ECGs Flashcards
What does the P-wave represent on an ECG?
Atrial depolarisation
What does the QRS complex represent on an ECG?
Ventricular depolarisation
What does the T-wave represent on an ECG?
Ventricular repolarisation
What is the PR interval and what causes it?
Time from atrial depolarisation to ventricular depolarisation.
Delay due to transmission through the AV node
What is the QT interval?
Time for ventricles to depolarise and repolarise
Why is the T-wave positive going?
The AP is longer in endocardial cells than in epicardial cells so the wave of repolarisation runs in the opposite direction to the wave of depolarisation.
What is the normal PR interval?
0.12 to 0.2 seconds
What is a normal QT interval?
0.42s at 60bpm
(varies with HR)
How do you measure HR on an ECG?
Count R waves in 30 large squares (= 6s) and multiply by 10
What HR is normal?
60-100 bpm
What HR is tachycardia?
Above 100 bpm
What HR is bradycardia?
Below 60 bpm
What does it suggest if a QRS complex is not preceded by a p-wave?
Heart block
Problem with conduction spreading to atria ventricular node.
What does it suggest it the PR interval is too long?
Suggesting problem with AV conduction and patient may have Av/heart block
What does it suggest if the QRS complex is too wide?
- Indicate a problem with fast conducting system
- Problem with bundle of His and Purkinje fibres
- Widening in left & right bundle branch block
