Normal Sinus Rhythm
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
Normal Sinus Rhythm
• Normal sinus rhythm is the standard against which all other rhythms are compared
Normal Sinus Rhythm
RATE RHYTHM P WAVE PR INTERVAL QRS
60-100 Regular Upright 0.12-0.20 0.11 or less
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
Normal Sinus Rhythm
• P waves are rounded, smooth, and upright in lead II, signaling that a sinus impulse has reached the atria
Normal Sinus Rhythm
• PR interval is normal indicating that the impulse is following normal conduction pathways– 0.12-0.20 seconds
Normal Sinus Rhythm
• The QRS complex is of normal duration representing normal ventricular impulse conduction and recovery– Less than 0.12 seconds
Normal Sinus Rhythm
• The T wave is upright in lead II, confirming that normal repolarization has taken place
Normal Sinus Rhythm
• The QT interval is within normal limits – 0.36 to 0.44 seconds
Normal Sinus Rhythm
• No ectopic or aberrant beats occur
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
Review
• Normal Sinus Rhythm– P wave– PR interval– QRS complex– ST segment– T wave– QT interval– Normal U wave
NS Rhythm Review
• Normal P wave– Before the QRS– 0.06 to 0.12 second– Usually rounded and upright
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
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
NS Rhythm Review
• Normal ST segment– From the S wave to the beginning of the T wave
NS Rhythm Review
• Normal T wave– After the S wave– Typically round and smooth
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
NS Rhythm Review
• Normal U wave– After T wave– Typically upright and rounded
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
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