ECG

Question 1

What does the P wave on an ECG represent?

Answer 1

Depolarisation of atria. The atria begin contracting approximately 25ms upon P wave. SAN stimulates waves of excitation that triggers atrial contraction.

Question 2

At which node does the current slow down allowing for atrial muscle contraction?

Answer 2

AV Node

Question 3

What does the QRS complex represent?

Answer 3

Depolarisation of the ventricles, requires greater electrical amplitude considering the larger ventricular cardiac muscle. Enlarges during hypertrophy (indicative of greater muscle mass) (Height & width).

Question 4

At what part of the QRS does ventricular contraction begin?

Answer 4

R wave (peak)

Question 5

What happens at the ST segment?

Answer 5

Plateau phase. Normal at baseline. The interval between ventricular depolarisation and repolarisation. ST segment is isoelectric (ventricular cardiomyocytes maintain resting potential).

Question 6

What does the QT interval represent?

Answer 6

Total duration of ventricular depolarisation & repolarisation

Question 7

What does the T wave represent?

Answer 7

Repolarisation of the ventricles

Question 8

What does a normal PR segment (interval) indicate?

Answer 8

Isoelectric line is dependent on the time taken of electrical conductance through the AV node. Delays in passage of impulse from SAN to AVN would be visible in a longer PR interval.

Question 9

What does an ECG lead refer to?

Answer 9

Imaginary line between 2 ECG electrodes. Electrical activity of this lead is measure and recorder as part of the ECG/