Cause of Sudden Cardiac Death

Cause of Sudden Cardiac Death

Identifying risk factors of Sudden Cardiac Arrest is a relatively new field of medicine. Not a subject often found outside Medical Journals and in professional publications.  But there is important information for parents and the community to hear which will help prevent many Sudden Cardiac Deaths (SCD).

In the past, many sudden deaths have been classified as “unexplained”1. But for the past few years cardiologists and geneticists have discovered that up to 30% of the previously Sudden Unexplained Deaths (SUD) may now have an explanation 1 2.  Many of the deaths classed as “sudden unexplained” have been found to have a genetic “marker” that could have been identified prior to the patient’s death, and in many cases could have prevented the cardiac arrest that caused their death. In fact, the list of genes which may be associated with Cardiac Arrest and which result in irregular heart rhythms has grown significantly in the last few years. 3

If people carrying these genes are identified, often simple modifications to lifestyle, exercise, and diet could reduce their risk of a sudden cardiac arrest.  There are also number of over-the-counter medications and certain prescriptions which should be avoided. 4

So the challenge is how to identify people who are at risk of having a cardiac arrest before it happens.  Currently many cardiac arrests occur without warning, but until we can identify “at-risk” individuals this is going to continue to be a problem.

Automated External Defibrillators (AEDs) have helped us save many people who have experienced Sudden Cardiac Arrest (SCA).  In fact the Heart & Stroke Foundation of Canada and the American Heart Association say that the determining factor in surviving a Cardiac Arrest is how quickly a life-saving shock can be delivered by an AED. 5  Some brands of AEDs when used are able to deliver that life-saving shock more quickly than others.6

What has not been widely publicized or included in First Aid and CPR training are how to identify potential warning signs of an at-risk person. We should be aware that people who experience fainting when they engage in physical activity (usually sports), or if they experience fainting during emotional events are candidates for a visit to their GP and possible a referral to a Cardiac Rhythm Specialist. 7

Additionally, if a Sudden Unexplained Death has occurred in a relatively young person, genetically related family members should speak with their physician about cardiac testing.

It’s just not possible for our health system to test every child to see if they are carrying a gene which puts them at risk of a cardiac arrest.  But for children unusual heart rhythms may be identified because some do have warning signs. 8

Once a person who has been identified as a carrier of a gene that puts them at-risk of a cardiac arrest, or worse, a person who has experienced Sudden Death and who is identified as carrying an at-risk factor, there are important steps for genetically related family members to do.  Simple testing can be performed to identify at-risk family members, and, depending on the risk factor identified, lifestyle, exercise and diet changes can actually save the lives of these family members.

BC Children’s Hospital is a world class facility with some of the most knowledgeable doctors in the world in dealing with irregular pediatric heart rhythms.  In concert with UBC Hospital and other Heart Rhythm specialists and Geneticists around the world this group has formed a group called HiRO (pronounced “hero”) – a Hearts in Rhythm Organization which shares new research information, patient treatment options, genetic counselling and advocating for education and increased access to AEDs everywhere.

For more information about how you can learn more about Sudden Cardiac Death and preventing it here are a couple of ideas:


  1. Sudden, unexpected cardiac or unexplained death in England: a national survey ,J. Bowker,D.A. Wood, M.J. Davies, M.N. Sheppard, N.R.B. Cary, J.D.K. Burton, D.R. Chambers, S. Dawling, H.L. Hobson,S.D.M. Pyke , QJM: An International Journal of Medicine, Volume 96, Issue 4, April 2003, Pages 269–279
  2. A Prospective Study of Sudden Cardiac Death among Children and Young Adults, Richard D. Bagnall, Ph.D., Robert G. Weintraub, M.B., B.S., Jodie Ingles, Grad.Dip.Gen.Couns., Ph.D., M.P.H., Johan Duflou, M.B., h.B., M.Med., Laura Yeates, Grad.Dip.Gen.Couns., B.Sc., Lien Lam, Ph.D., Andrew M. Davis, M.B., B.S., M.D., Tina Thompson, B.Nurs., Vanessa Connell, Dip.App.Sci., Jennie Wallace, R.N., Charles Naylor, M.B., B.Chir., Jackie Crawford, R.N.,  N Engl J Med 2016; 374:2441-2452
  5. American Heart Association, Guidelines 2015 CPR & ECC, Dallas, Texas
  6. Polikaitis, Audrius, PhD, The Usability of Five Automated External Defibrillators by Minimally Trained Bystanders, University of Illinois Medical Center, Chicago, Illinois
  8. Marijon E, Uy-Evanado A, Dumas F, et al. Warning Symptoms Are Associated With Survival From Sudden Cardiac Arrest. Ann Intern Med 2016; 164:23.
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