Miller, Wayne L.

Background: Blood volume (BV) in patients with chronic heart failure (HF) is characterized by heterogeneity in volume profiles; one profile being "normal BV". While overall intravascular volume may be considered normal clinically, the relative contributions of red blood cell (RBC) mass and plasma volume (PV) may not be. Objective: Assess how normal is a "normal BV" based on quantitative measures of RBC mass and PV. Methods: Retrospective analysis was undertaken in 395 patients with Class II-III HF. BV was quantitated using indicator-dilution methodology. Cohort was stratified by normal and hypervolemic BV. Results: Of the cohort, 31% (123/395) demonstrated normal total BV and 62% (244/395) hypervolemic BV. Of patients with "normal BV", 36% (44/123) demonstrated normal RBC mass and 60% normal PV (74/123). Importantly, 60% (74/123) demonstrated a deficit in RBC mass (true anemia), while a low hemoglobin (<12 g/dL) was present in just 29% (36/123). An excess in RBC mass (erythrocytosis) in 4% (5/123). Notably, true normal BV (i.e., normal RBC mass and normal PV) was observed in only 30% (37/123) of patients with an overall "normal" intravascular volume. Conclusions: Findings reveal that "normal BV" can be misleading by concealing substantial variability in RBC mass (including unrecognized anemia and erythrocytosis) as well as different degrees of PV expansion and contraction. An actual normal BV was identified in a minority of "normal BV" patients. This underscores the importance of looking beyond overall "normal BV" to the contributing elements of RBC mass and PV with significant implications for patient management and outcomes.

This analysis provides a novel assessment of the relationship between the severity of right ventricular dysfunction (RVD) and blood volume expansion (BVE) on clinical outcomes in patients with chronic left-sided heart failure. Findings demonstrate that despite the high prevalence of moderate or greater RVD, persistent BVE was associated with better 1-year event-free survival relative to normal BV. Hypothesis-generating, this suggests that BVE may provide an adaptive response compensating in part for the impact of RVD in chronic HF.

Background Venous hematocrit (vHct) is commonly used to inform blood volume (BV) status and stratify cardiovascular risk. However, vHct defines a percentage of red blood cells (RBCs) to total BV; therefore, similar vHcts can reflect significantly different absolute BVs and RBC mass/plasma volume profiles. This analysis explores how quantitative measures of BV enhance vHct reliability as a biomarker in heart failure. Methods A retrospective analysis was undertaken in 395 patients stratified by vHcts reflecting clinically heart failure–relevant cut points (35% and 40%). BV was quantitated by the indicator‐dilution methodology using iodinated‐131 labeled albumin. Kaplan–Meier analyses compared outcomes. Results Quantitative absolute BVs on average did not differ between vHct subgroups above or below cut points; however, the distribution of RBC mass and plasma volume profiles varied significantly. A normal BV profile was measured in approximately one third of cohort patients and BV hypervolemia in 58%, driven largely by plasma volume expansions (72% of cohort), all with similar distributions above and below cut points. In contrast, profiles of deficits in RBC mass (anemia) and excess (erythrocythemia) were more frequent below and above cut points, respectively, but not exclusively, with 14% of patients demonstrating contrasting RBC mass profiles. Kaplan–Meier analyses provided aggregate support for vHct to stratify heart failure–related outcomes but do not account for misclassified patients. Conclusions VHcts lack capacity to discriminate absolute BVs or the variability in RBC mass and plasma volume profiles above or below cut points. Therefore, quantitative BV measurements are key to adding specificity to individual vHct values, which permits reliable identification of BV status, assignment of appropriate risk, and guidance in management.

