Exam Tidbits: Lead Fractures and Pseudo Fractures

Conductor Fracture Clinical Signs

  • Rising pacing impedance.
  • Intermittent loss of sensing and/or pacing.
  • Complete failure of sensing and/or pacing.
  • Oversensing (contact potentials).
  • Source: Gradaus, Rainer, et al: ICD Leads: Design and Chronic Dysfunctions; PACE 2003; 26 (Pt. I) 649-657

Lead Fractures

  • Most information is derived from "Cardiac Pacing" edited by Kenneth Ellenbogen, specifically the chapter "Differential Diagnosis, Evaluation, and Management of Pacing System Malfunction" by Paul A. Levine, MD.
  • Levine appropriately titles the section dealing with lead fractures as OPEN CIRCUITS, as what appears to be a lead fracture may be due to other issues such as:
    • Improperly tightened set-screw.
    • Device being past its End of Life (EOL), resulting in no output.
  • Lead fractures can manifest as constant or intermittent events.
  • Even with a complete lead fracture, the ends of the wire may remain close enough for intermittent contact and capture.

Bipolar Wires

  • Inner coil (cathode) fracture:
    • Results in an open circuit.
    • No pacing or sensing occurs.
    • Reprogramming to unipolar mode will not resolve the issue.
  • Outer coil (anode) fracture:
    • Results in an open circuit.
    • Reprogramming the device to unipolar mode may provide temporary functionality because unipolar pacing makes the device ignore the anode.
  • Short circuit:
    • If the inner insulation opens due to stress (e.g., from a suture), a short circuit can occur between the anodal and cathodal wires.
    • Results in no pacing or sensing, or intermittent capture and sensing if the defect is intermittent (in unipolar configuration).

Diagnosing Lead Fractures

  1. Chest X-ray (AP and Lateral):
    • Fractured unipolar wires are generally easier to visualize than bipolar wire fractures.
    • Fractures may not always be visible on CXR, especially with bipolar leads.
  2. Device-based electrograms (if available):
    • Look for make/break signals, which indicate intermittent contact.
    • Look for total signal drop-out.
  3. Caution with Provocative Testing: Be very careful with provocative testing using arm and/or shoulder motion, as an intermittent fracture could become a complete fracture, potentially leaving a device-dependent patient with no rhythm.

Usual Sites of Transvenous Lead Fracture

  • Site of venous entry: 40%
  • Between the site of venous entry and the generator: 28%
  • Close to the lead insertion into the generator: 23%
  • Intravascular: 7%
  • Source: Alt E, Volker R, Blomer H. Lead fracture in pacemaker patients. Thorac Cardiovasc Surg 1987; 35:101-104.
  • Lateral and Posteroanterior chest X rays 3 months after implantation showing complete transection of the ventricular lead. The proximal end of the distal segment migrated to the right pulmonary artery (arrow).

Pseudo Fracture

  • Pseudo fractures are not limited to ICD leads; they can also be observed in some bifurcated bipolar pacing leads.
  • Pseudo fractures are apparent discontinuities of the coil commonly seen on chest x-ray.
  • The images presented show examples of normal leads that may appear damaged.
  • Left image source: Camos, Jean Pierre, et al; PACE 1999; 22:1704. Pseudofracture of an ICD Lead.
  • Right image source: Kratz, John M. et al; PACE 1995; 18:2225-2226. Pseudo Fracture of a Defibrillating Lead.