Optimal Implantable Cardioverter Defibrillator Programming

When an Implantable Cardioverter Defibrillator can Kill your Patient!

Inappropriate therapy due to noise oversensing caused a true ventricular fibrillation (VF) and a life-threatening event in a patient. A 19-year-old patient with surgically corrected congenital heart disease and systolic dysfunction had an implantable cardioverter defibrillator implanted for primary prevention in 2013. This patient was admitted at the Emergency Department in June 2018 after receiving eight shocks from the device on the same day, with a prolonged syncope after the third shock. Another noise-induced VF detection occurred, and two inappropriate shocks followed sequentially, causing true VF. Four appropriate shocks were subsequently needed until sinus rhythm was finally restored.

Sensing and Detection Functions in Implantable Cardioverter Defibrillators: The Good, the Bad and the Ugly

Implantable cardioverter defibrillators are small devices that have been proven to be beneficial by preventing sudden cardiac death, whether in primary or secondary prevention. Appropriate functioning of implantable cardioverter defibrillators is mainly dependent on the "good" sensing of ventricular electrogram waves, allowing for the adequate detection of ventricular arrhythmias in order to deliver appropriate therapy of either antitachycardia pacing or by delivering a shock according to the detected rhythm. Basic sensing function in defibrillators is based on detection rate and detection duration; additional parameters that are involved in the process of adequate detection include ventricular electrogram sensing, auto-adjusting sensitivity, supraventricular arrhythmia discrimination criteria, noise detection, and various dedicated algorithms. Defective sensing may result in the delivery of inappropriate therapy (oversensing) or inappropriate withholding of therapy (undersensing); the latter of which may lead to sudden cardiac death. This paper describes different clinical scenarios and programming tips to avoid abnormal or critical clinical situations.