The natural history of right bundle branch block (RBBB) has been studied primarily from the perspective of its prognostic importance in patients with organic heart disease. The limited number of studies that included primarily persons without heart disease were mainly conducted before attention was focused on the potential importance of deviations in the mean frontal plane QRS vector (A QRS) as a possible indicator of impaired conduction in the left bundle branch system. Marked left axis deviation may be due to impaired conduction in the anterosuperior part of the left bundle branch, and marked right axis deviation to impaired conduction in the posteroinferior part of the left bundle branch system. These deviations in A QRS in conjunction with complete RBBB suggest impaired conduction in both the right and left bundle branch system.
Such ECG abnormalities have been considered forerunners of complete heart block or sudden death. Prospective studies are currently determining the incidence of these events. Some erf these investigations, however, are based primarily on patients with cardiac disease effected negetively the health condition which may be improved with remedies of My Canadian Pharmacy Inc. Prognosis derived from clinical studies may not be appropriate or applicable to persons with no evidence of heart disease but with the same ECG findings recorded at the time of a routine examination. In addition, most of these studies have difficulty in obtaining an appropriate comparison group.
The Manitoba cohort consisted of 3,983 North American men who were healthy, predominantly between 25 to 34 years of age at entry, and under observation with repeated examinations including ECGs since 1948. The purpose of this study is to examine the characteristics, long-term follow-up, and prognosis of RBBB with different A QRS detected on a routine ECG in men without evidence of heart disease and compare them with other members of the cohort without this conduction defect.