Hypokalaemia and atrial fibrillation detected by implanted loop recorders
August Krebs Hessellund, Emilie Katrine Kongebro, Ketil Haugan, Claus Graff, Daniel Camillo Spona, Jonas Alexander Baadsgaard, Lucas Yixi Xing, Søren Højberg, Derk Krieger, Axel Brandes, Lars Køber, Ruth Frikke‐Schmidt, Jesper Hastrup Svendsen, Søren Zöga Diederichsen
Abstract
BACKGROUND AND AIMS: Potassium levels influence cardiac electrophysiology, yet their day-to-day association with atrial fibrillation (AF) remains unclear. This study investigated the association between plasma potassium (p-potassium) and daily AF in at-risk individuals undergoing continuous electrocardiographic monitoring. METHODS: This is a post hoc analysis of the LOOP study randomizing participants with stroke risk factors to implantable loop recorder (ILR) screening for AF (n = 1501) or usual care. The ILR raw data were linked to p-potassium measurements collected in routine care allowing for 1-day time difference. Associations between p-potassium and daily AF > 60 min (main outcome) were analysed using generalized and linear mixed effect models. RESULTS: The ILR data and blood tests results were available for 1334 participants combining >1.6 million days of heart rhythm monitoring (including 50 746 days with AF) with 12 136 p-potassium measurements. P-potassium was lower on days with AF [mean difference -.21 mmol/L (-.25; -.18)]. Self-controlled case analyses comparing AF incidence during hypokalaemia (p-potassium <3.5 mmol/L) vs in normal range yielded an incidence rate ratio of 2.24 (1.29-3.88). Hypokalaemia was present in 5.1% of days with AF lasting <60 min and 19.1% with AF lasting >240 min. Each mmol/L decrease in p-potassium was associated with a five-fold increase in odds of AF [adjusted odds ratio (aOR) .20 (.15-.28)], more strongly when p-potassium deviated from the individual's usual value [aOR .15 (.10-.24); P-interaction = .001], and less in participants receiving diuretics [aOR .28 (.17-.47); P-interaction < .0001]. CONCLUSIONS: This exploratory study found that low p-potassium was associated with day-to-day AF occurrence, particularly for longer episodes and when deviating from the individual's usual level.