Table 1

Baseline characteristics of patients undergoing cardiac surgery

Variable	Atrial fibrillation		Overall	P value	Test
Variable	No	Yes
	% or mean
Cardiac surgery patients (N=1,269,414)	55.1	44.9
Mean age (years)	62	70	65.6	<0.001	t-test
Mean CCI	1.36	1.67	1.5	<0.001	t-test
Mean LOS (days)	11.1	12.2	11.6	<0.001	t-test
Mean cost (US$)	58,065	61,012	59,398	<0.001	t-test
Female	41.2	40.5	40.9	0.001	χ²
Primary payer
Medicare	49.5	68	57.8	<0.001	z-test
Medicaid	7.5	3.8	5.8	<0.001	z-test
Private	37.1	24.8	31.5	<0.001	z-test
Self-pay	2.9	1.6	2.3	<0.001	z-test
No charge	0.4	0.2	0.3	0.392	z-test
Other	2.7	1.7	2.3	<0.001	z-test
Race
White	77.7	84.1	80.6	<0.001	z-test
Black	8.6	4.9	6.9	<0.001	z-test
Hispanic	7.5	5.1	6.4	<0.001	z-test
Asian/Pacific Islander	2	2.2	2.1	0.275	z-test
Native American	0.7	0.5	0.6	0.297	z-test
Other	3.5	3.2	3.4	0.08	z-test
Income
0–25th percentile	23.4	21	22.3	<0.001 (increasing income in atrial fibrillation)	Cochran-Armitage
26th–50th percentile (median)	25.6	25.4	25.5
						51st–75th percentile	25.5	26.1	25.8
											76th–100th percentile	25.5	27.5	26.4
Moderate-to-severe disability on discharge	53.7	65.6	59		<0.001											χ²
In-hospital death	5	3.9	4.5		<0.001	χ²
No acute kidney injury	84.4	81.7	83.2		<0.001 (worsening renal function)	Cochran-Armitage
Acute kidney injury without dialysis	13.9	16.4	15
							Acute kidney injury with dialysis	1.8	1.9	1.8
												Stroke	2.1	1.8	2	<0.001	χ²
Congestive heart failure	2.3	2.2	2.3	0.612		χ²
Chronic lung disease	18.6	21.9	20.1	<0.001		χ²
Pulmonary hypertension	0.9	0.8	0.9	0.059		χ²
Hypertension	57.9	64.5	60.8	<0.001	χ²
Peripheral artery disease	14.4	14.1	14.3	0.106	χ²
Electrolyte disorder	27.4	32.1	29.5	<0.001	χ²
Metastatic cancer	0.5	0.4	0.5	0.229	χ²
Obesity	12.5	13.3	12.9	<0.001	χ²
Valve disease	2.1	1.9	2	0.012	χ²
Diabetes mellitus	23.6	25.3	24.4	<0.001	χ²
Weekend admission	7.3	7	7.2	0.022	χ²
Elective admission	63	64.8	63.8	<0.001	χ²
Hospital region
Northeast	22.3	22.1	22.2	0.205	z-test
Midwest	24.5	25.7	25	<0.001	z-test
South	33.6	32.4	33.1	<0.001	z-test
West	19.5	19.8	19.7	0.089	z-test
Teaching hospital	70.4	68.8	69.7	<0.001	χ²
Urban hospital	97	97	97	0.847	χ²
Hospital bed size
Small	6.1	6.4	6.2	<0.001 (increasing bed size in atrial fibrillation)	Cochran-Armitage
Medium	17.5	18	17.8
						Large	76.3	75.6	76
											Procedures (variables PR1–PR3)
CABG only	3.1	7.1	4.9		<0.001						z-test
Valve repair/replacement only	56.7	57.5	57		<0.001	z-test
CABG with valve repair/replacement	25.6	26.2	25.8		<0.001	z-test
Other procedures PR1–PR3	14.7	9.1	12.2	<0.001	z-test

CABG, coronary artery bypass graft; CCI, Charlson Comorbidity Index; LOS, length of stay.