Admitted to the hospital, he was found to have hypertrophic cardiomyopathy, or thickening of the muscles in the heart.

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Hypertrophic cardiomyopathy (HCM), a heart-related abnormality, is the most common cause of sudden death in young athletes at sporting events.

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The teenager, who had just signed schoolboy forms with Yorath's former club Leeds United, had an undiagnosed heart condition known as hypertrophic cardiomyopathy.

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Dr. Green is heading a new clinical trial involving 200 people, half of whom have hypertrophic cardiomyopathy and a family history of the disorder.

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Over the next five days, she remained in a medically induced coma, she told CNN, and doctors diagnosed her with a heart defect she didn't know she had -- hypertrophic cardiomyopathy.

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Among them are hypertrophic cardiomyopathy (HCM) - a hereditary condition in which there is excessive thickening in the heart muscle, myocarditis, which leads to inflammation of the heart muscle and coronary artery disease.

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Mrs Lunt, 55, was unaware her son had been suffering from an undiagnosed heart defect which can cause hypertrophic or dilated cardiomyopathy and lead to sudden death syndrome.

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