The effect of sex on ventricular filling pressure during graded exercise in healthy young adults

There are several sex differences in cardiovascular morphology. Specifically, females have smaller cardiac chambers compared to males. Whether smaller left ventricular (LV) size contributes to higher filling pressures during dynamic exercise is unknown. We tested the hypothesis that smaller LV volumes and smaller stroke volume (SV) reserve in young females would be associated with greater LV filling pressures. <b>Methods.</b> Fourteen young males (n=7; 34±3yrs; 48.1±4.5 ml/kg/min) and females (n=7; 31±3yrs; V̇O_2peak 39.6±4.1 ml/kg/min) completed a maximal exercise test and an invasive exercise test with right heart catheterization. Hemodynamic response, including pulmonary capillary wedge pressure (PCWP), cardiac output and SV (direct Fick), were measured during upright rest and cycle exercise at a standard absolute heart rate of 100bpm, as well as 70 and 90% HR max. <b>Results.</b> Females had a greater PCWP during exercise (p=0.038), specifically when heart rate was matched at 100 bpm (males: 7±3, females: 10±2 mmHg, p=0.040) and at 90% HRmax (males: 8±3, females: 14±3 mmHg, p=0.006). Females also had a smaller SV reserve (46±19 %) than males (70±20 %, p=0.076). There was an inverse relationship between change in SV with exercise and PCWP (r²=0.22, p=0.003). The PCWP-cardiac output slope was significantly greater in females (0.9 ± 0.3 mmHg/L/min) than males (0.3 ± 0.2 mmHg/L/min, p=0.004). <b>Conclusion.</b> Females have higher PCWP for a given cardiac output and lower SV during exercise than males. These findings suggest smaller, absolute LV volumes are less distensible which may contribute to apparent sex differences in adaptations to chronic endurance training and performance.