I have mild mitral valve prolapse as well as mild thickening of the leaflets and mild regurgitation of the mitral and tricuspid valves. They say its nothing-- From what I understand mvp shows up some times and at other times it doesnt when its a mild case.
I can't say for sure, but the words "slight", "trace" and "mild" often imply that something can be measured, but it has no consequence what so ever. Please be aware that the valves in the heart are passive; in order for them to close, some blood must necessarily run back (if not, they wouldn't close).
If the cardiologist told you it's not a big deal, you shouldn't worry at all. The heart is never mathematically perfect, and there are some small errors in every heart. Like a PAC or a PVC, they are not "normal" but everyone have them. The cardiologist must decide what's within normal limits and what need treatment.
The sinus tachycardia up to 170 BPM, what is the cause? I hope you don't have a constant heart rate of 170, that would be serious. If it happens during anxiety attacks or similar conditions, it's normal.