This week, the overall grades of three Medical Devices stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Volcano (NASDAQ:VOLC) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Volcano designs, develops, manufactures and commercializes a suite of intravascular ultrasound (IVUS) and functional measurement (FM) products that enhance the diagnosis and treatment of vascular and structural heart disease. VOLC also rates an F in Portfolio Grader’s specific subcategory of Earnings Momentum. The stock’s trailing PE Ratio is 42.7. To get an in-depth look at VOLC, get Portfolio Grader’s complete analysis of VOLC stock.

Slipping from a C to a D rating, Dentsply International (NASDAQ:XRAY) takes a hit this week. Dentsply International designs and manufactures a range of dental products. 

For more information, get Portfolio Grader’s complete analysis of XRAY stock.

Hansen Medical (NASDAQ:HNSN) earns an F (“strong sell”) this week, moving down from last week’s grade of D (“sell”). Hansen Medical develops and manufactures medical robotics designed for positioning, manipulation, and control of catheters and catheter-based technologies. The stock gets F’s in Earnings Growth, Earnings Momentum, and Equity. Cash Flow and Sales Growth also get F’s. The stock price has fallen 17.9% over the past month, worse than the 7.2% increase the Nasdaq has seen over the same period of time. As of Aug. 27, 16.1% of outstanding Hansen Medical shares were held short. In the past week, the volume of trades plummeted to half the previous rate. For a full analysis of HNSN stock, visit Portfolio Grader.

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.