Week 1/2 - A(1) - Yr 4 ECG Module (Section 1 and 2) - How to do it, Analysing the ECG( rate/rhythym/axis/waves/interval/segment

Question 1

SECTION 1 - HOW TO DO AN ECG What angle should a patient be lying at when performing an ECG? Any pillows?

Answer 1

Patient should be lying at 30-40 degrees with one or two pillows supporting the neck

Question 2

If the patient is lying in any other position than the 30-40 degrees eg sitting on a chair or lying flat, what should you do?

Answer 2

If the patient is lying in any other position this should be documented in the patients notes

Question 3

How should the patients identity be confirmed?

Answer 3

The patients identity should be confirmed by asking the patient to confirm their identity and verifying it against their wristband Their correct patient details should then be entered into the ECG machine

Question 4

How should the patient’s skin be prepared for an ECG?

Answer 4

The skin should be rubbed gently with dry gauze to remove loose dry skin If necessary the chest should be shaved or cleaned to improve electrode contact

Question 5

Should the electrodes be placed over bone or muscle?

Answer 5

The electrodes on the ECG should be placed over bone and not muscle to limit interference

Question 6

Where on the limbs should limb electrodes be placed? Which colours go where?

Answer 6

Limb electrodes should be placed ideally on the wrists and ankles * Traffic light- red–>yellow–>green–>black * RA - right arm (red lead) * LA - left arm (yellow lead) * LL - left leg (green lead) * RL - right leg (black lead)

Question 7

Where should the chest electrodes be placed?

Answer 7

V1 - 4th IC space, right sternal edge V2 - 4th IC space, left sternal edge V3 - between V3 and V4 V4 - 5th IC space, right mid clavicular line (where the apex beat of the heart is normally found) V5 - same level as V4, anterior axillary line V6 - same level as V4&5, mid axillary line

Question 8

How should the ECG chest electrodes be placed on a female?

Answer 8

The bra on the female should be removed and the electrodes should be placed under the breast fold in the appropriate positioning

Question 9

Common tracing problems are usually due to poor electrode contact Three common tracing problems are: * AC interference * Muscle tremor * Baseline wander Describe what AC interference looks like on the ECG?

Answer 9

AC interference is displayed as a thick baseline on the ECG waveform - due to electrical interference from other equipment in the room

Question 10

Common tracing problems are usually due to poor electrode contact Three common tracing problems are: * AC interference * Muscle tremor * Baseline wander Describe what muscle tremor looks like on the ECG?

Answer 10

A patient with a muscle tremor (ie shivering) will cause ECG waveform to look fuzzy

Question 11

Common tracing problems are usually due to poor electrode contact Three common tracing problems are: * AC interference * Muscle tremor * Baseline wander Describe what baseline wander looks like on the ECG?

Answer 11

A wandering baseline is where the ECG waveform baseline is not level and instead moves like a wave Can be due to poor electrode attachment

Question 12

What should the speed and gain be set to for a standard ECG?

Answer 12

Speed should be set to 25mm/s Gain should be set to 10mm/mV

Question 13

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Answer 13

V1 - 4th IC space, right sternal edge

Question 14

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Answer 14

Ask the patient to confirm their name and date of birth and verify this by reviewing the wrist band

Question 15

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Answer 15

Lying at 30 degrees (30-40 degrees) If patient is in any other position this must be documented

Question 16

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Answer 16

Common tracing problems are due to poor electrode attachment (looks like muscle tremor here) An abrasive pad could be used here to improve contact

Question 17

SECTION 2 - APPROACH TO ANALYSING THE 12 LEAD ECG It is important to have a step wise approach to analyzing a 12 lead ECG - ensures subtle features are not missed What is the step wise approach to analyzing the ECG? One section can be further split - next flashcard

Answer 17

* Rate * Rhythm - specific way to analyse the rhythm * Axis * P wave * PR interval * QRS complex * ST segment * T wave

Question 18

What are the 6 key questions to ask yourself when analyzing the patients rhythm?

Answer 18

Rhythm Is there any electrical activity? Are there any p-waves present? What is the QRS rate? Is the QRS regular/irregular? Is the QRS narrow/broad? What is the relationship between p-waves and QRS complexes?

Question 19

STATE AGAIN What is the stepwise approach to analysing the ECG? What are the 6 questions to ask yourself to determine the rhythm?

Answer 19

* Rate * Rhythm * Is there any electrical activity? * Are there p-waves present? * What is the QRS rate? * Are the QRS complexes regular / irregular? * Are the QRS complexes broad/narrow? * What is the relationship between p-waves and QRS complexes? Axis, P-waves, PR interval, QRS complex, ST segment, T-waves

Question 20

How do you calculate the heart rate if the rhythm is regular?

