Sinus Sinus RhythmsRhythms

Electrical impulses that originate from the SA node.

Normal Sinus Rhythm (NSR)Normal Sinus Rhythm (NSR)

Rhythm: Regular

Rate: 60 – 100 bpm

P waves: Upright & uniform; precedes each QRS complex

PRI: 0.12 – 0.20 sec; constant

QRS: Narrow (< 0.10 sec); sometimes wide

***Interpretation: Normal Sinus Rhythm

Sinus Bradycardia (SB)Sinus Bradycardia (SB)

Rhythm: Regular

Rate: < 60 bpm

P waves: Upright & uniform; precedes each QRS complex

PRI: 0.12 – 0.20 sec; constant

QRS: Narrow (< 0.10 sec); sometimes wide

***Interpretation: Sinus Bradycardia (ST-segment depression ???)

Sinus Bradycardia (SB)Sinus Bradycardia (SB)

Normal with relaxation or sleep when parasympathetic effect is dominant over the SNS

Common in trained athletes (as low as 35 bpm)

Beneficial for some patients with cardiac insufficiencies (decreases the workload of the heart)

Sinus Bradycardia (SB)Sinus Bradycardia (SB)

• Vagal stimulation• Carotid sinus hypersensitivity syndrome

• Sleep apnea syndrome• Hypothyroidism, Hypothermia, hyperkalemia

• Sudden movement from recumbent to an upright position• Increased ICP

• Digitalis, CCB’s, & BB’s• Sick sinus syndrome (degenerative disease of the sinus node)

Sinus Tachycardia (ST)Sinus Tachycardia (ST)

Rhythm: Regular

Rate: > 100 bpm; < 160 bpm

P waves: Upright & uniform; precedes each QRS complex

PRI: 0.12 – 0.20 sec; constant

QRS: Narrow (< 0.10 sec); sometimes wide

***Interpretation: Sinus tachycardia

Sinus Tachycardia (ST)Sinus Tachycardia (ST)

Normal response of the heart to the body’s demand for increase

in blood flow

• Excitement, exertion, exercise• Fever, infections, septic shock

• Hypoxia, hypovolemia, hypotension, heart failure, hyperthyroidism

• Pain, PE, anxiety, anemia

Sinus Tachycardia (ST)Sinus Tachycardia (ST)

• Myocardial ischemia, MI

• Drugs that increase sympathetic tone (epinephrine, norepi, dopamine, TCA’s, isuprel, cocaine, nitroprusside)

• Drugs that decrease parasympathetic tone (atropine)

• Smoking, alcohol consumption, caffeine

Sinus Arrhythmia (SA)Sinus Arrhythmia (SA)

Rhythm: Irregular

Rate: 60 – 100 bpm; sometimes slower

P waves: Upright & uniform; precedes each QRS complex

PRI: 0.12 – 0.20 sec; constant

QRS: Narrow (< 0.12 sec); sometimes wide

***Interpretation: Sinus Arrhythmia

Sinus Arrhythmia (SA)Sinus Arrhythmia (SA)

Normal phenomenon caused by variations in autonomic tone

Associated with phases of respiration

Inspiration = Rate Increases

Expiration = Rate Decreases

Sinus PausesSinus PausesTwo Kinds:

Both originate from the sinus node

Sinus (Exit) Block & Sinus Arrest

Sinus ArrestSinus Arrest

Failure of the SA node to fire; a

disorder of automaticity.

Failure of the SA node to discharge

causes an irregularity of when the rhythm resumes following the pause

Sinus ArrestSinus Arrest

Rhythm: depends on underlying; pauses cause slight irregularity; does not resume on time after pause

Rate: depends on underlying

P waves: Upright & uniform; precedes each QRS complex

PRI: 0.12 – 0.20 sec; constant

QRS: Narrow (< 0.12 sec); sometimes wide

***Interpretation: NSR with a sinus arrest (??? Sec)

Sinus (Exit) BlockSinus (Exit) BlockElectrical impulse is

initiated by the SA node, but is BLOCKED

as it exits the sinus node preventing

conduction to the atria. SA node discharge not affected; regularity not disturbed after rhythm resumes following the

pause

                  

Sinus (Exit) BlockSinus (Exit) Block

Rhythm: depends on underlying; pauses cause slight irregularity; resumes on time after pause

Rate: depends on underlying

P waves: Upright & uniform; precedes each QRS complex

PRI: 0.12 – 0.20 sec; constant

QRS: Narrow (< 0.12 sec); sometimes wide

***Interpretation: NSR with a sinus exit block (??? Sec)

Sinus PausesSinus PausesCauses:

• Increase in vagal tone on the SA node

• Myocardial ischemia or infarction

• Use of certain drugs (digitalis, BB’s, or CCB’s)

May be short and asymptomatic

Significant length of a pause is greater than or equal to 3 seconds

SummarySummary• All sinus rhythms originate from the SA

Node

• P waves are upright & uniform

• Sinus rhythms are differentiated by rates

• All sinus rhythms are regular with the exception of _______________________

• Sinus Pauses – Two Types:___________

TIME TO WORKOUT!!!TIME TO WORKOUT!!!

ReferencesReferencesChernecky, C., et al. (2002). Real world nursing survival guide:

ECG’s & the heart. United States of America: W. B. Saunders Company.

Huff, J. (2006). ECG workout: Exercises in arrhythmia interpretation (5th ed.). United States of America: Lippincott, Williams & Wilkins.

Walraven, G. (1999). Basic arrhythmias (5th ed.). United States of America: Prentice-Hall, Inc.

www.madsci.com/manu/ekg_rhy.htm