Table 3.

Longitudinal associations of serum and dialysate electrolytes with QTc interval in 146 incident dialysis patients

Variables	Model 1		Model 2		Model 3
	QTc difference (95% CI), ms	P	QTc difference (95% CI), ms	P	QTc difference (95% CI), ms	P
Serum measurements
Total calcium, per 1 mg/dl decrease	+ 9.13 (0.65, 17.61)	0.04	+ 8.89 (1.20, 16.58)	0.02	+ 7.06 (− 0.59, 14.72)	0.07
Corrected calcium, per 1 mg/dl decrease	+ 8.29 (−1.29, 17.88)	0.09	+ 7.71 (− 0.91, 16.34)	0.08	+ 5.74 (− 2.78, 14.26)	0.19
Ionized calciuma, per 0.1 mmol/l decrease	+ 9.79 (3.17, 16.41)	0.004	+ 10.18 (4.02, 16.33)	0.001	+ 9.05 (3.28, 14.83)	0.002
Potassium, per 1 mEq/l decrease	+ 9.08 (2.23, 15.94)	0.01	+ 9.87 (3.12, 16.62)	0.004	+ 9.43 (2.89, 15.98)	0.01
Magnesiuma, per 0.1 mEq/l decrease	+ 0.84 (− 1.05, 2.74)	0.38	+ 0.69 (− 1.26, 2.63)	0.49	+ 0.32 (−1.60, 2.24)	0.75
Dialysate measurements
Calcium
2.5 mEq/l	reference		reference		reference
< 2.5 mEq/l	+ 3.18 (− 6.56, 12.91)	0.52	+ 3.03 (− 6.07, 12.14)	0.51	+ 4.00 (− 4.60, 12.60)	0.36
Potassium
2 mEq/l	reference		reference		reference
> 2 mEq/l	− 5.44 (− 21.22, 10.35)	0.50	−6.36 (− 21.05, 8.32)	0.40	− 5.58 (− 19.98, 8.82)	0.45
Serum-to-dialysate gradients
Total calcium, per 1 mEq/l increase in difference	− 11.13 (− 23.59, 1.33)	0.08	−10.81 (− 22.38, 0.76)	0.07	−8.06 (− 18.88, 2.77)	0.15
Corrected calcium, per 1 mEq/l increase in difference	− 9.14 (− 22.83, 4.54)	0.19	− 8.48 (− 21.15, 4.19)	0.2	− 5.61 (− 17.34, 6.12)	0.35

Model 1 includes the main exposure (one of serum, dialysate, or gradient measurements)

Model 2 includes model 1, age, sex, and ethnicity

Model 3 includes model 2, Charlson comorbidity index, non-dialysis systolic blood pressure, left ventricular mass index, and use of antihypertensive medication, renin-angiotensin-aldosterone system blockade, cinacalcet, and QT-prolonging medication

^aModels with ionized calcium and magnesium also include serum pH