Association Between Body Mass Index, Obesity, and Clinical Outcomes Following Coronary Artery Bypass Grafting in Brazil: An Analysis of One Year of Follow-up of BYPASS Registry Patients

Ramos, Rodrigo Santin; Rocco, Isadora Salvador; Viceconte, Marcela; Santo, José Amalth do Espírito; Berwanger, Otavio; Santos, Renato Hideo Nakagawa; Kalil, Renato Abdala Karam; Jatene, Fabio B.; Cavalcanti, Alexandre Biasi; Zilli, Alexandre Cabral; Pimentel, Walace de Souza; Hossne Junior, Nelson Américo; Branco, João Nelson Rodrigues; Trimer, Renata; Evora, Paulo Roberto Barbora; Gomes, Walter J.; Guizilin, Solange; ,

doi:10.21470/1678-9741-2023-0133

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Brasil

Brazilian Journal of Cardiovascular Surgery

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Sumário

ORIGINAL ARTICLE • Braz. J. Cardiovasc. Surg. 39 (2) • 2024 • https://doi.org/10.21470/1678-9741-2023-0133 copy

Association Between Body Mass Index, Obesity, and Clinical Outcomes Following Coronary Artery Bypass Grafting in Brazil: An Analysis of One Year of Follow-up of BYPASS Registry Patients

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

Objective:

To investigate the association between body mass index (BMI), obesity, clinical outcomes, and mortality following coronary artery bypass grafting (CABG) in Brazil using a large sample with one year of follow-up from the Brazilian Registry of Cardiovascular Surgeries in Adults (or BYPASS) Registry database.

Methods:

A multicenter cohort-study enrolled 2,589 patients submitted to isolated CABG and divided them into normal weight (BMI 20.0-24.9 kg/m²), overweight (BMI 25.0-29.9 kg/m²), and obesity (BMI > 30.0 kg/m²) groups. Inpatient postoperative outcomes included the most frequently described complications and events. Collected post-discharge outcomes included rehospitalization and mortality rates within 30 days, six months, and one year of follow-up.

Results:

Sternal wound infections (SWI) rate was higher in obese compared to normal-weight patients (relative risk [RR]=5.89, 95% confidence interval [CI]=2.37-17.82; P=0.001). Rehospitalization rates in six months after discharge were higher in obesity and overweight groups than in normal weight group (χ²2 D'Agostino RS, Jacobs JP, Badhwar V, Fernandez FG, Paone G, Wormuth DW, et al. The society of thoracic surgeons adult cardiac surgery database: 2019 update on outcomes and quality. Ann Thorac Surg. 2019;107(1):24-32. doi:10.1016/j.athoracsur.2018.10.004.
https://doi.org/10.1016/j.athoracsur.201... =6.03, P=0.049); obese patients presented a 2.2-fold increase in the risk for rehospitalization within six months compared to normal-weight patients (RR=2.16, 95% CI=1.17-4.09; P=0.045). Postoperative complications and mortality rates did not differ among groups during time periods.

Conclusion:

Obesity increased the risk for SWI, leading to higher rehospitalization rates and need for surgical interventions within six months following CABG. Age, female sex, and diabetes were associated with a higher risk of mortality. The obesity paradox remains controversial since BMI may not be sufficient to assess postoperative risk in light of more complex and dynamic evaluations of body composition and physical fitness.

Keywords:
Body Mass Index; Obesity Paradox; Mortality; Coronary Artery Bypass; Postoperative Complications; Registries

Abbreviations, Acronyms & Symbols
ARDS	= Acute respiratory distress syndrome	ICU	= Intensive care unit
BMI	= Body mass index	LCOS	= Low cardiac output syndrome
BYPASS	= Brazilian Registry of Cardiovascular Surgeries in Adults	LVEF	= Left ventricular ejection fraction
CABG	= Coronary artery bypass grafting	MI	= Myocardial infarction
CAD	= Coronary artery disease	MV	= Mechanical ventilation
CI	= Confidence interval	PCI	= Percutaneous coronary intervention
COPD	= Chronic obstructive pulmonary disease	RBC	= Red blood cells
CPB	= Cardiopulmonary bypass	RR	= Relative risk
CVD	= Cardiovascular disease	STS	= Society of Thoracic Surgeons
EuroSCORE	= European System for Cardiac Operative Risk Evaluation	SWI	= Sternal wound infections
GzLM	= Generalized linear model

