I had an echo done 10 years ago which came back normal. I was told my heart was healthy and I could run marathons without worrying about sudden death, but I feel like that's not enough. I keep getting couplets, bigeminy and NSVT or PSVT (not sure which, but more likely NSVT). When I was 12, I experienced something that matched numerous EKG print outs of NSVT runs separated by a sinus beat. I feel like there is something there. What tests should I get? So far, I have only had EKGs, one 24-hour Halter and one echocardiogram. I am considering asking my doctor a stress test, an event-monitor or a ZIO patch. Would a heart MRI offer any further insight?