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Right and Left Bundle Branch Blocks

Left bundle branch blocks are seen in the examples above.  The QRS durations are too wide to be normal but too narrow to indicate a ventricular pacemaker. These prolonged QRS  complexes and their abnormal shapes indicate bundle branch blocks.  Notice that there are no significant positive deflections (above the baseline) seen in this lead (V1).   This characterizes the block as left.


Right bundle branch blocks are seen in these examples, again all seen in lead V1.  Prolonged QRS duration and abnormal shape indicate these blocks.  Notice how in each case there are significant positive deflections (above the baseline).  This characterizes the blocks as right.