An article from National Institutes Of Health suggests that coronary heart disease (CHD) begins with damage to the lining and inner layers of the coronary (heart) arteries. Several factors contribute to this damage. They include :
# smoking,including secondhand smoke
# high amounts of certain fats and cholesterol in the blood
# high blood pressure
# high amounts of sugar in the blood due to insulin resistance or diabetes
# blood vessel inflammation

Plaque may begin to build up where the arteries are damaged. The build up of plaque in the coronary arteries may start in childhood.

Overtime,plaque can harden or rupture (break open). Hardened plaque narrows the coronary arteries and reduces the flow of oxygen-rich blood to the heart. This can cause chest pain or discomfort called angina.

If the plaque ruptures,blood clots fragments called platelets stick to the site of the injury. They may clump together to form blood clots. Blood clots can further narrow the coronary arteries and worsen angina. If a clot becomes large enough,it can mostly or completely block a coronary artery and cause a heart attack.

A healthy diet can help reduce your risk of developing coronary heart disease and high blood pressure.