Despite concerns regarding the safety of drug-coated stents in a small fraction of patients, medical device maker Medtronic (NYSE:MDT) keeps fighting its way toward the U.S. market. That campaign suffered a setback Friday from the FDA, but the battle's not over yet.

If it gains FDA approval, Endeavor would make Medtronic just the third player in the U.S. drug-coated stent market, after current heavyweights Boston Scientific (NYSE:BSX) and Johnson & Johnson (NYSE:JNJ), and the first addition since 2004.

On Friday, the FDA said that the Endeavor failed to meet a secondary goal in a study that compared the Endeavor stent to Boston Scientific's Taxus stent. The study showed that the Endeavor stent had a slightly higher rate of narrowed artery walls around the stent when compared to Taxus. However, the difference was considered insignificant, and most of Wall Street expects the FDA to approve the Endeavor stent -- possibly as early and the end of this year.

The company might not have been hoping for this news, but it shouldn't be a major concern in the grand scheme of things. Coronary stents accounted for only 15.5% of Medtronic's revenue in its Q1. So while it might take some time for Medtronic to appease the FDA regarding Endeavor's safety, it has plenty more sources of revenue. The company grew its implantable cardiac defibrillator (ICD) sales by a respectable 8% in its first quarter. Medtronic's ICD revenue now accounts for 23.2% of the company's total sales.

Fools should remain excited about any possible upside from Endeavor's approval. Still, remember that the company also has a well-diversified product portfolio to protect itself against any unforeseen pitfalls ahead.

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