Cardiac 'resynchronization' by a left lateral accessory pathway.

We present the case of a 21 year-old woman with unremarkable medical history except for tachycardia episodes. The ECG showed a delta wave pre-excitation by a left lateral pathway. One radiofrequency pulse temporarily terminated the accessory pathway conduction, revealing a nodal conduction with complete left bundle branch block.

T wave oversensing and low percentage of biventricular pacing in cardiac resynchronization therapy.

The success of cardiac resynchronization therapy (CRT) depends on a high percentage of ventricular pacing. We present the electrocardiography and electrograms of a patient who underwent an implantable cardioverter-defibrillator (ICD) with CRT implantation showing a low percentage of ventricular pacing as a result of T wave oversensing of paced QRS. The patient showed no clinical improvement.