Editor’s Note: The following guest post is published with the permission of its author, Edward J. Schloss, MD, (Twitter ID @EJSMD) the medical director of cardiac electrophysiology at Christ Hospital in Cincinnati, OH.
Lessons from the Riata Recall– Part III
by Edward J Schloss MD
In two earlier posts on Cardiobrief (here and here), I have written in some detail about the St. Jude Riata/Riata ST lead recalls. In these pieces, I’ve summarized what we know about the design of these leads and their clinical performance. Ultimately I hope this updated information allows clinicians and other interested parties to make intelligent decisions regarding lead follow up and new lead model selection.
This week we’ve seen new important information that sheds additional light on the performance of Riata and Riata ST. As is often the case, new information leads to both new answers and new questions.
Accepted for publication in Heart Rhythm are two new manuscripts that reference these leads. From frequent contributor Robert Hauser and his group at Minneapolis Heart Institute Foundation comes this review of ICD lead related deaths from the FDA MAUDE database. Also accepted for publication is a prospective series of Riata and Riata ST leads that underwent fluoroscopic and electrical evaluation from Parvathaneni et al at Vanderbilt.
Hauser’s study has been previously reported on this site (20 Deaths Linked to New Problem with Riata Leads). It is notable for being one of the first Riata studies focusing on electrical, rather than structural failures. In the study, 22 (since corrected to 20 by St. Jude review) deaths discovered in the voluntary FDA MAUDE database were linked to failure of the Riata or Riata ST lead. Interestingly, nearly all deaths appear to be due to failure of the high voltage portion of the lead, and most were directly linked to insulation abrasion. This is a failure mechanism not commonly seen with other ICD leads, as noted in the article’s comparison to Medtronic Quattro Secure leads (in which failure of the low voltage conductors is the dominant mechanism). Hauser estimated that failure of the St. Jude leads had an incidence “about 9 times greater than Quattro.”
Close reading of the Hauser data raises some interesting and, at times, troubling points:
• The first manifestation of failure of Riata/Riata ST leads may be patient death. This may be due to our poor ability to detect high voltage (HV) lead dysfunction, especially with older generation ICD generators (Atlas/Epic) that do not have an automated mechanism to test the high voltage circuit. Most concerning here is the possibility that HV lead failure in this population could go undetected through even compulsively well conducted office visits and remote monitoring (case report). Only when a shock is needed to terminate the clinical arrhythmia would the dysfunction manifest itself. In a malignant arrhythmia, the end result could be patient death.
• The actual act of testing for lead failure may be hazardous. Patient #18 in the Riata lead-related death series was reported to die from ventricular fibrillation that was not terminated by a dysfunctional ICD lead. That episode of fatal arrhythmia was actually created by the high voltage lead integrity test that had been performed to assess the function of the lead. Thus, in this case the ICD and dysfunctional lead appeared to directly cause the patient’s death. Important details are lacking, but the information available is troubling.
• There are numerous mechanisms for failure of these leads. They can abrade from outside-in (such as ICD generator-lead friction or lead-lead interaction) or inside-out (due to breach of internal cables thorough their protective silicone jacket with contact to shocking coil). They may also have conductor failure as seen more commonly in other ICD leads.
• There appears to be time dependence to these lead failures. Riata average failure presentation was at average 61 months. The four Riata ST failures occurred at an average of 36 months. Recall, however that Riata has been market released 10 years compared to 7 years for Riata ST.
• Riata ST failures reported in the study appear to be all “outside-in” mechanism from external abrasion.
• There was no demonstrated externalization of lead cables in any of the deaths reported. One must recognize, however, the limitation that no systematic fluoroscopic or post-mortem lead examination was reported in MAUDE.
• The overall incidence of lead failure is not possible to report from this data given the voluntary reporting inherent in the MAUDE data. This may limit the accuracy of Hauser’s estimate of a 9-fold increase in failures compared to the Medtronic Quattro Secure lead.
In the second new manuscript, Parvathaneni et al report on lead fluoroscopic externalization and electrical failure. His co-investigator Ellis also reported at the Riata Lead Summit in January. The methodology of the new study ensures that there was some degree of overlap between these reports. Please refer to Hauser’s perspective in NEJM for a discussion and images of lead conductor externalization.
The Nashville investigators performed fluoroscopic and electrical evaluation of 87 patients with Riata (n=74) or Riata ST (n=13) leads. Patient selection was due to lead failure, need for lead extraction, proximity to device battery replacement, or patient request after counseling. They found a high incidence of fluoroscopic abnormalities (externalization or abnormal cable spacing) in both families of leads, and modeling techniques clearly demonstrated that externalization increased over time.
