Electrocardiographic findings in accessory right precordial leads in adults and seniors with notched S waves in lead V1-a preliminary study.

Background: Atypical right bundle branch block (RBBB) may present with an rS pattern and notched S wave in lead V1 . The notched S wave may represent slowed conduction or delayed activation of the right ventricular conduction system or ventricular myocardium.

Methods: We retrospectively analyzed the QRS patterns in accessory right precordial leads (from V3 R to V5 R) in 15 adults/senior individuals with notched S wave in lead V1 .

Results: In the right accessory precordial leads, 13 showed triphasic QRS pattern with final R' wave in their QRS complexes. This QRS pattern in association with notched S wave in lead V1 is suggestive of the presence of RBBB (incomplete or complete).

Conclusions: A notched S wave in lead V1 and in the right precordial accessory leads associated with a final R' wave suggests the possibility of concealed RBBB (incomplete or complete).