Cardiovascular System

ANALYSIS Dr.Mohammed Sharique Ahmed Quadri

Asst. Professor PhysiologyAlmaarefa College

الرحيم الرحمن الله بسم

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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

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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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