Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ΩΩ 3b Bateman - Clinical Scans etc > Learning ECG > Flashcards

Learning ECG Flashcards

1
Q

What are each part of an ECG?

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

What is the P wave?

A

P waves represent atrial depolarisation.

In healthy individuals, there should be a P wave preceding each QRS complex.

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

What is the PR interval?

A

The PR interval begins at the start of the P wave and ends at the beginning of the Q wave.

It represents the time taken for electrical activity to move between the atria and the ventricles.

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

What is the QRS complex?

A

The QRS complex represents depolarisation of the ventricles.

It appears as three closely related waves on the ECG (the Q, R and S wave).

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

What is the ST segment?

A

The ST segment starts at the end of the S wave and ends at the beginning of the T wave.

The ST segment is an isoelectric line that represents the time between depolarisation and repolarisation of the ventricles (i.e. ventricular contraction).

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

What is the T wave?

A

The T wave represents ventricular repolarisation.

It appears as a small wave after the QRS complex.

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

What is the RR interval?

A

The RR interval begins at the peak of one R wave and ends at the peak of the next R wave.

It represents the time between two QRS complexes.

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

What is the QT interval?

A

The QT interval begins at the start of the QRS complex and finishes at the end of the T wave.

It represents the time taken for the ventricles to depolarise and then repolarise.

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

What are the characteristics of ECG paper?

A

Each small square represents 0.04 seconds

Each large square represents 0.2 seconds

5 large squares = 1 second

300 large squares = 1 minute

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

Where are ECG leads placed?

A

Chest electrodes

There are six chest electrodes:

V1: 4th intercostal space at the right sternal edge.

V2: 4th intercostal space at the left sternal edge.

V3: midway between the V2 and V4 electrodes.

V4: 5th intercostal space in the midclavicular line.

V5: left anterior axillary line at the same horizontal level as V4.

V6: left mid-axillary line at the same horizontal level as V4 and V5.

Limb electrodes

There are four limb electrodes:

Red (RA): on the ulnar styloid process of the right arm.

Yellow (LA): on the ulnar styloid process of the left arm.

Green (LL): on the medial or lateral malleolus of the left leg.

Black (RL): on the medial or lateral malleolus of the right leg.

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

What does each lead viewpoint represent on an ECG?

A

Chest leads

V1: septal view of the heart

V2: septal view of the heart

V3: anterior view of the heart

V4: anterior view of the heart

V5: lateral view of the heart

V6: lateral view of the heart

Other leads

Lead I: lateral view (calculated by analysing activity between the RA and LA electrodes)

Lead II: inferior view (calculated by analysing activity between the RA and LL electrodes)

Lead III: inferior view (calculated by analysing activity between the LA and LL electrodes)

aVR: lateral view (calculated by analysing activity between LA+LL -> RA)

aVL: lateral view (calculated by analysing activity between RA+LL -> LA)

aVF: inferior view (calculated by analysing activity between RA+LA -> LL)

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

With regards to R and S leads, what height means that the electrical activity is moving that way?

A

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.

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

Which leads are inferior, lateral, anterior and septal?

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

What leads are represented in the cardiac axis?

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

What does a normal cardiac axis look like?

A

In healthy individuals, you would expect the cardiac axis to lie between -30°and +90º.

The overall direction of electrical activity is therefore towards leads I, II and III (the yellow arrow below).

As a result, you see a positive deflection in all these leads, with lead II showing the most positive deflection as it is the most closely aligned to the overall direction of electrical spread.

You would expect to see the most negative deflection in aVR.

This is due to aVR providing a viewpoint of the heart from the opposite direction.

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

What is right axis deviation and what is the most common cause of it?

A

Right axis deviation (RAD) involves the direction of depolarisation being distorted to the right (between +90º and +180º).

The most common cause of RAD is right ventricular hypertrophy. 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 the deflection in lead aVF/III to be more positive.

RAD is commonly associated with conditions such as pulmonary hypertension, as they cause right ventricular hypertrophy. RAD can, however, be a normal finding in very tall individuals.

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

What is left axis deviation?

A

Left axis deviation (LAD) involves the direction of depolarisation being distorted to the left (between -30° and -90°).

This results in the deflection of lead III becoming negative (this is only considered significant if the deflection of lead II also becomes negative). LAD is usually caused by conduction abnormalities.

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

WHAT ARE THE DIFFERENT STEPS FOR INTERPRETENING AN ECG?

