My doctor told me i have 70% right coronary artery blockage. how did he measure the percentage of blockage?

Comparison: The diameter of the narrowest part of the artery is compared to a nearby segment which is felt to be healthy. This is assuming that there is a nearby part that is healthy. In a diffusely diseased artery, it may not be possible to assign a percent stenosis.

Estimate: In general this is performed by comparing the size of the normal coronary artery to the area of the blockage. Under some circumstances this can be performed electronically.