Heart rate 40-50 bpm results from stress test, echocardiogram, ekg, 24hr holter monitor all "normal" could my slow heart b due to genetics/other factors?

The "Brady Bunch": I make the odd reference above simply to highlight that a heart rate slower than 60 docs refer to as "bradycardia". As long as you don't have any symptoms, we usually aren't terribly aggressive treating it...Especially in a young person. For example, most endurance runners or young athletes have a resting heart rate below 60...Higher stroke volume = less beats per minute. That's a good "brady".

Heart rate: Asymptomatic heart rate of 40-50 BPM can be normal for an individual if normal sinus mechanism.