Aortic stenosis (AS) is the narrowing of the exit of the left ventricle of the heart such that problems result. It may occur at the aortic valve as well as above and below this level. It typically gets worse over time. Symptoms often come on gradually with a decreased ability to exercise often occurring first. If heart failure, loss of consciousness, or heart related chest pain occurs due to AS the outcomes are worse. Loss of consciousness typically occurs with standing or exercise. Signs of heart failure include shortness of breath especially with lying down, at night, and with exercise as well as swelling of the legs. Thickening of the valve without narrowing is known as aortic sclerosis.Causes include being born with a bicuspid aortic valve and rheumatic fever. A bicuspid aortic valve affects about one to two percent of the population while rheumatic heart disease mostly occurring in the developing world. A normal valve, however, may also harden over the decades. Risk factors are similar to those of coronary artery disease and include smoking, high blood pressure, high cholesterol, diabetes, and being male. The aortic valve usually has three leaflets and is located between the left ventricle of the heart and the aorta. AS typically results in a heart murmur. Its severity can be divided into mild, moderate, severe, and very severe based on ultrasound of the heart findings.Aortic stenosis is typically followed using repeated ultrasounds. Once it has become severe treatment primarily involves valve replacement surgery with transcatheter aortic valve replacement (TAVR) being an option in some who are at high risk from surgery. Valves may either be mechanical or bioprosthetic with each having risks and benefits. Another less invasive procedure, balloon aortic valvuloplasty (BAV) may result in benefit but this is for only for a few months. Complications like heart failure may be treated as per normal in those with mild to moderate AS. In those with severe disease a number of medications should be avoided including ACE inhibitors, nitroglycerin, and some beta blockers. Nitroprusside or phenylephrine may be used in those with decompensated heart failure depending on the blood pressure.Aortic stenosis is the most common valvular heart disease in the developed world. It affects about 2% of people who are over 65 years of age. Estimated rates are not known in most of the developing world as of 2014. In those who have symptoms, without repair, the chance of death at five years is about 50% and at 10 years is about 90%. Aortic stenosis was first described by French physician Lazare Rivière in 1663.