I Have History Of Fast Heart Beat Intermitent, Been Checked

I have history of fast heart beat intermitent, been checked out in the past by cardiologist, was told more of an nuisance, but noticed as ive got older now 53;, keep myself relatively fit by walking briskly 5 miles a day, that they last longer, 30 minutes at a time, should I be concerned I hae no other medical problems ie high blood pressure??