Predicting New-Onset Postoperative Atrial Fibrillation Following Isolated Coronary Artery Bypass Grafting: Development and Validation of a Novel Nomogram

Figures & data

Table 1 Characteristics of the Patients in the Derivation Cohort and Validation Cohort

Variable	Derivation Cohort (n=3641)	Validation Cohort (n=1213)	P value
Age, y	62.6±8.6	62.9±8.7	0.277
Sex, male, n(%)	2773(76.2)	895(73.8)	0.095
BMI, kg/m^2	25.9(23.8,27.9)	25.8(23.5,27.7)	0.191
BMI≥28 kg/m^2, n(%)	811(22.3)	269(22.2)	0.944
Heart rate, beats/min, n(%)	81.9±17.1	77.7±16.6	<0.001
≤60	318(8.7)	167(13.8)	<0.001
61–80	1559(42.8)	584(48.1)
81–100	1237(34.0)	348(28.7)
101–120	455(12.5)	99(8.2)
>120	72(2.0)	15(1.2)
Current smoking, n(%)	1082(29.7)	328(27.0)	0.075
Medical history, n(%)
Hypertension	2439(67.0)	825(68.0)	0.510
Diabetes	1446(39.7)	486(40.1)	0.828
COPD	61(1.7)	20(1.6)	0.950
PVD	1611(44.2)	572(47.2)	0.078
Previous CVA	417(11.5)	124(10.2)	0.238
Previous MI	404(11.1)	128(10.6)	0.600
Previous PCI	754(20.7)	318(26.2)	<0.001
Echocardiographic features
LVEF, %	59.9±8.2	58.5±8.7	<0.001
LVEF<50%, n(%)	372(10.2)	162(13.4)	0.002
LVEDD, mm	48.1±5.4	48.7±5.8	0.002
LAD, mm	36.3±4.3	36.5±4.4	0.086
LAD>40mm, n(%)	530(14.6)	193(15.9)	0.251
Preoperative medication, n(%)
β-Blockers	2734(75.1)	871(71.9)	0.024
Calcium channel blockers	262(7.2)	95(7.8)	0.461
Statins	3039(83.5)	973(80.5)	0.010
Baseline laboratory values
eGFR, mL/min/1.73 m^2	92.0±16.6	91.8±16.9	0.661
Hemoglobin, g/dL	13.5±1.4	13.3±1.7	<0.001
Platelet count, ×10^9/L	221.5±64.0	217.4±68.2	0.060
White blood cell count, ×10^9/L	7.3±2.5	7.9±3.1	<0.001
Procedural characteristics
Preoperative IABP, n(%)	112(3.1)	46(3.8)	0.223
Minimal access surgry, n(%)	290(8.0)	100(8.2)	0.757
Number of grafts per patient	2.6±0.9	2.6±0.9	0.222
LIMA graft + SVG, n(%)	2516(69.1)	835(68.8)	0.863
On-pump surgery, n(%)	837(23.0)	285(23.5)	0.717
POAF, n(%)	1025(28.2)	337(27.8)	0.804
CHA2DS2-VASc score	2(2,4)	3(2,4)	0.063
HATCH score	1(1,2)	1(1,2)	0.120
POAF score	1(0,2)	1(0,1)	0.100
Hospital stay, days	14.2±5.6	14.4±5.5	0.230

Note: Values are mean ± SD, n(%), or median (interquartile range).

Abbreviations: BMI, body mass index; COPD, chronic obstructive pulmonary disease; PVD, peripheral vascular disease; CVA, cerebral vascular accident; MI, myocardial infarction; PCI, percutaneous coronary intervention; LVEF, left ventricular ejection fraction; LVEDD, left ventricular end diastolic diameter; LAD, left atrial diameter; eGFR, estimated glomerular filtration rate; IABP, intra-aortic balloon pump; LIMA, left internal mammary artery; SVG, saphenous vein graft; POAF, postoperative atrial fibrillation.

Figure 1 The consort diagram showing the inclusion and exclusion of patients.

Abbreviations: CAD, coronary artery disease; CABG, coronary artery bypass grafting; AF, atrial fibrillation.

Table 2 Characteristics of the Patients with and without Postoperative Atrial Fibrillation in the Derivation Cohort

