Lowering cholesterol far below the level that most doctors now consider adequate can substantially reduce patients' risk of having or dying from a heart attack, researchers reported today. The findings, cardiologists say, will greatly change how doctors treat patients with heart disease and will provide the impetus to re-evaluate how low cholesterol levels should be. The study compared high doses of one of the most powerful cholesterol-lowering drugs, Pfizer's Lipitor, to a less potent drug, Pravachol, made by Bristol-Myers Squibb, which conducted the trial. The patients taking Lipitor were significantly less likely to have heart attacks or to require bypass...