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Arrhenius equation

(ă-rā′nē-us) [Svante Arrhenius, Swedish chemist and Nobel laureate, 1859–1927] A mathematical formula that specifies the influence of temperature on the rate of a chemical reaction. In general, a higher temperature produces a faster reaction. The equation is used in industry and pharmacy to predict shelf life of reagents and pharmaceuticals.


(ar″ĕ-nō″blas-tō′mă) [Gr. arr(h)ēn, male + blastoma] An ovarian tumor that secretes male sex hormone, causing virilization in the female.

arrhinia, arhinia

(ă-rin′ē-ă, -rī′nē-) [1an- + rhino- + -ia] Congenital absence of the nose.


(ā″rith′mē-ă) [1an- + rhythm + -ia] Irregularity or loss of rhythm, esp. of the heart. SEE: dysrhythmia. arrhythmic (-mik), adj.

atrial a. A disturbance in cardiac rhythm, including atrial fibrillation, atrial flutter, multifocal atrial tachycardia, paroxysmal supraventricular tachycardia, and premature atrial contractions.

cardiac a. An abnormal rhythm of the heart caused by physiological or pathological disturbances in the discharge of cardiac impulses from the sinoatrial node or their transmission through conductive tissue of the heart. SEE: bradycardia; cardioversion; artificial cardiac pacemaker; sick sinus syndrome; tachycardia.

reperfusion a. Cardiac arrhythmia that occurs as the infarcted heart is resupplied with blood after angioplasty or thrombolysis.

sinus a. Cardiac irregularity marked by variation in the interval between sinus beats and evident on the electrocardiogram as alternately long and short intervals between P waves. Sinus arrhythmia may occur with respiration (evidenced as an increased heart rate during inspiration and a decreased heart rate on expiration) or may result from the use of digitalis glycosides. In older patients, presence of sinus arrhythmia is common and is statistically linked with an increased risk of sudden death.

ventricular a. A disturbance of the (cardiac) ventricular rhythms, including torsades de pointes, ventricular fibrillation, ventricular flutter, ventricular tachycardia, or frequent premature ventricular contractions. SYN: ventricular dysrhythmia.


(ā-rith″mŏ-jen′ik) [arrhythmia + -genic] Tending to produce or promote cardiac arrhythmias.

arrhythmogenic right ventricular dysplasia/cardiomyopathy

(ā-rith″mŏ-jen′ik) ABBR: ARVD/C. Arrhythmogenic right ventricular dysplasia.


American Registry of Radiologic Technologists.


Acute retroviral syndrome.


(ar′sĕn-ăl) 1. In health care, the resources available for clinical use, e.g., laboratory equipment or available drugs at a particular hospital. 2. Any of the various biochemical pathways used by a pathogen to cause disease.


(ar″sĕ-nī′ă-sĭs) [arsen(ium) + -iasis] Chronic arsenic poisoning. SYN: arsenicalism.


(ar′sĕ-nik, ars′nik) ...

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