CardioMind, a Sunnyvale, Calif., developer of artery-opening stents, said ithas  launched the first human tests of its experimental product. That milestone triggered the release of $22 million — a second tranche of a $33 million funding the company initially reported last July.

The CardioMind stents are designed to treat blockages in smaller blood vessels. The company claims that its Sparrow system is 70 percent smaller in diameter than any stents on the market, potentially making it possible for cardiologists to snake the drug-coated, expandable mesh tubes into blood vessels that are 2.3 millimeters wide or smaller. The study will test both drug-coated and bare-metal versions of the Sparrow stents against a competing stent in 220 patients.

Stents have been in the news a lot over the past year after initial studies suggested that they aren’t any more effective than drug treatment in patients suffering chest pain and that drug-coated stents designed to prevent the formation of scar tissue might instead contribute to dangerous blood clots. Additional research has since muddied those findings further, although initial concerns sent stent sales plunging 37 percent last year at large manufacturers like Boston Scientific and Johnson & Johnson.

Using stents to open up “peripheral” blood vessels such as those in the legs has grown more popular in recent years — and small wonder, given that such procedures could pull in a staggering $1.2 billion by 2012, according to a 2006 market-research report by Frost & Sullivan. To the best of my knowledge, however, there isn’t yet any clinical evidence that stent treatment is any more effective in treating peripheral vascular disease than other therapies.