Dynamic left ventricular outflow tract (LVOT) obstruction was thought to be a hallmark of hypertrophic obstructive cardiomyopathy, especially in those cases with isolated asymmetric septal hypertrophy and systolic anterior motion (SAM) of the mitral valve. Recently, several authors described the occurrence of a dynamic LVOT obstruction during acute coronary insufficiency in ventricles without significant myocardial hypertrophy. The LVOT gradient was reported to disappear following resolution of the ischemic syndrome. Furthermore, it was reported that LVOT obstruction in the setting of acute myocardial infarction could predispose to cardiac rupture. We describe four cases with acute anterior myocardial infarction complicated with a dynamic LVOT obstruction documented by transthoracic Doppler echocardiogram. The detection of the dynamic LVOT obstruction allowed us to optimize the pharmacological treatment in each case. In spite of therapy, two of our patients worsened progressively to fatal cardiogenic shock and cardiac rupture. In conclusion, the development of a LVOT obstruction during acute anterior myocardial infarction has to be considered a serious and potentially fatal complication.