Early Techniques
Lead extraction has undergone an explosive evolution since its inception as a rudimentary skill with limited technology and therapeutic options (see Figure 1). Early techniques involved simple manual traction, which frequently proved ineffective for chronically implanted leads and carried a high risk for myocardial avulsion, tamponade, and death.1–3 Bilgutay and colleagues attempted to improve the success rate of simple traction by creating a graded weight and pulley system to deliver sustained gentle traction on the externalized portion of a lead.4 This method failed to significantly improve outcomes and suffered from similar limitations. In addition, weighted traction typically required prolonged bed rest and heightened the risk for infection. In the event that transvenous extraction proved unsuccessful, cardiotomy via median sternotomy, thoracotomy, or limited atriotomy remained a definitive solution, but at the expense of significant morbidity.5–7 The significant morbidity and mortality associated with these early extraction techniques limited their application to life-threatening situations such as infection and sepsis and, thus, stymied the development of the field.
Femoral Tools
Percutaneous catheter retrieval and removal of foreign bodies has been described since 1967.8,9 Early techniques of transvenous foreign body removal utilized catheters, wire snares, forceps, and basket retrievers with tools and technology frequently borrowed from other disciplines.10–12 Byrd utilized the lessons of these early experiences and created a femoral retrieval system that consisted of a 16Fr sheath with a hemostatic valve in combination with various snares.13 To this day, transfemoral foreign body retrieval with the Byrd Femoral Work Station® (Cook Medical) remains a necessary skill for successful lead extraction, particularly in cases where the lead is not accessible from the implant vein. The recent description of a novel technology to facilitate extraction and the maintenance of vascular access proposed a hybrid superior and inferior approach, with femoral snaring of the lead to stabilize the lead while countertraction and counterpressure are used to free the lead, reiterates the clinical importance of femoral retrieval.14
Mechanical Extraction
Telescoping Sheaths
Telescoping mechanical sheaths were developed in the 1980s to aid in the extraction of chronically implanted leads utilizing the principles of counterpressure and countertraction. Counterpressure is the pressure applied by the telescoping sheath as it dilates adherent fibrous tissue. Countertraction is the traction applied to the lead that is opposed by the force of the overlying sheath delivered to the myocardium.15 Applying countertraction limits the traction forces on an entrapped electrode to the circumference of the sheath. Once the lead is released from the fibrous tissue, the myocardium falls away from the sheath, reducing the risk for myocardial invagination and injury.16,17
Telescoping sheaths are ‘non-powered’ sheaths made of different materials with varying properties, including stainless steel, Teflon®, and polypropylene. Teflon is soft and flexible but is unable to cut through dense scar tissue, while polypropylene is stiffer and better at disrupting encapsulating scar but must be used with caution to avoid vascular injury. Stainless steel sheaths are employed only for disrupting dense and calcified fibrosis as the central venous circulation is entered.17 The inner and outer sheath pair is advanced along the lead with alternating counterclockwise and clockwise motions with moderate pressure.16 The soft inner sheath is used as a guide; the more rigid outer sheath serves to disrupt and dilate the encapsulating fibrous tissue. Sufficient traction is essential to ensure that the sheaths track the path of the lead and remain within the confines of the vasculature. Transvenous lead extraction success rates via a superior (i.e. implant vein) approach improved to 71–97% with the addition of this new extraction technique.15,18–21
Locking Stylets
The ability to successfully extract a lead with traction is directly dependent on the lead construction and its tensile strength.22 Locking stylets were developed in 1990 to reinforce the lead, transmit the extraction force to the tip of the lead, reduce the risk for lead disruption, and increase the likelihood of complete lead removal.18,20,23 Since 1990, a number of types of locking stylet have been designed. While the original locking stylets had to be sized to the lead lumen, the most commonly utilized locking stylets today are designed to accommodate a range of lead lumen diameters.
The Liberator® (Cook Medical) and Lead Locking Device (LLD®) EZ (Spectranetics) stylets offer similar support but differ in their locking mechanism design. The locking mechanism of the Liberator is at the distal tip of the stylet, providing focal traction at the tip of the lead, whereas the LLD EZ stylet grabs the lead in multiple areas and exerts force along the length of the lead.24 Applying sufficient traction to leads that could not receive a locking stylet, due to either extensive damage or a solid core design, had proved challenging until the introduction of the Bulldog™ Lead Extender (Cook Medical) in 1997. The device consists of a wire with a threadable handle through which the lead is passed and secured, thereby locking the insulation and conductor to the extender. The advent of locking stylets permitted safer and more successful transvenous lead extraction via the implant vein, stimulating the development of new techniques and technologies.
