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Cardiovascular System ANALYSIS Dr.Mohammed Sharique Ahmed Quadri Asst. P rofessor P hysiology Almaarefa College. ELECTROCARDIOGRAM (ECG). بسم الله الرحمن الرحيم. The 12-Leads. The 12-leads include:. 3 Limb leads (I, II, III). 3 Augmented leads (aVR, aVL, aVF). - PowerPoint PPT Presentation
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Cardiovascular System
ANALYSIS Dr.Mohammed Sharique Ahmed Quadri
Asst. Professor PhysiologyAlmaarefa College
الرحيم الرحمن الله بسم
1
THE 12-LEADS
The 12-leads include:
–3 Limb leads (I, II, III)
–3 Augmented leads (aVR, aVL,
aVF)–6 Precordial leads
(V1- V6)2
VIEWS OF THE HEART
Some leads get a good view of the:
Anterior portion of the heart(V1,V2,- setum V3,V4-)- anterior
Left Lateral portion of the heart( I , Avl, v5,v6)
Inferior portion of the heartII, III, aVF
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BASIC COMPONENTS
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THE “PQRST”
P wave - Atrial depolarization
• T wave - Ventricular repolarization
• QRS - Ventricular depolarization
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THE PR INTERVAL
Atrial depolarization +
delay in AV junction (AV node/Bundle of His)
(delay allows time for the atria to contract before the ventricles contract)
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SEGMENTS & INTERVALS
PR interval: 0.12 – 0.20 sec QRS interval : 0.08 – 0.10sec QT interval : 0.40-0.43sec ST interval :0.32 - sec
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HOW TO READ THE ECG
Rhythm analysis
Analyzing individual wave & segments
Determine the mean electrical axis
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RHYTHM ANALYSIS
• Step 1: Determine regularity.• Step 2: Calculate rate. • Step 3: Assess the P waves.• Step 4: Determine PR interval.• Step 5: Determine QRS duration.
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1-DETERMINE REGULARITY
Look at the R-R distances (using a caliper or markings with a pen on paper).
Regular (are they equidistant apart)? Occasionally irregular? Regularly irregular? Irregularly irregular?
Interpretation? Regular
R R
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2-CALCULATING HEART RATE
H.R = 1500 NO OF SMALL SQURES BETWEEN R-R
WAVES
OR
H.R = 300 NO OF BIG SQURES BETWEEN R-R
WAVES 11
CALCULATE RATE
Option 2 Find a R wave that lands on a bold line. Count the # of large boxes to the next R
wave. If the second R wave is 1 large box away the rate is 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75, etc. (cont)
R wave
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3-ASSESS THE P WAVES
Are there P waves? Do the P waves all look alike? Do the P waves occur at a regular rate? Is there one P wave before each QRS?Interpretation?
Normal P waves with 1 P wave for every QRS
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4-DETERMINE PR INTERVAL
Normal: 0.12 - 0.20 seconds. (3 - 5 boxes)
Interpretation? 0.12 seconds
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5-QRS DURATION
Normal: 0.04 - 0.12 seconds. (1 - 3 boxes)
Interpretation?0.08 seconds
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RHYTHM SUMMARY
Regularity regular Rate 90-95 bpm P waves normal PR interval 0.12 s QRS duration 0.08 sInterpretation?
Normal Sinus Rhythm
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Calculate Heart Rate.What is Axis ?
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Normal ECG
35 bpm• Rate?• Regularity? regular
normal
0.10 s
• P waves?
• PR interval? 0.12 s• QRS duration?
Interpretation? Sinus Bradycardia
VARIATIONS IN SINUS RHYTHM
130 bpm• Rate?• Regularity? regular
normal
0.08 s
• P waves?
• PR interval? 0.16 s• QRS duration?
Interpretation? Sinus Tachycardia
VARIATIONS IN SINUS RHYTHM
INTERPRETE THE ECG ?
SINUS ARHYTHMIASINUS ARHYTHMIAObserve Variation in Heart Rate during Inspiration and Expiration.[Increased Heart Rate during Inspiration] 20
Deviation from NSR No organized atrial depolarization, so no
normal P waves (impulses are not originating from the sinus node).
