Sinus tachycardia

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2]

Sinus tachycardia is a rhythm with elevated rate of impulses originating from the sinoatrial node, defined as a rate greater than 100 beats/min in an average adult. The normal heart rate in the average adult ranges from 60–100 beats/min. Note that the normal heart rate varies with age, with infants having normal heart rate of 110–150 bpm to the elderly, who have slower normals.

• Sinus bradycardia

1. Hammill S. C. Electrocardiographic diagnoses: Criteria and definitions of abnormalities, Chapter 18, MAYO Clinic, Concise Textbook of Cardiology, 3rd edition, 2007 ISBN 0-8493-9057-5

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ayokunle Olubaniyi, M.B,B.S [2]

Sinus tachycardia can result from various causes which include: cardiovascular (e.g. heart failure, myocardial infarction, cardiac tamponade); side effect of medications (e.g. aminophylline, atropine); infectious (e.g. sepsis); metabolic (e.g. dehydration, hypoglycemia), and many other conditions. It can also be as a result of some acute, life threatening conditions such as alcohol and cocaine overdose, pulmonary embolism, anemia, shock, e.t.c

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

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Usually apparent on the EKG, but if heart rate is above 140 bpm the P wave may be difficult to distinguish from the previous T waveand one may confuse it with a paroxysmal supraventricular tachycardia or atrial flutter with a 2:1 block. Ways to distinguish the three are:

• Vagal maneuvers (such as carotid sinus massage or Valsalva maneuver) to slow the rate and identification of P waves
• Administer AV blockers (e.g., adenosine, verapamil) to identify atrial flutter with 2:1 block

Postural orthostatic tachycardia syndrome (POTS) usually occurs in women with no known heart problems. This syndrome is characterized by normal resting heart rate but exaggerated postural sinus tachycardia with or without orthostatic hypotension.