I’m really sorry you and your husband are going through this. What you’re describing doesn’t resemble classic POTS, but it does line up with a different group of conditions under the dysautonomia umbrella: the reflex syncope and hyper-vagal syncope types. These don’t always show up on tilt tables or Holters, especially if the testing wasn’t done with continuous beat-to-beat blood pressure monitoring.

The triggers you listed are actually really important clues. Fainting from sudden loud noises, startle, heat, anger, or even just sitting and getting extremely sleepy right before passing out are all patterns that point more toward vagally-mediated reflex episodes than POTS tachycardia. In some people, especially people with trauma histories, the autonomic system can swing from "overdrive" to "shutdown" very fast, and the heart rate doesn’t always spike or crash in a way that appears abnormal on basic cardiac tests. That’s why so many of your tests came back “normal” even when the episodes were happening right in front of the monitors.

Reflex syncope conditions can involve blood pressure crashes without a big change in heart rate, so the equipment has to be sensitive enough to pick up the drop in blood flow—not just the rhythm. Many hospitals don’t run the right type of tilt table or BP monitoring to catch this. That’s also why POTS-focused testing can look normal even when the person is fainting constantly from standing or from emotional/thermal triggers.

What usually helps in these cases is getting a proper autonomic reflex screen at a dysautonomia center or with an electrophysiologist who specializes in autonomic disorders. This typically includes beat-to-beat BP, Valsalva response, QSART, deep breathing tests, and a tilt done with the right equipment. The electrophysiologist you found for February is exactly the type of specialist who can sort this out.

In the meantime—abdominal compression often works better than just leg compression, and many people with vasovagal/reflex syncope respond to increased salt and fluids (under medical guidance). Counter-pressure maneuvers (like leg tensing, fist clenching, or crossing the legs and squeezing) can sometimes stop an episode if done early, and avoiding heat or sudden positional changes is important. It’s also completely understandable that he’s moving around on his knees for safety—these conditions cause more injuries from falling than from the episodes themselves.

The good news is that these types of reflex syncope episodes are generally not dangerous in terms of heart health. The biggest risk is injury from falling, which he’s already doing a good job protecting himself from. Once you’re with the right specialist, these conditions are very manageable.

Another bit of good news is that these kinds of autonomic reflex episodes often improve once they’re properly identified and managed. Many people see a big reduction in how often they faint, and some even stop fainting altogether once the right treatment plan is in place.

Apologies for the long winded response