Alison,
I too have an increased heart rate that started around the time my RSD spread into my chest wall. I started having runs of SVT (Supraventricular Tachycardia-a very rapid heart rate) and also low blood pressure. My cardiologist ran all kinds of tests and luckily did not find anything wrong with the heart itself. After all the tests came back ok he determined that the RSD was affecting my heart rate and blood pressure. I wish I could explain it the way he did but it all has to do with the sympathetic nervous system and the nerves that innervate the heart. I am now on medication to keep my heart rate lower. I pray all goes well for you when you see the cardiologist. Keep us updated.
Cricket