Coronary artery blood flow

Regarding normal coronary artery blood flow, the following statements are true EXCEPT which one?

a) Total left coronary artery flow is initially decreased by tachycardia

b) At rest, right coronary artery blood flow is greater than left coronary artery blood

flow at the beginning of systole

c) Flow in the left coronary artery at rest may be as high as 100 mL/min

d) Right coronary flow is at its lowest at the beginning of diastole

e) At rest, peak left coronary artery flow may be six times higher than peak right

coronary artery flow

Answer: d

Explanation

In health, the development of a tachycardia will initially lead to a drop in left coronary artery flow, as the time in diastole during which flow normally occurs is reduced. In health, this is rapidly compensated for and flow matches any increase in demand. Left coronary artery flow is very low during the whole of systole and may be absent at the beginning of systole. Right coronary flow is generally more even throughout the cardiac cycle, and despite being at its lowest rate in the cardiac cycle, is higher than left coronary flow at the beginning of systole. However, overall, right coronary flow is lower than left, and the peak left-sided flow at rest is around 100 mL/min, compared to 15 mL/min for the right side.