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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