Rick D. Mcvenes

Anatomical and Morphological Evaluation of Pacemaker Lead Compression

In recent years, pacemaker lead failure due to compressive damage has been reported with increasing frequency. To document the mechanism of this failure, we evaluated explanted mechanically damaged leads with electrical testing, optical microscopy, and in some cases, scanning electron microscopy (SEM) In addition, we performed an autopsy study to measure the compressive loads on catheters placed percutaneously through the costoclavicular angle, as well as by cephalic cutdown. Of the 49 explanted compression damaged leads with enough clinical data for analysis, all had been placed by percutaneous subclavian puncture. Our autopsy data confirmed the significant increase in pressures generated in the costoclavicular angle for medial percutaneous subclavian catheterization (126 ± 26 mmHg) compared to a more lateral percutaneous subclavian puncture (63 ± 15 mmHg) or a cephalic cutdown (38 ± 13 mmHg) (P < 0.01). In vivo coil compression testing documented loads up to 100 pounds per linear inch of coil and a compressive morphology by SEM identical to that seen in the clinical explants. Pacemaker leads appear to be susceptible to compression damage when placed by subclavian venipuncture. When possible, leads should be placed such that they avoid the tight costoclavicular angle.

Effect of Steroid Elution on Electrical Performance and Tissue Responses in Quadripolar Left Ventricular Cardiac Vein Leads

The use of steroid elution (SE) electrode in a cardiac pacing lead is known to suppress myocardial inflammation to lower pacing thresholds (PTs). SE has been widely utilized on the distal electrode of left ventricular cardiac vein (LVCV) leads used in cardiac resynchronization therapy (CRT). However, no paired comparison in effect of SE has been studied in proximal electrodes of quadripolar LVCV leads.

Effect of insulation material in aging pacing leads: comparison of impedance and other electricals: time-dependent pacemaker insulation changes.

Background: There has been concern over declining bipolar (BP) impedance (Z) in aging polyurethane (PU) cardiac pacing leads. Subsequently, a prospective study was conducted comparing BP Z, threshold (Th), and R‐wave sensing amplitude of 55D PU‐insulated (Model 4024, Medtronic, Inc., Minneapolis, MN, USA) and silicone‐insulated (Model 5024) leads.

Implantable Cardiac Electrostimulation Devices

The history of bradycardia (too slow heart beat) goes back 300 years, but implantable pacemakers made their appearance in 1959. Since then, as pacemakers became more sophisticated, the indications for their use have expanded greatly. Today they are used to treat numerous rhythm disturbances including some forms of tachycardia (too fast a heart beat), heart failure, and even stroke (thromboembolism due to atrial fibrillation). Implantable cardioverter defibrillators (ICD) made their appearance in 1980. Today they are used to correct tachycardia, ventricular fibrillation, and even asystole (no heart beat) as well as heart failure patients. These are highly sophisticated devices made from very high reliability components.

To Cut or to Cap, That Is the Question: An Engineering Perspective

In his discussion, Dr. Parsonnet provides important guidance in the management of pacing leads that are no longer functional. There are engineering considerations that are important in order to make the appropriate choice for the patient in performing either capping or cutting. These fall into three broad categories of Electromagnetic Interference (EMI), Biocompatibility, and Future Considerations. Before discussing these areas of interest, one needs to recognize that the decision “to cut or to cap” entails a qualifying “to cut and seal or to cap” aspect. Dr. Parsonnet has made many pioneering contributions over the years to the design of pacing leads and refining the methods of implantation as technology changed. His recommendations for removing conductor wires and suturing the insulation carry implicit knowledge of lead construction and sealing the severed end. In order to properly “cut and seal” a lead, the implanter should have knowledge of the lead’s construction before proceeding to pull on the conductors to uncoil them. There are pacing lead designs that use cables rather than coiled conductors (e.g., Siemens Elema 588 [SiemensElema AB, Solna, Sweden] and Medtronic 3830 models [Medtronic Inc., Minneapolis, MN, USA]). Although not a topic of this discussion of pacing leads, many defibrillation lead models also use combinations of cables and coils. Implanters should be able to recognize when a lead has a cable conductor when choosing “to cut” rather than “to cap.” Pulling on a cable conductor may help with removal of the lead by traction, but it will not uncoil or stretch as a coiled conductor does. This is important in judging how hard to pull on an exposed conductor when attempting to remove some of the wire from the cut lead body and to assure the lead is sealed. Active fixation pacing lead designs often rely on the rotation of the conductor coil to retract the helix fixation electrode. If one chooses “to cut and seal,” whether to attempt to “unscrew” the helix should considered prior to attempts to either remove the lead, cap the lead, or to cut and uncoil the conductor and seal the retained lead body.

Programming Eccentricities of an Activity Sensing Pacemaker

The Activitrax rate responsive pacemaker system has enjoyed wide popularity but minor engineering eccentricities have occurred and have been reported. We report another unusual feature seen in Activitrax models 8400, 8402, and 8403. This feature consists of continuing in a temporary mode while a different permanent mode was programmed. These eccentricities of the programming features are not very commonly seen, however, they can be some what perplexing to the physician following the patient. These unusual features are no longer present in the newer models being manufactured.