THE idea that cholesterol plays a key role in heart disease is so tightly woven into modern medical thinking that it is no longer considered open to question. This is the message that emerged all too clearly from the recent news that the drug Vytorin had fared no better in clinical trials than the statin therapy it was meant to supplant. Vytorin is a combination of cholesterol-lowering drugs, one called Zetia and the other a statin called Zocor. Because the two drugs lower LDL cholesterol by different mechanisms, the makers of Vytorin (Merck and Schering-Plough) assumed that their double-barreled therapy...