Dynamic left ventricular outflow tract obstruction in acute coronary syndromes: an important cause of new systolic murmur and cardiogenic shock.

Dynamic left ventricular outflow tract (LVOT) obstruction has traditionally been associated with hypertrophic obstructive cardiomyopathy. Recently, acute dynamic LVOT obstruction has been described as a complication of myocardial infarction (MI). Herein the cases of 3 patients are described, all of whom presented with a systolic murmur and electrocardiographic evidence of MI. All 3 patients developed cardiogenic shock and were subsequently found by echocardiography to manifest an acute dynamic LVOT obstruction. Cardiogenic shock persisted until therapy was directed toward decreasing the degree of the dynamic LVOT obstruction. The treatment of acute coronary syndromes in the presence of a dynamic LVOT obstruction differs from the traditional treatment of acute coronary syndromes and includes the use of beta-blockers and alpha1-agonists, as well as the avoidance of therapies that aggravate the magnitude of the LVOT obstructive gradient, including nitrates, inotropic agents, and afterload reduction. The development of a systolic murmur in the setting of acute MI complicated by cardiogenic shock with only a small elevation in creatine kinase suggests the presence of a dynamic LVOT obstruction, as well as the classical mechanical complications of MI, namely, ventricular septal rupture and papillary muscle rupture. The presence of a dynamic LVOT obstruction is reliably detected by transthoracic echocardiography or by transesophageal echocardiography if transthoracic image quality is suboptimal.