Interpretation of ECG Flashcards
Name the parts that make up the ECG
- P wave
- QRS
- T wave
What does the P wave signal
atrial depolarisation
What does the QRS complex signal
- ventricle depolarisation
What does the T wave signal
- Ventricular repolarisation
What should the first thing in an ECG should you look at
- to make sure you are looking at the right person ECG - check the name, date of birth and hospital number
- its calibration - 1mV = 10mm
What are the two calibration numbers that you should remember
- Paper speed should be 25mm/sec
- calibration should be 1mV = 10mm
- these are at the bottom of most ECG
What should the paper speed in an ECG be
25mm/sec
Where should the chest leads go
6 of them
- V1 - 4th intercostal space on the right sternum
- V2 - 4th intercostal space on the left sternum
- V4 - 5th intercostal space midclavicular line (apex beat)
- V3 between V4 and V2
- V6 - mid axillary line
what does the chest lead allow you to do
- Look at the QRS complex from different planes
describe how the QRS becomes positive
- It becomes positive by the time you reach V4
name the 6 limb leads
I II III aVR aVF aVL
Out of the limb leads which should be positive and negative
I - QRS is meant to be positive II - QRS is meant to be positive III- QRS is meant to be positive aVR - should always be negative aVF - QRS is meant to be positive aVL - halfway between the right direction so half and half
when is QRS positive
QRS is positive when ventricular depolarisation is in the right direction
Name the chest leads
V1-V6
Name the normal ECG wave forms and what is normal
- PR = 120-200 msec (3-5 small Sq)
- QRS < 120 msec (< 3 small Sq)
- QTc < 440 msec
what does 1 small sequence and 1 big sequence in msec
1 small Sq = 40 msec
1 big square= 200 msec
How do you work out the QTc
QT/ square root of RR
what is the QTc dependant on
- it is dependant on the heart rate
How do you read an ECG
– Rhythm – Rate – Axis – P waves – PR interval/ heart block – QRS morphology/ ST segments/ T waves – QT interval
How do you assess Rhythm
- are the QRS regular complexes
- is there a P wave before every QRS
What is the definition of sinus rhythm
- there is a P wave before every QRS
- requires an ECG to know
What is sinus arrhythmia
- variation of RR interval with respiration
- normal variant
Why is lead II used to look at the P wave and thus used in rhythm
one of the best leads to look at the p wave
- atrial depolarisation is in the same direction
What are ectopics
When you heart throws up some extra beats
- ectopics above the AV node are called supraventricular ectopics
- ectopics below the AV node are called ventricular ectopics
What is the difference between supra-ventricular and ventricular ectopics
Supraventricular
- ectopics above the AV node are called supraventricular ectopics
- narrow QRS complex
Ventricular
- ectopics below the AV node are called ventricular ectopics
- Broad QRS complex
What is the normal heart rate
50-100bpm
How do you calculate heart rate
- look at the RR interval
- count the number of squares between the QRS complex
- number of big squares and then divide 300 by the number of big squares
who can you not calculate heart rate in
- Patients who have an irregular heart rhythm
What is the axis
Axis is the net electrical vector of the heart
- gives an overall idea of the direction of depolarisation
in what direction does the heart depolarise
- from the top of the right shoulder and down
- from aVR to II
What is the normal electrical axis
-30 to +120
what is the axis in left axis deviation and right axis deviation
Left axis deviation is when the axis is greater than -30
right axis deviation is when the axis is greater than +120
if lead II is positive then
the axis is likely to be normal
If lead II is not positive then
then the axis is likely to be abnormal - have to work out if it is right and left deviation