I have had extensive Cardio testing, worn a Halter monitor, had blood tests including TSH, never smoked. I have maintained consistent daily runs of 20 mins for 20 years, and have alw had stable weight of 118 - 124 pounds on a %foot 4inch frame. Cardiologists were not able to find any physical problem but could see that I have heart racing. They Rx d Metoprolol 25mg 9 months ago. 1 tab twice dly. I took it for 6 weeks and did not find it changed anything, yet the heart racing occurs several times a day for one year now. Should I resume the metoprolol? How long do you recommend taking it? I have never had Diabetes or heart issues. There is some family hist. of Diabetes and my slender, active mother died unexpectedly at age 60 of a Stroke caused by Brain Tumour. I am now nearly 62 and still trying to be active but usu stop due to rapid heart rate.