Effect of Obesity on Mortality and Morbidity After Coronary Artery Bypass Grafting Surgery in Iranian Patients

authors:

avatar Maryam Ardeshiri 1 , avatar Zahra Faritous 1 , * , avatar Zahra Ojaghi Haghighi 1 , avatar Shirin Hosseini 1 , avatar Ramin Baghaei 1

Rajaie Cardiovascular Medical and Research Center, Iran University of Medical Sciences, Tehran, Iran

how to cite: Ardeshiri M, Faritous Z, Ojaghi Haghighi Z, Hosseini S, Baghaei R. Effect of Obesity on Mortality and Morbidity After Coronary Artery Bypass Grafting Surgery in Iranian Patients. Anesth Pain Med. 2014;4(2):e18884. https://doi.org/10.5812/aapm.18884.

Abstract

Background:

Recent years have witnessed the emergence of obesity as a major public health concern. The drastic rise in obesity and its concomitant co-morbidities is a reflection of the recent changes in dietary habits in Iran and many other developing countries. A recent large population study in Tehran reported that 58% and 75% of middle-aged Iranian men and women, respectively, were either overweight or obese.

Objectives:

Considering the impact of obesity on mortality and morbidity after coronary artery bypass graft surgery (CABG), we sought to investigate the association between central obesity and the body mass index (BMI) and the post-CABG mortality and morbidity in Iranian patients.

Patients and Methods:

This prospective study was on 235 adult patients scheduled for isolated CABG in a university hospital. The patients were divided in two groups according to BMI ≥ 30 (obese; n = 60) and BMI < 30 (non-obese; n = 175). In-hospital and late (after 3 months) morbidity and mortality rates were compared between obese and non-obese patients.

Results:

A total of 235 patients (135 women) with a mean age of 59 ± 9.2 years (range = 29 to 79 years), mean BMI of 27.3 ± 4.2 (range = 17 to 40), and mean waist circumference of 101.2 ± 14.7 cm (range = 55 to 145 cm) were included. By the third postoperative month, wound infection had significantly increased in patients with BMI ≥ 30 (P = 0.022). In-hospital and late morbidity and mortality rates were comparable between the two groups (P > 0.05).

Conclusions:

In our patients obesity was a risk factor for wound infection but not atelectasis or the need for intra-aortic balloon pump or re-exploration. Obesity was not associated with increased in-hospital or 3 months mortality rates after CABG.

1. Background

Recent years have witnessed the emergence of obesity as a major public health concern. The drastic rise in obesity and its concomitant co-morbidities is a reflection of the recent changes in dietary habits in Iran (1) and many other developing countries (2). A recent large population study in Tehran reported that 58% and 75% of middle-aged Iranian men and women, respectively, were either overweight or obese (3). Obesity can promote the atherosclerotic process by disrupting the endothelial function as well as enhancing oxidative stress and induction of pro-inflammatory states (4, 5).

2. Objectives

Obesity is, therefore, regarded as a risk factor for mortality and morbidity after coronary artery bypass graft surgery (CABG) (6-9). There is a relatively wide divergence of opinions on the relationship between the body mass index (BMI) and post-CABG morbidity and mortality in the current literature: There is a school of thought maintaining that BMI is not a risk factor for mortality (10, 11), whilst some other investigators consider obesity as a protective factor in patients undergoing CABG (12). What most experts agree on its relation with post-CABG complications, however, is waist circumference (WC), which is deemed the best and most simple anthropometric measurement for central obesity. Yet no previous study has hitherto evaluated the effect of obesity, in terms of WC, on post-CABG morbidity and mortality in Iran. We, therefore, aimed to investigate the association between obesity (BMI) and mortality and morbidity rates in Iranian patients following CABG.

