Abstract Body (Do not enter title and authors here): Background: In heart failure with preserved ejection fraction (HFpEF) expanded blood volume (BV) can result in significant hemodynamic stress that contributes to disease pathogenesis. Due to the lack of routine access to methods of BV measurement, clinicians typically rely on BV prediction equations. However, current prediction equations do not accurately or precisely estimate BV, or its components, in HFpEF. The aim of our analysis was to directly measure blood volume in adults with HFpEF and compare newly developed BV prediction equations (Oberholzer et al., 2023) to previously validated equations (Nadler and Pearson).
Methods: In 52 adults with HFpEF (65% female; age: 70±7 years; BMI: 38±7[GM1] kg/m²) we assessed total hemoglobin mass via carbon monoxide rebreathing, enabling calculation of BV. We estimated BV with the Oberholzer simple (age, sex, height and body mass) and clinical (age, height, and lean mass) equations, as well as Nadler and Pearson equations. Data were compared via either paired or independent samples t-tests or a one-way ANOVA with values presented as mean [95% CI] or mean ± standard deviation.
Results: Unlike the Oberholzer simple (-226 [-507 – 55] ml, P=0.113) equation, the Oberholzer clinical equation significantly underestimated measured BV (-513 [-807 – 219] ml, P=0.001); both of which were imprecise with large typical error values (TE; Simple: 11%; Clinical: 11%). Compared to the Oberholzer equations, the mean estimated-measured difference was greater with the Nadler (P<0.001; TE=12%) and Pearson (P<0.001; TE=11%) equations (Figure 1A). We observed greater accuracy and precision of all prediction equations for females compared to males (Figure 1B-C): Oberholzer simple (P=0.070); Oberholzer clinical (P=0.047); Nadler (P<0.001); Pearson (P<0.043).
Conclusions: The Oberholzer simple equation yielded the most accurate and precise prediction of BV in adults with HFpEF, with greater accuracy and precision in females. However, all prediction equations remain imprecise with substantial error up to 11% and should therefore be used with caution. As such, there needs to be more widespread measurement of BV to refine prediction equations utilized in clinical settings.