12 Lead ECG theory Flashcards
What are the indications for electrocardiography?
-chest pain
-acute myocardial infarction
-pulmonary embolism
-dizziness/syncope
-arrythmias
-drug efficacy
-pre- op
What is and ECG?
its a representation of the summation of the heart’s electrical activity recorded from electrodes on the body surface.
What is the skin prep for an ECG?
-clean
-abrade (gently take away the top layer of the skin)
-no oils
-shave
What are three steps to prepare the patient for an ECG?
-explanation
-relaxation
-details (name, hospital number, DOB)
whats the difference between congential and acute heart disease?
congentail-born with it
acute-aqquired it over time
What is a diagnostic ECG?
-one you can interpret
-has to be 12 lead minimum
Who came up with ECG?
-A.D Waller 1887
-Einhoven 1908
-P, QRS, T
How to check machine safety?
check the labels on the machine to check its in date, check for visible damage.
what things do you need to prepare for the equiptment?
-paper speed
-calibration
-frequency response
-settings, operator dependent
What does the paper speed for an ECG need to be?
25mm/s
What is the correct callibration for an ECG?
-sensitivity is 10mm/mV
-the standard calibration signal measures 1mV over 10mm
(output over input)
What is the frequency respomse for an ECG?
0.05-150Hz
What does a monoriting ECG frequency go up to?
40Hz
What are the 4 types of lead systems?
-Bipolar
-Unipolar
-Limb leads
-Chest leads
What are the limb lead placements?
lead I-left arm to right arm
lead II - left leg to right arm
lead III- left leg to left arm
(top three leads are bipolar)
(bottom three are unipolar)
aVR- right arm
aVL-left arm
aVF- foot
What do bipolar leads measure?
amplifying the difference between two sites
what are the different colors for limb leads?
yellow -left arm
red-right arm
black-right foot
green- left foot
why dont we measure the right lead in a limb ECG?
beacause the right leg is neutral
What are the bipolar leads on a limb ECG?
lead I
lead II
Lead III
What are the unipolar leads on a limb ECG?
-lead aVR
-lead aVL
-lead aVF
Where are the chest leads/ precordial leads placed?
V1- 4th intercostal RSE
V2-4th intercostal LSE
V3-midway V2-V4
V4- 5th intercostal mid clavicular
V5-left ant axilla at the level of V4
V6-mid axilla at the level of V4
What does RSE and Lse mean?
Right sternal edge
left sternal edge
what does axilla mean?
Armpit
where is the acrominoclavicular joint?
end of right clavicle,helps us determine left anterior axilla
What are the colours for the precordial leads?
V1-red
V2- yellow
V3- green
V4-Brown
V5-black
V6-purple
What planes do limb leads look at the heart in?
frontal plane
What planes do chest leads look at the heart in?
horizontal plane
What surface are leads II,III and aVF on?
inferior surface
what surface are leads I and aVL on?
high lateral surface
What surface are leads V1- V3 on?
anteroseptal surface
What surface are leads V4-V6 on?
anterolateral surface
What pole is the left arm?
positive pole
What is the hexaxial reference system?
allows us to determine how the heart is lying electrically not physically
-determines the hearts electrical axis in the frontal plane
what do p waves represent?
atrial depolarisation
what do QRS complexes represent?
ventricular depolarisation
What do T waves represent?
ventricular repolarisation
What are some troubleshooting factors?
-gain
-sensitivity and paper speed
-artefact
-baseline wander
-muscle tremor
-AC interference
-comments
When do AC mains occur?
-poor maintenance equiptment
What causes a baseline wander?
-someone with chronic obstructive airway disease
-poor contact with electrodes
-cables being knocked
What causes somatic?
-shivering
-nervous
-fidgeting
-not laying comfortably
-these muscles will interfere with the ECG
what is the equation for large square rate of an ECG?
rate= 300/ R-R intervals in large squares
What is the equation for small square rate of an ECG?
rate= 1500/ R-R intervals in small squares
Whats the equation for the R wave method?
Number of R waves in a rhythm strip x 6
Name the perpendicular leads
I and AVF
II and AVL
III and AVR
