Q waves leads II, III, v4, v5, v6. ECG reads LVH. Went on beta blockers for sinus tachycardia. Q waves no longer on ECG. What does this mean?

It means that the. quality of one or the other (or both) EKGs is not good. Most likely your body position changed (lying vs. sitting) or leads were incorrectly placed. Heart rate could potentially make a difference as well. At your age it is not concerning in anyway and is most likely an artifact. Don't worry.