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.

Summarized question: What causes fast heart beat when suffering from narcolepsy ?