Week 2- ECG Interperation Flashcards
What does each little box represents?
- 0.04 seconds
What does 1 large box represents?
- Each large 0.2 secs
What is the P wave?
- Formed as the impulse is generated in the atria and represents atrial depolarization
- Smooth, round, upright shape
- Immediately precedes the QRS
- Duration is less than 110 ms (less than 3 boxes)
What should you look for in P wave?
- Look for no P waves
- If a P wave is present but not followed by a QRS complex (not followed by a QRS this indicates there is a block)
- Can give clues to the pacemaker site
- P waves that vary in size and configuration
- Morphology: upright or inverse
- If P waves look different then their coming from somewhere else not the SA node
What is the PR interval?
- Amount of time it takes for the atria to depolarize and for the impulse to travel through the AV node
- Slightly delay that normally occurs
- Measured from the start of the P wave to the point at which the QRS complex begins
What is the QRS complex?
- Narrow, with sharply pointed waves, and has a duration of less than 0.12s (3 or less boxes)
- If QRS is wide this indicates a block somewhere
- Represents depolarization of simultaneously contracting ventricles
- Beginning of the Q wave to the end of the S wave
- Should follow each P wave
What is the T wave?
- Represents ventricular repolarization
- Asymmetric less than half the overall height of the QRS complex, and be oriented in the same direction as the overall QRS
- Typically have a slower upstroke and faster down stroke
What are the steps to reading an ECG Rhythm?
- What is the heart rate?
- Are the P waves present? Are they regular? Do they all look alike? Are they inverted, absent, or retrograde? Are their fibrillation of flutter waves?
- Is the PR interval less or greater than 0.20 seconds?
- Is the QRS complexes narrow or wide
- Ratio is there a P wave for every QRS
- Is the rhythm regular, regularly irregular, or irregularly irregular?
How can we determine heart rate?
The 6 second method
- simplest & most accurate when rhythm is irregular or between approx 50-100
- Count the number of QRS complexes in a 6 sec strip, multiply by 10
The sequence method
- Regular rhythms and strips less than 6s long
- 300, 150, 100, 75, 60, 50, 43, 38, 33
- Find R wave on a heavy line and count off until you reach the next R wave
How do we determine the rhythm regularity?
- Measure the distance between R waves is one method used to evaluate rhythm regularity
(Regular, regularly irregular, or irregularly irregular)
What are the categories of Dysrhythmias?
- Disorder of impulse formation
- Disorder of impulse conduction
- Artifact
Disorder of impulse formation
- SA node failure
- Other pacemakers
- Ectopic focuses
Disorders of impulse conduction
- Delayed or blocked in the heart
Artifact
- 60 cycle interference
- Poor contact
- Damaged cable
Characteristics:
- Rate- 60-100 bpm
- P waves present & upright
- PR normal
- QRS narrow
- Ratio 1:1
- Rhythm is regular
NORMAL SINUS RHYTHM
Characteristics:
- Rate normal range (increases with inspiration and slow with expiration)
- P waves present & upright
- PR interval normal
- QRS is narrow
- Ratio 1:1
- Rhythm is regularly irregular
- Bainbridge reflex: sudden changes in pressure
(normal finding in children and young adults)
SINUS ARRHYTHMIA
Characteristics:
- Rate less than 60 bpm
- P waves present & upright
- PR interval normal
- QRS is narrow
- Ratio 1:1
- Rhythm is regular
SINUS BRADYCARDIA
Characteristics:
- Rate 100-160 bpm
- P waves present & upright
- PR interval normal
- QRS is narrow
- Ratio is 1:1
- Rhythm is regular
(Paediatrics & children)
SINUS TACHYCARDIA
Characteristics:
- Rate 140-250 bpm
- S/S: heart pounding, out of breath, sweating, hypotensive, chest pain
- P waves buried under the preceding T wave
- PRI: N/A
- QRS narrow (<0.012 secs)
- Ratio: N/A
- Regular rhythm
(Fast, narrow complexes can’t make out P waves)
SUPRAVENTRICULAR TACHYCARDIA (SVT)
- Rate change is sudden and unexpected
- P waves may be seen during the slow phase
- Each section has a regular rhythm
- RE-entry or bypass tracts (WPW)
- Fast, narrow complex begins and ends abruptly
- Caused by re-entry syndromes
PAROXYSMAL SUPRAVENTRICULAR TACHYCARDIA (PSVT)
When does RE-entry Syndrome occur?
- Re-entrant arrhythmias occur when an electrical impulse recurrently travels in a tight circle within the heart
- When conduction is abnormally slow in some area (for example in heart damage) the myocardial cells are unable to activate the fast sodium channel
- Part of the impulse will arrive late and potentially be treated as a new impulse
(series of beats - sudden onset)
What is RE-entry Syndrome?
- In the AV node, a wave of depolarization encounters a region that is non-conductive and deviates around it.
