I agree with kenkeith, nitro can help with esphogeal pain. I have a long hx of CAD, numerous stents, heart attacks, etc. However, I was fooled by GERD pain because nitro spray took away the symptoms temporarily and went twice to the hospital this year where no cardiac disfunction was detected. My symptoms ultimately led to a recent surgery called a Nissen Fundoplication as I had extreme acid reflux. It's not easy to determine the cause of chest pain, I know from experience.
Nitro is contraindicated for pericarditis, and there would be no relief from chest pain you are experiencing with nitro. If there is no deep breathing pain, one can rule out a blood clot (pulmonary embolus) and costochodritis.
It is possible that it could be rheumatiod arthritis, but you state the doctor ruled that out! . If it were arthritis you would most likely see pain in the center of the chest or in the back where there are joints.
Lupus can effect the joints and cause chest pain and/or back pain. No relief from nitro.
Because you have relief from nitro, it is almost always associated with coronary artery occlusions, however, some esphogeal pain can be helped with nitro. I'm not aware what an echo would do to help diagnose chest pain. An echo with a stress perfusion analysis would be more helpful to locate any vessel stenosis that may interfer with adequate blood flow to heart cells.
Another problem to consider is what I was diagnosed with recently. I have had a couple of stents placed in my RCA and suffered 2 heart attacks AFTER the stents were put in. Last April I went to the ER again with what I thought was another heart attack. The chest pain were the same as with the heart attacks. The difference is I didn't notice these radiating out. These chest pains wake me from a dead sleep and I have to get up and take a nitro pill. This was diagnosed as coronary artery spasms. It took some time to convince the nurses that the pains I had were causing the monitors to go crazy. They told me it was nothing, that I had moved. After it happened 3 times they were able to see the spasms. And as with you, the nitro always works. I am now on a calcium channel blocker and that has helped. I still have them, but no where near the dozen a day I was having before. And positions do bring these on too. Take care, Ally
Perhaps the problem lies in smaller vessels no seen in an echo or angiogram. Perhaps to eliminate the possibility of ischaemia they should organise a nuclear perfusion scan. I would make the Cardiologist aware that Nitro helps the symptoms, this is a clear indicator that CAD may still be involved.