Coronary circulatory function with increasing obesity: A complex U-turn

The aim of this investigation was to explore and characterize alterations in coronary circulatory function in function of increasing body weight with medically controlled cardiovascular risk factors and, thus, "metabolically" unhealthy obesity.

We prospectively enrolled 106 patients with suspected CAD but with normal stress-rest myocardial perfusion on ¹³ N-ammonia PET/CT and with medically controlled or no cardiovascular risk factors. ¹³ N-ammonia PET/CT concurrently determined myocardial blood flow (MBF) during pharmacologically induced hyperaemia and at rest. Based on body mass index (BMI), patients were grouped into normal weight (BMI: 20.0-24.9 kg/m² , n = 22), overweight (BMI: 25.0-29.9 kg/m² , n = 27), obese (BMI: 30.0-39.9 kg/m² , n = 31), and morbidly obese (BMI ≥ 40kg/m² , n = 26).

Resting MBF was comparable among groups (1.09 ± 0.18 vs. 1.00 ± 0.15 vs. 0.96 ± 0.18 vs.. 1.06 ± 0.31 ml/g/min; p = .279 by ANOVA). Compared to normal weight individuals, the hyperaemic MBF progressively decreased in in overweight and obese groups, respectively (2.54 ± 0.48 vs. 2.02 ± 0.27 and 1.75 ± 0.39 ml/g/min; p < .0001), while it increased again in the group of morbidly obese individuals comparable to normal weight (2.44 ± 0.41 vs. 2.54 ± 0.48 ml/g/min, p = .192). The BMI of the study population correlated with the hyperaemic MBF in a quadratic or U-turn fashion (r = .34, SEE = 0.46; p ≤ .002).

The U-turn of hyperaemic MBF from obesity to morbid obesity is likely to reflect contrasting effects of abdominal versus subcutaneous adipose tissue on coronary circulatory function indicative of two different disease entities, but needing further investigations.