{"id":42367,"date":"2014-03-28T07:36:04","date_gmt":"2014-03-28T11:36:04","guid":{"rendered":"http:\/\/blogs.nejm.org\/cardioexchange\/?post_type=voices&p=42367"},"modified":"2014-03-28T07:38:32","modified_gmt":"2014-03-28T11:38:32","slug":"how-sure-can-we-be-about-optisure","status":"publish","type":"post","link":"https:\/\/blogs.nejm.org\/cardioexchange\/2014\/03\/28\/how-sure-can-we-be-about-optisure\/","title":{"rendered":"How Sure Can We Be About Optisure?"},"content":{"rendered":"

On March 24, St. Jude Medical announced the global launch of the Optisure family of ICD leads. It\u2019s been a while since a new ICD lead was launched, and I\u2019m probably not the only one who was caught by surprise. I\u2019d like to explore why this approval is important for the ICD community. First, a brief history of ICD leads from St. Jude.<\/p>\n

FROM RIATA TO DURATA <\/b><\/p>\n

St. Jude Medical developed its own line of ICD leads after it purchase<\/a>d 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\u2019 interest in a thin lead was very strong. Even the high-profile failure of the 7 Fr Medtronic Fidelis ICD lead didn\u2019t seem to dampen that enthusiasm.<\/p>\n

Both of St. Jude\u2019s Riata lead families later developed problems. Reports of subacute perforation<\/a> 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 \u2014 a process called externalization<\/a>. This problem, along with noted increased electrical failures of this lead, prompted an FDA class I recall<\/a> of both product lines in December 2011, in addition to intense scrutiny and discussion in the lay press<\/a>, investor press<\/a>, blogosphere<\/a>, and academic literature<\/a>.<\/p>\n

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<\/a> 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.<\/p>\n

The failure of the Riata leads has been shown to be time-dependent, so the device community has expressed some concern<\/a> about Durata\u2019s future performance. In addition, FDA has continued to apply pressure, with a January 2013 warning letter<\/a> about this lead, specifically noting problems detected during a California plant inspection. Early active registry studies of Durata<\/a> have been highly favorable, but a limited number of Durata problems have been discussed<\/a> in case reports<\/a>. Noted ICD critic Dr. Robert Hauser has also reported on a series of Durata failures from the FDA MAUDE database<\/a>.<\/p>\n

INSIDE THE DURATA<\/b><\/p>\n

The Durata and Riata ST may share some failure mechanisms. In particular, the Swerdlow case report<\/a> revealed inside\u2013out 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.)<\/p>\n

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<\/a> 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.<\/p>\n

St. Jude has staunchly defended Durata<\/a>, citing the favorable active registry data and additional testing in a large bibliography<\/a> on its website. The company\u2019s independent engineering analysis<\/a> concluded that Swerdlow\u2019s lead was damaged externally as a result of the extraction tools, not Optim degradation (counter to Swerdlow\u2019s assertion).<\/p>\n

THE BASICS ABOUT OPTISURE<\/b><\/p>\n

St. Jude released Optisure this week, its first new ICD lead line since Durata. The product literature<\/a> describes Optisure as \u201cproviding an additional system enhancement for addressing lead complications and improving system reliability.\u201d The company says the slightly thicker 8 Fr lead is \u201cfor physicians who prefer a larger lead diameter.\u201d<\/p>\n

According to St. Jude, Optisure is built on the basic design of Durata with these additional modifications:<\/p>\n