64 year old female with a history of pacemaker.
-Underlying atrial fibrillation
-Ventricular pacing with a vector suggestive of biventricular pacing
- Atrial fibrillation
- Paced morpohology consistent with biventricular pacing
Discussion: When the paced QRS is positive in V1 and negative in limb lead I, this is fairly specific for cardiac resynchronization therapy. Do not forget to code the underlying atrial rhythm which is best seen in V3 (atrial fibrillation).