To our knowledge, the present study was the first investigating the relationship between angiographic severity and early postoperative hemodynamic derangement in overweight patients. We found that Gensini angiographic severity score was also an independent predictor of LCOS after CABG, together with those already known including cross clamp time and age.
In line with a number of previous studies, postoperative mortality and morbidities were not too more common in this study but were close to mild risky population, roughly suggesting that obesity itself does not add too much risk for development of various complications after CABG. However, the number of our patients was limited to prove or disprove the presence of an obesity paradox since this term has been suggested upon researching on thousands of patients. Nevertheless, among the whole of overweight patients, some are supposed to be more likely to develop LCOS after surgery, which is often the case in all different populations undergoing CABG. Our retrospective observations provided that having higher angiographic severity scores might be the unique characteristics of such patients.
Why investigate whether there is a relationship between angiographic severity and CABG outcomes, whilst obesity paradox and its relevance have already been revealed in over weight population undergoing CABG? First, previous studies have fallen short in giving robust data establishing such paradox and been biased by several factors. In a recent study by Ardeshiri et al. 15, authors reported that there was no significant difference between patients with a BMI lower or higher than 30 kg/m2 in regard to many CABG outcomes. However early outcomes such as cardiogenic shock, requirement of intraaortic balloon pump and myocardial infarction occurred in only a few patients in overweight group where total number of patients was 60. In another study on overweight patients undergoing CABG, Benedetto et al. 16 reported that obesity was not protective for late date after CABG although overweight status was not associated with increased risk of death early after the operation. Although this study results were based on 3821 obese patients initially, a propensity score analysis was performed to match two groups by confounders. Final analyses were performed n matched 203 patients. This approach is subject to criticism since an overmatch bias seems likely because patients with known risk factors that are almost unique to obese individuals in real life have totally been left outside the analysis. Producing a near-normal except high-weight population, this study fell short focusing the main problematic proportion of the overweight patients undergoing CABG operation. Stamou et al. 17 reporterd the presence of obesity paradox in their study on 2440 patients undergoing CABG (isolated and combined) but, in controversy, they did not perform any baseline matching between patients with or without high BMI. Patients in high weight and obesity groups were significantly younger and they significantly more tend to have diabetes and three vessel diseases, this time producing and important patient selection bias. Le-Bert et al. 8 sought to clarify the same issue on elderly obese patients under-going CABG and reported that obesity in elderly did not demonstrate an increased risk of postsurgical complications after CABG. In this study, intraaortic balloon pump was required in 45 (26.9%) vs 27 (28.7%) patients in normal vs overweight patients, respectively (p :0.95). These figures, being close to those we found in our study, indicates that one-fourth of patients with high BMI have low cardiac output syndrome after CABG, if they are not young enough to tolerate harmful effects of cardiopulmonary bypass on myocardium.
Second, and more important, is that metabolic obesity rather than anatomic obesity has recently increased in popularity since metabolically healthy subjects with high BMI have a lower prevalence of cardiac risk factors, suggesting a new definition for obesity that should be based on fat distribution rather than body mass index 18. Recently there have been many studies pointing out the importance of distinguishing metabolically healthy obese patients from those with abnormal metabolic status. Mørkedal et al. 19 reported that obesity without metabolic abnormalities does not increase the risk of acute myocardial infarction but there was significant increase in risk of heart failure. Supporting this, Hamer et al. 20 reported that metabolically healthy obese individuals were not at increased risk of cardiovascular disease. On the contrary, Chang et al. 21 reported that patients with metabolically healthy obesity had a higher prevalence of subclinical atherosclerosis, indicating that obesity is harmful to coronary arteries regardless of its association with metabolic derangement. Nevertheless, the opposite of these findings was defended Rhee et al. 22. Importance of metabolically healthy status in overweight patients has thus still been controversial especially when cardiovascular disease prevalence or death was taken into consideration as the outcome parameters. Kwon et al. 23 sought to clarify the relationship between metabolic obesity and angiographic coronary artery disease. Based on Korean national classification, they defined the metabolic obesity as presence of 3 or more of the following; larger waist circumference, elevated highdensity lipoprotein cholesterol and triglyceride level, high blood pressure and diabetes. Their findings were interesting; metabolically obese but normal weight individuals had higher severity in angiography than metabolically healthy normal weight individuals after adjustment for various risk factors and metabolically obese individuals had higher angiographic severity than non-metabolically obesity after adjustment for age and sex. This study particularly draws attention to the importance of distinguishing patients with more severe coronary artery disease extension from those having mild involvement of coronary arteries with atherosclerosis.
We think that our study provided some information regarding the identification of more risky ones among those patients with high BMI submitted to CABG. Since the correlation between angiographic severity and presence of some cardiovascular risk factors (coexistence has recently been called as metabolic obesity) has been well established 24, it is not surprising to find out that angiographic severity may play an important role as an independent risk factor for development of LCOS after CABG.
Our study had several limitations. Retrospective design and lack of control group comprised of normal weight individuals was the major limitation. Use of certain criteria for determination of metabolic obesity and giving more detailed information which proportion our patients were indeed metabolically obese would have add much more information to the study. Finally, long term data could not to be provided because more than >50% patients could not respond to our invitation and also due to lack of adequate registry data regarding coronary artery disease outcomes.
In conclusion, we found that overweight patients with higher Gensini angiographic scores more tend to have low cardiac output syndrome after CABG than those with lower scores. Therefore, obesity paradox or in other words, protective effect of being overweight against adverse outcomes after CABG should be revisited in further study focusing on angiographic severity and its association with metabolic obesity since there seems to be an important cause and effect relationship between these two parameters.
Conflict of interest: None declared.