Heater-Cooler Devices and Mycobacterium Chimaera

Last Updated: 18 July 2016

What are heater-cooler devices and how are they used?

Heater-cooler devices are medical devices that are used in cardiothoracic surgeries (surgeries involving the heart, lungs and other chest organs). The most common type of open heart surgery is coronary artery bypass grafting (CABG) where a healthy artery or vein is grafted (attached) to a blocked coronary (heart) artery. Another form of open heart surgery is heart valve replacement to replace a defective or diseased heart valve. 

The heating elements (red) are used to ensure the patients’ blood is maintained at body temperature during the surgery, the cooling elements (blue) are used to cool the cardioplegia fluids. These fluids are used to protect the heart during surgery.

Heater-cooler devices are operated during surgery by a perfusionist. The heater cooler device incorporates tanks that provide temperature-controlled water to external heat exchangers or to warming/cooling blankets through closed water circuits. 
Heater-Cooler Unit
Sommerstein R, Rüegg C, Kohler P, Bloemberg G, Kuster SP, Sax H. Transmission of Mycobacterium chimaera from heater–cooler units during cardiac surgery despite an ultraclean air ventilation system. Emerg Infect Dis. 2016 Jun http://wwwnc.cdc.gov/eid/article/22/6/16-0045_article 

What types of heater-coolers are used in Ireland?

In Irish Hospitals, the heater-coolers used have been purchased from two manufacturers: Sorin / LivaNova and Maquet. Of the nine cardiothoracic surgical centres in Ireland, Sorin / LivaNova devices are used in four with Maquet devices used in the remaining seven. Two centres have devices from both manufacturers.

What is the link between heater-cooler devices and the organism Mycobacterium chimaera?

A number of EU countries have reported a small number of cases of infection in patients after cardiac surgery caused by an unusual organism Mycobacterium chimaera. The source of the infection has been attributed to contaminated heater-cooler units, via the production of an aerosol of contaminated water from the device. The airborne route of transmission of Mycobacterium chimaera from the heater coolers water reservoir to the patient during open heart surgery is a newly described phenomena and was not anticipated when the devices were originally designed or certified.

Mycobacterium chimaera is one of a group of common slow-growing environmental organisms that sometimes cause respiratory infections or severe disease in people whose immune systems are in some way compromised. Mycobacterium chimaera is frequently found in many day-to-day places such as soil and water. The risk of being infected during an open heart surgery is deemed to be very low. 

How is the HPRA contributing to the management of this issue?

The HPRA is actively involved in the HSE led National Incident Management and Learning Team. 

The HPRA is also working closely with other EU medical devices regulators. As the manufacturers for both the Sorin / LivaNova and the Maquet heater coolers are located in Germany, the German Federal Institute for Drugs and Medical Devices (BfArM) is Chair of a European working group established to address this issue. The focus of the working group has been to ensure that all appropriate actions are taken to maximise the safety and mitigate the risk of infections associated with these devices.   

All know cases of Mycobacterium chimaera infections to date have been linked to the Sorin / LivaNova device. The Notified Body for this medical device, TÜV SÜD Product Service GmbH Zertifizierstellen, is also based in Germany. 

The HPRA has highlighted this issue through a number of safety communications. This has included the publication and dissemination of two safety notices, one in August 2014 (SN2014-34: Heater Cooler Unit), and again in August 2015 (SN2015-23: Compatibility of Consumable Devices with Heater Coolers). Additionally, Field Safety Notices have been issued by Sorin / LivaNova. The first, in June 2015, recommended enhanced device maintenance protocols and cleaning. The HPRA confirms that the requirements of this field safety notices have been implemented in Irish hospitals. The second, in June 2016, provided guidance regarding the compatibility of Sorin / LivaNova Heater coolers with certain oxygenators and the cleaning actions relating to oxygenator mounting brackets.

Is there any information available for patients on Mycobacterium chimaera generally and the associated level of risk with surgery? 

The HSE has published an information leaflet for patients which is available to download from its website. If you have further questions about a mycobacterial infection, you can ask your doctor at your next appointment.