Impact of Body Mass Index on In-Hospital Outcomes after Percutaneous Coronary Intervention

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1 PERCUTANEOUS CORONARY INTERVENTION ORIGINAL RESEARCH Impact of Body Mass Index on In-Hospital Outcomes after Percutaneous Coronary Intervention Bahram Sohrabi MD 1, Afshin Habibzadeh MD 1, Samad Ghaffari MD 1, Mohsen Abbasnezhad MD 1, Parastoo Chaichi MD 2, Aysan Salamzadeh MD 1, Amir Kamalifar MD 3 Received: 10th December 2012, Reviewed: 11th Jan Accepted: 1st Feb Key words: Obesity; Percutaneous coronary intervention; Outcome DOI: /ejcm ABSTRACT: Objectives: The aim of current study is to evaluate relation between body mass index (BMI) and in-hospital outcome in patients undergoing percutaneous coronary intervention (PCI). Background: Relation between body mass indexes (BMI) with percutaneous coronary intervention (PCI) has shown in different studies. Recent studies suggested a paradox relation between different BMI values and outcome in certain patients. Methods: In this prospective study, 1134 patients (81.7% male, 18.3% female with mean age of 58.18±11.16 years) whom undergone PCI between January 2011 and December 2011 were chosen and their BMI and disease outcome was studied. Classification of BMI was: healthy weight (18.5 to 24.9 kg/m2), overweight (25 to 29.9 kg/m2), moderate obesity (30 to 34.9 kg/m2) and severe obesity (over 35 kg/m2). Baseline patient characteristics and in-hospital outcome were compared among BMI categories. Results: Major adverse cardiac events (MACE) were significantly higher in patients with overweight and moderate obesity than two other groups. There was no difference in mortality, reinfarction, revascularisation, stroke and bleeding events among the 4 groups. Being overweight is an independent factor associated to in-hospital MACE (odds ratio [OR] 0.37, 95% confidence interval [CI] 0.17 to 0.73, p=0.01) and mortality rate (OR 0.20, 95%CI 0.04 to 0.85, p=0.03). Conclusion: BMI overall is not correlated to in-hospital MACE and mortality; however, overweight patients are at reduced risk for MACE and mortality. 1. Dept. of Cardiology, Cardiovascular Research Center, Tabriz University of Medical Sciences, Tabriz, Iran. 2. Medical Philosophy and History Research Center, Tabriz University of Medical Sciences, Tabriz, Iran. 3. Students Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran. CORRESPONDENCE Afshin Habibzadeh Cardiovascular Research Center, Tabriz University (Medical Sciences), Golbad Ave., Tabriz, Iran. Zip code: Tel: Fax: Afshin.habibzadeh@gmail.com CONFLICT OF INTEREST None INTRODUCTION In the general population, obesity is associated with an increased risk of cardiovascular disease incidence and mortality. 1 3 Obesity is an important risk factor for the development of diabetes, hypertension, coronary artery disease and left ventricular dysfunction 4 and is considered an independent cardiovascular risk factor that is associated with poor clinical outcomes. 5 However, recent studies have suggested a paradoxical relationship between obesity and clinical outcomes in certain subsets of patients. Data from percutaneous coronary intervention (PCI) registries suggest that the very lean and the very obese have an increased risk of in-hospital complications and short-term mortality. 6 Some studies have shown a paradoxical protective effect of moderate obesity on outcome after PCI In these studies patients with high body mass index (BMI) showed lower risks of inhospital events, 8 and lower mortality rates after the procedure. 12 There is not a complete understanding of BMI effect on PCI outcome. In this study we aim to evaluate in-hospital outcome and mortality in patients with different BMI categories undergoing PCI. ACKNOWLEDGEMENTS This research was financially supported by Vice Chancellor for Research, Tabriz University of Medical Sciences, Iran. The authors are indebted to Cardiovascular Research Center, Tabriz University of Medical Sciences, Tabriz, Iran for its support. ISSN EUROPEAN JOURNAL OF CARDIOVASCULAR MEDICINE VOL II ISSUE III

