A second factor to be considered

when deciding between a dual-chamber or single-chamber device is the detrimental effect of unnecessary right ventricular pacing on morbidity and mortality, which was observed in the early days of dual-chamber ICD therapy 24 and 36. In the meantime, this risk has been substantially reduced by the introduction of algorithms to minimize ventricular pacing 37, 38 and 39. The devices implanted within the OPTION trial were all equipped with SafeR, a well-established algorithm to minimize ventricular pacing, with proved effectiveness in randomized clinical trials 30 and 38. In the OPTION trial, no statistically significant differences in the percent of ventricular pacing was observed between the dual-chamber setting and single-chamber Z-VAD-FMK order setting groups, with a median

ventricular pacing percent of 0%. Furthermore, there were equivalent rates of death or cardiovascular events in both groups. Thus, dual-chamber ICD therapy combined with the SafeR algorithm provides a net benefit by reducing inappropriate shocks selleck products without increasing cardiovascular morbidity and mortality. Finally, it is generally believed that the implantation of dual-chamber ICDs requires greater expertise. There are reports of an increased incidence of implantation- and device-related complications with dual-chamber ICDs in current clinical care (23), recently confirmed by Peterson et al. (40). In contrast to that and in agreement with the DATAS (Dual Chamber and Atrial Tachyarrhythmias Adverse Events Study) (41), the OPTION trial showed no elevated incidence of device-related

or implantation-related adverse events in the dual-chamber Ureohydrolase group, even disregarding the atrial lead–related complications in the single-chamber group. All patients in the OPTION study were provided with dual-chamber devices. This could slightly overestimate the rates of inappropriate shocks due to AF induced by local irritation from the lead. This study design was chosen because the information from the atrial lead was crucial to determine accurately the appropriateness of the therapy, which represented a central component of our primary endpoint. Moreover, it should be noted that the slow ventricular tachycardia zone setting was different between the groups: this zone was used as a monitor zone for the single-chamber group, while ATP with no shock was recommended for the dual-chamber group. Such a difference must be considered in addition to the treatment difference that is under randomized investigation. Given the small number of inappropriate shocks in the dual-chamber setting group, further subgroup analysis with respect to patients who may benefit most from dual-chamber implantation was not possible. The crossover rate was higher than in some other studies. However, it is not assumed that this has contributed to the positive finding of the trial, because the vast majority of patients switched to the dual-chamber setting group.