Down the left limb, the waves continues
Down the right limb, the wave encounters a group of cells that are still refractory and the wave is blocked - The wave (impulse) of depolarization spreads to the rest of the heart causing it to contract and repolarize.
Meanwhile, the previously blocked conduction limb is now able to conduct slowly in retrograde direction. - Now the impulse re-enters a polarized or repolarizing region and gives rise to an ectopic focus that may generate a single beat or give rise to a series of consecutive beats
What is pre-excitation syndrome?
- Impulse from somewhere in the atria reach the ventricles sooner than one transmitted down the normal conduction pathway
- In some individuals, pre-excitation occurs because there exists a muscle fiber that penetrates the AV ring that normally isolates the 2
- This acts as an accessory pathway
What are the types of pre-excitation syndromes?
- WPW (kent bundle)
- Manheim Fibers
- LGL
What is WPW (Kent Bundle)?
- Pathway through the AV ring that bypasses the AV node. Conduction is up from the ventricles to the atria or vise- versa
What is Manheim Fibres?
- From the AV node, bundle of His or branches (AV node - accessory pathways and bundle branches simultaneously)
What is LGL?
- Bypass the AV node and goes directly to the bundle of His
Characteristics:
- Rate is generally slow to normal
- P waves present & upright (different morphology from the other P waves)
- PR interval normal
- QRS is narrow
- Ratio 1:1
- Rhythm is regular, except where disrupted by the pause
SINUS ARREST
What is sinus arrest?
- SA node fails to initiate an impulse
- Next beat after the pause will be out of sequence
- Patients with this dysrhythmia are candidates for pacemakers
Characteristics:
- Rate slow to normal
- P waves present, except when dropped
- QRS narrow
- Ratio 1:1
- Rhythm regular except when disrupted by dropped beats
SINUS EXIT BLOCK (SA BLOCK)
What is sinus exit block?
- Results from either the pacemaker cells or the transitional cells failing to produce an impulse
- After the dropped beat, the cycle continues on time
Premature Atrial Complex (PAC)
- Contraction ahead of the regular P wave
- Ectopic beats from somewhere in the atria (somewhere in the atrium)
- Similar or different morphology
- Irregular rhythm where the PAC disturbs the rhythm
- PRI can be normal or long
- P wave must be upright
Premature Junctional Complex (PJC)
- Contraction ahead of the regular P wave
- Ectopic beat from somewhere in the atria
- Similar or different morphology
- Irregular rhythm where the PJC disturbs the rhythm
- PRI can be
- P wave is inverted or retrograde
Characteristics:
- Rate 40-60 bpm
- P waves are absent, inverted, or retrograde (after T wave)
- PRI is normal, short or N/A
- QRS is usually narrow
- Ratio 1:1
- Regular rhythm
JUNCTIONAL RHYTHMS
What can cause a junctional rhythm?
- Sick sinus syndrome
- Severe bradycardia that allows the AV node to take over
- same etiology as junctional rhythms, however the rate is >100 bpm
Characteristics: - P waves- retrograde
- PR interval is short
- Regular rhythm
JUNCTIONAL TACHYCARDIA
What is fibrillation?
- Waves with no organization or regularity
- Indication of random electrical activity
- No viable cardiac output associated with fibrillating tissues
- Can be atrial or ventricular
Wavy Line
What is atrial fibrillation?
Multiple foci firing in the atria, but they don’t effectively depolarize the muscle tissues
- Atria does not contract
- 70% of the ventricles blood volume is reached passively as blood returns to the heart and flows between atria and ventricles
- Remaining blood volume stays in the atria
- Common cause of embolic stroke from the formation of micro clots
Characteristics:
- Rate will vary
- P waves not discernable
- PRI N/S
- QRS is usually narrow
- Ratio N/A
- Irregularly irregular rhythm- Hallmark of A-fib
ATRIAL FIBRILLATION
(little waves are fibrillation waves)
Characteristics:
- Atrial rate 200-350 bpm
- P waves have saw tooth appearance
- QRS usually narrow
- Ratio 2:1, 3:1, 4:1 and may vary
- Rhythm usually regular
ATRIAL FLUTTER
What is atrial flutter?
- Resulting from rapid firing of ectopic impulses from one of the atria
- AV node serve to protect the ventricles by limiting the number getting through
- It allows every second, third or fourth impulse to conduct to the ventricles
- Results in a 2:1, 3:1 or 4:1 conduction
What are the AV Blocks?
- 1st degree (long PR interval)
- 2nd degree- type I and II
- 3rd degree
- Ectopic beats
- Fibrillation
- Asystole
- PEA
Heart Blocks
- Delays are a normal function of the AV node
- Occasionally the impulses are delayed more than usual resulting in heart blocks
- Classified into different degrees based on the seriousness of the block and the amount of myocardial damage
Characteristics:
- Rate- depends on underlying rhythm
- P waves normal
- PR interval>0.20 secs
- QRS is narrow
- Ratio 1:1- one per QRS
- Rhythm is regular
1st DEGREE AV BLOCK
What causes 1st Degree AV block?
