Over- and undersensing-pitfalls of arrhythmia detection with implantable devices and wearables.

Cardiac implantable electronic devices (CIEDs) are a cornerstone of arrhythmia and heart failure detection as well as management. In recent years new kinds of devices have emerged which can be used subcutaneously or worn on the skin. In particular for large-scale arrhythmia monitoring, small, unobtrusive gadgets seem positioned to upend paradigms and care delivery. However, the performance of CIEDs and wearables is only as good as their sensing and detection capacities. Whether for pacing, defibrillation or diagnostic monitoring, the device must be able to process and filter the sensed signal to reduce noise and to exclude irrelevant physiological signals. The demands on sensing and detection quality will differ depending on how the information is applied. With a pacemaker or implantable cardioverter/defibrillator, withheld or erroneous therapy can have severe consequences and accurate and reliable detection of cardiac function is crucial. Monitoring devices are usually used in risk assessment and management, with greater tolerance for isolated artefacts or lower quality of readings. This review discusses sensing and detection and the performance to date by CIEDs as well as subcutaneous and wearable devices.