My partner (47 year old woman in very good health, fit, slim) was in hospital for 2 nights with racing and irregular heart and was diagnosed with atrial fibrillation. A cardio electro-physiologist follow-up appointment diagnosed her by her hospital traces as having atrial tachycardia NOT atrial fibrillation and said she is fine, and to go back in 6 months for a check. He said if she gets AT for more than 3 hours to go to hospital if it s uncomfortable. She is getting it a lot tonight for runs of about 2-3 mins at a time of very fat rate (150bpms) it comes on when she lies on her left hand side. Is there a common reason for it to come on with positional movement? Thanks in advance.