Answer 20

Calculate the number of large boxes between 2 R waves and divide into 300 Regular tachycardia - Calculate the number of small boxes between 2 R waves and divide into 1500

Question 21

STATE AGAIN HOW YOU CALCULATE A REGULAR RHYTHM HEART RATE How do you calculate the heart rate if the rhythm is irregular?

Answer 21

Regular * Calculate the number of large boxes between 2 R waves and divide into 300 * If a tachycardia, calculate the number of small boxes between 2 R waves and divide into 1500 Irregular * Calculate the number of QRS complexes in 6 seconds - 30 large boxes - and multiply by 10 SNEAKY WAY for either - ECG trace is usually for 10 seconds, count the number of QRS complexes and multiply by 6

Question 22

STATE AGAIN the speed and gain in a normal ECG? How second does a large box on the ECG equal? How many seconds does a small box on the ECG equal?

Answer 22

Speed = 25mm/s Gain = 10mm/mV One large box on the ECG = 0.2 seconds,takes 5 large boxes to equal one second One small box on the ECG = 0.04 seconds, takes 5 small boxes to equal one large box

Question 23

We have discussed rate and rhythm , now lets discuss axis What is the cardiac axis?

Answer 23

Cardiac axis is an expression of the direction of sum electrical activation in the heart The cardiac axis gives us an idea of the overall direction of electrical activity.

Question 24

To determine the cardiac axis you need to look at leads 1 to III on ECG paper A simpler way that we will discuss later is to think of lead I as your left and aVF as the right Bipolar leads record the difference in voltage between two extremities What are these bipolar leads and what are the extremities?

Answer 24

The bipolar leads that record the difference in voltage between two extremities are leads I, II and III Lead I measures difference in voltage between RA and LA Lead 2 measures difference in voltage between RA and LL Lead 3 measures difference in voltage between LA and LL

Question 25

Limb leads include leads 1, II, III, Augmented limb leads include aVR, aVL, aVF We have already dicussed how leads I, II and III are biploar recording the differences between two extemities What do leads aVR, aVL and aVF record? Are they unipolar or bipolar?

Answer 25

aVR, aVL and aVF are unipolar leads Lead aVR - Augmented Vector Right, positive electrode right shoulder. Lead aVL - Augmented Vector Left, positive electrode left shoulder. Lead aVF - Augmented Vector Foot, positive electrode on foot.

Question 26

Einthoven’s triangle can be redrawn so that: * Lead 1 (RA to LA), * Lead 2 (RA to LL)& * Lead 3 (LA to LL) intersect at a common point What is this common point?

Answer 26

They can be redrawn so that they have a common point of intersection, the heart

Question 27

Cardiac axis is defined as * Normal axis * Left axis deviation * Right axis deviation * Indeterminate axis Where would you expect to the axis to lie in healthy individuals? What would leads 1 and AVF look like?

Answer 27

In a healthy individual would expect the axis to be between -30 and +90 degrees You would expect a positive deflection in leads 1 and aVF FOR EASE - think of: * lead 1 = left arm * aVF = right arm

Question 28

Right axis deviation Where would you expect to the axis to lie? What would leads 1 and AVF look like? What is a common cause of right axis deviation?

Answer 28

Would expect the axis to lie between +90 and +180 Lead 1 would be negative and aVF would be positive Common cause of RAD is right ventricular hypertrophy - extra ventricular tissue means stronger electrical signal

Question 29

Left axis deviation Where would you expect to the axis to lie? What would leads 1 and AVF look like? What is a common cause of left axis deviation?

Answer 29

Would expect the axis to lie between -30 and -90 Lead 1 would be positive and aVF would be negative Left axis deviation is usually caused by conduction abnormalities. - eg WPW, LBBB

Question 30

What is indeterminate axis deviation also known as? What angle would you expect the axis to lie between? What would leads 1 and AVF look like? What may cause it?

Answer 30

Indeterminate axis deviation aka extreme right axis deviation or no man’s land or northwest The axis lies between -180and -90 degrees Leads 1 and aVF would both be negative Misplacement of limb leads is the most common cause (reversal of RA and LL)

Question 31

Which ECG lead is used as the rythym strip and what direction does it see the heart from?

Answer 31

Lead II is used as the ECG rythym strip, it sees the heart from an inferior direction (at 60 degrees on the cardiac axis) Lead II = RA(-ve) to LL(+ve)

Question 32

We have discussed rate, rhythm and axis Let’s now discuss the ECG timings - Pwave, PR interval, QRS complex, QT interval, ST segment, Twave ( in relation to the rythym strip) What does the P-wave represent and how long does it last?

