Normal sinus rhythm is characterized by a regular rhythm originating from the sinus node between 60-100 beats per minute. Each impulse follows the normal conduction pathway with visible P waves preceding upright QRS complexes and normal PR and QT intervals. Normal sinus rhythm serves as the standard against which all other cardiac rhythms are compared.

1. Normal Sinus Rhythm

2. Normal Sinus Rhythm
• Description
– The sinus node is the pacemaker, firing at a
regular rate of 60 to 100 times per minute
• Conduction
– Each impulse follows the normal pathway of
conduction resulting in atrial and ventricular
depolarization

3. Normal Sinus Rhythm
• Normal sinus rhythm is the standard against
which all other rhythms are compared

4. Normal Sinus Rhythm
RATE RHYTHM P WAVE PR INTERVAL QRS
60-100 Regular Upright 0.12-0.20 0.11 or less

5. Normal Sinus Rhythm
• Atrial and ventricular rhythms are regular
• Atrial and ventricular rates fall between 60
and 100 beats/minute
– The SA node’s normal firing rate and all impulses
are conducted to the ventricles

6. Normal Sinus Rhythm
• P waves are rounded, smooth, and upright in
lead II, signaling that a sinus impulse has
reached the atria

7. Normal Sinus Rhythm
• PR interval is normal indicating that the
impulse is following normal conduction
pathways
– 0.12-0.20 seconds

8. Normal Sinus Rhythm
• The QRS complex is of normal duration
representing normal ventricular impulse
conduction and recovery
– Less than 0.12 seconds

9. Normal Sinus Rhythm
• The T wave is upright in lead II, confirming
that normal repolarization has taken place

10. Normal Sinus Rhythm
• The QT interval is within normal limits
– 0.36 to 0.44 seconds

11. Normal Sinus Rhythm
• No ectopic or aberrant beats occur

12. Normal Sinus Rhythm
• Characteristics of normal sinus rhythm
– Regular rhythm
– Normal rate
– A P wave for every QRS complex and all P waves
similar in size and shape
– All QRS complexes similar in size and shape
– Normal PR and QT intervals
– Normal (upright and round) T waves

13. Review
• Normal Sinus Rhythm
– P wave
– PR interval
– QRS complex
– ST segment
– T wave
– QT interval
– Normal U wave

14. NS Rhythm Review
• Normal P wave
– Before the QRS
– 0.06 to 0.12 second
– Usually rounded and upright

15. NS Rhythm Review
• Normal PR interval
– From the beginning of the P wave to the beginning
of the QRS complex
– 0.12 to 0.20 second

16. NS Rhythm Review
• Normal QRS complex
– Follows the PR interval
– 0.06 to 0.10 second
– Consists of the Q wave, the R wave, and the S
wave

17. NS Rhythm Review
• Normal ST segment
– From the S wave to the beginning of the T wave

18. NS Rhythm Review
• Normal T wave
– After the S wave
– Typically round and smooth

19. NS Rhythm Review
• Normal QT interval
– From the beginning of the QRS complex to the
end of the T wave
– Usually lasts from 0.36 to 0.44 second

20. NS Rhythm Review
• Normal U wave
– After T wave
– Typically upright and rounded

21. NS Rhythm Review
• Determine the rhythm
• Determine the rate
• Evaluate the P wave
• Measure the PR interval
• Determine the QRS complex duration
• Examine the T waves
• Measure the QT interval duration
• Check for ectopic beats and other abnormalities