Left ventricular aneurysm is a bulge in the wall of the lower left chamber of the heart when the rest of it contracts. It is usually seen as a complication to a heart attack. In that heart attack, the blood vessel to the bulging region is totally blocked and there is very little collateral blood supply. The affected region of heart muscle is scarred and thinned out so that it bulges out when the rest of the left ventricle contracts and pressure inside rises.
