The grades of four Medical Devices stocks are better this week, according to the Portfolio Grader database. Every one of these stocks has an “A” (“strong buy”) or “B” overall (“buy”) rating.

Edwards Lifesciences (NYSE:EW) is making headway this week, with the company’s rating improving to an A (“strong buy”) from a B (“buy”) last week. Edwards Lifesciences provides products and technologies related to the treatment of advanced cardiovascular diseases. In Portfolio Grader’s specific subcategory of Equity, EW also gets an A. For more information, get Portfolio Grader’s complete analysis of EW stock.

Spectranetics (NASDAQ:SPNC) boosts its rating from a B to an A this week. The Spectranetics Corporation develops, manufactures, markets and distributes single-use medical devices used in minimally invasive procedures within the cardiovascular system, many of which are used with its proprietary excimer laser system. For more information, get Portfolio Grader’s complete analysis of SPNC stock.

This week, Gen-Probe

(NASDAQ:GPRO) pushes up from a B to an A rating. Gen Probe develops, manufactures, and commercializes diagnostic products based on its genetic probe technologies. For more information, get Portfolio Grader’s complete analysis of GPRO stock.

This week, PhotoMedex (NASDAQ:PHMD) is showing significant improvement as the company’s rating hops from a C (“hold”) to a B (“buy”). PhotoMedex manufactures excimer laser and fiber-optic systems used to treat dermatological conditions such as psoriasis, vitiligo, atopic dermatitis, and leukoderma. Shares of PHMD have increased 16% over the past month, better than the 1% increase the Nasdaq has seen over the same period of time. For more information, get Portfolio Grader’s complete analysis of PHMD stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.