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LSS 1 > Cardiovascular Systems 10 - Electrocardiography > Flashcards

Cardiovascular Systems 10 - Electrocardiography Flashcards

1
Q

What is a lead in an ECG?

A

Leads are a view of the electrical activity of the heart, they are not a cable/wire

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2
Q

What is a vector?

A

A quantity that has both magnitude and direction

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3
Q

Describe what can be deduced from the lines of the ECG, including steepness, direction and width of the deflection.

A
  • The isoelectric line is where there is no net change in voltage, as vectors are perpendicular to the lead
  • The steepness of the line shows the velocity of an action potential
  • The width of the deflection shows the duration
  • Upward deflections are towards the cathode (+) and downward are towards the anode (-)
  • Every wave has both up and downstrokes
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4
Q

What is the P wave?

A
  • The electrical signal that stimulates contraction of the atria
  • Generated by the sinoatrial node
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5
Q

What is the QRS complex?

A
  • The electrical signal that stimulates contraction of the ventricles
  • Q is where the electrical signal is in bundle branches
  • R is where the signal is in purkinje fibres (early ventricular depolarisation)
  • S is also where the signal is in purkinje fibres (late ventricular depolarisation)
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6
Q

What is the T wave?

A

The electrical signal tat signifies relaxation of the ventricles

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7
Q

Where is the electrical signal in the heart between the P wave and QRS complex?

A
  • It is in the atrioventricular node
  • It is isoelectric
  • AV node conducts slowly
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8
Q

What causes the line between the QRS complex and the T wave?

A

The signal is in the fully depolarised ventricles, it is isoelectric.

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9
Q

Describe the placement of electrodes on a patient?

A
  • One on the right arm, one the left arm, right leg and left leg.
  • The other 6 (V1-V6) are on the ribs
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10
Q

Where is the V1 electrode?

A

Right sternal border in the 4th intercostal space

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11
Q

Where is the V2 electrode?

A

Left sternal border in the 4th intercostal space

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12
Q

Where is the V3 electrode?

A

Halfway between V2 and V4

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13
Q

Where is the V4 electrode?

A

Mid-clavicular line in the 5th intercostal space

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14
Q

Where is the V5 electrode?

A

Anterior axillary line at the level of V4

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15
Q

Where is the V6 electrode?

A

Mid-axilliary line at the level of V4

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16
Q

What is lead 1?

A

Right arm to left arm

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17
Q

What is lead II?

A

Right arm to left leg

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18
Q

What is lead III?

A

Left arm to left leg

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19
Q

How is heart rate calculated form an ECG?

A

300/number of big squares

20
Q

Which is bigger, T wave or P wave?

21
Q

How is the cardiac axis calculated?

A
  • Lead II and aVL are used, as they are 90 degrees apart
  • Amplitude fo LII is calculated, as it that of aVL. This is done by taking away the number of squares of the S from that of the R downward stroke of the QRS complex.
  • These are used as lines of a triangle
  • Trigonometry is used to find the hypothesis
  • 60-answer to find the angle of the heart (as the LII line is at an angle of 60 degrees)
22
Q

Which leads have a virtual anode?

A

aVR, aVL, aVF, V1-V6

23
Q

Which leads have a fixed anode?

A

LI, LII, LIII

24
Q

Which lead is the most commonly used single lead?

25
What is the normal range of the cardiac axis?
-30 to +90 degrees
26
What is the approach used to take and analyse an ECG?
- Ensure it is correct patient - Look at rate and rhythm - P-wave and PR interval - QRS duration - QRS axis - ST segment - QT interval - T wave
27
Describe the ECG appearance in sinus bradycardia.
- Each P wave is followed by QRS | - Rate is regular but slow
28
What is the cause of sinus bradycardia?
- Healthy - Caused by medication - Caused by vagal stimulation
29
Describe the ECG appearance in sinus tachycardia.
- P wave followed by QRS | - Regular rate but fast
30
What causes sinus tachycardia?
Physiological response (secondary)
31
Describe the ECG appearance in sinus arrhythmia.
- Each P wave is followed by a QRS wave - Rate is irregular, but normal. - The R-R interval varies with breathing
32
Describe the ECG appearance in atrial fibrillation.
- Oscillating baseline, the atria contract asynchronously - Rhythm can be irregular, rate may be slow - Increased clot risk due to turbulent blood flow
33
Describe the ECG appearance of atrial flutter.
- Saw tooth pattern in the baseline of II, III, aVF - The atrial to ventricular beats at 2:1, 3:1 or higher ratio - The saw tooth is not always visible in all leads
34
Describe the ECG appearance in first degree heart block.
- Prolonged PR segment/interval due to slower AV conduction | - Regular rhythm, P wave before every QRS
35
Describe the ECG appearance of second degree heart block (Mobitz 1)
- Gradual prolongation of the PR interval until a beat is skipped - Most P waves followed by QRS, some are not - Regularly irregular (each component is regular, but the regularities are different)
36
Describe the ECG appearance of second degree heart block (Mobitz II)
- P waves are regular, but only some are followed by QRS - There is no PR prolongation - Regularly irregular, there is a ratio of successes to failures
37
Describe the ECG appearance of third degree heart block.
- P waves are regular, as are QRS, but there is no relationship - P waves can be hidden within QRS - There is non-sinus rhythm
38
Which type of heart block is the most progressed?
- Third degree heart block is complete - First degree is the most benign, it is a disease of aging - Second degree (Mobitz II) is more serious than Mobitz I, as it can rapidly deteriorate into third degree
39
Describe the ECG appearance of ventricular tachycardia.
- P waves are hidden - The rate is irregular and fast (100-200bpm) - High risk of fibrillation - This is a shockable rhythm
40
Describe the ECG appearance of ventricular fibrillation.
- Heart rate is irregular, 250bpm+ | - The heart cannot generate an output- just lots of squiggly lines!
41
Describe the ECG appearance of ST elevation
- P waves are visible and always followed by QRS - Rhythm is regular and the rate is normal (85bpm) - The ST segment is elevated 2mm or more over the isoelectric line
42
What causes ST elevation?
Infarction
43
Describe the ECG appearance of ST depression.
- P waves are visible, always followed by QRS - Rhythm is regular and heart rate is normal - The ST segment is depressed 2mm or more below the isoelectric line
44
What causes ST depression?
Myocardial ischaemia (coronary insufficiency)
45
What is the clinical relevance of ECG?
- Cheap, reliable and fast way to assess heart function | - Can evaluate the conduction system and structure

LSS 1 (35 decks)

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