Introduction

Approximately 227,000 Riata^™ and Riata ST^™ leads have been distributed worldwide since the initial introduction of the Riata^™ family of leads in June 2001. Initial reports of lead failure due to externalization of the lead conductors began to appear in 2008. Subsequently, more reports of insulation failure and conductor externalization have surfaced with a prevalence ranging from 8% to 33%. Structural failure frequently has been observed in the absence of electrical abnormalities, a finding attributed to the ethylene tetrafluoroethylene (ETFE) coating on the high-voltage and pace-sense cables. Adverse clinical consequences of electrically silent externalized cables have not been well categorized, and management recommendations remain controversial.

Case Report

A 62-year-old male with dilated cardiomyopathy (EF 30%), moderate to severe mitral regurgitation and recurrent monomorphic ventricular tachycardia, and frequent PVCs was referred for catheter ablation. He had recurrent arrhythmias despite treatment with various antiarrhythmic drugs as well as three prior ablation attempts at an outside institution with endocardial and epicardial mapping and ablation. He underwent implantation of a dual-chamber ICD in 2003 with a dual-coil Riata lead (model 1580). He had known cable externalization documented in October 2012 (Figure 1A). Transthoracic echocardiography was performed in September 2013, and revealed EF 20-25% and a small mobile vegetation or thrombus on the atrial (RA) portion of the ICD lead (Figure 1B). Following serial negative blood cultures, anticoagulation therapy with warfarin was initiated. At the time of presentation to this institution for repeat VT ablation (December 2013), the lead parameters were within normal limits (R wave 7.5mV, pacing/shock impedance 360/38Ω, capture threshold 1.25V/0.5ms). Intracardiac echocardiography (ICE) performed at the time of EPS revealed an unanticipated finding — a large, complex, mobile mass measuring 5x2cm attached to the lead (Figure 1C, Video 1). Successful termination of PVCs with ablation in the LVOT just below the left coronary cusp was performed under continuous ICE. Review of all available coagulation studies demonstrated therapeutic anticoagulation with warfarin since initiation with rare exception.

The patient had single-vessel coronary artery disease and significant mitral regurgitation. It was determined that the mass and lead could not be removed safely with transvenous lead extraction (TLE), and the patient was referred for surgical removal. He underwent successful surgical removal of his transvenous leads with right atrial mass attached to the ICD lead (Figure 2A), mitral valve repair, and single-vessel coronary bypass. Only antegrade cardioplegia was administered due to the RA mass; the atrium was opened and the mass was removed under direct vision. The SVC coil was approached from the RA and cut. The distal portion of the ICD lead was removed. The ICD pocket was opened, and the generator and proximal portions of the lead were similarly removed. Pathologic examination of the specimen revealed a 5x2.7x1cm bland, laminated, unorganized thrombus with focal chronic inflammation associated with synthetic material (Figures 2B-D). Gram stain and culture were negative for organisms.

Postoperative chest radiograph demonstrated a retained portion of the SVC coil (Figure 3A). He was taken to the EP laboratory for transvenous retrieval of the retained lead fragment (Figure 3B, Video 2). Using a 16F Byrd Femoral Workstation (Cook Medical), the fragment was grasped with a bioptome loaded with a gooseneck snare and successfully removed from the body (Figure 3C). He underwent contralateral transvenous ICD implantation. Diagnostic evaluation for a hypercoagulable syndrome was negative. He made an uneventful recovery.

Discussion 

This case report illustrates potential complications that can be observed with advisory Riata^™ leads and their extraction. Although thrombus formation in association with externalized cables has been reported,^1-3 this is the first case of massive thrombus generation despite therapeutic anticoagulation. Goyal et al² observed no change in thrombus size in the majority of cases (4/5) and one case of thrombus regression with therapeutic anticoagulation. In contrast, we observed a marked increase in the size of the thrombus in just three months despite therapeutic anticoagulation. 

