Inhibition and restoration of CRT pacing - What is the mechanism?

The electrocardiogram (ECG) interpretation in patients with cardiac resynchronization therapy (CRT) may be challenging. The difficulty increases if not well-known pacemaker algorithm is turned on. We show a T-wave protection algorithm (LVTP) in a patient with CRT. Accelerated sinus rhythm and intermittent oversensing in left ventricular channel resulted in loss of CRT pacing. The restoration of biventricular pacing occurred when atrial rate decreased. We provide detailed descriptions of the electrocardiogram and intracardiac electrogram. LVTP may confuse ECG examination interpretation, especially in patients with accelerated atrial rhythm and oversensing in left ventricular channel.