Ventricular Aneurysm

Excerpt

About 1.5 million patients develop acute myocardial infarction per year in the United States. Several complications, such as ischemic, mechanical, arrhythmic, embolic, or inflammatory complications, are associated with acute myocardial infarction. The development of mechanical complications after acute myocardial infarction is associated with significantly reduced short-term and long-term survival. One of the most common complications occurring post-infarction is a ventricular aneurysm. LV aneurysm was first reported in 1951 by angiographic evidence. The term aneurysm applies to the bulging or outpouching of the weakened muscle wall. The natural course leading to the formation of a ventricular aneurysm involves a full-thickness infarct that has been replaced by fibrous tissue. This inert portion cannot take part in the contraction and herniates outward during systole. It leads to an expansion of a dyskinetic area and forms a thin circumscribed, fibrous and noncontractile outpouching.

A significant left ventricular (LV) aneurysm is present in 30% to 35% of acute transmural myocardial infarction. The two major risk factors for developing LV aneurysm include total occlusion of the left anterior descending artery and failure to achieve patency of infarct site artery. Ventricular aneurysms can be true or false aneurysms. A true aneurysm is formed by full-thickness bulging of the ventricular wall. In contrast, a false ventricular aneurysm is formed by the rupture of the ventricular wall, which is contained by the surrounding pericardium. The inferior and anterior myocardial infarctions occur with almost equal frequency. It explains 85% of a true LV aneurysms location at the apical and anteroseptal wall. The incidence of an inferior-posterior or lateral wall aneurysm is very low, about 5% to 10%. This preference for the apical site may be explained because there are only three layers of muscle at the apex compared with four layers at the base. False aneurysms tend to involve the posterior or diaphragmatic surface more commonly than the apical or lateral wall. Most of the ventricular aneurysms are asymptomatic and are evident during routine diagnostic procedures. However, LV aneurysm symptoms can range from thromboembolic, arrhythmic, wall motion abnormalities, reinfarction, ventricular tachyarrhythmias, and risk of sudden cardiac death.