EKG

Question 1

What is a dipole?

Answer 1

A positive and negative charge separated by small distance which generated local current flow and electrical field

Question 2

Can dipoles summate?

Answer 2

Yes, if they are close together in space and time

Question 3

What is a vector?

Answer 3

Physical quantities with magnitude and direction represented by arrows

Question 4

Dipoles summate into _____

Answer 4

Cardiac vectors

Question 5

Is an EKG a record of a single action potential in a single cell?

Answer 5

NO

Question 6

What do EKGs record?

Answer 6

The overall spread of activity through the heart during depolarization and repolarization
(Only the electrical activity that travels through body fluids and reaches the body surface is recorded)

Question 7

WHat plane of the heart do the limb leads measure

Answer 7

Frontal plane

Question 8

What plane of the heart do the augmented unipolar leads measure

Answer 8

Frontal

Question 9

Are the limb leads bipolar or unipolar

Answer 9

Bipolar

Question 10

What plane of the heart do the chest leads measure

Answer 10

Transverse

Question 11

When you are looking at an EKG recording, what is the line called that separates the tracing of separate leads

Answer 11

Switching artifact

Question 12

What information can be obtained from an EKG?

Answer 12

Pattern and frequency of events (rate and rhythm)

Conduction time

Axis determination (direction of depolarization)

Size of heart chamber

Question 13

Can you make diagnoses by looking at an EKG?

Answer 13

No it is dangerous to do so

Question 14

Can you see on an EKG the depolarisationof the SA node?

Answer 14

No, it is too small. The first uptick on the EKG is showing the depolarization of both ventricles

Question 15

What two events are recorded during the QRS complex?

Answer 15

Repolarizatino of the atria as well as the massive depolarization of the ventricles

Question 16

What does the t wave reflect

Answer 16

The repolarization of the ventricles

Question 17

What does the PR segment represent?

Answer 17

The AV node delay

Question 18

What does the TP interval represent?

Answer 18

The time during which the ventricles are relaxed and filling

Question 19

What does the ST segment represent?

Answer 19

Time during which ventricles are contracting and emptying

Question 20

What is a segment?

Answer 20

An isoelectric line on the EKG, no waves. (Flat part at “0”)

Question 21

What is an interval?

Answer 21

PArt of the line that contains a segment and a wave

Question 22

What is a wave

Answer 22

An actual deflection from “0”

Question 23

How many waves are in the QRS complex?

Answer 23

3

The q and S waves are negative deflections

Question 24

What does the T wave reperesent ?

Answer 24

Repolarization of both ventricles

Question 25

Why is the T wave an upward deflection?

Answer 25

Because the epicardium actually has a shorter plateau phase, and so it actually repolarizes first, followed by the middle and endocardium. This causes the repolarization to actually flow from out to in, and the electrode senses it as moving AWAY from it. (Double negative appearing as a positive deflection )

Question 26

What is a U wave?!

Answer 26

A wave that may appear after the T wave that reperesents repolarization of the papillary muscles

Question 27

When would you observe a U wave?

Answer 27

Only during pathology: Hypokalemia Hypercalemia Thyrotoxicosis

Question 28

What do we use the PR segment for

Answer 28

As a baseline to evaluate the ST segment displacement

Question 29

What is the PR segment

Answer 29

the Isoelectric period between the end of the P wave and the beginning of QRS complex

Question 30

What is the ST segment?

Answer 30

The period between the completion of ventricular depolarizaon and beginning of ventricular repolarizaion

Question 31

What does the ST segment correspond to?

Answer 31

The plateau of the ventricular action potential

Question 32

The ST segment is isoelecrtic and corresponds to the plateau of the ventricular action potential. Does this mean that the ventricles are at rest?

Answer 32

No

Question 33

What does the PR interval represent?

Answer 33

The time for atrial depolarization and the AV node delay. | SO basically the conduction fo the impulse form the upper part of the atrium to the ventricles

Question 34

What is the normal value of the PR interval?

Answer 34

About .12-.20 sec or about ONE LARGE BOX**

Question 35

If the PR interval is longer than one big box, what can you suspect?

Answer 35

There’s some sort of block

Question 36

What does the QT interval represent?

Answer 36

Ventricular depolarization and repolarization (the entire electrical conductivity of the ventricles)

Question 37

What does the QT interval approximate?

Answer 37

The time of a ventricular action potential?

Question 38

Where on the EKG strip is the QT interval?

Answer 38

From the onset of the QRS complex to the end of the T wave

Question 39

Which line/segment/interval denotes the electric systole of the heart?

Answer 39

The QT interval

Question 40

What does the length of the QT interval depend on?

Answer 40

Heart rate

Question 41

If the QT interval depends on the the heart rate, how can we tell if it is normal?

Answer 41

We mathematically correct it comparing it to heart rate. (Corrected QT known as QTc)

Question 42

What would we use RR interval or PP interval for?

Answer 42

To calculate heart rate

Question 43

If we give a pt a drug that blocks the L-type calcium channels and shortens the duration of the plateau phase, which part of the EKG will be shortened?

Answer 43

The ST segment !!*****

Question 44

How many small boxes equal one second on an EKG?

Answer 44

25

Question 45

wht length of time does ONE SMALL box represent?

Answer 45

.04 seconds

Question 46

What length of time does one BIG box (5 smalls) represents

Answer 46

.2 seconds

Question 47

How many mV does one small box represent (on the Y Axis)

Answer 47

0.1mV

Question 48

What is the proper method to determine heart rate with an EKG>

Answer 48

Beats per 6 seconds (30 Large boxes) x10

Question 49

WHat is the “quick” estimation method to determine heart rate with an EKG?

Answer 49

HR=300/# large squares per cycle | In 60 seconds you would have 300 large boxes

Question 50

What is the net vector?

Answer 50

Sum of the positive and negative deflections of the waveform

Question 51

Which vector do we use to determine the net vector?

Answer 51

The QRS net vector

Question 52

What is meant by vector analysis?

Answer 52

Determining the mean axis of depolarization of ventricles

Question 53

Why do we care about the mean axis of ventricular depolarization?

Answer 53

It is used to obtain information about the conduction pathway and anatomical abnormalities

Question 54

What is the normal range of the mean QRS axis?

Answer 54

Between 0 and +90*

Question 55

What is a mean axis deviation”?

Answer 55

Value outside of the normal range (normal is 0 to +90*)

Question 56

What does is it mean when the mean QRS axis is more negative than 0 degrees?

Answer 56

Left axis deviation

Question 57

What does it mean when the mean QRS axis is more positive than +90*

Answer 57

Right axis deviation

Question 58

What are common causes for Left Axis deviation?

Answer 58

You are having MORE current coming from the Left side of the heart: 1. ) LV hypertrophy 2. )Obesity 3. ) Pregnancy 4. ) RV infarct

Question 59

What are some common causes for Right Axis deviation?

Answer 59

1. )RV hypertrophy 2. ) LV infarct 3. ) Tall, thin body type

Question 60

Which side of the upside down triangle is lead II and which is lead III

Answer 60

Lead II on the left Lead III on the right (0 is the middle of the side of the triangle, and the bottom point of the triangle is + for both leads)