Question

For each of the cardiac phenomena A–E, select the most appropriate option from the features of the electrocardiogram listed below. 

1. The T wave. 

2. The P wave. 

3. The P–R interval. 

4. Depression of the ST segment. 

5. A flat record. 

A. Cardiac arrest. 

B. Repolarization of the ventricles. 

C. Inadequate blood flow to ventricular muscle. 

D. The delay in impulse conduction in the AV node. 

E. Spread of the cardiac impulse over the atria.

Answer 1

A. Option 4 Late pregnancy. The relative increase in plasma volume in late pregnancy results in a low haematocrit. 

B. Option 1 Fainting. The vagal element of the vaso-vagal faint can cause severe bradycardia. 

C. Option 5 Hypothermia. The decrease in the metabolic rate in hypothermia reduces oxygen consumption. 

D. Option 2 Severe haemorrhage. The intense reflex venoconstriction in severe haemorrhage may make it difficult to insert catheters for introducing intravenous fluids. 

E. Option 6 Lying down. Due to the increase in venous return to the heart.