introduction to ecgs - aast
TRANSCRIPT
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Introduction to ECGsR. Gentry Wilkerson, MDAsst. ProfessorDepartment of Emergency Medicine
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Objectives
Lead Placement
Hexaxial System
ECG Paper
Systematic Approach to Reading an ECG
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Lead Placement
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Hexaxial System
• Limb Leads (Bipolar): RA, LA, RL, LL
• Forms Einthoven’s Triangle
• I : 0º
• II : 60º
• III : 120º
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Hexaxial System
• Augmented Leads (Unipolar)
• Utilize a central negative terminal
• aVL : -30º
• aVF : 90º
• aVR : -120º
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Hexaxial System
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Precordial Leads
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1 mm x 1 mmHeight = millivolts
Width = Time
ECG Paper
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Calibration
Vertical Axis‘y’
1 Small Square = 1 mm (0.1 mV)Vertical Axis
‘y’ 1 Large Square = 5 mm (0.5 mV)Vertical Axis‘y’
2 Large Squares = 10 mm (1 mV)
Horizontal Axis‘x’
1 Small Square = 0.04 secHorizontal Axis
‘x’ 1 Large Square = 0.2 secHorizontal Axis‘x’
5 Large Squares = 1 sec
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I
aVL
HIGH LATERAL
II
III aVF
V1
V2
V3
V4
V5
V6
LATERAL
INFERIOR
SEPTAL ANTERIOR
RHYTHM STRIP
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ECG Complex
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Interpreting the ECG
•Rate
•Rhythm
- Ectopic beats?
•Axis
• Intervals
- Blocks?
•Atrial Abnormalities
•Ventricular hypertrophy
• ST/T changes
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The Rate
• 5 big boxes = 1 sec
• 300 big boxes = 60 sec
•Rate = 300/# big boxes
300
150
100 75 60 50
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The Rate
•Multiply # beats on rhythm strip x 5
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The Rhythm
• Is it fast or slow?
• Is it regular or irregular?
•Are there p waves present?
•Are all p waves the same?
•Does each QRS have a p wave?
• Is the PR interval constant?
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The Rhythm
•Are the p waves and QRS complexes associated with each other?
•Are the QRS complexes narrow or wide?
•Are the QRS complexes grouped or not?
•Are there dropped beats?
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The Rhythm
SupraventricularRhythms
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Normal Sinus Rhythm
•Rate: 60 - 100 bpm
•Regular
• P wave present
• P:QRS ratio: 1:1
• PR Interval: Normal
•QRS width: Normal
•Grouping: None
•Dropped: None
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Sinus Bradycardia
•Rate: Less than 60
•Regular
• P wave present
• P:QRS ratio: 1:1
• PR Interval: Normal
•QRS width: Normal
•Grouping: None
•Dropped: None
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Sinus Tachycardia
•Rate: Greater than 100
•Regular
• P wave present
• P:QRS ratio: 1:1
• PR Interval: Normal
•QRS width: Normal
•Grouping: None
•Dropped: None
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Sinus Arrhythmia
•Rate: 60 - 100
•Varies with respiration
• P wave present
• P:QRS ratio: 1:1
• PR Interval: Normal
•QRS width: Normal
•Grouping: None
•Dropped: None
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Sinus Pause / Arrest
•Rate: Varies
• Irregular
• P wave present
• P:QRS ratio: 1:1
• PR Interval: Normal
•QRS width: Normal
•Grouping: None
•Dropped: None
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Sinoatrial Block
•Rate: Varies
• Irregular
• P present except in areas of dropped beat
• P:QRS ratio: 1:1
• PR Interval: Normal
•QRS width: Normal
•Grouping: None
•Dropped: Yes
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Ectopic Atrial Tachycardia
•Rate: Greater than 100
•Regular
• P wave present
• P:QRS ratio: 1:1
• PR Interval: Normal
•QRS width: Normal
•Grouping: None
•Dropped: None
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Ectopic Atrial Tachycardia
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Wandering Atrial Pacemaker
•Rate: Less than 100
• Irregularly irregular
• P wave ≥ 3 morphologies
• P:QRS ratio: 1:1
• PR Interval: Varies
•QRS width: Normal
•Grouping: None
•Dropped: None
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Multifocal Atrial Tachycardia
•Rate: Greater than 100
• Irregularly irregular
• P wave ≥ 3 morphologies
• P:QRS ratio: 1:1
• PR Interval: Varies
•QRS width: Normal
•Grouping: None
•Dropped: None
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Atrial Flutter
•Rate: atrial- 250-350, ventricular 125-175
•Usually regular
• P wave- flutter waves
• P:QRS ratio: Often 2:1
• PR Interval: Variable
•QRS width: Normal
•Grouping: None
•Dropped: None
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Atrial Fibrillation
•Rate: Variable
• Irregularly irregular
• P waves chaotic
• P:QRS ratio: None
• PR Interval: None
•QRS width: Normal
•Grouping: None
•Dropped: None
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•Rate: 40-60
•Regular
• P waves- none, antegrade, retrograde
• P:QRS ratio: None or 1:1
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Junctional Rhythm
• PR Interval: None, short or negative
•QRS width: Normal
•Grouping: None
•Dropped: None
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Accelerated Junctional Rhythm
•Rate: 60-130 bpm
•Regular
• P waves- none, ante-, retrograde
• P:QRS ratio: none or 1:1
• PR Interval: None, short or neg
•QRS width: Normal
•Grouping: None
•Dropped: None
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The Rhythm
