P1652Limited correlation of calculated plasma volume status with invasive right heart pressures in patients with heart failure

Abstract

Abstract Background Estimated plasma volume (ePV) can be calculated from haematocrit and body weight, and has been shown to correlate with PV measured using 125Iodine labelled human serum albumin. Comparing a patient's ePV to ideal PV (iPV), an estimate of a patient's relative congestion, called PV status (PVS), is possible. Higher PVS is associated with increased mortality in patients with heart failure (HF), and has been proposed as a simple, cheap, and non-invasive way of assessing congestion. Purpose Whether PVS is associated with invasively measured markers of congestion is unknown. We calculated PVS in patients with HF who had right heart catheterisation (RHC), and assessed any correlation between PVS and invasive measures of congestion. Methods We calculated PVS in consecutive patients who had RHC performed as part of transplant assessment. iPV was calculated as: iPV = c × weight (kg) where c=39 in males and c=40 in females. ePV was calculated using subjects' haematocrit and weight as follows: ePV = (1 − haematocrit) × [a + (b × weight in kg)], where haematocrit is a fraction, a=1530 in males and a=864 in females, and b=41 in males and b=47.9 in females. PVS was calculated as: PVS = PVS = (ePV − iPV) /iPV × 100%. Correlation between PVS and invasive wedge pressure, mean right atrial (RA) pressure, and NTproBNP were made using Pearson correlation. Results PV indices and RHC data were available for 61 patients, 43 (71%) were male. Median age was 55 [IQR 48, 58] years. 20 (33%), 24 (39%), and 15 (25%) were NYHA association class II, III, and IV respectively. The median NTproBNP was 1390 [IQR 512, 3612] pg/ml and median ejection fraction was 29 [IQR 20, 35] %. The median PVS was −5.9% (IQR −12.5, −1.6]. Median wedge and mean-RA pressures were 14 [7, 21] and 4 [1, 8] mmHg, respectively. Correlation between mean RA pressure and PVS is shown in the figure. There was no correlation between PVS and mean RA pressure (r=0.12, p=0.34) or wedge pressure (r=0.01, p=0.92). There was a weak correlation between NTproBNP and PVS (r=0.31, p=0.01) Correlation mean RA pressure and PVS Conclusion PVS did not correlate with the invasive measures of congestion, mean RA and wedge pressure, but was weakly correlated with NTproBNP. Although there were limited number of patients in this study, we question the conclusion that PVS is a marker of congestion, and whether it can be used clinically for this purpose.