The atrial rate is usually above 350 beats per minute
Atrial activity is chaotic (resulting in an irregularly irregular rate).
Common, affects 2-4%, up to 5-10% if > 80 years old
70 bpm• Rate?• Regularity? regular
flutter waves
0.06 s
• P waves?
• PR interval? none• QRS duration?
Interpretation? Atrial Flutter
1st Degree AV Block
2nd Degree AV Block, MobitzType I
2nd Degree AV Block,MobitzType II
3rd Degree AV Block
60 bpm• Rate?• Regularity? regular
normal
0.08 s
• P waves?
• PR interval? 0.36 s• QRS duration?
Interpretation? 1st Degree AV Block
Take a look at this ECG. What do you notice
PR Interval > 0.20 sEtiology: Prolonged conduction delay in the AV node or Bundle of His.
50 bpm• Rate?
• Regularity? regularly irregular
normal, but 4th no QRS
0.08 s
• P waves?
• PR interval? lengthens
• QRS duration?
Interpretation? 2nd Degree AV Block, Type I
Take a look at this ECG. What do you notice
– PR interval progressively lengthens, then the impulse is completely blocked (P wave not followed by QRS).
• Etiology: Each successive atrial impulse encounters a longer and longer delay in the AV node until one impulse (usually the 3rd or 4th) fails to make it through the AV node.
40 bpm• Rate?
• Regularity? regular
normal, 2 & 3 no QRS
0.08 s
• P waves?
• PR interval? 0.14 s
• QRS duration?
Interpretation? 2nd Degree AV Block, Type II
Take a look at this ECG. What do you notice
Occasional P waves are completely blocked (P wave not followed by QRS).
Etiology: Conduction is all or nothing (no prolongation of PR interval); typically block occurs in the Bundle of His.
40 bpm• Rate?
• Regularity? regular
no relation to QRS
wide (> 0.12 s)
• P waves?
• PR interval? none
• QRS duration?
Interpretation? 3rd Degree AV Block
Take a look at this ECG. What do you notice
Etiology: There is complete block of conduction in the AV junction, so the atria and ventricles form impulses independently of each other. Without impulses from the atria, the ventricles own intrinsic pacemaker kicks in at around 30 - 45 beats/minute.
When an impulse originates in a ventricle, conduction through the ventricles will be inefficient and the QRS will be wide and bizarre.
Determination of Mean Electrical Axis
Axis refers to the mean QRS axis (or vector) during ventricular depolarization. As you recall when the ventricles depolarize (in a normal heart) the direction of current flows leftward and downward because most of the ventricular mass is in the left ventricle. We like to know the QRS axis because an abnormal axis can suggest disease such as pulmonary hypertension from a pulmonary embolism.
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When a vector is exactly horizontal and directed toward the person’s left side,the vector is said to extend in the direction of 0 degrees
From this zero reference point, the scale of
vectors rotates clockwise:
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FORMATION OF HEXAAXIAL SYSTEM
I
III II
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aVR aVL
aVF
FORMATION OF HEXAAXIAL SYSTEM
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-90 -120 -60 aVR aVL -150 -30
180 0 I +150 +30 III+120 +60 II +90
aVF
FORMATION OF HEXAAXIAL SYSTEM
33
Determination of Mean Electrical Axis
The QRS axis is determined by overlying a circle, in the frontal plane. By convention, the degrees of the circle are as shown.
The normal QRS axis lies between -30o and +110o.
0o
30o
-30o
60o
-60o-90o
-120o
90o 120o
150o
180o
-150o
A QRS axis that falls between -30o and -90o is abnormal and called left axis deviation.
A QRS axis that falls between +110o and +180o is abnormal and called right axis deviation.
A QRS axis that falls between +180o and -90o is abnormal and called Indeterminant (extende rt axis ) .
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HOW TO CALCULATE THE QRS AXIS
Leads & there isoelectric partners
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… if the QRS is negative in lead I and negative in lead II what is the QRS axis? (normal, left, right or right superior axis deviation)
QRS Complexes
Axis I aVF
+ +
+ -
- +
- -
normal
left axis deviation
right axis deviation
right superior axis deviation/ indeterminant
How to calculate the QRS axis
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