Are non-invasive estimations of plasma volume an accurate measure of congestion in patients with chronic heart failure?

Abstract

Aim We report associations between different formulae for estimating plasma volume status (PVS) and clinical and ultrasound markers of congestion in patients with chronic heart failure (CHF) enrolled in the Hull Lifelab registry. Methods and results Cohort 1 comprised patients with data on signs and symptoms at initial evaluation (n = 3505). Cohort 2 included patients with ultrasound assessment of congestion (lung B-line count, inferior vena cava (IVC) diameter, jugular vein distensibility (JVD) ratio) (N = 341). Two formulae for PVS were used: (a) Hakim (HPVS) and (b) Duarte (DPVS). Results were compared with clinical and ultrasound markers of congestion. Outcomes assessed were mortality and the composite of heart failure (HF) hospitalisation and all-cause mortality. In cohort 1, HPVS was associated with mortality (hazard ratio (HR) per unitary increase = 1.02 (1.01 – 1.03); P<0.001). In cohort 2, HPVS was associated with B-line count (HR) = 1.05 (95% confidence interval (CI) 1.01 – 1.08); P = 0.02) and DPVS with the composite outcome (HR = 1.26 (1.01 – 1.58); P = 0.04). HPVS and DPVS were strongly related to haemoglobin concentration and HPVS to weight. After multivariable analysis, there were no strong or consistent associations between PVS and measures of congestion, severity of symptoms, or outcome. By contrast, log[NTproBNP] was strongly associated with all three. Conclusions Amongst patients with CHF, HPVS and DPVS are not strongly or consistently associated with clinical or ultrasound evidence of congestion, nor clinical outcomes after multivariable adjustment. They appear only to be surrogates of the variables from which they are calculated with no intrinsic clinical utility.

Critical Analysis of the Effects of SGLT2 Inhibitors on Renal Tubular Sodium, Water and Chloride Homeostasis and Their Role in Influencing Heart Failure Outcomes

“…Even if there were no erythropoiesis, estimation of plasma volume by the Strauss formula can be distorted by shifts in the distribution of red blood cells from intravascular pools, as is commonly seen during the clinical course of patients with acutely decompensated heart failure. [86][87][88]93 Even if measured accurately, decreases in plasma volume do not reliably reflect intravascular or total body decongestion. Diuretics may have little effect on or even increase plasma volume in heart failure, if they mobilize fluid from the interstitial space.…”

“… 85 The Kaplan formula is based on hematocrit and body weight, whereas the Strauss formula focuses on the ratios of hemoglobin and hematocrit. These formulas yield poor estimates of directly measured values 86 —often deviating by >1 liter 87 —and provide unreliable metrics of clinical congestion 88 or decongestion. 89 Furthermore, the Strauss formula assumes that red blood cell mass in the central circulation does not change between paired assessments.…”

“…Even if there were no erythropoiesis, estimation of plasma volume by the Strauss formula can be distorted by shifts in the distribution of red blood cells from intravascular pools, as is commonly seen during the clinical course of patients with acutely decompensated heart failure. 86 – 88 , 93 …”