 Aneurysms are classified by type, morphology, or location.A true aneurysm is one that involves all three layers of the wall of an artery (intima, media and adventitia).True aneurysms include atherosclerotic, syphilitic, and congenital aneurysms, as well as ventricular aneurysms that follow transmural myocardial infarctions (aneurysms that involve all layers of the attenuated wall of the heart are also considered true aneurysms).