I have a lot of back pain and was prescribed Cyclobenzaprine. I am nervous to take it b/c I am starting to wonder if I have an underlying heart problem. At times it feels like my heart is racing and pounding out of my chest. Sometimes my chest has a dull ache like pain that lasts for hours, but it not too bad. I have a family hx of heart attacks and I think I am nervous. My doctor said he didn't think there was a reason to pursue any heart diagnostics. I am a 30 yo, non-smoker, non-drinker, overweight (5'9" 213 lb), female, who walks 2-4 miles a day. What do you think about me taking Cyclobenzaprine for my lower back pain?