Background: Although brain natriuretic peptide (BNP) levels are shown to be an important prognostic factor in patients with acute myocardial infarction (MI), the relationship between arrhythmias and BNP levels is not known. This study assessed whether baseline clinical factors, N-terminal-proBNP (NT-proBNP) levels and electrocardiographic patterns of acute inferior MI are associated with greater risk of developing complete atrioventricular block (CAVB) and mortality. Methods and Results: Seventy-nine consecutive patients (52 male, 27 female with an avarage age of 64.2 ± 10.9 years) with CAVB and 119 control patients (93 male, 16 female with an average age of 57.7 ± 11.4 years) without CAVB were enrolled. Regression analysis revealed that NT-proBNP levels > 104 pg/mL increased the development of CAVB by 16.7 folds, > 1 mm ST elevation in RV4 by 2.7 folds, ratio of elevation in lead III:II > 1.5 by 10.1 folds but the thrombolytic therapy decreased the development of CAVB by 2.8 folds. NT-proBNP > 92 pg/mL increased the mortality by 8.9 folds, a ratio of ST-segment elevation in lead III:II > 1 by 3.1 folds, ST segment elevation > 1 mm in RV4 by 3.5 folds, ejection fraction < 35% by 24.2 folds, age > 65 years by 8.3 folds and CAVB by 6.8 folds, on contrary thrombolytic treatment decreased the mortality by 3.3 folds. Conclusions: Simple electrocardiographic measurements and NT-proBNP levels at admission can be used as a screening test for development of complications such as CAVB, right ventricular involvement and mortality during acute inferior wall MI. © 2012 Via Medica.