Ventricular Rate Stabilization Algorithm of ICD Causing Dual Chamber Pacing During Ventricular Tachycardia

Some implantable cardioverter-defibrillators (ICD) are designed with a ventricular rate stabilization (VRS) algorithm triggered by sensing a pacemaker-defined ventricular premature complex, for the prevention of short-long-short sequences that may predispose to ventricular tachycardia (VT). The VRS algorithm initiates AV sequential pacing at a relatively fast and decreasing rate according to a programmable sequence. This report describes a complex manifestation of ICD function where activation of the VRS algorithm produced AV sequential pacing during sustained VT. This response occurs when there is an appropriate relationship between the timing cycles of the ICD and a relatively slow VT.