Racial Differences in Left Ventricular Mass and Wave Reflection Intensity in Children

ORIGINAL RESEARCH published: 31 March 2020 doi: 10.3389/fped.2020.00132 Racial Differences in Left Ventricular Mass and Wave Reflection Intensity in Children Kevin S. Heffernan 1*, Wesley K. Lefferts 2 , Nader H. Atallah-Yunes 3 , Alaina C. Glasgow 1 and Brooks. B. Gump 4 1 Department of Exercise Science, Syracuse University, Syracuse, NY, United States, 2 Division of Academic Internal Medicine, Department of Medicine, University of Illinois-Chicago, Chicago, IL, United States, 3 Division of Pediatric Cardiology, SUNY Upstate Medical University, Syracuse, NY, United States, 4 Department of Public Health, Syracuse University, Syracuse, NY, United States Edited by: Jonathan Paul Mynard, Royal Children’s Hospital, Australia Reviewed by: Chloe May Park, University College London, United Kingdom Hopewell Nkosipendule Ntsinjana, University of the Witwatersrand, South Africa *Correspondence: Kevin S. Heffernan Specialty section: This article was submitted to Pediatric Cardiology, a section of the journal Frontiers in Pediatrics Received: 08 January 2020 Accepted: 10 March 2020 Published: 31 March 2020 Citation: Heffernan KS, Lefferts WK, Atallah-Yunes NH, Glasgow AC and Gump BB (2020) Racial Differences in Left Ventricular Mass and Wave Reflection Intensity in Children. Front. Pediatr. 8:132. doi: 10.3389/fped.2020.00132 Frontiers in Pediatrics | www.frontiersin.org The burden of heart failure is disproportionately higher in African Americans, with a higher prevalence seen at an early age. Examination of racial differences in left ventricular mass (LVM) in childhood may offer insight into risk for cardiac target organ damage (cTOD) in adulthood. Central hemodynamic load, a harbinger of cTOD in adults, is higher in African Americans. The purpose of this study was to examine racial differences in central hemodynamic load and LVM in African American and non-Hispanic white (NHW) children. Two hundred sixty-nine children participated in this study (age, 10 ± 1 years; n = 149 female, n = 154 African American). Carotid pulse wave velocity (PWV), forward wave intensity (W1) and reflected wave intensity (negative area, NA) was assessed from simultaneously acquired distension and flow velocity waveforms using wave intensity analysis (WIA). Wave reflection magnitude was calculated as NA/W1. LVM was assessed using standard 2D echocardiography and indexed to height as LVM/[height (2.16) + 0.09]. A cutoff of 45 g/m (2.16) was used to define left ventricular hypertrophy (LVH). LVM was higher in African American vs. NHW children (39.2 ± 8.0 vs. 37.2 ± 6.7 g/m (2.16), adjusted for age, sex, carotid systolic pressure and socioeconomic status; p < 0.05). The proportion of LVH was higher in African American vs. NHW children (25 vs. 12 %, p < 0.05). African American and NHW children did not differ in carotid PWV (3.5 ± 4.9 vs. 3.3 ± 1.3 m/s; p > 0.05). NA/W1 was higher in African American vs. NHW children (8.5 ± 5.3 vs. 6.7 ± 2.9; p < 0.05). Adjusting for NA/W1 attenuated racial differences in LVM (38.8 ± 8.0 vs. 37.6 ± 7.0 g/m (2.16); p = 0.19). In conclusion, racial differences in central hemodynamic load and cTOD are present in childhood. African American children have greater wave intensity from reflected waves and higher LVMI compared to NHW children. WIA offers novel insight into early life origins of racial differences in central hemodynamic load and cTOD. Keywords: children, vascular stiffness, wave intensity analysis, wave reflection, left ventricular mass INTRODUCTION Although incidence and mortality from cardiovascular disease (CVD) is declining, there are still prominent disparities in CVD burden based on race (1). Compared to non-Hispanic whites (NHWs), African Americans have 33% higher death rates from CVD (1). Prevalence of hypertension in African Americans (∼42–44%) is among the highest in the world and greater 1 March 2020 | Volume 8 | Article 132 Heffernan et al. Racial Differences in Wave Intensity area (NA) (26, 27). A second forward traveling wave is generated at the end of systole, mirroring the decompression (deceleration) of the wave produced by/contributing to the closing of the aortic value during diastole (26). This expansion wave, denoted as W2, is related to cardiac untwist and suction and thus LV relaxation kinetics. Measures obtained from WIA have been shown to correlate with LV structure and function (28, 29). WIA may thus offer a novel window into racial differences in cTOD risk in childhood. The purpose of this study was to use WIA to assess racial differences in ventricular-vascular coupling and central hemodynamic load in children to gain insight into early life origins of cTOD. We hypothesized that African American children would have higher LVM, carotid artery stiffness and pressure from wave reflections. than that seen in NHWs (1, 2). As such hypertensive cardiac target organ damage (cTOD) is not only common but epidemic in African Americans (3, 4). African Americans have a 50% greater incidence of heart failure compared to their NHW counterparts (5). cTOD occurs earlier in life in African Americans than in NHWs (6, 7) and is associated with premature CVD events (8). The CARDIA study reported that 26/27 deaths from heart failure occurred in young African Americans (<50 years of age) with only 1 NHW death (9). Racial differences in hypertension and hypertensive cTOD may have its origins in childhood as higher blood pressure (BP) in African American children track into young adulthood (10) and BP is a significant correlate of cTOD in African American children (11, 12). There are also racial differences in age-related increases in left ventricular mass (LVM) (13), a measure of cTOD, with African Americans having larger LVM in late childhood through young adulthood (14). Predictors of increases in LVM and development of LV hypertrophy from young adulthood to middle-age include larger LVM assessed in young adulthood, higher systolic BP and Black/African American race (15–17). African Americans are more susceptible than NHW to BP-mediated cTOD suggesting that racial differences in hemodynamic load may have more profound effects on cTOD in African Americans (18, 19). Hemodynamic load is largely determined by central (large artery) stiffness and pressure from wave reflections (20, 21). Increases in arterial stiffness precede the development of hypertension in young adults (22) and increases in pressure from wave reflections have a profound and detrimental impact on the LV (20, 21). Increases in large artery stiffness and pressure from wave reflections alter ventricular-vascular coupling, contributing to increased afterload, myocardial strain, LVM, and ultimately LV hypertrophy (23). Racial differences in hemodynamic load may also have its origins in childhood as African American children have increased arterial stiffness compared to NHW children (24) and central BP is associated with LVM in young African American adolescents (25). Wave intensity analy (...truncated)