- Results from prolonged physiologic block in the AV node
- Can occur b/c of medication, vagal stimulation and disease- typically hemodynamically stable
Characteristics
- Rate- generally slow to normal
- P waves: present, stand alone
- PR Interval- PRI become increasingly longer until a beat is dropped
(the PRI before the dropped beat will be longer than the one after (long before, short after))
- QRS is narrow
- Ratio 1:!- one per QRS
- Rhythm is regularly irregular
2ND DEGREE TYPE I (WENKEBACH)
Characteristic:
- Rate: generally slow
- P waves present, stand alone
- PR Interval- when there are P waves associated with QRS the P-R interval will be constant
- QRS is narrow
- Ratio fixed ratio of 2:1, 3:1
- Rhythm is usually regular
2ND DEGREE, TYPE II
2nd Degree, Type II
- SA node fires at a normal rate but only every 2nd or 3rd impulse gets through
- Result of diseased or ischemic tissue in the AV node
What is 3rd degree (complete block)?
- Complete absence of AV conduction
- None of the supraventricular impulses are conducted to the ventricles
- Atria and ventricles firing separately
- One ventricle will fire after the other resulting in a wide QRS
- Typically a bradycardic rate due to intrinsic rate
- Narrow QRS can be seen if ectopic foci is located somewhere along the Bundle of His
Characteristics:
- Rate: slow 45 or below
- P waves: present, stand alone
- PR interval: N/A
- QRS: wide
- Ratio: N/A
- Rhythm: regular
THIRD DEGREE HEART BLOCK
Rhythms of the ventricles
- Ventricles may begin to originate their own impulse
- Missing P waves and wide QRS complexes
- Travels cell-to-cell
- 20 to 40 bpm
What is idioventricular?
- Occur when a ventricular focus acts as the primary pacemaker for the heart
Characteristics:
- Rate: 20-40 bpm
- P waves: absent
- PR N/A
- QRS is wide >0.12
- Ratio N/A
- Rhythm is regular
IDIOVENTRICULAR
What is accelerated idioventricular- AIVR?
- Faster version of an idioventricular rhythm
- Exceeds 40 bpm but remains under 100 bpm
- May represent serious cardiac disease
What is ventricular tachycardia?
- Extremely serious
- Characterized as 3 ventricular beats in a row
- May be short for be sustained
- Fast, regular wide complex rhythm
Characteristics:
- Rate 120-250
- P waves are not normally visualized
- PRI N/A
- QRS wide
- Ratio: N/A
- Rhythm usually regular
V-TACH
What is the difference Monomorphic V-tach vs Polymorphic V-tach?
Monomorphic: one shape
Polymorphic: in which there are multiple ventricular foci and the resultant QRS complexes vary in size and shape
What is Torsades de Pointes?
- Occur when there is an underlying prolonged QT interval
- A type of polymorphic v-tach
- Axis of the QRS complex changes from positive to negative in a haphazard fashion
- Means “twisting of points”
- Can convert to NSR or V Fib- treat this very carefully as it precursors/ notifier to death
What is premature ventricular complex (PVC)?
- Caused by the premature firing of the ventricular cell
- Ventricular pacer fires before the SA node, which causes the ventricles to be in a refractory state when the normal impulse tries to get through, causing the ventricles to not fire at their normal time
- the underlying pacing rhythm is not altered, so the beat following the PVC will arrive on time (this is a compensatory pause)
- Unifocal or multifocal
What is Multifocal vs Unifocal?
- Multifocal: arising from 2 or more ectopic foci
- Results in multiple QRS morphologies
- Unifocal: arising from a single ectopic foci
- Results in each PVC looking identcial
PVC’S can often occur in repeating patterns:
- Couplet- two consecutive PVCs
- Bigeminy- every other beat is a PVC
- Trigeminy- every third beat is a PVC
- Quadrigeminy- every fourth beat is a PVC
- Rhythm in which entire heart is no longer contracting
- Quivering without organized contraction, cardiac chaos
- Random depolarization of many cells
- Rhythm most commonly seen in cardiac arrests
- Responds well to defibrillation
- Can be coarse or fine
VENTRICULAR FIBRILLATION
- Flatline
- Entire heart is no longer contracting
- Many cells have no energy for contraction
- Generally a confirmation of death
ASYSTOLE
- Clinically dead or VSA
- There is a prescence of some form of electrical activity and a rhythm but the patient is apneic and pulseless
- CPR is indicated
PEA (PULSELESS ELECTRICAL ACTIVITY)
What are the 6H’s that cause PEA?
- hyperkalemia
- hypoxia
- hypothermia
- hydrogen ion access (acidosis)
- hypovolemia
- hypoglycemia
What are the 6T’s that cause PEA?
- tamponade (cardiac)
- Tension pneumothorax
- thrombosis (pulmonary embolism)
- thrombosis (myocardial infarction)
- toxins
- trauma
