To the latter, new data from L.M. Kallinen et al confirms what we already know about the Medtronic Spring Fidelis.
But first, some background. When Medtronic released the ultra-thin Sprint Fidelis lead several years ago, it was considered a boon for surgeons who had to constantly struggle to thread leads from an implanted defibrillator, to the heart. Defibrillators work much the same way as a pacemaker does, only at a higher complexity. The defibrillator constantly monitors the performance of the heart via the lead, which connects the two. If, and when the heart is found to be erratic and requires a stabilizing jolt, the defibrillator senses the issue and sends a life-saving impulse to the heart.
Here's the problem: the super-thin Sprint Fidelis lead, which surgeons thought was a godsend as they were easier to thread through to the heart, has been found to be prone to fracture. In other words, the lead could be too thin. Critics have suggested that not enough thought was given to such a thin lead surviving the rigors of the human body, which can sometimes be an unfriendly place. Thicker leads may have been a pain to install, but at least they were more robust.
Leads were found to fracture usually within three years after implantation—and such a fracture could cause a myriad of problems. The most obvious would be the inability of the defibrillator to sense a problem with the heart, given the failure of the lead to transport the vital information. Thus, the defibrillator would not have the capacity to successfully deliver what often is a life-saving impulse to the heart.
On the other hand, a fractured lead could result in incorrect information being fed to the defibrillator, which in turn would deliver jolts to a heart that didn't need the jolt. In this way there have been cases where well-performing hearts have been administered shocks for little or no reason, with far graver consequences than simple inconvenience for the patient. Some have actually died, allegedly due to inappropriate shocks.
The L.M. Kallinen et al study at the Minneapolis Heart Institute Foundation, appears to back this up. The researchers wanted to determine if impedance monitoring might prove effective in detecting Sprint Fidelis lead failures before they caused what were described as adverse clinical events. Various data, and features of the implantable defibrillator were utilized.
The result was that between September 2004 and February of this year 17 out of 514 Sprint Fidelis leads, or 3.3 percent, failed between 11 and 35 months after implantation. Fifteen of those failures, or 88 percent, were found to have been caused by pace-sensor conductor fractures, while 2 failures (12 percent) were caused by high-voltage conductor defects.
The researchers go on to report that 15 of such failures (80 percent) with pace-sense conductor fractures received inappropriate shocks, and concluded that impedance monitoring did not prevent inappropriate shocks in two-thirds of the patients studied.
"Thus, pace-sense conductor impedance monitoring as currently implemented does not reliably forewarn patients of a lead malfunction," wrote L.M. Kallinen and colleagues.
"Consequently, patients who have Sprint Fidelis leads remain at risk for adverse clinical events associated with pace-sense conductor fracture."
One can just imagine the fear that comes with knowing you have a Medtronic defibrillator in your body, with a recalled Sprint Fidelis lead that could fracture and send you an inappropriate shock when you least expect it. Worse still, you may not be in a position to have it replaced until it is proven to be troublesome. That's because while the Sprint Fidelis lead is prone to fracture, not all of them do—and surgeons would be understandably reluctant to perform replacement surgery on a lead that appears to be performing adequately. That's because replacing a lead comes with a higher surgical risk, than implanting the lead in the first place. Removing a lead risks tearing the heart wall. Surgeons will therefore perform the procedure only when absolutely necessary.
It puts the patient in an unenviable position.
A patient like Lonnie Chambers, who filed a product liability complaint against Medtronic in Madison County Circuit Court in July. He received a defibrillator with a Medtronic Sprint Fidelis lead July 10th, 2005.
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The plaintiff claims the defibrillator leads were unreasonably dangerous and defective. "The Plaintiff suffered severe and personal injury as the result of the defective defibrillator and leads as well as continuing and permanent damage," the complaint states.
The suit also alleges that Medtronic is in breach of an implied warranty because the company allegedly sold defibrillators and leads that had a manufacturing defect.
Chambers' wife Doris is also seeking damages alleging her husband's injuries have deprived her of his support, society, companionship and consortium.
The couple is seeking damages in excess of $300,000 plus costs.