What might tingling in the back behind the location of the heart and sometime in the front indicate. I have a low pulse rate 50 -55 workout everyday, heart however is giving hard beats, off and on, no rapid beats in a row. Problem has come and gone for about two weeks seems better when exercising. Did a swim, bike tri, can t runs because of knees, Sat. and had no issues. Age 66, family history of heart problems. Mitro Valve was identified once, 15 years ago - but not found again. Issue present before but has always gone away seems to be sticking around this time. See Dr. asap or see if it continues?