Background & Objectives: Coronary artery diseases are the leading causes of mortality and morbidity in industrial countries and in Iran. Myocardial infarction and unstable angina are essential clinical syndromes of coronary artery diseases, with the difference that the mortality and morbidity of NonST-elevated myocardial infractions is more than U/A and requires more intensive care. Rapid differentiation and diagnosis of NSTEMI from U/A plays a major role in effective treatment of patients and improvement of their prognosis. This study was designed to determine the incidence of nonST-elevated MI among patients hospitalized with initial diagnosis of U/A.

  Methods: This is a descriptive and analytical study performed on patients hospitalized with U/A diagnosis between 2001 and 2002 in Ardabil Buali hospital. The data (including demographic characteristics, patients’ clinical findings, ECG changes, laboratory findings) were collected using a questionnaire and analyzed by SPSS software using descriptive and analytical statistics.

  Results: mean patient age was 61 and prevalence of nonST-elevated MI among patients with U/A was 23 patients (22.1%). Mean age of patients with NSTEMI was 60.5 and its prevalence was greater in male (69.9%) than in female (30.4%). The most prevalent ECG change in patients was T wave inversion and ST depression (78.3%) and in U/A patients it was T wave inversion (60.5%). The difference was statistically significant (p<0.001). 64.7% of the NSTEMI patients and 27.4% of the patients with U/A had severe chest pain (p<0.004).

  Conclusion: Prevalence of NSTEMI was about ¹/₅ of patients hospitalized with diagnosis of U/A and ECG changes among these patients (as T wave inverison and ST depression along with negative T wave) is more prevalent compared to those with U/A. Clinical manifestation and complications were more severe in these patients than U/A group.