Variables	Total (n=2589)	Normal weight (n=767)	Overweight (n=1146)	Obesity (n=676)	P-value
Age (years)^a	63.5±9.5	64.5±9.9	63.7±9.2	61.9±9.5^{^*$}	< 0.001
BMI (kg/m²)^a	27.5±4.3	22.9±1.5	27.3±1.4	32.1±3.0^{^*$}	< 0.001
Female sex, n (%)^b	743 (28.7)	208 (27.1)	308 (26.9)	227 (33.6)^{^*$}	0.005
Hypertension, n (%)^b b χ2 test, respectively	2194 (84.7)	599 (78.1)	990 (86.4)	605 (89.5)^{^*$}	< 0.001
Dyslipidemia, n (%)^b b χ2 test, respectively	1357 (52.4)	349 (45.5)	615 (53.7)	393 (58.1)^{^*}	< 0.001
Diabetes, n (%)^b b χ2 test, respectively	1108 (42.8)	277 (36.1)	483 (42.1)	348 (51.5)^{^*$}	< 0.001
Active smoker, n (%)^b b χ2 test, respectively	313 (12.1)	132 (17.2)	110 (9.6)	71 (10.5)^*$	< 0.001
Ex-smoker, n (%)^b b χ2 test, respectively	649 (28.7)	177 (28.1)	289 (28.1)	183 (30.4)	0.557
History of CVD, n (%)^b b χ2 test, respectively	926 (35.8)	258 (33.6)	411 (35.9)	257 (38.0)	0.222
Heart failure, n (%)^b b χ2 test, respectively	338 (13.1)	110 (14.3)	143 (12.5)	85 (12.6)	0.451
Previous MI, n (%)^b b χ2 test, respectively	1036 (40.0)	323 (42.1)	445 (38.8)	268 (39.6)	0.348
Previous PCI, n (%)^b b χ2 test, respectively	339 (13.1)	89 (11.6)	159 (13.9)	91 (13.5)	0.334
LVEF (%)^a	58.2±12.8	56.0±13.6	58.8±12.6	59.8±11.8	< 0.001
Peripheral arterial disease, n (%)^b b χ2 test, respectively	174 (6.7)	59 (7.7)	78 (6.8)	37 (5.5)	0.241
Previous stroke, n (%)^b b χ2 test, respectively	112 (4.3)	32 (4.2)	52 (4.5)	28 (4.1)	0.894
Chronic kidney disease, n (%)^b b χ2 test, respectively	117 (4.5)	39 (5.1)	49 (4.3)	29 (4.3)	0.668
Preoperative arrhythmias, n (%)^b b χ2 test, respectively	153 (5.9)	49 (6.4)	64 (5.6)	40 (5.9)	0.766
Baseline clinics
Serum creatinine (mg/dL)^a	1.05±0.77	1.05±0.82	1.07±0.79	1.04±0.66	0.441
RBC (g/dL)^a	12.3±5.34	12.0±3.3	12.4±5.5	12.5±6.8	0.096
Blood glucose level (mmol/L)^a	102±77	94±74.2	104±77.5	109±80.9	0.001
Operative characteristics
Number of grafts, n^c c Kruskal-Wallis test *P<0.03 for pairwise comparison with normal weight	3 (2 - 4)	3 (2 - 4)	3 (2 - 4)	3 (2 - 4)	0.943
CPB use^a	2261 (87.4)	665 (86.7)	999 (87.2)	597 (88.4)	0.597
CPB time (min)^a	69 (52 - 90)	68 (51 - 89)	70 (55 - 91)	65 (50 - 88)	0.721
Occluding clamp^a	206 (9.1)	54 (8.1)	96 (9.6)	56 (9.4)	0.565
Total	57 (27.7)	13 (24.1)	31 (32.3)	13 (23.2)	0.381
Partial	149 (72.3)	41 (75.9)	65 (67.7)	43 (76.8)	-
Cardioplegia use, n (%)^a	2156 (95.4)	625 (94.0)	950 (95.1)	625 (94.0)^{^*}	0.017
Vasoactive drug during operation, n (%)^a	1271 (49.1)	398 (51.9)	558 (48.7)	315 (46.7)	0.132
Intraoperative mortality, n (%)^a	7 (0.3)	1 (0.1)	4 (0.3)	2 (0.3)	0.658

