exercise & atrial fibrillation

^[1]^[2]^[3]

Pathology

intense endurance training in animals produces atrial fibrosis & dilatation (left atrial enlargement) with autonomic changes including enhanced vagal tone
bradycardia of trained athletes promotes initiation of reentrant atrial fibrillation
stopping training allows for autonomic changes to reverse; however fibrosis & dilatation (left atrial enlargement) recover much more slowly, if at all

in women, exercise at levels up to 2500 MET-min/week reduces risk of atrial fibrillation
in men, increasing physical activity is only protective against atrial fibrillation to a level of 1500 MET-min/week
- beyond that, the protective effect is lost
- for men, there is a progressive increase in risk of atrial fibrillation with vigorous physical activity > 1500 MET-min/week, with s 12% risk increase at 5000 MET-min/week

strenous exercise is ~ 10 METS, thus
- 30 minutes 3 times/week ~ 900 METS/week
- 30 minutes 4 times/week ~ 1200 METS/week
- 40 minutes 3 times/week ~ 1200 METS/week
- 40 minutes 4 times/week ~ 1260 METS/week

↑ Elliott AD, Linz D, Mishima R Association between physical activity and risk of incident arrhythmias in 402,406 individuals: evidence from the UK Biobank cohort. Eur Heart J. 2020 Apr 14;41(15):1479-1486. PMID: https://www.ncbi.nlm.nih.gov/pubmed/31951255
↑ Nattel S Physical activity and atrial fibrillation risk: it's complicated; and sex is critical. Eur Heart J. 2020 Apr 14;41(15):1487-1489. PMID: https://www.ncbi.nlm.nih.gov/pubmed/31951253
↑ Elliott AD, Linz D, Verdicchio CV, Sanders P. Exercise and Atrial Fibrillation: Prevention or Causation? Heart Lung Circ. 2018 Sep;27(9):1078-1085. PMID: https://www.ncbi.nlm.nih.gov/pubmed/29891251