3. Patients and Methods

3.1. Study Population

Between March, 2010 and February, 2011, 235 patients with age over 18 years, and coronary artery disease who were referred to a university cardiovascular and research center for isolated CABG were investigated. The institutional approval number was 88.28. This is an analytic study. In all patients with American Society of Anesthesiologists (ASA) physical status class II or III, preoperative and operative data were prospectively collected and entered into a computerized database. The anaesthetic and surgical techniques were standardized for all of the patients. Anesthesia was induced using midazolam or propofol plus sufentanil and cisatracuriumor atracurium, followed by infusion dose of these drugs. Midline sternotomy, hypothermia 30-32 °C, and antegrade cold blood cardioplegia were used. Demographic and baseline data, clinical information, and ICU sheets in addition to data on risk factors, medication, and functional status were obtained by trained personnel supervised by a research nurse. Postoperative complications were also recorded prospectively by a researcher, and all major adverse events were prospectively validated by an experienced cardiac surgeon according to standard clinical definitions. All the patients were followed up in hospital and for a three-month follow-up period; follow-up was completed by all the patients. The exclusion criteria included: age < 18 years, severe co-morbidities, history of valvular heart disease, concomitant procedures, and low left ventricular ejection fraction (LVEF < 35%) on admission echocardiography. This study was approved by the institutional ethics committee and informed consent was obtained from all patients. This study was not been financially supported by any funding resource.

3.2. Clinical, Anthropometrical, and Laboratory Measurements

The patients’ characteristics, including age, sex, history of diabetes mellitus (DM), hypertension, hyperlipidemia, smoking, BMI, waist circumference, fasting blood glucose and cholesterol and triglyceride levels, were collected. N number and sites of the grafts were also recorded.

3.3. Definition of Obesity

BMI was measured as weight in kilograms divided by height in square meters (Kg/m2). Patients with BMI ≥30 Kg/m2 were classified as obese and those with BMI < 30 Kg/m2 considered as non-obese. WC was measured by placing a tape measure horizontally at the level of the iliac crest in non-stress situation. WC ≥102 cm in men and 88 cm in women was considered as obesity, and WC < 102 cm in men and < 88 cm in women was defined as non-obesity (13).

3.4. Outcomes Follow Up

The primary end-point of our study was operative mortality, defined as death from any cause occurred in-hospital and within three months after surgery. Cardiac and non-cardiac morbidities constituted the secondary end-points, which included arrhythmias, sepsis, heart failure cardiogenic shock (systolic blood pressure < 90 mmHg with no or poor response to fluids and requiring administration of inotropic infusions to maintain blood pressure and requirement for an intra-aortic balloon pump), aortic cross-clamp time atelectasia, re-intubation, renal failure, intra-aortic balloon pump requirement, bleeding, wound infection, lung infection, re-exploration, multi organ failure, tamponade, myocardial infarction, bedsore, pulmonary embolism, mechanical ventilation time (hour), ICU stay time (day) and re-admission due to mediastinitis. The criterion for postoperative sepsis was the occurrence of a positive blood culture. The criterion for lung infection was a positive culture of the sputum plus a radiological infiltration. The criterion for postoperative renal failure was a 50% increase in the baseline serum creatinin level. Multiorgan failure was defined as involvment of two or more organ systems. Mediastinitis was diagnosed when a deep sternal infection was present, necessitating exploration of the wound with excision of tissues and treatment with antibiotics. Mortality was defined as in-hospital death and death within a three-month period after the operation. All the follow-up data were collected when the patient was discharged for a period of three months following CABG. Follow-up was completed by all patients.

3.5. Statistical Analysis

The data are described as mean ± standard deviation (SD) for interval and count (%) for categorical variables. We used the chi-square test for categorical variables and student’s t test for numerical variables. P value ≤ 0.05 was considered as statistically significant result. SPSS® 15.0 for Windows® (SPSS Inc. Chicago, Illinois) was used for statistical analyses.

