Keep in mind that long qt syndrome, which is the actual worry, can occur in
people with relatively normal QT intervals.
Wikipedia describes a point system that is used to diagnose people, but in some cases genetic information may be the deciding factor. To your heart rate statement, 0.5 points is given to someone whose heart rate is low for their age (in children), so I am unclear on whether speeding up your heart rate will help you stay in the study.