Bundle Branch Block Module

Complete Bundle Branch Block

Tech Series
ECG Interpretation

Thomas E. O'Brien
AS CCT CRAT RMA

Objectives

Upon completion of the accompanying narrative, the student will be able to:

Recall which view is most commonly referred to when determining the presence of left or right bundle branch block
Recognize the morphologic features and inclusion criteria of complete left or right bundle branch block
Apply the process for measurement to determine the presence of left or right complete bundle branch block

Analysis of ECGs

People may choose to analyze ECG’s in a number of different ways. The sequence doesn’t necessarily matter as long as you gather and report the proper information each time.

If your protocols are different, always follow them.

Lessons

Lesson #1: Bundle Branch Block Determination

Intro

Evidence of Bundle branch block (BBB) may be seen in any lead, but the best view for determining the difference between left and right BBB is lead V1.

Interruption, delay of conduction or a change in the electrical conduction pathway will cause morphologic changes in the QRS complex.

Among those changes seen will include a widening of the QRS complex measuring 0.12 seconds or greater and may include an alteration in the deflection of the ventricular depolarization.

Lesson #2: Bundle Branch Block Determination II

Steps 1-3

Changes specifically seen include the QRS complex measuring 0.12 seconds or greater due to this delay. When determining the presence of BBB there are just a few simple steps to follow.

Step 1: Refer to lead V1
Step 2: Look for evidence that the electrical activity started above the ventricles (P wave). This is sometimes referred to as supraventricular activity.
Step 3: QRS complex measures 0.12 seconds or greater (not including aberrant complexes i.e. PVCs)

Steps 1-3 (continued)

By following the previous three steps, you will be able to determine whether a BBB is present or not.

Now it is simply a matter of one more step when analyzing the QRS in V1 to distinguish whether it is a left BBB or a right BBB.

Lesson #3: Bundle Branch Block Determination III

Step 4

Analyze the terminal portion of the QRS complex. Starting at the “J” point go one small box back into the QRS (moving to the left).

If the energy is below the isoelectric line, this is a left BBB.
If the energy of the depolarization is above the isoelectric line, this is a right BBB.
some people refer to a turn signal: down is left, up is right