ICD monitoring zones: intricacies, pitfalls, and programming tips

Implantable cardioverter-defibrillators (ICD) are widely regarded as the treatment of choice for primary and secondary prevention against sudden cardiac death across a broad spectrum of underlying pathologies. Over the past 20 years, ICDs have evolved into complex multifunctional units capable of recording, chronicling, self-testing, and delivering interventional therapies. Technological advances permitted the creation of ICD monitoring zones that are now considered valuable in diagnosing slower, presumably more stable ventricular arrhythmias. They may be helpful especially in patients with unexplained symptoms such as palpitations and/or syncope, particularly in the setting of antiarrhythmic pharmacological therapy that may slow ventricular tachyarrhythmias. Caregivers largely view ICD monitoring zones as passive features that do not interfere or interact with appropriate functioning of active treatment zones. As will be discussed in this clinical review, this is not always the case. Herein, we unravel the intricacies regarding monitoring zone functions and algorithms, highlight potential pitfalls, and offer practical programming tips relevant to each device manufacturer.