There are certain situations whereby we can accurately identify individuals who are at high risk; let me give you some examples.  In hypertrophic cardiomyopathy, people with very severe left ventricular hypertrophy, those with recurrent blackouts, a family history of multiple deaths from this condition, documentation of nonsustained ventricular tachycardia on the Holter monitor or abnormal blood pressure response during exercise testing are all at risk of sudden death.  If an individual has two of any of these risk factors, that would identify them at sufficiently high enough risk to warrant a defibrillator.  Another example would be long QT syndrome, those people with a QT interval of more than 500 milliseconds or those who are shown to have long QT type 3 are at sufficiently high enough risk to warrant a defibrillator.

When it comes to sport of course, we tarnish everybody with the same brush. We are fully aware that not everybody with any of these conditions is at the same risk of sudden death as someone else with the same condition.  There is one individual, for example, that may die at the age of 20, another individual may go to their grave at the age of 90 never knowing they had the condition.  Because we cannot always be sure about the impact of exercise per se on an individual with any of these conditions, we have a very homogeneous and conservative approach.  That is to say that any individual with any of these conditions that cause sudden death should abstain from exercise of moderate to severe intensity.