Prevalence is 200 per 100k so you’re almost certainly not affected. If you want to be sure a routine ECG and a trans thoracic ultrasound usually is sufficient to diagnose / exclude cardiac myopathy. 23andme doesn’t even look at the whole genome, they just look for common disease associated polymorphisms. No way of telling if you have a mutation that’s not in their database and even if you have a mutation it could be deactivated epigenetically or other factors could lead to you not suffering the disease.