ECG Changes (passmed) Flashcards
What are the features on an ECG of hyperkalaemia
- Tall tented T waves
- Flattening/loss of P waves
- Broad QRS Complex
- Ventricular Fibrillation
What are the features of hypokalaemia on an ECG
- Increased P wave amplitude
- Prolonged PR interval
- ST depression
- T wave flattening/inversion
- Prominent U waves
What are the features of hypercalcaemia on an ECG
Shortened QT interval
Osbourne (J waves)
Ventricular irritability (V Fib)
What are the features of hypocalcaemia on an ECG
Broadening QT interval
What is the P wave
Atrial depolarisation (left and right atria).
Should be no more than 2.5mm high and no more than 0.12 seconds long.
Large P wave = Right atrial hypertrophy.
Bifid P wave = Left atrial hypertrophy.
What is the R wave
Always the first positive going deflection.
Large R wave = Thin patient or hypertrophy.
Small R wave = Low voltage depolarisation or significant impedance (air, fluid, blood, fat).
What is the T wave
Ventricular Repolarisation
Inversion in V1-V2 = Normal in healthy young people.
Inversion in V2-V6 = MI, BBB, Hypertrophy, WPW syndrome.
What is the PR interval?
The time from the beginning of atrial depolarisation to the beginning of ventricular depolarisation.
- AV Node conduction time
0.12-0.2 seconds
<0.12 = An extra excitatory pathway - for example, WPW syndrome (+delta wave) = slurred upstroke of QRS.
> 0.12 = Normal in young athlete, medication (beta blocker), heart block.
What is the QRS complex
Ventricular depolarisation. Should be <0.12
> 0.12 seconds = blocking of one of the bundle branches
How to measure PR and QT segments
PR = Beginning of P to beginning of R
QT = Beginning of Q to end of T
What is the QT interval
The beginning of ventricular depolarisation to the end of ventricular repolarisation
The time is dependent on the heart rate (QTc)
QTc of >0.5 seconds in MALE OR FEMALE is dangerous - associated with tornadoes des pointes.
It is classed as prolonged if >440 seconds in males or >460 seconds in females.
Can cause torsades des pointes = which can lead to ventricular fibrillation
What is the ST segment
The period of time between ventricular depolarisation and ventricular depolarisation.
It should be an isoelectric line.
ST elevation = Infarction, pericarditis, BBB, cardiomyopathy, hypothermia.
ST depression = Ischaemia, digoxin toxicity, BBB, tachycardia.
What are the causes of right axis devaition
When LL I is negative.
Right ventricular hypertrophy, PE, anterolateral MI.
W-P-W syndrome.
What are the causes of left axis deviation
When LL II is negative
Ventricular tachycardia, inferior MI, left ventricular hypertrophy.
W-P-W syndrome.
Which ECG leads represent Inferior coronary artery
LL II
LL III
AvF
= RCA and/or left circumflex
