St. Jude Medical Incorporated's first-quarter income rose 27 percent behind climbing sales of implantable cardioverter defibrillators (ICDs) -- the company's biggest and most closely watched products -- and a significant contribution from favorable foreign-currency rates.

After topping Wall Street expectations for the quarter, the Little Canada maker of heart-rhythm products and other medical devices boosted its full-year earnings outlook Wednesday and issued second-quarter guidance ahead of analysts' views. The company also tightened its full-year forecast for revenue in the heart-rhythm market toward the upper end of its earlier forecast.

St. Jude shares rose 41 cents Wednesday, to close at $44.15, after slumping earlier in the session.

The company reported net income of $184.8 million, or 53 cents a share, compared with $145.7 million, or 41 cents a share, a year earlier, topping its earlier forecast. St. Jude noted that it would have earned a penny more per share in the recent quarter with the help of a federal research and development tax credit that it expects will be extended retroactively to the start of the year.

Revenue increased to $1.01 billion, from $887 million a year ago, with $45 million linked to the weak dollar. Gross margin rose to 74.2 percent, from 73.1 percent in the year-ago period.

Analysts surveyed by Thomson First Call had expected, on average, that St. Jude would earn 51 cents per share on revenue of $995 million in the first quarter.

Sales in St. Jude's heart-rhythm unit, which includes implantable defibrillators and pacemakers, jumped 15 percent, to $632 million, topping the company's January forecast. The performance was helped by a 20 percent climb to $361 million in sales of implantable cardioverter defibrillators, which provide shocks to treat hearts when they beat at dangerous speeds.

The ICD sales figure came in ahead of the consensus analyst outlook of about $350 million, according to Deutsche Bank analyst Tao Levy.

The U.S. ICD market has been struggling for years now to overcome the negative, growth-squelching effects of industry recalls in 2005. But St. Jude, which has said it expects to take market share in a sector it shares with industry leader Medtronic Inc. and Boston Scientific Corp., pointed to favorable signs.

"We have definitely seen the ICD market stabilize," Daniel Starks, the company's chief executive, said during a conference call with analysts.

St. Jude pacemaker sales rose 10 percent in the recent quarter, to $271 million. Some analysts said the pacemaker tally met or topped expectations, although J.P. Morgan analyst Michael Weinstein said in a note to investors that sales of the devices were $14 million below his forecast.

Looking ahead to the second quarter, St. Jude expects heart-rhythm sales of $650 million to $680 million. For the full year, the company sees sales between $2.63 billion and $2.7 billion. The bottom end of the forecast range has been increased since St. Jude reported fourth-quarter results.

For overall guidance, the company forecast second-quarter earnings of 54 to 56 cents a share, and boosted its full-year forecast by 7 cents a share, to a range of $2.15 to $2.20 a share.