Cardiac-hematological capacity in healthy Hans Chinese : effects of blood volume and body composition

Abstract

According to blood withdrawal studies, blood volume (BV) is the main determinant of cardiac and aerobic capacities, representing strong mortality predictors. Yet, whether blood volume expansion (BVexp), in isolation, improves cardio-respiratory capacities remains uncertain. Placebo (PBO) and albumin intravenous infusion leading to BVexp (+10 %) were delivered using a blinded and cross-over study design in healthy women and men (n=40) matched by age (26±4 vs. 27±5 yr) and physical activity. Cardiac structure, central/peripheral hemodynamics and O2 consumption were assessed up to peak incremental exercise via transthoracic echocardiography and pulmonary gas analyses. BVexp elicited nearly proportional increments (+8 to +10 %) in cardiac volumes in women and men. In both sexes, BVexp markedly reduced systemic peak O2 extraction (-12 to -14 %) in parallel to decrements in systemic vascular resistance and aerobic capacity (-8 to -10 %). The isolated expansion of BV up to the hypervolemic level typically elicited by endurance training leads to pronounced alterations in peripheral circulatory function and reduced aerobic capacity in healthy women and men.

Whether long-term increased water intake alone, or in combination with co-adjuvant non- exercise interventions aimed to expand BV, improve the human cardiovascular phenotype and cardiorespiratory fitness remains unexplored. Healthy adults (n=35, 42±18 yr, 51 % ♀) matched by sex, age, body composition, physical activity and cardiorespiratory fitness were randomly allocated to increased (+40 %) fluid (water) intake (IFI) or IFI + head up sleep (IFI+HUS) for 3 months. Long-term increased water intake largely expands the resting cardiac volume and output while reducing arterial elastance and cardiac afterload, without altering intravascular volumes, cardiac or aerobic capacities. With the addition of HUS, relaxation properties of the resting LV are further improved.

Lean body mass (LBM) and the functional capacity of the cardiovascular system constitute a female-specific relationship in European-American individuals. Whether such a recent finding can be extrapolated to the world’s largest ethnic group, i.e., Hans Chinese (HC), a population characterized by low LBM, is unknown. Healthy HC adults (n=144, 50 % ♀) closely matched by sex, age and physical activity were included. Total and regional (leg, arm, trunk) LBM and body composition were measured via dual-energy x-ray absorptiometry. In both sexes, total LBM positively associated with left ventricular (LV) mass and peak volumes (r≥0.33, P≤0.005) and negatively with LV end-systolic and central arterial stiffness (r≥-0.34, P≤0.004). Total LBM strongly associated with VO2peak (r≥0.60, P<0.001) and peak cardiac output (r≥0.40, P<0.001) in women and men. In conclusion, LBM independently determines internal cardiac dimensions, ventricular mass, stiffness and the capacity to deliver and consume O2 in HC adults irrespective of sex.