Edward J. Schloss, MD
On March 24, St. Jude Medical announced the global launch of the Optisure family of ICD leads. It’s been a while since a new ICD lead was launched, and I’m probably not the only one who was caught by surprise. I’d like to explore why this approval is important for the ICD community. First, a brief history of ICD leads from St. Jude.
FROM RIATA TO DURATA
St. Jude Medical developed its own line of ICD leads after it purchased the former ICD vendor Ventritex in 1996. The first-generation Riata lead, approved in 2001, was succeeded by the Riata ST line in 2006. These leads were distinguished, in part, by their thin diameter, permitting implantation through a 7 Fr introducer sheath. In that era, implanting physicians’ interest in a thin lead was very strong. Even the high-profile failure of the 7 Fr Medtronic Fidelis ICD lead didn’t seem to dampen that enthusiasm.
Both of St. Jude’s Riata lead families later developed problems. Reports of subacute perforation soon after implant in the Riata ST line arose in the late 2000s. A year or two later, the internal core structure of both the Riata and Riata ST leads was discovered to break down in 25% and 10%, respectively, of these leads, as evident on fluoroscopic evaluation — a process called externalization. This problem, along with noted increased electrical failures of this lead, prompted an FDA class I recall of both product lines in December 2011, in addition to intense scrutiny and discussion in the lay press, investor press, blogosphere, and academic literature.
By the time the Riata and Riata ST leads were recalled, St. Jude had already gotten approval and marketed the successors: Riata ST Optim and, later, the Durata lead. Both these leads shared design similarities with the Riata ST lead, but additional modifications were intended to prevent the failures that the predecessor lines had exhibited. To mitigate the perforation risk specifically, changes in the Durata lead were intended to minimize tip pressure to the myocardium. And both new leads had a new insulator wrapping around the silicon core from Riata ST. This Optim insulation, shown to be more resistant to abrasion, has apparently been successful at preventing the fluoroscopic externalization that had occurred with the earlier leads.
The failure of the Riata leads has been shown to be time-dependent, so the device community has expressed some concern about Durata’s future performance. In addition, FDA has continued to apply pressure, with a January 2013 warning letter about this lead, specifically noting problems detected during a California plant inspection. Early active registry studies of Durata have been highly favorable, but a limited number of Durata problems have been discussed in case reports. Noted ICD critic Dr. Robert Hauser has also reported on a series of Durata failures from the FDA MAUDE database.
INSIDE THE DURATA
The Durata and Riata ST may share some failure mechanisms. In particular, the Swerdlow case report revealed inside–out abrasion under the distal shocking coil, resulting in a short between that coil and the ring-electrode cable, and consequent oversensing. Swerdlow and the Hauser MAUDE study have suggested that a similar form of insulation failure at the proximal shocking electrode could result in failure to defibrillate. (Because Durata and Riata ST have essentially the same internal design and materials at the level of the shocking coils, it is possible that this failure mechanism will occur with the newer leads.)
Moreover, Swerdlow found evidence of disruption of the Optim layer, which he hypothesized was due to Optim degradation, possibly related to hydrolysis of the polymer and cyclical stresses during the 4 years of lead service. The long-term biostability of Optim is critical, because without the Optim layer, the Durata leads are quite similar to Riata ST.
St. Jude has staunchly defended Durata, citing the favorable active registry data and additional testing in a large bibliography on its website. The company’s independent engineering analysis concluded that Swerdlow’s lead was damaged externally as a result of the extraction tools, not Optim degradation (counter to Swerdlow’s assertion).
THE BASICS ABOUT OPTISURE
St. Jude released Optisure this week, its first new ICD lead line since Durata. The product literature describes Optisure as “providing an additional system enhancement for addressing lead complications and improving system reliability.” The company says the slightly thicker 8 Fr lead is “for physicians who prefer a larger lead diameter.”
According to St. Jude, Optisure is built on the basic design of Durata with these additional modifications:
• 8 Fr lead body
• additional Optim insulation at the proximal end of the lead
• new layer of Optim insulation under the SVC shocking coil
FDA filings show Optisure was submitted for approval as a PMA (pre-market approval) supplement on 10/24/12 and approved for release on 02/21/14. The filing links back to the original PMA for the Ventritex TVL lead issued in 1996. It does not appear that a human clinical trial was performed, as is common in PMA supplement approvals.
MY ANALYSIS OF OPTISURE
I’m happy that ICD companies continue to pursue process improvement. If we ever reach the point when we think we have a lead that is “good enough,” that will be really unfortunate. I’ve continued to have some concerns about Durata. ICD lead failures in the Riata lines have not become evident until 4 years of use, and we are only recently accumulating large numbers of Durata leads that have been implanted that long. Fortunately, Optisure’s design attempts to directly address two of the feared possible failure mechanisms of the Durata lead.
First, the increased Optim thickness in the proximal lead is likely to diminish the can/lead abrasion in the pocket, and perhaps in areas of cyclical stress. I find it really ironic and satisfying to read St. Jude promoting Optisure “for physicians who prefer a larger lead diameter.” Back in 2010, when I criticized thin ICD leads in an HRS debate, I had a hard time getting people to agree with me. Now, going thicker is a marketing strategy. Times really have changed.
Second, the Optim layer under the proximal shocking coil should help to prevent internal shorts that could cause lead failure. This type of short, if it involves the distal high voltage cable, is especially worrisome, as it may manifest only at the time of clinical or induced ventricular fibrillation. I fear that proximal coil HV shorting may be responsible for many of the Riata and Durata lead failures and deaths documented in MAUDE database entries, such as those published by Hauser (as well as this more recent report). Having a layer of Optim between the silicone core and the SVC shocking coil should help to prevent this shorting, just as it has prevented externalization. Unfortunately, this mitigation will not change the likelihood of shorting under the RV coil (as in Swerdlow’s case) but should help overall lead reliability. St. Jude seems to feel the same way, citing Optisure’s design as an “enhancement for addressing lead complications and improving system reliability.”
WHAT’S NEXT FOR ICDs?
Getting a pacemaker or ICD lead designed, approved, and built is an enormous undertaking. The process has only become more difficult because of increasing regulatory barriers. The formerly common process of PMA supplement approval has come under greater scrutiny. ICD and LV leads that formerly might have been approved under PMA supplement now require large U.S. trials. The trials’ costs, coupled with the fear of another Fidelis or Riata debacle, appear to have stifled lead innovation. Given the development of two new leadless pacemakers (now being implanted in Europe) and the U.S.-approved subcutaneous ICD, we may be at the beginning of the end of the era of transvenous cardiac leads.
I have to agree with Zheng and Redberg that the PMA supplement process for medical device approval is problematic. The fact that leads from Riata to Optisure were approved on the basis of a dissimilar lead developed by a different company nearly 20 years ago should be ample evidence of this argument. Should Riata leads have gone through a clinical trial? Answering yes may seem logical. The unfortunate reality, however, is that no pre-market clinical trial would have picked up this lead’s late and novel failure mechanism. Even today, I would argue that careful industry engineering and close post-market scrutiny (including FDA-mandated registries) are doing far more to help our ICD patients than any pre-market trial ever could.
Nevertheless, it is critical to improve existing products, especially ICD leads. Most of us agree these are the “weak link in the chain.” I fear that a more highly regulated environment is having the paradoxically adverse effect of forcing us to settle with what we already have. That’s why I tweeted on March 24 that the quick approval of Optisure “both surprises and pleases me.” I wonder if this lead would even have been developed if it had been forced through a long, expensive clinical trial. Would that outcome have been a good thing?