Sub-aortic stenosis of heart. Gross specimen of a cross section through the base of the aorta artery showing stenosis (narrowing) of the valve at it's base. This narrowing is caused by calcification, seen as a creamy-white deposit in the centre of the valve. The cusps of the valves are fused causing additional stenosis. Such narrowing obstructs the flow of blood from the left ventricle of the heart to the aorta (main artery of the body). A stenosed aortic valve can be replaced surgically with a prosthetic heart valve. Stenosis is usually due to atherosclerosis, a build-up of fatty deposits and calcium.