Left ventricular (LV) aneurysms and pseudoaneurysms represent serious complications, primarily associated with myocardial infarction (MI), though other etiologies exist. While both involve abnormal bulging of the LV wall, they differ significantly in their pathophysiology, radiological appearance, and management. Understanding these differences is crucial for accurate diagnosis and appropriate treatment planning. This article will delve into the distinctions between LV true aneurysms and pseudoaneurysms, focusing on their radiological features, echocardiographic characteristics, and therapeutic approaches.
Pathophysiology and Formation:
A true aneurysm involves all three layers of the ventricular wall (endocardium, myocardium, and epicardium). It results from progressive weakening and dilation of the myocardial wall, often due to extensive myocardial necrosis following an MI. The weakened area gradually stretches and bulges outward, forming a sac-like structure that communicates directly with the LV chamber. The aneurysm's wall comprises attenuated but intact myocardial tissue. This process is relatively slow and progressive.
In contrast, a pseudoaneurysm, also known as a false aneurysm, is a contained rupture of the myocardium. It lacks a true myocardial wall; instead, it is a contained outpouching of blood surrounded by a thin layer of pericardium, thrombus, and fibrous tissue. This typically occurs acutely after an MI, when a significant portion of the myocardium ruptures, but the rupture is contained by the surrounding pericardium, adjacent structures, or adherent thrombus. The result is a bulging sac filled with blood, which communicates with the LV through a small, often narrow, neck or defect. This communication is crucial in differentiating it from other cardiac masses.
Radiological Features:
Imaging plays a vital role in differentiating between true and false aneurysms. While both appear as outpouchings of the LV on imaging modalities, subtle but important differences exist:
* Echocardiography: Echocardiography, particularly transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE), is the initial and often definitive imaging modality for diagnosing both true and false aneurysms.
* True Aneurysm (Echo): A true aneurysm typically presents as a thinned, globally dilated segment of the LV wall with akinesis or dyskinesis. The neck of the aneurysm is wide and continuous with the LV chamber. The wall thickness is demonstrably reduced compared to the surrounding myocardium. Thrombus formation within the aneurysm is common.
* Pseudoaneurysm (Echo): A pseudoaneurysm is characterized by a thin, echolucent, and often poorly defined wall, often with a narrow neck connecting it to the LV cavity. The neck is a critical differentiating feature; it is significantly narrower than in a true aneurysm. The wall of a pseudoaneurysm consists primarily of pericardium, thrombus, and fibrous tissue, not intact myocardial tissue. Intraluminal thrombus is almost invariably present. Color Doppler echocardiography can demonstrate the communication between the LV and the pseudoaneurysm through the narrow neck.
* Cardiac Computed Tomography (CT) and Magnetic Resonance Imaging (MRI): CT and MRI provide superior anatomical detail, allowing for a more precise assessment of the aneurysm's size, shape, wall thickness, and the presence of thrombus.
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