'A' Level Medical Option Questions - The Heart - ECG


The graph below shows a normal electrocardiogram (ECG) signal obtained at the surface of the skin of a patient.

(a) What is the amplitude of the main pulse in the signal?

Pulse amplitude: 0.9 mV

1 mark

(b) Find the period of the heart beat and from it calculate the pulse rate per minute.

T = 0.7s

f = 1/T = 1/0.7 Hz

60/.07 = 86 min–1

2 marks

(c) What changes would you expect to see in the electrocardiogram if the patient began to take exercise?

T would get shorter as the flat part of trace would shrink

When you exercise the heat beat rate increases - the time interval between beats decreases - the 'beat' part stays roughly the same..

2 marks

(d) On the graph, label with a P the points where atrial contraction occurs and with a Q the points where ventricular contraction starts.

Note it says 'points' - so label all of them!

See trace above for P and Q location

2 marks

Total 7 marks