Good point and well-written post! I'm not a doctor and am not trying to diagnose you, but the panic attack you describe sounds like a specific "type" that I have also had. It involves your vagus nerve getting pinched, which can happen anywhere along the nerve itself, but it often tends to get pinched around the area where the esophagus meets the stomach. The vagus nerve passes right through that same hole in the diaphragm and if your stomach pushes up or even herniates a little, the nerve can get pinched. Anyway, one symptom or result of a pinched vagus nerve, aside from severe anxiety, is that your legs feel heavy and you can also feel somewhat dizzy or like you're going to pass out. This is because an aggravated or pinched vagus nerve (and its associated anxiety) can then cause a vaso-vagal response (or vasovagal syncope). Your vagus nerve is actually trying to shut you down in response to your heightened fear and the veins (or arteries, not sure and always get those mixed up) in your legs widen, allowing blood to settle in the lower extremities. Your blood pressure drops and drains somewhat out of your head, making you feel woozy. You can even faint, but it's not life threatening... just a weird way your vagus nerve can decide to manage various stressors.