(I am no expert, the following is only from my own experience after serious burnout years ago and a lot of research for my family and me. But it is perhaps helpful as start for you!)

If it is not due to any medical drugs (e.g. dopamin - parkinson drugs?), please consider the adrenal glands and possible exhaution.

Perhaps this is helpful: Tachycardia-symptoms - POTS

Mitral valve prolapse syndrome, chronic orthostatic intolerance, and orthostatic tachycardia symptoms are each names that reference postural tachycardia syndrome (POTS). POTS is not a new illness. It is caused by a malfunction of the patient's autonomic nervous system (ANS).

ADRENAL FATIGUE

VAGUS NERVE RESET (your wife should watch, as soon she is home/better)

HERBAL SOLUTIONS:

American ginseng is, it’s going to be just as effective as Chinese ginseng, Panax, Red, Korean ginseng, but it’s not going to be as stimulating. You can take a lot more of it and not cause insomnia or have too much stimulation or agitation.

I’ll combine American ginseng with Reishi mushroom, astragalus and ginger in a tincture and that particular formula is designed for chronic infections. Again, that’s American ginseng, Reishi mushroom, astragalus and ginger root. That really helps with chronic infections. A lot of people with fatigue, they have a chronic infection that’s just wearing them down. It’s wearing down the adrenals. That’s how we’ll use that combination.

... and as an idea to research further

The adrenal glands have a major impact on the body system! When exausted Vitamin D, Magnesium/Calcium, Zinc would/could help, but more importantly reducing of stress, NO COFFEE AND STIUMLANTS, NO JOGGING!, slow nice walks, BEING in nature, fresh air and the sun, cold showers and later cold swims (think learning Wim Hof), avoid mind work, thinking, internet, problems.

Feelings of love, laughter and liberty are very much helful.

God bless you and your little family, praying that your wife will recover soon and completely.