I get this thread is older but I'm commenting in case a new parent shows up looking for similar answers. I had sudden cardiac death 16 years ago. I was out for a run. John Doe, coma for a week, loss of short term memory for a few months . . . it was dramatic but I survived. I live in Seattle but was seen by Dr Barry Maron in Minneapolis for a few years at the start (he's now in Boston and I've got a doc in Seattle.) I was confirmed with HCM (apparently, the SCA was "diagnostic." 😉 ) At the time there was a gene research project going on out of Harvard Health that I got into. They found a gene mutation. Both my kids were tested; my daughter has the mutation & my son does not. My sister and my father both subsequently tested positive for the gene.
I was non-obstructive & non-symptomatic at the time i had an SCA. I understand this is extraordinarily rare. The guidance used to be that if you are gene positive or have any obstruction, then kids should stop all sports. They are now relaxing that quite a bit. My 15 year old daughter is not an athlete (because of the guidance we received) but I ride my bicycle roughly 5,000 miles per year and am quite active (although, I'm not one of the fast kids . . . HCM evolves and heart becomes less effective at "refilling" after blood is pumped.) Guidance these days is that exercise, especially more endurance based, helps the heart "re-model" to accomodate some challenges presented by HCM and can actually improve outcomes for HCM patients (while SCA during athletics with HCM patients is actually much more rare than had been once believed.) There's a study in the American Journal of Physiology. I am a "newbie" here so cant post links but the title of the article is "Exercise in hypertrophic cardiomyopathy: restrict or rethink"