ECG Flashcards
An ECG is?
recording of changes in potential, by electrodes on the body surface to allow measurement of heart electrical activity
what information does an ECG provide?
cardiac rate and rhythm, chamber size, electrical axis of heart
magnitude of charge vector determined by ____
mass of cardiac muscle
direction of charge vector determined by _____
activity of the heart at an instant in time
upwards deflection on an ECG is caused by
depolarisation moving towards positive recording electrode
downwards deflection on an ECG is caused by
depolarisation moving away from positive recording electrode
Lead I is set up as
RA + to LA -
lead II is set up as
RA - to LL +
Lead III set up as
LA - to LL +
what plane do leads I-III and aVF, aVR and aVL look at
frontal coronal
what plane do leads V1-6 look at
transverse
what causes the upward P wave on lead II
atrial depolarisation spreading left
how long does the QRS complex normally last
<100ms
what causes Q on lead II
ventricular depolarisation occurs in IV septum and spreads left to right
what causes R
main walls of ventricles depolarise
What causes S
upper walls of ventricles depolarise
what causes T
ventricular repolarisation
what is goldbergers method
use of two negative limb leads to create reference point in the middle
how long does P wave last
0.08-0.1s
how long does QRS last
<0.1s
how long is the PR interval and why is it that long
0.12-0.2s, largely AV node delay
how long is the time on a small square of ECG trace?
0.04s
how do you calculate HR from ECG
300/number of large squares between beats
what lead is the rhythm strip
usually lead II
what leads pick up inferior heart abnormalities
Lead II, Lead III, aVF
what leads pick up coronal heart abnormalities
lead I and aVL
what may a normal ECG fail to pick up
stable angina
MI
intermittent rhythm disturbance
how do you work out HR from ECG with irregular QRS
count number of QRS in 30 large squares and multiply by 10
what would left axis deviation look like on ECG
inversion of aVF
What would right axis deviation look like on ECG
inversion of lead I