Inpatient outcomes	Total (n=2589)	Normal weight (n=767)	Overweight (n=1146)	Obesity (n=676)	P-value
Prolonged MV, n (%)	580 (22.4)	170 (22.2)	253 (22.1)	157 (23.2)	0.836
ARDS, n (%)	34 (1.3)	9 (1.2)	18 (1.6)	7 (1.0)	0.576
LCOS, n (%)	78 (3.0)	24 (3.1)	38 (3.3)	16 (2.4)	0.506
Renal failure, n (%)	88 (3.4)	24 (3.1)	40 (3.5)	24 (3.6)	0.884
Stroke, n (%)	31 (1.2)	10 (1.3)	12 (1.0)	9 (1.3)	0.821
Need for insulin, n (%)	513 (19.8)	134 (17.5)	222 (19.4)	157 (23.2)	0.021
New arrhythmias, n (%)	431 (16.6)	121 (15.8)	196 (17.1)	114 (16.9)	0.736
Bleeding, n (%)	76 (2.9)	32 (4.2)	32 (2.8)	12 (1.8)^* * P<0.05 for pairwise comparison of obesity vs. normal weight	0.025
Early reoperation, n (%)	60 (2.3)	18 (2.3)	29 (2.5)	13 (1.9)	0.706
SWI, n (%)	119 (4.6)	11 (1.4)	49 (4.3)	59 (8.8)^* * P<0.05 for pairwise comparison of obesity vs. normal weight	< 0.001
Prolonged ICU stay, n (%)	580 (22.4)	170 (22.2)	253 (22.1)	157 (23.2)	0.836
Prolonged hospitalization, n (%)	128 (4.9)	36 (4.7)	51 (4.5)	41 (6.0)	0.294
Hospital mortality, n (%)	58 (2.2)	20 (2.6)	24 (2.1)	14 (2.1)	0.714
30-day outcomes	Total	Normal weight	Overweight	Obesity	P-value
	(n=2142)	(n=641)	(n=931)	(n=570)
Renal failure, n (%)	26 (1.2)	5 (0.8)	10 (1.1)	11 (1.9)	0.166
Stroke, n (%)	13 (0.6)	4 (0.6)	3 (0.3)	6 (1.1)	0.209
Heart Failure, n (%)	16 (0.7)	4 (0.6)	5 (0.5)	7 (1.2)	0.288
30-day rehospitalization, n (%)	113 (5.3)	35 (5.5)	42 (4.5)	36 (6.3)	0.302
30-day mortality, n (%)	26 (1.1)	6 (0.9)	12 (1.3)	8 (1.4)	0.745
6-month outcomes	Total	Normal weight	Overweight	Obesity	P-value
	(n=1635)	(n=499)	(n=716)	(n=420)
Renal failure, n (%)	15 (0.9)	2 (0.4)	6 (0.8)	7 (1.7)	0.126
Stroke, n (%)	6 (0.4)	1 (0.2)	3 (0.4)	2 (0.5)	0.752
Heart failure, n (%)	10 (0.6)	2 (0.4)	6 (0.8)	2 (0.5)	0.578
6-month rehospitalization, n (%)	92 (5.6)	18 (3.6)	44 (6.2)	30 (7.1)^* * P<0.05 for pairwise comparison of obesity vs. normal weight	0.040
Surgical intervention at 6-month, n (%)	30 (1.8)	4 (0.8)	12 (1.7)	14 (3.3)^* * P<0.05 for pairwise comparison of obesity vs. normal weight	0.016
6-month mortality, n (%)	20 (1.2)	7 (1.4)	9 (1.3)	4 (0.9)	0.811
1-year outcomes	Total	Normal weight	Overweight	Obesity	P-value
	(n=1049)	(n=318)	(n=462)	(n=269)
Renal failure, n (%)	2 (0.2)	0 (0.0)	2 (0.4)	0 (0.0)	0.280
Stroke, n (%)	2 (0.2)	0 (0.0)	2 (0.4)	0 (0.0)	0.278
Heart failure, n (%)	10 (1.0)	2 (0.6)	4 (0.9)	4 (1.5)	0.555
1-year rehospitalization, n (%)	29 (2.8)	8 (2.5)	16 (3.5)	5 (1.9)	0.420
1-year mortality, n (%)	7 (0.7)	0 (0.0)	5 (1.1)	2 (0.7)	0.188

