Cardiology\ Echocardiography

Question 1

On an electrocardiography (ECG), what is the unit of measurement on the x axis?

Answer 1

Seconds

Question 2

On an electrocardiography (ECG), what is the unit of measurement on the y axis?

Answer 2

Millivolts

Question 3

On an electrocardiography (ECG), what is the dimensions of a small box?

Answer 3

1 × 1 mm

Question 4

On the ECG what is the dimensions of a large box?

Answer 4

5 × 5 mm

Question 5

On the ECG what is the length of time repesented by a small box?

Answer 5

0.04 seconds

Question 6

On the ECG what is the length of time represented by a large box?

Answer 6

0.2 seconds (or 0.04 seconds × 5)

Question 7

On the ECG what is the name for a positive or negative deflection from the baseline?

Answer 7

Wave

Question 8

On the ECG what is the name for a line between two waves?

Answer 8

Segment

Question 9

On the ECG what is the name for a segment and wave combination?

Answer 9

Interval

Question 10

Where are the precordial leads placed?

Answer 10

• V1: 4th intercostal space (ICS), to the right of the sternum
• V2: 4th ICS, to the left of the sternum
• V3: between V2 and V4
• V4: 5th ICS, at the mid-clavicular line
• V5: at the same level as V4 at the anterior axillary line
• V6: at the same level as V4 and V5, at the mid-axillary line

Question 11

What represents atrial contraction?

Answer 11

P wave

Question 12

What represents ventricular contraction?

Answer 12

QRS complex

Question 13

What represents ventricular repolarization?

Answer 13

T wave

Question 14

When reading an ECG, what components should be covered?

Answer 14

• Rate
• rhythm
• axis
• intervals
• hypertrophy
• evidence of myocardial infarction

Question 15

How can the rate be determined?

Answer 15

Here are two ways:

(1) Count the number of big boxes between QRS complexes. 1 big box = 300 beats per minute (bpm); 2 = 150 bpm; 3 = 100 bpm; 4 = 75 bpm; 5 = 60 bpm; 6 = 50 bpm. It’s helpful to memorize the sequence: 300-150-100-75-60-50.
(2) Count the number of QRS complexes on the last line at the bottom of the page and multiply that number by 6 (the rhythm strip represents 10 seconds worth of electrical activity).

Question 16

What does normal sinus rhythm (NSR) indicate?

Answer 16

NSR indicates that the electrical impulse in the heart is generated by the sinoatrial node and is following the heart’s normal circuitry (ie, from the sinoatrial node to the atrioventricular node to the bundle of His and to the Purkinje fibers)

Question 17

What ECG features indicate that the patient is in sinus rhythm and that the impulse is being generated by the sinoatrial node?

Answer 17

• Each QRS complex is preceded by a P wave.
• The P waves are positive in I, II, and aVF
  
  • a positive deflection indicates that an impulse is approaching a lead. I, II, and aVF are at the inferior-lateral border of the heart, so positive P waves in these leads suggest that the impulse was generated from the sinoatrial node

Question 18

Sinus rhythm with the rate between 60 and 100

Answer 18

Normal sinus rhythm

Question 19

Sinus rhythm with the rate greater than 100

Answer 19

Sinus tachycardia

Question 20

Sinus rhythm with the rate less than 60

Answer 20

Sinus bradycardia

Question 21

What does the electrical axis (of ECG events) represent?

Answer 21

The mean QRS vector =

• the summation of the amplitude and directionality of all the small vectors that make up ventricular depolarization.
• Since the left ventricle dominates ventricular depolarization, the mean QRS vector normally points inferiorly and to the patient’s left.

Question 22

Which leads are used to determine axis?

Answer 22

• First look at the QRS complexes in leads I and aVF.
• If the QRS complex is positive in lead I and negative in aVF, look at lead II.

Question 23

What is the axis?

• QRS complex is positive in lead I and aVF

Answer 23

Normal

Question 24

What is the axis?

QRS complex is positive in lead I, negative in aVF, and positive in lead II

Answer 24

Normal

Question 25

What is the axis?

QRS complex is positive in lead I, negative in aVF, and negative in lead II

Answer 25

Left-axis deviation

Question 26

What is the Axis?

QRS complex is negative in lead I and positive in aVF

Answer 26

Right-axis deviation

Question 27

What is the axis?

QRS complex is negative in lead I and aVF

Answer 27

Northwest axis (also called extreme right axis deviation or indeterminate)

Question 28

What is a normal PR interval?

Answer 28

• Between 0.12 seconds (three small boxes) and 0.2 seconds (five small boxes)

Question 29

What is the normal duration for a QRS complex?

Answer 29

• Less than 0.12 seconds (three small boxes)

Question 30

What is the equation for calculating the correct QT interval?

Answer 30

QTc = QT interval/square root of the RR interval (in seconds)

Question 31

Why is the QT interval corrected?

Answer 31

• The QT interval represents ventricular repolarization, which is dependent on the heart rate.
• With faster heart rates, the QT interval is shorter(and vice versa for slower heart rates)

Question 32

What constitutes a prolonged QTc interval?

Answer 32

Greater than 0.44 seconds

Question 33

What ECG changes can be seen in a myocardial infarction (MI)?

Answer 33

• ST segment elevation (although ST segment depression can be seen in nonST elevation MIs)
• T-wave inversion
• Q waves (must be in at least two contiguous leads)

Question 34

Which areas of the heart correspond to ECG changes in these leads?

II, III, aVF

Answer 34

Inferior: typically supplied by either the right coronary or circumflex arteries

Question 35

Which areas of the heart correspond to ECG changes in these leads?

V1-V6

Answer 35

Anterior: supplied by the left anterior descending artery

Question 36

Whic areas of the heart correspond to ECG changes in these leads?

I, aVL, V5, V6

Answer 36

Lateral: supplied by the circumflex artery