Week 3 Cardio Flashcards
What does a Q wave indicate?
Depolarisation of the septum
What does a P wave indicate?
Atrial depolarisation
What does an R wave indicate?
Main depolarisation of the ventricles
What does an S wave indicate?
Depolarisation of the last remaining myocytes in the ventricles
What does a T wave indicate?
Repolarisation of the ventricles
What is the PQ interval?
The delay in conduction from the AV node to the ventricles
What does the QT interval represent?
The time taken for depolarisation and Repolarisation of the ventricles
(Ventricular systole + diastole)
What direction does depolarisation occur in the septum?
Base to apex, and left to right
Why does the T wave record a positive deflection if it is a negative charge?
Repolarisation is negative, but because it is a negative charge moving towards a negative electrode, it records an upwards deflection
What does isolectric mean?
No net movement of current. This can be either when the cell is either completely depolarised or completely repolarised.
Where are the electrodes of lead 1 positioned?
Left arm and right arm
Where are the electrodes of lead 2 positioned?
Left leg, right arm
Where are the electrodes of lead 3 positioned?
Left arm, left leg
What angle is lead 1?
Zero degrees
What angle is lead 2?
60 degrees
What angle is lead 3?
120 degrees
What angle is aVF?
90 degrees
What angle is aVR?
210 degrees
What angle is aVL?
-30 degrees
What does the ‘mean electrical axis of the heart’ refer to?
The direction where most of the flow of current is heading. This is calculated by the ECG machine and is recorded as the different deflections.
What is a biphasic deflection?
When the current is moving approximately perpendicularly to the angle of the lead. It will record an upward and downward deflection
