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. We suggest finding a good sensitivity of F waves in induced ventricular fibrillation during ICD implantation in order to overcome the harm of possible oversensing

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. (Cardiol J 2012; 19, 5: 536-538