How are pseudoaneurysms best distinguished from true aneurysms?

True ventricular aneurysms are lined by scarred myocardium and have a broad neck. Pseudoaneurysms occur after myocardial rupture contained by pericardium or scar tissue and lack myocardium in the wall. Pseudoaneurysms typically have a narrow neck and are more prone to rupture.

Pseudoaneurysms can occur at various locations, not exclusively the apex. Both true aneurysms and pseudoaneurysms may contain thrombus, so this is not a distinguishing feature.

This differentiation is important clinically and is detailed in adult echocardiography and surgical cardiology texts and ASE guidelines【16:Textbook of Clinical Echocardiography, 6e†p.400-405】【12:ASE Cardiac Masses and Aneurysms Guidelines†p.150-160】.