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ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills
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ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

Dec 22, 2015

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Page 1: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Cardiff and Vale ECG Department

Electrocardiogram (ECG)

Clinical Skills

Page 2: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Aims & Outcomes

The aim of this module is to produce a technically accurate, artefact free 12 lead ECG in accordance with AHA/ SCST guidelines. To be able to recognise the basic components of the ECG.

Learning OutcomesAt the end of the session the student should be able to:

Recognise the anatomy of the conduction system of the heart.Identify the waveforms of the cardiac cycle, as seen on the ECG.Calculate the heart rate from the ECG.Outline the equipment and specifications required for recording a 12 lead ECG.State and demonstrate the anatomical positions for electrode placement.Recognise and minimise interference patterns on an ECG.Identify Einthoven’s Triangle, and its uses in practical electrocardiography.Produce a technically accurate ECG.

Aims & Outcomes

Page 3: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

An ECG is a transthoracic interpretation of the electrical

activity of the heart.

A typical ECG tracing of the cardiac cycle (heartbeat)

consists of a P wave, QRS complex, T wave and sometimes

a U wave.

William Einthoven chose the letters P,Q,R, S, T to identify

the tracing.

What is an ECG?

WHAT IS AN ECG?

Page 4: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Conduction System

The heart is influenced by the autonomic nervous system which can increase or decrease the heart rate in line with the requirements of the body.

However, due to an intrinsic regulating system, called the conduction system it is possible for the heart to go on beating without any direct stimulus from the nervous system. This system is composed of specialised muscle tissue that generates and distributes the conduction that causes contraction of the cardiac muscle. These tissues are found in the sinus (or sinoatrial) node, atrioventricular node, bundle of His, bundle branches, and conduction myofibres.

When stimulated by electrical activity, muscle fibres contract and produce motion. In the heart, this electrical activity is referred to as depolarisation. The contraction causes the blood to be pumped around the body.

Relaxation of the heart muscle is caused by electrical repolarisation.

Conduction System

Page 5: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECGConduction System

DEPOLARISATION

REPOLARISATION

Page 6: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Principle of how the ‘ECG’ works

In this example we are recording the potential difference between two points. As depolarisations (positive charge entering the cell from outside) move across the cell, the voltage difference increases. A movement of positive charges into a cell is recorded as a positive deflection and a movement of positive charges out of the cell is recorded as a negative deflection.

Principles of how the ‘ECG’ works

Page 7: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Principle of how the ‘ECG’ works

Principles of how the ‘ECG’ works

To understand the morphology of the ECG waveforms one needs to appreciate only one biophysical fact: if a wave front of depolarisation travels towards the electrode attached to the + input terminal of the ECG amplifier and away from the electrode attached to the – terminal, a positive-going deflection will result. If the waveform travels away from the + electrode towards the – electrode, a negative-going deflection will be seen.

If the waveform is travelling in a direction perpendicular to the line joining the sites where the two electrodes are placed, no deflection or a biphasic deflection will be produced.

Page 8: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Views of Depolarisation

It can then be seen that the voltage recorded along a particular lead axis (the vector joining the - to the + electrode) at a particular time is obtained by taking a projection onto that axis of the vector representing the magnitude and direction of depolarization at that time. Thus, when the lead axis in the figure alongside points from left to right, parallel to the direction of movement of depolarization, a positive-going complex results. When the two directions are anti-parallel, a negative-going complex is produced.

Views of Depolarisation

Page 9: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Atrial Depolarisation

The electrical activity of the heart originates in the sino-atrial node. The impulse then rapidly spreads through the right atrium to the atrioventricular node. It also spreads through the atrial muscle directly from the right atrium to the left atrium. The P-wave is generated by activation of the muscle of both atria.

Atrial Depolarisation

Page 10: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Septum Repolarisation

The impulse travels very slowly through the AV node, then very quickly through the bundle of His, then the bundle branches, the Purkinje network, and finally the ventricular muscle.

The first area of the ventricular muscle to be activated is the interventricular septum, which activates from left to right. This generates the Q-wave.

Septum Repolarisation

Page 11: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Ventricular Depolarisation

Next, the left and right ventricular free walls, which form the bulk of the muscle of both ventricles, gets activated by an action potential from the bundles of His and begin to cause depolarisation from the septum towards the apex (bottom) of the ventricles.

This generates the R-wave on the ECG.

Ventricular Depolarisation

Page 12: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Late Ventricular Depolarisation

A few small areas of the ventricles are activated at a rather late stage. This generates the S-wave

Late Ventricular Depolarisation

Page 13: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Ventricular Repolarisation

Finally, the ventricular muscle repolarises. This generates the T-wave

Ventricular Repolarisation

Page 14: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Not All Cardiac Actions Potentials Are The Same!!