2 BODY MASS INDEX AND IN-HOSPITAL OUTCOMES METHODS In this prospective study, we evaluated 1134 patients undergoing PCI between January 2011 and December 2011 in Madani Heart Hospital, Tabriz, Iran. The Ethics Committee of the Tabriz University of Medical Sciences approved the study, and all subjects gave informed consent. Information was prospectively recorded, including baseline demographics, clinical and procedural characteristics, and PCI and inhospital outcomes. Major adverse cardiac events and mortality in hospital were recorded. BMI was calculated at baseline by dividing the patient s measured weight (in kg) by the square of the height (in m). Classification of BMI was: healthy weight (18.5 to 24.9 kg/m2), overweight (25 to 29.9 kg/m2), moderate obesity (class I) (30 to 34.9 kg/m2) and severe obesity (class II) (over 35 kg/m2). We aimed to excluded patients whose BMI was recorded as <18 kg/m2 or >50 kg/m2; but interestingly, during study we had neither cases with BMI <18 kg/ m2 nor BMI >40 kg/m2. Diabetes mellitus was defined as a fasting glucose concentration of 7.0 mmol/l, a blood glucose concentration of 11.0 mmol/l on a 75-g, 2-h oral glucose tolerance test, or the use of anti-diabetic therapy. Hypertension was defined as a history of a systolic blood pressure of 140 mmhg, a diastolic pressure of 90 mmhg, or the use of antihypertensive therapy. Hyperlipidemia was defined as a fasting total cholesterol concentration of 220 mg/dl, a fasting triglyceride concentration of 150 mg/dl, or the use of anti-hyperlipidemic therapy. Coronary angiography data were obtained from database of the Catheterization Laboratory of Shahid Madani Hospital, including detailed angiographic findings of all patients at this institution. Procedural success was defined as angiographic success with no in-hospital major adverse cardiac event (MACE), defined as death, MI with new Q-waves on electrocardiogram (ECG) or urgent target vessel revascularisation (TVR) (including both repeat PCI and coronary artery bypass graft surgery [CABG]). New MI was defined as elevation of creatine kinase-mb to > 2 times the upper limit of normal with recurrent ischemic symptoms following PCI. Post-procedural ECGs were routinely assessed for new Q-waves; however, cardiac troponin, creatine kinase and creatine kinase-mb fraction were not routinely collected. DATA ANALYSIS Statistical analyses were performed using the Statistical Package for Social Sciences, version 16.0 (SPSS, Chicago, Illinois). Baseline patient clinical characteristics and angiographic data were compared among BMI categories. The chi-square test was used to test for differences in proportions of BMI categories for categorical variables. Analysis of variance was used to test for differences in means of BMI categories for quantitative variables. Logistic and multiple regression techniques were used to determine the effect of BMI on PCI outcome and mortality. A p value of 0.05 or less was considered significant. RESULTS Our study comprised of 1134 subjects; 207 (18.3%) female and 927 (81.7%) male with mean age of 58.18±11.16 (range 24-85) years. Their mean BMI was 27.43±4.05 (range ) kg/m2. The four groups comprised: Normal, 310 patients (27.3%); overweight, 526 patients (46.4%); moderate obesity, 246 patients (21.7%) and severe obesity, 52 patients (4.6%). The baseline characteristics of the patients according to BMI are shown in Table 1. There were some significant findings; by increase in the severity of obesity, patients were younger, mostly female and had higher prevalence of hypertension, familial history of coronary artery disease (CAD), previous PCI. Patients with overweight and moderate obesity had higher rate of hyperlipidemia, chronic renal failure, LVEF >40% and lower rate of previous MI and peripheral artery disease. Moderate obese patients significantly had the highest prevalence of CABG and lowest diabetes and severe obese patients do not have anemia. There were no significant differences in the proportions of patients with