ECG Flashcards
Where are leads attached to?
Left leg, left arm, right arm
What shape does this form? What name is given to the sides of the triangle?
Standard Limb leads
I,II,III
Describe the Standard Limb leads
I= right arm to left arm
II= left leg to right arm
III= left leg to left arm
(i.e. looking from the left leg(+ve) towards the right arm (-ve)
What plane do these allow us to see in?
Frontal plane
What other plane can we analyse?
The Transverse plane
How can we analyse the Horizontal Plane?
Using the precordial probes (V1-V6)
How do the readings on the precordial leads vary?
V1= very negative= depolarisation travelling away v3-v4 = in the middle V6= very positive= depolarisation approaching
Which sll shows the strongest R wave and why?
SLL II shows the strongest because it is on the axis of the approaching depolarisation.
Why are there three parts to the QRS complex?
Q= depolarisation left to right of interventricular septum. R= cumulative depolarisation of bulk of the ventricles from endocardium to epicardium. resultant vector= towards apex of heart S= depolarisation of upper part of the interventricular septum.
What forms the P wave?
Atrial depolarisation
What forms the QRS wave?
Ventricular Depolarisation
What is the T wave?
Ventricular Repolarisation
Why is the T wave positive?
Because it is repolarisation travelling away from the electrode- so the remote electrode becomes more negative- so the reference is positive.
Which SLL shows the weakest R wave and when might this not be the case?
SLL1 as it is perpendicular to the depolarisation
But if the heart is deviated to the left then SLL 1 will show the strongest signal.
Why does the plateau not show up?
Because the ECG can only pick up rapid changes
Why can you not see atrial repolarisation?
Because this overlaps with ventricular depolarisation which is a much bigger signal so it occludes the atrial repolarisation.
What is the PR interval?
Time between the start of atrial depolarisation and the start of ventricular depolarisation= 0.12-0.2 secs
What is the time taken for QRS complex?
around 0.08 seconds shouldn’t be greater than 0.12secs
What is the QT interval?
Complete time for ventricle to depolarise and repolarise. Varies with HR but should be 0.42 at 60bpm.
What is SINUS RHYTHM?
When every QRS is preceded by a P wave.
Define Tachycardia and Bradycardia
Tachycardia= HR over 100bpm (at rest) Bradycardia= HR under 60 bpm
Which leads allow us to read in the frontal plane?
SLL and Augmented Limb Leads
Define Augmented Limb Leads
These are stretching from one SLL to the middle of the other two- so give a reference with respect to both of the other SLL.
aVR= from right arm to mid SLL 111
aVL= from left arm to mid SLL11
aVF= from left foot to mid SL1
Explain the concept of a rhythm strip and what we can read from it?
Should run at 25mm/sec and each big square = 0.2 sec= 5mm
So if we the number of R-R in 30 squares (6 secs)
HR = R-R waves in 6 secs x 10
Should be around 60-100 bpm
What condition is related to the term STEMI?
Myocardial Infarction
A STEMI= st elevated MI
Which is more severe- a STEMI or NSTEMI?
STEMI= very severe MI
