Brainscape's Knowledge GenomeTM

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


See full index

Block 4 > L5 Physiology: clinical introduction to ECG > Flashcards

L5 Physiology: clinical introduction to ECG Flashcards

1
Q

We have 12 leads but _____ is called the rhythm strip.

A

Lead 2

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

Lead 2 gives us the best look at the ______?

A

P wave

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

Holter monitor is worn for ___ hours and it can pick up any arrythmias.

A

24 hours

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

How do you calculate heart rate using leads?

A

Use lead 2 (rhythm strip) and look at the interval between two R waves (R-R interval).

Count big boxes between the two waves: each big box = 200 millisecond, so 5 big boxes is 1 second.

Heart rate is 300/number of big boxes.

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

Tachycardia

A

Heart rate greater than 100

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

Bradycardia

A

HR less than 60

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

ECG is a surface representation of?

A

Electrical activity of the heart

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

Describe the conduction of the heart

A

Heart has its own conduction.

  1. Wave of depolarization propagates from the SA node through intermodal pathways and through Bachman’s bundle.
  2. Pauses at the AV node
  3. Propagates through Bundle of His, then the bundle branches.
  4. Bundle branches terminate in purkinje fibres.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

SA node depolarisation is controlled by?

A

Controlled by hormones and the SNS (vagus) -> if you are fit with high vagal tone the HR will be slow

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

P wave

A

Action potentials that result from the depolarization wave from the SA node as it spreads across the atria (atrial depolarisation).

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

PR segment

A
  • It then pauses for a second
  • 120-200 ms (3-5 small squares)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

QRS complex

A
  • Ventricular depolarization begins.
  • The Q wave is due to septal depolarization which actually moves from left to right, and then propagates back to form the QRS complex.
  • Biphasic because electricity moves in 2 directions.
  • LV thicker with more conduciveness so its contribution is greater.
  • <120 ms (2-3 small squares)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

ST segment

A

Once vetricular depolarization is complete, there is a pause.

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

T wave

A

Ventricular repolarization begins at the apex -> then repolarization is complete

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

QT segment

A
  • From the Q wave to the end of the T wave
  • Normally <440-450 ms
  • This allows for both ventricular depolarization and repolarization.
  • Genetic abnormalities and drug interactions that can cause a long QT interval.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What indicates normal sinus rhythm in the heart?

A

P waves before every QRS complex

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

A positive deflection is elicited by?

A

A wave of depolarization travelling towards a particular electrode on the chest surface.

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

Negative deflection is elicited by?

A

If it is moving away it will be a negative deflection, but if its perpendicular then you get a biphasic response.

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

How many leads on chest and limbs?

A

6 on chest, 3 on limbs

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

Describe this image

A

V1 is the right pre-cordial lead across to V6 in the axilla.

Normal complex will look different depending on where they are placed.

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

Chest leads look at a ______ axis, and limb leads look in a _________.

A

Horizontal axis; frontal plane.

22
Q

Limb leads are referred to as ________ because?

A

Bipolar leads; because they have an electrode attached to one limb, but the amplifier measures the difference between one limb and the other.

23
Q

Unipolar derived leads

A

Uses limb leads, so we can imagine a central point in the torso which is called wilsons central terminal.

24
Q

Wilsons central terminal

A

Imaginary central point in torso in limb leads context.

25
Q

Einthoven’s triangle

A

Allows heart to be split up into segments, and see where the conduction is.

26
Q

Cardiac axis

A

Cardiac axis is average (or net) direction of spread of depolarization estimated from the frontal (limb) leads 1, 2 and 3.

27
Q

Normal axis is usually positive in leads?

A

Leads 1, 2 and 3.

28
Q

What should occur in normal axis?

A
  • Lead 1 and aVF (augmented vector foot) should both be positive
  • Lead 2 positive because the direction of conduction is down this way
  • aVR (augmented vector right) negative because it is looking up towards the right arm, therefore conduction is away from it.
29
Q

What should occur in leftward axis?

