Topic 5 : Electrocardiographs Flashcards
What is an electrocardiograph?
The electrocardiogram (ECG) monitors heart rate, cardiac rhythm and axis deviation. ECGs record electrical activity of the heart, allowing any irregularity to be diagnosed.
What is the difference between normal heart contractions and abnormal contractions that an electrocardiograph records?
Normal heart contraction requires normal electrical conduction of activating electrical impulses through cardiac muscle tissues. Abnormal or “skipped” contractions result from abnormal electrical activity.
What is pulmonary circulation?
The process where deoxygenated blood enters the right side of the heart and is pumped to the lungs.
What is systemic circulation?
The newly oxygenated blood enters the left side of the heart where it is pumped to the organs and tissues via systemic circulation
What three reasons will you usually take an ECG?
- 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
An ECG trace may taken to monitor a patient which:
- 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
How is the electronegativity recorded?
electroactivity is recorded on heat-sensitive paper and is called a “trace”.
Define depolarisation
Depolarization: contraction of the myocardium
Define repolarisation
Repolarization: relaxation of cells after depolarization
Define systole: the ventricles contract
Systole: the ventricles contract
Define diastole
diastole: the ventricles are filling
Describe the contractions of the heart
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.
What are the 3 parts of an ECG tracing
The parts are labelled P, QRS, and T
What is the P wave of an ECG tracing?
P wave: ECG representation of the depolarisation of right and left atria.
What is the QRS interval of an ECG tracing?
QRS interval: right and left ventricular depolarisation (normally the ventricular are activated simultaneously). During this phase the valves of the heart are closed.
What is the T wave of an ECG tracing?
T Wave: ventricular repolarisation
What is the function of leads on an ECG?
The different leads allow you to look at the heart from different angle
What are the different angles on the ECG called?
Each angle is called a lead.
How is each lead connected to the animal?
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.
How do you calibrate and set up an ECG machine?
- 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)
What are the three basic controls on an ECG for the trace?
- The paper shred 2. Calibration setting 3. Filter
What is the paper speed function on an ECG? And what is the general paper speed?
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.
What is the function of calibration setting on an ECG?
sets the height of the complexes typically 1cm/m V
What is the function of filter setting on an ECG?
– can help reduce the impact of artefacts on the recorded trace, but always have it turned off initially.
What should an ECG be labelled with?
- The animal’s name
- Species
- Owner’s name
- Date
Label the parts (P, QR and T) on a ECG tracing?