Ventricular Rhythms
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Idioventricular Rhythm
•Rate: 20 - 40 bpm
•Regular
• P wave absent
• P:QRS ratio: None
• PR Interval: None
•QRS width: Wide, bizarre
•Grouping: None
•Dropped: None
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Accel. Idioventricular Rhythm
•Rate: 40 - 100 bpm
•Regular
• P wave absent
• P:QRS ratio: None
• PR Interval: None
•QRS width: Wide, bizarre
•Grouping: None
•Dropped: None
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Ventricular Tachycardia
•Rate: 100 - 200 bpm
•Regular
• P wave ?buried
• P:QRS ratio: None
• PR Interval: None
•QRS width: Wide, bizarre
•Grouping: None
•Dropped: None
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Ventricular Tachycardia
• Fusion Beats
•Mix between V-tach and sinus morphologies
•Capture Beats
• Sinus morphology
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Ventricular Tachycardia
• Josephson’s Sign
• Small notching near the low point of S wave
• Brugada’s Sign
• Interval from R wave to bottom of S wave is ≥ 0.10 seconds
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Torsades de Pointes
•Rate: 200 - 250 bpm
• Irregular
• P wave: None
• P:QRS ratio: None
• PR Interval: None
•QRS width: Variable
•Grouping: N/A
•Dropped: None
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Ventricular Fibrillation
•Rate: Indeterminate
• Irregular
• P wave: None
• P:QRS ratio: None
• PR Interval: None
•QRS width: None
•Grouping: None
•Dropped: No beats
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Axis
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Axis
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Axis
• The axis is the direction of the sum vector of ventricular depolarization
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Axis
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Axis
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Axis
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Axis
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Intervals
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PR Interval•Normal: 0.12 to 0.20 sec
• Short PR interval
•Wolff-Parkinson-White
• Lown-Ganong-Levine
•AV Junctional Rhythm (see arrhythmia lecture)
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Wolff-Parkinson-White•Defined by:
• Short PR (<0.12 sec) with normal P wave
• May be normal in 12%
• Wide QRS complex (≥0.11 sec)
• Presence of a delta wave
• ST-T wave changes
•Association with paroxysmal tachycardias
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PR Interval• Normal: 0.12 to 0.20 sec• Long PR interval – 1st Degree AV Block
• AV nodal disease• Enhanced vagal tone• Myocarditis• Myocardial infarction (especially inferior MIs)• Electrolyte imbalance• Drugs (Beta Blockers, CCBs, cardiac
glycosides)
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QRS Duration
•Normal : 0.06 to 0.10 sec• Hyperkalemia• Ventricular tachycardia• Idioventricular rhythms• Drug effects and overdoses• Wolff-Parkinson-White• BBBs and Intraventricular conduction delay• PVCs• Aberrantly conducted complexes
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QT Interval• Must be corrected for rate = QTc
• Bazett’s Formula• Fridericia’s Formula• Hodge’s Formula
• Normal is < 440
3QTC = QT + 1.75 (HR – 60)
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QTC
• Causes of shortened QTc
• Hypercalcemia• Digitalis• Tachycardia
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QTC
• Causes of prolonged QTc
• Hypocalcemia• Drugs (Quinidine, Procainamide, Psychotropics,
Tricyclics, Pentamidine)• CNS• Hypothermia• Hypothyroidism• Ischemic Heart Disease• Genetic (Long QT Syndrome)
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Torsades de Pointes• Increased risk when QTc > 500 msec
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Heart Blocks
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Atrioventricular (AV) Block
•Conduction between the atria and ventricles is altered
•Abnormality can be located anywhere in the AV node, His bundle, or bundle branches
•May result in either a partial or complete block
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1st Degree AV Block
• Every atrial impulse conducts to the ventricles and a regular ventricular rate is produced
• PR interval exceeds 0.20 sec (5 boxes) in adults•Almost always asymptomatic• Etiology
•Medications•Age• Increased vagal tone
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1st Degree AV Block
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2nd Degree AV Block (Mobitz I- Wenckebach)
• Progressive prolongation of AV conduction (and the PR interval) until an atrial impulse is completely blocked
•Conduction ratios are used to indicate the ratio of atrial to ventricular depolarizations• 3:2 indicates that two of three atrial impulses
are conducted into the ventricles
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2nd Degree AV Block (Mobitz I- Wenckebach)
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2nd Degree AV Block (Mobitz II)• PR interval remains constant before and after the
non-conducted atrial beats
•Usually occur in the infranodal conducting system
•Often have co-existing fascicular or BB blocks
•Often due to permanent structural defects in the infranodal conducting system
•May progress suddenly to complete heart block
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2nd Degree AV Block (Mobitz II)
•RR interval surrounding the dropped beat(s) is an exact multiple of the preceding RR interval
• If there is 2:1 conduction, one cannot differentiate between Mobitz I and II
