Naming of components of QRS complex

Naming of components of QRS complex

Initial negative deflection of the QRS complex is named a q or Q wave depending on the amplitude. Usually waves less than 5 mm in amplitude are designated by small letters and those larger than 5 mm with capital letters. But this may not be strictly followed by all who use these terminologies. Initial positive deflection will be called an R wave regardless of whether there is a q or Q preceding it. A negative deflection occurring after and r or R wave will be called as S wave, regardless of whether there is a preceding q or Q wave. When there is only a single negative deflection, it is called as a qs or QS complex depending on the amplitude. qR will be a small q followed by a big R wave. QR would mean big Q and R waves.

qRs would mean small q followed by tall R and a small s. Rs would be tall R followed by small s. rs would indicate small r and s. rS will be small r follwed by deep S. rsR should be called rsR’ as a second positive wave should be designated R’. Second s or S should be similarly designated as s’ or S’. Definition of pathological Q wave is usually as one which has a width of at least 40 ms or depth more than 25% of the ensuing R wave. Of these, the width is more important than the depth.