Transcript EKG Extravaganza!

EKG Extravaganza!
Michele Ritter, M.D.
Argy Resident – Feb. 2007
Normal Conduction of the Heart
 SA node
 Left/Right atrium
 Atrial Contraction
 AV node
 Bundle of His
 Purkinjie fibers
 Endocardium
 Epicardium
 Ventricular
contraction
Generation of EKG
Generation of EKG
 P wave:
 = depolarization/contraction of both atria
 QRS complex:
 = depolarization/contraction of ventricles
 T wave
 = rapid phase of ventricular repolarization
 ST segment
 = plateau phase of ventricular repolarization
 QT interval
 = ventricular systole
ECG Leads
 Limb Leads

Bipolar


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
Lead I – left arm (+)
and right arm (-)
Lead II – left leg (+)
and right arm (-)
Lead III – left leg (+)
and right leg (-)
Unipolar



aVR - right arm
potentials
aVL – left arm
potentials
aVF – left leg
potentials
 Precordial Leads


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
V1
V2
V3
V4
V5
V6
Precordial Leads
Reading EKGs
1. Rate
2. Rhythm
3. Axis
4. Hypertrophy
5. Infarction
Rate
 Large Box = 0.2 seconds
 Small Box = 0.04 seconds
Rate
 300-150-100-75-60-50 Rule
 If one box between R-waves, then rate is 300;
If two boxes between, then rate 150, etc.
 Rate = 1500/(mm between R waves)
What is the rate?
Rhythm
 Is the rhythm regular (distance between QRS
complexes equal)?
 Is there a P-wave before every QRS
complex?
 Is the PR interval normal?

0.12 sec - 0.20 sec
 Is the QRS duration normal?

0.04 sec to 0.12 sec
Irregular Rhythms
 Usually caused by multiple, active
automaticity sites that causes irregular atrial
and ventricular activity
 Include:



Wandering Pacemaker
Multifocal Atrial Tachycardia
Atrial Fibrillation
Irregular Rhythms
 Wandering Pacemaker



Have P’ waves (not true P waves because
pacemaker activity is wandering from SA node
to a nearby atrial automaticity foci)
Atrial Rate less than 100
Irregular shape to P waves and irregular
ventricular rhythm.
Irregular Rhythms (cont.)
 Multifocal Atrial Tachycardia
 Think of it as tachycardic wandering pacemaker
 P’ waves again
 Atrial rate excees 100
 Irregular ventricular rhythm
 Irregular morphology of P’ waves
 Occurs in:
 COPD
 Heart Disease
Irregular Rhythm (cont.)
 Atrial Fibrillation



No P waves (because there are multiple atrial automaticity
foci sending impulses – no single impulse depolarizes atria
completely)
Irregular ventricular rhythm
Caused by:




Heart disease (CAD, CHF)
Thyroid disease
Pericardial effusion
Alcohol
Tachy-arrhythmias
 Rapid rhythms
originating in a very
irritable foci that paces
rapidly.
 Includes:
Paroxysmal Tachycardia
Rate Range
150 to 250
Flutter
250 to 350
Fibrillation
350 to 450
Atrial Tachyarhythmias
 Supraventricular tachycardia
 Includes paroxysmal junctional tachycardias
Paroxysmal Atrial Tachycardia and Paroxysmal
Junctional Tachycardia
 Caused by very irritable automaticity foci that originate
above the ventricles.
 Narrow QRS complex tachycardia
 Have P’ waves – often get lost in QRS.
Supraventricular arrhythmias
Atrial Tachyarrhythmias (cont.)
 Torsades de Pointes
 Rate is usually 250 to 350 beats/min.
 The amplitude of each successive complex gradually
increases and then gradually decreases – “party
streamer”
 Caused by:
 Severe hypokalemia
 Medications that block potassium channels
 Congenital abnormality (Long QT syndrome)
Atrial Tacchyarrhythmia
 Atrial Fibrillation

Rapid Ventricular Response = increased heart
rate, putting patient at risk for hypotension.
Atrial Tachyarrhythmias (cont.)
 Atrial Flutter

