Background: Isolated systolic hypertension (ISH) is the most common form of high blood pressure (BP) in young adults and is associated with elevated stroke volume (SV), especially in males. However, not all young adults with high SV have high systolic BP (SBP). We sought to examine the haemodynamic factors that distinguish between levels of SBP in individuals with high SV.

Methods: Detailed haemodynamic measurements including brachial BP, SV and peripheral vascular resistance (PVR) were available in 2671 individuals (1303 males) aged 18–40 years. Data were stratified by gender and tertile of SV. In a subset of 89 individuals (51 males), haemodynamic measurements were repeated prior to, during and after low-level exercise on a cycle ergometer.

Results: In males and females with in the highest tertile of SV, a higher PVR was associated with increased SBP (P<0.001, males; P=0.003, females). In addition, multivariable regression analyses showed a significant, positive association between SBP and the interaction between SV and PVR (P<0.001), after adjustment for age and gender. A higher resting PVR was also associated with higher SBP during low-level exercise (r=0.3, P=0.05) and at 5 mins post-exercise (r=0.3, P=0.02) in males.

Conclusion: For a given level of SV, PVR distinguishes between different levels of SBP in young adults. PVR also appears to influence the SBP response to low-level exercise in males. The underlying mechanisms require further investigation.