Physician-Predicted Risk for CAD vs Observed CAD in Obesity

The frequency of coronary artery disease (CAD) in patients who are obese was found to be lower than predicted by physicians, according to study results published in Heart.

The aim of the Prospective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE; Clinicaltrials.gov Identifier: NCT01174550) trial was to assess the association of obesity with risk factor burden, risk scores, and the obstructive CAD prevalence. Patients who were symptomatic but not diagnosed with CAD were randomly assigned to receive anatomic testing with electrocardiogram- (ECG) gated coronary computed tomographic angiography or a stress test. Stress testing was conducted using exercise ECG, stress echocardiography, or nuclear myocardial perfusion imaging.

Obstructive CAD was defined as ≥50% stenosis in the left main coronary artery, or ≥70% in any other major vessel. The updated Diamond-Forrester clinical prediction rule was used to assess the risk for obstructive CAD, and the Framingham Risk Score was used to predict cardiac events. Clinical outcomes included cardiovascular death, myocardial infarctions, and/or unstable angina hospitalization. Patients were categorized based on the World Health Organization guidelines for body mass index (BMI).

Of the 8889 patients included in this study, 35% were categorized as overweight, 28% were categorized as “obese 1”, 13% were categorized as “obese 2,” and 7% were categorized as “obese 3.” Overall, more obese patients were younger; women were more frequently in the underweight, normal weight, and obese 2 and 3 categories. Cardiovascular risk factors were found to increase with obesity.

The Diamond-Forrester predictive model indicated an inverted U-shaped relationship between obstructive CAD and BMI, with the lowest and the highest categories of BMI having the lowest number of high-risk patients. Based on this model, the normal weight group and the obese 2 and 3 groups had similar probabilities of developing CAD. The Framingham Risk Score and physician’s estimation of risk of developing CAD were both found to increase with BMI. The observed prevalence of obstructive CAD was 14.6% in individuals with a BMI <35 kg/m² (ie, underweight, normal weight, overweight, and obese 1 categories) and 12% in patients with a BMI ≥35 kg/m² (ie, obese 2 and 3 categories; P =.04).

Based on 2-way interactions between the Diamond-Forrester predictions and BMI, the adjusted odds ratio of obstructive CAD in patients with a BMI <35 kg/m² was 1.45, and 1.19 in patients with a BMI ≥35 kg/m². With each unit increase in BMI the risk for cardiovascular death, myocardial infarction, and unstable angina hospitalization was found to decrease (adjusted hazard ratio [aHR], 0.96; 95% CI, 0.94-0.99; P =.005). Patients with a BMI ≥40 kg/m² had a lower risk for cardiovascular death, myocardial infarction, and unstable angina hospitalization than patients with a BMI <40 kg/m² (aHR, 0.45; 95% CI, 0.22-0.92, P =.03).

Study limitations included the reliance on history vs direct measurement to assess risk factors, and the lack of direct measure of adipose tissue and of epicardial fat.

“These data highlight the challenges that providers face when evaluating and managing an increasingly obese patient population and support the need for more specific guidelines that incorporate anthropomorphic measures,” concluded the study authors.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Litwin SE, Coles A, Hill CL, et al. Discordances between predicted and actual risk in obese patients with suspected cardiac ischaemia [published online October 10, 2019]. Heart. doi:10.1136/heartjnl-2018-314503