4. Results

4.1. Background Data

A total of 235 patients (135 women) with a mean age of 59 ± 9.2 years (range = 29 to 79 years), mean BMI of 27.3 ± 4.2 kg/m2 (range = 17 to 40 kg/m2), and mean WC of 101.2 ± 14.7 cm (range = 55 to 145 cm) were recruited in the present study. Table 1 depicts the descriptive data on the study population’s background and demographics in obese and non-obese patients, and Table 2 illustrates the postoperative outcomes compared between the two groups.The mean age in patients with BMI ≥30 kg/m2 (59 ± 8.7 kg/m2) was lower than that in patients with BMI < 30 kg/m2 (60 ± 9.5 kg/m2), but this difference was not statistically significant. Those with BMI ≥30 were more likely to be female (P < 0.001) and have diabetes mellitus (P = 0.033). Total serum cholesterol (P < 0.001), serum low-density lipoprotein (P < 0.001), serum triglyceride (P = 0.016), WC (P < 0.001), and ejection fraction (P = 0.037) were significantly higher in the obese patients (BMI ≥ 30), whilst smoking was more frequent in those with BMI < 30 (P = 0.027). There was no difference between the site of coronary involvement and obesity when patients were startified according to their BMI. Eight 8 (57.1%) of male patients and 30 (65.2%) of female patients with BMI ≥ 30 had DM (P = 0.004), and 7 (23.3%) of male patients and 23 (76.7%) of female patients with BMI ≥ 30 had dyslipidemia (P = 0.034; Table 3).

Table 1.

The General Characteristics of Patients According to Body Mass Index (BMI) a

Characteristic / VariableTotal (n = 235)BMI < 30 (n = 175)BMI ≥ 30 (n = 60)P value
Age, y59 ± 9.260 ± 9.559 ± 8.70.386
Gender, Female/Male135/10089/86(6/14)< 0.001 b
Diabetes mellitus121 (51.5)83 (47.4)38 (63.3)0.033 b
Hyperlipidemia (history)107 (45.5)77 (44)30 (50)0.421
Hypertension136 (57.9)99 (56.6)37 (61.7)0.49
Waist Circumference, cm101.2 ± 14.797.9 ± 14.2110.8 ± 11.7< 0.001 b
Addiction28 (12)24 (13.8)4 (6.7)0.141
Alcohol1 (0.4)1 (0.6)00.557
Smoking20 (8.5)19 (10.9)1 (1.7)0.027 b
Ejection Fraction, %45.2 ± 9.544.5 ± 9.647.5 ± 90.037 b
Para-Clinical Finding
Fasting Serum Glucose, mg/dl145 ± 60.4142 ± 60.1153.82 ± 610.085
Total Serum Cholesterol, mg/dl174.3 ± 53.8166.8 ± 49.6196.1 ± 59.8< 0.001 b
Serum High Density Lipoprotein, mg/dl39.8 ± 54.941.2 ± 63.335.8 ± 110.877
Serum Low Density Lipoprotein, mg/dl90.2 ± 37.485.7 ± 37.6103.4 ± 33.8<0.001 b
Serum Triglyceride, mg/dl201.1 ± 142.8186.7 ± 105.2243.3 ± 2140.016 b
Serum Creatinin, mg/dl1.3 ± 0.31.3 ± 0.31.2 ± 0.30.086
Involved Coronary Artery
Left Main6 (2.6)6 (3.4)00.15
Left Anterior Descending234 (99.6)174 (99.4)60 (100)0.557
Left Circumflex203 (86.4)155 (88.6)48 (80)0.095
Right Coronary Artery202 (86)152 (86.9)50 (83.3)0.498
Total graft number3.3 ± 0.93.3 ± 0.93.1 ± 0.90.048 b
Cardiopulmonary bypass time, min100.2 ± 55.3101.9 ± 56.995.5 ± 50.50.356
Cross-clamp time, min56.4 ± 42.956.2 ± 44.357 ± 390.499
Mechanical ventilation time, h25.1 ± 89.527.2 ± 103.419 ± 12.80.589

4.2. Early and Late Complications

The incidence of complications after three months was low. The only outcome which was significantly different among the BMI categories was wound infection (at three months’ follow-up) (P = 0.022), whilst three (5%) of the patients with BMI ≥ 30 kg/m2 had this complication at three months’ follow-up. Detailed outcomes, with regard to the BMI, are listed in Tables 2 and 3. Adjusted associations between the different outcomes and BMI ≥ 30, history of diabetes and sex were determined by logistic regression models; there was no statistically significant association between them. All the patients who died had central obesity, but the p value was not significant.

Table 2.

