Topic 5 : Electrocardiographs

Question 1

What is an electrocardiograph?

Answer 1

The electrocardiogram (ECG) monitors heart rate, cardiac rhythm and axis deviation. ECGs record electrical activity of the heart, allowing any irregularity to be diagnosed.

Question 2

What is the difference between normal heart contractions and abnormal contractions that an electrocardiograph records?

Answer 2

Normal heart contraction requires normal electrical conduction of activating electrical impulses through cardiac muscle tissues. Abnormal or “skipped” contractions result from abnormal electrical activity.

Question 3

What is pulmonary circulation?

Answer 3

The process where deoxygenated blood enters the right side of the heart and is pumped to the lungs.

Question 4

What is systemic circulation?

Answer 4

The newly oxygenated blood enters the left side of the heart where it is pumped to the organs and tissues via systemic circulation

Question 5

What three reasons will you usually take an ECG?

Answer 5

• To diagnose an abnormal cardiac rhythm (arrhythmia) - To aid in the detection of an enlarged heart - To aid in the detection of electrolyte, systemic or metabolic disorders

Question 6

An ECG trace may taken to monitor a patient which:

Answer 6

• That is in shock - That has been seizuring - During and after surgery (for depth of anaesthesia as well as cardiac monitoring) - Preoperatively in older animals to detect cardiac abnormalities - To evaluate the effect of cardiac drugs - To monitor the heart during pericardiocentesis - As part of a series of ECGs to aid in the prognosis and diagnosis of cardiac disease

Question 7

How is the electronegativity recorded?

Answer 7

electroactivity is recorded on heat-sensitive paper and is called a “trace”.

Question 8

Define depolarisation

Answer 8

Depolarization: contraction of the myocardium

Question 9

Define repolarisation

Answer 9

Repolarization: relaxation of cells after depolarization

Question 10

Define systole: the ventricles contract

Answer 10

Systole: the ventricles contract

Question 11

Define diastole

Answer 11

diastole: the ventricles are filling

Question 12

Describe the contractions of the heart

Answer 12

Each contraction of the heart is preceded by an electrical wave front that stimulates the heart muscle to contract (systole) and then relax (diastole) in preparation of the next heat beat.

Question 13

What are the 3 parts of an ECG tracing

Answer 13

The parts are labelled P, QRS, and T

Question 14

What is the P wave of an ECG tracing?

Answer 14

P wave: ECG representation of the depolarisation of right and left atria.

Question 15

What is the QRS interval of an ECG tracing?

Answer 15

QRS interval: right and left ventricular depolarisation (normally the ventricular are activated simultaneously). During this phase the valves of the heart are closed.

Question 16

What is the T wave of an ECG tracing?

Answer 16

T Wave: ventricular repolarisation

Question 17

What is the function of leads on an ECG?

Answer 17

The different leads allow you to look at the heart from different angle

Question 18

What are the different angles on the ECG called?

Answer 18

Each angle is called a lead.

Question 19

How is each lead connected to the animal?

Answer 19

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

Question 20

How do you calibrate and set up an ECG machine?

Answer 20

• making sure it contains enough paper (you should always have spare paper on hand) - the pen is in the centre of the paper - the lead clips are clean - there is adequate amount of electrode gel available - the machine is earthed (Use a rubber mat, lambs’ wool / skin, wool rug, fibreglass will reduce interference)

Question 21

What are the three basic controls on an ECG for the trace?

Answer 21

1. The paper shred 2. Calibration setting 3. Filter

Question 22

What is the paper speed function on an ECG? And what is the general paper speed?

Answer 22

easiest to remember by thinking that the faster the paper speed the more spread out the heart beat is across the page, complexes are wider and easier to interpret. In general paper speed is either 50mm/sec or 25mm/sec. Faster speed gives an easier to study ECG.

Question 23

What is the function of calibration setting on an ECG?

Answer 23

sets the height of the complexes typically 1cm/m V

Question 24

What is the function of filter setting on an ECG?

Answer 24

– can help reduce the impact of artefacts on the recorded trace, but always have it turned off initially.

Question 25

What should an ECG be labelled with?

Answer 25

• The animal’s name
• Species
• Owner’s name
• Date

Question 26

Label the parts (P, QR and T) on a ECG tracing?

Answer 26