Comprehensive and Detailed Explanation From Exact Extract:

A pseudoaneurysm (false aneurysm) of the heart or great vessels is a contained rupture of the vessel or myocardial wall with a narrow neck and high risk of rupture, making it a surgical emergency. Unlike true aneurysms, pseudoaneurysms lack all vessel wall layers and have a fragile wall prone to catastrophic rupture.

True aneurysms involve all wall layers and generally have a lower immediate risk. Severe aortic or mitral stenosis are serious conditions often requiring intervention but not immediate emergency surgery unless complicated.

Therefore, pseudoaneurysm is the critical finding that mandates urgent surgical repair.

This distinction and management urgency are detailed in the "Textbook of Clinical Echocardiography, 6e", Chapter on Aneurysms and Cardiac Emergencies【20:385-390†Textbook of Clinical Echocardiography】.