Sinus Rhythm

Question 1

What are the changes from sinus rhythm on an ECG due to?

Answer 1

Pathology or the way we recorded it.

Question 2

How does your heart lie when you are born?

Answer 2

Lies vertical (tilts more as you grow).

Question 3

How does your heart lie when you are pregnant?

Answer 3

Lies more horizontally.

Question 4

What are some factors that cause an ECG to appear different?

Answer 4

-thickness of heart walls
-distance between heart and electrode (less distance- bigger waveforms)
-rate of depolarisation and repolarisation
-rate of travel

Question 5

What does the P wave represent?

Answer 5

P (pacemaker) cells that automatically depolarise.
Represent atrial depolarisation.

Question 6

What are the 2 components that a P wave show?

Answer 6

The right and left atrium depolarising (positive is right atrium depolarising and negative is the left).

Question 7

What is the normal length of a P wave?

Answer 7

No longer than 0.08 seconds, no taller than 0.23mV.

Question 8

Which lead would you expect to see P wave?

Answer 8

Lead 2.

Question 9

What can you conclude if P waves are in only one lead?

Answer 9

They are there! Need to look a the whole ECG.

Question 10

Does the PR interval have to be the same in every complex?

Answer 10

Yes.

Question 11

What is normal for the PR interval?

Answer 11

0.12-0.2 seconds.

Question 12

What can we suggest if the PR interval is too short?

Answer 12

Pathology- accessory pathway.

Question 13

What can we suggest if the PR interval is too long?

Answer 13

Pathology- block.

Question 14

What would you expect the PR interval to be like for someone tachycardic?

Answer 14

Expect to be shorter (needs to pump harder).

Question 15

What is the PR interval followed by?

Answer 15

A Q or R wave (whichever is the 1st positive or negative deflection).

Question 16

What does the PR interval represent?

Answer 16

The time travelled through the AV node (delay)- protects the ventricles as wants atria to contract to fill the ventricles.

Question 17

What is the only connection between the upper and lower chambers?

Answer 17

The AV node.

Question 18

What does the refractory period do?

Answer 18

Protects the ventricles (how long it takes to recover and slows down conduction).

Question 19

What does the QRS represent?

Answer 19

Ventricular depolarisation.

Question 20

How to recognise a Q wave?

Answer 20

Goes down the page.

Question 21

How to recognise an R wave?

Answer 21

Goes up the page.

Question 22

How to recognise an S wave?

Answer 22

Goes below the isoelectric line.

Question 23

What is the Q wave associated with?

Answer 23

Pathology (MI).

Question 24

What is R wave progression?

Answer 24

This is where the R wave increased in size from V1-6 (from right to left side).

Question 25

According to R wave progression, what should happen to V5 if it peaks in V4?

Answer 25

V5 and V6 should dip.

Question 26

Is there a Q wave seen in V1?

Answer 26

No.

Question 27

Which way does the heart depolarise?

Answer 27

Inside out (endo to epicardium).

Question 28

Why does the left side have more Q waves than right?

Answer 28

Left side is more dominant as there is more muscle so more electrical activity as the myocardium is thicker.

Question 29

Where in the QRS frontal axis is normal?

Answer 29

-30 to +90 degrees.

Question 30

Where is left axis deviation?

Answer 30

-45.

Question 31

Where is right axis deviation?

Answer 31

+100.

Question 32

Link between most and least activity in the leads?

Answer 32

Need to establish the lead with the most activity and the lead perpendicular to that will have the least activity.

Question 33

How do the limb leads view the heart?

Answer 33

In the frontal plane (how the heart is lying).

Question 34

What is the ST segment?

Answer 34

The J point to the beginning of the T wave.

Question 35

What is normal for an ST segment?

Answer 35

Don't measure the duration of the ST segment but should be within 1mm of the isoelectric line.

Question 36

What is the ST segment good for recognising?

Answer 36

Good marker for ischaemia (elevated or depressed).

Question 37

What is the J point?

Answer 37

The point after the S wave where it meets the isoelectric line.

Question 38

What does the QT interval represent?

Answer 38

The whole time from depolarisation to repolarisation.

Question 39

How do you measure the QT interval if there is no Q wave?

Answer 39

Measure from the R wave.

Question 40

When does the QT adjust?

Answer 40

When heart rate increases, diastole shrinks.

Question 41

What can we suggest if there is a long QT?

Answer 41

Prone to VT.

Question 42

What is normal for a QT interval?

Answer 42

0.42-0.45.

Question 43

What is Basset's formula for corrected QT?

Answer 43

QTc= QT/Sq root R-R (seconds).

Question 44

Which way does the heart repolarise?

Answer 44

From the outside in (epicardium to endocardium).

Question 45

What do T waves represent?

Answer 45

Ventricular repolarisation.

Question 46

If the T waves are symmetrical, is that normal or abnormal?

Answer 46

Abnormal (should have a slow ascend and a steeper descend).

Question 47

What is normal for a T wave?

Answer 47

Should be less than 2/3 size of the R wave.

Question 48

To calculate rate, how many seconds does one small square and one large square represent?

Answer 48

-small square= 0.04 -large square= 0.2

Question 49

How to calculate R-R interval?

Answer 49

Number of small squares x 0.04

Question 50

How to calculate HR from R-R interval?

Answer 50

60/ R-R interval (bpm).

Question 51

What is the criteria for sinus rhythm (P waves)?

Answer 51

-morphology has to be the same in one lead -must be present -morphology must be normal for the person and lead -1 P wave per QRS and come before QRS.

Question 52

What is the criteria for sinus rhythm (QRS)?

Answer 52

-must be typical for patient and lead -must be the same in a given lead

Question 53

What is the criteria for sinus rhythm (T waves)?

Answer 53

-asymmetrical -same polarity as QRS -less than 2/3 R wave

Question 54

What is sinus rhythm based on?

Answer 54

Criteria NOT patterns.