| AI | accidental injury; accidentally incurred; adiposity index; aggregation index; allergy and immunology... |
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| AS | acetylstrophanthidin; acidified serum; acoustic schwannoma; acoustic stimulation; active sarcoidosis... |
| SAR | scatter/air ratio; seasonal allergic rhinitis; sexual attitude reassessment; slowly adapting recepto... |
| SVAS | supravalvular aortic stenosis; supraventricular aortic stenosis |
| TAA | thioacetamide; thoracic aortic aneurysm; total ankle arthroplasty; transverse aortic arch; tumor-ass... |
| aortic dissection | A pathologic process, characterised by splitting of the media layer of the aorta, which leads to formation of a dissecting aneurysm. Classified according to location as follows: type I involves the ascending aorta, transverse arch, and distal aorta; type II is confined to the ascending aorta; type III extends distally in the descending aorta. (05 Mar 2000) |
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| aortic dissection: aetiology | <radiology> Usually degenerative, due to aging, increased risk: hypertension, bicuspic aortic valve, aortic coarctation, pregnancy, connective tissue disorder (Marfan, Ehlers-Danlos), skeletal abnormalities (scoliosis, pectus), mycotic aneurysm, Takayasu (giant cell) arteritis, aortic laceration see also: classification (12 Dec 1998) |
| aortic dissection: classification | <radiology> DeBakey: I ascending aorta to arch with or without descending aorta (30%), II ascending aorta only (20%), III descending aorta to thoracic aorta (50%), Stanford: A involvement of ascending aorta (regardless of origin), B aortic arch and distal aorta see also: aetiology mnemomics: 1 A.D. (DeBakey), A = Ascending (12 Dec 1998) |
| aortic dwarfism | Underdevelopment of physical stature associated with severe aortic stenosis. (05 Mar 2000) |
| aortic facies | The pale sallow complexion of one suffering from incompetence of the aortic valve. (05 Mar 2000) |
| aortic foramen | The opening in the diaphragm bounded by the two crura, the vertebral column, and the median arcuate ligament, through which pass the aorta and thoracic duct. Synonym: hiatus aorticus, aortic foramen, aortic opening. (05 Mar 2000) |
| aortic hiatus | The opening in the diaphragm bounded by the two crura, the vertebral column, and the median arcuate ligament, through which pass the aorta and thoracic duct. Synonym: hiatus aorticus, aortic foramen, aortic opening. (05 Mar 2000) |
| aortic incompetence | Defective closure of the aortic valve permitting regurgitation into the left ventricle during diastole. (05 Mar 2000) |
| aortic insufficiency | A congenital or acquired heart valve abnormality that results in the abnormal back flow of blood in the aorta, through an incompetent aortic valve and into the left ventricle. Chronic aortic insufficiency leads to enlargement of the left ventricle and pulmonary congestion. If left uncorrected, congestive heart failure will result. Aortic valve replacement is eventually necessary in most cases of significant valvular incompetence. (27 Sep 1997) |
| aortic knob | The prominent shadow of the aortic arch on a frontal chest radiograph. (05 Mar 2000) |
| aortic knuckle | The contour of the aortic arch protruding from the mediastinal silhouette in an anteroposterior (AP) radiograph of the chest. (05 Mar 2000) |
| aortic laceration | <radiology> Deceleration injury, 80% at aortic isthmus (just distal to insertion of lig. Arteriosum), other sites: proximal ascending aorta, descending aorta at diaphragmatic hiatus, transverse aortic arch, laceration usually transverse, all layers involved in only 40% (12 Dec 1998) |
| aortic lymphatic plexus | A plexus of lymph nodes and connecting vessels lying along the lower portion of the abdominal aorta. Synonym: plexus aorticus. (05 Mar 2000) |
| aortic murmur | A murmur produced at the aortic orifice, either obstructive or regurgitant. (05 Mar 2000) |
| aortic nerve | <anatomy, nerve> A branch of the vagus which ends in the aortic arch and base of the heart; composed entirely of afferent fibres; its stimulation elicits a brainstem reflex which causes slowing of the heart, dilation of the peripheral vessels, and a fall in blood pressure. Synonym: Cyon's nerve, depressor nerve of Ludwig, Ludwig's nerve. (05 Mar 2000) |