Hi,
How are you? How was your ultrasound and chest CT scan? Is there a family history of heart diseases?
Aside from cardiac pathology, other differentials to be considered include orthostatic hypotension, infection, nerve disorders, metabolic causes and other systemic diseases such as your thyroid or kidneys. In particular, postural or orthostatic hypotension is the sudden fall in blood pressure that occurs when a person assumes a standing position, usually after a prolonged period of rest. This may present as dizziness, lightheadedness, headache, blurred or dimmed vision, generalized numbness/tingling and fainting.
With complete medical history and physical examination together with your laboratory tests, other causes could be ruled out. Take care and do keep us posted.
Shortness of Breath especially when lying down could be fluid backing up into the lungs. Do you have a cough? When you are sitting up is the shortness of breath improved? Can you climb stairs without getting out of breath? If your ears, lips, or nose start turning blue you have an emergency situation. Left side heart failure produces symptoms of shortness of breath, cough, fatigue, dizziness, numbness, confusion and is very serious. Right side heart failure produces symptoms of water retention in the legs and abdomen. The echocardiogram which is the ultrasound does not always show everything. An angiogram will show what the problem is. If the problem is an clogged artery, they can put stents in, which is not that bad of a procedure and you will feel a ton better. Don't be scared of this procedure, it's really not that bad.
Hopefully, it is not your heart. I hope you find out what is causing this and you are feeling better soon. Twelve people in our family have heart problems so we have been through this a lot. Take care and keep your appointment.