Action potentials at the bottom edge of the ventricle are SHORTER than at the top. This helps to explain why the repolarisation of the ventricles (the T wave) gives a positive deflection on the ECG trace.

You can see that the action potentials at the bottom of the ventricle repolarise before those at the top.

Therefore the wave of repolarisation moves in the opposite direction to the wave of depolarisation.

Cardiac Action Potentials

Page 15: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

The ECG

The ECG

P

QRS

T

U

Atrial Depolarisation

Ventricular Depolarisation

Ventricular Repolarisation

Though to be Septal Repolarisation

Page 16: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

The P Wave

The P Wave

P Atrial Depolarisation

Represents atrial depolarisation Small, rounded wave

Page 17: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

The QRS Wave

The QRS Wave

Represents ventricular depolarisation Large, “pointed” wave

Q Wave:The first negative deflection.

R Wave:Any positive deflection.

S Wave:Any negative deflection after an R wave.

QRS Ventricular Depolarisation

Page 18: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

The T Wave

The T Wave

T Ventricular Repolarisation

Large, rounded wave Represents ventricular repolarisation

Page 19: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

• Measured from the beginning of the P wave to the beginning of the QRS complex

• Normal value: 0.12 – 0.2 secs3 – 5 small squares

PR Interval

Page 20: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

QRS Duration

• Measured from initial deflection of the QRS from the isoelectric line to the end of the QRS complex

• Normal value: < 0.12 secs

less than 3 small squares

Page 21: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Sinus Rhythm

Quick Check: Sinus Rhythm

Rate Rhythm

Ventricular 60 - 100 Regular

Atrial Same as ventricular Regular

P-R Interval Normal

QRS Complex Normal

Page 22: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

ATRIO-VENTRICULAR BLOCKS

Page 23: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

1st Degree Heart Block

Measured from the beginning of the P wave to the beginning of the QRS complex

Normal value: 0.12 – 0.2 secs3 – 5 small squares

Atrio-Ventricular Heart Block

PR Interval

> 5 small squares

Page 24: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

1st Degree Heart Block

Prolonged PR interval: >0.2 secs Constant PR interval Regular ventricular rhythm

Atrio-Ventricular Heart Block

Page 25: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

2nd Degree Heart Block

Atrio-Ventricular Heart Block

Mobitz Type 1 Wenckebach

Mobitz Type 2 ConstantPeriodic

Page 26: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

2nd Degree Heart Block – Mobitz Type 1 - Wenckebach

Progressive Lengthening of PR interval, until a non-conducted P wave occurs. Usually occurs in a cyclic pattern

Atrio-Ventricular Heart Block

Page 27: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

2nd Degree Heart Block – Mobitz Type 1 - Wenckebach

Atrio-Ventricular Heart Block

Page 28: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

2nd Degree Heart Block – Mobitz Type 2 – Constant Block

P wave not followed by a QRS plus P wave normally conducted. (May be 2:1, 3:1, etc) PR interval of the conducted beat is constant. (May be normal or prolonged) Atrial rate is regular and normal. Ventricular rate may be regular (eg. 2:1)

Atrio-Ventricular Heart Block

Page 29: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

2nd Degree Heart Block – Mobitz Type 2 – Constant Block

Atrio-Ventricular Heart Block

Page 30: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

2nd Degree Heart Block – Mobitz Type 2 – Periodic Block

Normal 1 P:1 QRS conduction with occasional non-conducted P waves.

PR interval of the conducted beat is regular. (May be normal or prolonged)

Atrio-Ventricular Heart Block

Page 31: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

2nd Degree Heart Block – Mobitz Type 2 – Periodic Block

Atrio-Ventricular Heart Block

Page 32: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

3rd Degree Heart Block – Complete Heart Block

Regular P waves at a normal rate Regular QRS complexes at a slow rate. (30 – 40 beats / min) No correlation between P waves and QRS complexes QRS may have abnormal shape

Atrio-Ventricular Heart Block

Page 33: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

MYOCARDIAL ISCHAEMIA & INFARCTION

Page 34: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

What is an MI?

