Final answer:
A pseudoaneurysm is characterized by a wall rupture and a contained hematoma, differing from a true aneurysm which involves all three layers of the vessel bulging out.
Step-by-step explanation:
The key difference between a pseudoaneurysm and a true aneurysm of the heart is wall rupture and contained hematoma. A pseudoaneurysm, or false aneurysm, occurs when there is a rupture of the arterial wall and the leaking blood is contained by the surrounding tissues, creating a hematoma that communicates with the artery. This does not involve the three layers of the blood vessel wall. Conversely, a true aneurysm involves all three layers of the vessel (intima, media, and adventitia) bulging out due to weakening.