Background & Objective: Despite all improvements in diagnosis and treatment, one third of patients with Myocardial infarction lose their life. Different studies have shown that cardiac arrhythmia are the most common cause of death in MI, and cardiac blocks are one of the important groups of these arrhythmia, which are effective in prognosis, duration of hospitalization and hospital mortality of the patients.

  Methods : In this study, 630 patients with AMI, who were admitted in CCU of Bou-Ali hospital in Ardabil from January 1998 to January 2001 were studied and the data were callected with the help of questionnaires and secondary data analysis method. The data were analyzed with statistical methods.

  Results : 9.4% of cases in this study had AV block and 30.2% had bundle branch block. 40.5% of men and 37.6% of women had at least one kind of block(in AV node or bundle branch), but no significant relation was found between sex and these blocks. Also, 62% of in-hospital mortalities of patients with AMI were in association with blocks (AV or bundle branch) and only 38% of mortalities were without blocks. This showed a meaningful relation between hospital mortality and these kinds of blocks (p <0.05 ).

 Conclusions: The total frequency of AV and bundle branch blocks due to AMI, was 39.6% which is similar to other studies, but what is remarkable in this study, is the higher prevalence of bundle branch blocks due to AMI.