[Electrical storm: definition, prevalence, causes and prognostic implications]. / Elektrischer Sturm: Definition, Häufigkeit, Ursachen und prognostische Implikationen.

BACKGROUND: Electrical storm (ES) represents a state of cardiac electrical instability which manifests by multiple episodes of ventricular tachyarrhythmia (VT) within a short time. In patients with an implantable cardioverter-defibrillator (ICD), ES is best defined as ≥ 3 appropriate VT detections in 24 h, treated by antitachycardia pacing or shock. The number of shocks and inappropriate detections are irrelevant for the definition. Within a period of 3 years ES occurred in approximately 25 % of ICD patients with secondary prophylaxis indications of sudden cardiac death. Although the definition includes minor arrhythmic events, ES frequently consists of up to 50 VTs. Potential triggers found in 20-65 % of patients include new/deteriorated heart failure, diarrhea/hypokalemia, changes in antiarrhythmic medication, association with other illnesses, and psychological stress. In most patients ES consists of monomorphic VT indicating the presence of reentry while ventricular fibrillation indicating acute ischemia is rare. MATERIAL AND METHODS: ES seems to have a low immediate mortality (1 %) but frequently (50-80 %) leads to hospitalization. Long-term prognostic implications of ES are unclear. The key intervention in ES is a reduction of the elevated sympathetic tone by beta blockers and also frequently sedation. Amiodarone i.v. is highly efficient in ES while class I antiarrhythmic drugs are usually unsuccessful. Substrate mapping and VT ablation may be useful in treatment and prevention of ES. Prevention of ES requires ICD programming systematically avoiding unnecessary shocks by long VT detection and numerous attempts of antitachycardia pacing before shock therapy which can fuel the sympathetic tone and prolong ES.

External cardioversion of atrial fibrillation in patients with implanted pacemaker or cardioverter-defibrillator systems: a randomized comparison of monophasic and biphasic shock energy application.

AIMS: External cardioversion (ECV) of atrial fibrillation (AF) may damage implanted pacemaker and cardioverter-defibrillator (ICD) systems. This prospective study evaluated the safety and efficacy of ECV comparing mono- to biphasic shock waveforms in patients with implanted rhythm devices. METHODS AND RESULTS: Patients with pacemaker or ICD systems and an indication for ECV were randomized to receive mono- or biphasic shocks. Systems were tested immediately before and after ECV, 1 h and 1 week later with respect to device and lead integrity. Forty-four patients (71 +/- 10 years, 31 male; 29 pacemakers, 12 ICDs, three cardiac resynchronization systems) underwent ECV with antero-posterior paddle orientation (monophasic in 21 and biphasic in 23 patients). Pacing impedances were reduced immediately after ECV (atrial 402-392 ohm, P < 0.001; ventricular 517-496 ohm, P = 0.001) and returned to baseline values within 1 week. Ventricular sensing was reduced immediately after ECV (12.4-11.6 mV, P = 0.004). There was no device or lead dysfunction in any patient. ECV was successful in 42/44 patients (95%), cumulative energy was significantly lower for biphasic compared with monophasic shocks (P = 0.001). CONCLUSION: ECV for AF seems to be safe and effective in patients with implanted rhythm devices.

ICD therapy in coronary artery disease. A reappraisal in 2005.

25 years after the first coronary artery patient received an implantable cardioverter defibrillator (ICD), many randomized controlled trials on prophylactic ICD therapy have been conducted. Taken together, these trials allow an evidence-based approach to primary prevention of sudden cardiac death in patients after a myocardial infarction. Patients with chronic ischemic cardiomyopathy, a long history of heart failure, and an ejection fraction of < or = 0.30 benefit from preventive device therapy and are thus candidates for prophylactic defibrillator implantation. For this purpose, a single-chamber device appears to be appropriate, since there have been no prospective studies showing convincing clinical benefit by adding an atrial lead. For similar patients who have additional intraventricular conduction delays, a biventricular ICD must be considered. However, this decision must be based on individual considerations until more data from prospective trials become available. Prophylactic ICD therapy should not be used in patients with recent myocardial infarction. There is convincing evidence that ICD benefit in coronary patients accrues after a considerable time having elapsed from the most recent infarct, presumably at least 6 months or perhaps longer.

Efficacy and safety of ICD therapy in a population of elderly patients treated with optimal background medication.

INTRODUCTION: Implantable cardioverter-defibrillator (ICD) therapy has been shown to improve survival in patients with structural heart disease and at high risk for life threatening ventricular arrhythmias. Whether elderly patients benefit from device therapy in a similar way as younger patients is largely unknown. METHODS: We retrospectively analyzed data from 375 consecutive ICD recipients with structural heart disease. Patients were divided into two groups, younger than 70 years at time of ICD implantation (group 1) or 70 years or older (group 2). Main outcome measures were time to death from any cause and time from first appropriate ICD therapy to death. RESULTS: Group 1 and 2 patients were comparable with respect to clinical presentation and average follow-up duration. In the elderly patient group, 78% received an ICD for secondary prevention versus 63% in group 1 (p = 0.007). During a mean follow-up period of 26.5 +/- 18.1 months, there was no significant difference in overall mortality among the two groups: 47 patients died, 34 (12.5%) of group 1 versus 13 (12.7%) of group 2. The average time to death was 28.4 +/- 16.7 vs 30.4 +/- 22.1 months after device implantation, respectively (p = ns). There was no difference in time from device implantation to first adequate ICD therapy and time from first appropriate ICD therapy to death among the two groups (p = ns). Device associated complications were comparable in both groups. CONCLUSIONS: Elderly ICD recipients had comparable survival rates and appropriate use of the ICD compared to younger individuals.