Introduction to the 12-Lead ECG Interpretation

Question 1

A right bundle-branch block is indicated by __________.

Answer 1

a widened QRS that is positive in right-sided leads and negative in left-sided leads

Question 2

What is the orientation of lead I?

Answer 2

Positive on left hand and negative on right hand

Question 3

Lead II and lead III are both positive on the left foot, but the negative lead of II is on the ______ hand and the negative lead of III is on the ______ hand.

Answer 3

right; left

Question 4

Left bundle-branch blocks lead to a widened QRS that is away from _____ and towards _____; thus, widened QRS waves will be positive in left-sided leads and negative in right-sided leads.

Answer 4

V1; V6

Question 5

A normal QRS axis is positive in leads _______.

Answer 5

I and II

Question 6

The _____ half of the P wave is the right atrium, so right atrial enlargement manifests in _______.

Answer 6

left; increased amplitude of the left side of the P wave

Question 7

A 12-lead ECG in left ventricular hypertrophy will display __________.

Answer 7

markedly increased voltage amplitude of QRS, especially in V5 and V6

Question 8

Right-ventricular hypertrophy will display ________.

Answer 8

markedly increased voltage of the QRS wave, especially in V1 and V2

Question 9

Where will anteroseptal infarctions show up?

Answer 9

V1 and V2

Question 10

Where will anterior wall infarctions show up?

Answer 10

V3 and V4

Question 11

Anterolateral infarctions will show up on the _______ leads.

Answer 11

V5 and V6

Question 12

Inferior wall infarctions will lead to _______.

Answer 12

II, III, and aVF ST elevations

Question 13

Remember that acute pericarditis will display ___________.

Answer 13

diffuse ST elevation without Q waves

Question 14

The normal axis of the ventricles is _________, with 0° being directly to the patient’s left and positive being clockwise.

Answer 14

-30° to +90°

Question 15

Other than bundle blocks, _______ can also produce widened QRS waves.

Answer 15

ectopic pacemakers in the ventricles

Question 16

Hemiblocks do not widen the QRS wave, but they do change the axis; left anterior fascicle blocks lead to ________ deviation, while left posterior fascicle blocks lead to _______ deviation.

Answer 16

left axis; right axis

Question 17

Ischemia due to increased oxygen demand leads to ____________, while ischemia due to coronary obstruction leads to __________.

Answer 17

depressed ST segment; T wave inversion

Question 18

________ are usually the last ECG finding to develop after an MI.

Answer 18

Q waves

Question 19

Subendocardial infarcts are displayed by ____________.

Answer 19

ST depression without Q waves

Question 20

In addition to hemiblocks, axis shifts can also originate from __________.

Answer 20

unilateral hypertrophy

Question 21

ST elevation indicates either _____________.

Answer 21

injury if localized or pericarditis if diffuse