Electrocardiography

Question 1

Hypertrophic Obstructive Cardiomyopathy - what decreases and increases the sound of the murmur

Answer 1

It is counterintuitive as an increase in venous return lowers the sound of the murmur (from squatting to standing up) and a decrease in venous return increases the sound of the murmur in HOCD

Question 2

What does EKG look at

Answer 2

Records the depolarization of cardiomyocytes from 12 different angles

Question 3

Why dont we see repolarization of the atria on EKG

Answer 3

It is obscurred by the ventricular depolarization QRS complex

Question 4

What represent the RT complex on EKG

Answer 4

Phase 2 of the ventricular contraction which basically consist of no change in the action potential

Question 5

What are the 2 planes an EKG measures voltage to

Answer 5

Vertical and horizonatal plane, the 6 leads he showed us meaures in the horizontal plane

Question 6

What are the limb leads

Answer 6

No sensor on the right leg

Question 7

Summary of the EKG

Answer 7

Question 8

How do you define the beginning of QRS segment in abnormal EKG

Answer 8

The first negative to resting potential is defined as the Q point

Question 9

What is J point

Answer 9

Right after S point

Question 10

How does ST change in ischemia and infarction

Answer 10

Ischemia cause ST segment depression, infarction causes ST segment elevation

Question 11

What are the first few things you look at in an EKG

Answer 11

1. Rate: 300/ R-R interval (big boxes)
2. Rythm: sinus is normal, anything other than that can be afib or some kind of heart block
3. Axis: he said look at 1,2 and 3 electrodes in the frontal plane - the slide said right or left axis deviation
4. Interval: we look at PR interval, QRS interval and QT interval (200, 120, 450 milliseconds)
5. Hypertrophy: left ventricle hypertrophy, the QRS voltage would be higher. He also mentioned the cornel criteria
6. Ischemia/Infarction: Previous and acute infarctions

Question 12

How do you look at the axis

Answer 12

He said here that we look at I and aVF. For these 2 the QRS have to be positive in I and also in aVF. This is called the 2 thumbs up sign.

When he said positive he meant the total area under the curve in the QRS complex has to be positive.

Clinically this means that most of the myocardial mass depolarizes in lead I and in aVF. Anything between aVF and I is normal. Clinically anything between aVF and aVL is normal. This is referred as being in “the normal quadrant”

Question 13

Answer 13

Sum of the vector has to be between I and aVF

Question 14

How do you measure hypertrophy on EKG

Answer 14

You measure the height on your QRS complex

Question 15

What are the characteristics of afib

Answer 15

1. Tachycardia
2. Not in rythym, R to R dont have equal spacing
3. Atrial depolarization waves are not recorded since it is in afib, fibrillation waves are not usually strong

Question 16

What is the total time that EKG runs for

Answer 16

6 seconds

Question 17

How do you find the heart rate in afib

Answer 17

Count all of the R waves and multiply it by 6 (know why)

Question 18

What kind of deviation is in afib

Answer 18

Right axis deviation

Question 19

What are the main causes of afib

Answer 19

Long term hypertension as the atria are stretched and are more prone to go into afib

Question 20

Describe the right axis and left axis deviation

Answer 20

Right axis deviation - Lead I is negative, aVF is positive

Left axis deviation is the opposite - aVF is negative and I is positive

Question 21

What happens in I negative and AVF negative

Answer 21

Extreme right axis deviation, happens in patient with situs inverses

Question 22

What congential heart disease show right axis deviation

Answer 22

Tetralogy of Fallot and Eisenmenger complex

Question 23

How do you check for hypertrophy on EKG

Answer 23

This is the Cornell criteria

1. Look at the R wave on aVL
2. Look at the S wave on V3

For males normal goes up to 28 boxes and for female it goes up to 20 boxes on EKG (in vertical axis).

You check the height of the QRS complex on

When you have left ventricular hypertrophy you have more myocardial mass which causes higher potential

Question 24

What is this person having

Answer 24

Notice that there is ST elevation in II, III and aVF. This means that this person is having infarction. Since II, III and aVF runs through the right ventricle according to the axis, this person is having right ventricle infarction, so this person may have a thrombus in the right coronary artery.

Also notice that there is sometimes P wave in the bottom strip but no QRS wave which means there is an AV nodal block which causes PR interval change

Question 25

Types of different blocks

Answer 25

Need to know how to pick them up on an EKG

1st degree AB block: PR interval that is longer than normal, longer than 0.2 seconds

2nd degree AV block, Mobitz I: prolonging PR interval, PR interval gets longer every time

2nd degree, Mobitz II: normal stable PR interval which then just drops, it does not prolong you just get a drop in the PR segment

3rd degree: total heart block, makes no rythym