Rhythm Interpretation: 9.1-9.3

Escape beat

• If SA node does not generate an impulse, another part of the electrical system can generate it, causing a late heart beat called escape beat

• May be isolated or regular

Escape rhythm

• Created when an area other than the SA node acts as primary pacemaker of the heart

Abnormal rhythms

• Can also develop when parts of cardiac conduction system become irritable

• Hypoxia, MI, or other medical problems can cause this

• Irritable area can generate an impulse even when the SA node is working normally

• Ectopic focus or ectopic pacemaker

• Isolated early beats caused by ectopic foci are very common

Dysrhythmia

• Abnormal rhythms

• Rhythms that are too fast or too slow or that begin in an area of the heart other than SA node

• Cardiac rhythms can starts in 5 different areas of heart’s conduction system; each is named for where it begins

  • Sinoatrial node = sinus rhythm

  • Atria = atrial rhythm

  • AV junction = junctional

  • ventricles = ventricular

• Heart blocks/AV vlocks

  • Caused by problems in the conduction of electrical impulses between atria and ventricles

Normal characteristics of heart rhythms

1. determine Heart rate - 60-100 bpm

2. examine rhythm for regularity - regular R-R intervals

3. Note P wave - one before each QRS complex; all identical

4. Measure PR interval - 0.12-0.20 seconds

5. Measure QRS - <0.12 seconds

Underlying Rhythm and irregular complexes

• Underlying rhythm - basic rhythm of the patient’s heart

• Irregular complexes - abnormal heartbeats

Quick reference

• Sinus - Means the rhythm/complex begins in the sinus node

• Atrial - begins in the atria

• Junctional - begins in the area of the AV junction

• Ventricular - begins in the ventricles

• Supraventricular - begins somewhere above the ventricles

• Bradycardia - is slow

• Tachycardia - is fast

• Premature - comes earlier than expected

• Escape - comes later than expected

• Multifocal - originates from multiple locations in the heart

• Paroxysmal - comes and goes in bursts

• Uniform - stays the same

• Monomorphic - has a key feature (e.g., the QRS complex) that stays the same every time

• Polymorphic - has a key feature that changes from beat to beat

Sinus rhythms

• Originate in the sinoatrial node

• HR - 60-100bpm, regular rhythm, positive P-wave before each QRS complex, PR interval between 0.12-0.2 seconds, and a QRS complex <0.12 seconds.

Sinus Tachycardia

• Heart rate is fast (>100 bpm), but all other characteristics are normal

Sinus bradycardia

• Heart rate is slow (<60bpm) and all other characteristics are normal.

Sinus arrhythmia

• All characteristics are normal except R-R interval - this is irregular in sinus arrhythmia

• Rhythm does not repear with consistent timing

• Usually varies with patient’s breathing; increases with inhalation and decreases with exhalation

Sinus arrest//pause

• SA node does not initiate an impulse at the right time

• Creates pause in electrical activity

• Complexes are normal, but rhythm pattern is irregular

Symptomatic

• Experiencing cardiac symptoms

• Sinus bradycardia - can be normal for athletes or can be slowed due to parasympathetic nervous system, but can be associated with symptoms decrease CO, dizziness, weakness, fainting, chest pain, SOB, low BP, clammy skin, changes in mental status

• Sinus tachycardia; side effect of medication, response to stress, or heart’s reponse to the body’s need for additional oxygen

  • Fever, exercise, fear, and low blood volume are also possible causes

• Sinus Arrythmia happens naturally in some children and adults

  • Does not usually need to be reateded unless HR is slow enough to cause pronlems with circulation or CO

• Sinus arrest may be caused by SA node damage, medications, or increase vagal tone

  • When vagus nerve is stimulated by pain, the sight of blood, or straining to have a bowel movement, the HR may slow dramatically

• Decision to treat these conditions depends on how often the arrest happens. Some patients may be asymptomatic, other patients may be treated with medication.