Hi. Sinus tachycardia is sinus rhythm with a rate of > 100bpm.  Appropriate sinus tachycardia can result from:  Exercise Anxiety Alcohol / caffeine use Drugs (e.g. beta-agonists like dobutamine) Inappropriate sinus tachycardia can result from: Fever Hypotension Hypoxia Congestive heart failure Bleeding Anemia Hyperthyroidism Cardiomyopathy (with reduced left ventricular function and compensatory tachycardia) Myocarditis Inappropiate sinus tachycardia is rare and characterized by tachycardia at rest and exaggerated acceleration of the heart during physiologic stress. The mechanism leading to an exaggerated response of the sinus node to minimal physiologic stress is incompletely understood. Consult Physician...