Letter by Suri and Keller Regarding Article, “Annual Rate of Transvenous Defibrillation Lead Defects in Cardioverter-Defibrillators Over a Period of >10 Years”
To the Editor:
The high failure rates of transvenous defibrillation leads in implantable cardioverter-defibrillators reported by Kleemann et al1 are quite disturbing. This article raises many issues about lead design, implantation techniques, and follow-up.
First, the electrophysiology community craves leads with small diameters. This preference may have a negative impact on lead durability. Polyurethane, which is used to produce smaller leads, is more likely to degrade prematurely. Kleemann et al make the case for reevaluating the design of smaller leads. Although the poor performance of older leads is concerning, they had a better survival rate than newer models. The authors speculate that “the better survival of the Medtronic 6936 or 6966 is partly a result of the larger diameter.”
In addition, smaller leads appear to be associated with an increased incidence of perforation.2 Transmission of greater force per unit area and increased torque at the tissue-lead interface may result in more frequent perforation. Yet there seems to be continuing pressure on industry to downsize defibrillator leads. This downsizing may lead to increased complication rates and decreased lead survival.
Second, the authors stated that 95% of the leads were implanted via the subclavian vein, an approach that is associated with more lead complications. In light of this study, implanters should strongly consider using either the cephalic3 or axillary approach to limit mechanical stress, especially in patients at higher risk for lead stress. Additionally, a recent communication from a manufacturer4 suggests problems with other small-diameter leads having a higher-than-expected conductor fracture rate. In this case, their preliminary investigation suggests that “variables within the implant procedure may contribute significantly to these fractures.”
Kleemann et al also show a trend toward a higher rate of lead defects when multiple transvenous leads are implanted. It is therefore imperative that we implant the most appropriate device with the least amount of hardware. Clearly, device selection and implantation technique are critical to lead survival. The “fast-track” approach to train nonelectrophysiologists to implant defibrillators may further compound this problem.5
Finally, we believe that the study highlights the need for defibrillation threshold testing during follow-up. Basic interrogations failed to identify one third of the defects. Defibrillation threshold testing would allow measurement of shocking impedance in devices from all manufacturers. Additionally, it may provoke postshock oversensing, a sign of insulation failure. Routine defibrillation threshold testing may allow earlier diagnosis of lead failure and may reduce the incidence of inappropriate shocks.
Dr Suri has received grant support and speakers’ honoraria from St Jude Medical, Medtronic, and Boston Scientific. In addition, he has served as a consultant to St Jude Medical and Medtronic. Dr Keller has received grant support from St Jude Medical, Medtronic, and Boston Scientific.
Kleemann T, Becker T, Doenges K, Vater M, Senges J, Schneider S, Saggau W, Weisse U, Seidl K. Annual rate of transvenous defibrillation lead defects in implantable cardioverter-defibrillators over a period of >10 years. Circulation. 2007; 115: 2474–2480.
Physician information: Sprint Fidelis leads. Minneapolis, Minn: Medtronic; March 21, 2007.