2.2.1 Electrocardiography

Question 1

Which leads are responsible for capturing the horizontal planes?

Answer 1

Pre-cordial

Question 2

79 y/0 F with severe dyspnea: note the tachycardia.

Describe the rate, rhythm, and axis? What could this patient be experiencing?

Answer 2

Rate: just under 150

Rhythm: Irregular rhythm

Axis: Right axis deviation

Representation of Atrial fibrillation

• almost always tachycardia
• w/ irregular rhythm

Question 3

In which lead, is the Q wave normally found?

Answer 3

AVR lead (210 degrees)

Question 4

What type of block?

Answer 4

Complete heart block/3rd degree

Question 5

How would infarction manifest itself on an EKG? Ischemia?

Answer 5

Infarction: ST segment elevation

Ischemia: ST segment depression

Question 6

Where does phase 2 of the cardiomyocyte AP show up on an EKG?

Answer 6

It forms the separation b/t the S and T wave

Question 7

What is happening in the heart during the QRS complex?

Answer 7

Ventricular depolarization (contraction)

Question 8

Altering phase 3 of the cardiomyocyte AP will affect what on an EKG?

Answer 8

Alter the shape of the T wave

Question 9

What type of axis deviation would be found in a patient that presented with the following EKG readings?

Answer 9

Normal mean electrical axis, two thumbs up

Question 10

Still looking at axis, a R wave that points up is considered what? downward?

Answer 10

Upward: positive

Downward: negative

Question 11

Which leads are responsible for catching the frontal plane?

Answer 11

Limb

Question 12

60 yF with chest pain

Answer 12

Infarction

Question 13

What type of AV block?

Answer 13

2nd degree AV block Mobitz type I

Question 14

What the three possible criteria to use when determining whether the patient has hypertrophy? Describe the sensitivity and specificity of these.

Answer 14

Romhilt Estes, Cornell, No name criteria

All poorly sensitive but very specific

Question 15

What type of axis deviation would be found in a patient that presented with the following EKG readings?

Answer 15

Right axis deviation

Question 16

Rapid review: What happens during phases 0-4 of a cardiac myocyte action potential?

Answer 16

Question 17

What is occuring in the heart during the P wave?

Answer 17

Atrial depolarization (contraction)

Question 18

What are the four types of AV block? What are their characteristics

Answer 18

Question 19

What is occurring in the cardiac tissue during the ST segment?

Answer 19

Ventricles are the plateau phase of depolarization (phase 2)

Question 20

What is happening in the heart during the T wave?

Answer 20

Ventricular repolarization (relaxation)

Question 21

What is this patient’s HR? What else do you notice about this EKG?

Answer 21

300/5 = 60

Lack of P wave (not SA node pacing). Could be AV nodal pacing (almost brachycardia)

Question 22

What type of axis deviation would be found in a patient that presented with the following EKG readings?

Answer 22

Extreme right axis deviation

Question 23

36 y/o F with syncopal episode

Describe rate, rhythm, axis, and hypertrophy.

Answer 23

Rate: Just under 60

Rhythm: Sinus (Lead I and II are good for finding p wave due to placement over atria)

Axis: Normal

Hypertrophy: present

Question 24

Describe the placement of the limb leads and the angles of the vectors that they detect?

Answer 24

Einthoven’s Triangle

Question 25

When analyzing axis, which leads are you looking at? What is considered normal?

Answer 25

Lead I and AVF; anything between 0 and 90 degrees

Question 26

Which leads are good for looking at ST elevation?

Answer 26

II, III, aVF

Question 27

What is the treatment for A fib/right axis deviation?

Answer 27

Control HR, consider anticoagulation (CHADS2) to reduce the risk of stoke/thromboembolism

Question 28

What are the 6 steps in the clinical approach to reading an EKG?

Answer 28

1. Rate
2. Rhythm
3. Axis
4. Intervals
5. Hypertrophy
6. Ischemia/Infarction

Question 29

What is occurring the cardiac tissue when the QRS complex begins?

Answer 29

Conduction through the His-Purkinje system and ventricular system

Question 30

When looking at rhythm, what is the first question to ask yourself?

Answer 30

Is it sinus or not? (presence of the P wave?)

Question 31

What is the Cornell calculation for ventricular hypertrophy?

Answer 31

R_AVL + S_V3 = 20 (in females)

R_AVL + S_V3 = 28 (in males)

Gender bias is due to the fact that female breast tissue doesn’t conduct electrical impulses as well as muscle

Question 32

Describe the four possible axial scenarios and the direction of the R wave in leads I and aVF.

Answer 32

Normal: positive R wave for both

Right axis deviation (R.A.D.): positive aVF and negative Lead I

Left axis deviation (L.A.D.): negative aVF and positive Lead I

Extreme R.A.D: negative aVF and Lead I (in healthy individual, possibly situs inversus)

Question 33

How does one determine the rate when looking at an EKG?

Answer 33

Each big box is 300.

So, find two consecutive R-R peaks and count the number of boxes between them. Then, take 300 and divided by the number of boxes that you just counted.

Question 34

What is the most common cause of L ventricular hypertrophy? What are some other possible causes?

Answer 34

Chronic HTN

Other causes: aortic stenosis, HOCM

Question 35

An obstruction (due to MI or surgical cut) of the left bundle branch will have what effect on the QRS complex?

Answer 35

Wider due to slower propogation through the ventricle

• Called a left bundle branch block

Question 36

What type of axis deviation would be found in a patient that presented with the following EKG readings?

Answer 36

Left axis deviation

Question 37

What is responsible for the P-R interval found on an EKG?

Answer 37

The pause in the AV node