Dictionary

aortic aneurysm See aneurysm, aortic.

aortic arch The second section of the aorta following the ascending aorta. As it continues from the heart, it gives off the brachiocephalic trunk, and the left common carotid and subclavian arteries. The brachiocephalic trunk splits to form the right subclavian and the right common carotid arteries, which supply blood to the right arm and…

aortic insufficiency Backflow of blood from the aorta into the left ventricle across a weakened aortic valve. Also known as aortic regurgitation.

aortic regurgitation See aortic insufficiency.

aortic stenosis Narrowing (stenosis) of the aortic valve, the valve between the left ventricle of the heart and the aorta. This narrowing impedes the delivery of blood to the body through the aorta and makes the heart work harder. The need for surgery depends on the degree of stenosis. A procedure called balloon valvuloplasty has…

aortic valve One of the four valves of the heart. The aortic valve is positioned at the beginning of the aorta. It normally permits blood from the left ventricle to flow into the aorta, and prevents blood in the aorta from returning to the heart. See also heart valve.

aortic valve, bicuspid An abnormal aortic valve with only two cusps. See also aortic stenosis.

aortitis Inflammation of the aorta. The causes of aortitis include syphilis and rheumatic fever.

anticipation The progressively earlier appearance and increased severity of a disease from generation to generation. The phenomenon of anticipation was once thought to be an artifact, but a biological basis for it has been discovered in a number of genetic disorders, such as myotonic dystrophy and Huntington disease.

anti-citrulline antibody See citrulline antibody.

anticoagulant An agent that is used to prevent the formation of blood clots. Anticoagulants have various uses. Some are used for the prevention or treatment of disorders characterized by abnormal blood clots and emboli. Anticoagulant drugs include intravenous heparin, which acts by inactivating thrombin and several other clotting factors that are required for a clot…

antidepressant A medication that prevents or reduces the symptoms of clinical depression. Some antidepressants may also be prescribed for their other medical effects, including increasing blood flow within the brain and treating chronic pain. See also MAO inhibitor; SSRI; tricyclic antidepressant.