Blood volume expansion, normovolemia, and clinical outcomes in chronic human heart failure: more is better

Congestion/decongestion in heart failure: what does it mean, how do we assess it, and what are we missing?-is there utility in measuring volume?

Clinical congestion remains a major cause of hospitalization and re-hospitalizations in patients with chronic heart failure (HF). Despite the high prevalence of this issue and clinical concern in HF practice, there is limited understanding of the complex pathophysiology relating to the "congestion" of congestive HF. There is no unifying definition or clear consensus on what is meant or implied by the term "congestion." Further, the discordance in study findings relating congestion to physical signs and symptoms of HF, cardiac hemodynamics, or metrics of weight change or fluid loss with diuretic therapy has not added clarity. In this review, these factors will be discussed to add perspective to this issue and consider the factors driving "congestion." There remains a need to better understand the roles of fluid retention promoting intravascular and interstitial compartment expansions, blood volume redistribution from venous reservoirs, altered venous structure and capacity, elevated cardiac filling pressure hemodynamics, and heterogeneous intravascular volume profiles (plasma volume and red blood cell mass) with a goal to help demystify "congestion" in HF. Further, this includes highlighting the importance of recognizing that congestion is not the result of a single pathway but a complex of responses some of which produce symptoms while others do not; yet, we confine these varied responses to the single and somewhat vague term "congestion."

Understanding the variability in red cell and plasma volume combinations can help guide management in heart failure

AIMS

Quantitative methods have shown clinically significant heterogeneity in blood volume (BV) profiles across heart failure (HF) phenotypes. These profiles extend from hypovolaemia to normal BV and to variable degrees of BV hypervolaemia, frequently with similar clinical presentations. However, a comprehensive survey of BV profiles providing practical clinical guidance for the interpretation and management of quantitative plasma volume (PV) and red blood cell (RBC) mass findings has not been reported. The intent of this study is to advance this concept through a multicentre analysis.

METHODS AND RESULTS

A retrospective analysis of clinical and BV data was undertaken in stable NYHA class II-III HF patients (N = 546). BV was quantitated using established nuclear medicine indicator-dilution methodology. Differing combinations of PV and RBC mass were identified contributing to marked heterogeneity in overall BV profiles. A quantitatively normal BV was identified in 32% of the cohort but of these only ~1/3 demonstrated a true normal BV (i.e., normal PV + normal RBC mass). The remaining portion of normal BV profiles reflected balanced combinations of compensatory PV expansion with RBC mass deficit (anaemia) (14% of cohort) and PV contraction with RBC mass excess (erythrocythemia) (6% of cohort). Main contributors to BV hypervolaemia were PV excess with a normal RBC mass (21% of cohort; 23% female) and PV excess with erythrocythemia (24% of cohort; 26% female). Hypovolaemia was predominately defined by RBC mass deficit with a normal PV (6% of cohort; 57% female) or RBC mass deficit with PV contraction (5% of cohort; 48% female).

CONCLUSIONS

Findings support the clinical relevance of identifying and accurately interpreting the varying combinations of PV and RBC mass in patients with chronic HF. This in turn helps guide appropriate individualized patient management strategies. A practical volume-based guideline is provided in an effort to aid clinician interpretation.

Comparison of Blood Volume Profiles in Heart Failure With Preserved and Reduced Ejection Fractions: Sex Makes a Difference

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.

Blood volume phenotypes and patient sex in resistant hypertension

The relationship of blood volume (BV) to systemic blood pressure (BP) is not well defined in resistant hypertension (RH). The goal of this study was to examine the extent to which systemic BP stratified by patient sex would impact BV phenotypes. A retrospective analysis of clinical and quantitative BV data was undertaken in a cohort of ambulatory patients with a history of controlled and uncontrolled RH. We analyzed 253 unique BVs with 54% of patients above goal BP of <150 mmHg. BV phenotypes were highly variable but no correlation of systolic BP to absolute BV or percentage deviation from normal volume was identified in either sex. Males demonstrated overall larger absolute BVs with higher prevalence of large plasma volume (PV) expansion; females were overall more hypovolemic by total BV but with a higher frequency of normal PV than males. Females trended towards more RBC mass deficit (true anemia) (49% vs. 38%. P  = 0.084) while more males demonstrated RBC mass excess (erythrocythemia) (21% vs. 11%, P  = 0.029). Importantly, a significant portion (52%) of patients with true anemia identified by BVA would go undetected by hemoglobin measurement alone. BV phenotypes are highly diverse in patients with RH. However, absolute BV or variability in BV phenotypes even when stratified by patient sex did not demonstrate an association with systemic BP. BV phenotyping provides a key to optimizing clinical management by identifying RBC mass profiles particularly distinguishing true anemia, dilutional anemia, and erythrocythemia and the contribution of PV expansion. Findings support the clinical utility of BV phenotyping in RH.

Prognostic implications of volume status assessed by blood volume analysis in ambulatory heart failure

The prognostic implications of intravascular volume status assessed by blood volume analysis (BVA) in ambulatory heart failure (HF) remain uncertain. The incremental benefits of assessing volume status, beyond the well-established filling pressures, in predicting HF outcomes are unknown.

Serial blood volume measurements in patients with compensated chronic heart failure: How do volume profiles change over time?

