26. Rabkin, S.W., Mathewson, F.A.L., Tate, R.B.: Long term follow-up of incomplete right bundle branch block: The risk of development of complete right bundle branch block. J Electrocardiology 14 (4): 379-386, 1981.
The purpose of this study was to examine the long term prognosis of "so-called" incomplete right bundle branch block (RSR in V1 or V2) from the perspective of the risk of occurrence of complete right bundle branch block. The Manitoba Study consists of a cohort of 3983 men who have been followed with regular examinations, including ECGs since 1948. Six hundred and twenty-six cases with R1 in the right precordial leads were observed from the time of their first 12 lead ECG to the end of the observation period in 1977. Ten cases of right bundle branch block occurred in this group. Although the number with complete right bundle branch block is small, it was significantly p<0.05) greater than the number of cases expected, based on calculations of the incidence rate in the entire cohort. The age adjusted incidence rate for complete right bundle branch block was 1.76/1000 person years in those wiht R1 in leads V1 or V2, and 0.44/1000 person years in those without R1 in V1 or V2. The age adjusted incidence of complete right bundle branch block was greater in persons with R1 in V1 or V2 and QRS duration less than 0.10 sec. (1.22/1000 person years) than those without R1 in these leads (0.44/1000 person years) but the observed number of cases was not significantly greater than expected. In those with R1 and QRS duration of 0.10 sec. or greater and less than 0.12 sec., the age adjusted incidence rate was 3.03/1000 person years and a significant (p< 0.05) greater number of cases was observed than expected. In addition the time interval between the detection of R1 in V1 or V2 and development of complete right bundle branch block was significantly (p<0.05) shorter in those with wider QRS compared to a narrower QRS (4.2 versus 15.8 years respectively).
This data suggests that an R1 in the right precordial leads represents a form of impaired conduction in the right bundle branch system, especially when associated with a QRS duration between 0.10 to 0.12 seconds because of the increased likelihood of complete right bundle branch block.