Sinus Rhythms & Arrhythmias

Sinus Rhythms

• Impulse originates in SA node and are conducted normally through pathway

  • hence, sinotrial node generates a sinus rhythm

• expected to see:

  • P waves, QRS complexes, T waves

  • rhythm and rate may vary from pt to pt, but duration of PRI and QRS complex are within normal ranges and consistent throughout

Sinus rhythms may be classified as:

• Normal sinus rhythm (NSR)

• sinus tachycardia

• sinus bradycardia

Sinus Arrhythmia / Dysrhythmia

• impulse originates from SA node

• a normal physiological mechanism in response to phases of respiration

  • not a true arrhythmia

  • reason up to 3 box variation is still considered a “normal rhythm”

Atrial Arrhythmia

• Originate from an ectopic focus in the atria

  • when cells are deprived of O₂, may become irritable and originate its own beat

Junctional Arrhythmia

• Originate from Bundle of His at AV Junction

  • AV Junction = AV node + bundle of His

Ventricular Arrhythmia

• ectopic focus in ventricle takes over and creates own beat

  • similar to atrial arrhythmia

• no P wave seen

  • b/c P wave represents atrial depolarization

• QRS complex will be ‘wide and bizarre’ in appearance

Clues for Arrhythmias:

• Check relation between P waves and QRS

  • clues can help:

    • eliminate most possibilities

    • point to one or two specific patterns

  • gray area exists

    • may not always be possible to classify

Causes of Arrhythmias:

• Ischemia

  • Angina

    • Chest pain (CP) d/t CA

      • vasoconstriction / vasospasm

• Hypoxemia

  • oxygen deficiency in arterial blood

• Ideopathic

• Anxiety

• Trauma

• Birth Defects

  • ASD

  • VSD

Causes of Arrhythmias:

• Vagal Stimulation (slows AV conduction, slowing HR)

  • gagging

  • vomiting

  • straining w/ BM

  • carotid massage

  • sleeping

  • digitalis Tx

    • slows impulse transmission to increase force of contraction

• Drugs

  • heart meds

  • stimulants

  • depressants

  • caffeine

  • tobacco

Normal sinus rhythm (NSR)

• site of impulse: SA node

• rate: 60-100 BPM

• rhythm: regular for atria and ventricle

• P waves: normal

  • uniform

  • upright

  • one to precede each QRS

• PRI: normal

  • 0.12 - 0.2 s and constant

• QRS: normal

  • 0.06 - 0.10 s

  • or just <0.12 s

• Etiology → none

  • this is the normal cardiac pattern

Sinus Bradycardia

• rate: <60 BPM

• rhythm: regular

• site of impulse: SA node

• P waves: normal

• PRI: normal

• QRS: normal

Sinus Bradycardia etiology:

• normal in athletes

• decreased metabolic rate

  • hypothermia

• increased intracranial pressure

• acute MI

• vagal stimulation

Significance of sinus bradycardia:

• may proceed blocks or asystole

• may precipitate escape rhythms

Sinus bradycardia signs / symptoms:

• slow, regular pulse

• decreased cardiac output → CHF

  • swollen, edematous legs (Rt rided CHF)

  • SOB, hemoptysis (Lt sided CHF)

Sinus bradycardia treatment:

• meds: Atropine and Isuprel

  • speed up heart rate

• Pacemaker

• Tx underlying cause (if known)

Sinus Tachycardia

• rate: >100 BPM

• rhythm: regular

• site of impulse: SA node

• P waves: normal

• PRI: normal

• QRS: normal

Causes of Sinus Tachycardia:

• normal in children

  • <10 yrs

• increased metabolic demands

  • fever

  • pain

  • anxiety

  • fear

  • exercise

• stimulants

  • caffeine

  • nicotine

  • cocaine

• compensation for beginning stage of decreased cardiac output

  • shock

  • CHF

Sinus Tachycardia signs / symptoms:

• rapid, regular pulse

• usually asymptomatic

• may report heart “racing”

• palpitations

• dyspnea / SOB

Sinus Tachycardia treatment:

• meds: Beta Blockers

  • Propranolol, Acebetolol, and Verapamil

  • Slow heart rate

• Tx underlying cause (if known)

Sinus Arrhythmia

• not a true arrhythmia

  • a normal physiological mechanism due to breathing

• represents the normal and extremely minimal variations in the SA node’s pacing rate in associated with the phases of respiration

  • increase in HR during inspiration

  • decrease in HR during expiration

Sinus Arrhythmia

• rate: 60-100 BPM

• rhythm: Irregular

• site of impulse: SA node

• P waves: normal

• PRI: normal

• QRS: normal

Sinus arrhythmias are common in:

• children

• young adults

• elderly

Sinus arrhythmia clinical presentation:

• pt has irregular pulse

• no treatment required