St. Jude Medical (STJ) shares jumped Wednesday after the company beat first-quarter earnings estimates and boosted guidance.

Shares were up $3.47, or 9.6%, to $39.73.

The medical device company earned $119 million, or 32 cents a share, in the latest quarter, compared with $95 million, or 26 cents a share, a year earlier. Excluding a charge in the most recent quarter related to its January acquisition of Endocardial Solutions, earnings were $132 million, or 35 cents a share. Revenue was $663.9 million in the 2005 quarter.

Analysts had been forecasting earnings of 33 cents a share on revenue of $646 million. The company also raised earnings guidance for the current quarter, predicting earnings of 35 cents to 37 cents a share. Analysts were forecasting 34 cents a share.

St. Jude reported better-than-expected sales of the company's implantable cardioverter defibrillators, which rose 72% from a year ago to $206 million. ICDs monitor heart rhythm and deliver a shock to the system during cardiac arrest to prevent sudden death.

"This quarter's ICD sales represent a clear gain in market share," St. Jude Medical CEO Daniel J. Starks said. "Our structured continuous improvement programs continue to pay off, as reflected in our expanding gross profit margin and our EPS growth." The company expects ICD market share to continue to grow.

First-quarter ICD sales growth came at the expense of a 3% drop in pacemaker sales to $217 million. The company says patients who would previously have gotten pacemakers now get ICDs.

Starks says the company beat revenue estimates partially as a result of a "lumpy" market dynamics. In the fourth quarter, St. Jude reported ICD sales at the low end of its guidance.

For the year, the company sees earnings of $1.39 to $1.43 a share, compared with the Thomson First Call consensus estimate of $1.40 a share. The company expects a stronger second half than first, but it is cautious. It says it may increase its guidance after the second quarter.

St. Jude also encouraged investors to be patient in 2005 and 2006 while it improves technology and conducts clinical trials. The company expects strong growth in 2007 and beyond.

Starks says St. Jude could make a significant investment in atrial fibrillation cardiac programs. The company expects its cardiology division to see competition from other vascular closure device makers, but it says lost sales will be offset by three new products it gained through its acquisition of Velocimed earlier this month.