Electrocardiography Flashcards
What is an ECG
a diagnostic tool used to measure the electrical activity of the heart, summation of activity, consisting of 10 leads minimum, recorded from electrodes on the body’s surface, produces 12 traces
What do leads AVF, AVR & AVL measure?
AVF- inferior regions such as feet
AVR-measure right side of heart through the right arm
AVL- measures left side of heart through left arm
What do leads i,ii & iii measure?
i- left side of heart (left arm to right arm)
ii-left leg to right arm
iii-left leg to left arm
What does lead V1,V2,V3,V4,V5 & V6 measure?
V1- 4th intercostal RSE (Rv and inv septum, anteroseptal surface V1-V3, red lead)
V2-4th intercostal space LSE (RV and septum, yellow lead)
V3- midway between 2&4th (records anterior wall of LV, green lead)
V4- 5th intercostal mid clavicle (v4-v6 measures anterolateral surfaces, v4 anterior wall of LV, brown lead)
V5-left ant axillia at v4 level (records lateral wall of LV, black lead)
V6- mid axillia (armpit) at V4 level (purple lead,
What is a bipolar lead?
A lead composed of two electrodes of opposite polarity is called bipolar lead, (lead i, ii, iii), recording from two different sites
What is a unipolar lead?
A lead composed of a single positive electrode and a reference point is a unipolar lead. (AVR, AVF,AVL and V leads)
How to prepare a patient for an ECG
Explain the procedure, and details (DOB, name & hospital number) and answer any questions, ensure the patient is relaxed and has a bare chest, clean the skin, shave the chest and remove oils. gently abrade, take off the top layer of dead skin
Danger’s of ECG
Results need to be reproducible
differently, if ECG is done differently the results will look different and interpretation will be different
Difference between diagnostic and monitor ECG
A diagnostic ECG consists of a minimum of 12 leads and a frequency between 0.05-150Hz, whereas a monitor ECG consists of 1-2 leads and has a frequency of 40Hz
Why a patient has been referred for an ECG
could be due to:
chest pain
acute MI
Pulmonary embolism
dizziness
arrhythmias
drug efficacy
pre-operation
What is a pulmonary embolism
The thrombus in lower limbs breaks off and gets stuck in a lung artery. Starts in a deep vein in the leg which travels to the lungs
What is syncope
someone coming in and out of consciousness
What is an arrythmia
any person not within sinus rhythm, e.g., fibrillation
How to prepare ECG equipment
make sure to calibrate the machine 1mv/10mm for every 1mv the pen will move 10mm, the paper speed should be 25mm/s, frequency response 0.05-150Hz
Paper speed importance
it can make a patient’s rhythm look different, can make them look bradycardic/ tachycardic
Calibration needs to change when?
if complexes are overlapping, makes ecg look taller or shorter
Frequency can be changes when?
eradicate electromagnetic waves, make sure to write on ECG change in settings
Lead I attachment & colour
Left arm attached to pos electrode (yellow)
right arm attached to neg electrode (red)
Lead II attachment & colour
the right arm is positive electrode
left foot is negative electrode (green)
lead III attachment & colour
Left arm to left foot
Left arm is negative and left foot is positive (green)
electrode attachment on right leg
The right leg is neutral, will improve the quality of the signal, remove artefacts
What is a differential amplifier
amplifies difference between inputs
aV stands for
Augmented voltage
How many traces produced by aV electrodes
6 traces produced by aV electrodes
Angle of louis
Fusion between the sternum and manubrium
breast tissue ecg
Lift breast tissue with the back of hand to place V4 & V5 and lower breast tissue back down, ECG cannot be done with a bra on
V4R
mirror position, applied on pediatrics, as heart is further right and swings round as it growsr
V7, V8 and V9
V7- left posterior axillary line
V8-mid scapular line (in line with V6)
V9- Paravertebral line (Same level as V6)
What plane do chest leads measure in?
the horizontal plane of the heart
What plane do limb leads measure in?
they observe the heart in the frontal plane
What is the Hexaxial reference system?
This system allows us to determine how the heart lies electrically, can give information about the axis of the heart, Lead i,ii,iii and AVF, AVR &AVR allows axis deviations to be spotted.
If the pen moves up signal moves towards an electrode
if the pen moves down signal moves away from the electrode
AVL is perpendicular to?
Lead II
Lead III is perpendicular to?
AVR
Lead I is perpendicular to?
AVF
What does the P wave represent?
Atrial depolarization
What does QRS wave represent?
Ventricular depolarization, no QRS in V2, RS complex instead
What does the T wave represent?
ventricular repolarization
What is AC mains?
How well the equipment is maintained, poorly maintained equipment masks the ability to interpret data, zigzag harsh lines
What is baseline wander
picked up on ECG, if patient has baggy lungs, or poor contact to electrodes, records rising and falling of chest
a wave on ecg
What is somatic
nervous activity picked up, the patient may be laying uncomfortably, interferes with ecg,
