Atrial tachyarrhythmias in primary and secondary prevention ICD recipients: clinical and prognostic data.

Background: Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice. The natural history of this disturbance and its effect on survival is still not known in patients with implantable cardioverter defibrillators (ICDs).
Methods and Results: Several controlled trials for both secondary and primary prevention of sudden death using ICDs have been published in literature, and meta-analysis of them provided useful clinical information on the outcome during the follow-up of this population. AF occurs in about 25% of the patients with secondary prevention indication for ICD implantation. The prevalence of AF in patients with primary prevention indication for ICD implantation is much more difficult to define; it seems to be higher in patients with left ventricular dysfunction due to nonischemic etiology (ranging from 15% to 25%), and is lower in patients with ischemic etiology (about 5-10%). However, data from clinical registries, which are expected to better reflect clinical practice than randomized trials, seem to show a substantial difference as compared to the latter ones. A history of AF episodes in patients with an ICD indication for both primary and secondary prevention is probably associated with a higher risk of death. This is particularly evident in secondary prevention in ICD recipients, while it is still controversial in patients who received an ICD for primary prevention, particularly when patients with nonischemic etiology of their left ventricular dysfunction are considered. In a population of patients implanted with an ICD, there are several other clinical factors (ejection fraction, New York Heart Association functional class, age) that can interfere with the risk of death much more than AF itself.
Conclusions: Further large-scale registries are needed to further characterize the population receiving ICD implantation, assessing the course of risk of death with regard to clinical variables and to evaluate the degree of acceptance of trials in clinical practice.