A
  1. Confirm details
  2. Heart rate + rhythm
  3. Cardiac axis
  4. P waves
  5. PR interval - 0.12 - 0.2s
  6. QRS complex - 0.12 - 0.2s
  7. QT - 0.32 - 0.42s
  8. ST segment
  9. T waves
  10. U waves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

WHAT ARE THE DIFFERENT CLASSIFICATIONS OF HEART RATE?

A

Normal: 60-100 bpm

Tachycardia: > 100 bpm

Bradycardia: <60bpm

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

How is heart rate calculated with a regular heart rhythm?

A

If a patient has a regular heart rhythm their heart rate can be calculated using the following method:

Count the number of large squares present within one R-R interval.

Divide 300 by this number to calculate heart rate.

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

How is heart rate calculated with an irregular heart rhythm?

A

If a patient’s heart rhythm is irregular the first method of heart rate calculation doesn’t work (as the R-R interval differs significantly throughout the ECG). As a result, you need to apply a different method:

  1. Count the number of complexes on the rhythm strip (each rhythm strip is typically 10 seconds long).
  2. Multiply the number of complexes by 6 (giving you the average number of complexes in 1 minute).
22
Q

WHAT CAN HEART RHYTHMS LOOK LIKE ON ECG?

How do you work out the rhythm on an ECG trace?

A

A patient’s heart rhythm can be regular or irregular.

Irregular rhythms can be either:

  1. Regularly irregular (i.e. a recurrent pattern of irregularity)
  2. Irregularly irregular (i.e. completely disorganised)

Mark out several consecutive R-R intervals on a piece of paper, then move them along the rhythm strip to check if the subsequent intervals are similar.

23
Q

What does an irregularly irregular ECG look like?

A
24
Q

WHAT IS THE CARDIAC AXIS?

What clock direction should the electrical activity spread?

Which leads do you need to look in to determine the axis?

A

Cardiac axis describes the overall direction of electrical spread within the heart.

In a healthy individual, the axis should spread from 11 o’clock to 5 o’clock.

To determine the cardiac axis you need to look at leads I, II and III.

25
Q

What does a normal cardiac axis look like?

A

Lead II has the most positive deflection compared to leads I and III.

26
Q

What does right axis deviation look like?

A

Lead III has the most positive deflection and lead I should be negative.

Right axis deviation is associated with right ventricular hypertrophy.

27
Q

What does left axis deviation look like on ECG?

A

Lead I has the most positive deflection.

Leads II and III are negative.

Left axis deviation is associated with heart conduction abnormalities.

28
Q

WHAT DO YOU LOOK FOR IN P WAVES?

A

Are P waves present?

  1. If so, is each P wave followed by a QRS complex?
  2. Do the P waves look normal? – check duration, direction and shape
  3. If P waves are absent, is there any atrial activity?

Sawtooth baseline → flutter waves

Chaotic baseline → fibrillation waves

Flat line → no atrial activity at all

29
Q

HOW LONG SHOULD THE PR INTERVAL BE?

What does a prolonged PR interval suggest?

A

The PR interval should be between 120-200 ms (3-5 small squares).

Prolonged PR interval (>0.2 seconds)

A prolonged PR interval suggests the presence of atrioventricular delay (AV block).

30
Q

What the PR interval in first degree heart block?

A

First-degree heart block involves a fixed prolonged PR interval (>200 ms).

31
Q

What is 2nd degree heart block (type 1)?

A

Second-degree AV block (type 1) is also known as Mobitz type 1 AV block or Wenckebach phenomenon.

  1. Progressive prolongation of the PR interval until eventually the atrial impulse is not conducted and the QRS complex is dropped.
32
Q

What is 2nd degree heart block (type 2)?

A

Second-degree AV block (type 2) is also known as Mobitz type 2 AV block.

  1. Typical ECG findings in Mobitz type 2 AV block include a consistent PR interval duration with intermittently dropped QRS complexes due to a failure of conduction.
  2. The intermittent dropping of the QRS complexes typically follows a repeating cycle of every 3rd (3:1 block) or 4th (4:1 block) P wave.
33
Q

What is third degree heart block?

A

Third-degree (complete) AV block occurs when there is no electrical communication between the atria and ventricles due to a complete failure of conduction.

Typical ECG findings include the presence of P waves and QRS complexes that have no association with each other, due to the atria and ventricles functioning independently.

  1. Narrow-complex escape rhythms (QRS complexes of <0.12 seconds duration) originate above the bifurcation of the bundle of His.
  2. Broad-complex escape rhythms (QRS complexes >0.12 seconds duration) originate from below the bifurcation of the bundle of His.
34
Q

What happens in the PR interval is shorter?

