This ECG is from a healthy young man in his 20's. He was born with a ventricular septal defect (VSD) that was surgically repaired when he was a toddler. He now has a right bundle branch block, which could be a result of the defect, or the surgery. This is a good ECG for the Instructors' Collection because it clearly shows all the ECG characteristics of right bundle branch block: wide QRS in a supraventricular rhythm (in this case, NSR), rSR' pattern in V1, wide or "slurred" S waves in Leads I and V6. There is no rhythm strip below the 12 leads in this ECG, but there is no rhythm disturbance.