Extremely irritable atrial focus produces a
rapid series of atrial depolarizations (250-350
beats/min.)
Ventricular tacchyarrythmias (cont.)
 Paroxysmal Ventricular Tachycardia



Is like a run of PVC’s
Irritable (hypoxic) ventricular focus results in
rapid rate that is too fast for heart to function
effectively.
WIDE QRS COMPLEX tachycardia
Ventricular Tacchyarhythmia (cont.)
 Ventricular Fibrillation



Caused by rapid-rate discharges from many irritable,
parasystolic entricular automaticity foci.
An erratic, rapid twitching of the ventricles, with
ventricular rate reaching 350 to 450 beats/min.
Tracing is totally erratic, without identifiable waves.
Tacchyarrhythmia
 Wolff-Parkinson-White syndrome



A ventricular “pre-excitation” arrhythmia
An abnormal, accessory AV conduction pathway, the bundle
of Kent, can “short circuit” the usual delay of ventricular
conduction in the AV node.
Results in


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
Shortened PR interval (< 0.12 sec)
Widened QRS (> 0.12 sec)
Delta waves
Can result in several tachyarrhythmias including
supraventricular tachycardia, atrial flutter, atrial fibrillation
Blocks
 Sinus Block
 AV Block
 Bundle Branch Block
Sinus Block
 SA node fails to pace for at least complete cycle.
 Occurs in:
 Sick Sinus Syndrome (SSS)
 SA node dysfunction resulting recurrent episodes of
sinus block or sinus arrest
 Frequently occurs in elderly patients with heart
disease.
 Bradycardia-Tachycardia Syndrome
 Patients with SSS who develop episodes of
supraventricular tachycardia mingled with sinus
bradycradia.
AV Block
 1° (first degree) AV Block
 Prolongs AV node conduction
 Prolonged PR interval (>0.2 sec – one big
box)
 The PR interval is consistently prolonged the
same amount in every cycle
 P-QRS-T sequence is normal in every cycle.
AV Block (cont.)
 2° (second degree) AV Block

Wenckebach (Mobitz Type I)




Gradually prolongs the PR interval , until the final P wave fails
to produce a QRS response.
This cycle then repeats itself.
Usually non-pathologic
Mobitz (Mobitz Type II)


Totally blocks a number of paced atrial depolarizations (P
waves) before conduction to the ventricles is successful.
Can be:
 2:1 – two P waves to every QRS
 3:1 – three P waves to every QRS

Usually permanent, and can progress to complete heart block
2° AV Block – “Wenckebach”
2° AV Block - Mobitz
2:1
3:1
AV Block - 2° AV block (cont.)
 If see 2:1 AV block and uncertain if
Wenckebach or Mobitz…



Do vagal maneuver
If Wenckebach, there is an increase the
number of cycles/series (increasing to 2:3 or
4:3)
If Mobitz (Type II), it becomes a 1:1 AV
conduction.
AV Block (cont.)
 3° (third degree) AV block:
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
“Complete Heart Block”
Complete block of the conduction to the ventricles, so
atrial depolarizations are not conducted to the
ventricles.
See a sinus-paced atrial (P wave) rate and a totally
independent, focus-pased, slow ventricular (QRS rate)
– AV dissociation.
Can have:
 Junctional Focus
 Normal (narrow) QRS
 Ventricular rate: 40-60/min.

Ventricular Focus
 PVC-like QRS’s
 Ventricular rate: 20-40/min.
AV Block (cont.)
 3° (third degree) AV Block
Bundle Branch Block
Bundle Branch Blocks
 Caused by block of conduction in the right or left
bundle branch.
 The bundle branch delays depolarization to the
ventricles that it supplies.
 Left Bundle Branch Block (LBBB)



