Cardiac stroke volume in females and its correlation to blood volume and cardiac dimensions

Janis Schierbauer; Sandra Ficher; Paul Zimmermann; Nadine B Wachsmuth; Walter F J Schmidt

doi:10.3389/fphys.2022.895805

Cardiac stroke volume in females and its correlation to blood volume and cardiac dimensions

Front Physiol. 2022 Sep 27:13:895805. doi: 10.3389/fphys.2022.895805. eCollection 2022.

Authors

Janis Schierbauer^{1

2}, Sandra Ficher², Paul Zimmermann^{1

3}, Nadine B Wachsmuth^{1

2}, Walter F J Schmidt²

Affiliations

¹ Division of Exercise Physiology and Metabolism, University of Bayreuth, Bayreuth, Germany.
² Department of Sports Medicine/Sports Physiology, University of Bayreuth, Bayreuth, Germany.
³ Department of Cardiology, Klinikum Bamberg, Bamberg, Germany.

Abstract

We aimed to continuously determine the stroke volume (SV) and blood volume (BV) during incremental exercise to evaluate the individual SV course and to correlate both variables across different exercise intensities. Twenty-six females with heterogeneous endurance capacities performed an incremental cycle ergometer test to continuously determine the oxygen uptake (V̇O₂), cardiac output (Q̇) and changes in BV. Q̇ was determined by impedance cardiography and resting cardiac dimensions by 2D echocardiography. Hemoglobin mass and BV were determined using a carbon monoxide-rebreathing method. V̇O_2max ranged from 32 to 62 mL·kg^-1·min^-1. Q̇_max and SV_max ranged from 16.4 to 31.6 L·min^-1 and 90-170 mL, respectively. The SV significantly increased from rest to 40% and from 40% to 80% V̇O_2max. Changes in SV from rest to 40% V̇O_2max were negatively (r = -0.40, p = 0.05), between 40% and 80% positively correlated with BV (r = 0.45, p < 0.05). At each exercise intensity, the SV was significantly correlated with the BV and the cardiac dimensions, i.e., left ventricular muscle mass (LVMM) and end-diastolic diameter (LVEDD). The BV decreased by 280 ± 115 mL (5.7%, p = 0.001) until maximum exercise. We found no correlation between the changes in BV and the changes in SV between each exercise intensity. The hemoglobin concentration [Hb] increased by 0.8 ± 0.3 g·dL^-1, the capillary oxygen saturation (ScO₂) decreased by 4.0% (p < 0.001). As a result, the calculated arterial oxygen content significantly increased (18.5 ± 1.0 vs. 18.9 ± 1.0 mL·dL^-1, p = 0.001). A 1 L higher BV at V̇O_2max was associated with a higher SV_max of 16.2 mL (r = 0.63, p < 0.001) and Q̇_max of 2.5 L·min^-1 (r = 0.56, p < 0.01). In conclusion, the SV strongly correlates with the cardiac dimensions, which might be the result of adaptations to an increased volume load. The positive effect of a high BV on SV is particularly noticeable at high and severe intensity exercise. The theoretically expected reduction in V̇O_2max due to lower SV as a consequence of reduced BV is apparently compensated by the increased arterial oxygen content due to a higher [Hb].

Keywords: carbon monoxide-rebreathing; cardiac output; echocardiogaphy; hemoconcentration; hemodynamics; impedance cardiography; oxygen uptake; plasma volume shifts.