I was diagnosed (through gene testing) to have paramyotonia congenita.
I am 60 years old, and am noticing it is getting worse as I age.
Honestly, I feel like I am trapped in a muscle suit that is trying to squeeze me to death some days, lol (no kidding)!
I have learned through an email from University of Michigan's Lori L. Isom, Ph.D., who is the Chair of Pharmacology, Professor of Molecular and Integrative Physiology, Professor of Neurology at University of Michigan Medical School and a Fellow - American Epilepsy Society Department of Pharmacology that, " my gene defect, specifically SCN4A, is also expressed in the heart and thus SCN4A variants have been associated with cardiac arrhythmia, which I have suffered from, but was chalked up as caused by "stress" until this diagnosis.
I was told that I likely need a detailed cardiac work-up, and to working closely with a cardiologist, and perhaps get a second opinion from the Michigan Medicine Cardiovascular Center.

I also was seen by a fine doctor at the Hauenstein Neuro-Science Center in Grand Rapids, MI, who indicated that when the sodium channel has a defect such as this, it leaves the "gate" open, which allows electroyltes to keep flowing into the muscle, making it fire /spasm. He indicated that sodium channel blockers are excellent at stopping this action. However, the drugs on the market currently come with their own risks.
That said, I opted for the natural sodium channel blocker route: CBD with some (Indica) THC to enable it to work synergistically (effectively) at reducing muscle spasms throughout the body, including cardiac muscle.
I also receive bi-weekly chiropractic massage paired with theraputic massage, and am sure to take at least two hot baths a week with epsom salt to help pull the lactic acid out of the muscles, which contributes to soreness.
I also get blood draws to check on electroyltes and a metabolic panel because I suffer from rolling deficiencies as a result of the muscles burning up the minerals and nutrients present.
I have learned (through experience) that when I start feeling Short of Breath (winded easily) my ferritin is low and I need to supplement with iron ( best is "Flora Iron + Herb liquid).
When I have muscles that just won't relax and start "roping" it's a potassium deficiency.
When I am weak and cannot even open a twist top, it's a magnesium deficiency, and Natural Calm (just mag) is the best for helping with that, and any tension headaches, heel spurs, high blood pressure, etc.

In the end, we have to become good stewards of these bodies we find our souls trapped in.
Tune in to what your body is telling you, and find doctors who listen just as intently, too!
Best wishes