Detection of biventricular volume increase in overweight and obese by using a novel index of the ideal human - a single center non-contrast-enhanced cardiac CT study

Abstract The bi-ventricular volume (BVV) can be measured from non-contrast-enhanced CT images in patients referred for coronary artery calcium (CAC) scoring. Such determined BVV has been found to correlate with left ventricular mass and to predict increased risk of all-cause and CV mortality in patients with type 2 diabetes mellitus. Currently, no data are available that quantifying the effect of body size on BVV using NCE-CT. We used a new indexing parameter that consisted of two parts: height and the difference between numerical values of height and body surface area (BSA). In the "ideal human", the difference is zero. Any deviation from this value determines the share of body mass regardless of height. Aim We hypothesize that a novel indexation way allows for better discrimination of the increased bi-ventricular volume in overweight and obese patients. Method We retrospectively analyzed the CT data from 2466 patients with CAC scoring over the last 15 years. Among them 1606 women and 860 men with an average age of 64 ± 11 years (range 21-93). The fatless bi-ventricular volume was measured manually using commercial software on a dedicated workstation (Vitrea2). Values of the raw (measured, ml) BVV and BVV normalized for height, BSA, and the novel parameter i.e. [h+ (h-BSA)], were compared in patients taking into account body mass index (BMI) categories of normal weight (25% of patients), overweight (40%) and obese (35%). Results Overall, the measured BVV [ml] was significantly greater in males (414±97) than in females (297±66) (p<0.001). BVV decreased non-linearly from before 40ties to mid-60ties, and then remained nearly stable. In normal-weight males, the measured BVV (370±80ml) was greater than in normal-weight females (279±61ml) (p<0.001). In overweight males, the BVV was 411±89ml; in overweight females, the BVV reached 290±59ml (p<0.001). These differences were non-significantly different from the sample of patients with normal BMI. In obese patients, mean values significantly differed between males and females (442±106 vs 321±71 ml, p<0.001). As the absolute value of the BVV should be interpreted in the context of body habitus, normalization for height, BSA, and the novel index were used. The results of these examinations are given in the figure. Conclusions Commonly used methods of indexing the volumetric parameters of the ventricles, as well as the novel indexing approach showed similar results in patients with normal body weight. The proposed indexation allowed for discriminating the increase in BVV that is easy to overlook in overweight. The use of body surface area for volumetric normalization is misleading as it provides similar values in normal, overweight, and obese patients, and should therefore be avoided. We should consider whether ventricular size standards based on a study population under 50 years of age create reliable conditions for detecting ventricular enlargement at an older age.