ECG Flashcards
How do potential arise at the surface of the body
Currents that flow when membrane potential of myocardial tissue is change (depolarisation or depolarisation)
Only large masses generate detectable current
What is the recording (positive) electrode
Seeing electrode
When depolarisation moves towards recording electron it goes upwards
When depolarisation moves away from electron it goes downwards
From where to where does Lead 1 go
RA-ve to LA+ve
From where to where does Lead 2 go
RA-ve to LL+ve
From where to where does Lead 3 go
LA-ve to LL+ve
What causes the P wave in lead 2
Atrial depolarisation moving towards the recording electron
What does the QRS complex represent
ventricular depolarisation
What does the T wave represent
Ventricular repolarisation
What is the PR interval
Start of P wave till start of QRS complex
Reflects time for SA node impulse to reach ventricles
Strongly influenced by AV node delay
What is the ST segment
End of QRS complex to start of T wave
Ventricle contract (systole)
What is the QT interval
From start of QRS complex to end of T wave
Reflects time of ventricular depolarisation and repolarisation
What are the 12 ECG leads
3 standard limb leads (I, II and III) - bipolar
3 augmented voltage (aV) leads (aVR(right), aVL(left) and aVF(foot) - unipolar
6 chest leads (V1-V6) (aka precordial leads)
Why 12 leads
determine axis of heart
ST segment or T wave changes in specific regions
Voltage criteria changes
What is the hex axial reference system
Views heart in frontal plane provided by standard and augmented limb leads
6 views
What is the TP segment
Between T and P wave
Ventricle relax (diastole)
