T5: ECG

Question 1

What does an electrocardiograph do?

Answer 1

• Monitors heart rate, cardiac rhythym and axis deviation.
• Records electrical activity of the heart.

Question 2

What does a normal heart contraction require?

Answer 2

Normal electrical conduction of activating electrical impulses through cardiac muscle tissue.

Question 3

What are ECGs taken for?

Answer 3

• Diagnosing cardiac diseases and abnormal cardiac rhythym (arrythmia)
• Aids in detection of enlaged heart
• Aids in detection of electrolyte, systemic or metabolic disorders
• Anaesthetic monitoring
• Useful in cardiac arrest cases and CPR
• Useful in diagnosing ventricular fibrillation

Question 4

Where in the heart does deoxygenated blood enter and where does it go?

Answer 4

Right side of heart.

Pumped to lungs.

Question 5

Where in the heart does oxygenated blood enter and where does it go?

Answer 5

Comes from the lungs and enters left side of heart.

Pumped to the body.

Question 6

What is a trace?

Answer 6

The recorded electroactivity on heat sensitive paper

Question 7

What does an ECG represent?

Answer 7

Amplitude and duration of electical activity

Question 8

What happens in each heart contraction?

Answer 8

Each contraction of the heartis preceded by an electrical wave font that stimulates the heart to contract and relax in preperation for next heart beat.

Question 9

What is Depolarization?

Answer 9

Contraction of the myocardium

Question 10

What is Repolarization?

Answer 10

Relaxation of cells after depolarization

Question 11

What is systole?

Answer 11

Contraction of the ventricals

Question 12

What is diastole?

Answer 12

The filling of ventricles (relax)

Question 13

What are the parts to an ECG?

Answer 13

1. P Wave
2. QRS Interval
3. ST/T wave
4. PR interval
5. QRS Duration
6. QT Interval
7. RR Interval
8. PP interval

Question 14

Attempt to draw a typical ECG printout.

Answer 14

Question 15

What does each ECG lead have?

Answer 15

Each lead has a positive and negative pole which is attached to the skin of the animal and can be used to measure the spread of the eclectrical activity within the heart.

Different leads allow you to look at the heart from different angles. Each angle is called a lead.

Question 16

Describe Alligator Clips

Answer 16

• Good for once off ECGs
• Clips should be placed on loose folds of skin at the elbows and knees.
• Requires a conducting medium (eg spirit) just sufficient enough to wet clip and hair through skin.

Question 17

Describe ECG pads

Answer 17

• Good for lengthy ECGs eg during surgery
• Can be taped to patient’s feet to provide a ore reliable contact with the skin.
• Gel is required - some pads come with gel

Question 18

How do you read an ECG Strip?

Answer 18

• ECG paper is a grid where time is measured along the horizontal axis
• Each sml sq is 1mm in length and represents 0.04 secs
• Each lrg sq is 5mm in length and represents 0.2 secs
• Voltage is measured along the vertical axis
• 10mm is equal to 1mV in voltage

Question 19

How do you measure the heart rate on ECG paper?

Answer 19

• ECG paper moves at a standardized 25mm/sec.
• Vertical lines can be used to measure time.
• There is a 0.20 sec between 2 of the large lines.
• ECG paper usually has special markings every 3 seconds

Question 20

What should you check before doing an ECG?

Answer 20

• Machine contains enough paper
• Pen is in centre of paper
• Lead clips are clean
• Aqaquete amount of elctrode gel available
• Machine is earthed

Question 21

What are the 3 basic controls on an ECG machine?

Answer 21

1. Paper speed: faster the paper speed the more spread out the heart beat is across page
2. Calibration settings: sets the height of the complexes typically Icm/mV
3. Filter: can help reduce the impact of artefacts on the recorded trace, but always have it turned off initially.

Question 22

How would you position a dog and a cat for an ECG reading?

Answer 22

Dog: right lateral recumbancy

Cat: sternal recumbancy

Question 23

Why do you not want to sedate an animal for an ECG reading?

Answer 23

Sedation, esp with alpha 2 agonists, may alter cardiac rythym

Question 24

What 4 questions should you ask when trying todetermine if a rhythm is normal or abnormal ?

Answer 24

1. Is there a P for every QRS?
2. Is there a QRS for every P?
3. Are the Ps and QRSs consistently and reasonably related?
4. Are the Ps and QRSs all the same?

Question 25

**What does it mean if you do not have a P wave before a QRS complex?**

Answer 25

Ventricals have depolarized without preceeding depolarization of the atria

Question 26

**What can cause the absence of a P wave before a QRS complex?**

Answer 26

1. Ventricular depolarization 2. Junctional depolarization 3. Atrial standstill 4. A-fib 5. Sinus arrest with escape complexes

Question 27

**What is A-fib?**

Answer 27

When the atria have random and irregular depolarization usually caused by enlarged atria. Won't see P waves, oscillating baseline but normal ventricular depolarization.

Question 28

**What will atrial standstill look like and what would youthink if you saw it**

Answer 28

Will be no P waves at all because the atria are completley inactive. Always think high K.

Question 29

**What does it mean if there is a P wave but no QRS to follow?**

Answer 29

AV block

Question 30

**What is it called when there is not a consistent relationship between P waves and QRS complexes?**

Answer 30

Atrioventricular dissociation

Question 31

**What is it called if there is variation in P wave aplitude?**

Answer 31

Wandering pacemaker. Can be normal in dogs.

Question 32

**Most common irregularly irregular heart rhythm?**

Answer 32

A-fib

Question 33

**Normal heart rate for cat and dog and rabbit?**

Answer 33

Dog: 70-180bpm depends on breed Cat: 140-200bpm Rabbit: 198-330bpm

Question 34

**What does the P wave of an ECG represent?**

Answer 34

Depolarisation of R & L atria

Question 35

**What does the QRS interval of an ECG trace represent?**

Answer 35

R & L ventricular depolarisation. Durig this phase, valves of heart are closed

Question 36

**What does the ST/T wave of an ECG trace represent?**

Answer 36

ventricular repolarisation

Question 37

**What does the PR interval of an ECG trace represent?**

Answer 37

time interval from onset of atrial depolarisation (P wave) to onset of ventricular depolarisation (QRS complex)

Question 38

**What does the QRS duration of an ECG trace represent?**

Answer 38

duration of ventricular muscle depolarisation

Question 39

**What does the QT interval of an ECG trace represent?**

Answer 39

duration of ventricular depolarisation and repolarisation

Question 40

**What does the RR interval of an ECG trace represent?**

Answer 40

duration of ventricular cardiac cycle (indicator of ventricular rate)

Question 41

**What does the PP interval of an ECG trace represent?**

Answer 41

duration of atrial cycle (indicator of atrial rate)