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3rd Degree AV Block (Complete Heart Block)
•Complete absence of AV conduction
• Perfusing rhythm is maintained by a junctional or ventricular escape rhythm
•Regular P-P intervals, R-R intervals
•Variable P-R intervals
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AV Dissociation• Term indicates only the occurrence of independent
atrial and ventricular contractions• Passive Type- default or "escape" like in third
degree AV block •Active Type- when the ventricular rhythm
usurps control•May be caused by entities other than complete
heart block•Accelerated Idioventricular Rhythm•Ventricular Tachycardia
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Right Bundle Branch Block
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Right Bundle Branch Block
• Major Criteria• QRS ≥ 0.12 sec• Slurred S wave in leads I and V6• RSR’ pattern in V1• May get a QR’ pattern if there is previous
anteroseptal infarct
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Right Bundle Branch Block
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Right Bundle Branch Block
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Left Bundle Branch Block
• Major Criteria• QRS ≥ 0.12 sec• Broad, monomorphic R waves in I and V6 with no
Q waves• Broad, monomorphic S waves in V1• May have a small r wave
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Left Bundle Branch Block
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Left Bundle Branch Block
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Left Bundle Branch Block
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Left Ventricular Hypertrophy
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Left Ventricular HypertrophyCompare these two 12-lead ECGs. What stands out as
different with the second one?
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Left Ventricular HypertrophyAs the heart muscle wall thickens there is an increase in
electrical forces moving through the myocardium resulting in increased QRS voltage
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Criteria for LVH
Gubner-Ungerleider 1943 RI > 15
RI + SIII > 25
Sokolow-Lyon 1949 SV1 + R(V5 or V6) > 35
RaVL > 11
Siegel 1982 Total 12-Lead voltage > 175
Murphy 1984 S(V1 or V2) + R(V5 or V6) > 35
Cornell (Casale) 1985 SV3 + RaVL > 28 (♂) 20 (♀)
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Right Ventricular Hypertrophy
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Right Ventricular Hypertrophy
• Right Axis Deviation
• R > S in V1
• Deep S in left precordial leads
• Slight prolongation of QRS up to 120 msec
• Strain pattern in V1-3
• May have right atrial abnormality
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Causes of R > S in V1
• Right Ventricular Hypertrophy• True Posterior MI• Lead Misplacement• RBBB• WPW Type A • Normal variant
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Q Waves
• Significant if:• More than 1/3 height of QRS• Wider than 0.03 sec
• Septal Qs (normal variant)• Result of initial depolarization occurring in the
septum from left to right• Often found in left sided leads: I, aVL and V6
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Q Waves
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ST Segment
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ST Segment Elevation
• ST elevation > 1 mm in limb leads and > 2 mm in chest leads indicates an evolving acute MI until proven otherwise.
• Other primary causes:• Early repolarization (normal variant) • Pericarditis• Ventricular aneurysm• Pulmonary embolism
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STEMI Localization
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ST Segment Depression
• Primary Causes• Myocardial Ischemia• LVH• Intraventricular conduction defects• Medication (digitalis)• Reciprocal changes in leads opposite area of acute
MI
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Sgarbossa Criteria
• For detecting an AMI in the setting of LBBB • Derived from the GUSTO-1 trial• Not perfect in screening for AMI. Use as another data
point for risk-stratifying.• Sgarbossa criteria hold true for LBBB pattern seen in
pacemaker patients
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Sgarbossa Criteria
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Pericarditis
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Pericarditis
• Stage I• First few days → 2 weeks• ST elevation, PR depression• Up to 50% of pt with symptoms / rub do NOT have
or evolve into stage I
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Pericarditis – Stage I
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Pericarditis – Stage II
• Stage II• Lasts days → weeks• Normalization of ST and PR segments• ST returns to baseline, flat T waves
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Pericarditis – Stage II
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Pericarditis – Stage III
• Stage III• Begins after 2-3 weeks, lasts several weeks• Widespread T wave inversion
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Pericarditis – Stage III
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Pericarditis – Stage IV
• Stage IV• Lasts up to several months• Gradual resolution of T wave changes
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Osborn Waves
• Positive deflections occurring at the junction between the QRS complex and the ST segment, the J point, has a myocardial infarction-like elevation
• Associated with hypothermia
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Osborn Waves
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Last night....
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Questions?