‘Powered’ Sheaths
‘Powered’ sheaths employ a source of energy to make the dissection of encapsulating fibrous tissue easier and more efficient, thus enabling the advancement of the sheath along the lead with reduced traction and counterpressure forces.22,25 One such powered sheath, the Excimer Laser System (Spectranetics), a ‘cool’ pulsed ultraviolet laser at a wavelength of 308nm, was developed between 1993 and 1999.16 The laser sheath applies circumferential pulses of energy at its distal end, dissolving tissue in contact with the tip of the sheath by photochemical destruction of molecular bonds and photothermal ablation that vaporizes water and ruptures cells with resultant photomechanical creation of kinetic energy.26 The sheath is advanced over the lead body utilising the standard techniques of counter-pressure and countertraction, and laser energy is delivered when encapsulating fibrous tissue arrests sheath advancement. Tissue in direct contact with the sheath tip is ablated to a depth of 50μ until the distal electrode is reached; countertraction is still necessary to dislocate the lead tip. In comparison with mechanical telescoping sheaths, laser-assisted extraction resulted in more frequent complete lead removal and shortened extraction times without an increase in procedural risk.26–31 The introduction of laser extraction changed the landscape of transvenous extraction, providing a highly effective and low-morbidity technique with broad applications.16,32
Shortly after the development of the Excimer Laser System, the Perfecta® Electrosurgical Dissection Sheath (EDS; Cook Medical) followed. The EDS consists of an inner polytetrafluoroethylene sheath with bipolar tungsten electrodes exposed at the distal tip and an outer sheath for counterpressure and countertraction. Radiofrequency energy is delivered between the bipoles to dissect through fibrous binding sites, much like a surgical cautery tool, although the lead tip must be liberated with countertraction.22,25,33 In contrast to the Excimer Laser Sheath, the EDS permits a localized application of radiofrequency energy with linear rather than circumferential dissection of the encapsulating fibrous tissue. The focused and steerable dissection plane offers the potential advantages of improved precision and diminished risk. The introduction of the EDS offered a cost-effective alternative to the Excimer Laser System without compromising safety or efficacy.33,34
Despite the improved success of lead extraction with powered sheath technologies, disruption of calcified binding sites remained difficult with both systems. The most recent addition to the armamentarium of lead extraction tools provides a solution. The Evolution® and Evolution Shortie Mechanical Dilator Sheaths (Cook Medical) are ‘hand-powered’ mechanical sheaths that consist of a flexible, braided stainless steel sheath with a stainless steel spiral-cut dissection tip. The sheath is attached to a trigger activation handle that rotates the sheath and allows the threaded metal end to bore through calcified and dense adhesions.35 This technology has provided an effective alternative for dealing with the challenges of densely scarred venous entry sites and heavily calcified adhesions.36
Future Directions
Transvenous lead extraction has evolved dramatically over the past 30 years and exponentially throughout the past decade. The extractor now has an armamentarium of tools and techniques with which to approach each case. Despite these advances, the basic tenets of counterpressure and countertraction remain critical to ensuring successful and safe outcomes. As indications for device therapy expand and younger patients receive devices, it is likely that the number of lead extractions performed will increase, and so too will the pressure on the field to continue to evolve not simply as a technique but also as a discipline and a science.
The recently presented 2009 Heart Rhythm Society Expert Consensus on Transvenous Lead Extraction provides several recommendations to help the specialty of lead extraction evolve. The document creates standard definitions, recommends guidelines for safe lead extraction, identifies indications for extraction, and emphasizes the importance of reporting outcomes. As new extraction tools and novel leads designed to facilitate future extraction are introduced, standardized reporting of outcomes will become essential. Data collection will serve to advance our collective knowledge and allow us to draw conclusions regarding the safety and complications of these techniques. Questions in terms of the benefits of lead extraction in specific situations remain, and a nationwide database of extraction outcomes and complications will allow us to critically evaluate and rigorously answer these questions. Moreover, collaboration among those performing lead extraction will be critical to building a community of lead extractors and creating a field committed to quality. The future of lead extraction and its evolution as a discipline lies in the development of new techniques and tools, the creation of a collaborative community, and the growth of the science.