We present the case of a 68-year-old man with a cardiac resynchronization therapy-defibrillator Medtronic device implanted 3 years ago, admitted to our hospital due to a wide complex tachycardia with unexpected pacing spikes inside QRS complexes. Although that could be easily attributed to ventricular undersensing, more complicated mechanisms are involved, including the origin of the tachycardia, the parameters of the device, and the position of the device and the leads.
Keywords: defibrillator function; paradoxical pacing; resynchronization therapy; wide complex tachycardia.
© 2022 The Authors. Journal of Arrhythmia published by John Wiley & Sons Australia, Ltd on behalf of the Japanese Heart Rhythm Society.