A 55-year-old recipient of a Marquis VR single chamber ICD in the context of an old anterior myocardial infarction, 40% left ventricular ejection fraction (LVEF) and episode of VT at 200 bpm during electrical storms, was complaining of palpitations.
This tracing illustrates 3 key elements : 1) the delivery of a shock is the primary function of an ICD. Shocks terminate tachyarrhythmias in the vast majority of cases. However, on rare occasions, the shocks are proarrhythmic and, as in this case, transform an organized VT into life-threatening VF; 2) the initially organized FVT suggests that ATP may have been successful, eliminating the need for multiple shocks; 3) the defibrillation threshold is not a fixed value and, in this case, several shocks at maximal output were ineffective, whereas the 5th shock, of the same strength, terminated the tachycardia.
A tachycardia was detected in the VF zone, which lasted 50 sec, explaining the clinical presentation with syncope. The 5th shock terminated VF. The PainFREE trial recommended systematic programming of ATP during the capacitor charge. However, this was not possible with this ICD model.
