Body Mass Index and in-hospital mortality in patients from the Register of Acute Coronary Syndromes (RESCUE)
MIGUEL A. RODRÍGUEZ-RAMOS, DAYANI ARTEAGA-GUERRA,
LEONEL SIMANCAS-BROCHE, MICHEL GUILLERMO-SEGREDO.
Hospital General Docente Camilo Cienfuegos
Sancti-Spiritus, Cuba. E-mail
Recibido 20-SET-19 – ACEPTADO después de revisión el 27-OCTUBRE-2019.
There are no conflicts of interest to disclose.
In Acute Myocardial Infarction (AMI), some studies show a better prognosis of obese patients (Obesity paradox). Objective: to determine the association between Body Mass Index (BMI) and in-hospital mortality in a series of non-consecutive cases admitted with AMI. Method: Four groups were established: Underweight (BMI<20 kg/m2 BSA), Normal weight (NW) (BMI: +20-25 kg/m2 BSA), Overweight (BMI: +25-30 kg/m2 BSA), and Obese (BMI: +30 kg/m2 BSA). Analyses were made on ST Elevation Myocardial Infarction (STEMI) population and on overall AMI population. Clinical variables, complications, hemodynamic status at admission and discharge were studied. Results: With respect to patients with BMI <20 kg / m2 BSA, the association with mortality in patients with STEMI was: in NW 0.22 (CI: 0.05-0.86, p: 0.001), Overweight: 0.03 (CI: 0.02-0.23, p: 0.001), and Obese 0.52 (IC: 0.11-2.4, p: 0.41); in AMI: NW 0.3 (0.1-1.18, p: 0.007), Overweight 0.05 (0.01-0.32, p: 0.001), and Obese 0.62 (0.14-2.6, p: 0.52). Conclusions: There are elements to propose an “Obesity Paradox” in patients with BMI and BMI between 20-30 kg / m2bs.
Obesity and overweight present an increasing prevalence throughout the world . They are mentioned as mortality causes in some countries and their role in the pathophysiology of certain co-morbidities (diabetes, hypertension, hypercholesterolemia, etc.) cannot be questioned, although in some specific scenarios they could play a paradoxical role .
This is the case of Acute Myocardial Infarction (AMI), where some reports show a worse prognosis of patients with a body mass index (BMI) below 20 kg/m2 BSA, in comparison to those with overweight or mild obesity. These results may suggest that in the case of Acute Myocardial Infarction, BMI of more than 25 kg/m2 BSA (and even 30 kg/m2 BSA) could be associated to a better prognosis of the patient, even though this relation is still being discussed .
In a previous report from this center , this paradoxical relation was not confirmed. And, although not significant, data showed a reduction in in-hospital all-cause mortality risk between patients with BMI of more than 20 kg/m2 BSA in relation to those with BMI below this value. Further, most reports come from centers where coronary interventionism is the treatment of choice; therefore, a new analysis with data from patients treated with pharmacological reperfusion seems convenient.
The aim of this study was to determine the association between Body Mass Index (BMI) and in-hospital mortality in a series of non-consecutive cases (June 2014-February 2016 and May 2017-July 2018) admitted with AMI into the Hospital Provincial Camilo Cienfuegos.
All patients admitted between June 2014-February 2016 and May 2017-July 2018, in the Cardiology Ward of the Provincial Hospital of Sancti-Spiritus, Cuba, were included into the database of the Registry of Acute Coronary Syndromes – RESCUE (REgistro de Síndromes Coronarios agUdos). The data were obtained from clinical histories. A total of 830 patients were admitted and discharged with diagnosis of myocardial infarction or unstable angina. The final sample consisted of 825 patients, since 5 registries were dismissed as they had incomplete information in discharge.
Variables and events of interest
Basic and anthropometric demographic characteristics were collected for the patients studied. BMI was defined as weight in kilograms, divided by height in square meters. The following groups were defined: low weight (BMI <20 kg/m2 BSA); normal weight (BMI +20-25 kg/m2 BSA), overweight (BMI +25-30 kg/m2 BSA) and obese (BMI >39 kg/m2 BSA).
Also, clinical variables were analyzed, including classical cardiovascular risk factors, hemodynamic state in admission, as well as different scores from prognostic scores as TIMI and GRACE, electrocardiographic data, treatment administered during admission, complications and state at the time of discharge.
Continuous variables were expressed as mean and standard deviation, being compared by Student’s t test; while those expressed in percentages were compared using chi-square analysis.
There were 825 patients studied over the defined period, 476 with STEMI (57.7%). Overall mortality was 8.5% (70 patients), not verifying differences between cardiovascular risk factors in the diagnostic subgroups, nor subdivided by BMI. However, in patients with STEMI, taking as index group those with BMI <20 kg/m2 BSA, the probability of in-hospital decease was 0.22 (CI: 0.05-0.86, p=0.001) in patients with normal weight; 0.03 (CI: 0.02-0.23, p=0.001) in overweight patients; and 0.52 (CI: 0.11-2.4; p=0.41) in obese patients; in turn, repeating the same analysis in all the population with AMI, a probability of in-hospital death was obtained of 0.3 (0.1-1.18, p=0.007) in patients with normal weight; 0.06 (0.01-0.32, p=0.001) in overweight patients; and in obese patients, 0.62 (0.14-2.6, p=0.52) as shown in Table 1.
Comparison of mortality according to diagnosis and BMI.
