An Analysis of a Riata Lead Failure, Does It Relate to the MDA?
Terry Dillon, Cardiac Physiologist, St Bartholomew’s Hospital

Just over twelve months ago a patient presented for a routine ICD check in the follow up clinic at St Bartholomew’s Hospital. The system was an ATLAS DR 11 V-268 and the RV lead in situ was a RIATA ST 7040.  In 2011 a Medical Device Alert had been issued for this Riata lead model and in accordance with the recommended guidelines routine follow up had been increased to every three months.

The patient, now 41 years of age, had the ICD system implanted in 2007.  He had been diagnosed with dilated cardiomyopathy with a measured ejection fraction of 25% and the ICD implantation was offered on the basis of MADIT II primary prevention. The implantation had been successful with universally good system measurements produced and a DFT that was performed without incident. Subsequently there had been no instances of VT / VF although some episodes of paroxysmal atrial fibrillation had occurred. Both clinical and technical management had otherwise been normal up until the clinic visit in July 2013. He had also had corrective surgery for aortic coarctation.

On the visit in July 2013 all routine measurements made on the system were found to be normal with one notable exception. The HV lead measurement had dropped to < 10Ω suggesting a conduction fault within the shocking circuit. This value was found to be in both shocking configurations, namely RV coil to SVC / Can and RV Coil to Can, implying that the RV pair of coils was involved in the circuitry fault. The question that needed to be asked was if this fault was attributable to factors associated with the MDA?

MDA for Riata ST 7040

An ICD lead is made up of: a central inner coil that carries current to the distal tip of the lead so as to provide pacing and sensing facilities, a pair of conductor cables that complete the bipolar pacing and sensing circuit back to the Can, a pair of conductor cables that carries current to the RV shock coil, and a pair of cables that carries current to the SVC shock coil if the lead is dual coil. The central inner coil is surrounded by polytetrafluoroethylene (PTFE) for insulation, similarly the pairs of conductor cables are each surrounded by ethylene-tetrafluoroethylene (EFTE) for the same purpose.  PTFE allows for flexibility where as EFTE allows for tensile strength. The central coil is surrounded by silicon in which the pairs of conductor cables are set.  On later models of lead there is an added outer insulation layer of silicone polyurethane copolymer (Optim).
The MDA for the Riata ST 7040 was issued when it was found that in some of these leads the conductor cables had externalised from the main body of the lead. Inevitably there has been the potential for lead failure to occur hence the MDA, however relatively few leads with externalised conductors had had electrical failures reported. In other words despite externalisation electrical conduction has been preserved due to the tensile strength of EFTE as an insulator.

Externalised Cables Viewed with X-ray


The Situation with The Patient

Once the drop in HV impedance to <10Ω had been identified the most important thing to do was to obtain an X-ray. The X-ray showed no signs of any externalised cables or any obvious abnormalities such as subclavicular crush.  The X-ray however did show something very unusual!


Persistent Left Sided Superior Vena Cava

In normal foetal development the Coronary Sinus (initially termed the Vein of Marshall) is formed from the Common Cardinal Vein that lies in the area of the atrioventricular groove. Into the Common Cardinal Vein flow the Right and Left Pre Cardinal veins that carry blood from the upper portion of the embryo. At day 45 post conception an anastomosis connects the right and left pre cardinal veins superior to the Common Cardinal Vein and the lower portion of the Left Cardinal Vein atrophies. The residual Left Cardinal Vein becomes the Left Inominate Vein and the Right Cardinal Vein becomes the normal Right Sided SVC. A PLSVC arises when the left Pre Cardinal vein fails to atrophy and venous flow is preserved through to the coronary sinus, the left innominate vein may or may not be present.


The Relevance of the PLSVC in the Patient

At implant the PLSVC with a patent innominate vein was identified after attempted left cephalic venous access had failed. The left innominate vein was obviously present as the lead entered the RA via the right sided SVC. The PLSVC was confirmed by the access of the RA lead on the left side entering the RA via the coronary sinus. With no obvious signs on the X-ray of : breakage in the lead, subclavicular crush, tight ligature around the suture sleeve, and low shock impedance ruling out loose header screw, the default assumption was that external crush on the lead body had caused electrical shorting of the conductor coils serving the RV shocking electrode. Is it a case of the innominate vein and the rudimentary right sided SVC being narrow in size? Is it also possible that the presence of the PLSVC is incidental to the failure of the lead through external crush?

New Implantation 2013

A new RV lead needed to be implanted to replace the now defunct Riata ST 7040.  The plan was to try and avoid extraction of the Riata if possible. If no left sided access could be found then the Riata would have been extracted. Fortunately the new RV lead, a single coil Medtronic 6935M, was placed successfully through the PLSVC to the RV alongside the residual RA lead and thus the Riata lead was capped and left in situ. The patient’s comparatively young age meant that the capped Riata could be a potential problem in the future but once access for the new lead had been confirmed the grounds for extraction had thus reduced from a Class 1 extraction criteria to a class II one. The new ICD was a Medtronic Evera S DR, testing of which gave good measured parameters and a successful DFT.