Answer 32

The P-wave represents atrial depolarisation which spreads inferiorly and to the left from the sinoatrial node The p-wave lasts 0.08 to 0.1 seconds (2 to 3 small boxes)

Question 33

What is the first initial deflection termed after a Pwave termed if it is: * Downwards? * Upwards?

Answer 33

First initial deflection after a p-wave if downward is termed a Qwave First upward deflection after the p-wave is termed an R wave whether it is preceded by a Q wave or not

Question 34

What is the first downward deflection after an R-wave known as?

Answer 34

The first downward deflection after the R-wave is termed an S wave

Question 35

What does the QRS complex represent? What does, the Q,R and S waves of the complex represent?

Answer 35

QRS complex represents ventricular depolarisation Q wave -L->R depolarisation of interventricular septum away from recording electrode R wave - depolarisation of the main ventricular mass towards the recording electrode S wave -depolarisation of the ventricles at the base of the heart away from the recording electrode

Question 36

How long does the QRS complex last? What does a narrow or broad QRS complex make you think?

Answer 36

QRS complex is normally * A narrow QRS complex makes you think of a rhythm that originates above the AV node whether conducted through it or not * A broad QRS complex makes you think of a rhythm that originate in the ventricle

Question 37

How does the progression of R waves through the chest leads work? When should the progression from S>R to R>S occur?

Answer 37

R wave amplitude should increase from V1 to V6 The transition from S > R wave to R > S wave should occur in V3 or V4.

Question 38

What does a T-wave represent and how long should it last?

Answer 38

A twave represents ventricular repolarisation and should have an upwards deflection on lead 2

Question 39

PR interval ST segment QT interval * What does the PR interval span and how long does it last? * What does the PR interval represent and what does it allow for?

Answer 39

* PR interval lasts from the start of the P wave to the start of the QRS complex (from the start of atrial to depolarisation to the start of ventricular depolarisation) * It lasts 0.12 to 0.2 seconds * It represents delay at the AV node and allows for ventricular filling

Question 40

What does the ST segment span? Is the deflection normally negative or positive?

Answer 40

ST segment is from the end of the QRS complex to the start of the T wave - represents ventricular contraction (systole) It is normally isoelectric - elevation or depression is diagnostically important

Question 41

What does the QT interval span from? What does it reflect? What can prolong it?

Answer 41

* QT interval is from the start of the QRS complex to the end of the T wave * It primarily reflects the time for ventricular depolarization and repolariation * Prolongation can be a cardiac syndrome or acquired eg due to drugs eg macrolides (calrithromycin, erythromycin etc)

Question 42

What is the length of the QT interval?

Answer 42

QT interval needs to be corrected for heart rate Lasts < 0.44 seconds in males & < 0.46 seconds in females

Question 43

State what each wave represents and how long they last * P-wave * QRS complex * Q-wave * R-wave * S-wave * T-wave

Answer 43

P-wave - atrial depolarisation - 0.08 to 0.1 seconds QRS complex - ventricular depolarisation - * Q wave- left to right IVS depolarisation (away) * R wave - main ventricular depolarisation (towards) * S wave - base of ventricular depolarisation (away T wave - ventricular repolarisation

Question 44

State what each interval /segment represents and how long they last * PR-interval * QT-interval * ST-segment * TP interval

Answer 44

PR interval - start of atrial to start of ventricular depolarisation- AV nodal delay - 0.12 to 0.2 seconds QT interval - depolarisation and repolarisation of the ventricles - adjusted for heart rate (0.44seconds in males, 0.46seconds in females) ST segment - end of QRS to start of twave - ventricular contraction (systole) TP interval - end of T-wave to start of P-wave - ventricular relaxation (diastole)

Question 45

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Answer 45

The axis is normal Positive deflection in lead 1 and lead aVF (axis lies between -30 and +90 degrees)

Question 46

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Answer 46

There is right axis deviation Lead 1 negative and lead aVF positive deflection Axis lies between +90 and +180 degrees (right ventricular hypertrophy is a common cause)

Question 47

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Answer 47

There is poor R-wave progression R>S should occur from V3 to V4

Question 48

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Answer 48

180ms Normal PR interval 0.12 seconds to O.2 seconds (start of atrial depolarisation to start of ventricular depolarisation) (start of pwave to start of QRS complex)

Question 49

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Answer 49

Maximum QRS duration should be 120ms (0.12 seconds)