Sex Differences in the Influence of Heart Rate, End-Diastolic Volume, and Body Surface Area on Cardiac Output: A Magnetic Resonance Imaging Study

Background This study investigates sex differences in the determinants of cardiac output (CO) using cardiac magnetic resonance imaging (CMR). Methods This is a single centre, cross-sectional study of 268 adults (43% female, 59 ± 10 years) from the Courtois Cardiovascular Signature Program. Participants were stratified into below and above mean CO groups using predefined sex-specific thresholds (6.0 L/min in males, 4.9 L/min in females). Multivariable regression and interaction analyses assessed associations between CO and heart rate (HR), end-diastolic volume (EDV), and body surface area (BSA) by sex. Results Among males with below mean CO, EDV and HR were independently associated with CO (EDV: β = 0.42, CI [0.241, 0.592], p < 0.001; HR: β = 0.21, CI [0.037, 0.385], p=0.018). In below mean CO females, only HR was independently associated with CO (β = 0.26, CI [0.023, 0.490], p=0.032). In the above mean CO group, only HR was independently associated with CO in males, while in females, both HR and EDV were associated; BSA was not associated in either sex. Interaction analysis revealed a stronger EDV-CO relationship in below vs above mean CO states among males (p = 0.010), whereas no significant interactions were observed in females. Conclusion These findings reveal sex-specific patterns of association in the determinants of CO, with CO more strongly associated with EDV in males and HR in females in low output states.