Aetiology of bundle-branch block.

During the past five years 161 cases of bundlebranch block have been seen in the Cardiac Department of St. Vincent's Hospital. These patients have been evaluated clinically in an attempt to identify all possible associated and causative factors. This communication deals with these various factors and attempts to identify their relative importance in the genesis of both types of conduction defect. Reference is also made to some clinical features noted in these patients.