Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Yr 3 - Skills & Extras > Understanding an ECG > Flashcards

Understanding an ECG Flashcards

(55 cards)

Start Studying
1
Q

What is the purpose of an ECG?

A

to record the electrical activity of the heart from different angles to both identify and locate pathology

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do P waves represent?

A

Atrial depolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

In healthy individuals, what precedes each QRS complex?

A

A p wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does the PR interval represent?

A

The time taken for the electrical activity to move between the atria & ventricles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where does the PR interval start and end?

A

Start - beginning of the P wave
End - beginning of the Q wave (NOT at R peak)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does the QRS complex represent?

A

Ventricular depolarisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does the ST segment represent?

A

Time between depolarisation and repolarisation of the ventricles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where does the ST segment start and end?

A

Start - end of the S wave
End - beginning of the T wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does the T wave represent?

A

Repolarisation of the ventricles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What appears after the QRS complex?

A

T wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does the RR interval represent?

A

Time between the two QRS complexes (i.e. duration of cardiac cycle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where does the RR interval begin and end?

A

Begin - peak of one R wave
End - peak of next R wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does the QT interval represent?

A

The time taken for the ventricles or depolarise and then repolarise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Where does the QT interval start and end?

A

Start - beginning of QRS complex
End - end of T wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Which part of the ECG represents atrial depolarisation?

A

P wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which part of the ECG represents ventricular depolarisation?

A

QRS complex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Which part of the ECG represents the time between depolarisation and repolarisation of the ventricles?

A

ST segment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which part of the ECG represents the time taken for the electrical activity to move between the atria and ventricles?

A

PR interval

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which part of the ECG represents the repolarisation of the ventricles?

A

T wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which part of the ECG represents the time between the two QRS complexes?

A

R-R interal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Which part of the ECG represents the time taken for the ventricles to depolarise and repolarise?

A

QT interval

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What does each small square of an ECG represent?

A

0.04 seconds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What does each large square of an ECG represent?

24
Q

how many large squares on an ECG represent 1 second?

25
How many large squares on an ECG represents 1 minute?
300
26
How does an ECG electrode differ from an ECG lead?
Electrode → A conductive pad that is attached to the skin **to record electrical activity** Lead → A **graphical representation of the heart’s electrical activity** which is calculated by analysing data from several ECG electrodes
27
How many ECG electrodes are there in a 12-lead ECG?
10 (6 chest 4 limb)
28
Describe the position of the chest electrodes
* V1 → 4th intercostal space at right sternal edge * V2 → 4th intercostal space at left sternal edge * V3 → Midway between V2 and V4 electrodes * V4 → 5th intercostal space in left midclavicular line * V5 → Left anterior axillary line at same level as V4 * V6 → Left mix-axillary line at same level as V4/V5
29
Describe the position of the 4 limb electrodes
* Red (RA) → on ulnar styloid process of right arm * Yellow (LA) → on ulnar styloid process of left arm * Green (LL) → on medial or lateral malleolus of left leg * Black (BL) → on medial or lateral malleolus of right leg
30
What 12 leads doe an ECG consist of?
* Three bipolar limb leads (I, II and III) * Three unipolar limb leads (IV/aVR, V/aVL and VI/aVF) * 6 unipolar chest leads
31
What view of the heart does each chest lead give you?
* V1 → septal * V2 → septal * V3 → anterior * V4 → anterior * V5 → lateral * V6 → lateral
32
What does a **bipolar** ECG lead mean?
A lead composed of **two** **electrodes** of opposite polarity is called bipolar lead.
33
What does a **unipolar** ECG lead mean?
A lead composed of a single positive electrode and a reference point is a unipolar lead.
34
Leads I, II and III are **bipolar.** Which 2 electrodes does each lead analyse activity between?
* Lead I → calculated by analysing activity between **RA** (right arm) and **LA** (left arm) electrodes * Lead II → calculated by analysing activity between **RA** and **LL** electrodes * Lead III → calculated by analysing activity between **LA** and **LA** electrodes
35
Which view of the heart does lead I → aVF give?
1 → lateral II → inferior III → inferior aVR → lateral aVL → lateral avF → inferior
36
What causes **positive deflection** in an ECG trace?
When the **electrical activity** within the heart travels **_towards_** a lead
37
What type of deflection do you get in an ECG trace when electrical activity travels **away from a lead**?
Negative
38
How do deflections appear on an ECG?
Waves
39
What does each deflection (i.e. wave) on the ECG represent?
the **average direction of electrical travel**
40
What does the height of each deflection/wave on an ECG represent?
The **amount** of **electrical activity flowing** in that **direction** (i.e. the **higher** the deflection, the **greater** the amount of electrical activity flowing towards the lead).
41
What is the lead with the most positive deflection aligned with?
The **direction** the heart’s **electrical activity** is **travelling** Example: * If the **R wave** is **greater** than the **S wave** it suggests depolarisation is moving **towards** that lead. * If the **S wave** is **greater** than the **R waves** it suggests depolarisation is moving **away** from that lead. * If the **R and S waves** are of **equal** size it means depolarisation is travelling at exactly **90°** to that lead.
42
What does the **cardiac axis** give us an overall idea of?
the **overall direction of electrical activity**
43
Describe a brief order of electrical activity in healthy individuals in the heart
1. The electrical activity of the heart begins at the sinoatrial (SA) node 2. Spreads to the atrioventricular (AV) node 3. Spreads down the **bundle of His** 4. Spreads to **Purkinje fibres →** causes ventricular contraction
44
Where should the cardiac axis lie between?
-30 degrees and +90 degrees
45
Towards which leads (in healthy individuals) is the **overall direction of electrical activity**?
Leads I, II and III → you will therefore see a **positive deflection** in all these leads
46
In a healthy individual, which lead will show the **most positive deflection**? Why?
Lead II → as it is the most closely aligned to the overall direction of electrical spread
47
In a healthy individual, which lead will show the **most negative deflection**? Why?
Lead IV/aVR → due to aVR looking at the heart in the opposite direction
48
Right axis deviation involves the direction of depolarisation being distorted how?
To the right (between +90 and +180 degrees)
49
How are the leads affected in right axis deviation?
Lead I becomes negative Lead aVF/III becomes more positive
50
What is the most common cause of right axis deviation?
Right ventricular hypertrophy
51
How does right ventricular hypertrophy lead to right axis deviation?
* **Extra right ventricular tissue** results in a **stronger electrical signal** being generated by the **right side of the heart** * This causes the deflection in **lead I to become negative** and deflection in **lead aVF/III to be more positive**
52
When is right axis deviation a normal finding?
In very tall individuals
53
Give one other condition that causes right axis deviation
Pulmonary hypertension as causes right ventricular hypertrophy
54
Left axis deviation results in the direction of depolarisation being distorted how?
To the left (between -30 and -90 degrees)
55
Left axis deviation results in the deflection of lead III becoming negative. When is this finding only considered significant?
If the deflection of lead II also becomes negative

Yr 3 - Skills & Extras (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions