Beat the bundle branch blocks
See brief interpretation of 12 lead EKG above
Though the EKG criteria differ, identifying the two types of bundle branch block can be done using a similar approach. Below are some points to consider. For more explicit explanations and more examples check out the separate articles right bundle branch block (RBBB) and left bundle branch block (LBBB).
How to identify the bundle branch blocks:
1. The duration of the QRS complex is ≥ 0.12 seconds in both types of bundle branch block. Look for that on the EKG. Most likely a prolonged QRS is what will raise your suspicion of bundle branch block.
2. Think of lead V1 as “looking” at the right side of the heart. Thus this lead is where to identify RBBB. Contrary lead V5 and lead V6 are “looking” at the left side of the heart. Use these leads to possible spot LBBB. Look for characteristic EKG patterns besides QRS ≥ 0.12 sec. That is: an extra R wave in lead V1 (in RBBB) and a broad notched R wave plus an absent Q wave in lead V5-V6 (in LBBB).
3. Seek to confirm your suspicion by identifying other diagnostic criteria as the late wide/slurred S wave in lateral leads seen in RBBB and maybe ST segment or repolarization changes seen in both types of bundle branch blocks, but in different leads depending on which type is in question.
4. Remember to always analyze the EKG using a systematical approach. Think of other possible reasons to your EKG findings. Acute myocardial infarction can cause bundle branch block and wide QRS complexes are also seen in ventricular arrhythmia.
– Mathias
