A clinical study was made on 200 cases of bundle branch block diagnosed in 5,762 electroc ardiogramson 5,050 patients, with particular reference to etiological diseases. This group consisted of 115 cases of complete right bundle branch block (ICRTIBB), 73cases of complete right bundle branch block(CRBBB)and 12 cases of complete left bundle branch block (CLBBB). The overall incidence of bundle branchblock among 5,050 patients was 3.98% ; ICRBBBwas 2.28%; CRBBB 1.45% and CLBBB 0.24%.
The major etiological diseases of ICRBBB in patients under the age of 20 were congenital heart disease, atrial septal defect being most frequent, rheumaticheart disease was the major etiological disease in those between the ages of 20 and 39 and hypertensive cardiovascular disease and/or arteriosclerotic heart disease in those above the age of 40. However, in about 45% of cases with ICRBBB no definite evidence of heart disease was found clinically.
The most common underlying diseases of CRBBB were congenital heart disease, particulaly atrial septal defect and rheumatic heart disease is those under the age of 40 and hypertensive cardiovascular disease and/or arteriosclerotic heart disease in those above40. However, no definite evidence of heart disease was noted clinically in about 45% of cases with CRBBB.
Hypertensive cardiovascular disease and/´or arteriosclerotic heart disease were responsible for 75% of CLBBB and none of the patients with CLBBB was
found without serious organic heart disease.
The incidence of ICRBBB in the various cardiacs was high in congenital heart disease and rheumatic heart disease in the order of frequency, whereas that of CRBBB was high in conge Rital heart and hypertensive cardiovascular disease and/or arteriosclerotic heart disease in the order of frequency. The incidence of CLBBB was definitely high in hypertensive cardiovascular disease and/or arteriosclerotic heart disease among others.
Major electrocardiographic abnormalities associated with CRBBB were right ventricular hypertrophy, with or without left ventricular hypertrophy andauricular fibrillation. On the other hand, left ventricular hypertrophy, myocardial infarction and atrioventricular block were major associated electrocardiographic abnormalities of CLBBB.
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