smoking. Angiographic findings of vascular involvement showed that multiple vessel disease existed in 98 (31.6%) of normal BMI patients, 214 (40.7%) of overweight patients, 145 (58.9%) of moderate obese patients and 13 (25%) of severe obese patients; the difference between four groups were significant (p<0.001). There was a significant difference in MACE events between 4 groups; as patients with overweight and moderate obesity had higher rate of MACE than normal and severe obese subjects (Table 2). The frequencies of overall mortality (neither cardiovascular nor non-cardiac), reinfarction, revascularisation, stroke and bleeding did not differ among the 4 groups (Table 2). Multivariate analysis showed that BMI itself had no impact on inhospital MACE (Table 3). Being overweight was significant indicator of in-hospital MACE; other independent factors were age, gender, previous PCI, anemia and LVEF. Using Multivariate analysis in order to find factors associated with in-hospital mortality, we found that being overweight along with previous MI and LVEF were independent predictors for in-hospital mortality (Table 3). DISCUSSION In this prospective, single center study among Iranian population, we evaluated body mass index effect on the outcome of patients undergoing percutaneous coronary intervention. We found that overweight and moderate obese patients had higher rate of MACE than other two groups. In contrast, we found no difference between groups regarding in-hospital mortality; however, regression analysis showed that overweight patients are at lower risk of in-hospital MACE and mortality than normal weight patients. However, in the study of Minutello et al. 11 patients with moderate or severe obesity have lower rates of death and MACE, with severe obesity patients having the lowest adjusted mortality rates. In this study, a consistent reduction in events has been found with increasing BMI until the BMI reaches 40 kg/m2. EUROPEAN JOURNAL OF CARDIOVASCULAR MEDICINE VOL II ISSUE III 155

3 HEALTHCARE BULLETIN PERCUTANEOUS CORONARY INTERVENTION Table 1: Characteristics of patients undergoing percutaneous coronary intervention by body mass index category Normal BMI Overweight Moderate obese Severe obese P value Age 60.11± ± ± ± * Gender (male) 86.5% 82.3% 76.4% 73.1% 0.007* Hypertension 28.7% 48.3% 61.8% 50% <0.001* Hyperlipidemia 25.8% 34.4% 44.7% 26.9% <0.001* Diabetes 25.5% 30.2% 18.7% 25% 0.009* Smoking 36.5% 31.6% 33.3% 34.6% 0.54 Familial history of CAD 16.5% 16.2% 18.7% 51.9% <0.001* Previous MI 61.9% 56.1% 59.8% 80.8% 0.004* Previous PCI 48.4% 54.6% 55.7% 90.4% <0.001* Previous CABG 5.8% 6.8% 16.7% 5.8% <0.001 Previous CRF 0 2.1% 9.4% Previous PAD 21% 16.9% 16.3% 32.7% 0.02* LVEF>40% 72.6% 76% 74.8% 67.3% Anemia 25.5% 12.5% 22.8% 0 <0.001 * p is significant. CAD: coronary artery disease; MI: myocardial infarction; PCI: percutaneous coronary intervention; CABG: coronary artery bypass graft; CRF: chronic renal failure; PAD: peripheral artery disease; LVEF: left ventricle ejection fraction. Table 2: In-hospital outcome of patients undergoing percutaneous coronary by body mass index category Normal BMI Overweight Moderate obese Severe obese P value MACE 31 (10%) 83 (15.8%) 47 (19.1%) 8 (15.4%) 0.02* Overall mortality 9 (2.9%) 27 (5.2%) 10 (4.1%) 2 (3.8%) 0.48 Cardiovascular death 5 (1.6%) 5 (1%) 1 (0.4%) Non-cardiac death 4 (1.3%) 22 (4.2%) 9 (3.7%) 2 (3.8%) 0.14 Reinfarction 7 (2.3%) 24 (4.6%) 13 (5.3%) 2 (3.8%) 0.27 Revascularization 19 (6.1%) 52 (9.9%) 31 (12.6%) 6 (11.5%) 0.06 Stroke 1 (0.3%) 5 (1%) 2 (0.8%) bleeding 9 (2.9%) 18 (3.4%) 9 (3.7%) 2 (3.8%) 0.95 * p is two-sided significant. MACE: Major adverse cardiac event; MI: Mocardial infarction 156 EUROPEAN JOURNAL OF CARDIOVASCULAR MEDICINE VOL II ISSUE III

