Associations of serum and dialysate electrolytes with QT interval and prolongation in incident hemodialysis: the Predictors of Arrhythmic and Cardiovascular Risk in End-Stage Renal Disease (PACE) study

Table 4 Longitudinal associations of serum calcium and ionized calcium with QTc interval in 146 incident dialysis patients after simultaneously adjusting for serum potassium, and the interaction between each serum calcium measure and serum potassium

Variables	Multivariable*		Interaction
Variables	QTc difference (95% CI), ms	P	P**
Serum calcium and potassium in one model
Total calcium, per 1 SD decrease	+ 0.12 (−0.008, 0.25)	0.07	0.29
Potassium, per 1 SD decrease	+ 0.14 (0.04, 0.23)	0.004	0.29
Ionized calcium and potassium in one model
Ionized calcium, per 1 SD decrease	+ 0.21 (0.10, 0.32)	< 0.001	0.18
Potassium, per 1 SD decrease	+ 0.13 (0.04, 0.22)	0.003	0.18
Serum calcium and magnesium in one model
Serum calcium, per 1 SD decrease	+ 0.12 (−0.02, 0.25)	0.08	0.19
Magnesium, per 1 SD decrease	−0.02 (− 0.15, 0.12)	0.82	0.19
Ionized calcium and magnesium in one model
Ionized calcium, per 1 SD decrease	+ 0.21 (0.10, 0.31)	< 0.001	0.87
Magnesium, per 1 SD decrease	+ 0.01 (−0.13, 0.14)	0.91	0.87
Serum potassium and magnesium in one model
Serum potassium, per 1 SD decrease	+ 0.13 (0.04, 0.23)	0.006	0.84
Magnesium, per 1 SD decrease	−0.02 (−0.15, 0.12)	0.79	0.84

*Includes main exposures (calcium, potassium, or magnesium), age, sex, ethnicity, Charlson comorbidity index, non-dialysis systolic blood pressure, left ventricular mass index, and use of beta-blocker, renin-angiotensin-aldosterone system blockade, cinacalcet, and QT-prolonging medication. Model with ionized calcium also includes serum pH
**Interaction between calcium and potassium tested in a separate model

ISSN: 1471-2369