The American College of Cardiology and the American Heart Association have released a new clinical practice guideline for the treatment of blood cholesterol in people at high risk for cardiovascular diseases caused by atherosclerosis, or hardening and narrowing of the arteries, that can lead to heart attack, stroke or death. The guideline identifies four major groups of patients for whom cholesterol-lowering HMG-CoA reductase inhibitors, or statins, have the greatest chance of preventing stroke and heart attacks. The guideline also emphasizes the importance of adopting a heart-healthy lifestyle to prevent and control high blood cholesterol.