Question of the month: Jody asked: “I'm trying to get my head around what is going on in the heart when it is referred to as a 'flipped bundle'...can you help me out?? July 31 2015
Hi Jody, Thanks for asking this question. I actually have never heard this expression before but had an idea it would be referring to bundle branch blocks. I did a search online for “flipped bundle” and “flipped bundle on the ECG” and came across numerous references to bundle branch blocks. So, a “flipped bundle” is either a right or left bundle branch block. By stating the bundle is “flipped” indicates that the direction of the QRS complex has “flipped” from its normal position to the position that results from the bundle branch block.
One reference actually referred to the flipping up or down of the QRS complex as the Turn Signal Theory. In the Turn Signal Theory, when you look at V1 in a Right Bundle Branch Block, the wide QRS complex flips or turns to an upright position above the isoelectric line. When you look at V1 in a Left Bundle Branch Block, the wide QRS complex is in a negative position below the isoelectric line. The Turn Signal refers to when you are driving and approach a turn, you will indicate to other drivers which direction you are turning by putting your turn indicator either ‘up’ or ‘down’. When you want to turn LEFT, you turn your indicator “down”. Left = down (LBBB) in V1. When you want to turn RIGHT, you turn your indicator “up”. Right = up (RBBB) in V1.
The rationale for the QRS complex to flip to a certain direction in a RBBB or LBBB is related to the altered electrical force having to compensate for the blocked branch. This altered electrical force will assume a new pathway around the blocked branch and this extra force will start off in the non-affected branch and associated ventricle and travel to the affected branch and associated ventricle. A basic rule in ECG is that a QRS complex is upright if the energy is traveling towards the positive electrode and a QRS complex is negative if the energy is traveling away from the positive electrode. Therefore, in a RBBB, because the altered energy is traveling toward the right bundle and right ventricle, V1 (which is sitting pretty much right at the right ventricle) will be an upright QRS complex. In a LBBB, because the altered energy is now traveling from the right bundle and right ventricle toward the left bundle and left ventricle, and traveling away from V1, the QRS complex will now be negative. I hope this has helped clear things up. If not, let me know and I will look into it further. Darlene
Thanks to Dawn Altman for her fantastic website: ECG Guru.
Jason E. Roediger - Certified Cardiographic Technician (CCT) at http://ecgguru.com/content/bundle-branch-block.