Boston Scientific's Emblem S-ICDs are among the devices that will receive a software upgrade to prevent future incidents.

Boston Scientific is developing an S-ICD software update after a super rare malfunction caused a device-related patient death.

According to a recent "Dear Doctor" letter, a patient with one of the company's S-ICD (subcutaneous implantable cardioverter-defibrillator) system died after the device repeatedly delivered an atypical amount of energy because a specific memory location was corrupted by radiation within the environment. This repeated atypical energy delivery prevented an arrhythmia detection and subsequent treatment, and ultimately contributed to the patient's death, the company said.

The probability of the same thing happening to another patient is 1 in 300,000 over five years, Boston Scientific determined after its investigation of the incident. Still, the company is developing software updates for its Emblem S-ICDs and SQ-RX S-ICDs as a precaution. This problem cannot occur with any of the company's transvenous defibrillators or pacemakers because of hardware and software differences, Boston Scientific noted.

Engineers were able to simulate the device behavior in a lab by corrupting two specific adjacent bits of device memory on similar model S-ICDs. The software update would mitigate the effects of memory corruption by preventing atypical energy delivery, Boston Scientific said.

The company said the memory corruption that happened in the reported case was due to a transient change of the device's operating state, caused by what engineers refer to as a single event upset (SEU). An SEU is a change of state in the device memory induced by environmental radiation interacting with a specific memory location. 

All electronic devices that use integrated circuits are susceptible to SEUs, but implantable heart devices include mechanisms that are supposed to detect and correct memory corruption before it interferes with the device's function. This type of corruption can't always be detected though, especially if it impacts multiple bits in an area of memory that is expected to change as software performs device operations. That's what happened in this case, Boston Scientific said.

The company also noted that the patient had not been subjected to ionizing radiation therapy or any other readily identifiable external source of ionized particles prior to the incident.