Table 2. Number of Patients With Electrolyte Concentrations Above the Thresholds Among Those Who Did and Did Not Develop AF.

Electrolyte Group	AF, n (%)	No AF, n (%)	p value
Mean [K+] <4.5 mmol/L, n (%)	274 (51.6)	1057 (42.0)	<0.001
Mean [K+] ≥4.5 mmol/L, n (%)	257 (48.4)	1461 (58.0)	<0.001
Mean [Mg2+] <1.0 mmol/L, n (%)	145 (30.3)	973 (39.3)	<0.001
Mean [Mg2+]≥1.0 mmol/L, n (%)	333 (69.7)	1505 (60.7)	<0.001

Due to missing [K⁺] and [Mg²⁺] data, 3,049 patients were included in potassium analyses and 2,956 were included in magnesium analyses as described in Fig 1. For those who developed AF the mean [K⁺] was calculated over the 12 hours before onset of AF and the mean [Mg²⁺] was calculated over the 24 hours before onset of AF. For those who didn’t suffer AF the mean values were calculated over the first 72 hours of the CICU stay. Abbreviation: AF, atrial fibrillation; CICU, Cardiac Intensive Care Unit