I was having sudden onsets of missed hearts beats or really fast heart beat with extreme anxiety. Pressure.on the chest, pain in the chest and left arm.i got my self checked from a cardiologist. My ECG, Echo and treadmill stress test are all clear. The doctor says that I have anxiety disorder. Buy the pain is real and it doesn't go away. I have pain in my back too on the left side. Like a pulled muscles. Stretching is a little difficult. I can carry weight easily. Climb stairs up and down easily. But that pain scares me.