A
  • Lead 1 positive, aVF negative
  • Common examples: left ventricular hypertrophy; left bundle branch or fascicular block delayed conduction
30
Q

What should occur in rightward axis

A
  • Lead 1 negative, aVF positive
  • Common examples: right ventricular hypertrophy; RV “strain” e.g. pulmonary embolus
31
Q

Atrial fibrillation

A
  • Irregularly irregular rhythm
  • No clear P waves
  • There is chaotic electrical activity.
  • No organized atrial depolarization from the SA node across the atria.
32
Q

Consequence of atrial fibrillation

A

Because it potentially occurs 600 times a minute (very quickly), some waves progress to the ventricles.

33
Q

If the cardiac cells are not ready to accept the atrial signal what happens?

A

Nothing will happen but at odd times, the signal does get through and we get a QRS segment.

34
Q

It can be fast or slow, but atrial fibrillation is commonly?

A

Tachy

35
Q

Heart block causes what?

A

Delay in conduction at the AV node

36
Q

How many various types of heart block exists?

A

1st, 2nd and 3rd degree

37
Q

Describe 1st degree heart block

A
  • A long PR interval of more than 1 big box.
  • This is benign
  • Can be caused by drugs, or just by ageing, generally not dangerous
38
Q

Describe 2nd degree AV block

A

Two types of 2nd degree AV block: Mobitz 1 and Mobitz 2

39
Q

What is observed in Mobitz 1 (2nd degree AV block)?

A
  • Long PR interval, but with each subsequent beat, the PR interval gets a bit longer, until eventually, there is no QRS and conduction has gone.
  • Wait for intrinsic SA activity to kick in again before we get another QRS wave.
40
Q

Wenckebach AV block is?

A

It is progressive PR prolongation

41
Q

Observe Mobitz 2

A

Rather than progressive PR prolongation, person has normal PR intervals.

However, random lost conduction and random blockage occurs.

PP interval is the same, and randomly it is blocked.

P waves progress at a constant rate.

This is a marker of more serious conduction disease.

42
Q

Mobitz 2 can progress into?

A

3rd degree AV

43
Q

What happens in 3rd Degree AV block

A
  • This is where there is a complete disconnect between the atria and the ventricles at the AV node in terms of electrical conduction.

P waves at normal rate.

Cardiomyocytes have their own intrinsic activity, so there is still a QRS complex, but they will have an escape rhythm that is usually at a slower rate.

44
Q

In 3rd degree AV block, there is no?

A

No relation between P wave and QRS, and AV conduction is not occurring.

45
Q

3rd degree AV block typically causes?

A

Typically causes bradycardia and needs a pacemaker.

46
Q

Danger of 3rd degree AV block?

A

Intrinsic ventricular activity can be very slow, and these people can faint and injure themselves and not wake up.

47
Q

What will left ventricular hypertrophy indicate?

A

Strong positive deflection compared to V1 and V2 where amplitude is moving away.

48
Q

Criteria of left ventricular hypertrophy

A

S (negative deflection) in V1 + R (positive deflection) in V5 or V6 of greater or equal to 35 mm.

R in a VL greater or equal to 11mm.

49
Q

Right bundle branch block

A
  • Conduction in the right bundle to the right ventricle is slow.
  • Common in healthy normal.
50
Q

Criteria of right bundle branch block

A

QRS is wide i.e. greater than 120ms.

V1 where there is an RSR’ (R wave, followed by S, then second more dominant R wave) what is markedly positive.

51
Q

Left bundle branch block

A

Conduction in the left bundle to the left ventricle is slow.

52
Q

Criteria of left bundle branch block

A

QRS is wide, i.e. > 120ms.

There is a dominant S wave (which may be a ‘W’ shape).

Last electrical activity is from the left ventricle (away from V1), which is dominant and unopposed by the right ventricle.

In V6 there may be a broad QRS with a notched ‘M’.

Block 4 (8 decks)

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