Variables	RR	95% CI	z	P-value
Prolonged MV	1.05	0.65 - 1.68	0.208	0.835
ARDS	1.05	0.37 - 2.91	0.104	0.917
LCOS	0.78	0.40 - 1.48	-0.760	0.447
Renal failure	1.13	0.63 - 2.04	0.418	0.676
Stroke	1.06	0.41 - 2.71	0.132	0.895
Need for insulin	1.08	0.81 - 1.43	0.537	0.932
New arrhythmias	1.26	0.94 - 1.69	1.579	0.114
Bleeding	0.44	0.21 - 0.85	-2.320	0.061
Early reoperation	0.89	0.42 - 1.87	-0.290	0.772
SWI	5.89	2.37 - 17.82	3.51	0.001
Prolonged ICU stay	0.88	0.68 - 1.14	-0.971	0.332
Prolonged hospitalization	1.25	0.74 - 2.10	0.822	0.411
Inpatient mortality	0.72	0.35 - 1.46	-0.892	0.372
30-day rehospitalization	1.21	0.72 - 2.03	0.725	0.469
30-day mortality	2.19	0.73 - 6.97	1.394	0.163
6-month rehospitalization	2.16	1.17 - 4.09	2.433	0.045
Need for surgical intervention	4.38	1.53 - 15.77	2.546	0.033
6-month mortality	0.62	0.16 - 2.13	-0.739	0.460
1-year rehospitalization	0.69	0.21 - 2.16	-0.614	0.539

