| ADT | Accepted Dental Therapeutics; adenosine triphosphate; admission, discharge, transfer; agar-gel diffu... |
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| ATD | Alzheimer-type dementia; androstatrienedione; anthropomorphic test dummy; antithyroid drug; aqueous ... |
| ATS | Achard-Thiers syndrome; acid test solution; alpha-D-tocopherol acid succinate; American Thoracic Soc... |
| CTU | cardiac-thoracic unit; centigrade thermal unit; constitutive transcription unit |
| CTV | cervical and thoracic vertebrae; clinical target volume |
| aortic sac | In mammalian embryos, the endothelially lined dilation just distal to the truncus arteriosus; it is the primordial vascular channel from which the aortic arches arise and is homologous to the ventral aorta of gill-bearing vertebrates. (05 Mar 2000) |
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| aortic septal defect | A small congenital opening between the aorta and pulmonary artery about 1 cm above the semilunar valves, e.g., aorticopulmonary window. Synonym: aorticopulmonary window. (05 Mar 2000) |
| aortic sinus | The space between the superior aspect of each cusp of the aortic valve and the dilated portion of the wall of the ascending aorta, immediately above each cusp. Synonym: sinus aortae, Petit's sinus, Valsalva's sinus. Arlt's sinus, an inconstant depression on the lower portion of the internal surface of the lacrimal sac. Barber's pilonidal sinus, pilonidal sinus occurring in barbers, usually in the web between the fingers, due to the burying of exogenous hairs by the alternate loosening and tightening of tissues of the hand by the manipulation of scissors. (05 Mar 2000) |
| aortic sinus aneurysm | Abnormal dilation of one or more of the three aortic sinuses situated behind the three aortic valve cusps. (05 Mar 2000) |
| aortic spindle | A fusiform dilation of the aorta immediately beyond the isthmus. Synonym: His' spindle. (05 Mar 2000) |
| aortic stenosis | Progressive narrowing of the aortic valve resulting in the obstructed passage of blood from the left ventricle into the aorta. Causes for aortic stenosis include rheumatic fever, congenital and idiopathic sclerosis. Chronic stenosis can lead to left ventricular enlargement and congestive heart failure. (27 Sep 1997) |
| aortic sulcus | A broad deep groove on the medial aspect of the left lung above and behind the hilum receiving the arch of the aorta and the thoracic aorta. Synonym: sulcus aorticus. (05 Mar 2000) |
| aortic ultrasound | An ultrasound examination of the aorta to determine its size, shape and course. The diagnosis of abdominal aortic aneurysm can be made using this test. (27 Sep 1997) |
| aortic valve | The heart valve that divides the left ventricle and the aorta. The aortic valve opens during left ventricular contraction and then closes to prohibit the backwash of oxygenated blood from the aorta into the ventricle. The aortic valve has 3 valve cusps. (27 Sep 1997) |
| aortic valve insufficiency | Backflow of blood from the aorta into the left ventricle, owing to imperfect functioning of the aortic semilunar valve. (12 Dec 1998) |
| aortic valve prolapse | The downward displacement of the cuspal material (misalignment of the cusps) below a line joining points of attachment of the aortic valve leaflets. The prolapsed cusp may occlude the ventricular septal defect during ventricular diastole. (12 Dec 1998) |
| aortic valve stenosis | Narrowing of the orifice of the aortic valve or of the supravalular or subvalvular regions. (12 Dec 1998) |
| aortic vestibule | The anterosuperior portion of the left ventricle of the heart immediately below the aortic orifice, having fibrous walls and affording room for the segments of the closed aortic valve. Synonym: Sibson's aortic vestibule, vestibulum aortae. (05 Mar 2000) |
| apical-aortic conduit | A valved conduit between the LV apex and aorta, used to treat severe otherwise unapproachable LV outflow tract obstruction. (05 Mar 2000) |
| bicuspid aortic valve | See: familial aortic ectasia syndrome. (05 Mar 2000) |