07/08. tbl. 105. árg. 2019

No significant association between obesity and long-term outcome of coronary artery bypass grafting

Engin marktæk tengsl offitu og lifunar eftir kransæðahjáveituaðgerð

Objectives: Our objective was to investigate long-term outcomes of obese patients undergoing coronary artery bypass grafting (CABG) in Iceland.

Materials and methods: A retrospective analysis on 1698 patients that underwent isolated CABG in Iceland between 2001-2013. Patients were divided into four groups according to body mass index (BMI); Normal=18.5-24.9kg/m2 (n=393), ii) overweight=25-29.9 kg/m2 (n=811), iii) obese=30-34.9 kg/m2 (n=388) and iv) severely obese ≥35kg/m2 (n=113). Thirty-day mortality and short-term complications were documented as well as long-term complications that were pooled into major adverse cardiac and cerebrovascular events (MACCE) and included myocardial infarction, stroke, repeated CABG, percutaneous coronary intervention with or without stenting, and death. After pooling the study groups, survival and freedom from MACCE plots (Kaplan- Meier) were generated and Cox regression analysis used to identify predictive factors of survival. Average follow-up time was 5.6 years.

Results: Severely obese and obese patients were significantly younger than those with a normal BMI, more often males with identifiable risk factors of coronary artery disease (CAD) and a lower EuroSCORE II (1.6 vs. 2.7, p=0.002). The incidence of major early complications, 30-day mortality (2%), long-term survival (90% at 5 years, log-rank test p=0.088) and MACCE-free survival (81% at 5 years, log-rank test p=0.7) was similar for obese and non-obese patients. BMI was neither an independent predictor for long-term (OR: 0.98 95%-CI: 0.95-1.01) nor MACCE-free survival (OR: 1.0 95%-CI: 0.98-1.02).

Conclusions: Obese patients that undergo CABG in Iceland are younger and have an increased number of risk factors for coronary disease when compared to non-obese patients. However, BMI neither predicted long-term survival or long-term complications. The outcomes following CABG in obese patients are good in Iceland.


Tables and figures

Figure1a. Kaplan-Meier curves comparing overall survival of the four weight groups (p=0.088, log-rank test).

Figure1b. Kaplan-Meier curves comparing survival without MACCE (Major adverse cardiac and cerebrovascular event) of the four weight groups (p=0.7, log-rank test).


Table I. Comparison of preoperative patient demographics for patients in different BMI groups that underwent CABG surgery during the years 2001-2013 in Iceland. Values are mean with standard deviation or number (%).


Total
(n=1705)
Normal weight
(n=393)
Overweight
(n=811)
Obese class I
(n=388)
Obese class II&III
(n=113)
p-value
Age 66 ± 9.4 67 ± 10 66 ± 9 65 ± 9 61 ± 9 < 0.001
Male 1437 (82) 304 (77) 687 (85) 315 (81) 86 (76) 0.007












Risk factors for cardiovascular disease

Hypertension 1143 (65) 218 (55) 530 (66) 266 (68) 93 (82) < 0.001
Diabetes 280 (16) 41 (11) 116 (14) 74 (19) 41 (37) < 0.001
Dyslipidemia 992 (56) 203 (53) 460 (58) 224 (60) 76 (72) 0.006
Smoking history 1260 (56) 268 (68) 568 (70) 300 (77) 89 (79) 0.006
Family history of CAD 910 (52) 195 (52) 431 (55) 198 (54) 62 (61) 0.44

*Coronary artery disease







Other preoperative patient demographics

EuroSCORE II 2.2 ± 3.6 2.8 ± 3.9 2.2 ± 3.5 1.8 ± 2.4 1.6 ± 1.3 < 0.001
CCS class 3-4 1326 (76) 283 (72) 619 (76) 298 (77) 93 (82) 0.51
NYHA class 3-4 784 (44) 175 (54) 359 (54) 174 (54) 58 (62) 0.49
LVEF 55 ± 9.9 55 ± 10 55 ± 10 55 ± 9,5 55 ± 8,6 0.58
Three vessel CAD and/or left main stem disease 1574 (90) 346 (88) 739 (91) 346 (89) 107 (95) 0.12
CKD* 237 (14) 59 (15) 102 (13) 53 (14) 17 (15) 0.09
COPD 126 (7) 37 (9) 48 (6) 32 (8) 4 (4) 0.08

*GSH<60 ml/min/1,73 m2

History of cardiovascular disease

History of MI 446 (25) 114 (29) 197 (24) 102 (26) 23 (20) 0.18
History of arrythmia 179 (10) 42 (11) 77 (10) 39 (10) 13 (12) 0.87
History of valve disease 41 (3) 10 (3) 21 (3) 14 (4) 4 (4) 0.69
Previous PCI 369 (21) 68 (17) 177 (22) 81 (21) 28 (25) 0.22









Preoperative medications

Beta-blockers 1184 (67) 256 (68) 537 (71) 267 (72) 90 (83) 0.017
Statins 1318 (75) 277 (74) 599 (77) 311 (83) 95 (88) <0.001
Acetylsalicylic acid (aspirin) 652 (30) 116 (29) 309 (39) 136 (35) 56 (50) <0.001
Heparin 768 (44) 169 (43) 356 (44) 160 (42) 53 (47) 0.58
Clopidogrel 64 (4) 12 (3) 30 (3,8) 11 (2,8) 6 (5,3) 0.56


Table II. Operative variables, length of stay, short-term minor and major complications and 30 day mortality following CABG in Iceland 2001-2013, stratified by BMI. Values are mean with standard deviation or number (%).


