<s>[INST] I m 58 yrs old and since Oct. my heart rate has been very fast. This has caused me to sound as if I m having problems breathing. My pulse/ox is always 98-100 but my heart rate can go from resting, 120 to more then 150 after I walk about 500 feet. I have a lot of pain issues and also narcolepsy and auto ammune problems. [/INST] Fast heart rate and narcolepsy are not necessarily related in any specific way except possibly as side effects to medications that are sometimes given to treat the disorder. The other symptoms that you mention including pain issues and other problems with autoimmune diseases may be more responsible and more related to your symptom of fast heart rate or tachycardia. My recommendation therefore, is that you seek out either a primary care physician or cardiologist to review your cardiac symptoms to make sure that these have been documented and are being appropriately ad Chat Doctor. If this information has been a value to you would you take a moment to provide some written feedback as well as giving the answer a star rating. Many thanks and have a nice day. </s>