Just one thing that crosses my mind. Anxiety depletes magnesium, and low magnesium will make you feel anxious. Low magnesium levels and SVT can be connected. Tremors can by brought on by magnesium deficiency. And most of the population are magnesium deficient! Magnesium and vitamin D are essential to balance out calcium and get calcium properly stored in your body. Calcium causes your muscles to contract, magnesium is needed to relax them.
May be worth having a chat with your GP about that, (although many GPs are still pretty ignorant about magnesium, and they also are extremely unlikely to test for mag deficiency).
Worth watching this following video made by a York based cardiologists about magnesium.
He’s actually done a few videos on magnesium. The one I’ve linked to is probably the most general. Obviously because he’s a cardiologist he has a particular focus on the heart.
From wikipedia it is clear that magnesium deficiency can cause a raft of neurological symptoms:
Deficiency of magnesium can cause tiredness, generalized weakness, muscle cramps, abnormal heart rhythms, increased irritability of the nervous system with tremors, paresthesias, palpitations, low potassium levels in the blood, hypoparathyroidism which might result in low calcium levels in the blood, chondrocalcinosis, spasticity and tetany, migraines, epileptic seizures, basal ganglia calcifications and in extreme and prolonged cases coma, intellectual disability or death.[7]