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Malignant Hyperthermia Investigation Unit

Malignant hyperthermia (MH) is an inherited muscle condition in which sustained contractions of muscles may occur in response to specific anesthetic drugs. Affected individuals are susceptible to life-threatening reactions to commonly used anesthetics. In very rare situations, MH reactions may occur without an anesthetic. 

The Malignant Hyperthermia Investigation Unit (MHIU), at Toronto General Hospital, Toronto, Canada is one of the first centers in the world that has worked on providing care and diagnostic testing to Malignant Hyperthermia patients. It is currently the only diagnostic and research center  for MH in Canada.

Our mission is:

  • To advise and provide resources to increase knowledge of MH among Canadian health practitioners and patients.
  • Act as a referral center to assess "at risk individuals" and provide them with genetic counseling, genetic testing, and CHCT testing.
  • To create and maintain an MH registry of the Canadian MH population.
  • To perform scientific research on MH.

MHIU History

Dr. Beverley A. Britt, an anesthesiologist from Toronto, was devoted to unraveling the biochemical and genetic bases for MH and to the development of preoperative diagnosis of MHS. She started her research in malignant hyperthermia in 1966 with Dr. Werner Kalow, often described as the "father of pharmacogenetics". They were the first to take advantage of the knowledge that caffeine might be a useful tool in MH research, and noted that tension developed in MHS fibers compared to normal fibers at lower caffeine concentrations. Their research was the basis for the North American caffeine-halothane contracture test (CHCT) and the European in vitro contracture test (IVCT). Dr. Britt established a unit for further research on malignant hyperthermia and became its director. Over the years, she tested the muscles of numerous survivors and their relatives with caffeine and halothane. This unit is now known as the Malignant Hyperthermia Investigation Unit (MHIU) at Toronto General Hospital. Subsequent to Dr. Britt, Dr. Jane Heggie, and Dr. Julian Loke were directors of this unit. Currently Drs Sheila Riazi and Carlos Ibarra run the unit.

MHIU sees at risk individuals in the clinic and performs muscle biopsy and contracture testing or genetic testing if required.

 MHIU patients assessed at the clinic (rose) or who underwent muscle biopsy (green)

Education, Research, achievements and ongoing initiatives

Anesthesia residents from University of Toronto spend one day at MH unit to participate in clinic, biopsy and contracture testing. This rotation is quite popular among residents.

In last 5 years, we have had 7 summer/project students, 4 graduate students (3 masters, and 1 PhD), and 2 post-doctoral fellows. This has led to 48 publications in high impact journals, including two in Nature Communications. From our most recent research works stand out the discovery of a new candidate gene for MH susceptibility, a novel association between diabetes and calcium leak in skeletal muscle, and factors affecting the penetrance of an MH reaction. We will be hiring a new MH clinical/research fellow in July-2024.

Over the same period, our group has secured almost $7 million dollars in funding from national (CIHR) and international (NIH) agents, including a recent grant from the European Joint programme- Rare Diseases (EJP-RD) through CIHR to Dr Ibarra (PI) for a transnational project to develop a novel metabolic test in vivo to diagnose MH from susceptibility.

Our contact information is:

Toronto General Hospital, University Health Network

Malignant Hyperthermia Investigation Unit

3 Eaton North-323, 200 Elizabeth Street

Toronto, ON, M5G 2C4 Canada

Phone: (416) 340-3128; Fax: (416) 340-4960



For donation, please donate money to research in the field of Malignant Hyperthermia, you can send a cheque, payable to

"Malignant Hyperthermia Education Research Innovation Fund" to:

Toronto General Hospital, University Health Network
 Malignant Hyperthermia Investigation Unit
 Eaton North, 3rd Floor, Rm. 323
 200 Elizabeth Street
 Toronto, ON, M5G 2C4 Canada

We would be happy to issue an acknowledgement letter/receipt.

Lead Physician(s)

 Dr. Sheila Riazi