I'm no expert in anything medical, but I wonder if you're actually losing out to scoliosis, and perhaps also to a spinal stenosis that affects your Vagus nerve or your phrenic nerve. It might be worth a pokerfaced ask of your cardiologist.

They say your ECG is normal, and that's pretty much the end of it...right there. If you wear a smart watch or use a Kardia Mobile (you might find a use for one of those, probably cheaper in the case of the Kardia), and if they show arrhythmia, you can download the data from either one and send a file to their offices. My electrophysiologist accepted my Galaxy watch's depiction of my recurring atrial fibrillation at face value and scheduled me for an ablation. But what I'm intending here is for YOU to learn for yourself, and definitively, whether or not you are actually in arrhythmia when you get those sensations. If it says no, then.....................again, that's pretty much that.

Did the cardiologist mention troponin, which is an enzyme given off by damaged myocytes (heart muscle cells)?