Boston Scientific (NYSE:BSX) last month alerted physicians after learning of a fluke incident involving its S-ICD pacemaker, in which a patient died when the device’s memory was corrupted by radiation.
In a June letter to physicians, Marlborough, Mass.-based Boston Scientific wrote of “a single, isolated S-ICD event that resulted in a device-related patient death in May of this year.”
“Boston Scientific engineers have determined that this patient’s S-ICD repeatedly delivered an atypical amount of energy (similar to the arrhythmia induction function) because a specific memory location was corrupted by radiation within the environment. This repeated atypical energy delivery prevented S-ICD arrhythmia detection/treatment and ultimately contributed to the patient death,” according to the letter, which noted that the radiation involved in the incident was from an ionized subatomic particle such as an alpha particle, neutron, or high energy proton – although it does not appear that the deceased patient received ionizing radiation therapy prior to the event.
A three-week internal investigation in the lab, including experiments to simulate the issue, led Boston engineers to conclude that the incident was a one-off – a so-called “single event upset” involving “a change of state in the device memory induced by environmental radiation interacting with a specific memory location,” with a probability of approximately one in 300,000 over five years, the company said.
“Although this device behavior is highly unlikely to reoccur, Boston Scientific is actively developing an S-ICD software update to mitigate the effects of memory corruption by preventing atypical energy delivery. We expect software to be completed in July with submissions to Regulatory Authorities shortly thereafter,” according to the letter. “Based on information received during the investigation, it does not appear that the patient was subjected to any readily identifiable external source of ionized particles (e.g., ionizing radiation therapy) prior to the event.
“Root cause investigation of this event identified a single scenario that could lead to this behavior in an SICD. Boston Scientific engineers simulated this scenario by corrupting two specific adjacent bits of memory on representative S-ICDs within a laboratory setting. Testing demonstrated energy output similar to the arrhythmia induction function, correlating with information available from this event. Additional simulations were performed in attempts to produce this behavior and no other scenarios were identified,” Boston Scientific wrote. “It is important to note that this particular device behavior cannot occur with any Boston Scientific transvenous defibrillators or pacemakers due to differences in hardware and software.”
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