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Mycobacterium chimaera in a post thaw pulmonary valve homograft as a result of contaminated heater cooler unit in use during the implant surgery

 National Heart Centre Singapore, National Cardiovascular Homograft Bank, 169609, Singapore

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Date of Submission15-Apr-2020
Date of Acceptance06-May-2020
Date of Web Publication29-Jun-2020

How to cite this URL:
Heng WL, Chakaramakkil MJ. Mycobacterium chimaera in a post thaw pulmonary valve homograft as a result of contaminated heater cooler unit in use during the implant surgery. Ann Pediatr Card [Epub ahead of print] [cited 2020 Oct 24]. Available from:


Aortic and pulmonary valve homografts are the replacement of choice in complex left and right ventricular outflow tract reconstructions in children and in adults in whom long-term postoperative anticoagulation therapy is not desirable and in patients with extensive perivalvular tissue destruction due to endocarditis.[1] We report a case of Mycobacteriumchimaera (MC), detected in routine post thaw culture of a pulmonary valve homograft, prior to implantation. We believe that this is the first reported case of a homograft implicated by the use of a contaminated heater cooler unit (HCU) used during the implant surgery.

Before clinical release, the homograft was processed under aseptic conditions and all microbiological cultures were negative. The homograft was thawed inside the cardiac operating theater and a post thaw tissue culture sample was taken as per the standard operating procedure. This post thaw culture sample from the pulmonary homograft grew MC. A HCU was in use in the cardiac theater at the time of the thawing of the homograft. Later, the HCU that was used in the implant surgery was found to have been contaminated with MC.

The teenage recipient was last seen 2 years postoperation and he remained well with no evidence of MC disease. The longest time from cardiac surgery to presentation of symptoms of MC infection was reported to be more than 6 years.[2] Therefore, it is imperative that the recipient is on long-term follow-up by the implant hospital.

Since 2011, HCUs were identified as a source of MC infections in patients undergoing cardiac surgeries.[2],[3] MC is the pathogen responsible for the global outbreak caused by an exposure to the LivaNova (formerly Sorin) 3T HCUs, which is widely used in cardiac operating theaters, including all our hospitals in Singapore. Investigations confirmed that the HCUs were most probably contaminated during the manufacturing process in Germany.[2] An airborne transmission pathway can result when the MC expelled from the contaminated HCUs reach and settle on the surgical field (and homograft to be implanted) through aerosolization of water.[3]

Corrective actions of regularly cleaning of HCUs, daily change of water, and periodic testing of water cultures from the HCUs may reduce the risk of MC contamination of HCU. As a precautionary measure, our tissue bank performs Mycobacterium testing of tissues from donors who either have had previous cardiac surgeries or whose tissues are recovered in operating theater where a HCU was in use.


We would like to thank Dr. Loh Yee Jim, who alerted us to this case; A/Prof. Thoon Koh Cheng and Dr. Sng Li Hwei for their valuable insights and advices.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Heng WL, Tan JL, Lim CH, Lim YP. 3-years post-operative outcome of a recipient of pulmonary valve homograft originating from a heart transplant patient in Singapore. J Clin Case Rep 2012;2:230.  Back to cited text no. 1
Kasperbauer SH, Daley CL. Mycobacterium chimaera infections related to the heater-cooler unit outbreak: A guide to diagnosis and management. Clin Infect Dis 2019;68:1244-50.  Back to cited text no. 2
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;22:1008-13.  Back to cited text no. 3

Correspondence Address:
Wee Ling Heng,
National Heart Centre Singapore, National Cardiovascular Homograft Bank, 169609
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/apc.APC_72_20


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