Dominant R waves or RSR' patterns in right precordial leads frequently present problems in differential diagnosis. Either may be a normal variant or an indication of heart disease.
Variants of the RSR' pattern are common in normal children and not uncommon in young adults. The normal R' wave is attributed to late activation of the crista supraventricularis. It is often difficult to distinguish normal from abnormal and one of the knottiest problems is the RSR' complex in lead V1 or V2 that casts suspicion on the otherwise normal patient and her tracing (Figure, d). Some general rules are helpful:1
An R' wave is probably normal in V2 if it is not found in V1; it is probably normal in V1 if not present in V3R or a low V1.
An R' wave is probably abnormal if it is associated with a primary R