ECG 1

Question 1

Describe the components of a 12 ECG.

Answer 1

A 12 ECG includes three standard limb leads (I, II, III), augmented leads (aVR, aVL, aVF), six chest leads (V1-V6), and a rhythm strip.

Question 2

Define the purpose of a rhythm strip in an ECG.

Answer 2

The rhythm strip is a longer continuous recording of standard limb lead II, providing a detailed view of the heart’s electrical activity over time.

Question 3

Define the purpose of standard limb leads in an ECG.

Answer 3

Standard limb leads in an ECG focus on electrical events in the heart across the vertical or frontal plane, providing valuable information about the heart’s activity.

Question 4

Describe the standard limb lead II in an ECG.

Answer 4

It is considered the most normal ECG lead and resembles the stereotypical trace, with the recording electrode in the left leg relative to the electrode in the right arm.

Question 5

How does a wave of depolarisation affect the ECG trace when it spreads towards the left leg electrode?

Answer 5

It makes the left leg electrode positive relative to the right arm electrode, resulting in a positive going blip on the ECG trace.

Question 6

Define the PR interval in an ECG.

Answer 6

It is the time from the start of the P wave to the start of the QRS complex, representing the duration from atrial depolarisation to ventricular depolarisation.

Question 7

What does the QRS complex represent in an ECG?

Answer 7

It represents ventricular depolarisation.

Question 8

How is ventricular repolarisation depicted on an ECG trace?

Answer 8

It is shown by the T wave, indicating the recovery phase of the ventricles.

Question 9

Describe the significance of the u wave in an ECG.

Answer 9

The u wave’s significance is unclear, as its representation and role in cardiac activity remain uncertain.

Question 10

What is the direction of the wave of depolarisation that causes a negative going blip on the ECG trace?

Answer 10

It is moving away from the electrode in the left leg towards the electrode in the right arm, making the left leg electrode negative relative to the right arm electrode.

Question 11

How does a wave of repolarisation towards the left leg affect the ECG trace?

Answer 11

It makes the left leg electrode negative relative to the right arm electrode, resulting in a negative going blip on the ECG trace.

Question 12

Define the T wave in an ECG.

Answer 12

It represents ventricular repolarisation, indicating the recovery phase of the ventricles after depolarisation.

Question 13

Describe the time taken for the QRS complex in an ECG

Answer 13

The time taken for the cells in the ventricle to start depolarising to the last cells in the ventricle depolarising, usually about 0.08 s.

Question 14

Define the QT interval in an ECG

Answer 14

The time taken from the ventricles depolarising to repolarising again, which varies with heart rate but is approximately 0.42 s at a resting heart rate of 60 bpm.

Question 15

How does the size of the atria and ventricles affect ECG readings?

Answer 15

Atrial repolarisation is not visible on ECG because it coincides with ventricular depolarisation, which produces a larger signal due to the ventricles being much larger.

Question 16

Do different parts of the ventricle depolarise at the same time?

Answer 16

No, different parts depolarise at different times and in different directions, leading to the complexity of the QRS complex.

Question 17

Describe the depolarisation direction of the interventricular septum in an ECG

Answer 17

The interventricular septum depolarises from left to right, resulting in a negative Q wave when recorded from standard limb lead II.

Question 18

Explain the reason behind the positive T wave in an ECG

Answer 18

The T wave is positive-going because the wave of repolarisation moves away from the electrode in the left leg, making it more positive relative to the electrode in the right arm.

Question 19

Describe the difference in R wave size between standard limb lead II, I, and III in an ECG.

Answer 19

The R wave is bigger in standard limb lead II compared to standard limb lead I and III due to the alignment of the wave of depolarization with the axis of lead II.

Question 20

Define augmented limb leads in an ECG.

Answer 20

Augmented limb leads are derived from one limb lead and recorded with respect to the other two limb leads, providing additional perspectives on the electrical events in the heart.

Question 21

How are augmented limb leads aVR, aVL, and aVF recorded in an ECG?

Answer 21

aVR is recorded from the right arm relative to the left arm and left leg, aVL from the left arm relative to the right arm and left leg, and aVF from the left leg relative to the right arm and left arm.

Question 22

Describe the information provided by augmented limb leads in an ECG.

Answer 22

Augmented limb leads, along with standard limb leads, offer six different views of the electrical events in the heart, enhancing the understanding of frontal or vertical plane electrical activity.

Question 23

Do augmented limb leads aVR, aVL, and aVF show different R wave characteristics in an ECG?

Answer 23

Yes, the R wave characteristics differ in augmented limb leads - aVR typically shows a negative R wave, aVL may have a unique R wave appearance due to its perpendicular axis, and aVF usually displays a positive and reasonably large R wave.

Question 24

How does the alignment of the depolarization wave affect the R wave appearance in augmented limb leads?

Answer 24

The alignment of the depolarization wave with the axis of the lead influences the appearance of the R wave - positive in the direction of the axis, negative when moving away, and potentially ambiguous when perpendicular to the axis.

Question 25

Describe the placement of the 6 precordial or chest leads in an ECG.

Answer 25

The 6 precordial leads are arranged around the front of the heart to look at electrical events in the heart in the horizontal or transverse plane.

Question 26

Define the concept of ‘progression’ in an ECG.

Answer 26

Progression refers to the change in direction of R waves from negative to positive as you move from V1 to V6 in an ECG.

Question 27

How can the rhythm strip in an ECG be used to calculate heart rate?

Answer 27

By counting the number of R waves that occur during 30 large squares (equivalent to 6 seconds) and multiplying by 10.

Question 28

Describe the purpose of the rhythm strip in an ECG.

Answer 28

The rhythm strip provides a continuous recording from standard limb lead II, focusing on timing to calculate heart rate accurately.

Question 29

Do the limb leads and precordial leads in an ECG provide information from different planes?

Answer 29

Yes, the limb leads provide information in the frontal plane, while the precordial leads provide information in the transverse plane.

Question 30

How does the main wave of depolarization move in the ventricles of the heart during an ECG?

Answer 30

The main wave of depolarization moves from the endocardial surface to the epicardial surface, with the R wave directionally moving towards V6 and V5.

Question 31

Describe bradycardia and tachycardia based on heart rate values.

Answer 31

Bradycardia is when the heart rate is below 60 bpm, while tachycardia is when the heart rate is above 100 bpm.

Question 32

Define PR interval and its significance in ECG interpretation.

Answer 32

The PR interval is the time from the beginning of the P wave to the beginning of the QRS complex. An abnormal PR interval can indicate issues with atrioventricular conduction.

Question 33

How can a widened QRS complex on an ECG be indicative of specific heart conditions?

Answer 33

A widened QRS complex (>0.12 s) can suggest problems with the fast conducting system like bundle branch blocks, such as left bundle branch block or right bundle branch block.

Question 34

Describe the significance of ST segment elevation in an ECG.

Answer 34

ST segment elevation indicates a serious heart condition, such as a myocardial infarction (heart attack), with the extent of elevation correlating to the severity of the heart damage.

Question 35

What does the term STEMI stand for in the context of ECG interpretation?

Answer 35

STEMI stands for ST segment elevation myocardial infarction, which signifies a specific type of heart attack.

Question 36

How can one differentiate between a STEMI and an NSTEMI on an ECG?

Answer 36

In a STEMI, the ST segment is elevated above the baseline, indicating a more severe heart attack compared to an NSTEMI, where the ST segment is not elevated.