Shares of

Health Grades

(HGRD)

were among the worst-performing health-related stocks Wednesday, falling 9% after the company reiterated its 2005 earnings projection but lowered its sales estimate.

The health care ratings company continues to see earnings at the high end of its previous guidance of 10 cents to 13 cents a share, but sales growth is now seen at slightly lower than 45%, which is below the company's previous guidance of 45% to 55%.

For 2006, the company expects an operating margin of about 25% on sales growth of at least 40% over 2005 results. Shares recently were trading down 59 cents to $6.

WebMD Health

(WBMD)

fell 4% after the provider of health information services said it acquired eMedicine.com for $25.5 million. eMedicine.com, an online publisher of medical information, had break-even earnings and about $6 million in revenue during 2005. "The acquisition of eMedicine.com complements WebMD's current offerings for physicians and health care professionals," WebMD said in a statement. WebMD expects the deal to add to 2006 earnings before interest, taxes, depreciation, amortization, but it will be offset by integration-related costs. The company's shares recently were down $1.51 to $37.49.

Aetna

(AET)

shares rose 4% after the health insurance company named a new chief medical officer and was upgraded by J.P. Morgan. The company named Troyen Brennan chief medical officer to take over for Charles Cutler, who had been serving as interim medical chief. Brennan, who joins Aetna Feb. 21, is a professor of medicine at Harvard Medical School and also served as president and CEO of Brigham & Women's Physicians Organization.

Separately, J.P. Morgan upgraded Aetna to overweight from neutral. Aetna shares rose $3.67 to $92.88.

Shares of

Guidant

( GDT) traded actively after the medical device company said

Boston Scientific's

(BSX) - Get Report

most recent $27 billion buyout offer is superior to

Johnson & Johnson's

(JNJ) - Get Report

$24 billion offer. Guidant, which already signed a merger agreement with Johnson & Johnson, now must wait five business days, or until Jan. 25, before changing its recommendation or ending the Johnson & Johnson deal, which is worth $71 a share, and agree to Boston Scientific's offer, valued at $80 a share.

In a statement late Tuesday, Johnson & Johnson said that it "considers the proposal from Boston Scientific to be a highly dilutive and leveraged transaction based on extremely aggressive business projections and, as such, one that will not provide $80 per share in value to Guidant shareholders." Johnson & Johnson said that it would consider alternatives under its existing agreement with Guidant. Shares of Guidant were recently trading down 35 cents to $75.87; Johnson & Johnson was trading up 38 cents to $61.66; and Boston Scientific shares were up 5 cents to $23.95.

Other health care volume movers included

Pfizer

(PFE) - Get Report

, down 37 cents to $23.91;

Insmed

(INSM) - Get Report

, up 48 cents to $3.23;

Merck

(MRK) - Get Report

, down 22 cents to $32.99;

Elan

(ELN)

, up 10 cents to $16.71;

Bristol-Myers Squibb

(BMY) - Get Report

, down 16 cents to $22.14;

UnitedHealth Group

(UNH) - Get Report

, up 5 cents to $61.05;

Amgen

(AMGN) - Get Report

, up 45 cents to $78.67; and

Schering-Plough

( SGP), up 8 cents to $19.93.