Oronary heart disease is caused by a buildup of plaque in the arteries that supply blood to the heart. when the flow of blood to the heart is restricted or blocked, the heart can be damaged due to a lack of oxygen. further, if a large piece of plaque buildup gets dislodged from an artery wall, it can get stuck in other arteries throughout the body, including arteries in the brain. for simplicity, let's assume that the artery is cylindrical with a radius of r. the flow rate of a viscous fluid is given by poiseuille's law q=(π/8)(δp/ηl)r4.