Riata leads had significantly more fluoroscopic abnormalities at 47% (35/74) versus 15% (2/13) in the Riata ST models. It’s worth noting that only one Riata ST had true externalization with the second showing the most modest “type I” abnormality. The authors explain that their small number of Riata ST leads reflected an institutional shift away from this lead when it was found to be associated with subacute perforations– a different and less publicized problem with the low-profile (thin) Riata ST leads.
The investigators suggest that differing lead age between these lead families might have played a role in this difference, but did not have statistical power to prove this possibility. They noted that both percentages were well above what St. Jude has reported in their registries.
Electrical abnormalities were also shown to be high in the study, both in externalized and non-externalized leads. The investigators recognize that patient selection methodology created a bias, preferentially selecting out electrically abnormal leads for the study.
Close reading of this study suggests that externalization is a clear problem with Riata and well above St. Jude industry-reported numbers. This finding serves to confirm previously reported trials (here and here).
Riata ST externalization, however, has been demonstrated less frequently and its true incidence remains in question with limited and conflicting data. New information in the Parvathaneni study showed only 2/13 abnormal leads. This stands in contrast to his co-investigator Ellis’ report at the Riata Lead Summit. In the Ellis talk, slide 43 states externalization was “Equivalent between 1580 [Riata] and 7000 [Riata ST] series” at 26% or 17/64 in their whole series. It’s difficult to reconcile these disparities, as there would almost certainly have to be significant patient overlap between these two reports. In addition, Riata ST numbers were either low or not specified in the other published externalization studies referenced above.
We are a long way from reaching the final chapter in the Riata/Riata ST lead recall story. These two new studies provide new answers and raise new questions:
• There is really no denying that we have a problem with the first generation 8Fr Riata lead. Failures of this lead have been associated with patient deaths. There are now multiple series showing time dependent breakdown of the inner core structure of this lead. Multiple reports have shown increased electrical failures.
• We are very likely underdetecting the incidence of Riata lead dysfunction in our patients. Existing lead follow up mechanisms are unable to reliably detect existing or predict imminent lead failure with a high degree of certainty. Detecting failures of the high voltage circuit in this lead is particularly difficult.
• Electrical failure and externalization of these leads is clearly time dependent as is typical of lead insulation problems (see Figure 3 in this article).. The evidence supporting this for Riata has grown stronger. It may take years before we know where we stand with all of St. Jude’s leads. The relative “youth” of Riata ST and its successor Durata make prediction of ultimate failures a difficult business.
• Due to significant limitations of the studies, we are still lacking a true measure of the incidence of these leads’ failures and externalizations. The MAUDE database relies on voluntary reporting and therefore has both numerator and denominator problems. Fluoroscopic externalization evaluations are just now getting started and we will need to see more studies before the story is clear.
• What is the best way to screen for lead failure, especially high voltage? Should we be performing hospital based lead testing with determination of lead defibrillation thresholds? Is office based high voltage lead integrity testing sufficient, or even safe?
• What is the magnitude of the problems with Riata ST? These two studies appear to show Riata ST outperforms Riata. Is this due to the newer lead’s design improvements or its younger age? Judging by the time dependence of failure of Riata failures (manifest in the 4-5 year time frame), we still don’t know yet. The St Jude sponsored prospective trial should help with this question.
• Where do we stand with the successor to these leads, Durata? There have been few troubling signals with this lead. However, given its troubled pedigree and relatively brief period of follow up, can we trust it to perform at a high level?
Clinicians following ICD patients are often faced with difficult decision points. Rarely have we been as challenged as we are today with these St. Jude ICD leads. Industry and society recommendations are only as good as the data available at the time that they are made. Based on this new data, I plan to take the following actions in addition to the current industry and HRS recommendations:
–I think all St. Jude leads should have some assessment of the integrity of their HV circuit. For older Atlas/Epic ICD generators, that will mean performing a high voltage integrity test. This might best be performed in the hospital with defibrillation backup considering the MAUDE case discussed above. In newer ICD generators I will carefully review the automated lead impedance trends. In suspected, but not proven HV failure and at device replacement, I will likely perform hospital-based defibrillation threshold testing.
–I am not performing routine screening fluoroscopy at this time. Fluoroscopic examination of the lead at generator replacement, however, seems like a good compromise. Whether to replace externalized, but electrically intact leads is not clear based on available data. These will be addressed on a case-by-case basis.
–I have chosen not to implant Durata leads. Alternative ICD leads with longer track records and less problematic pedigrees are currently available. Based on my detailed literature review for a 2010 HRS debate, I do not feel there are demonstrated advantages to downsized lead caliber, which is this lead’s main differentiator from its competition. I sincerely hope Durata is proven to have robust long-term performance. It will be years, however, before we know if this proves to be the case.
Dr. Schloss has research relationships with Biotronik, Boston Scientific, Medtronic and St. Jude Medical. He has consulting relationships with Boston Scientific and Medtronic. Dr. Schloss acknowledges the assistance of Dr. John Mandrola in the preparation of this article.