It would seem that St. Jude (NYSE:STJ) has cracked the code on the ICD (implantable cardioverter defibrillator) business. Once again, St. Jude had a very strong quarter, and ongoing market share gains in the ICD business are largely responsible.

For the second quarter, St. Jude posted revenue growth of 30%. With improvements at both the gross margin and operating margin lines, operating income swelled 45%, and net income wound up growing 41% (if certain charges and items are excluded).

ICD sales were the star of the second-quarter show. Sales rose 92% -- and I believe this is the first time that ICD sales have exceeded pacemaker sales in a quarter. Business was strong both here and abroad, and the company continues to gain market share.

Although we won't know for sure until the other two ICD players report earnings, I would suspect that St. Jude is making most of its inroads at the expense of Guidant (NYSE:GDT). Guidant generally has older technology relative to Medtronic (NYSE:MDT) and St. Jude, and I believe St. Jude has exploited that. Looking ahead, concerns related to the recent device-failure reports and recalls from Guidant could likely be a further boon to St. Jude's efforts to grow market share.

Though ICDs are the shining star now, St. Jude did do well with its other businesses. Sales in the atrial fibrillation business climbed about 65% (boosted by the acquisition of Endocardial Solutions) and the vascular sealing business also performed well. Pacemaker sales were only up 4%, but that's actually not so bad given the generally low expectations for the pacemaker business.

If I have any real quibble with St. Jude, it's this: While management goes out of its way to provide detailed guidance on a business-by-business basis, it doesn't offer a cash flow statement in the earnings release. I realize that's not a terrible offense, but if they have sufficient clarity to offer a balance sheet, they should have sufficient information to offer a cash flow statement.

Whether your cut-off makes St. Jude a mid-cap or a large-cap, this company is certainly growing -- and the stock's valuation reflects that. I do believe further growth and success lie ahead for St. Jude, but at current prices there is little margin for error.

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).