Original research Postgrad Med J: first published as 10.1136/postgradmedj-2020-138926 on 11 December 2020. Downloaded from Relative Fat Mass Index can be solution for obesity paradox in coronary artery disease severity prediction calculated by SYNTAX Score Süleyman Çağan Efe ,1 Ali Karagoz,1 Cem Dogan,1 Zubeyde Bayram,1 Sedat Kalkan,1 Mehmet Sait Altıntas,2 Yasin Yuksel,2 Turgut Karabag,2 Burak Ayca,2 Nihal Ozdemir1 1Cardiology, Kartal Kosuyolu ABSTRACT define obesity to date, there is no consensus about Training and Research Hospital, Background The relation between body mass index its exact definition yet. In one definition, obesity is Istanbul, Turkey 2 (BMI) and coronary artery disease (CAD) extension introduced as an increase in the body fat percentage Cardiology, Istanbul Teaching 4 5 and Research Hospital, Istanbul, remains controversial. A new score was developed to (BFP). Body mass index (BMI) has been used Turkey estimate body fat percentage (BFP) known as Relative frequently to determine definitions for obesity Fat Mass (RFM) Index. This study aimed to evaluate limits. However, it is thought that it is not a suffi- Correspondence to the value of RFM Index in predicting the severity cient formula to determine the body fat described Süleyman Çağan Efe, of the CAD, compared with other anthropometric in the definition of obesity. This situation is mani- Cardiology, Kartal Kosuyolu Training and Research Hospital, measurements. fested by its inability to distinguish people with Istanbul 34865, Turkey; Methods A total of 325 patients with chronic different fat ratios even though they have the same scaganefe@ gmail. com CAD were investigated. RFM, BFP, BMI and other BMI values.6 anthropometric characteristics of patients were Evidence from some studies in patients with Received 24 August 2020 measured before angiography. CAD severity was obesity with coronary artery disease (CAD) appears Revised 20 October 2020 determined by SYNergy between percutaneous to be contradictory. As a result of these studies, Accepted 29 October 2020 Published Online First 11 coronary intervention with TAXus and cardiac surgery the concept of ‘obesity paradox’ was proposed December 2020 trial (SYNTAX) Score. The association between due to the protective effect of obesity in spite of copyright. SYNTAX Score and variables was evaluated using the negative consequences.7–10 Moreover, the same linear regression models. In order to compare results as obesity paradox were confirmed for the the model performance, R- squared (R2), Akaike’s severity of CAD in some studies.11–13 Meanwhile, information criterion, Bayesian information criterion some studies showed that patients with increased and root mean square error were used. BMI had a greater prevalence, extent and severity Results Univariate linear regression outcome of CAD.14 15 These controversial results lead the variable, SYNTAX was used to determine whether researchers of current study to evaluate the utility there was any relationship between variables. of BMI in the diagnosis of obesity and its relevance Independent variables were included in the to cardiovascular events. multivariable linear logistic regression models. The Classification of obesity according to the BMI analysis showed that in model 1, RFM (β coefficient: has been questioned in some studies. For example, http://pmj.bmj.com/ 2.31 (0.90 to 3.71), p=0.001)), diabetes mellitus some authors believe that BMI is a parameter that (β coefficient: 3.72 (1.67 to 3.76), p=0.004)), should be used in the follow-up of patients, and haemoglobin (β coefficient: −2.12 (−3.70 to −0.53), not in the diagnosis of obesity.16 In addition, some p=0.03) and age (β coefficient: 1.83 (0.29 to 3.37), other parameters stated by international consensus p=0.02)) were statistically significant. The adjusted are more valuable in recommending and moni- R2 values in model 1 were higher than model 2 toring weight loss like waist circumference (WC).17 (BFP) and model 3 (BMI) (0.155, 0.137 and 0.130, Confusion caused by irrelevance between BMI and on September 27, 2021 by guest. Protected 2 respectively), and χ values of RFM were higher than obesity led the researchers to seek for new equa- BFP and BMI (10.5, 3.4 and 1.0, respectively). tions. As a result of the studies, a new proposal was Conclusion RFM Index is a more reliable and made to estimate the whole body fat (WBF) and to compatible marker of obesity in showing the severity of define obesity, which is known as relative fat mass CAD compared to BMI. (RFM). RFM Index is calculated using height, WC and gender regardless of weight. In some studies, it has been shown that the percentage of WBF is better predicted by RFM than BMI.18 © Author(s) (or their employer(s)) 2021. No INTRODUCTION The prevalence of CAD is associated with commercial re-use . See rights In recent years, dramatic increase in the prevalence the mortality and morbidity of patients. Hence, and