I am 70 years old. I exercise a lot. 3 zumba classes, 2 tai chi classes, 1 yoga class per week plus I like to walk around 8-10 miles per week. I have mitral valve prolapse. I have had a heart stress test and got an A+. Lately, I have been experiencing heart palpations. Am I exercising too much?
Yes any form for strain, like exercise or mental stress and many other day-to-day activities, can sometimes cause some ectopic heart beats in the case of mitral valve prolapse.  However strongly I would suggest you not stop or decrease the form of exercise which you do the benefit from it far overweight any risk.  However, if you get palpation which is distressing and any dizziness, if possible do get an EKG or if rarer 24 holder to see the type of ectopic and maybe a small dose of beta blocker (medicine) will take care of it.  Regards