My RHR is around 40. When my GP discovered it he ran a few tests (ECG and echocardiogram) that were all clear and then sent me to a cardiac electrophysiologist. He basically said that as long as I wasn't experiencing any of the symptoms of sinus bradycardia (fainting, dizziness, fatigue, etc) then this is just a normal heart rate for my body and I didn't have anything to worry about.