Sometimes people in distress and pain are unable to communicate clearly. I hope that you only mean 'hand' and not arm or forearm. If the pain is restricted to 'hand' only, and particularly if echocardiogram is normal, it is unlikely to be because of heart ailment. You should be be relieved to know this, as your description reflects your concern for any serious cause. Localized hand pain can be because of neuro-muscular or bony causes commonly. If Neurologist and Orthopedician are unable to find a cause, it may be Somatoform Pain Disorder, for which a Psychiatrist can help you.