4 BODY MASS INDEX AND IN-HOSPITAL OUTCOMES Table 3: Multivariate analysis of factors associated with in-hospital MACE and mortality. MACE Mortality Mortality OR (95%CI) p value OR (95%CI) p value Normal weight BMI 1 1 Overweight 0.37 ( ) 0.01* 0.20 ( ) 0.03* Moderate obese 0.28 ( ) ( ) 0.10 Severe obese 0.28 ( ) ( ) 0.10 Age ( ) 0.009* 1.02 ( ) 0.09 Gender 0.54 ( ) 0.03* 0.42 ( ) 0.08 Multivessel disease 0.89 ( ) ( ) 0.07 diabetes 0.70 ( ) ( ) 0.81 Hypertension ( ) ( ) 0.85 Hyperlipidemia 1.14 ( ) ( ) 0.58 Current smoking 1.44 ( ) ( ) 0.49 Previous MI 1.27 ( ) ( ) 0.04* Previous PCI 0.58 ( ) 0.02* 0.52 ( ) 0.11 Previous CABG 0.69 ( ) ( ) 0.65 LVEF 0.48 ( ) <0.001* 0.37 ( ) <0.001* Anemia 3.46 ( ) <0.001* 1.69 ( ) 0.20 * p is significant. BMI: Body mass index; MI: myocardial infarction; PCI: percutaneous coronary intervention; CABG: coronary artery bypass graft; LVEF: left ventricle ejection fraction. Observational studies suggest that obesity and overweight are associated with a neutral or beneficial effect on all-cause mortality post-coronary revascularisation. 13,14 A recently meta-analysis showed that compared to individuals without elevated BMI levels, both overweight and obese patients had lower in-hospital mortality. Also in patients with moderate and/or severe obesity, in-hospital mortality was reduced. 13 An explanation to these findings could be due to early diagnosis of their disease and its early management; as reported, obese patients are probably referred for angiography at an earlier stage of their disease, having a better short-term outcome The better outcomes for cardiovascular and total mortality seen in the overweight and mildly obese groups could be explained by the lack of discriminatory power of BMI to differentiate between body fat and lean mass. 18 Overweight and obese individuals are at greater risk for developing coronary artery disease, primarily as a consequence of obesityrelated conditions such as diabetes, hypertension, and dyslipidemia. 5 This could be another possible reason for better results in overweight and obese patients; as in such patients with numerous cardiovascular risk factors, the management of the disease is earlier and more severe. EUROPEAN JOURNAL OF CARDIOVASCULAR MEDICINE VOL II ISSUE III

5 HEALTHCARE BULLETIN PERCUTANEOUS CORONARY INTERVENTION In our study patients with higher BMI were more likely to be younger and female and had hypertension, peripheral artery disease, familial history of CAD, previous PCI and MI and low LVEF. Higher hyperlipidemia and chronic renal failure were higher in patients with overweight and moderate obesity. Niraj et al. 16 found that patients in higher obesity classes were more likely to be women and younger and had a higher prevalence of diabetes mellitus, systemic hypertension and dyslipidemia. Unlike previous studies, 16,19-21 we found no increased prevalence of diabetes according to BMI categories. In our study the frequencies of reinfarction, revascularisation, stroke and bleeding did not differ among BMI categories. In contrast, Gruberg et al. 7 observed that normal BMI patients had a higher incidence of major in-hospital complications, including cardiac death. But likely, they found no difference between groups in myocardial infarction and revascularisation rates. Our results could be confined to some limitations; in the study period we do not observe any cases with low body mass index (<18.5 kg/m2) and very severe obesity (BMI>40 kg/m2). There is various reports that patients at both BMI extremities are at greatest risk for post-pci MACE and mortality.6,9,14 In these studies usually a U-shaped relation has been exhibited between BMI and risk of PCI outcome and mortality. However, they mostly have reported better results in moderate and severe obese patients, and not overweight patients. CONCLUSION In conclusion, we observed that among patients undergoing PCI, overweight patients are at reduced risk for MACE and mortality. There was no relation between BMI categories and need for revascularisation, reinfarction, stroke or bleeding after PCI. REFERENCES Jonsson S, Hedblad B, Engstrom G, Nilsson P, Berglund G, Janzon L. 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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: EUROPEAN JOURNAL OF CARDIOVASCULAR MEDICINE VOL II ISSUE III