I thought some of you (especially those with children that actively participate in competitive athletics) would find the info from the following sources helpful. The first is a book that you can find at kcls.org: "The Heart of a Child: What Families Need to know About Heart Disorders in Children". Also the recent (and unfortunately titled) SeattleMamaDoc blog entry "How to Prevent Sudden Cardiac Death in Young Athletes."
Make sure you talk to your pediatricians about your child's heart health at every visit... and feel free to use our example as proof that you're not just being a paranoid parent!
And finally, if you're reading this in the Seattle area, get outside and enjoy the wonderful weather!