Medical Device Daily Washington Editor

Pacemakers and implantable defibrillators are complex enough by themselves, but add tabletop programmers to the mix and manufacturers end up with problems that Bill Gates would understand all too well.

St. Jude Medical (St. Paul, Minnesota) has to worry about something more critical than computer crashes though, and on Friday reported a patch for problems discovered in the software used to drive two of its programmers for the Identity series of pacemakers.

The software used in the APS III models 3500 and 3510 and the Merlin PCS 3650 pacemaker programmers are subject to “an anomaly in the programmer’s software [that] may lead to incorrect reporting of battery voltage, expected battery longevity and elective replacement indicator status,” the company said in a statement. These units are used to program three of the company’s Identity series pacemakers, the SR 5172, the DR 5370 and the XL DR 5376. The software versions affected are 6.1.1 and earlier for the APS units and 4.1.1 and earlier for the Merlins.

The company said it expects to have the corrected software available “within two months, pending regulatory approval.”

However, Angie Craig, St. Jude’s vice president of corporate relations, told Medical Device Daily that the firm has performed its own validation of the software fix and is awaiting the agency’s review. She added that the two-month figure is an estimate of how long the FDA might need to review the validation documents.

The company’s physician letter stresses that this problem affects “only the reporting of these measured data parameters” and that “functionality, actual longevity and battery status are not affected.” The letter also states that the company has not received any reports of adverse events in connection with the software problem, which is said to have demonstrated an incidence rate of 0.027%, or 53 field reports out of more than 199,000 devices.

According to a separate document titled “physician device advisory notice,” the software can cause the programmer to write unspecified data to “a location in an Identity pacemaker’s memory that could, under certain rare device timing conditions, have the effect of preventing the automatic daily update of internal battery status.” The advisory notes further that because this daily calculation mechanism also adjusts “the magnet rate,” any attempts at trans-telephonic monitoring may prove futile.

The regulation that governs changes to software that operates medical devices states that in the event of any changes to the code, “a validation analysis should be conducted not just for validation of the individual change, but also to determine the extent and impact of that change on the entire software system.” This includes “an appropriate level of software regression testing to show that unchanged but vulnerable portions of the system have not been adversely affected.”

Craig told MDD that she was not aware of any impending changes to the software validation regime for pacemaker programmers, but that “[a]s part of our normal continuous improvement processes we do revise our test procedures based on new information.”