Table 3.

Univariate and backward linear multivariate regression model analysis

	Univariate analysis			Multivariate analysis
Variable	USC	SC	R square	P value	USC	SC	P value
Age (per year)	0.079	0.139	0.019	<0.001	0.061	0.108	<0.001
Female gender	−0.211	−0.054	0.003	0.056	Excluded
Temperature (°C)	0.038	0.009	0.000	0.764
Systolic blood pressure (mm Hg)	0.024	0.146	0.021	<0.001	0.029	0.173	<0.001
Diastolic blood pressure (mm Hg)	0.005	0.022	0.000	0.479
Ventricular rate (beats/min)	−0.013	−0.076	0.006	0.006	−0.014	−0.081	0.005
Serum Sodium (mmol/l)	−0.022	−0.024	0.001	0.399
Serum Potassium (mmol/l)	0.299	0.054	0.003	0.054	0.253	0.046	0.098
Serum Calcium (mmol/l)	−0.735	−0.038	0.001	0.178
Maximum P-wave duration (ms)	0.020	0.130	0.017	<0.001	0.018	0.112	<0.001
P-wave balance in lead V1 (µV)	0.003	0.077	0.006	0.006	0.003	0.072	0.010
P-wave dispersion (ms)	0.001	0.009	0.000	0.740
Total P-wave area in lead V1 (mm*ms)	0.002	0.084	0.007	0.003	Excluded
PR interval (ms)	0.007	0.090	0.008	0.001	Excluded
QRS duration (ms)	0.009	0.053	0.003	0.059	Excluded
Heart axis (degrees)	−0.012	−0.191	0.036	<0.001	−0.010	−0.164	<0.001
Sokolow-Lyon voltage (mm)	0.000	−0.048	0.002	0.084	0.000	−0.097	<0.001
Cornell product (mm)	5.67 *10−7	0.021	0.000	0.458
Maximum T‑wave duration (ms)	−0.002	−0.019	0.000	0.503
Minimum T‑wave duration (ms)	0.001	0.038	0.001	0.171
T-wave dispersion (ms)	−0.001	−0.045	0.002	0.107
QTcF (ms)	5.38 *10−5	0.001	0.000	0.982

Probabilities of less than 0.10 in the linear univariate regression model were added to the backward linear multivariate regression model. Results are reported as unstandardised coefficient (USC) and standardised coefficient (SC) with the corresponding P value and the R‑square value in the linear univariate regression model. The R square of the backward linear multivariate regression model was 0.100

mV millivolt, µV microvolt, ms milliseconds, mm millimetres, QTcF corrected QT interval with the Fridericia formula