3.3 ECG

ElectrocardiogramElectrocardiogram

ECG/EKG ECG/EKG

Dr. PANKAJDr. PANKAJ

Electrocardiogram Electrocardiogram

When impulses passes through heart then When impulses passes through heart then electrical current also spreads to the electrical current also spreads to the surrounding tissues and to surface of body. surrounding tissues and to surface of body. When electrodes are placed on the surface When electrodes are placed on the surface then it can record the electrical activity . then it can record the electrical activity . This is known as This is known as ECG.ECG.

ECG paperECG paper-ECG paper: contains small and large squares.-ECG paper: contains small and large squares.-Each small square is 1 mm and large square is 5mm-Each small square is 1 mm and large square is 5mm-Time is measured along horizontal line and each -Time is measured along horizontal line and each

small square is 0.04 sec and each large square is small square is 0.04 sec and each large square is 0.2 sec.0.2 sec.

-Voltage is measured along vertical line and 10 mm -Voltage is measured along vertical line and 10 mm is equal to 1 mVis equal to 1 mV

-ECG paper moves at 25 mm/s speed, i.e. 1500 -ECG paper moves at 25 mm/s speed, i.e. 1500 squares/minsquares/min

ECG leadsECG leads

3 types of leads:3 types of leads:

Horizontal plane leads:Horizontal plane leads:

1.Chest leads/precordial leads: V1, V2, V3, 1.Chest leads/precordial leads: V1, V2, V3, V4,V5,V6V4,V5,V6

Frontal plane leads:Frontal plane leads:

2.Bipolar leads/standard/Einthoven’s 2.Bipolar leads/standard/Einthoven’s leads: I,II,IIIleads: I,II,III

3.Augmented unipolar leads: aVR, aVL, 3.Augmented unipolar leads: aVR, aVL, aVFaVF

Placement of leadsPlacement of leadsAugmented leads:Augmented leads:

aVR: right armaVR: right arm

aVL: left armaVL: left arm

aVF: left footaVF: left foot

Chest leadsChest leads

V1: in 4V1: in 4thth ICS at right sternal border ICS at right sternal border

V2: in 4V2: in 4thth ICS at lft sternal border ICS at lft sternal border

V3: midway between V2 and V3V3: midway between V2 and V3

V4: 5V4: 5thth ICS in lft MCL ICS in lft MCL

V5: anterior axillary line in 5V5: anterior axillary line in 5thth ICS ICS

V6: mid axillary line in 5V6: mid axillary line in 5thth ICs ICs

12 leaded ECG/EKG12 leaded ECG/EKG

Chest leadsChest leads

Einthoven’s triangleEinthoven’s triangle

Einthoven’s triangleEinthoven’s triangle

Hexaxial reference systemHexaxial reference system

Intrinsic Conduction SystemIntrinsic Conduction System

FunctionFunction: initiate & distribute impulses so heart : initiate & distribute impulses so heart depolarizes & contracts in orderly manner from depolarizes & contracts in orderly manner from

atria to ventricles.atria to ventricles.

SA node

AV node

Bundle of His

Bundle Branches

Purkinje fibers

Intrinsic Conduction SystemIntrinsic Conduction System

FunctionFunction: initiate & distribute impulses so heart : initiate & distribute impulses so heart depolarizes & contracts in orderly manner from depolarizes & contracts in orderly manner from

atria to ventricles.atria to ventricles.

SA node

AV node

Bundle of His

Bundle Branches

Purkinje fibers

Intrinsic Cardiac Conduction Intrinsic Cardiac Conduction SystemSystem

Approximately 1% of cardiac muscle cells are autorhythmic rather than contractile

75/min

40-60/min

30/min

ECG Deflection WavesECG Deflection Waves

(Pacemaker) Atrial repolarization

ECG Deflection WavesECG Deflection Waves

(Pacemaker) Atrial repolarization

ECG Deflection Wave ECG Deflection Wave IrregularitiesIrregularities

Enlarged QRS =

Hypertrophy of ventricles


Prolonged QT Interval =

Repolarization abnormalities increase chances of ventricular arrhythmias.


Elevated T wave :

Hyperkalemia


Flat T wave :

Hypokalemia or ischemia


Elevated T wave :

Hyperkalemia

Heart BlocksHeart Blocks

Normal ECG

3rd Degree Block

No P waves. Rate determined by autorhythmic cells in ventricles

2nd Degree BlockNot a QRS for each P wave

P

QRS

T

Cardiac CycleCardiac Cycle All events associated with a single heart All events associated with a single heart

beat including atrial systole & diastole beat including atrial systole & diastole followed by ventricular systole & diastole.followed by ventricular systole & diastole.

(V. Systole) (V. Diastole)

Systolic BP

Diastolic BP

ECG Deflection WavesECG Deflection Waves60 seconds ÷ 0.8 seconds = resting heart rate of 75 beats/minute

Frank Starling Law of the Frank Starling Law of the HeartHeart

The more cardiac muscle is stretched The more cardiac muscle is stretched within physiological limits, the more within physiological limits, the more forcibly it will contract.forcibly it will contract.

Rubber band analogyRubber band analogy Increasing volumes of blood in ventricles Increasing volumes of blood in ventricles

increase the stretch & thus the force increase the stretch & thus the force generated by ventricular wall generated by ventricular wall contraction.contraction.

Greater stretch means more blood Greater stretch means more blood volume is pumped out, up to physical volume is pumped out, up to physical limits.limits.


The more cardiac muscle is stretched The more cardiac muscle is stretched within physiological limits, the more within physiological limits, the more forcibly it will contract.forcibly it will contract.

