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 V3R to V5R) 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).