Coronary heart disease can lead to the build-up of fatty deposits (atheroma) inside the coronary arteries, restricting blood flow to the heart muscle cells.
Table 1 shows how the percentage occlusion (blockage) of a patient's coronary artery affects the blood flow rate to the downstream cardiac muscle.
Table 1
| Coronary artery occlusion (%) | Blood flow rate (cm3/min\text{cm}^3\text{/min}cm3/min) |
|---|---|
| 0 | 240 |
| 20 | 192 |
| 50 | 96 |
| 70 | 44 |
| 90 | 12 |
Describe the trend shown in Table 1 between the coronary artery occlusion and the blood flow rate.
Calculate the percentage decrease in the blood flow rate when the artery's occlusion increases from 0% to 50%. Show your working.
Assuming the change in blood flow rate is linear between an occlusion of 50% and 70%, estimate the blood flow rate when the coronary artery is 60% occluded. Show your working.