However, when continuing with the logistic regression analysis, it was verified that there are other parameters with a stronger relationship than BMI with mortality in patients with AMI cardiogenic shock: 15.3 (0.1+22.8, p=0.001) and ejection fraction >35%: 12.1 (6.3-25.8, p=0.001) and systolic blood pressure >100 mmHg: 11.9 (3.8-17.8, p=0.001); data shown in Table 2; besides not being verified when this analysis was made in patients with NSTEMI.
Table 2 .
Logistic regression of parameters most related to a poor prognosis.
The proportion of patients with low BMI in the STEMI subgroup is greater in the sample. This group represents only 3% of the total population of several studies included in a meta-analysis. In it, only two studies showed frequencies close to ours, although not exceeding them .
The data from the RESCUE Registry do not confirm association between BMI and mortality in patients with STEMI; although there is greater mortality in the subgroup with low weight, that decreases as BMI increases, similarly to Ariza-Sole  and Niedziela . The first of these show that this difference could be due to the determination of the groups according to BMI; although in this study, this phenomenon seems to be limited by the weight of the size of the sample.
Meanwhile, in the subgroup with NSTEMI patients, the frequency of patients with low BMI coincides with that reported [8-10], and less BMI-dependent associations were identified in these patients. In the sample of the RESCUE Registry in patients with AMI/NSTEMI, there is barely an age difference between the studied groups; so age-dependent associations observed in the subgroup of STEMI patients are not identified in NSTEMI individuals.
Moreover, mortality in the subgroup of patients with low BMI was minimal; so no relation was sustainable with this result.
Therefore, a first conclusion is that if absolutely severe patients (shock, hypotensive, and severe systolic function depression) die, they will die regardless of their body mass index.
Reports with series of patients much greater than this sample [11-13], show that mortality according to BMI groups presents a J-shaped behavior, where the groups at the ends present either a null difference, or they are not statistically different in their behavior.
In a subsequent analysis, when subdividing patients with more than 20 kg/m2 BSA in 5 groups of BMI, and in Figure 1, the probability of death according to BMI is verified in a U-shaped line, where a greater chance of death presents in patients with BMI of less than 20 kg/m2 BSA, and the least mortality corresponds to patients that would qualify as overweight, with a risk of death even lower than in patients with a normal weight.
Figure 1. In-hospital mortality risk and body mass index.
This analysis was not reported previously, and the conclusion was that there were no elements to pose an “Obesity Paradox”. However, in the light of the current results, with a larger sample, mismatching results are found in regard to the first RESCUE analysis to be able to state that at least, in a single center, the obesity paradox is a sample-dependent phenomenon, that should be taken into account at the time of stratifying risk in the short term, in patients with Acute Coronary Syndrome.
Although there were no significant differences between extreme BMIs, there are elements to take into account to propose an “Obesity Paradox” in patients with AMI and BMI between 20-30 kg/m2 BSA. Mortality in patients with BMI greater than 30 kg/m2 BSA was less than that of patients with BMI lower than 20 kg/m2 BSA.
Tojek K, Wustrau B, Czerniak B, et al. Body mass index as a biomarker for the evaluation of the “Obesity Paradox” among inpatients. Clin Nutr 2019; 38 (1): 412-21.
Arrebola-Moreno AL, Marfil-Alvarez R, Catena A, et al.: Body mass index and myocardium at risk in patients with acute coronary syndrome. Rev Clin Esp (Barc). 2014; 214 (3):113-20.
Aljizeeri A, Coutinho T, Pen A, et al. Obesity and coronary artery calcification: ¿can it explain the obesity-paradox? Int J Cardiovasc Imaging 2015; 31 (5): 1063-70.
Rodriguez-Ramos MA: About acute coronary syndromes and obesity. Small lessons from RESCUE. Clinical Nutrition 2018 (37) 1777-78.
Niedziela J, Hodzik B, Niedziela N, et al. The obesity paradox in acute coronary syndrome: a meta-analysis. Eur J Epidemiol 2014; 29: 801-12.
Ariza-Sole A, Leon V, Formiga F, et al. Body mass index and prognosis in the elderly patients with acute coronary syndromes. Med Clin (Barc) 2015; 145 (1): 14-7.
Wells B, Gentry M, Ruiz-Arango A, et al. Relation between body mass index and clinical outcome in acute myocardial infarction. Am J Cardiol. 2006; 98 (4): 474-777.
Bucholz E, Rathore S, Reid K, et al. Body mass index and mortality in acute myocardial infarction patients Am J Med. 2012; 125 (8): 796-803.
Dooley J, Chang AM, Salhi R, Hollander JE. Relationship between body mass index and prognosis of patients presenting with potential acute coronary syndromes. Acad Emerg Med 2013; 20 (9): 904-10.
Goldberg RJ, Cui J, Olendzki B, et al. Excess body weight, clinical profile, management practices, and hospital prognosis in men and women after acute myocardial infarction. Am Heart J.2006; 151 (6): 1297-304.
Angera O, Albertsson P, Karason K, et al. Evidence for obesity paradox in patients with acute coronary syndromes: a report from the Swedish Coronary Angiography and Angioplasty Registry. Eur Heart J 2013; 34: 345-53.
Witassek F, Schwenkglenks M, Erne P, Radovanovic D. Impact of body mass index on mortality in Swiss hospital patients with ST-elevation myocardial infarction: does an obesity paradox exist? Swiss Med Wkly. 2014; 144:w13986.
Lavie CJ, Oktay AA, Milani RV. The obesity paradox and obesity severity in elderly STEMI patients. Eur Heart J Qual Care Clin Outcomes. 2017; 3 (3): 166-67.