St. Jude Medical in Little Canada is one the world’s elite makers of advanced pacemakers and implantable defibrillators, but its share of the market for heart devices may come under strain as it plunges into a complex acquisition with much larger Abbott Laboratories in Illinois.

“I think both Boston Scientific and Medtronic are licking their lips in terms of potential market share that could come up for grabs,” Piper Jaffray analyst Brooks West said after separate earnings calls Wednesday from St. Jude and Abbott that revealed no new details about the pending tie-up, like who will run the combined med-tech business.

Competitors Boston Scientific and Medtronic are already taking market share from St. Jude, as both have Food and Drug Administration approval to sell pacemakers deemed safe for use in MRI (magnetic resonance imaging) scanners. Medtronic also has an MRI-approved implantable defibrillator, which St. Jude and Boston Scientific are still pursuing.

St. Jude reported Wednesday that sales in its largest division, traditional cardiac rhythm management (CRM) devices like pacemakers and defibrillators, declined by a currency-adjusted 7 percent in the previous three months, to $395 million.

“Similar to past quarters, our CRM business was challenged,” CEO Mike Rousseau told investors. He reiterated his past comments that St. Jude expects to quickly regain its lost market share when its MRI-safe pacemaker is approved for U.S. sales later this year, and its MRI defibrillator is approved next year.

Abbott’s $25 billion acquisition of St. Jude is scheduled to unfold in the middle of that timeline, creating the potential for senior management turnover at a time when St. Jude will need tight focus to regain lost ground in heart-rhythm devices.

Executives with both companies said Wednesday the deal is still on track to close by 2016’s end, as originally scheduled. The companies recently disclosed they had received requests for more information about the deal from regulators at the Federal Trade Commission, but the request is not being perceived as a threat to the acquisition.

Abbott, whose largest division is comprised of nutrition brands like Pedialyte and Similac, posted $1.37 billion in sales in its medical devices division in the most recent quarter — not far from St. Jude’s total sales of $1.56 billion in the quarter that ended July 2. Its shares rose 2 percent Wednesday, to $42.65. St. Jude rose 1 percent, closing at $81.24.

Executives with both companies, while mum on any new details, affirmed their continued confidence: “I’d say, with regard to St. Jude, everything is tracking well. We still hope to close that before year-end,” Abbott CEO Miles White told investors Wednesday.

Jeffrey Loo, an analyst who covers both companies for S&P Capital IQ, said he wasn’t too surprised at the lack of additional details about a deal that is still several months away, including who will run the combined device business. But it’s unlikely that job would go to someone at St. Jude, he said.

“I would be surprised if they elevated someone at St. Jude to run that division,” Loo said. “There isn’t much overlap between their portfolios.”

West had a different perspective, noting that St. Jude’s senior management team has done an admirable job of holding on to market share despite challenges like competition with MRI-safe heart devices and St. Jude’s 2010 worldwide recall of Riata defibrillator leads. Letting the St. Jude management team leave the company during the transition could put St. Jude at “significant risk” of eroding sales, he said.

“These guys have really been able to hold it together through some storms,” West said. “If those guys were to leave, that would be a question mark. Or a red flag.”

White told investors that the division would probably be run by a “balanced mix” of Abbott and St. Jude executives.

In its quarterly earnings report Wednesday, St. Jude met analysts’ estimates to the penny, with adjusted diluted earnings per share of $1.06 during the three months that ended July 2. That EPS represented 3 percent growth over the comparable year-ago quarter.

St. Jude’s adjusted net income for the quarter was $305 million, which represented 4 percent growth after excluding the impacts of acquisition-related costs and amortization of intangibles.

Looking at revenue, St. Jude’s $1.56 billion in sales was $12 million above the analysts’ consensus forecast.

That was an 11-percent increase over St. Jude’s sales in the same quarter last year, but only 2 percent above the year-ago revenue after factoring in how much was earned last year by Thoratec Corp., a heart-device company that St. Jude acquired last fall.

Sales of St. Jude devices to treat heart failure declined by 1 percent to $384 million in the quarter. But that was offset by other gains, including 20 percent growth in the neuromodulation division ($140 million in sales) and 13 percent growth in atrial fibrillation devices ($324 million in sales).