Hey ya Cindi, I have volumes of experience with heart problems just within the last year. It isn't related to my MS but I have what is called bradycardia or slow heart rate which came on within a matter of weeks and required me to get a pacemaker. The pacer works at 85% of the time meaning that my own heart beats the rest of the 15%, the pacer will only kick in when my heart gets into a slow rhythm. Well now I have been have afib and vtak and they are considering switching out the pacer for a defibrillator or ICD.
Anyway, when you have a sinus disturbance, or as you mentioned sinus tachycardia, physicians don't normally treat this rather just keep an eye on it and try to find the reasons as to why your having tachycardia. Some of those can be drug interactions due to a prescription medication, hypermetabolism, anxiety and exercise or can be way more serious like anemia, CHF, a hemorrhage, or heart muscle damage. There are many people who live with dysrhythmias everyday and manage them quite well, but you should be referred to a cardiologist to follow up on those results in any case just to be sure.