Post-Operative Outcomes According to Body Mass Index (BMI) a

Characteristic / VariableTotalBody Mass Index < 30 (n = 175)Body Mass Index ≥ 30 (n = 60)P value
Arrhythmia18 (7.7)16 (9.1)2 (3.3)0.144
Sepsis3 (1.3)3 (1.7)00.307
Congestive heart failure2 (0.9)1 (0.6)1 (1.7)0.425
Cardiac shock2 (0.9)2 (1.1)00.406
Atelectasia16 (6.8)12 (6.9)4 (6.7)0.961
Reintubation3 (1.3)2 (1.1)1 (1.7)0.755
Renal failure2 (0.9)2 (1.1)00.406
Intra-aortic balloon Pump9 (3.8)8 (4.6)1 (1.7)0.312
Bleeding20 (8.5)16 (9.1)4 (6.7)0.553
Wound infection9 (3.8)8 (4.6)1 (1.7)0.312
In-hospital death3 (1.3)3 (1.7)1 (1.7)0.982
Re-exploration8 (3.4)6 (3.4)2 (3.3)0.972
Lung infection4 (1.7)4 (2.3)00.238
Multi-organ failure000-
Tamponade3 (1.3)2 (1.1)1 (1.7)0.755
Myocardial infarction12 (5.1)10 (5.7)2 (3.3)0.473
Bedsore7 (3)5 (2.9)2 (3.3)0.851
Pulmonary embolism3 (1.3)2 (1.1)1 (1.7)0.755
ICU stay time, day b4.9 (3-8)5.2 (3-10)4± (3-6)0.542
Sepsis, after 3 months000-
Cardiac Shock, after 3 months1 (0.4)1 (0.6)00.557
Wound Infection, after 3 months4 (1.7)1 (0.6)3 (5)0.022 c
Death, after 3 months4 (1.4)2 (1.1)1 (1.7)0.755
Lung Infection, after 3 months2 (0.9)1 (0.6)1 (1.7)0.425
Myocardial Infarction, after 3 months3 (1.3)2 (1.1)1 (1.7)0.755
Pulmonary Emboli, after 3 months8 (3.4)7 (4)1 (1.7)0.391
Re-admission, after 3 months24 (10.2)18 (10.3)6 (10)0.952
Mediastinitis, after 3 months9 (3.8)7 (4)2 (3.3)0.816
Table 3.

Post-Operative Outcomes According to BMI in Both Sexes a

Characteristic/ VariableBMI < 30BMI ≥ 30P value b
Women = 89Men = 86Women = 46Men = 14
Diabetes52 (58.4)31 (36)30 (65.2)8 (57.1)0.004b
Hyperlipidemia (History)47 (61)30 (39)23 (76.7)7 (23.3)0.034b
HDL-Dyslipidemia c75 (84.3)65 (75.6)42 (91.3)9 (64.3)0.025b
Arrhythmia10 (11.2)6 (7)2 (4.3)00.244
Sepsis1 (1.1)2 (2.3)000.549
Congestive heart failure01 (1.2)01 (7.1)-
Cardiac Shock2 (2.2)000-
Atelectasia8 (9)4 (4.7)4 (8.7)00.132
Re-intubation02 (2.3)1 (2.2)00.32
Renal Failure2 (2.2)000-
Intra-Aortic balloon Pump4 (4.5)4 (4.7)010.58
Bleeding7 (7.9)9 (10.5)3 (6.5)1 (7.1)0.561
Wound Infection4 (4.5)4 (4.7)1 (2.2)00.908
In-hospital death2 (2.2)1 (1.2)1 (2.2)00.463
Re-exploration3 (3.4)3 (3.5)1 (2.2)1 (7.1)0.672
Lung Infection2 (2.2)2 (2.3)000.972
Multi organ failure0000-
Tamponade2 (2.2)01 (2.2)0-
Myocardial Infarction4 (4.5)6 (7)2 (4.3)00.701
Bedsore5 (5.6)01 (2.2)1 (7.1)0.2
Pulmonary Embolism2 (2.2)01 (2.2)0-
ICU stay time, dayd5.5 (3-11)4.9 (3-10)4 (3-8)4 (3-9)0.823
Cardiopulmonary bypass time, min95.1 ± 48.2109 ± 64.289.9 ± 46.1113.7 ± 61.20.598
Cross Clamp Time, min50.6 ± 35.561.9 ± 51.554.3 ± 37.165.6 ± 44.90.123
Mechanical ventilation time, h32.4 ± 143.221.8 ± 24.817.8 ± 9.523.1 ± 20.30.603
Sepsis, after 3 months0000-
Cardiac Shock, after 3 months01 (1.2)00-
Wound Infection, after 3 months1 (1.1)03 (6.5)0-
Death, after 3 months1 (1.1)1 (1.2)1 (2.2)00.785
Lung Infection, after 3 months01 (1.2)1 (2.2)00.643
Myocardial Infarction, after 3 months2 (2.2)01 (2.2)0-
Pericardial Effusion, after 3 months2 (2.2)5 (5.8)1 (2.2)00.329
Re-admission, after 3 months9 (10.1)9 (10.5)6 (13)00.57
Mediastinitis, after 3 months5 (5.6)2 (2.3)2 (4.3)00.192

