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Electrocardiography > Approach to interpreting an ECG > Flashcards

Approach to interpreting an ECG Flashcards

1
Q

What is the first step in ECG interpretation?

A

Check the patient’s details, including age, clinical history, and the date/time of the ECG.

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2
Q

What should you check for on the ECG machine before interpreting?

A

Verify that the ECG calibration is correct (standard calibration: 25 mm/s, 10 mm = 1 mV).

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3
Q

What is the normal paper speed for an ECG?

A

25 mm per second.

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4
Q

What is the normal amplitude for a 1 mV signal on ECG paper?

A

10 mm (10 small squares).

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5
Q

What are the three main waves on a normal ECG?

A

P wave, QRS complex, and T wave.

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6
Q

What is the normal duration of the P wave?

A

Less than 0.12 seconds (less than 3 small squares).

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7
Q

What does the P wave represent?

A

Atrial depolarization.

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8
Q

What is the normal axis of the P wave?

A

Positive in leads I, II, and aVF, and negative in aVR.

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9
Q

What does the PR interval represent?

A

The time taken for electrical conduction from the atria to the ventricles.

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10
Q

What is the normal duration of the PR interval?

A

0.12 to 0.20 seconds (3 to 5 small squares).

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11
Q

What does the QRS complex represent?

A

Ventricular depolarization.

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12
Q

What is the normal duration of the QRS complex?

A

Less than 0.12 seconds (less than 3 small squares).

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13
Q

What is the normal amplitude of the QRS complex?

A

Typically less than 2.5 mV (25 mm or 2.5 large squares).

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14
Q

What is the ST segment?

A

The flat, isoelectric section between the end of the QRS complex and the start of the T wave.

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15
Q

What does the ST segment represent?

A

The interval between ventricular depolarization and repolarization.

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16
Q

What does the T wave represent?

A

Ventricular repolarization.

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17
Q

What is the normal direction of the T wave?

A

It is normally upright in leads I, II, and V3-V6, and inverted in aVR.

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18
Q

What is the QT interval?

A

The time from the start of the QRS complex to the end of the T wave, representing the total time of ventricular depolarization and repolarization.

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19
Q

What is the normal QT interval duration?

A

Less than 0.44 seconds in men and 0.46 seconds in women.

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20
Q

What does the U wave represent?

A

The U wave represents repolarization of the Purkinje fibers or after-potentials of ventricular depolarization.

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21
Q

How do you calculate heart rate from an ECG?

A

Use the 300 rule: Divide 300 by the number of large squares between R waves.

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22
Q

What should you assess after heart rate in ECG interpretation?

A

Assess the rhythm: Check if it is regular or irregular.

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23
Q

How do you identify regularity of rhythm?

A

Measure the distance between consecutive R waves (R-R intervals).

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24
Q

What is the significance of the P-QRS-T sequence?

A

It ensures that every P wave is followed by a QRS complex and every QRS is followed by a T wave, indicating normal conduction.

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25
Q

How do you determine if there is a normal sinus rhythm?

A

There is a P wave before every QRS complex, and the P wave is upright in leads I and II and inverted in aVR.

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26
Q

What is the axis of an ECG?

A

The direction of the heart’s electrical activity in the frontal plane.

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27
Q

How do you determine the electrical axis of the heart?

A

Check the net deflection of the QRS complex in leads I and aVF.

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28
Q

What is the normal electrical axis?

A

Between -30° and +90°.

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29
Q

What does a positive QRS in leads I and aVF indicate?

A

Normal axis.

30
Q

What is the isoelectric point on an ECG?

A

The point where the net deflection is zero, often used to assess electrical axis.

31
Q

What does the presence of a Q wave indicate?

A

Initial depolarization of the ventricles, normally present in some leads like III and aVL.

32
Q

How do you assess the width of the QRS complex?

A

Measure the duration from the start of the Q wave to the end of the S wave, and ensure it is less than 0.12 seconds.

33
Q

What leads represent the lateral aspect of the heart?

A

Leads I, aVL, V5, and V6.

34
Q

What leads represent the inferior aspect of the heart?

A

Leads II, III, and aVF.

35
Q

What leads represent the anterior aspect of the heart?

A

Leads V1 to V4.

36
Q

What does an inverted T wave in lead aVR indicate?

A

Normal finding; T waves are expected to be inverted in aVR.

37
Q

What are the precordial leads?

A

Leads V1 to V6.

38
Q

Where is lead V1 placed?

A

At the fourth intercostal space to the right of the sternum.

39
Q

Where is lead V4 placed?

