Bos Sci rebuts HeartRhythm CRT-D case study about weak header bond
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In the study, written by David D. McManus, MD, and his colleagues at University of Massachusetts Medical Center in Worcester, Mass., a 58-year-old man with a history of non-ischemic cardiomyopathy, depressed ejection fraction, symptoms of NYHA Class III heart failure and a QRS duration of 138 ms underwent placement of a Boston Scientific Cognis N119 biventricular CRT-D. A St. Jude Medical 1688TC bipolar lead, Boston Scientific 0185 bipolar lead and a Boston Scientific 4554 bipolar lead were positioned using standard fluoroscopic views in the right atrium, right ventricle (RV) and anterolateral tributary of the coronary sinus, respectively.
“The distinct, decaying, low-frequency noise seen in this case implicates air escape from the RV port as the noise source,” according to the authors, which they attributed to the RV port seal plug as being slightly open.
“As pressure in the header equalized, escaping air bubbles and corresponding noise signals slowed and finally ended, as observed on the stored EGM,” McManus wrote. “Use of new, larger seal plugs in the Cognis N119 was intended to improve sealing performance compared with older Boston Scientific devices. Our experience suggests that recommended maneuvers for releasing pressure during lead insertion may not have been sufficient in this case to prevent air compression and leakage from the Cognis N119 CRT-D header.”
In summary, the article suggested a weakened header bond was responsible for the abnormal sensing and pacing impedance experienced by the patient.
In response, the Natick, Mass.-based Boston Scientific said: “We find it unacceptable that HeartRhythm rushed this manuscript to publication and speculated on the cause of the problem without requesting from us a detailed engineering analysis of the explanted device. Our analysis found that while the bond between the header and the case was weakened, the device functioned normally and a weakened header bond was not the cause of the abnormal sensing and pacing impedance observed in this patient.”
"X-ray analysis and electrical testing verified that the header wires were neither fractured nor otherwise damaged, and the seal between the header and the case was secure with no evidence of body fluid under the header,” the company continued. “In short, there is no mechanism to link the noise observations to a weakened header bond.”
McManus and colleagues acknowledged that a Medline review of relevant search terms did not reveal any reports of header malfunction involving the Cognis N119 device. Yet, they maintain that “attention to this potential problem is warranted given the difficulties associated with timely recognition and correction of problems with implanted devices.”
According to Boston Scientific, “Including this most recent case, only three instances of weakened header bonds have been observed in a context of more than 90,000 Cognis and Teligen devices implanted subcutaneously.”
However, the company added that it has “implemented manufacturing process improvements to strengthen the header bond on these devices, allowing physicians to implant devices in either a subpectoral or subcutaneous position.” Boston Scientific said it has received approval from U.S. and European regulatory authorities for the devices with the “strengthened header bond” and has begun shipping these devices.