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Obesity, Coronary Microvascular Dysfunction, and Risk
Study Questions:
What is the relationship among obesity, coronary microvascular dysfunction (CMD), and adverse outcomes?
Methods:
The investigators followed consecutive patients undergoing evaluation for coronary artery disease with cardiac stress positron emission tomography demonstrating normal perfusion (N = 827) for a median 5.6 years for events, including death and hospitalization for myocardial infarction or heart failure. Cox proportional hazards models were used to examine the association between covariates and events, sequentially adding demographic and clinical factors, followed by body mass index (BMI) and then coronary flow reserve (CFR).
Results:
An inverted independent J-shaped relationship was observed between BMI and CFR, such that in obese patients, CFR decreased linearly with increasing BMI (adjusted p < 0.0001). In adjusted analyses, CFR but not BMI remained independently associated with events (for a 1-U decrease in CFR, adjusted hazard ratio, 1.95; 95% confidence interval, 1.41-2.69; p < 0.001; for a 10-U increase in BMI, adjusted hazard ratio, 1.20; 95% confidence interval, 0.95-1.50; p = 0.125) and improved model discrimination (C-index 0.71-0.74). In obese patients, individuals with impaired CFR demonstrated a higher adjusted rate of events (5.7% vs. 2.6%; p = 0.002), even in those not currently meeting indications for bariatric surgery (6.4% vs. 2.6%; p = 0.04).
Conclusions:
The authors concluded that CMD was independently associated with elevated BMI and adverse outcomes, and was a better discriminator of risk than BMI and traditional risk factors.
Perspective:
This study reports an inverted J–shaped relationship between BMI and CFR in patients referred for cardiac stress testing, with higher BMI in obese patients associated with worsening coronary microvascular function, independently of clinical risk factors. Furthermore, in obese patients, only those with impaired CFR demonstrated a significantly increased risk of events. Additional prospective studies are needed to determine whether CMD may identify obese individuals most likely to benefit from bariatric surgery or other weight loss interventions.
Keywords: Bariatric Surgery, Body Mass Index, Coronary Artery Disease, Diagnostic Imaging, Heart Failure, Metabolic Syndrome, Myocardial Infarction, Myocardial Ischemia, Obesity, Positron-Emission Tomography, Primary Prevention, Risk Factors, Weight Loss
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