BACKGROUND: Blood volume (BV) profiles vary markedly in patients with heart failure (HF), but how HF phenotypes and patient sex impact volume profiles remain to be explored. The aim of the study was to differentiate BV, plasma volume, and red blood cell mass profiles by phenotypes of preserved and reduced left ventricular ejection fractions and assess the impact of patient sex on profile heterogeneity. METHODS: Retrospective analysis of clinical and BV data was undertaken in patients with chronic New York Heart Association II–III heart failure. BV was quantitated using the nuclear medicine indicator-dilution methodology. RESULTS: A total of 530 BV analyses (360 HF with reduced ejection fraction and 170 HF with preserved ejection fraction) were identified in 395 unique patients. Absolute BV was greater in HF with reduced ejection fraction (6.7±1.8 versus 5.9±1.6 liters: P <0.001); however, large variability in frequency distribution of volume profiles was observed in both phenotypes (−22% deficit to +109% excess relative to normal volumes). HF with reduced ejection fraction was characterized by a higher prevalence of BV expansion ≥+25% of normal (39% versus 26%; P =0.003), and HF with preserved ejection fraction was characterized a by more frequent normal BV (42% versus 24%; P <0.001). Male sex in both phenotypes was associated with a larger absolute BV (7.0±1.6 versus 5.1±1.3 liters; P <0.001) and higher frequency of large BV and plasma volume expansions above normal (both P <0.001), while females in both phenotypes demonstrated a higher prevalence of normal BV and plasma volume (both P <0.001). CONCLUSIONS: Findings support significant differences in BV, plasma volume, and red blood cell mass profile distributions between heart failure phenotypes, driven in large part by sex-specific factors. This underscores the importance of identifying and distinguishing individual patient volume profiles to help guide volume management strategies.

The novel findings of this study demonstrate that blood volume profiles while highly variable in clinically compensated patients with HF on stable medical therapy do not change substantially over a 6-mo period regardless of baseline expanded or normal blood volumes. This lack of change in volume profiles particularly from an expanded blood volume has implications for long-term volume management and also for how we understand the pathophysiology of volume homeostasis in chronic HF.

AbstractIntravascular volume is largely regulated by the kidneys but how differences in intravascular volume profiles interact with chronic kidney disease (CKD) to influence outcomes in chronic heart failure (HF) has not been explored. Our hypothesis was that a greater degree of volume expansion (VE) would moderate the impact of CKD on HF‐related clinical outcomes. Quantitative blood volume (BV) data were available in 137 patients at the time of hospital discharge using a nuclear medicine radiolabeled albumin indicator‐dilution technique. The study patients were stratified by the cohort median glomerular filtration rate (GFR, 44 ml/min/1.73 m2). An a priori cut‐point of ≥+25% above normal BV was then used to further stratify the two GFR subgroups and prospectively analyzed for 1‐year HF‐related mortality or 1st re‐hospitalization. Persistent BV expansions ≥+25% were present in 51% of the cohort. In the subgroup with GFR above the median (N = 68) greater or lesser BV expansion from +25% did not differentiate outcomes. However, in the subgroup with GFR below the median (N = 69), BV expansion‐stratified risk (log‐rank p = 0.022) with <+25% VE associated with poorer outcomes, while VE ≥ + 25% was associated with lower risk and comparable to GFR above the median. In patients with chronic HF, significant intravascular VE and CKD are common co‐existing conditions. The presence of larger VE, however, appears to be a factor mitigating the impact of declining renal function on clinical outcomes, and as an element of volume pathophysiology warrants further study.

Fluid volume homeostasis in health and heart failure (HF) requires a complex interaction of 2 systems, the intravascular and interstitial‐lymphatic circulations. With the development of HF both the intravascular and interstitial compartments undergo variable degrees of volume remodeling which can include significant expansion. This reflects the impact of multiple pathophysiologic mechanisms on both fluid compartments which initially play a compensatory role to stabilize intravascular circulatory integrity but with progression in HF can evolve to produce the various manifestations of volume overload and clinical HF congestion. The intent of this review is to help enhance recognition of the pathophysiologic and clinical importance of the interlinked roles of these 2 circulatory systems in volume regulation and chronic HF. It would also be hoped that a better understanding of the interacting functions of the intravascular and interstitial‐lymphatic fluid compartments can potentially aid development of novel management strategies particularly addressing the generally undertargeted interstitial‐lymphatic system and help bring such approaches forward through a more integrated view of these 2 circulatory systems.