EKG - The Basics

Question 1

One small box = ___ seconds

Answer 1

0.04 sec (40 msec)

Question 2

Five small boxes = 1 BIG box = ___ seconds

Answer 2

0.2 sec (200 msec)

Question 3

Five BIX boxes = ___ seconds

Answer 3

1 seconds (5 x 0.2 sec)

Question 4

How many limb leads are there?`

Answer 4

6 limb leads

Question 5

What are the three standard limb leads?

Answer 5

Lead I, II, III

Question 6

What are the three augmented limb leads?

Answer 6

aVL, aVR, aVF

Question 7

What are the inferior leads?

Answer 7

II, III, aVF

Question 8

What are the left lateral leads?

Answer 8

I, aVL, V5, V6 (they view the left lateral wall of heart)

Question 9

What are the six precordial leads?

Answer 9

V1 - V6

Question 10

What are the anterior leads?

Answer 10

V2, V3, V4

Question 11

What are the R ventricular leads?

Answer 11

aVR, V1

Question 12

Match each lead to its category:
I                     
II                    
III            
aVL                 Anterior leads
aVR                 Inferior leads
aVF                 Left lateral leads
V1                    R ventricular leads
V2
V3
V4
V5
V6

Answer 12

Inferior: II, III, aVF
Anterior: V2, V3, V4
Left lateral: I, aVL (L for lateral), V5, V6
R ventricular: aVR (R for right), V1

Question 13

Atrial depolarization begins where?

Answer 13

Sinus node, high up in the top of the R atrium

Question 14

Which atrium depolarizes first?

Answer 14

R atrium, then the L atrium

Question 15

The height of one small square = __ mm and __ mV

Answer 15

One small square tall = 1 mm = 0.1 mV

Question 16

What is the normal length of PR interval

Answer 16

0.12 - 0.2 seconds (max 1 big box / 5 small boxes)

Question 17

What does a long PR interval ( > 1 big box 0.2 sec) ?

Answer 17

some degree of A-V blocks (1st; 2nd - type 1 Wenke or type 2 mobitz; 3rd-aka complete AV dissociation)

Question 18

What is the difference between the types of AV blocks

Answer 18

1st degree: constant prolonged PR interval. Is > 0.2 sec but is fixed

2nd degree:

• — Type I aka Wenkebach: increasingly long PRi until non-conducted P wave occurs (QRS gets dropped )
• — Type II aka Mobitz: again fixed prolonged PRi, plus nonconducted P waves (QRS’s getting dropped)

3rd degree: complete A-V dissociation

Question 19

What is the normal Q wave amplitude?

Answer 19

no greater than 0.1 mV ( 1 mm = 1 small box)

Question 20

What is R wave progression?

Answer 20

increasing R wave amplitude from V1 to V5 (moving from right to left in the precordial leads) - note sometimes R wave in V6 is a little smaller than V5

Question 21

What is a transition zone? Where is the normal transition zone?

Answer 21

Where the QRS goes from being predominantly negative to predominantly positive.

Normal transition zone = at leads V3 and V4

Question 22

What is the amplitude of QRS so much greater than that of the P wave?

Answer 22

Because the ventricles have so much more muscle mass than do the atria, and can generate a much greater electrical potential.

Question 23

What is a normal QRS interval duration?

Answer 23

0.06 to 0.1 seconds ( 1 - 2.5 small boxes, max half of a big box)

Question 24

What does a mildly long QRS (0.1 - 0.12 s) indicate?

Answer 24

Incomplete RBBB or LBBB; nonspecific intraventricular conduction delay (IVCD), or L anterior or posterior fascicular block

Question 25

What does a VERY long QRS ( > 0.12 sec) indicate?

Answer 25

Complete RBBB or LBBB; nonspecific IVCD; ectopic rhythms originating in the ventricles

Question 26

QT interval (beginning of Q to end of T wave) normal duration =

Answer 26

< 0.44 sec (slightly more than 2 big boxes)

* note QT is heart rate dependent, so QTc is corrected for HR)

Question 27

Causes of long QT (> 0.44 s) are…

Answer 27

Drugs (TCA, phenothiazines)
Electrolytes (LOW K+, Mg+, Ca+)
CNS dz (arachnoid hemorrhage, stroke, trauma
Hereditary LQTS (Romano-Ward syndrome)
Coronary dz (some post-MI pts)

Question 28

What is the normal range of axis?

Answer 28

-30 to + 90 degrees)

Question 29

On the circle, what degrees is aVL at? …aVF? …aVR?

Answer 29

aVL = -30 degrees
aVF = + 90 degrees (straight down)
aVR = - 150 degrees

Question 30

P wave is usually (positive or negative) in the L lateral and inferior leads?

Answer 30

P wave is usually POSITIVE in the L lateral (I, aVL, V5, V6) and inferior (II, III, aVF) leads

Question 31

P wave is often biphasic in which two leads?

Answer 31

P wave is usually biphasic in III and V1

Question 32

P wave is usually most positive in ___ lead, and most negative in ___ lead.

Answer 32

Most positive in Lead II. Most negative in Lead aVR.

Question 33

T waves are variable, but are usually positive in leads with tall ___ waves.

Answer 33

T waves are usually positive in leads with tall R waves.