St. Jude Medical Inc. (STJ) posted a 14% jump in first-quarter net income as its major medical-products, including implantable defibrillators, shrugged off the economic downturn and posted solid sales gains.

While the company said Wednesday it expects unfavorable currency rates to nick 2009 sales and earnings more than previously expected, it held its full-year earnings guidance in check because of overall business performance and growth expectations. Investors responded positively, lifting St. Jude shares 6.4% to $36.53 in recent trading.

Chairman and Chief Executive Daniel J. Starks said the results reflect the company's "resilience" amid the recession, noting that growth dynamics in important product markets "are remarkably stable."

"These results further strengthen our confidence that we are in the right markets with the right products and that our growth program remains on track," he said in a press release.

The St. Paul, Minn., company posted net income of $201.3 million, or 58 cents a share, up from $176.6 million, or 50 cents, a year earlier. The per-share result matched the average forecast among analysts surveyed by Thomson Reuters and landed in the middle of the range St. Jude projected in January.

Net sales rose 12% to $1.13 billion, topping Wall Street forecasts, and were up 17% if the impact of a stronger dollar is excluded. The strong dollar's impact on overseas sales is important for St. Jude because it derives nearly half its sales from outside the U.S.

Gross margin in the first quarter slipped to 74% from 74.2%.

In St. Jude's biggest business, for implanted heart-rhythm devices such as pacemakers and defibrillators, sales rose 7% in the first quarter, or 12% excluding the currency hit. Considering St. Jude believes the overall market is growing in a mid single-digit range, the first-quarter results confirm St. Jude continues to gain market share there, Starks said on a conference call.

The company expects that trend to continue in a heart-rhythm market it shares with Medtronic Inc. (MDT) and Boston Scientific Corp. (BSX). In the $6 billion market for implantable defibrillators, which shock hearts to stop potentially dangerous rhythm problems, St. Jude said its sales rose 9% in the quarter, or 14% excluding currency.

Elsewhere in the company, sales of products to address the rhythm issue atrial fibrillation rose 22%, sales of cardiovascular products were up 15%, and sales of neuromodulation devices soared 40%. In all cases, growth was higher when the dampening effect of foreign currency is excluded.

The company said the dollar's strength compared with the Japanese yen will hurt 2009 financial results more than previously thought, and it decreased its full-year sales forecasts for atrial fibrillation and cardiovascular products to account for this effect.

But guidance was modestly improved for heart-rhythm and neuromodulation products, and the net result was a new full-year sales forecast of $4.71 billion to $4.87 billion. The top end of that guidance came down a bit from the forecast made in January.

The full-year earnings guidance remains the same at $2.48 to $2.54 per share, which compares with Wall Street's $2.51 a share estimate.

For the second quarter, St. Jude forecast earnings of 62 cents to 64 cents. Analysts expected 64 cents.

-By Jon Kamp, Dow Jones Newswires; 617-654-6728; jon.kamp@dowjones.com

(Mike Barris contributed to this report.)