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