Abstract 16398: Prognostic Utility of the Hemoglobin/Hematocrit Equation for Estimating Plasma Volume Changes Over Time in Chronic Heart Failure
Background: Plasma volume (PV) expansion is a hallmark feature of worsening heart failure that is notoriously underestimated by clinical examination. Whilst radioisotope assays optimally quantify PV status, numerous validated equations also exist for its estimation. The hemoglobin(Hb) / hematocrit (Hct) formula is an index of the % change in PV (%ΔPV) over time that is predicated on the disproportionate alterations in Hb and Hct during PV fluctuations. We tested its prognostic utility in chronic heart failure (CHF) patients.
Methods: We analysed the relation between calculated PV changes over time and mortality in 273 outpatients with CHF (mean [±SD] age 70±13yr, 47% NYHA class > 2, LVEF 29±8%). %ΔPV was derived using the following equation: ([(Hb1/Hb2) x ((100-Hct2) / (100-Hct1))] -1) x 100% where 1= baseline and 2=end values.
Results: Over a median (±IQR) follow-up of 13±17 months, median %ΔPV was 4±24% with 42% and 58% of patients having PV contraction and expansion, respectively. Patients whose PV increased had poorer LVEFs (28% vs 30%, P=0.04) at baseline. Over this period, 53 (19%) patients died. %ΔPV predicted mortality (HR: 1.015, 95% CI: 1.007-1.024, P<0.001) in a graded fashion (Figure A) and did so independently of all covariates including baseline LVEF, and changes in sodium, urea, creatinine and albumin over time. A %ΔPV ≤ 10.2% optimally predicted survival (ROC AUC 0.63, P=0.003) and conferred a 60% reduced hazard for death (HR 0.40, 95% CI 0.24-0.70, P=0.001, Figure B).
Conclusions: Non-invasive estimation of plasma volume changes using the Hb/Hct equation appears prognostically useful in CHF patients and suggests that dehydration is better tolerated than volume excess and that targeting therapy to keep plasma volume increases below 10.2% might increment survival. Prospective studies assessing the utility of this simple, cheap and readily available index are needed.
- © 2011 by American Heart Association, Inc.