Background and aims: Despite all wide improvement in diagnosis and treatment, one third of patients with acute Myocardial infarction lose their life. Cardiac arrhythmia is the most common cause of death in acute myocardial infarction, and cardiac blocks are of the important groups of these arrhythmia. This study was planned to determine the incidence of branch block of the heart and its demographic risk factors and related clinical history in patients with myocardial infarction.

Methods: In this cross-sectional study, 263 patients with acute myocardial infarction, who were admitted in CCU ward were studied and data of demographic characteristics and medical history were collected. Data were analyzed by STATA software and central tendency and dispersion using descriptive statistics, t-test, chi square and ANOVA.

Results: Relative frequency of incidence of total branch block was 15.97% (42 patients).  45.23% had right bundle branch block and 54.76% left bundle branch block. The incidence of right and left bundle branch block in total population under study were 7.22 and 8.75%. There was no significant relationships between the incidence of the right and left cardiac bundle branch block and sex, age, place of residence, high blood pressure and history of ischemic diseases (P>0.05), but there is a significant relationship between  the incidence of the right and left cardiac bundle branch block  and diabetes (P<0.05).

Conclusion: In this study, the incidence of branch block among patients was reported. Regarding to the high incidence of the factor under study, it is recommended to check patients with myocardial infarction seriously regarding to positive factor including diabetes and detection of ventricular arrhythmias including electrolyes disorders so that could be prevented by good clinical  measurement.