| RRR | regular rhythm and rate; renin release rate (or ratio) |
|---|---|
| RR&R | regular rate and rhythm |
| RSR | regular sinus rhythm; relative survival rate; right superior rectus [muscle] |
| SMR | senior medical resident; sensorimotor rhythm; severe mental retardation; sexual maturity rating; ske... |
| SR | sarcoplasmic reticulum; saturation recovery; scanning radiometer; screen; secretion rate; sedimentat... |
| tic-tac rhythm | A condition in which the cadence of the heart sounds resembles that of the foetus, the first and second sounds becoming alike and evenly spaced; a sign of serious myocardial disease. Synonym: pendulum rhythm, tic-tac rhythm, tic-tac sounds. Origin: embryo-+ G. Kardia, heart (05 Mar 2000) |
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| trainwheel rhythm | A quadruple cadence to the heart sounds due to the easy audibility of both third and fourth heart sounds, indicative of serious myocardial disease. Synonym: trainwheel rhythm. (05 Mar 2000) |
| 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) |
| 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) |
| 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) |