Management of thrombi in association with externalized cables includes both transvenous and surgical extraction. Knowledge regarding the defibrillation coil connections is critical for complete removal of the lead. Different manufacturers have different defibrillation coil connections (Figure 3D). A proximal connection can unravel the coil electrode with traction. In contrast, a distal connection can compress the coil from distal to proximal, causing the coil to bunch and bulge. Dual connection will result in forces applied to both ends with maintenance of a stable shape. As aforementioned, not only does this have important implications for transvenous lead extraction, but also for surgical extraction. If the lead has only a distal defibrillation coil connection (i.e., St. Jude Medical Riata^™, Durata^™ and Optisure^™), and the surgeon cuts the SVC coil within the heart and then removes the remainder of the lead from the pocket, a remnant is likely to be left behind since the coil is no longer attached to the proximal portion of the lead, as is illustrated in the current case.

The management of patients with an implanted Riata^™ ST ICD lead is challenging. Clinicians are divided over the management of electrically silent leads with cable externalization, as available data surrounding the long-term sequelae of chronically externalized cables are sparse. One camp suggests that so long as the lead is electrically intact, there is no urgency to remove the lead, and the lead can either remain active or be abandoned. The other camp feels strongly that there is sufficient emerging evidence regarding the potential additional consequences of cable externalization (e.g., thrombus formation^1-3) that the lead should be extracted. Current available recommendations further confuse the issue. On August 16, 2012, the FDA recommended that patients with Riata^™ leads undergo X-ray or fluoroscopic screening (without recommendation as to the frequency of screening), yet if the lead is electrically functioning, that patients should be followed closely regardless if there is cable extrusion or not. This case illustrates that fluoroscopic imaging alone is insufficient and that the appropriate screening interval has yet to be determined. In addition, as opposed to other leads for which the major concern is electrical failure, the Riata^™ family of leads pose a mechanical risk as well. Therefore, abandonment of electrically failed Riata^™ leads may be even more problematic than the abandonment of other failed leads.

If the decision is made for lead extraction, the clinician must decide if lead removal will be performed transvenously or surgically. Data regarding TLE of Riata^™ ST leads suggest that it can be performed safely by experienced operators at high-volume centers with a complication rate comparable to published data, but that extraction of the Riata^™ ST leads can be challenging and leads with externalized cables may require specific extraction techniques.⁴ Echocardiographic screening of patients with externalized cables is not performed routinely prior to transvenous lead extraction and the presence of externalized cables has not been identified as a predictor of major complications with TLE. The thrombus attached to the extruded cables in this case precluded safe transvenous removal, and suggests that perhaps more rigorous evaluation of patients with externalized cables should be performed prior to TLE. Moreover, this case highlights the importance of understanding lead design prior to extraction, either transvenously or surgically, to limit the occurrence of predictable outcomes with the potential for morbidity.

Conclusions

Management recommendations regarding the presence of electrically silent externalized cables in the Riata^™ ST ICD lead are controversial. This case report illustrates potential complications that can be observed with advisory Riata^™ leads and their extraction. 

Disclosures: Outside the submitted work, the authors report the following disclosures: Dr. Maytin has received research grants from Boston Scientific and Spectranetics, and is a consultant for St. Jude Medical; Dr. Chinitz has no disclosures; Dr. Michaud has received consulting fees / honoraria from Boston Scientific Corp., Medtronic, Inc., and St. Jude Medical, and research funding from Boston Scientific Corp. and Biosense Webster, Inc.; Dr. Epstein has received research grants from and is a consultant for Boston Scientific, Medtronic, Spectranetics, and St. Jude Medical, and he also has equity in and has served as a board member for Carrot Medical.

References

1. Larsen JM, Theuns DA, Thogersen AM. Paradoxical thromboembolic stroke during extraction of a recalled St Jude Medical Riata defibrillator lead with conductor externalization. Europace. 2014;16:240.
2. Goyal SK, Ellis CR, Rottman JN, Whalen SP. Lead thrombi associated with externalized cables on Riata ICD leads: a case series. J Cardiovasc Electrophysiol. 2013;24:1047-1050.
3. Ricciardi D, La Meir M, de Asmundis C, Brugada P. A case of in vivo thrombogenicity of an externalized Riata ST lead. Europace. 2013;15:428.
4. Maytin M, Wilkoff BL, Brunner M, et al. Multicenter experience with extraction of the Riata/Riata ST ICD lead. Heart Rhythm. 2014;11:1613-1618.