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Venous Hematocrit: Caveats to Informing Blood Volume and Relative Risk in Chronic Heart Failure.
1Department of Cardiovascular Medicine Mayo Clinic Rochester MN USA.
Journal of the American Heart Association
|June 24, 2025
Summary
Venous hematocrit (vHct) does not reliably indicate absolute blood volume (BV) or red blood cell (RBC) and plasma volume profiles. Quantitative BV measurements are essential for accurate risk stratification and management in heart failure patients.
Area of Science:
- Cardiovascular Medicine
- Hematology
- Biomarker Analysis
Background:
- Venous hematocrit (vHct) is a common but imprecise measure of blood volume (BV) status and cardiovascular risk.
- Similar vHct values can represent diverse absolute BVs and red blood cell (RBC)/plasma volume distributions.
- This study investigates quantitative BV measures to improve vHct reliability in heart failure.
Purpose of the Study:
- To evaluate the utility of quantitative blood volume measurements in enhancing the diagnostic and prognostic value of venous hematocrit in heart failure.
- To explore the relationship between vHct, absolute blood volume, and the distribution of RBC mass and plasma volume.
Main Methods:
- Retrospective analysis of 395 heart failure patients stratified by clinically relevant vHct cut points (35% and 40%).
- Quantitative blood volume (BV) was determined using indicator-dilution methodology with iodinated-131 labeled albumin.
- Kaplan-Meier survival analyses were performed to compare patient outcomes.
Main Results:
- Absolute BV did not significantly differ between vHct subgroups, but RBC mass and plasma volume profiles showed significant variation.
- BV hypervolemia, primarily due to plasma expansion, was present in 58% of patients.
- Anemia and erythrocytosis profiles were observed, with 14% of patients exhibiting discordant RBC mass profiles relative to vHct cut points.
Conclusions:
- Venous hematocrit alone is insufficient to accurately discriminate absolute blood volumes or the complex profiles of RBC and plasma volumes.
- Quantitative BV measurements are crucial for refining the interpretation of vHct values.
- Accurate BV assessment enables reliable identification of volume status, appropriate risk assignment, and guided patient management in heart failure.
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