Brainscape's Knowledge GenomeTM

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


See full index

103-theme 3 > introduction to the ECG > Flashcards

introduction to the ECG Flashcards

1
Q

what is a syncytium?

A

one large cell having many nuclei that are not separated by cell membrane

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

what is a functional syncytium?

A

many cells functioning at once

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

what are the 3 types of cardiac myocytes?

A
  • pacemaker cells= for setting the heart’s rhythm
  • conducting cells= for transmitting rhythm throughout the heart
  • contractile cells= for contracting to that rhythm (most numerous)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

explain how the speed of propagation varies? 4

A
  • contractile= atrial and ventricular monocytes- 0.3-0.5m/s
  • conducting system (modified cardiomyocytes) purkinjie fibres up to 5m/s
  • throughout the AV node 0.05m/s
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

how are cardiomyocytes linked? 2

A
  • by low resistance pathways associated with gap junctions at the intercalated discs
  • when one action potential depolarizes one cell–> initiating an action potential in adjacent cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe the spread of impulse through the atria? 7

A
  • internodal bundles conduct the impulse from the SA node to the AV node
  • bundles ensure synchronous contraction of the aorta
  • conducting via atrial muscle would be slow (0.3-0.5m/s)
  • conducting via bundles in the atria
  • there are 4 specialised bundles in the atria
  • these contain purkinhie-like cells which are cardiomyocytes modified to conduct
  • bundles are in direct contact with the atrial muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

explain the impulse at the AV node? 7

A
  • AV node is the only point where the wave of depolarisation passes from the atria to the ventricles
  • AV node delays the wave of excitation from atria to ventricles by 0.1-0.2 seconds
  • the electrical delay means ventricles contract after the atria to permit longer and more effective ventricular filling
  • to permit longer and more effective ventricular filling
  • action potential conducted very slowly in the AV node (0.05m/s)
  • AV node is composed of small, modified myocytes
  • electrical connection between adjoining cells is weaker
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

explain ventricular propagation? 3

A
  • AV node connects to the bundle of His followed by the purkinjie fibre system
  • purkinjie fibres transmit the impulse rapidly to the main mass of the ventricles
  • from there, slower conduction between contractile monocytes can occur
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are purkinjie fibres?

A
  • very large monocytes- transmit the impulse faster- bigger diameter cells conduct faster
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what order does the heart depolarise in? 3

A
  • septum
  • spex
  • atrioventricular groove
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is an ECG? 5

A
  • gross electrical measurement of the heart
  • the electrical activity of the heart is measured on the skin
  • the individual currents of the cardia monocytes are tiny
  • these currents can be detected from the wrist and the ankle
  • this is possible because the heart is a functional syncytium in which large groups of cells all make electrical charges simultaneously
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what can the ECG diagnose? 4

A
  • excellent for rate- Holter monitor (ECG) allows 24/7 rate determination- especially useful when the articular rate is different from the ventricular rate
  • many subtleties- not a one stop diagnosis and patient history is essential
  • diagnosis requires other techniques
  • very fast and affordable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is a lead?

A

2 or 3 different electrodes placed on the body in different positions

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

what is the set up of lead II?

A
  • positive electrode on left leg
  • negative electrode on the right arm
  • ground electrode on the right leg (although it could be almost anywhere)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe the 12 standard leads? 3

A
  • 3 bipolar leads- I,II,III detect what happens in the frontal plane
  • 3- ‘augmented’ leads
  • 6 precordial leads
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how is switching between leads shown on an ECG?

A

vertical lines

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

what does the P wave show?

A

depolarisation of the atria in response to SA node triggering

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

what does the PR segment show?

A

delay of AV node to allow filling of the ventricles

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

what does the QRS complex show?

A

depolarisation of ventricles, triggers main pumping contractions

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

what does the ST segment show?

A

beginning of ventricular repolarization, should be flat

21
Q

what does the T wave show?

A

ventricular repolarisation

22
Q

describe the problems with the QRS complex? 2

A
  • if the ORS is wide or misshapen, then ventricular conduction is abnormal
  • large (deep) Q waves are a sign of dead tissue (only MI)
23
Q

what is the sinus rhythm? 4

A
  • when the heart rhythm is generated from the sinoatrial node
  • each P wave is followed by a QRS complex
  • every ORS complex is preceded with a P wave
  • when PR interval is always normal
24
Q

what is sinus tachycardia?

A
  • tachycardia driven by the SA node beating too quickly- it has normal PR intervals
25
Q

what is the normal PR interval and its duration?