Rubber band analogyRubber band analogy Increasing volumes of blood in ventricles Increasing volumes of blood in ventricles

increase the stretch & thus the force increase the stretch & thus the force generated by ventricular wall generated by ventricular wall contraction.contraction.

Greater stretch means more blood Greater stretch means more blood volume is pumped out, up to physical volume is pumped out, up to physical limits.limits.


Increased blood volume = increased stretch of myocardium

=

Increased force to pump blood out.

ECG waves & genesisECG waves & genesisP wave: normally upright , signifies atrial depolarisationP wave: normally upright , signifies atrial depolarisation <2.5mm height and 0.11 sec duration<2.5mm height and 0.11 sec duration

QRS complex: ventricular depolarisation N: 0.08 – 0.12 secQRS complex: ventricular depolarisation N: 0.08 – 0.12 sec T wave: ventricular repolarisationT wave: ventricular repolarisation

U wave: it is positive deflection which comes after T wave. Is U wave: it is positive deflection which comes after T wave. Is due to slow repolarization of interventricular purkinje fiber. due to slow repolarization of interventricular purkinje fiber. Often it is not evident in ECGOften it is not evident in ECG

R-R interval: distance between two successive R waveR-R interval: distance between two successive R wave

P-R interval : time taken for impulse to travel from SA node to P-R interval : time taken for impulse to travel from SA node to ventriclesventricles

0.12-0.22sec0.12-0.22sec

QT interval: total time for ventricular depolarisation and QT interval: total time for ventricular depolarisation and repolarisationrepolarisation

<0.42 sec<0.42 sec

AxisAxisNormal axis lies between -30 and +110 Normal axis lies between -30 and +110

degreedegree

Left axis deviation: -30 and -90 degreeLeft axis deviation: -30 and -90 degree

Right axis deviation: +110 and +/- 180 Right axis deviation: +110 and +/- 180 degreedegree

Intermediate axis : -90 and +/- 180 Intermediate axis : -90 and +/- 180 degreedegree

Electrical axis of heartElectrical axis of heart

Technique of reading and reporting Technique of reading and reporting ECGECG

1.Heart rate1.Heart rate2.Rhythm2.Rhythm3.Voltage3.Voltage4.Axis4.Axis5.P wave5.P wave6.PR interval6.PR interval7.QRS complex7.QRS complex8.ST segment8.ST segment9.T wave9.T wave10.U wave10.U wave11.QT duration11.QT duration12.Final diagnosis12.Final diagnosis

Standardisation Standardisation

Determination of axisDetermination of axis

Many methods are Many methods are therethere

Measure the overal Measure the overal height in leads I height in leads I and aVF and then and aVF and then plot in graph plot in graph paper. Then find paper. Then find the vector angle.the vector angle.

Heart rateHeart rate

HR= 1500/ RR interval in small HR= 1500/ RR interval in small squaressquares

Uses of ECGUses of ECG

1.1. Aids diagnosis, prognosis and Aids diagnosis, prognosis and treatmenttreatment

2.2. Gives information regarding Gives information regarding functioning of atria and ventriclesfunctioning of atria and ventricles

3.3. Identify damage to heart (infarction)Identify damage to heart (infarction)

4.4. Identify abnormal rhythm and rateIdentify abnormal rhythm and rate

5.5. Identify change in size of chambers Identify change in size of chambers of heartof heart

Some Abnormalities in Some Abnormalities in ECGECG

P wave:P wave: a) p wave wide and notched (p-mitral)-left atrial hypertrophya) p wave wide and notched (p-mitral)-left atrial hypertrophy b) p wave tall and peaked ( p-pulmonale) –right atrial b) p wave tall and peaked ( p-pulmonale) –right atrial

hypertrophyhypertrophy

QRS complex:QRS complex:Tall QRS- ventricular hypertrophyTall QRS- ventricular hypertrophyTall peaked T wave- hyperkalemiaTall peaked T wave- hyperkalemiaLow or inverted T wave- myocardial ischemiaLow or inverted T wave- myocardial ischemia

U wave:U wave:Prominent U wave- hypokalemiaProminent U wave- hypokalemia

ST segment:ST segment:Elevated with convexity upward-myocardial infactionElevated with convexity upward-myocardial infactionDepressed- angina pectorisDepressed- angina pectoris

PR interval:PR interval:

Increased PR interval -BradycardiaIncreased PR interval -Bradycardia

Decreased PR interval- tachycardiaDecreased PR interval- tachycardia

No PR interval- complete heart blockNo PR interval- complete heart block

Normal sinus rhythmNormal sinus rhythm

RVHRVH

Coronary infarctionCoronary infarction

Sinus tachycardiaSinus tachycardia

Ventricular tachycardia Ventricular tachycardia following extrasystolefollowing extrasystole

Ventricular fibrillationVentricular fibrillation

ECGs (lead II) showing abnormal rhythms A:Respiratory sinus

arrhythmia. B:Sinus arrest with

vagal escape. C:Atrial fibrillation. D:Premature

ventricular complex.

E:Complete atrioventricular block.

Wolf parkinson white ( WPW ) Wolf parkinson white ( WPW ) syndrome:syndrome:

Extra path is formed between atrium and Extra path is formed between atrium and ventricleventricle

Features:Features:

1.1. Short PR intervalShort PR interval

2.2. Wide QRS complexWide QRS complex

3.3. Delta waveDelta wave

Heart block:Heart block:1.First degree heart block: prolonged PR interval1.First degree heart block: prolonged PR interval

2.Second degree heart block2.Second degree heart block

a. Mobitz type I b. mobitz type IIa. Mobitz type I b. mobitz type II

3.Complete heart block3.Complete heart block

3.3 ECG

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