Cardiac Rhythm Management
Articles Articles 2013 June

Subtotal Separation of Implantable Cardioverter-Defibrillator Header from the Casing Mimicking An Atrial Lead Fracture


1 Regional Cardiology Associates, Sacramento, CA
2 Mercy Heart & Vascular Institute, Sacramento, CA

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Dr. Aryana reports he has received consulting fees from Biotronik and Boston Scientific. He has also reported that he has received consulting fees along with speaker honoraria from St. Jude Medical. Dr. O’Neill has reported he has received consulting fees from Boston Scientific and speaker honoraria from St. Jude Medical.
Manuscript received March 29, 2013, Final version accepted April 18, 2013.

Address correspondence to: Address correspondence to: Arash Aryana MD, FACC, FHRS, Regional Cardiology Associates and the Mercy Heart & Vascular Institute, 3941 J Street, Suite #350, Sacramento, California 95819. E-mail:

A 76-year-old man received a dual-chamber implantable cardioverter-defibrillator (ICD), implanted subpectorally for recurrent sustained ventricular tachycardia in the setting of ischemic cardiomyopathy and tachy–brady syndrome. Seven years later, the ICD reached elective replacement indicator and was replaced with a Boston Scientific Teligen model. A routine ICD interrogation 18 months later revealed intermittent loss of pacing capture at maximum output in conjunction with an elevated lead impedance >2,000 ohms ( Figure 1 ). P-wave sensing was generally stable and there was no evidence of noise or artifact on the intracardiac recordings with or without pectoral manipulations. All other parameters were within normal limits including stable R-wave sensing, ventricular pacing threshold (0.7 V @ 0.5 ms) and pacing and shock impedance. As a result, a fracture in the atrial lead conductor was suspected. In view of the patient’s need for atrial pacing, he was referred for a lead replacement. However, at the time of the procedure, a preliminary inspection of the ICD header revealed subtotal separation from the casing. Furthermore, examination of the atrial lead showed normal sensing, pacing threshold, and impedance as confirmed through the analyzer. Thus, the ICD generator was replaced instead, which rectified the abnormal atrial lead findings.

In December 2009, Boston Scientific Corporation issued an advisory reporting that mechanical stress associated with subpectoral implantation of Teligen ICDs or Cognis cardiac resynchronization therapy-defibrillators (CRT-Ds) may weaken the bond between the header and the casing.1 Since then, several reports have demonstrated that this rare complication can present with fluctuations or abnormal increases in multiple, ventricular, or shock lead impedances usually associated with non-physiological noise on the intracardiac electrograms.2–4 However, as illustrated by this case, this unusual complication may also simply manifest with lone atrial lead abnormalities such as elevated pacing threshold and impedance mimicking a lead fracture.


Figure 1: Right panels, illustrate the ICD intracardiac recordings showing sinus rhythm free of noise or artifact with relatively stable P-wave sensing but elevated atrial lead impedance >2,000 ohms. However, the ventricular lead parameters are within normal limits including stable R-wave sensing as well as pacing and shock impedance. Left panels, illustrate images obtained intraoperatively showing subtotal separation of the ICD header from the can. Intraoperative evaluation of the atrial lead through the analyzer revealed normal lead sensing, pacing threshold, and impedance.


  1. Boston Scientific Corporation. Product Advisory. December 1, 2009. Accessed December 23, 2009. .
  2. Laborderie J, Bordachar P, O’Neill MD, Clémenty J. Fluctuation of atrial and ventricular lead impedances heralding subtotal separation of device header and generator in a patient with an implantable cardioverter-defibrillator. Heart Rhythm 2007; 4:218–220.
  3. Germano JJ, Darge A, Maisel WH. Weakened implantable cardioverter-defibrillator header bond: abnormality not limited to subpectoral implants. Heart Rhythm 2010; 7:701–704.
  4. Hayat SA, Kojodjojo P, Mason A, et al. Malfunction of subpectorally implanted cardiac resynchronization therapy defibrillators due to weakened header bond. J Cardiovasc Electrophysiol 2013; 24:351–355.