A

At the fifth intercostal space, midclavicular line.

40
Q

What does lead V1 primarily represent?

A

The electrical activity of the right ventricle.

41
Q

What should be the normal appearance of the T wave in precordial leads?

A

It should be upright in V3 to V6.

42
Q

What is the role of augmented limb leads?

A

They provide additional views of the heart’s electrical activity: aVR, aVL, and aVF.

43
Q

What is the purpose of the chest leads in an ECG?

A

To provide horizontal plane views of the heart, focusing on the anterior and lateral walls.

44
Q

What does the term “biphasic wave” refer to in an ECG?

A

A wave that has both positive and negative components.

45
Q

What does a consistent R-R interval suggest about the rhythm?

A

The rhythm is regular.

46
Q

How do you assess P wave morphology?

A

Check for shape, duration, and amplitude in lead II or V1.

47
Q

What does an upward P wave in lead II indicate?

A

It indicates normal atrial depolarization from the SA node.

48
Q

What does an isoelectric ST segment suggest?

A

No ischemia or injury, normal finding.

49
Q

What is the significance of the J point?

A

The J point marks the end of ventricular depolarization and the start of repolarization, located at the beginning of the ST segment.

50
Q

Why is it important to systematically review all ECG leads?

A

To ensure that no abnormal findings are missed and to assess the heart’s electrical activity from multiple angles.

51
Q

Where is the Right Arm (RA) electrode placed in ECG?

A

The RA electrode is placed just below the right clavicle, near the right shoulder.

52
Q

Where is the Left Arm (LA) electrode placed in ECG?

A

The LA electrode is placed just below the left clavicle, near the left shoulder.

53
Q

Where is the Right Leg (RL) electrode placed in ECG?

A

The RL electrode is placed on the right lower leg, just above the ankle or knee. It serves as the ground electrode.

54
Q

Where is the Left Leg (LL) electrode placed in ECG?

A

The LL electrode is placed on the left lower leg, just above the ankle or knee.

55
Q

What is the primary purpose of the Right Leg (RL) electrode in an ECG?

A

The RL electrode is used as the ground or neutral electrode.

56
Q

How many limb electrodes are placed in a standard ECG?

A

Four electrodes: Right Arm (RA), Left Arm (LA), Right Leg (RL), and Left Leg (LL).

57
Q

Which limb leads form the Einthoven’s triangle?

A

Leads I, II, and III form the Einthoven’s triangle, derived from the RA, LA, and LL electrodes.

58
Q

What is the function of the limb leads in ECG?

A

Limb leads capture electrical activity from the frontal plane of the heart.

59
Q

How does Lead I record electrical activity?

A

Lead I records the electrical activity between the Right Arm (RA) and Left Arm (LA) electrodes.

60
Q

How does Lead II record electrical activity?

A

Lead II records the electrical activity between the Right Arm (RA) and Left Leg (LL) electrodes.

61
Q

How does Lead III record electrical activity?

A

Lead III records the electrical activity between the Left Arm (LA) and Left Leg (LL) electrodes.

62
Q

What are the augmented limb leads in an ECG?

A

The augmented leads are aVR, aVL, and aVF, which provide additional views of the heart.

63
Q

Where does the augmented lead aVR record from?

A

The aVR lead records from the Right Arm (RA) in relation to the central point between LA and LL.

64
Q

Where does the augmented lead aVL record from?

A

The aVL lead records from the Left Arm (LA) in relation to the central point between RA and LL.

65
Q

Where does the augmented lead aVF record from?

A

The aVF lead records from the Left Leg (LL) in relation to the central point between RA and LA.

66
Q

What is the frontal plane in ECG interpretation?

A

The frontal plane is the vertical plane that the limb leads (I, II, III, aVR, aVL, aVF) monitor, capturing electrical activity from the top to the bottom of the heart.

67
Q

Why is proper limb lead placement important in ECG?

A

Proper limb lead placement ensures accurate recording of the heart’s electrical activity and avoids misdiagnosis.

68
Q

How should the skin be prepared before placing ECG electrodes?

A

Clean the skin to remove oils and dirt, and shave hair if necessary to ensure good electrode contact.

69
Q

Can limb leads be placed on the torso?

A

Yes, limb leads can be placed on the torso in emergency situations or if the patient’s limbs are unavailable, but this can affect the accuracy of the ECG.

70
Q

What is the purpose of the Einthoven triangle in ECG?

A

The Einthoven triangle helps in calculating the heart’s electrical axis using Leads I, II, and III.

Electrocardiography (5 decks)

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