ECG

Question 1

Abnormalities in which leads shows patholgy in which areas of the heart?

Answer 1

Question 2

What are the individual leads of an ECG measuring?

Answer 2

During the cardiac cycle different regions of the heart are depolarized, or polarized, creating a charge separation, or dipole. The dipole generates an electrical field (lines of isopotential) that are measurable with the two electrodes.

Question 3

What determines the magnitude of the electrical dipole?

Answer 3

Tthe mass of cardiac muscle that is involved in the generation of the signal (Ventricles make a bigger signal that the atria)

Question 4

What determines the direction of the electrical dipole?

Answer 4

Determined by the overall activity of the heart any instant in time and varies during the cardiac cycle

Question 5

Is the positive limb electrode the recording or the reference electrode?

Answer 5

Recording

Question 6

Is the negative limb electrode the recording or the reference electrode?

Answer 6

Reference

Question 7

At which angle does each of the limb leads look at the heart?

Answer 7

• Lead I looks at the heart at 0 degrees (3 o’clock) - Lead II looks at the heart at +60 degrees (5 o’clock) - Lead III looks at the heart at 120 degrees (7 o’clock)

Question 8

**Einthoven’s Triangle

Answer 8

Formed by the 3 limb leads, which ensure no area of the heart is undetected

Question 9

Which part of the cardiac cycle is represented by the PR interval?

Answer 9

AV nodal delay between atrial and ventricular contraction

Question 10

Which part of the cardiac cycle is represented by the TP interval?

Answer 10

Diastole

Question 11

**Goldberger’s method

Answer 11

In augmented limb leads, - uses one electrode as the recording electrode (+ve), but uses two others as the reference electrodes (-ve

Question 12

Electrical Axis of the Heart

Answer 12

Mean direction of the action potentials traveling through the ventricles during ventricular activation (depolarization).

Question 13

What is normal axis deviation and what does it look like on an ECG?

Answer 13

QRS axis between -30 and +90 degrees On ECG: Both leads I and II are pointing up

Question 14

What is left axis deviation and what does it look like on an ECG?

Answer 14

QRS axis less than -30 degrees On ECG: Lead I is pointing up and II is pointing down (‘leaving’ each other)

Question 15

What is right axis deviation and what does it look like on an ECG?

Answer 15

QRS axis more than +90 degrees On ECG: Lead I is pointing down and Lead II is pointing up (‘reaching’ for each other)

Question 16

How long is a normal PR interval (AV nodal delay) on ECG?

Answer 16

0.12-0.2 secs (3-5 small squares)

Question 17

How long is a normal P wave on ECG?

Answer 17

0.08-0.1 secs

Question 18

What is the standard speed of ECG paper?

Answer 18

25 mm/sec

Question 19

What time length does one small ECG box represent?

Answer 19

0.04secs

Question 20

What time length does one large ECG box represent?

Answer 20

0.2secs

Question 21

How many large boxes are there in a second and a minute on ECG?

Answer 21

5 in a second and 300 in a minute

Question 22

How do you determine heart rate on ECG?

Answer 22

300/number of large boxes between beats or 300/numer of large boxes between R-R interval

Question 23

How many leads are the and how many wires are there for ECG?

Answer 23

12 leads but only 10 wires. - Wires = connect the electrodes to the ECG machine Leads = the imaginary lines between the electrodes

Question 24

What steps would you go through when approaching an ECG?

Answer 24

• 1. Verify patient details: name and DOB
• 2. Check date and time in which ECG was taken
• 3. Check the calibration of the ECG paper
• 4. Look at the rhythm strip
     * a. Is electrical activity present?
     * b. Is the rhythm regular or irregular? Spaces between the QRS complexes are uniform
     * c. What is the heart rate? (300/number of large squares/number of QRS in 30 large x10)
     * d. P-waves present?
     * e. What is the PR interval?
     * f. Is each P-Wave followed by a QRS complex?
     * g. Is the QRS duration normal?
• 5. Look at individual leads for voltage criteria changes or any ST or T wave changes

Question 25

How long do normal QRS complexes last?

Question 26

**Irregularly irregular rhythm with absent P waves and normal QRS =

Answer 26

Atrial Fibrillation

Question 27

What does ventricular fibrillation look like?

Answer 27

Question 28

What does Ventricular Tachycardia look like?

Answer 28

Question 29

What actually is an ECG?

Answer 29

the detection by surface electrodes of the electrical activation of the heart muscle cells.

Question 30

What occurs during the TP interval?

Answer 30

Diastole

Question 31

Where do you place the chest leads?

Answer 31