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Lesson 12 of 21 · Rhythm Recognition

Sinus Rhythms

Sinus rhythms share upright P waves in II, one P per QRS, and a constant PR. They differ only in rate and regularity.

01The family

II
Normal sinus rhythm: 60–100.
II
Sinus bradycardia: < 60.
II
Sinus tachycardia: > 100, gradual onset.
II
Sinus pause/arrest: a sudden gap with no P wave.

02Sinus arrhythmia

Rate speeds with inspiration and slows with expiration. It's normal, especially in young people, and needs no treatment.

Clinical pearl. Sinus tachycardia above 150 in an adult is uncommon at rest; look hard for flutter waves or SVT.

Key takeaways

  • Same P morphology, 1:1, constant PR
  • Treat the cause of sinus tach, not the rate
  • Pauses > 3 s may need pacing evaluation