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Cardiovascular System > ECG > Flashcards

ECG Flashcards

1
Q

What are the parts of the conducting system of the heart

A

Sinoatrial node

Atrioventricular noce

Bunde of His

Right bundle branches

Left bundle branches

Purkinje fibres

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2
Q

What are are the functions of the fibrous ring of the heart

A

Anchors the valves

Is where the heart muscles insert

Electrical insulator allowing atria to contract seperately from the ventricles

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3
Q

What does an ECG record

A

Shows electrical changes on extracellular surface of cardiac myocytes

Shows muscle depolarisation

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4
Q

Describe the types of deflection during depolarisation and repolarisation

A

Depolarisation towards +ve electrode - positive complex, upward deflection

Depolarisation away +ve electrode - negative complex, downward deflection

Repolarisation towards +ve electrode - negative complex, downward deflection

Repolarisation away +ve electrode - positive complex, upward deflection

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5
Q

What is seen on an ECG when SA node depolarises

A

Nothing as insufficient signal

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6
Q

What does the P wave represent and what causes it to be upward

A

Atrial depolarisation

Depolarisation is downward, going towards the +ve electrode

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7
Q

What is the name for when there is little or no signal on an ECG

A

isoelectric segment or flat line

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8
Q

How is the delay at the AV node and the spread of depolarisation to the bundle of His seen on an ECG

A

Both are seen as an isoelectric segment

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9
Q

What does the q wave represent, how is it seen and why is this the case

A

It represents the depolarisation of the interventricular septum

Seen as a small downward deflection as depolarisation is from left to right, moving obliquely away from +ve electrode (no deflection may be seen)

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10
Q

What does the R wave represent, how does it appear and why

A

It represents depolarisation of apex and free ventricular wall

Appears as large upward deflection due to depolarisation moving towards electrode

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11
Q

What does the S wave represent, how does it appear and why

A

Represents the depolarisation spreading upwards to the base of the ventricles

Seen as small downward deflection as the depolarisation is moving away - small as not moving directly away

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12
Q

What does the T wave represent, how does it appear and why

A

Ventricular repolarisation

Appears as medium upward deflection as the repolarisation is moving away from the +ve electrode

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13
Q

What are the 6 views seen by the limb leads and which limbs contribute to them (also are they unipolar of bipolar)

A

aVR - unipolar, right upper

aVL - unipolar, left upper

aVF - unipolar, left lower

I - bipolar, left and right upper

II - bipolar, right upper and left lower

III - bipolar, left upper and left lower

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14
Q

What are leads I and aVL looking at

A

Left side of heart

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15
Q

What are leads II, III and aVF looking at

A

Inferior surface of the heart

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16
Q

What two planes are view by the leads, and what set does which

A

Limb looks at vertical

Chest looks at horizontal

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17
Q

Group the chest leads according to where they face

A

Septal leads - V1 and V2, face right ventricle and septum

Anterior leads - V3 and V4, face apex and anterior ventricle wall

Antero-septal leads - V1 to V4

Lateral leads - V5 and V6, face left ventricle

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18
Q

Which ECG leads face which parts of the ventricles

A

Inferior surface - II, III and aVF

Right ventricle and septum - V1 and V2

Anterior surface of ventricles - V3 and V4

IVS and anterior surface of ventricles - V1 to V4

Lateral surface of ventricles - I, V5, V6 and aVL

19
Q

What does one small square represent on an ECG

A

0.04 seconds (40 ms)

20
Q

What does one large square on an ECG represent and how many are needed for 6 seconds

A

0.2 seconds (200 ms)

30 large squares = 1 minute

21
Q

How long is a normal PR interval

A

0.12-0.2 seconds (3-5 small boxes)

22
Q

How long is a normal QRS interval

A

< 0.12 seconds

< 3 small boxes

23
Q

What is the upper limit of a QT interval

A

0.44-0.45 seconds (11 boxes)

24
Q

Label Diagram

A
25
Q

Label Diagram

A
26
Q

What are the conditions for a sinus rhythm

A

Regular rhythm

Regular heart rate (60-100bpm)

Present P waves - upright in leads II and III

PR interval - 3-5 small boxes

QRS - < 3 small boxes

Every P wave followed by QRS

Every QRS preceded by P wave

27
Q

What is an atrioventricular conduction block/heart block and what are the causes

A

Delay/ failure of conduction of impulses from atrium to ventricules via AV node and Bundle of His