permissions. Published of obesity has become a major health problem and different scoring systems were improved to deter- by BMJ. reached alarming dimensions.1 It is known that mine the prevalence and severity of CAD. SYNergy To cite: Efe SÇ, Karagoz A, being overweight and obese are associated with between percutaneous coronary intervention with Dogan C, et al. an increased risk of cardiovascular disease, that TAXus and cardiac surgery trial (SYNTAX) Score Postgrad Med J can cause mortality in the general population.2 3 has shown prognostic value for short- term and 2021;97:434–441. Although different approaches have attempted to long- term adverse cardiovascular events.19 20 434 Efe SÇ, et al. Postgrad Med J 2021;97:434–441. doi:10.1136/postgradmedj-2020-138926 Original research Postgrad Med J: first published as 10.1136/postgradmedj-2020-138926 on 11 December 2020. Downloaded from Figure 1 Consolidated Standards of Reporting Trials flow diagram of study. SYNTAX, SYNergy between percutaneous coronary intervention with TAXus and cardiac surgery trial. copyright. Accordingly, this study was conducted to evaluate the value Measurements of RFM Index in predicting the severity of the CAD, compared The body height was taken in the standing position close to with other anthropometric measurements. wall without shoes; weight was measured similarly without heavy dresses before CAG. WC was measured at the mid- point between the distal border of the ribs and the top of the iliac METHODS crest with subjects standing at the end of a normal expiration. This cross- sectional study was carried out with the participation BMI was calculated by dividing body weight in kilograms by the of 325 patients whose chronic CAD was determined by stress square of body length in metres (kg/m2). Waist height ratio was electrocardiography or myocardial perfusion scintigraphy. The calculated by dividing WC by height (cm).21 samples had been admitted to an outpatient cardiology clinic By using the US Navy method, the BFP formula was calculated http://pmj.bmj.com/ from June 2018 to October 2020. as follows:21 BFP (women)=495/(1.29579–0.35004 * log10 (Waist +Hip Neck)+0.22100 *log (Height)) – 450; Inclusion criteria 10 BFP (men)=495/(1.29579 - 0.35004 * log (Waist – There were two inclusion criteria: subjects aged between 18 and 10 Neck)+0.22100 * log (Height)) – 450; and 80 years and patients with chronic stable angina and undergoing 10 first time coronary angiography (CAG) for CAD detection. RFM Index was defined according to the following equation: 64 − (20 × height/waist) + (12 × sex), (sex=0 for men and on September 27, 2021 by guest. Protected 1 for women).18 Exclusion criteria Obesity was considered when BMI was equal or higher than 2 21 There were five exclusion criteria as follows: 30 kg/m , RFM higher than 33.9 in women or 22.8 in men. 1. Patients with unstable angina, acute ST segment-elevated In this study, we used SYNTAX 1 Score because it is based on myocardial infarction, non- ST segment- elevated myocardial anatomical stenosis irrespective of other parameters. Parameters infarction. which take part in SYNTAX Score 2 (diabetes mellitus (DM), 2. Patients with history of previous coronary artery bypass creatinine (CR)) could affect our results. Since using similar grafting or percutaneous coronary intervention (PCI). parameters like DM or CR as independent predictor in regres- 3. Those who had participated in weight-reducing programmes sion model affects the reliability of results, we preferred to use (including diets) or received related medications. SYNTAX Score 1. The SYNTAX I Score (www . SYNTAXscore. 4. Any systemic infection or any other serious comorbid con- com) was determined according to the coronary artery stenosis dition. and the anatomic complexity of the coronary lesions in patients 5. People unwilling to participate in the study. with multivessel disease. SYNTAX Score showed a signifi- The inclusion and exclusion criteria have been summarised in cant correlation with the morbidity and mortality outcomes of the Consolidated Standards of Reporting Trials flow diagram patients after PCI and was proposed as a tool to determine the (figure 1). option of revascularisation in patients with CAD. As SYNTAX Efe SÇ, et al. Postgrad Med J 2021;97:434–441. doi:10.1136/postgradmedj-2020-138926 435 Original research Postgrad Med J: first published as 10.1136/postgradmedj-2020-138926 on 11 December 2020. Downloaded from Scores increase, the prevalence of coronary disease refers to Table 1 Baseline characteristics of study population according to more complex and difficult interventional procedures, thus SYNergy between percutaneous coronary intervention with TAXus representing potentially worse prognosis.19 and cardiac surgery trial (SYNTAX) Scores The SYNTAX Score was determined by two independent cardiologists (SCE, BA) with 5 years of interventional experi- SYNTAX group 1 SYNTAX group 2 ence.