| SMR | senior medical resident; sensorimotor rhythm; severe mental retardation; sexual maturity rating; ske... |
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| SR | sarcoplasmic reticulum; saturation recovery; scanning radiometer; screen; secretion rate; sedimentat... |
| UHR | underlying heart rhythm |
| VR | right arm [electrode]; valve replacement; variable ratio; vascular resistance; venous reflux; venous... |
| AO | abdominal aorta; achievement orientation; acid output; acridine orange; ankle orthosis; anodal openi... |
| trigeminal rhythm | A cardiac arrhythmia in which the beats are grouped in trios, usually composed of a sinus beat followed by two extrasystoles. Synonym: trigeminy. (05 Mar 2000) |
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| triple rhythm | A triple cadence to the heart sounds at any heart rate, due to the easy audibility of a third (usually) or fourth heart sound, or at faster rates a summation sound due to coincidence of the third and fourth heart sounds. (05 Mar 2000) |
| trunk of atrioventricular bundle | The singular initial portion (stem) of the atrioventricular bundle which passes from the atrioventricular node into the right trigone of the fibrous skeleton of the heart and along the periphery of the membranous interventricular septum; upon reaching the muscular interventricular septum, the trunk terminates by dividing into the right and left crura of the atrioventricular bundle. Synonym: truncus fascicularis atrioventricularis. (05 Mar 2000) |
| escape rhythm | Three or more consecutive impulses at a rate not exceeding the upper limit of the inherent pacemaker; extreme range of impulse formation at the sinoatrial node is between 40 to 180 impulses per minute, that of the atrioventricular junction is normally 40 to 60 impulses per minute, and the normal rate of the ventricular myocardium (idioventricular rhythm) is 20 to 40 impulses per minute. (05 Mar 2000) |
| junctional rhythm | Rhythms originating anywhere within the A-V junction. Formerly, "A-V nodal" or simply "nodal" rhythms. (05 Mar 2000) |
| ultradian rhythm | See: ultradian. (05 Mar 2000) |
| left atrioventricular valve | <anatomy, cardiology> The heart valve that divides the left atrium and left ventricle. During left atrial contraction, the mitral valve opens to allow blood to flow into the left ventricle. Upon closure, the mitral valve prohibits the regurgitation of blood back into the left atrium. The mitral valve is the only heart valve that has only 2 valve cusps (all others have 3). (13 Nov 1997) |
| left crus of atrioventricular bundle | The left leg or branch of the atrioventricular bundle which separates from the atrioventricular bundle just below the membranous portion of the interventricular septum to descend the septal wall of the left ventricle and begins to ramify subendocardially. Synonym: crus sinistrum fasciculi atrioventricularis. (05 Mar 2000) |