Caused by acute MI or degenerative changes

28
Q

How would an ECG present a bundle branch heart block and why

A

Wider QRS complex but normal PR

Because it takes longer for depolarisation to spread across ventricles so QRS wider

29
Q

Describe the types of heart block and how they appear on an ECG

A

1st degree - caused by partial block meaning impulse takes longer time to conduct, PR interval prolonged (>5 small boxes)

2nd degree, Mobitz type I - successively longer PR intervals until QRS dropped, then cycle starts again

2nd degree, Mobitz type II - PR intervals stay the same length, but QRS complex is suddenly dropped

3rd degree - complete failure of atrioventricular conduction, atria and ventricles conduct independently, QRS and P wave have no relationship

30
Q

What are the types of abnormal rhythms, where may they arise from and what deos the QRS look like

A

Supraventricular rhythms - sinus node, atrium, AV node. Normal QRS complex

Ventricular rhythms - ventricles. Wide and bizarre QRS complex (abnormal)

31
Q

What are the features of atrial fibrillation and what is a possible cause

A

Supraventricular rhythm

Rhythm arises from multiple atrial foci - causes rapid and chaotic impulses and this means there are no p waves, just a wavy baseline, atria just quiver (no contraction)

Not all impulses conducted by AV node (refractory period)

AV conducts are irregular rate so R-R intervals are irregular but QRS complex is normal - irregular pulse and irregular stroke volume

Usually occurs due to artial dilation but may have no previous pathology

32
Q

What are the features of ventricular ectopic beats

A

Ectopic focus in ventricle muscle spontaneously depolarise but impulse does not spread via His-purkinje system

Much slower depolarisation of ventricular muscles

Wide and abnormally shaped QRS complex with no P wave

33
Q

What is ventricular tachycardia

A

Run of ≥ 3 consecutive ventricular ectopics

High risk of ventricular fibrillation developing

34
Q

What is ventricular fibrillation

A

Abnormal, chaotic, fast ventricular depolarisations from numerous ectopic sites in ventricular muscle

There is no coordinated contraction so ventricles quiver meaning no cardiac output -> cardiac arrest

35
Q

What are the differences between a partial and complete narrowing of coronary artery lumen

A

Partial narrowing - sub-endocardial ischaemia as it is furthest away from coronary arteries so is most vulnerable

Complete narrowing - trans mural injury, including sub-epicardial region

36
Q

What is a STEMI and describe its features

A

ST segment Elevation Myocardial Infarction

Complete occlusion of coronary artery by thrombus

Trans mural injury of affected area

There is an ST segment elevation in leads facing the affected area - due to sub-epicardial injury

37
Q

How would an ECG of a patient look weeks later after the STEMI

A

ST and T are normal but there is a deeper Q wave and the R wave is reduced in height

38
Q

Why do the Q waves deepen in a STEMI/myocardial infarction

A

There is muscle necrosis meaning the tissue does not produce an action potential so ECG looks through infarcted area to pick up electrical activity from opposite side of the heart which is directed away from the lead, producing the deep Q wave

39
Q

What determines a pathological Q wave

A

> 1 small square wide

> 2 small squares deep

Depth more than 1/4 height of subsequent R wave

40
Q

What are the ECG changes in a sub-endocardial injury

A

ST segment depression and T wave inversion

41
Q

What changes are seen in an ECG of patient with acute unstable angina or Non STEMI and how would you tell the difference between the two

A

Either

  • T wave inversion
  • ST depression
  • T wave inversion and ST depression

Differentiated by blood test for evidence of myocyte necrosis

42
Q

How would UA and NSTEMI appear weeks after the episode

A

Normal ST and T

No Q waves

43
Q

What are the four stages in hyperkalaemia as the level of potassium increases

A
  • Tall, peaked T wave
  • Tall, peaked T wave with flattened p wave and prolonged PR
  • Tall, peaked T wave with absent p wave and widened QRS
  • Widened QRS, ST merges with T wave. Gives sine wave pattern
44
Q

What are the three stages of hypokalaemia on an ECG as the potassium concentration decreases

A
  • Low T wave
  • Low T wave, high U wave
  • Low T wave, high U wave, low ST segment

Cardiovascular System (16 decks)

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