On a day when the Dow Jones Industrial Average (INDEX: ^DJI) fell 190 points on thin trading as high gas prices combined with the European debt drama, significantly larger moves happened in the health-care sector. For instance, Geron (Nasdaq: GERN) which shocked investors yesterday after announcing the elimination of its stem-cell program, added another 7% to its continuing slide today.

But instead, let's focus on what went right. We have a duo of biotechs that had a great showing, along with a medical-device maker popping after hours.

Investors in little-known ARCA Biopharma are 43% richer than they were when they woke up, all thanks to a positive trial result. The company's drug candidate, GencaroTM, is hoping to carve out space in the large and lucrative atrial fibrillation market. It had a 74% reduction in new a-fib onsets for patients with a relatively common genotype.

Don't feel bad if you've never heard of ARCA. Even after its rocket shot, the company's market cap is below $20 million. Considering a-fib treatments are where heavyweights like Bristol-Myers Squibb (NYSE: BMY) and Johnson & Johnson play, ARCA has an uphill battle in front of it.

Meanwhile, BioSante Pharmaceuticals (Nasdaq: BPAX) jumped 8% after the company revealed that its female sexual dysfunction product LibiGel improved free testosterone levels in women post-menopause. The real winner, though, may be Antares Pharma (AMEX: AIS), whose gel BioSante uses to deliver the drugs to patients. Not only does Antares have a huge financial stake in LibiGel's success, but it also further validates its platform, which is also licensed out to Jazz Pharmaceuticals (Nasdaq: JAZZ). LibiGel is currently in phase 3 trials that the FDA signed off on, so as long as the efficacy and safety profile are solid, investors are looking at a less surprise-filled approval process.

Finaly, Zoll Medical (Nasdaq: ZOLL) reported estimate-beating fourth-quarter results after the market closed. Thanks to a 57% sales increase of its LifeVest defibrillator, Zoll managed earnings growth of 65%. More exciting yet are the company's 2012 estimates. At the high end, management believes 19% revenue growth is achievable, or a full $20 million more than the $603 million analysts had expected. The good news erased a 5% decline that happened during the trading session, and if management's assessments are accurate, more good days lay ahead for investors.

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David Williamson owns shares of Johnson & Johnson, but he holds no other position in any company mentioned. Check out his holdings and a short bio. The Motley Fool owns shares of Johnson & Johnson. Motley Fool newsletter services have recommended buying shares of and creating a diagonal call position in Johnson & Johnson. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.