Variables	RR	95% CI	z	P-value
Prolonged MV
Obesity - normal weight	1.05	0.65 - 1.68	0.208	0.835
Overweight - normal weight	0.93	0.61 - 1.40	-0.367	0.713
Age	1.04	1.02 - 1.07	4.440	< 0.0001
Sex (female - male)	1.32	0.91 - 1.91	1.482	0.138
Diabetes	0.93	0.64 - 1.32	-0.410	0.681
Hypertension	0.89	0.56 - 1.50	-0.434	0.664
ARDS
Obesity - normal weight	1.05	0.37 - 2.91	0.104	0.917
Overweight - normal weight	1.47	0.66 - 3.48	0.923	0.356
Age	1.09	1.05 - 1.14	4.374	< 0.001
Sex (female - male)	1.92	0.95 - 3.84	1.845	0.065
Diabetes	0.75	0.36 - 1.50	-0.810	0.418
Hypertension	1.58	0.55 - 6.71	0.744	0.457
LCOS
Obesity - normal weight	0.78	0.40 - 1.48	-0.760	0.447
Overweight - normal weight	1.05	0.63 - 1.81	0.206	0.837
Age	1.02	0.99 - 1.05	1.830	0.067
Sex (female - male)	1.38	0.84 - 2.22	1.314	0.189
Diabetes	0.99	0.61 - 1.57	-0.053	0.958
Hypertension	0.93	0.50 - 1.84	-0.242	0.808
Renal failure
Obesity - normal weight	1.13	0.63 - 2.04	0.418	0.676
Overweight - normal weight	1.06	0.64 - 1.82	0.249	0.803
Age	1.03	1.01 - 1.06	2.541	0.011
Sex (female - male)	0.94	0.57 - 1.49	-0.270	0.787
Diabetes	1.25	0.81 - 1.93	0.997	0.319
Hypertension	1.63	0.82 - 3.72	1.281	0.200
Stroke
Obesity - normal weight	1.06	0.41 - 2.71	0.132	0.895
Overweight - normal weight	0.82	0.35 - 1.95	-0.468	0.639
Age	1.06	1.02 - 1.11	2.996	0.003
Sex (female - male)	1.65	0.78 - 3.39	1.343	0.179
Diabetes	1.31	0.63 - 2.72	0.726	0.468
Hypertension	1.38	0.47 - 5.88	0.524	0.600
Need for insulin
Obesity - normal weight	1.08	0.81 - 1.43	0.537	0.932
Overweight - normal weight	1.01	0.78 - 1.31	0.085	0.591
Age	1.00	0.99 - 1.02	0.738	0.461
Sex (female - male)	1.17	0.93 - 1.46	1.355	0.175
Diabetes	7.49	5.93 - 9.54	16.603	< 0.001
Hypertension	0.89	0.65 - 1.24	-0.667	0.505
New arrhythmias
Obesity - normal weight	1.26	0.94 - 1.69	1.579	0.114
Overweight - normal weight	1.15	0.89 - 1.49	1.074	0.283
Age	1.06	1.04 - 1.07	8.914	< 0.001
Sex (female - male)	0.92	0.72 - 1.17	-0.680	0.497
Diabetes	0.88	0.71 - 1.09	-1.127	0.260
Hypertension	1.28	0.93 - 1.78	1.466	0.143
Bleeding
Obesity - normal weight	0.44	0.21 - 0.85	-2.320	0.061
Overweight - normal weight	0.66	0.39 - 1.09	-1.604	0.109
Age	1.01	0.99 - 1.05	1.176	0.239
Sex (female - male)	0.69	0.38 - 1.19	-1.258	0.208
Diabetes	0.98	0.60 - 1.58	-0.066	0.947
Hypertension	1.15	0.62 - 2.36	0.428	0.668
Reoperation
Obesity - normal weight	0.89	0.42 - 1.87	-0.290	0.772
Overweight - normal weight	1.15	0.63 - 2.16	0.450	0.653
Age	1.02	0.99 - 1.05	1.524	0.127
Sex (female - male)	0.68	0.35 - 1.24	-1.187	0.235
Diabetes	1.26	0.74 - 2.14	0.868	0.385
Hypertension	0.95	0.48 - 2.12	-0.119	0.906
SWI
Obesity - normal weight	5.89	2.37 - 17.82	3.51	0.001
Overweight - normal weight	2.96	1.19 - 8.98	2.153	0.094
Age	0.97	0.96 - 1.03	-1.425	0.887
Sex (female - male)	1.08	0.56 - 1.98	0.240	0.810
Diabetes	1.85	1.03 - 3.39	2.02	0.043
Hypertension	0.99	0.44 - 2.69	-0.003	0.997
Prolonged ICU stay
Obesity - normal weight	0.88	0.68 - 1.14	-0.971	0.332
Overweight - normal weight	0.98	0.78 - 1.22	-0.199	0.842
Age	0.99	0.97 - 1.00	-2.490	0.013
Sex (female - male)	1.07	0.87 - 1.33	0.700	0.484
Diabetes	1.06	0.88 - 1.29	0.647	0.518
Hypertension	1.32	1.03 - 1.69	2.176	0.030
Prolonged hospitalization
Obesity - normal weight	1.25	0.74 - 2.10	0.822	0.411
Overweight - normal weight	0.95	0.58 - 1.55	-0.218	0.827
Age	1.05	1.02 - 1.07	3.941	< 0.001
Sex (female - male)	2.06	1.37 - 3.07	3.531	< 0.001
Diabetes	1.79	1.19 - 2.72	2.809	0.005
Hypertension	1.09	0.61 - 2.16	0.291	0.771
Hospital mortality
Obesity - normal weight	0.72	0.35 - 1.46	-0.892	0.372
Overweight - normal weight	0.75	0.41 - 1.39	-0.913	0.361
Age	1.02	0.99 - 1.05	1.249	0.212
Sex (female - male)	2.79	1.64 - 4.79	3.771	< 0.001
Diabetes	1.06	0.61 - 1.81	0.210	0.834
Hypertension	1.37	0.62 - 3.65	0.716	0.474

