| arrhythmias, atrial | Abnormal heart rhythm due to electrical disturbances in the atria (the upper chambers of the heart) or the AV node relay station , leading to fast heart beats. Examples of atrial arrhythmias includes atrial fibrillation, atrial flutter, and paroxysmal atrial tachycardia (PAT). (12 Dec 1998) |
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| arrhythmias, rapid | Abnormally rapid heart rhythms, medically termed tachycardia. (12 Dec 1998) |
| arrhythmias, slow | Abnormally slow heart rhythms, medically termed bradycardia. (12 Dec 1998) |
| arrhythmias, ventricular | Abnormal rapid heart rhythms (arrhythmias) that originate in the lower chambers of the heart (the ventricles). Ventricular arrhythmias include ventricular tachycardia and ventricular fibrillation. Both are life threatening arrhythmias most commonly associated with heart attacks or scarring of the heart muscle from previous heart attack. (12 Dec 1998) |
| arrhythmic | Marked by loss of rhythm; pertaining to arrhythmia. (05 Mar 2000) |
| arrhythmogenic | <pharmacology, physiology> Producing or promoting arrhythmia. Origin: Gr. Rhythmos = rhythm, gennan = to produce (18 Nov 1997) |
| arrhythmogenic right ventricular dysplasia | A congenital cardiomyopathy in which transmural infiltration of adipose tissue results in weakness and aneurysmal bulging of the infundibulum, apex, and posterior basilar region of the right ventricle and leads to ventricular tachycardia arising in the right ventricle. (12 Dec 1998) |
| arrhythmous | <medicine> Being without rhythm or regularity, as the pulse. Origin: Gr.; priv. + rhythm. Source: Websters Dictionary (01 Mar 1998) |
| arris | The sharp edge or salient angle formed by two surfaces meeting each other, whether plane or curved; applied particularly to the edges in moldings, and to the raised edges which separate the flutings in a Doric column. Arris fillet, a triangular piece of wood used to raise the slates of a roof against a chimney or wall, to throw off the rain. Arris gutter, a gutter of a V form fixed to the eaves of a building. Origin: OF. Areste, F. Arete, fr. L. Arista the top or beard of an ear of grain, the bone of a fish. Source: Websters Dictionary (01 Mar 1998) |
| arrondissement | A subdivision of a department. The territory of France, since the revolution, has been divided into departments, those into arrondissements, those into cantons, and the latter into communes. Origin: F, fr. Arrondir to make round; ad + rond round, L. Rotundus. Source: Websters Dictionary (01 Mar 1998) |
| arrow grass | <botany> An herbaceous grasslike plant (Triglochin palustre, and other species) with pods opening so as to suggest barbed arrowheads. Source: Websters Dictionary (01 Mar 1998) |
| arrow point tracing | A tracing of mandibular movements made by means of a device attached to the opposing arches; its shape resembles that of an arrowhead or a Gothic arch, and when the instrument's marking point is at the apex of the arch, the jaws are considered to be in centric relation. Synonym: arrow point tracing, Gothic arch tracing, Gothic arch, stylus tracing. (05 Mar 2000) |
| arrow poison | Any natural toxin used for coating arrows, spears, and darts (e.g., extracts containing aconitin, ouabain, cardiac glycosides, batrachotoxin, curare, etc.). (05 Mar 2000) |
| arrowhead | 1. <botany> An aquatic plant of the genus Sagittaria, especially. S. Sagittifolia, named from the shape of the leaves. 2. <cell biology> Fanciful description given to the pattern of myosin molecules attached to a filament of F actin. Easier to see if tannic acid is added to the fixative. The arrowheads indicate the polarity of the filament, the barbed (attachment) end is the site of major subunit addition. (18 Nov 1997) |
| arrowroot | 1. <botany> A west Indian plant of the genus Maranta, especially. M. Arundinacea, now cultivated in many hot countries. It said that the Indians used the roots to neutralize the venom in wounds made by poisoned arrows. 2. A nutritive starch obtained from the rootstocks of Maranta arundinacea, and used as food, especially. For children an invalids; also, a similar starch obtained from other plants, as various species of Maranta and Curcuma. Source: Websters Dictionary (01 Mar 1998) |