A first look at the ECG Flashcards
What plane do standard limb leads look at?
vertical/frontal
What does an approaching wave of depolarisation cause on the ECG?
An upward going blip
Are fast or slow events transmitted better?
Fast
What is the P wave caused by?
Atrial depolarisation
What is the QRS complex caused by?
ventricular depolarisation
What is the T wave caused by?
ventricular repolarisation
What is the PR interval?
time from atrial depolarisation to ventricular depolarisation
How long does the PR interval last?
0.1-0.2 seconds
What is the PR interval transmitted through and how does this affect the time?
The AV node which is the delay box and why it is the slowest part of the process
What is the QRS interval?
Time for the whole of the ventricle to depolarise
How long does the QRS wave last?
0.008 seconds
What is the QT interval?
Time spent while ventricles are depolarised
What does the QT interval vary with?
heart rate
What is the normal QT interval at 60bpm?
0.42 seconds
Why is atrial repolarisation not seen on the ECG?
Coincides with ventricular depolarisation which involves more tissue and swamps the signal from the atria
What things can cause axis deviation?
heart rotated to left
hypertrophy on left
atrophy on right
What extra information can augmented lead limbs give you?
An extra 3 perspectives
What plane do the precordial leads look at?
Transverse plane
What are the 2 ways to determine heart rate from an ECG?
Measure RR interval and work out how many occur in 60 seconds
Better one is to count the R waves in 6 seconds and multiply by 10
What is normal sinus rhythm?
60-100 bpm
What is bradycardia?
below 60bpm
What is tachycardia?
above 60bpm
What is STEMI?
ST elevated myocardial infarction
What is NSTEMI?
Non ST elevated myocardial infarction
