ECG Level 3 Tutorial: Bundle Branch Blocks
Tutorial: Bundle Branch Blocks
Understand why a right bundle branch block and left bundle branch block pattern are created. Learn also the diagnostic criteria.
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Tutorial: Bundle Branch Blocks Incomplete blocks
Times Practiced
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
Incomplete blocks
Incomplete bundle branch blocks essentially share the same diagnostic criteria as complete bundle branch blocks with one difference: the QRS duration is shorter with incomplete blocks.

Remember that the QRS duration for complete blocks is > 120 ms (3 little squares). The QRS duration diagnostic criteria for incomplete bundle branch blocks is 100 - 120 ms. (which is 2.5 - 3 little squares).

Different textbooks might reference different QRS durations.

Here is an example of incomplete LBBB:

With close-ups of V1 and V6:

Here is an example of incomplete RBBB:

With close-up looks at V1 and V6: