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Sinus Tachycardia

normal
Lead II
25 mm/s10 mm/mV
Heart rate
72bpm
RR
833ms
QT
273ms

Sinus Tachycardia

The SA node fires normally but at a rate above 100 bpm. A physiologic response to exercise, fever, pain, anxiety, hypovolemia, or other stressors — not a primary arrhythmia.

Mechanism

The SA node fires normally but at a rate above 100 bpm. A physiologic response to exercise, fever, pain, anxiety, hypovolemia, or other stressors — not a primary arrhythmia.

Findings· 3
  • Regular rhythm, rate >100 bpm.
  • Normal P waves (may merge with preceding T at high rates).
  • Normal PR, narrow QRS.
Clinical Impact

Treat the underlying cause, not the rate. Persistent unexplained sinus tachycardia warrants investigation.

Differential· 2
SVT (AVNRT)

Both regular narrow-complex tachycardias. SVT has abrupt onset, no P waves, rate usually >150.

Atrial Flutter 2:1

Regular ~150 bpm can mimic sinus tachy. Adenosine unmasks flutter waves.