The submuscular implantation location is an uncommon location to implant the devices. It is estimated that only 5% (3850) of the 77,000 devices implanted, were implanted in the subpectoral location.
From Boston Scientific's "Dear Doctor" letter:
Boston Scientific has determined that the bond between the header and case could be weakened by significant forces associated with a subpectoral implant procedure or when a device in a subpectoral position is pushed against a rib during contraction of the pectoralis muscle. A weakened header bond may alter lead impedance and introduce noise that may inhibit pacing therapy or initiate inappropriate tachy therapy. Additional mechanical stress applied to a weakened bond may eventually cause header connection wires to fracture, resulting in loss of therapy.In summary, the devices need to be followed as usual (every three months), but are not recommended for removal unless they begin to develop erratic behavior. The warranty and unreimbursed medical expenses "may" be honored in "certain geographies."
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Rate of Occurrence
The implant orientation of devices is not reported to Boston Scientific, making it difficult to provide rate of occurrence and prediction information. We have received two (2) reports worldwide of subpectoral implants with weakened header bonds. We estimate that 5% of approximately 77,000 COGNIS and TELIGEN devices worldwide have been implanted in a subpectoral location.
The following factors may also impact the risk of failure if implanted in a subpectoral location:
• Exact location of the patient’s ribs relative to the device
• Body size and/or muscle mass of the patient (risk may increase for larger/muscular patients)
• Activity level and/or occupation of the patient (risk may increase for more active patients)
For future implants:
• Boston Scientific recommends that subpectoral implantation of affected COGNIS CRT-Ds or TELIGEN ICDs (Table 1) be avoided until improvements to header bond strength are available for devices in your geography.
For affected devices (Table 1) implanted in a subpectoral location:
• Follow patient at least once every three months as recommended in device instructions for use.
• Consider advising patients to contact their physician or clinic if they receive shocks, in order to ensure timely review of associated electrograms and other device data via in-clinic or remote interrogation.
Reference: Boston Scientific's webpage with more information as well as links to the Dear Doctor and Dear Patient letters