It's a scary number: 685,000 Americans died of heart disease in 2003, making it the country's No. 1 killer. At the same time, heart disease represents a major opportunity for drug makers, provided they can develop compounds to effectively treat the condition. Yesterday, AstraZeneca (NYSE:AZN) unveiled some attention-getting data on a new use for one of its existing drugs, but the results' potential benefits for the company's sales are less clear.

At the annual meeting of the American College of Cardiology, the London-based drug developer released a study showing that high doses of its cholesterol drug Crestor reduced patients' arterial deposits of fatty substances and other gunk by between 7% and 9%. The findings were significant because they demonstrated that Crestor can actually reverse atherosclerosis, a condition that develops over many years.

Analysts were quick to point out that the study showed Crestor outperforming Pfizer's (NYSE:PFE) Lipitor, the market's best-selling cholesterol medication. According to, Pfizer is unhappy about AstraZeneca's claim that Crestor was the first statin to cause plaque regression; Lipitor also was shown to reduce plaque in the arteries of some patients, although by only 5.9%.

Even though the Crestor data is encouraging, Pfizer has little to fear from AstraZeneca's drug. At $1.2 billion in annual sales, Crestor has a long way to go before it challenges the popularity of Lipitor, which rang up $13 billion in sales last year. Perhaps more significantly, Crestor carries risks that Lipitor does not, including a greater potential linkage to myopathy, or muscle toxicity, which causes muscle weakness.

The untapped potential of statins may be the most important discovery of the Crestor study, and it's clearly not lost on many drug makers. Merck (NYSE:MRK) and Schering-Plough (NYSE:SGP) launched statin-combination drug Vytorin in 2004, and Merck and Pfizer continue to develop other new statin formulations.

Indeed, major changes could occur in the cholesterol drug market in the coming years. But these changes will likely stem from Vytorin and the launch of drugs now in development, not from growing sales of Crestor.

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Pfizer is a Motley Fool Inside Value recommendation. Merck is a Motley Fool Income Investor recommendation.

Fool contributor Brian Gorman is a freelance writer in Chicago. He does not own shares of any companies mentioned in this article.