A

start of the P wave to the start of the QRS complex

3-5 little boxes (120-200ms)

26
Q

what is the normal QT interval and its duration?

A

from the start of the QRS complex to the end of the T wave

9-11.5 boxes (360-460ms)

27
Q

what is the ST segment on the graph?

A

from the end of the QRS complex to the start of the T wave

28
Q

what is the normal QRS complex duration?

A

2-3 boxes (80-120ms)

29
Q

how long do these boxes count for on an ECG:

  • little box
  • big box
  • 5 big boxes
A
  • 40ms
  • 200ms
  • 1 second
30
Q

how do you calculate ventricular rate on an ECG?

A

count between the R waves

31
Q

how to calculate heart rate on an ECG?

A

count between P waves

32
Q

how do you work out rate on an ECG?

A

300/big boxes

33
Q

what does the parasympathetic input of the heart lead to? 5

A
  • vagus nerve leads to
  • muscarinic stimulation
  • decreased heart rate
  • decreased contractility
  • decreased conduction velocity
34
Q

what does the sympathetic input of the heart lead to? 3

A
  • increase in heart rate
  • increase in contractility
  • increase in conduction velocity
35
Q

what happens during parasympathetic withdrawal? 3

what can cause it?

A
  • increased heart rate
  • increased contractility
  • increased conduction velocity
  • atropine–> muscarinic antagonist
36
Q

what is a heart block? 2

A
  • a type of dysrhythmia (bad rhythm)

- any kind of impulse conduction that blocks the heart

37
Q

what is an AV heart block?

A
  • a delay or failure of atrial signal stimulating ventricle
38
Q

what can be the cause of a AV heart block? 3

A
  • ischaemia of AV node or AV bundle
  • compression of AV bundle by scar of calcified tissue
  • inflammation of the AV node or bundle
39
Q

what are the symptoms of a heart block? 4

A
  • can be asymptomatic
  • palpitations
  • hypotension like symptoms: dizziness, syncope
  • risk of sudden death
40
Q

what is a first degree heart block? 6

A
  • when the PR interval is bigger than 5 little boxes
  • all P waves are followed by QRS
  • almost always asymptomatic
  • often young people
  • delayed AV node transmission
  • rarely treated
41
Q

what is mobitz type 1? 6

A

-second degree heart block
-some P waves are blocked are blocked and are not followed by QRS (some ORS are missing)
-wenckebach
-PR interval gets longer until QRS wave fails to follow the P wave
-likely cause is AV node damage
usually no treatment given

42
Q

what is mobitz type 2? 8

A
  • second degree heart block
  • hay
  • some P waves are blocked and are not followed by QRS
  • PR interval remains the same
  • likely a problem in the bundle of His
  • high risk
  • can progress to a 3rd degree heart block
  • implant pacemaker
43
Q

what is a third degree heart block? 6

A
  • atrial signals consistantly fall to arrive at ventricles
  • ventricular rate is consistent(30-40 bpm)
  • time between atrial beats and ventricular beats is variable
  • PR interval varies radically- sometimes more then 12 boxes
  • intrinsic ventricular rate is low
  • atrial beats are consistent
44
Q

what are premature beats?

A

early and triggered by irritable tissue

45
Q

what are escape beats? 2

A
  • are late and triggered by natural rhythmicity of non-atrial tissue
  • occur when the atrial signal is very delayed or prevented (in third degree heart block)
46
Q

what is premature ventricular control? 4

A
  • unusually wide and weird looking ventricular activity
  • no S wave, instead a wide negative dip where the T wave should be
  • often beat triggered in middle of myocardium- the two ventricles are electrically unsynchronised
  • width is determined by slowed conduction velocity
47
Q

what is atrial fibrillation? 6

A
  • disorganised electrical activity in atria
  • no P wave, instead a flat and wiggly line
  • ventricular rate is fat and irregular: many signals reach the AV node
  • AF is very common in the elderly
  • can lead to thrombus formation in atrium due to slow flow of blood, this leads to a stroke risk
  • anticoagulants can try and prevent thrombus
48
Q

what is respiratory sinus arrhythmia? 5

A
  • heartbeat is slightly faster during inspiration, slightly slower during expiration
  • normal
  • usually only present in children and athletes
  • caused by respiratory centres in the brains medulla
  • observe ventricular rate: inverse of RR interval
49
Q

what does ST segment elevation show? 2

A
  • acute sign of MI

- isoelectric baseline: from end of T to the next P

103-theme 3 (18 decks)

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