X-ray of the New System with the Capped Riata


Points for Discussion

Inevitably the primary point of discussion revolves around the initial placement of the Riata lead at the 2007 implantation. The Riata RV and atrial leads ended up in their respective vascular positions because the RV lead which was inserted first fed easily through the patent innominate vein. The RA lead did not follow easily in through the same route and thus was placed via the true PLSVC. In a sense the RV lead actually followed the conventional route to the right SVC but the fact that the RA lead could not easily follow suggested that the vein was narrow.  When this case was presented by me at HRC in Oct 2013 a vote was taken as to whether the implanter took the right decision in placing the lead in situ where it had most easily accessed. The majority view was that the implanter took the right decision in settling for the easiest route, illustrating the view that the circumstances that lead to this lead failure may not be a matter of guaranteed foresight .There is literature available that states that lead insertion through PLSVC is deemed appropriate where necessary - Guenther et al (2013), but there is no data available on the incidence of lead failure in PLSVC, probably because it is a relatively uncommon occurrence. PLSVC is estimated to occur in 0.5 % of the population and occurs in 4.6 % of associated congenital heart disease cases, a point to bear in mind when considering that the patient had also been born with coarctation of the aorta.

The other question is to the nature of the hardware used at implantation. In a young patient there is the potential for the accumulation of leads in situ to build up over time due to chronic wear and tear, thus necessitating potential extraction to facilitate new lead requirements. Equally the more occasions of intervention that arise inevitably increase the potential for system infection with complete extraction following as a requirement. In a PLSVC a single coil ICD lead does have the advantage of being potentially easier to extract than a dual coil model. There is evidence available that suggests that dual coil leads offer no advantage over single coil ones in conventional situations, Aouker et al (2013), but whether an advantage can be obtained by placing a dual coil lead via the left SVC and creating an atypical vector remains a matter for discussion Vijayvergiya et al (2013).  Equally discretionary use of single chamber devices may be advantageous in some circumstances although this has to be considered against the risk of inappropriate shock therapies through reduced SVT discrimination capacity.

Points for Final Consideration

When confronted with a PLSVC, during a pacemaker or ICD implantation, it would be most likely best to take a fluoroscopic map of the vasculature and at least consider the options for positioning even if the easiest accessible route is taken over a visually preferred route. Remote monitoring is now commonly available and increased routine follow up through this medium can be considered for patients with this type of abnormal vasculature. Developing on line medical record systems will also help to accumulate and audit data on lead performance in such patients. As regards the involvement and exclusion of the Riata model MDA, it is important to know the specific characteristics of the MDA, and to keep up to date with developments and changes in recommendations that may significantly affect factions that may need to be taken.

References

• Hardey et al: Persistent left superior vena cava 1980.
• St. Jude Medical ICD Lead Design and Long-Term Performance July 2013.
• Medical Device Alert Ref: MDA/2012/061 Issued: 10 September 2012 at 11:30.
• FDA Safety Communication: Premature Insulation Failure in Recalled Riata Implantable Cardioverter Defibrillator (ICD) Leads Manufactured by St. Jude Medical, Inc 2011.
• Yasuda et al: ICD lead implantation via persistent left superior vena cava 2003.
• Guenther et al Guenther et al: Implantable cardioverter defibrillator lead implantation in patients with a persistent left superior vena cava, feasibility, chances, and limitations: representative cases in adults 2013.
• Streitner et al: Comparison of Ventricular Tachyarrhythmia Characteristics in Patients with Idiopathic Dilated or Ischemic Cardiomyopathy and Defibrillators Implanted for Primary Prevention 2011.
• Aouker et al (2013): No benefit of a dual coil over a single coil ICD lead: evidence from the Sudden Cardiac Death in Heart Failure Trial.
• Vijayvergiya et al (2013): Transvenous defibrillator implantation in a patient with persistent left superior vena cava

Further Reading

• Aguilera et al: Radiography of Cardiac Conduction Devices: A Comprehensive Review 2011.
• Mandrola J: Trials and Fibrillations Post up: St Jude Riata Lead Update 2012.
• Bissinger et al: Cardiac defibrillator implantation via persistent left superior vena cava – sometimes this approach is facile. A case report 2011.
• Biffi et al: Left superior vena cava persistence in patients undergoing pacemaker or cardioverter-defibrillator implantation: a 10-year experience.
• Sohal et al: Laser extraction of a defibrillator lead from a persistent left superior vena cava 2013.
• Ellenbogen K. A. Cardiac Pacing and ICDs Fourth Edition Ch 5 pp 246, 354.

Acknowledgements
• Professor Richard Schilling

• Dr Niall Campbell

• Dr Mehul Dhinoja

• Dr Simon Sporton

• Dr Glyn Thomas

Click here to download the editorial as a PDF file.