5. Discussion

Our study showed a high prevalence of obesity in coronary artery disease patients scheduled for CABG. The prevalence of obesity in our patients, as indicated by BMI, was 25.5%, which is in agreement with some previous studies. However, it has been posited that WC is a stronger predictor of cardiovascular disease outcomes than BMI (14). Recent studies have demonstrated a dramatic rise(as high as 35%) in the prevalence of obesity in the Iranian population and Asian countries (15). It is worth noting that the number of obese patients undergoing CABG has also been on the increase in recent years (16). Intra-abdominal fat is resistant to insulin, giving rise to hyperlipidemia, glucose intolerance, hypertension and atherosclerosis. These conditions, in turn, induce adipokinase and enhance chronic low-grade inflammation (17). Consistent with the findings of some previous studies, females accounted for the majority of our obese patients (8). The frequency of diabetes and hyperlipidemia was also high in female patients in comparison with their male counterparts. In contrary, some investigators have suggested that obesity is a protective factor in patients undergoing CABG (18-20). The wound infection rates at three months’ follow-up post-CABG were high in our obese patients in comparison with our non-obese patients, which is in agreement with the findings of some previous studies (21-24). Some studies have not found any difference between obese and non-obese patients in terms of morbidity (25-27) and mortality (10, 11, 28). But others have demonstrated that the rates of ventricular tachycardia 10, myocardial infarction, hospital admission times (10, 24, 29) and atrial fibrillation (24) are significantly lower in obese patients. In our study, there was no association between obesity and mortality. However, some investigations have reported a significant difference regarding mortality between obese and non-obese patients undergoing CABG (29, 30). The impact of obesity on mortality may have decreased over time and it is thought to be related to the decline in the prevalence of cardiovascular risk factors and improvements in public health and medical care (29). This discrepancy in the aforementioned findings may be due to the differences in the definitions of obesity, cut-off points for group classification, study durations, and patient selection criteria. Moreover, what can also impact the outcome of a study is whether the study population is composed of emergent or non-emergent patients or whether some other surgical procedures are performed in tandem with CABG. The short follow-up duration of the present study is its most significant limitation. Studies with longer follow-up durations are required to shed further light on this issue. In our patients obesity was a risk factor for wound infection but not atelectasis, intra-aortic balloon pump or re-exploration. In this study obesity did not predict increased in-hospital or three months mortality rates after CABG. Patients with central obesity have more established coronary artery disease and CABG may be necessary for many obese persons. Therefore, they benefit from early aggressive risk reduction. It is, therefore, advisable that obesity (especially central obesity) in patients scheduled for CABG be identified and managed aggressively in order to reduce morbidity.

Acknowledgements

References

  • 1.

    Iranian Ministry of Health and Medical Education: a national survey on health and diseases in Iran.;. 2000.

  • 2.

    Ghassemi H, Harrison G, Mohammad K. An accelerated nutrition transition in Iran. Public Health Nutr. 2002;5(1A):149-55. [PubMed ID: 12027278]. https://doi.org/10.1079/PHN2001287.

  • 3.

    Azizi F, Salehi P, Etemadi A, Zahedi-Asl S. Prevalence of metabolic syndrome in an urban population: Tehran Lipid and Glucose Study. Diabetes Res Clin Pract. 2003;61(1):29-37. [PubMed ID: 12849921].

  • 4.

