A small group of older Boston Scientific (NYSE:BSX) subcutaneous implantable cardioverter defibrillators have an increased risk of early battery depletion, the company said this month in an advisory letter to physicians.

The Marlborough, Mass.-based company said the issue affects about 400 (0.7%) of its Emblem S-ICD and Emblem MRI S-ICD devices. Those devices have “an elevated likelihood (19% at 3 years) of an electrical component causing accelerated battery depletion,” according to the letter dated August 2019. The affected devices were made in July 2017 and are no longer on the market, Boston said.

“Because this behavior is detectable through regular follow-up care, the projected potential for life-threatening harm in this subset is approximately one in 20,000 at three years. The projected potential for life-threatening harm for all other devices (non-advisory) is approximately one in 5,000,000 at three years,” according to the letter.

The most common outcome is early device replacement; there were no other serious injuries reported, Boston Scientific said, noting that the problem can be detected via an unexpected decrease in battery capacity, or an early elective replacement indicator or end of life battery status. The devices can provide a minimum of 21 days worth of therapy after an elective replacement indication. The cumulative device survival rate at three years for the roughly 56,000 Emblem S-ICDs that have been implanted is 99.6%, the company said.

The company recommended that doctors enroll patients implanted with the affected devices in its Latitude NXT remote monitoring program and run device checks every three months. Device replacement within the 21-day window after ERI was also recommended, along with consideration of prophylactic replacement for higher-risk patients.

“Patient safety remains our highest priority. Although Boston Scientific recognizes the impact of this letter on both you and your patients, we are committed to transparent communication with our physician customers to ensure you have timely, relevant information for managing your patients,” the company said.