to 10 years. Additional determinants of prognosis and ICD discharge rate were identified left ventricular ejection fraction, age and tendency for the basic cardiac disease, however neither the result of electrophysiological testing nor the results of non-invasive risk stratification. In patients with ischemic heart disease, revascularization procedures improved prognosis only in tendency, while the effect of ICD therapy was significant. In patients with the non-obstructive form of hypertrophic cardiomyopathy ICD, discharges occurred in about 50% of patients; in contrast patients with surgical myectomy for obstructive cardiomyopathy showed no events during follow-up. In patients with chronic inflammatory heart disease and normal left ventricular function (LVF), a very low event rate was expected if patients were treated by immunosuppressive drugs. Patients with dilated cardiomyopathy did not differ from patients with ischemic heart disease with respect to prognosis and ICD discharge rate. CONCLUSION: Significant determinants of prognosis and ICD discharge rate are left ventricular function, age and with limitations the basic cardiac disease. In contrast to patients with better LVF relative survival benefit decreases significantly after 5 years in patients with a worse LVF. Patients with aborted SCD and preserved LVF experience half the ICD discharges compared to patients with poor LVF and gain at the same time a normalization of life expectancy. Causative treatment of the basic disease has an impact on the overall prognosis and event rate, but should in general not influence the decision for IDC implantation in high risk patients.

[Chemoreflex and baroreflex sensitivity in patients with survived sudden cardiac death]. / Chemoreflex- und Baroreflexsensitivität bei Patienten mit überlebtem plötzlichem Herztod.

INTRODUCTION: To evaluate patients with an increased risk of sudden cardiac death the analysis of ventricular late potentials, heart rate variability and baroreflexsensitivity is helpful. However, the prediction of malignant arrhythmic events cannot be performed with sufficient accuracy. For a better identification of high risk patients other methods are necessary. In this study the impact of the chemoreflexsensitivity for the prediction of ventricular tachyarrhythmias was investigated. METHODS: Out of 44 patients included in the study, 23 were survivors of sudden cardiac death (SCD). Seven patients suffered from sustained monomorphic ventricular tachycardias, 14 had no arrhythmic events in their prior history. For the investigation of the baroreflexsensitivity (BRS) systolic blood pressure was augmented by Norfenefrin (Novadral) and the resulting increase of RR-intervals was measured in the surface-ECG. For determination of the chemoreflexsensitivity (ChRS) the ratio of the RR-interval-shift and the blood pressure shift during a 5-min inhalation of oxygen with a nose mask was formed. RESULTS: Patients with aborted SCD showed significantly decreased values for the ChRS compared to those patients without an arrhythmic event in their prior history (2.49 +/- 1.86 vs. 6.75 +/- 6.79 mm Hg, p < 0.001). In contrast, for the BRS no significant differences could be found (5.23 +/- 3.95 vs. 5.34 +/- 3.10 mm Hg, p = n.s.). Patients with aborted sudden cardiac death and inducible tachyarrhythmias during the electrophysiologic study showed significantly lower values of BRS and ChRS compared to patients without inducibility. CONCLUSION: As a new method for identification of patients with an increased risk of sudden cardiac death the analysis of chemoreflexsensitivity seems feasible and indicates an increased arrhythmic risk with a high sensitivity. The predictive impact has to be corroborated in larger patient collectives by prospect studies.

Improved sensing signals after endocardial defibrillation with a redesigned integrated sense pace defibrillation lead.

Adequate sensing is a basic requirement for appropriate therapy with ICDs. Integrated sense pace defibrillation leads, which facilitate ICD implantation, show a close proximity of sensing and defibrillation electrodes that might affect the sensing signal amplitude by the high currents of internal defibrillation. In 99 patients, we retrospectively examined two integrated sense pace defibrillation leads, either both with a distance of 6 mm between the tip of the lead (sensing cathode) and the right ventricular defibrillation electrode (sensing anode) or one with a distance of 12 mm. Three seconds after a shock of 20 J, mean sensing signal amplitude during sinus rhythm (SR) decreased from 10.5 +/- 4.3 mV to 5.1 +/- 3.7 mV (P < 0.001) for the 6-mm lead, but showed no significant decrease for the 12-mm lead. The degree of signal reduction was inversely related to the time passed since defibrillation. Significant differences in reduction of sensing signal amplitude concerning monophasic and biphasic shocks could not be observed. Mean sensing signal amplitude of VF after shocks that failed to terminate it decreased in the same order as during SR (from 8.3 +/- 4.1 mV to 4.1 +/- 3.2 mV), but resulted in no failure of redetection during ongoing VF. DFTs did not differ for the 6-mm and the 12-mm lead. In conclusion, close proximity of the right ventricular defibrillation coil to the sensing tip of an integrated sense pace defibrillation lead causes energy and time related reduction in sensing signal amplitude after defibrillation, and might cause undersensing in the postshock period. A new lead design with a more proximal position of the right ventricular defibrillation coil avoids these problems without impairing DFTs.