Sinus Tachycardia - EKG Reference Caliper Time Interval: ___ seconds Key Features RhythmRegular RateFast (> 100 bpm) P WaveNormal, may merge with T wave at very fast rates PR IntervalNormal (0.12-0.20 sec) QRSNormal (0.06-0.10 sec) NotesQT interval shortens with increasing heart rate Sinus Tachycardia EKG Reference Definition of Sinus Tachycardia Sinus Tachycardia is characterized by a pulse rate of more than 100 beats per minute in adults. The electrical signals originate in the sinoatrial (SA) node. Appropriate sinus tachycardia can result from exercise, alcohol or caffeine, drugs and anxiety. Inappropriate Sinus Tachycardia Inappropriate Sinus Tachycardia is fairly rare. It can result from hypotension, hypoxia, congestive heart failure, bleeding, cardiomyopathy, myocarditis, anemia and fever. Quick Links Sinus Atrial Junctional Ventricular Atrioventricular Pacemaker All