Given how St. Jude Medical (NYSE:STJ) has promoted the near infallibility of the Durata defibrillator’s lead insulation, it was imperative that executives move fast when a report emerged that cables had poked through their insulation in one patient.

That single report had caused the stock to slide 6 percent in a day.

On Friday, just 10 days after the report emerged, the medical device maker announced that it had tracked the lead down to a Florida hospital where an analysis revealed that the cause for the wires coming out of their insulation was external abrasion.

By contrast, the Riata, Riata ST leads that were recalled, and two other leads were plagued by inside-out abrasion.

A statement from St. Jude Medical went on to say:

Through our investigation, we have identified that the patient had an additional defibrillation lead that had been capped (and was no longer being used).In the fluoroscopic images, the two leads cross in the region mentioned in the filed MAUDE report. Based upon physical examination, our analysis indicates the damage to the Durata lead is consistent with external abrasion from contact with a calcified, or hardened, heart valve or possibly from lead-to-lead contact. External abrasion is a known cause of failure across all cardiac leads in the industry, which is different from the inside-out abrasion seen with externalized conductors observed in some Riata leads.

One analyst who follows St. Jude Medical believes that the mystery has been solved.

“The one unconfirmed, somewhat ‘fuzzy’ report has now become confirmed and clear,” said Thom Gunderson, a Piper Jaffray analyst in an email. “Given the reports, the most reasonable conclusion is that the Durata lead failed from outside abrasion due to circumstances, not due to inside-out extrusion due to design.”

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