    Lindhout AH, Wouters CW, Noyez L. Influence of obesity on in-hospital and early mortality and morbidity after myocardial revascularization. Eur J Cardiothorac Surg. 2004;26(3):535-41. [PubMed ID: 15302048]. https://doi.org/10.1016/j.ejcts.2004.05.034.

  • 5.

    Bays HE, Gonzalez-Campoy JM, Bray GA, Kitabchi AE, Bergman DA, Schorr AB, et al. Pathogenic potential of adipose tissue and metabolic consequences of adipocyte hypertrophy and increased visceral adiposity. Expert Rev Cardiovasc Ther. 2008;6(3):343-68. [PubMed ID: 18327995]. https://doi.org/10.1586/14779072.6.3.343.

  • 6.

    Eagle KA, Guyton RA, Davidoff R, Ewy GA, Fonger J, Gardner TJ, et al. ACC/AHA guidelines for coronary artery bypass graft surgery: executive summary and recommendations : A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to revise the 1991 guidelines for coronary artery bypass graft surgery). Circulation. 1999;100(13):1464-80. [PubMed ID: 10500052].

  • 7.

    Brandt M, Harder K, Walluscheck KP, Schottler J, Rahimi A, Moller F, et al. Severe obesity does not adversely affect perioperative mortality and morbidity in coronary artery bypass surgery. Eur J Cardiothorac Surg. 2001;19(5):662-6. [PubMed ID: 11343949].

  • 8.

    Reeves BC, Ascione R, Chamberlain MH, Angelini GD. Effect of body mass index on early outcomes in patients undergoing coronary artery bypass surgery. J Am Coll Cardiol. 2003;42(4):668-76. [PubMed ID: 12932599].

  • 9.

    Potapov EV, Loebe M, Anker S, Stein J, Bondy S, Nasseri BA, et al. Impact of body mass index on outcome in patients after coronary artery bypass grafting with and without valve surgery. Eur Heart J. 2003;24(21):1933-41. [PubMed ID: 14585252].

  • 10.

    Engel AM, McDonough S, Smith JM. Does an obese body mass index affect hospital outcomes after coronary artery bypass graft surgery? Ann Thorac Surg. 2009;88(6):1793-800. [PubMed ID: 19932237]. https://doi.org/10.1016/j.athoracsur.2009.07.077.

  • 11.

    Gruberg L, Weissman NJ, Waksman R, Fuchs S, Deible R, Pinnow EE, et al. The impact of obesity on the short-term and long-term outcomes after percutaneous coronary intervention: the obesity paradox? J Am Coll Cardiol. 2002;39(4):578-84. [PubMed ID: 11849854].

  • 12.

    Sung SH, Wu TC, Huang CH, Lin SJ, Chen JW. Prognostic impact of body mass index in patients undergoing coronary artery bypass surgery. Heart. 2011;97(8):648-54. [PubMed ID: 21330312]. https://doi.org/10.1136/hrt.2010.211110.

  • 13.

    Expert Panel on Detection E, Treatment of High Blood Cholesterol in A. Executive Summary of The Third Report of The National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, And Treatment of High Blood Cholesterol In Adults (Adult Treatment Panel III). JAMA. 2001;285(19):2486-97. [PubMed ID: 11368702].

  • 14.

    Haffner SM. Waist circumference and BMI are both independently associated with cardiovascular disease. The International Day for the Evaluation of Abdominal Obesity (IDEA) survey. J Amer Coll Cardiol. 2006;47(4):358.

  • 15.

    Zabetian A, Hadaegh F, Azizi F. Prevalence of metabolic syndrome in Iranian adult population, concordance between the IDF with the ATPIII and the WHO definitions. Diabetes Res Clin Pract. 2007;77(2):251-7. [PubMed ID: 17234299]. https://doi.org/10.1016/j.diabres.2006.12.001.

  • 16.

    The Society of Cardiothoracic Surgeons of Great Britain and Ireland. National audit cardiac surgical database report.;. 2001.

  • 17.

    van Harmelen V, Dicker A, Rydén M, Hauner H, Lönnqvist F, Näslund E, et al. Increased Lipolysis and Decreased Leptin Production by Human Omental as Compared With Subcutaneous Preadipocytes. Diabetes. 2002;51(7):2029-36. [PubMed ID: 12086930]. https://doi.org/10.2337/diabetes.51.7.2029.

