Aortic valve stenosis or aortic stenosis A pathology in which the lumen of the aortic valve of the heart narrows☝🏻 The valve does not open fully, which reduces or blocks blood flow from the heart to the main artery (aorta) and to the rest of the body. Aortic stenosis is most often caused by calcium buildup on the aortic valve over time. These calcium deposits, which often appear with age, make the valve tissue stiff, narrow, and unyielding.