There has been a previous extensive transmural myocardial infarction involving the free wall of the left ventricle. Note that the thickness of the myocardial wall is normal superiorly, but inferiorly is only a thin fibrous wall. The thinned area represents a ventricular aneurysm that has developed as a consequence of the healed infarct. Such an aneurysm represents non-contractile tissue that reduces stroke volume and strains the remaining myocardium. The stasis of blood in the aneurysm predisposes to mural thrombosis.