Background: Body mass index (BMI) is the most widely used measure to diagnose obesity. However, the accuracy of BMI in detecting excess body adiposity in the adult general population is largely unknown. Methods: A cross-sectional design of 13 601 subjects (age 20-79.9 years; 49% men) from the Third National Health and Nutrition Examination Survey. Bioelectrical impedance analysis was used to estimate body fat percent (BF%). We assessed the diagnostic performance of BMI using the World Health Organization reference standard for obesity of BF%425% in men and435% in women. We tested the correlation between BMI and both BF% and lean mass by sex and age groups adjusted for race. Results: BMI-defined obesity (X30 kg m À2 ) was present in 19.1% of men and 24.7% of women, while BF%-defined obesity was present in 43.9% of men and 52.3% of women. A BMIX30 had a high specificity (men ¼ 95%, 95% confidence interval (CI), 94-96 and women ¼ 99%, 95% CI, 98-100), but a poor sensitivity (men ¼ 36%, 95% CI, 35-37 and women ¼ 49%, 95% CI, 48-50) to detect BF%-defined obesity. The diagnostic performance of BMI diminished as age increased. In men, BMI had a better correlation with lean mass than with BF%, while in women BMI correlated better with BF% than with lean mass. However, in the intermediate range of BMI (25-29.9 kg m À2 ), BMI failed to discriminate between BF% and lean mass in both sexes. Conclusions: The accuracy of BMI in diagnosing obesity is limited, particularly for individuals in the intermediate BMI ranges, in men and in the elderly. A BMI cutoff ofX30 kg m À2 has good specificity but misses more than half of people with excess fat. These results may help to explain the unexpected better survival in overweight/mild obese patients.
Normal weight obesity, defined as the combination of normal BMI and high BF content, is associated with a high prevalence of cardiometabolic dysregulation, metabolic syndrome, and CV risk factors. In women, NWO is independently associated with increased risk for CV mortality.
Tissue Doppler imaging (TDI) and TDI-derived strain imaging are robust physiologic tools used for the noninvasive assessment of regional myocardial function. Due to high temporal and spatial resolution, regional function can be assessed for each phase of the cardiac cycle and within the transmural layers of the myocardial wall. Newer techniques that measure myocardial motion by speckle tracking in grayscale images have overcome the angle dependence of TDI strain, allowing for measurement of 2-dimensional strain and cardiac rotation. TDI, TDI strain, and speckle tracking may provide unique information that deciphers the deformation sequence of complexly oriented myofibers in the left ventricular wall. The data are, however, limited. This review examines the structure and function of the left ventricle relative to the potential clinical application of TDI and speckle tracking in assessing the global mechanical sequence of the left ventricle in vivo.The spiral arrangement of muscle fibers in the heart is reminiscent of spiral and vortex patterns in nature, ranging from small organelles and whirlpools to hurricanes and rotational patterns of the galaxies (1-5). Vortex patterns link two fundamental forms of motion that work in close balance: an inner, rapidly descending swirl and an outer, less rapid, ascending rotation (4) ( Fig. 1 A-C). These counterdirectional movements of a vortex produce suction and expulsion forces that have been exploited for designing energy efficient propellers and turbines (6). Likewise, experimental and mathematical modeling of the clockwise and counterclockwise spiral loops of myofibers in the left ventricle (LV) has shown that counterdirectional geometry provides an efficient distribution of regional stresses and strains (7). Conversely, altered ventricular geometry resulting from cardiac remodeling, regional myocardial dysfunction, or asynchronous conduction distort the efficiency of the loading and expulsion dynamics (8,9). In this review, we associate the LV myofiber architecture to the spatiotemporal sequence of regional deformations occurring during normal cardiac contraction and relaxation. We further elucidate experimental observations, which explore the application of tissue Doppler imaging (TDI) and 2-dimensional ultrasound speckle tracking for delineation of the synchronous mechanical shortening and lengthening sequences of the human LV.Address reprint requests to Marek Belohlavek, Division of Cardiovascular Diseases, Mayo Clinic, 13400 East Shea Boulevard Scottsdale, AZ 85259, E-mail address for author named in reprint line: Belohlavek.email@example.com Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect th...
Apex-to-base delay in mechanical shortening of LV parallels the apex-to-base direction of the electric activation sequence. Basal subendocardial and apical subepicardial regions deform through a characteristic phase of postsystolic shortening. Short-lived apex-to-base and subendocardial-to-subepicardial relaxation gradients at the onset of diastole may have a physiologic significance in facilitating active restoration of the LV cavity in diastole.
In patients with CAD, BMI does not discriminate between BF% and lean mass, and a BMI < 30 kg/m(2) is a poor index to diagnose obesity. These findings may explain the controversial findings that link mild elevations of BMI to better survival and fewer cardiovascular events in patients with CAD. Body composition techniques to accurately diagnose obesity in patients with CAD might be necessary.
scite is a Brooklyn-based startup that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.