From your 2021 MCME Online module on Bundle Branch Blocks:
A question came up regarding what is RSR.
RSR is a “QRS” complex with an R-wave (upward deflection), followed by an S-wave (downward deflection), followed by another R-wave (upward deflection). This pattern is seen in lead V1 in Right Bundle Branch Blocks.
Check out the 2021 MCME Precourse on Bundle Branch Block for a deeper dive on this ECG finding.
Lead V1 with RsR pattern