ECG PPT

Question 1

Advantages of ECG? (8)

Answer 1

1. Simple and cheap
   Info about:
2. Anatomical orientation of heart (axis)
3. Chamber sizes (hypertrophy)
4. Arrhythmias and conduction blocks
5. Myocardial ischaemia (degree and location)
6. Myocardial infarction
7. Congenital defects
8. Changes in cardiac function with time/therapy

Question 2

In an ECG how is energy released? What is the vector displaying?

Answer 2

• In several directions when the heart depolarizes (every myocyte fires)
• A resultant vector (vector of depolarization)

Question 3

The heart has a frequency of?

Answer 3

1 Hz (~1 cycle/sec)

Question 4

What are the frequencies of the muscle activity, respiration activity, and electrical activity picked up by the heart?

Answer 4

• Muscle 5 – 50Hz
• respiration 0.12-.5 Hz
• electrical 60 Hz

Question 5

Describe ECG filter

Answer 5

• ECG filter 0.5 to 40 Hz (some 100 or 150 Hz)

- -> high pass and low pass filters

Question 6

What does ECG measure?

Answer 6

measures movement of positive charge

Question 7

What does an upwards deflection mean?

Answer 7

movement of positive charge towards the electrode

Question 8

What does a downwards deflection mean?

Answer 8

movement of positive charge away from the electrode

Question 9

How is the recording electrode represented?

Answer 9

Recording electrode represented by +

Question 10

Describe the leads in a 12 lead ECG

Answer 10

a) Bipolar leads
- > 3 bipolar limb leads
b) Unipolar leads
- > 3 augmented voltage limb leads
- > 6 precordial or “chest” leads
c) Reference electrode

12 lead ECG – 10 electrodes

Question 11

Describe the bipolar limb leads

Answer 11

Standard leads
Lead I: RA- → LA+
Lead II: RA- →LL+
Lead III: LA-→LL+

-> Lead II views conducting system
Einthoven’s triangle

Einthoven’s Law I + III = II

Question 12

Describe the limb unipolar “augmented leads”

Answer 12

aVR: RA +ve , (LA+LL) -ve
aVL: LA +ve , (RA+LL) -ve
aVF: LL +ve , (LA+RA) -ve

Unipolar leads have no
negative pole

Question 13

Describe chest unipolar “precordial” leads

Answer 13

+:
V1 and V2 = septal
V3 and V4 = anterior
V5 and V6 = lateral

-:
Mean(I, II, III) = center of
heart

Question 14

Which leads are in the frontal plane? Which leads are in the transverse plane?

Answer 14

Frontal Plane:
Lead I
Lead II
Lead III
aVL
aVR
aVF

Transverse plane:
V1
V2
V3
V4
V5
V6

Question 15

What occurs in during AVN block?

Answer 15

long PR

Question 16

What occurs in during Preexcitation (WPW)?

Answer 16

short PQ

Question 17

What occurs in during Bundle branch block?

Answer 17

BBB

Question 18

What occurs in during Long-QT syndrome?

Answer 18

arrythmia

Question 19

What occurs in during Short-QT syndrome?

Answer 19

sudden death?

Question 20

Normal mean electrical axis?

Answer 20

0 to +90

Question 21

How to determine MEA?

Answer 21

1. Record the ECG from Leads I and III.
   2, Draw a line through the baseline.
2. Measure the net height of the Q, the R, and
   S points above and below the baseline.
3. Compute the sum of the Q, R, and S heights.
4. Draw a horizontal line,
   and another line at 60 degrees to it.
5. Mark off a vector whose length is proportional
   to the sum of Q, R, and S for Lead I from the
   origin on the horizontal line.
6. Mark off the vector for Lead III on the sloping line.
7. Draw a line perpendicular to the end of each vector.
8. Draw a resultant vector.
9. Use a protractor to measure the angle.