  • 18.

    Yazdanian F, Faritous SZ, Mollasadeghi G, Nejad MH, JamshidKhamoushi A. Impact of Body Mass Index on In-Hospital Mortality and Morbidity after Coronary Artery Bypass Grafting Surgery. J Tehran Univ Heart Center. 2008;3(1).

  • 19.

    Shirzad M, Karimi A, Dowlatshahi S, Ahmadi SH, Davoodi S, Marzban M, et al. Relationship between body mass index and left main disease: the obesity paradox. Arch Med Res. 2009;40(7):618-24. [PubMed ID: 20082879]. https://doi.org/10.1016/j.arcmed.2009.10.005.

  • 20.

    Niraj A, Pradhan J, Fakhry H, Veeranna V, Afonso L. Severity of coronary artery disease in obese patients undergoing coronary angiography: "obesity paradox" revisited. Clin Cardiol. 2007;30(8):391-6. [PubMed ID: 17680619]. https://doi.org/10.1002/clc.20113.

  • 21.

    Kim J, Hammar N, Jakobsson K, Luepker RV, McGovern PG, Ivert T. Obesity and the risk of early and late mortality after coronary artery bypass graft surgery. American heart journal. 2003;146(3):555-60.

  • 22.

    Habib RH, Zacharias A, Schwann TA, Riordan CJ, Durham SJ, Shah A. Effects of obesity and small body size on operative and long-term outcomes of coronary artery bypass surgery: a propensity-matched analysis. Ann Thorac Surg. 2005;79(6):1976-86. [PubMed ID: 15919295]. https://doi.org/10.1016/j.athoracsur.2004.11.029.

  • 23.

    Lu JC, Grayson AD, Jha P, Srinivasan AK, Fabri BM. Risk factors for sternal wound infection and mid-term survival following coronary artery bypass surgery. Eur J Cardiothorac Surg. 2003;23(6):943-9. [PubMed ID: 12829070].

  • 24.

    Tolpin DA, Collard CD, Lee VV, Elayda MA, Pan W. Obesity is associated with increased morbidity after coronary artery bypass graft surgery in patients with renal insufficiency. J Thorac Cardiovasc Surg. 2009;138(4):873-9. [PubMed ID: 19660351]. https://doi.org/10.1016/j.jtcvs.2009.02.019.

  • 25.

    Del Prete JC, Bakaeen FG, Dao TK, Huh J, LeMaire SA, Coselli JS, et al. The impact of obesity on long-term survival after coronary artery bypass grafting. J Surg Res. 2010;163(1):7-11. [PubMed ID: 20452615]. https://doi.org/10.1016/j.jss.2010.02.014.

  • 26.

    Baslaim G, Bashore J, Alhoroub K. Impact of obesity on early outcomes after cardiac surgery: experience in a Saudi Arabian center. Ann Thorac Cardiovasc Surg. 2008;14(6):369-75. [PubMed ID: 19131923].

  • 27.

    Orhan G, Bicer Y, Aka SA, Sargin M, Simsek S, Senay S, et al. Coronary artery bypass graft operations can be performed safely in obese patients. Eur J Cardiothorac Surg. 2004;25(2):212-7. [PubMed ID: 14747115].

  • 28.

    Gurm HS, Brennan DM, Booth J, Tcheng JE, Lincoff A, Topol EJ. Impact of body mass index on outcome after percutaneous coronary intervention (the obesity paradox). J Am Coll Cardiol. 2002;90(1):42-5.

  • 29.

    Kuduvalli M, Grayson AD, Oo AY, Fabri BM, Rashid A. Risk of morbidity and in-hospital mortality in obese patients undergoing coronary artery bypass surgery. Eur J Cardiothorac Surg. 2002;22(5):787-93. [PubMed ID: 12414047].

  • 30.

    Rajaei S, Dabbagh A. Risk factors for postoperative respiratory mortality and morbidity in patients undergoing coronary artery bypass grafting. Anesth Pain Med. 2012;2(2):60-5. [PubMed ID: 24223339]. https://doi.org/10.5812/aapm.5228.