What Causes Palpitation In The Ear And Head?

I have had palpitations during the day and night which are more noticeable at night when I lie down. The palpitations go through to my ear and to the head and this is all felt on the left hand side. Sometimes I feel pressure on my back lefthand side just below the shoulder blade. I have had Heart scans etc, and the results are all good but these sympthoms continue, I do have ringing in my ears as well. What is the cause of all this.