Associated with cardiovascular disease!
Incidence increases greatly with age.
Think – V5, V6!!
 Right Bundle Branch Block (RBBB)
 Associated with structural heart disease, increased
age, sometimes iatrogenic (cardiac cath.)
 Think – V1, V2!!
Bundle Branch Block
Left Bundle Branch Block
 Widened QRS (> 0.12 sec, or 3 small
squares)
 Two R waves appear – R and R’ in V5 and
V6, and sometimes Lead I, AVL.
 Have predominately negative QRS in V1, V2,
V3 (reciprocal changes).
Right Bundle Branch Block
 Widened QRS (> 0.12 sec or 3 small
squares)
 R and R’ in V1 and V2, often with ST
depression and T wave inversion.
 Reciprocal changes (big negative S) in
V5,V6, I and AVL.
Right Bundle Branch Block
Bundle Branch Block
 Final Note:

If you have the above changes with R and R’,
but a normal (not widened) QRS, it is referred
to as an incomplete bundle branch block.
Axis
 The direction of depolarization as it passes
through the heart.
 A vector towards a lead results in a positive
deflection on the ECG, while a deflection
away from a lead results in a negative
deflection.
 If hypertrophy is present, the overall vector
(axis) points towards the hypertrophied part.
Axis
Frontal Plane
Horizontal Plane
Axis
 Normal Axis: QRS vector pointed downard
and to the patient’s left, in the 0 to 90° Range.
 Right axis Deviation: > 100°
 Left axis Deviation: < 0°
Axis – the nitty gritty
 QRS net positive in Lead I and AVF: normal axis
 QRS net positive in Lead I and net negative in AVF: Left axis Deviation
 QRS net negative in Lead I and net positive in AVF: Right axis Deviation
AVF
Axis
 Left Axis Deviation:

Can occur in:
 Left Ventricular Hypertrophy (hypertension!)
 Inferior myocardial infarction
 Right Axis Deviation:

Can occur in:
 Right ventricular overload (cor pulmonale)
 Left pneumothorax
 Lateral myocardial infarction.
Hypertrophy – we’re going to
essentials only.
 Left Ventricular Hypertrophy


Important because it is often a sign of longstanding hypertension!
Calculation:

mm of S in V1
+

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
mm of R in V5
If sum is more than 35 mm, you have LVH!!!
Remember, you usually see Left axis deviation with LVH.
Now the most important….
MYOCARDIAL
INFARCTION !!!!
EKG in Myocardial Infarction
 Gives information about:

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Duration — hyperacute/acute versus
evolving/chronic
Extent — transmural versus subendocardial
Size — amount of myocardium affected
Localization (which area of heart affected)
 Difficult to use EKG in certain situations:


Left bundle branch block
Paced rhythm
EKG in myocardial infarction
 Ischemia: T waves
 Injury: ST changes
 Necrosis: Q waves
Myocardial Ischemia
 Represented by inverted T waves.
 Should be symmetrically inverted.
 Can be marker of OLD infarction
 Wellens syndrome: Marked T wave inversion in V2
and V3, which alerts to stenosis of the left anterior
descending coronary artery (LAD)
Myocardial Injury
 Injury = “acute” or
“recent” ischemia.
 ST changes show that
the episode is acute.
 Transmural injury

ST Elevation
 Subendocardial injury

ST Depression
ST elevation
ST depression
Myocardial Necrosis
 Q wave:

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Diagnostic for myocardial infarction.
Can have MI in its absence (non Q-wave MI)
Can be acute or old! (Use ST changes to determine if
acute)
Is significant if at least one small square (1 mm or 0.4
seconds in duration)
Is usually at least 1/3 of the QRS amplitude
Location of Infarction

Posterior
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Inferior

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R or L coronary artery
ST changes/Q waves in II, III, AVF
May have reciprocal ST depressions
in I and AVL
Lateral
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
Right Coronary Artery
Large R, ST depressions in V1, V2,
V3
Circumflex artery
ST changes/Q waves in I and AVL,
V5, V6
May have reciprocal ST depressions
in II, III, AVF.
Anterior


Left Anterior Descending artery
ST changes/Q wave in V1, V2, V3,
V4
Where’s the MI?
Where’s the MI?
Where’s the MI?
Final one…
EKG - Conclusion
Rate
2. Rhythm
1.
1.
2.
Regular, irregular, irregularly irregular?
P waves? PR interval? QRS duration?
Axis
4. Hypertrophy
5. Ischemic Changes
3.
1.
2.
3.
T wave changes?
ST changes?
Q waves