Purpose: To determine the type of cardiac disease causing left bundle branch block (LBBB) in Porto Alegre, Brazil, and to assess the role of associated left axis deviation (-30 degrees or more in the frontal plane) in order to identify a specific etiology of LBBB.
Methods: Through reports from the assistant physicians or through examination of the patients, the underlying heart disease in 264 cases of LBBB was assessed. The chi-square test was used to determine a possible association between left anterior hemiblock LBBB and one or more specific type of underlying heart disease.
Results: Systemic arterial hypertension (30.7%), ischemic heart disease (30.3%), valvar heart disease (8.7%), cardiomyopathies (7.5%), idiopathic degenerative disease of the conduction system (1.6%) and miscellaneous heart diseases (1.2%) were the underlying heart diseases. The presence of LBBB did not indicate any specific type of cardiac disease.
Conclusion: The causes of LBBB in Porto Alegre are the same as reported in the international medical literature. Upward and leftward deviation (> or = -30 degrees) of QRS axis in the frontal plane did not show statistical significant association with any type of underlying cardiac disease.