Among patients with chronic heart failure (HF) intravascular volume profiles vary significantly despite similar clinical compensation. However, little is known regarding changes in blood volume (BV) profiles over time. The objective of this analysis was to identify the extent and character of changes in volume profiles over time. A prospective analysis was undertaken in patients who were hospitalized and treated for fluid overload. Quantitative BV analyses were obtained in a compensated state at hospital discharge (baseline) and follow-up at 1, 3, and 6 mo. Data were available on 10 patients who remained stable without rehospitalization or medication change over a 6-mo period. Baseline BV profiles were highly variable at hospital discharge with an average deviation of +28% above normal in 6 patients and normal BV in 4 patients. Over the follow-up period, the median change in BV was -201 mL [-3% (-6, +3%)] from baseline with profiles remaining in the same volume category in 9 out of 10 patients. Crossover from normal BV to mild contraction (-13% of normal) occurred in one patient. Red blood cell mass demonstrated the largest change over 6 mo [median -275 (-410, +175) mL] with a deviation from normal of -14 (-20, +8) % (reflecting mild anemia). These findings suggest that BV profiles in clinically compensated patients with HF do not change substantially over a 6-mo period regardless of baseline expanded or normal BV. This lack of change in volume profiles particularly from an expanded BV has implications for long-term volume management, clinical outcomes, and also our understanding of volume homeostasis in HF.NEW & NOTEWORTHY 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.

Measurement of Blood Volume in Patients with Heart Failure: Clinical Relevance, Surrogates, Historical Background and Contemporary Methodology

The development of clinical congestion resulting from volume overload, either by renal fluid retention or redistribution of blood volume from venous reservoirs, is a recurrent scenario in patients with chronic heart failure (HF). As a result, the treatment of congestion, most commonly by initiating aggressive diuretic therapy, is a front-line issue in the management of patients with HF. However, the association of clinical congestion and volume overload with physical signs and symptoms, as well as other surrogates of volume assessment, has limitations in accuracy and, therefore, reliability to direct appropriate interventions. The ability to quantitate intravascular volume and identify the variability in volume profiles among patients with HF can uniquely inform individualized volume management and aid in risk stratification. This tool is provided by contemporary nuclear medicine-based BVA-100 methodology, which uses the well-established indicator-dilution principle and is a requested topic for discussion in this review.

Relationship between BUN/Cr and Prognosis of HF Across the Full Spectrum of Ejection Fraction

BACKGROUND

In patients with heart failure (HF), due to the relative deficiency of blood volume, neurohormone system activation leads to renal vasoconstriction, which affects the content of blood urea nitrogen (BUN) and creatinine (Cr) in the body, while BUN and Cr are easily affected by other factors. Therefore, BUN/Cr can be used as another marker for the prognosis of HF.

OBJECTIVE

Explore the prognosis of adverse outcome of HF in the high BUN/Cr group compared with the low BUN/Cr group across the full spectrum of ejection fraction.

METHODS

From 2014 to 2016, symptomatic hospitalized HF patients were recruited and followed up to observe adverse cardiovascular outcomes. Logistic analysis and COX analysis were performed to determine significance. p-values <0.05 were considered statistically significant.

RESULTS

In the univariate logistic regression analysis, the high BUN/Cr group had a higher risk of adverse outcome in heart failure with reduced ejection fraction (HFrEF) and heart failure with preserved ejection fraction (HFpEF). Multivariate logistic regression analysis showed that the risk of cardiac death in the HFrEF group was higher than that in the low BUN/Cr group, while the risk of all-cause death was significant only in 3 months (p<0.05) (Central Illustration). The risk of all-cause death in the high BUN/Cr in the HFpEF group was significantly higher than that in the low BUN/Cr group at two years.

CONCLUSION

The high BUN/Cr group is related to the risk of poor prognosis of HFpEF, and is not lower than the predictive value of left ventricular ejection fraction (LVEF).

Blood volume and chronic kidney disease in heart failure - Can volume expansion help balance the Cardio-Renal Axis for better clinical outcomes?

Intravascular 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.

Clinically unrecognized plasma volume expansion predicts long-term all-cause-mortality in chronic heart failure

INTRODUCTION

Chronic heart failure (CHF) is associated with elevated total blood volume (BV) and distinct phenotypes of total red cell volume (RCV) and plasma volume (PV) elevations. Especially PV expansion during clinical decompensation is linked with adverse clinical outcomes. The role of PV expansion in compensated CHF patients is less clear. Aim of the present study is to investigate the impact of BV parameters on long-term mortality in CHF patients investigated at a compensated state.

METHODS AND RESULTS

BV, PV and RCV were determined in 44 (9 female) compensated CHF patients using an abbreviated carbon monoxide method, who were followed up for 6.0 years, (range: 3.7-6.5 years) for all-cause mortality. In univariate analysis PV expansion but not BV and RCV predicted all-cause mortality (p = .021). A cutoff of 1800 ml PV/m² body-surface area allows stratification for all-cause mortality (p = .044). PV expansion but not RCV reduction explains the significantly lower hematocrit values of nonsurvivors.

DISCUSSION

In this pilot study, PV expansion, which was unnoticed from a clinician's perspective, but is indicated by significantly lower hematocrit, appears to be a relevant predictor of long-term all-cause mortality. Whether PV expansion constitutes an adverse CHF phenotype and can be targeted by diuretic therapy is currently unclear.

Fluid Volume Homeostasis in Heart Failure: A Tale of 2 Circulations

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.