Total
(n=1705)
Normal weight
(n=393)
Overweight
(n=811)
Obese class I
(n=388)
Obese class II&III
(n=113)
p-value
OPCAB 380 (22) 90 (23) 168 (21) 90 (23) 26 (23) 0.71
Lenth of operation(min) 212 ± 52 207 ± 52 208 ± 55 219 ± 58 232 ± 61 < 0.001
Clamp time(min) 46 ± 17 45 ± 16 47 ± 16 48 ± 20 49 ± 18 0.043
LIMA used 1652 (94) 360 (91) 767 (95) 365 (94) 111 (98) 0.039
No. of distal anastomoses 3.5 (1-6) 3.4 (1-6) 3.5 (1-6) 3.5 (1-6) 3.5 (1-5) 0.55
Bleeding < 24 hrs, (ml) 981 ± 1007 1075 ± 807 957 ± 614 974 ± 1707 897 ± 719 0.21
Red blood cell transfusion(units) 2.6 ± 5 3.3 ± 6 2.6 ± 4 2.2 ± 6 2.4 ± 5 0.005
ICU stay (days) 1.9 ± 3 1.9 ± 3 2 ± 3 1.7 ± 3 2 ± 3 0.43
Total length of stay(days) 11 ± 8 12 ± 8 11 ± 7 11 ± 8 13 ± 13 0.02


Minor complications 855 (49) 195 (49) 394 (48) 186 (48) 58 (51) 0.92
Superficial wound infection 183 (10) 39 (10) 72 (8,9) 43 (11) 23 (20) 0.003
New onset atrial fibrillation/flutter 579 (33) 133 (34) 282 (35) 125 (32) 30 (27) 0.33
Drainage of pleural effusion 197 (11) 65 (16) 83 (10) 32 (8) 9 (8) < 0.001
Pneumonia 115 (7) 30 (8) 52 (6) 25 (7) 6 (5) 0.79
Urinary tract infection 62 (4) 14 (4) 24 (3) 17 (4) 5 (4) 0.54
Major Complications 294 (17) 76 (19) 131 (16) 60 (16) 20 (18) 0.46
Acute kidney injury 14 (1) 4 (1) 4 (0,5) 4 (1) 2 (2) 0.27
Deep sternal wound infectons 16 (1) 0 (0) 8 (1) 4 (1) 2 (2) 0.08
Sternum dehischience 27 (2) 4 (1) 12 (1) 9 (2) 2 (2) 0.48
Stroke 23 (1) 7 (2) 8 (1) 4 (1) 3 (3) 0.29
Multi-organ failure 55 (3) 15 (4) 25 (3) 8 (2) 6 (5) 0.26
30 day mortality 42 (2) 12 (3) 17 (2) 9 (2) 2 (12) 0.77


Table IIIa. Independent risk factors for death following CABG in Iceland 2001-2013 (Cox regression analysis).

Variables HR 95% CI p-value
Diabetes 1.98 1.48-2.66 < 0.001
Congestive heart failure, EF < 30% 1.98 1.24-3.15 0.004
Decreased kidney function* 1.93 1.40-2.66 < 0.001
COPD 1.65 1.13-2.40 0.009
LVEF 30 – 50% 1.24 0.96-1.62 0.1
EuroSCORE II 1.07 1.03-1.11 < 0.001
Age 1.07 1.05-1.09 < 0.001
Year of operation 0.91 0.87-0.96 < 0.001
Use of statins 0.76 0.58-0.99 0.044
Body mass index 0.98 0.95-1.01 0.87
*GSH<60 ml/min/1,73 m2


Table IIIb. Independent risk factors for MACCE following CABG in Iceland 2001-2013 (Cox regression analysis).

Variables HR 95% CI p-value
Congestive heart failure, EF < 30% 1.89 1.27 – 2.79 0.002
History of percutaneous coronary intervention 1.79 1.36 – 2.35 < 0.001
Decreased kidney function* 1.53 1.17 – 2.00 0.002
COPD 1.41 1.03 – 1.93 0.034
Diabetes 1.35 1.06 – 1.72 0.014
EuroSCORE-II 1.07 1.04 – 1.10 < 0.001
Age 1.03 1.02 – 1.04 < 0.001
Year of operation 0.96 0.93 – 1.00 < 0.035
Body mass index 1 0.98 – 1.02 0.95
*GSH<60 ml/min/1,73 m2











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