Can you describe the "chest tightness"? I am wondering if it's the same as my "chest heaviness" that is one of my main symptoms of orthostatic intolerance. It feels as though there's a weight in my chest and that I need to take a deep breath (to the top of my breath).
That sounds similar indeed. It kind of feels like I'm lacking air but I also can't inhale well, as if something were pushing on my ribcage, constricting me, stopping me from taking a deep breath. As if I were out of breath after having run a 10k but unable to properly inhale. I've always attribute this to asthma, but seems like it was mainly caused by tachycardia/OI (and Mestinon should if anything worsen my COVID induced asthma).
I experienced the exact same change taking a malic acid supplement. Before the supplement, it felt like just briefly forcing myself into activity (speedwalking half a block to try to catch the bus, for example) would leave me out of breath. Like you describe, it almost felt like there was some artificial blockage that prevented my lungs from filling up no matter how deeply I breathed in. I could feel my diaphram moving so I know I was actually taking a full breath, but it didn't feel like a full breath. After the supplement, the first thing that I noticed was that it felt like my body was actually using the air I breathed in. I could keep going for way longer and at a higher intensity without ever feeling that shortness of breath or chest tightness. I never had asthma (besides one brief incident seemingly caused by a supplement allergy) and generally don't have OI symptoms. So I wonder if there's some similar mechanism between the malic acid and mestinon. Thanks for sharing! This is really interesting.
I'm not deep enough in the field to speculate about a common mechanism between pyridostigmine and malic acid. But I'm happy to hear that malic acid helps you would it have to be malic acid or would something like magnesium malate also work? Another update to pyridostigmine: As of now I can confidently say it's "cured" my symptoms. I'm at 30 mg TID and my HR while standing has reduced from 120+ to 75-85 (55-65 supine), I feel much less fatigued, no chest tightness when standing, no lightheadedness, no nothing! Got a massive boost in quality of life. Very happy I decided to take it, hope it doesn't lose too much effect over time. I guess the next steps down the line will be to slowly wean me off the other medications (midodrine, fludrocortisone, nebivolol) one by one in the following months and see if the symptomatic relief through pyridostigmine sticks or if it's a beneficial interaction between anything in this cocktail. Let's see what my cardiologist says.
Mixed POTS and OI. No "classical" dysautonomia symptoms such as GI issues or dry/watery eyes/mouth, according to my doc. What exactly is up, is probably a mystery tbh.
Did a beta-blocker help you? Propranolol 20 mg in the morning seems to help lower my HR but doesn't seem to do much else to help my OI (which isn't severe, but is still quite disabling during PEM). I may trial mestinon.
Neither beta blocker helped me much with the increase of HR when standing up. They might have lowered it from 140 to the 120s. They had more effect on my supine resting HR. Propranolol (10 mg TID Q6H) helped me with this tired but wired feeling but it had a negative impact on my lung function, so I stopped it. Nebivolol (2.5 mg qd) had no impact on the tired but wired feeling but improved lung function compared to my baseline.
I have a thread about my experiences here if you're curious! I actually first got an effect from the spice sumac, which is high in malic acid (but low in certain sugars, which is my guess for why other things high in malic acid such as apple juice don't affect me the same way). On the thread, others have mentioned that magnesium malate actually gave them a small boost as well. The only thing I'm not sure about off the top of my head is how much malate is actually in magnesium malate, and whether there's a risk of magnesium toxicity if you take enough to match the malic acid supplement. Either way, sumac is inexpensive and seems to not trigger any negative effects for those that tried it so far. I've been looking into the pharmacodynamics of pyridostigmine and don't see an immediate connection with how I think the malate works. So either it's two non-overlapping mechanisms that work for different people, or there's a connection that might just not be covered in the literature.
Have you been tested for antibodies against the acetylcholine receptor. If not it might be worth doing so.
Thanks for the tip, yes I've been tested and no autoantibodies against acetylcholine receptors found. Also no muscle weakness as it would present with MG.