Final answer:
Coronary heart disease is the most serious form of heart disease and is caused by atherosclerosis, which restricts blood flow to the heart and increases the risk of a heart attack.
Step-by-step explanation:
The most serious form of heart disease is coronary heart disease. It is caused by a condition called atherosclerosis, which is the build-up of plaque in the arteries that supply the heart muscle. This build-up restricts blood flow to the heart and increases the risk of a heart attack. Coronary heart disease is the leading cause of death among adults in the United States.