when fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hardwhen fatty materials inside an artery become stiff and hard