Arrhythmia detection by dual-chamber implantable cardioverter defibrillatorsA review of current algorithms

This article reviews the arrhythmia detection criteria currently available in dual-chamber implantable cardioverter defibrillators (ICDs), and describes the implementation and performance of various detection algorithms. Nearly all criteria implemented in single-chamber devices appear to have been included in dual-chamber ICDs. However, two different strategies can be distinguished: the first adds dual-chamber inhibition criteria to a single-chamber detection configuration; the second is a new approach entirely based on a dual-chamber detection scheme. Despite widely available clinical data, an analysis of the implemented detection indexes, arrhythmia characteristics (induced vs spontaneous, minimum duration), device programming (detection rate, programme maintenance and tuning during follow-up), and different storage capabilities among various ICD models, leaves the results of these studies ultimately ambiguous. New algorithms are under study, but only protocols using a single set of arrhythmias and the same programming for all devices may allow relevant comparisons of the performances of detection algorithms. Furthermore, a criterion is required to distinguish reliably between haemodynamically stable and unstable tachycardias, not simply based on rate, but including the underlying cardiac function.