Three surgical patients in Los Angeles County have developed a potential heater cooler bacterial infection after undergoing open-heart surgery.

According to a Feb. 1 press release from the Los Angeles County Department of Health, officials have confirmed three cases of Mycobateria chimaera infection in patients with a history of open-chest heart surgery.

A fourth case of heater cooler bacterial infection is suspected but yet to be confirmed as of the date of the press release.

M. chimaera is a slow-growing, non-tuberculous mycobacterial infection. These bacteria can cause post-surgical infections that do not appear until months or even years after surgery. In the most severe cases, these infections may be fatal.

Tracing the Source of a Heater Cooler Bacterial Infection

The surgical device that has been implicated in many such infections recently is the Stöckert 3T heater-cooler system made by LivaNova. Previous versions of this device were manufactured by German company Sorin Group before it merged with LivaNova.

The Stöckert 3T is used during open-heart surgery to control the patient’s body temperature. It keeps the patient from becoming too hot or too cold by circulating temperature-controlled water through other devices like heat-exchanging blankets.

The water in the Stöckert 3T is contained inside a closed circuit, so it can’t contact the patient during surgery. However, researchers believe other parts of the machine may harbor mycobacteria that can get to the patient during surgery.

These bacteria may colonize inside of the machine, then be blown out through the machine’s exhaust system and into the air of the operating room. From there, they can make their way to the open surgical wound on the patient’s body.

These machines are in widespread use throughout the U.S. and the world. Over 250,000 heart bypass procedures are performed every year in the U.S. that use a heater-cooler device. Of those, about 60 percent use the Stöckert 3T system.

Investigators have reported finding evidence of M. chimaera bacteria at the facility in Germany where the 3T system was manufactured.

According to an FDA alert, machines manufactured prior to September 2014 may have been contaminated during manufacture. Machines manufactured since then have also tested positive for M. chimaera.

As of October 2016, more than 70 cases of heater cooler bacterial infection had been documented around the world.

That same month, the Centers for Disease Control issued an alert about the issue, warning patients and care providers about the risk of infection associated with the Stöckert 3T. The CDC and the FDA followed up in November 2016 with instructions to care providers about how to address the risk.

L.A. county health officials caution that the risk of infection is very low, even for patients directly exposed to a contaminated device or who were operated on at hospitals where a previous heater cooler bacterial infection was documented.

The county health authority says it is in touch with all hospitals in the county that use this device to determine their compliance with CDC guidelines.

While officials did not identify the hospitals where the infected patients’ procedures were performed, they say they have been working with those facilities to increase surveillance and to implement controls.