Study of Myocardial Perfusion in Obese Individuals without Known Ischemic Heart Disease

Abstract Background: Obesity is associated with an increased risk of type 2 diabetes mellitus (DM), ischemic heart disease (IHD) and cardiovascular mortality. Several studies have demonstrated the diagnostic and prognostic value of single photon computed tomography-myocardial perfusion scintigraphy (SPECT-MPI) in the evaluation of patients with suspected IHD, including in obese population. Data on clinical risk factors and their association with abnormal myocardial perfusion in obese patients are scarce in the Brazilian population. Objective: To determine the factors associated with abnormal myocardial perfusion in obese individuals without known IHD. Methods: We studied obese patients without known IHD who were referred for evaluation through SPECT-MPI between January 2011 and December 2016. Clinical variables and results of SPECT-MPI were obtained systematically. The distribution of continuous variables was assessed using the Shapiro-Wilk and Shapiro-Francia tests. We used the unpaired Student t test to compare the means of continuous variables with normal distribution and the Chi Square test for binomial variables analysis. A p value < 0.05 was considered statistically significant. The association of the clinical variables for the presence of factors associated with abnormal myocardial perfusion was determined by univariate and multivariate logistic regression analysis, and respective odds ratios (OR) and 95% confidence intervals (CI). Results: The study sample consisted of 5,526 obese patients. Mean body mass index (BMI) of our patients was 33.9 ± 3.7 kg/m2, 31% had DM, and myocardial perfusion abnormalities was observed in 23% of the total sample. The factors associated with abnormal myocardial perfusion on multivariate analysis were: age (OR: 1.02, 95% CI 1.01-1.03, p < 0.001), DM (OR: 1.57, 95% CI 1.31-1.88, p < 0.001), typical angina before the test (OR: 2.45, 95% CI: 1.82-3.31, p < 0.001), need for pharmacologic stress test (OR: 1.61, 95% CI: 1.26-2.07, p < 0.001), less physical effort evaluated in metabolic equivalents (METs) during the exercise treadmill test (OR: 0.89, 95% CI: 0.85-0.94, p < 0.001) and a lower post-stress left ventricular ejection fraction after stress (LVEF; OR: 0.989, 95% CI: 0.984-0.994, p < 0.001). Conclusion: The factors associated with abnormal myocardial perfusion in obese patients without known IHD were age, DM, presence of typical angina, ventricular dysfunction, and inability to undergo physical stress as clinical variables, in addition to functional capacity during physical stress.

摘要 背景：肥胖与2型糖尿病（type 2 diabetes mellitus, DM）、缺血性心脏病（ischemic heart disease, IHD）及心血管死亡风险升高相关。多项研究已证实单光子计算机断层扫描-心肌灌注显像（single photon computed tomography-myocardial perfusion scintigraphy, SPECT-MPI）在疑似IHD患者（包括肥胖人群）的评估中具有诊断及预后价值。目前巴西人群中关于肥胖患者临床危险因素及其与心肌灌注异常相关性的研究数据较为匮乏。
目的：明确无已知IHD的肥胖个体中心肌灌注异常的相关影响因素。
方法：本研究纳入2011年1月至2016年12月期间因评估需求接受SPECT-MPI检查且无已知IHD的肥胖患者。系统收集患者的临床变量及SPECT-MPI检测结果。采用Shapiro-Wilk检验与Shapiro-Francia检验评估连续变量的分布特征；对于符合正态分布的连续变量，采用成组t检验比较组间均值；二分类变量则采用卡方检验进行分析。以p值<0.05作为统计学显著性阈值。通过单因素及多因素logistic回归分析明确与心肌灌注异常相关的临床变量关联，并计算相应的比值比（odds ratios, OR）及95%置信区间（confidence intervals, CI）。
结果：本研究样本共纳入5526例肥胖患者。受试者的平均体质量指数（body mass index, BMI）为33.9±3.7 kg/m²，其中31%合并DM，整体样本中心肌灌注异常检出率为23%。多因素分析显示与心肌灌注异常相关的因素包括：年龄（OR=1.02，95%CI：1.01~1.03，p<0.001）、DM（OR=1.57，95%CI：1.31~1.88，p<0.001）、检查前存在典型心绞痛（OR=2.45，95%CI：1.82~3.31，p<0.001）、需行药物负荷试验（OR=1.61，95%CI：1.26~2.07，p<0.001）、运动负荷试验中达到的代谢当量（metabolic equivalents, METs）水平更低（OR=0.89，95%CI：0.85~0.94，p<0.001）以及负荷试验后左心室射血分数（left ventricular ejection fraction, LVEF）更低（OR=0.989，95%CI：0.984~0.994，p<0.001）。
结论：在无已知IHD的肥胖患者中，与心肌灌注异常相关的因素包括年龄、DM、典型心绞痛病史、心室功能异常、无法完成体力负荷试验，以及体力负荷过程中的功能储备能力。