Investors aren't predicting major financial fallout for St. Jude Medical in the wake of news that hundreds of thousands of batteries in its top-selling product — implantable defibrillators — are vulnerable to a rare but serious defect that leaves them unable to save lives.

St. Jude Medical stock was stable Wednesday, losing just 6 cents to close at $78.35 while the wider Standard & Poor's 500 was also flat.

But in the medical community, questions continue to swirl about whether Little Canada-based St. Jude and regulators responded quickly enough to a situation that has led to two confirmed deaths and dozens of hospitalizations. The defect with lithium batteries in St. Jude devices was first disclosed in a journal article in 2014, but the product advisory was published Tuesday.

St. Jude and the Food and Drug Administration "should have notified doctors and patients much sooner, because it is the doctor's and patient's decision as to what to do, not SJM or FDA," said Dr. Robert Hauser, a Minneapolis-based cardiologist.

St. Jude officials said the company closely studied the situation since 2014, and opted to issue its alert after it gathered sufficient evidence.

An implantable defibrillator uses electric shocks to restore a normal rhythm if a patient's heart beats too slowly or goes into sudden arrest. On Tuesday, St. Jude disclosed that nearly 350,000 implanted defibrillators it sold before a design improvement in May 2015 were vulnerable to having small globs of lithium accumulate and cause short circuits, depleting the device battery in as little time as one day.

Initially, St. Jude's medical advisory board recommended not publicizing the issue because the rate of confirmed battery failures was extremely low, St. Jude Medical Director Dr. Avi Fischer said.

"As the numbers over time increased, we got to a point of the issuance of an advisory, based on communications we had with our medical advisers, regulators, et cetera," Fischer said Tuesday.

Hauser said it was unconscionable that neither St. Jude nor the FDA spoke up sooner about a situation that led to a design improvement to address the problem on May 23, 2015. It reminded Hauser of events a decade ago, when he blew the whistle on Guidant Corp. for making a critical design change to prevent short-circuiting in its Prizm 2 DR defibrillator without telling the medical community.

"This is the same-old, same-old, and very disappointing, but not surprising," Hauser said.

One major apparent difference between Guidant's situation in 2005 and St. Jude in 2016 is the financial impact.

An investors' note from Wells Fargo Securities said Guidant lost 11 percent of the multibillion-dollar defibrillator market after its recall. In contrast, the Wells Fargo analysts modeled a 2.5 percent loss of market share in two years' time for St. Jude, which translates into a sales impact of about $143 million by 2018.

Analysts with Minneapolis-based Piper Jaffray reached a similar conclusion, based on the fact that no battery-depletion issues related to lithium clusters have been reported since the May 23, 2015 design change, and the low probability of devices needing to be replaced en masse.

"Reputation impact aside, there should be limited impact to [future] revenue," the Piper Jaffray analysts wrote. "The cost to STJ will likely then be enrolling patients not already participating in its Merlin.net remote monitoring system and the replacement cost for any failed devices."

Asked about FDA's response to St. Jude's lithium-cluster problem, an FDA spokeswoman said lithium clusters are a known phenomenon with such batteries, but they have been seen more frequently in St. Jude defibrillators compared with other devices.

"The FDA has been working directly and expeditiously with St. Jude Medical to communicate the problems outlined in the safety communication," spokeswoman Angela Stark wrote in an e-mail Wednesday.

St. Jude's product advisory warned about early depletion of lithium batteries in seven models of implantable cardioverter defibrillators and cardiac resychronization defibrillators — the Fortify, Fortify Assura, Quadra Assura, Quadra Assura MP, Unify, Unify Assura and Unify Quadra. So far, St. Jude has seen 841 prematurely depleted devices from the field that have lithium clusters, including 549 in the United States.

St. Jude has set up a website where patients can check if their device is affected by the advisory — https://www.sjm.com/en/patients/arrhythmias/resources-support/battery-advisory.

Joe Carlson • 612-673-4779