A

Simply, the P wave is originating from somewhere closer to the AV node so the conduction takes less time (the SA node is not in a fixed place and some people’s atria are smaller than others).

The atrial impulse is getting to the ventricle by a faster shortcut instead of conducting slowly across the atrial wall. This is an accessory pathway and can be associated with a delta wave (see below which demonstrates an ECG of a patient with Wolff Parkinson White syndrome).

35
Q

WHAT DO YOU NEED TO LOOK FOR IN QRS COMPLEXES?

A

Width

Height

Morphology

36
Q

What can the varius widths of QRS complexes mean?

A

A narrow QRS complex
impulse is conducted down the bundle of His and the Purkinje fibre to the ventricles. This results in well organised synchronised ventricular depolarisation.

A broad QRS complex
Abnormal depolarisation sequence – for example, a ventricular ectopic where the impulse spreads slowly across the myocardium from the focus in the ventricle. In contrast, an atrial ectopic would result in a narrow QRS complex because it would conduct down the normal conduction system of the heart. Similarly, a bundle branch block results in a broad QRS complex because the impulse gets to one ventricle rapidly down the intrinsic conduction system then has to spread slowly across the myocardium to the other ventricle.

37
Q

What can the different heights of QRS complexes mean?

A

Small complexes

  • Are defined as < 5mm in the limb leads or < 10 mm in the chest leads.

Tall complexes

  • Imply ventricular hypertrophy
  • (although can be due to body habitus e.g. tall slim people)
38
Q

What is a delta wave?

A

The mythical ‘delta wave‘ is a sign that the ventricles are being activated earlier than normal from a point distant to the AV node.

The early activation then spreads slowly across the myocardium causing the slurred upstroke of the QRS complex.

39
Q

What are Q waves?

A

Isolated Q waves can be normal.

A pathological Q wave is > 25% the size of the R wave that follows it or > 2mm in height and > 40ms in width.

A single Q wave is not a cause for concern – look for Q waves in an entire territory (e.g. anterior/inferior) for evidence of previous myocardial infarction.

40
Q

R and S waves - to look up on geeky medics dunno if need to know?

https://geekymedics.com/how-to-read-an-ecg/

A
41
Q

WHAT IS A J WAVE/OSBORNE WAVE?

When is it seen?

A

Wave just after the QRS complex

  1. Hypothermia
42
Q

WHAT IS THE ST SEGMENT?

A

The ST segment is the part of the ECG between the end of the S wave and the start of the T wave.

In a healthy individual, it should be an isoelectric line (neither elevated nor depressed).

Abnormalities of the ST segment should be investigated to rule out pathology.

43
Q

What does ST-elevation mean?

A

ST-elevation is significant when it is greater than 1 mm (1 small square) in 2 or more contiguous limb leads or >2mm in 2 or more chest leads.

It is most commonly caused by acute full-thickness myocardial infarction.

44
Q

What is ST depression?

A

ST depression ≥ 0.5 mm in ≥ 2 contiguous leads indicates myocardial ischaemia.

45
Q

WHAT SIZE ARE TALL T WAVES?

What pathology indicates tall tented t waves?

A

> 5mm in the limb leads AND

> 10mm in the chest leads (the same criteria as ‘small’ QRS complexes)

Tall T waves can be associated with:

  1. Hyperkalaemia (“tall tented T waves”)
  2. Hyperacute STEMI
46
Q

What leads is T wave inversion normal?

A

T waves are normally inverted in V1 and inversion in lead III is a normal variant.

47
Q

What is t wave inversion indicate?

A
  1. Ischaemia
  2. Bundle branch blocks (V4-6 in LBBB and V1-V3 in RBBB)
  3. Pulmonary embolism
  4. Left ventricular hypertrophy (in the lateral leads)
  5. Hypertrophic cardiomyopathy (widespread)
  6. General illness
48
Q

What are biphasic t waves indicitive of?

A

Biphasic T waves have two peaks and can be indicative of ischaemia and hypokalaemia.

49
Q

What do flattened t waves indicate?

A

Flattened T waves are a non-specific sign, that may represent ischaemia or electrolyte imbalance.

50
Q

WHAT IS A U WAVE?

A

U waves are not a common finding.

The U wave is a > 0.5mm deflection after the T wave best seen in V2 or V3.

51
Q

What is the cause of a U wave?

A
  1. Electrolyteimbalances
  2. Hypothermia
  3. Secondary to antiarrhythmic therapy (such as digoxin, procainamide or amiodarone)

ΩΩ 3b Bateman - Clinical Scans etc (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions