Interpreting ECG Flashcards
depolarisation
- na influx making membrane more +
repolarisation
- k efflux to decrease mp
deflection
- deviations from the isoelectric line (+ deflation = goes upwards, -ve deflection = downwards)
action propgoation
same as AP
exctiitioan -contration coupling
depolarisation wave c co ordained contraction of the atria and ventricles
exctiitioan -contration coupling
depolarisation wave c co ordained contraction of the atria and ventricles
cellular level
myocardial cells via gap junctions to the next cll so threshold reachAP fired influx of na+
tissue level
SAN atrial wall AVN (bottom left of the R A) slower rate b don’t want v to contract same rate as a b no filling of the v Bundle of His located in the ANNULAR FIBROSIS; so electrical activity spreads down the 2 … Bundle branches R and L so R bundle branch, and L bundle branch terminates at the Purkinje fibres where spreads depolarisation through the ventricles
annual fibrosis
- consists of 4 fibrous rings ( Fibrous ring of pulmonary valve / F r of aortic v/ right fibrous trigone/ left fibrous trigone ) - anchors myocardium and cardiac valves (just like how muscles are anchored by bones) - electrical insulator bw A and V b we don’t want chaotic movement of the e between them
Bundle of his
2 branches -R= carries impulses to R V - L= carries impulse to LV - work very fast so implies sent at the same rate c same contraction - terminate at the purkinjue fibres
why doesn’t AVN cause the rhythm
- SAN fires more rapidly so surpasses the other rhythms
firign rate of the conducting systems of the heart
SAN 60-100 time/min AVN 40-60/min LBB RBB - 20-40/min
whats an ECG ? a lead? an electrode? how many leads? how many views?
-measures changes in electrical potential produced by successive area of the myocardium during the cardiac cycle via a series of leads attached to the body - via of the heart / electrical capable that connects electrode to an ECG recorder - a conductive pad attached to skin and enables recording of electrical currents. - 10 leads, 12 views
COPD (large chest d air) and obesity (large chest ) how does this change to ECG recording
- e activity is altered be must travel through air/fat
what should you be aware of
when interpreting an ECG be aware of the ECG you’re thinking about - when describe the changes of e activity specificy the lead to specificy the view - lead 2 gives you really good view of P WAVE since It gives good view of the heart rate
P wave
-
1 wave?
1 wave - moe than 1 wave is a deflection so PQRST complex
electrodes
-10 { 4 limbs R arm L arm R L leg) - R leg no view of the heart it is just a grounding one , but you must put it on or the ECG looks weird - compare electrical activity of R L R L arm and leg) -preicordianl electrode = heart - called 12 leads be 12 views of the ehart
now we out
- R arm = R shoulder - R leg = bottom quadratic under the umbilicus ) - this is because you get eh same reading as the limb placement but less movement so less artefact - compare e activity over time 123
leads 123
123 bipolar ( have negative and positive end)
positive electrode
- if depolarisation current is going towards the positive electrode you get a upwards deflection -ifrepolaristoncurrent is going towards positive electrode you get downwards deflection
augmented limb lead
- no bipolar - one the leads is +avR ( R arm) -avL (left arm)+ -avF(F for left leg) + - avR (R values the average of the L arm and L leg) - avL (L arm is average of R arm and L leg -avF (L leg is average of R arm and L arm)
limb leads
6 view from the vertical plane from top to bottom
limb lead 2
RA and LL measures electrical difference between them and since the heart is diagonal its a straight line through to the inferior aspect of the heart
lateral
1 AVL
right side of heart
AVR
bottom
LL3 AVF LL2
Pericordinal / chest leads
view of the heart in a horizontal plane from front to back -unipoar -info about interventrial septum side -
deflection
-oblique deflection is smaller is not straight at you - if perpendicular straight line or nothing - going away = negative deflection
SAN
- ot detected
atrial depolarisation is
P wave (upwards b from leads 2, going towards the LL)
delay
don’t see it sicne its very small but we infer - but it is represented by a isoelectric line - f heart not contracting for long the AVN will be longer - prolonged P-R interval
as e goes into ventricles
- you get deflection b lots of cells in the ventriclestherfore large deflection ,
QRS complex
depolarisation of the ventricles lead 2
small squares 5 small squats make 1 large square
-0.04 sexonds - 0.2
P-R
3/4 small squares (
P wave
- atrial depolarisation ( positive deflection because the depolarisation is moving towards the positive electrode
Q wave
- SAN node - can be straight line or just downwards b the heart is a 3D model and so there’s bound to be deflection from a certain angle
R wave
- ventricular depolarisation - very high b ^^ of myocardial cells, the AP is moving through the bundle of his towards the apex of the heart hence the positive deflection as you’re moving towards the Lead 2
S wave
- AVN node inference - downwards again b heart 3D model there’ll be some deflection from an angle
T wave
- Ventricular repolarisation - still get a positive deflection because although its repolarising its moving towards the LLL wc is the positive electrode
where are the precordial leads placed and how many?
- 6 -
describe the leads and the view they allow
- vertical view (top to bottom of heart) -Right side of the heart avR - bottom view L2 avF L3 - lateral side/ left ventricle = L1 AVL
precordial leads HOW MANY? type of leads? placements
- 6 - unipolar - reading horizontal place allow front to back so look at walls -V1 = 4th intercostal right [antero-septal] -V2= 4th intercostal left [a-s] -V3 = inbetween V2 and V4[a-s] -V4 = 5th intercostal midcollar bone L[a-s] -V5 = 5th intercostal anterior axillary line -V6 = 5th intercostal midaxillary line