…is when part of the HEART muscle dies because it has been starved of OXYGEN

Myocardial Ischaemia & Infarction

Myocardial Infarction

Heart Attack

Coronary Thrombosis

Page 35: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Coronary Arteries

There are 3 Coronary Arteries:

1.LAD (Left main coronary artery)

2.Circumflex artery (originates off the LAD)

3.Right coronary artery

All these sub-divide into smaller branches

Myocardial Ischaemia & Infarction

Page 36: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Myocardial Infarction

Myocardial Ischaemia & Infarction

Myocardial Infarction as a result of a blocked left anterior descending coronary artery

Page 37: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Coronary Arteries Territory

Myocardial Ischaemia & Infarction

ARTERY ECG LEADS TERRITORY

RCA II, III & aVF Inferior

LAD V1 – V6 Anterior

Cx I, aVL, V5 & V6 Lateral

Page 38: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECGMyocardial Ischaemia & Infarction

V1 – V6

I, aVL, V

5 & V6

Page 39: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

ST Segments

Myocardial Ischaemia & Infarction

Note: “Upsloping” ST depression is not an ischaemic abnormality

Page 40: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

ST Segments

Myocardial Ischaemia & Infarction

Page 41: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Evolution of Acute MI

A. Normal ECG prior to MI

B. Hyperacute T wave change increased T wave amplitude and width may also see ST elevation

C. Marked ST elevation with hyperacute T wave changes (transmural injury)

D. Pathologic Q waves, less ST elevation, terminal T wave inversion (necrosis)

E. Pathologic Q waves, T wave inversion (necrosis and fibrosis)

F. Pathologic Q waves, upright T waves (fibrosis)

Myocardial Ischaemia & Infarction

Page 42: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

A 55 year old man with 4 hours of “crushing” chest pain

• Acute inferior myocardial infarction

• ST elevation in the inferior leads II, III and aVF

• Reciprocal ST depression in the anterior leads

Myocardial Ischaemia & Infarction

Page 43: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

• Acute antero-lateral infarction

• ST elevation in I, aVL, V2 – V6

• Reciprocal ST depression in inferior leads

Myocardial Ischaemia & Infarction

Page 44: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

ECG Taken @ 11:01 am

Myocardial Ischaemia & Infarction

Page 45: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

ECG Taken @ 11:12 am

Myocardial Ischaemia & Infarction

Page 46: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Narrowed Proximal LAD

Myocardial Ischaemia & Infarction

Page 47: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Interventional Procedure

Myocardial Ischaemia & Infarction

PTCAPercutaneous Transluminal Coronary Angioplasty

PCIPercutaneous Coronary Intervention

Page 48: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Evolution of Acute MI

ST elevationOften within minutes of onset of MI, but may be delayed for several hours

T Wave InversionSlightly later than ST elevation

ST elevation returns to iso-electric lineUsually within 48-72 hours

Q wavesMay take several hours to develop after onset of MI

Myocardial Ischaemia & Infarction

Page 49: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

ELECTRODE POSITIONING

Page 50: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Limb Leads

RA – Right Wrist

LA – Left Wrist

LL – Left Ankle

RL – Anywhere on Body

(Records I, II, III, aVR, aVL, aVF)

Electrode Positioning

Page 51: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Chest Leads

V1 – 4th intercostal space, right sternal border - (Always locate by using sternal angle)

V2 – 4th intercostal space, left sternal border

V4 – 5th intercostal space, left mid-clavicular line

V3 – Diagonally midway between V2 and V4

V5 – Left anterior axillary line, horizontal with V4*

V6 – Left mid axillary line, horizontal with V4 and V5*

(*Not 5th intercostal space!)

Electrode Positioning

Page 52: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Einthoven’s Triangle

Gives the first three limb leads on the ECG:I, II & III.

Utilises the RA, LA & LL, recording the potential difference between two points.

Can be used to identify origin of interference.

Electrode Positioning

Page 53: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECGElectrode Positioning

Page 54: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Recording Procedure

Identify patient and explain the procedure.

Ask patient to lie on bed/couch, if possible.

Prepare skin on electrode sites.

Attach electrodes and ECG leads.

Record Auto 12 lead.

Adjust, if necessary.

Inform patient of next step.

Label ECG and dispatch appropriately.

Recording Procedure

Page 55: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Specifications

Speed: 25mm/sec

Sensitivity: 10mm/mV

Frequency Response: 0.05 – 150Hz

Filter Off!

Measurement

Page 56: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECG

Leads

Leads

LIMB LEADS CHEST LEADS

Page 57: ECG Cardiff and Vale ECG Department Electrocardiogram (ECG) Clinical Skills.

ECGWeb Resources

www.scst.org.uk/resourceswww.bhf.org.ukwww.bcs.comwww.ems12lead.comwww.bem.fi/book/06/06www.invasivecardiology.comwww.medicine.mcgill.ca/physio/vlab/cardio/ecgbasicswww.ecglibrary.comwww.ivline.orgwww.my.clevelandclinic.orgwww.texheartsurgeons.comwww.rpw.chem.ox.ac.ukwww.nottingham.ac.ukwww.frca.co.ukwww.drmcdougall.com

Web Resources