Variable	With POAF (n=1025)	Without POAF (n=2616)	P value
Age, y	65.0±8.2	61.7±8.6	<0.001
Sex, male, n(%)	814(79.4)	1959(74.9)	0.004
BMI, kg/m^2	26.1(24.0,27.8)	25.8(23.7,27.7)	0.011
BMI≥28 kg/m^2, n(%)	242(23.6)	569(21.8)	0.225
Heart rate, beats/min, n(%)	83.7±18.1	81.2±16.7	<0.001
≤60	84(8.2)	234(8.9)	0.011
61–80	415(40.5)	1144(43.7)
81–100	356(34.7)	881(33.7)
101–120	138(13.5)	317(12.1)
>120	32(3.1)	40(1.5)
Current smoking, n(%)	290(28.3)	792(30.3)	0.239
Medical history, n(%)
Hypertension	740(72.2)	1699(64.9)	<0.001
Diabetes	410(40.0)	1036(39.6)	0.825
COPD	21(2.0)	40(1.5)	0.272
PVD	503(49.1)	1108(42.4)	<0.001
Previous CVA	128(12.1)	300(11.1)	0.372
Previous MI	123(12.0)	281(10.7)	0.277
Previous PCI	208(20.3)	546(20.9)	0.698
Echocardiographic features
LVEF, %	58.5±8.9	60.4±7.8	<0.001
LVEF<50%, n(%)	154(15.0)	218(8.3)	<0.001
LVEDD, mm	48.7±5.8	47.9±5.2	<0.001
LAD, mm	37.1±4.6	35.9±4.2	<0.001
LAD>40mm, n(%)	217(21.2)	313(12.0)	<0.001
Preoperative medication, n(%)
β-Blockers	757(73.9)	1977(75.6)	0.293
Calcium channel blockers	79(7.7)	183(7.0)	0.452
Statins	843(82.3)	2196(84.0)	0.227
Baseline laboratory values
eGFR, mL/min/1.73 m^2	88.2±17.5	93.5±16.0	<0.001
Hemoglobin, g/dL	13.5±1.5	13.4±1.4	0.504
Platelet count, ×10^9/L	218.1±64.7	222.8±63.7	0.044
White blood cell count, ×10^9/L	7.3±2.4	7.3±2.5	0.529
Procedural characteristics
Preoperative IABP, n(%)	35(3.4)	77(2.9)	0.459
Minimal access surgery, n(%)	82(8.0)	208(8.0)	0.961
Number of grafts per patient	2.6±0.9	2.6±0.9	0.334
LIMA graft + SVG, n(%)	671(65.5)	1845(70.5)	0.003
On-pump surgery, n(%)	287(28.0)	550(21.0)	<0.001
CHA2DS2-VASc score	3(2,4)	2(1,3)	<0.001
HATCH score	1(1,2)	1(0,1)	<0.001
POAF score	1(1,2)	1(0,1)	<0.001
Hospital stay, days	15.6±6.9	13.6±4.8	<0.001

Note: Values are mean ± SD, n(%), or median (interquartile range).

Abbreviations: POAF, postoperative atrial fibrillation; BMI, body mass index; COPD, chronic obstructive pulmonary disease; PVD, peripheral vascular disease; CVA, cerebral vascular accident; MI, myocardial infarction; PCI, percutaneous coronary intervention; LVEF, left ventricular ejection fraction; LVEDD, left ventricular end diastolic diameter; LAD, left atrial diameter; eGFR, estimated glomerular filtration rate; IABP, intra-aortic balloon pump; LIMA, left internal mammary artery; SVG, saphenous vein graft.

Table 3 Multivariate Logistic Regression Analysis for Predicting Postoperative Atrial Fibrillation in the Derivation Cohort

Covariate	β Coefficient	OR (95% CI)	P value
Age, y	0.048	1.049(1.038 to 1.060)	<0.001
Sex, male	0.397	1.488(1.236 to 1.790)	<0.001
Heart rate, beats/min			0.005
≤60	Ref.
61–80	0.161	1.175(0.884 to 1.561)	0.267
81–100	0.332	1.394(1.042 to 1.865)	0.025
101–120	0.312	1.366(0.976 to 1.912)	0.069
>120	0.942	2.565(1.465 to 4.492)	0.001
Hypertension	0.292	1.339(1.134 to 1.582)	0.001
LVEF<50%	0.546	1.726(1.358 to 2.194)	<0.001
LAD>40mm	0.480	1.616(1.318 to 1.982)	<0.001
eGFR, mL/min/1.73 m^2	−0.007	0.993(0.988 to 0.997)	0.003
On-pump surgery	0.261	1.298(1.090 to 1.546)	0.003

Abbreviations: OR, odds ratio; CI, confidence interval; LVEF, left ventricular ejection fraction; LAD, left atrial diameter; eGFR, estimated glomerular filtration rate.

Figure 2 The nomogram derived from derivation cohort for predicting new-onset postoperative atrial fibrillation following isolated coronary artery bypass grafting.

Abbreviations: eGFR, estimated glomerular filtration rate; LVEF, left ventricular ejection fraction; LAD, left atrial diameter; POAF, postoperative atrial fibrillation.

Figure 3 Calibration curves of the nomogram for predicting postoperative atrial fibrillation in derivation (A) and validation (B) cohorts. Diagonal line indicates perfect calibration. The triangles indicate the observed frequencies of postoperative atrial fibrillation by the deciles of the predicted probability.

Figure 4 Predicted and observed risks of postoperative atrial fibrillation based on decile grouping of predicted risk in derivation (A) and validation (B) cohorts.

Figure 5 Discriminative ability of the nomogram to postoperative atrial fibrillation as compared to the CHA2DS2-VASc, HATCH and POAF scores shown by area under the receiver operating characteristic (ROC) curves (AUCs) in derivation (A) and validation (B) cohorts.

Abbreviations: CI, confidence interval; POAF, postoperative atrial fibrillation.