BBB

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.

This is a good example of wide complex tachycardia that must be evaluated for V Tach vs supraventricular rhythm with left BBB.
The rhythm initially looks regular, but becomes irregular in V1 - V3. No P waves are seen prior to the QRSs, even when the rate slows down. The typical pattern for left bundle branch block exists: wide QRS, negative QRS in V1 and positive QRS in Lead I and V6. The irregularity suggests atrial fibrillation. A longer rhythm strip would be very helpful here. The axis, which is extreme left, could be from V Tach OR left BBB. There is no precordial concordance, favoring LBBB.
You may use this image free of charge to enhance your presentations or student handouts. Click on image, or, for best image quality, right click and SAVE image. For permission and charges for use in publications or for marketing uses, please contact the owner at ECGGuru@Comcast.net.