After years of safety worries about heart pacing leads, the sun could be appearing through the clouds for St. Jude Medical (STJ), with a large trial indicating that the wires it currently sells might be safe after all. An independent analysis of registry data on 11,000 leads has backed the Durata wires. Separately, a much smaller study on the now withdrawn QuickSite and QuickFlex wires has suggested that lead failures appear not to harm patients.
St. Jude, though, appears to have had enough of wires altogether. A private company called Nanostim has just seen a minor success in initial human trials of a pacemaker that is entirely free of leads – and St Jude looks set to acquire the firm next year.
Nanostim’s pacemaker is still at an early stage, and the results reported this week come from just three of the 11 patients enrolled in a prospective, single-arm, multicentre trial called Leadless. They show that the product was successfully implanted the first time in two of the patients and, after repeated repositioning, in the third, too.
The repositioning is crucial. The entire device is implanted within the heart percutaneously, via the femoral vein, unlike standard pacemakers, which are placed surgically under the skin, usually near the collarbone. Leads to the heart are placed separately in a minimally invasive procedure. If Nanostim’s pacemaker is to be implanted without surgery, it will have to be suitable for repositioning.
The relative ease and speed of the implantation is advantageous, but it is the lack of leads itself that could be Nanostim’s pacemaker’s real selling point. The leads are most fragile and failure-prone part of a pacing system, and doing away with them could represent a real advance.
As early as Nanostim’s technology is, it is still the most advanced device of its kind. The cardiovascular powerhouses Boston Scientific (BSX) and Medtronic (MDT) are both working towards the same goal, but if St. Jude does go ahead with its hinted-at plan to buy the California company, it could get the jump on its rivals.
St. Jude has been an investor in Nanostim since May 2011, at the same time obtaining the exclusive option to acquire the company. It is expected to exercise this right at the end of this year.
St. Jude’s interest in Nanostim is understandable after all the problems it has seen with its recalled Riata family of cardiac leads (Riata lawsuits put St Jude’s heart wire sales at risk, April 8, 2013). It also recalled its QuickSite and QuickFlex wires, which have been prone to the same flaw as the Riatas: the insulation can wear away, and the exposed wires can then cause inadequate or inappropriate shocks.
There have been signs that its current line of wires, Durata, might also be subject to this flaw, as it employs the same coating. But an independent review of studies in over 11,000 wires has found a five-year all-cause mechanical failure rate of just 0.6%. The wires concerned were Riata ST and Durata leads, so the two have not been compared head to head, but such a low failure rate is encouraging. The study also found that 99.9% of the wires did not suffer insulation abrasion.
Simultaneously, a 60-patient trial of QuickSite and QuickFlex has shown something rather stranger. 45% of the patients had wires where the insulation had worn off, vastly above St Jude’s previous estimate of 4%. Of these, electrical problems developed in 26% of cases.
Oddly enough though, this does not seem to have been much of a problem; no evidence of worsening heart failure was seen in the group with the damaged leads.
The SJM CLAS trial of all St. Jude’s heart leads – Riata, Durata, Quicksite and Quickflex – is ongoing, with interim data due in a year or so. Pacing wires have been troublesome in the extreme for the Minnesota group. These positive data notwithstanding. It must long for the day when it can abandon them.