Heart disease can be caused when bad cholesterol (LDL-C) is turned into a destructive free radical. Oxidized LDL-C starts inflammatory or immune cells inside of the heart muscle arteries to release chemicals which start this cascade of damage turning monocytes (regular infection white cells) into foam cells. Then the foam cells attract more free radicals and other damaging molecules and harden up inside in the artery (plaques). This process continues until there is a cement pipe-like artery inside your heart. Since the arteries are hard they cannot expand like they should and your blood pressure rises. As your blood pressure rises it causes more damage to your heart and the damage accelerates. The damaged arteries also attract blood clotting cells known as platelets. The platelets form clots where the plaques are and cause the plaques to become larger. The clots can get so big they close off the vessel (blood thrombus) and damage the area downstream. This is what causes heart attacks (myocardial infarction—death of heart muscles). Sometimes the blood clots break loose (emboli) and travel down a vessel until it reaches an area too small to travel through. If the clot is in the heart it causes a heart attack. If it is in the artery of the brain it causes a stroke. If it is inside your lung you have a pulmonary embolism. Sometimes the plaques can cause the vessel to spasm, which in turn stops the blood flow. It is a vicious circle: hypertension (high blood pressure) damages the vessels, which in turn form more plaques, which make the vessel harder and increases the blood pressure further. It is easy to see how high blood pressure, heart attacks, and strokes occur as a result of free-radical damage. A diet high in saturated fats and trans-fatty acids (the bad types of fat) contribute to high LDL cholesterol levels which increases the amount which can be turned into the damaging free radicals.
