Deck 9: Introduction to the 12-Lead Electrocardiogram

Question 1

Patients who experience a(n) _____ myocardial infarction have a greater incidence of heart failure and cardiogenic shock than those who have myocardial infarctions affecting other areas of the left ventricle.

A) lateral
B) posterior
C) inferior
D) anterior

Answer 1

D
Because the left anterior descending artery supplies approximately 40% of the heart's blood and a critical section of the left ventricle, a blockage in this area can lead to left ventricular dysfunction, including heart failure and cardiogenic shock.

Question 2

Which leads look at adjoining tissue in the inferior region of the left ventricle?

A) I, aVL
B) V1, V2
C) V3, V4, V5
D) II, III, aVF

Answer 2

D
Leads II, III, and aVF view adjoining tissue in the inferior region of the left ventricle.

Question 3

Normal electrical axis lies between _____ degrees.

A) -30 and +90
B) +90 and +180
C) -91 and -180
D) -1 and -90

Answer 3

A
In adults, the normal QRS axis is considered to be between -30 degrees and +90 degrees in the frontal plane.

Question 4

Lead aVL views the _____.

A) interatrial septum
B) lateral wall of the left ventricle
C) inferior wall of the left ventricle
D) anterior wall of the right ventricle

Question 5

An ECG machine's sensitivity must be calibrated so that a 1-millivolt electrical signal will produce a deflection measuring exactly _____ mm tall.

A) 0.5
B) 1
C) 5
D) 10

Question 6

Which of the following ECG changes is one of the earliest to occur during an ST elevation infarction, but may have resolved by the time the patient seeks medical assistance?

A) Pathologic Q waves
B) Hyperacute T waves
C) Horizontal ST segments
D) Lengthening of the QT interval

Question 7

Lead V? views the _____ wall of the left ventricle.

A) lateral
B) anterior
C) posterior
D) inferior

Question 8

Hypertrophy refers to a(n) _____.

A) delay in impulse conduction through the SA node
B) disturbance in impulse conduction through the AV junction
C) increase in the diameter of a chamber of the heart caused by volume overload
D) increase in the thickness of a heart chamber because of chronic pressure overload

Question 9

Lead V? views the _____.

A) septum
B) inferior wall of the left ventricle
C) lateral wall of the right ventricle
D) anterior wall of the right ventricle

Question 10

Where should the positive electrode for lead V? be positioned?

A) Right side of the sternum, fourth intercostal space
B) Left midaxillary line at the same level as V4
C) Left side of the sternum, fourth intercostal space
D) Left anterior axillary line at the same level as V4

Question 11

Which leads face the septum?

A) II, aVF
B) V1, V2
C) V5, V6
D) I, aVL

Question 12

Lead II views the _____ wall of the left ventricle.

A) anterior
B) inferior
C) septal
D) lateral

Question 13

Which of the following leads should be used to view the right ventricle?

A) V3
B) V7
C) V4R
D) V6

Question 14

Where should the positive electrode for lead V? be positioned?

A) Right side of the sternum, fourth intercostal space
B) Left midaxillary line at the same level as V4
C) Left side of the sternum, fourth intercostal space
D) Left anterior axillary line at the same level as V4

Question 15

Anterior or lateral wall myocardial infarctions are most often a result of an occlusion of the _____ coronary artery.

A) left
B) right

Question 16

A standard 12-lead ECG provides views of the heart in _____.

A) the frontal plane only
B) the sagittal plane only
C) the horizontal plane only
D) both the frontal and the horizontal planes

Question 17

The inferior wall of the left ventricle is supplied by the _____ coronary artery in most of the population.

A) left
B) right

Question 18

Poor R-wave progression is a phrase used to describe R waves that decrease in size from V? to V?. This is often seen in an _____ infarction.

A) anteroseptal
B) anterolateral
C) inferolateral
D) inferoposterior

Question 19

Lead V? views the _____ wall of the left ventricle.

A) lateral
B) anterior
C) posterior
D) inferior

Question 20

Which leads look at adjoining tissue in the anterior region of the left ventricle?

A) II, III, aVF
B) V2, V3, V4
C) I, aVL, V5
D) aVR, aVL, aVF

Question 21

Describe the appearance of a pathologic Q wave.

Question 22

The coronary arteries originate at the base of the _____.

Question 23

When reviewing a 12-lead ECG, intervals and duration are usually expressed in _____.

Question 24

List the ECG leads that view the heart in the horizontal plane, allowing a view of the front and left side of the heart.

Question 25

Indicative ECG changes observed in leads V?, V?, V?, and V? suggest that the _____ wall of the _____ ventricle is affected.

A) posterior; right
B) anteroseptal; left
C) inferolateral; left
D) anterolateral; right

Question 26

Lead I is perpendicular to lead _____.

A) II
B) III
C) aVF
D) aVL

Question 27

The axes of leads I, II, and III form an equilateral triangle with the heart at the center (Einthoven's triangle). If the augmented limb leads are added to this configuration and the axes of the six leads moved in a way in which they bisect each other, the result is the _______________.

Question 28

Acute coronary syndromes consist of three major syndromes that are related. List the three syndromes.

Question 29

List six leads that view the heart in the frontal plane.

Question 30

Lead I views the _____.

A) septum
B) inferior wall of the left ventricle
C) lateral wall of the left ventricle
D) anterior wall of the right ventricle

Question 31

Placement of right chest leads is identical to the standard chest leads except on the right side of the chest.

Question 32

An abnormal (i.e., pathologic) Q wave indicates the presence of dead myocardial tissue.

Question 33

The chest leads are the only unipolar leads in the standard 12-lead ECG.

Question 34

When you read a 12-lead ECG from left to right, the ECG tracing is continuous.

Question 35

What two factors determine the portion of the heart that each lead "sees"?

Question 36

Explain the meaning of the letters in aVR, aVL, and aVF.