Pre-Algebra on Khan Academy: No way, this isn't your run of the mill arithmetic. This is Pre-algebra. You're about to play with the professionals. Think of pre-algebra as a runway.
Coronary heart disease. Coronary heart disease (CHD) is the leading cause of heart attacks. CHD is a condition in which the coronary arteries (the major blood vessels that supply the heart with blood) get clogged up with deposits of cholesterol. These deposits are called plaques.
A heart attack can cause a cardiac arrest. In cardiac arrest (also called sudden cardiac death or SCD), death results when the heart suddenly stops working properly. This is caused by abnormal, or irregular, heart rhythms (called arrhythmias). The most common arrhythmia in cardiac arrest is ventricular fibrillation.