When I lie down, my pulse rate goes to 54-58 and I feel heaviness in the middle and left of chest. As soon as I change my position to sitting or start walking, the heaviness goes off and pulse rate goes to normal i.e. 65-90. What could be this? The heaviness feeling in chest is like something stuck over there. Also, when I do little exercise or walk for quite a distance say 500 mts, my heart rate goes upto 135. ECG and ECHO both comes normal on investigation.