Variables	RR	95% CI	z	P-value
30-day follow-up
Rehospitalization
Obesity - normal weight	1.21	0.72 - 2.03	0.725	0.469
Overweight - normal weight	0.84	0.52 - 1.37	-0.698	0.485
Age	1.03	1.01 - 1.05	2.673	0.008
Sex (female - male)	1.53	1.00 - 2.31	2.008	0.045
Diabetes	1.73	1.15 - 2.62	2.633	0.008
Hypertension	0.68	0.40 - 1.17	-1.457	0.145
30-day mortality
Obesity - normal weight	2.19	0.73 - 6.97	1.394	0.163
Overweight - normal weight	1.64	0.61 - 4.83	0.963	0.336
Age	1.16	1.10 - 1.22	5.404	< 0.001
Sex (female - male)	0.79	0.30 - 1.87	-0.495	0.620
Diabetes	1.06	0.47 - 2.39	0.154	0.877
Hypertension	1.22	0.40 - 5.28	0.312	0.755
6-month follow-up
Rehospitalization
Obesity - normal weight	2.16	1.17 - 4.09	2.433	0.045
Overweight - normal weight	1.87	1.07 - 3.41	2.126	0.100
Age	1.01	0.98 - 1.03	0.660	0.509
Sex (female - male)	1.19	0.75 - 1.89	0.771	0.441
Diabetes	1.08	0.69 - 1.67	0.340	0.733
Hypertension	1.02	0.57 - 1.97	0.066	0.947
Need for surgical intervention
Obesity - normal weight	4.38	1.53 - 15.77	2.546	0.033
Overweight - normal weight	2.11	0.73 - 7.61	1.277	0.202
Age	1.04	1.00 - 1.08	1.970	0.049
Sex (female - male)	1.36	0.61 - 2.87	0.791	0.429
Diabetes	1.05	0.49 - 2.19	0.116	0.907
Hypertension	2.08	0.61 - 13.09	0.991	0.322
6-month mortality
Obesity - normal weight	0.62	0.16 - 2.13	-0.739	0.460
Overweight - normal weight	0.82	0.29 - 2.33	-0.391	0.695
Age	1.09	1.04 - 1.16	3.141	0.002
Sex (female - male)	1.66	0.65 - 4.11	1.098	0.272
Diabetes	4.86	1.73 - 17.32	2.764	0.006
Hypertension	2.54	0.51 - 46.35	0.898	0.369
1-year follow-up
Rehospitalization
Obesity - normal weight	0.69	0.21 - 2.16	-0.614	0.539
Overweight - normal weight	1.50	0.64 - 3.80	0.906	0.365
Age	0.98	0.94 - 1.02	-0.955	0.339
Sex (female - male)	2.65	1.23 - 5.68	2.531	0.011
Diabetes	2.05	0.95 - 4.57	1.800	0.072
Hypertension	0.42	0.18 - 1.04	-1.999	0.046

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[1] *
These authors contributed equally to this work and share first authorship.