I think it is not a good idea to postpone any investigation that is very important to make a diagnosis. If you fail to undergo essential investigation then invariably your doctor unable to make a diagnosis & you would not get the proper treatment.Actually shortness of breath is caused by various pathologies of lungs & heart. Right heart failure
cause shortness of breath which is aggravated by lying down position. Therefore ECG can be recognized as a one important investigation which gives clues for proper diagnosis.