Heart Failure Outcomes With Volume-Guided Management

Clinical importance of distinguishing true anemia from dilutional pseudo-anemia: Consequences of a 3-year follow-up volume assessment in a heart failure patient

In chronic heart failure, dilutional anemia and hypervolemia may occur due to plasma volume expansion, the latter sometimes exacerbated by an increase in red cell volume. Diagnosis and a therapeutic strategy require determination of vascular volumes.

Role of splanchnic circulation in the pathogenesis of heart failure: State-of-the-art review

A hallmark of heart failure (HF), whether it presents itself during rest or periods of physical exertion, is the excessive elevation of intracardiac filling pressures at rest or with exercise. Many mechanisms contribute to the elevated intracardiac filling pressures, and notably, the concept of volume redistribution has gained attention as a cause of the elevated intracardiac filling pressures in patients with HF, particularly HF with preserved ejection fraction, who often present without symptoms at rest, with shortness of breath and fatigue appearing only during exertion. This phenomenon suggests cardiopulmonary system non-compliance and inappropriate volume distribution between the stressed and unstressed blood volume components. A substantial proportion of the intravascular blood volume is in the splanchnic vascular compartment in the abdomen. Preclinical and clinical investigations support the critical role of the sympathetic nervous system in modulating the capacitance and compliance of the splanchnic vascular bed via modulation of the greater splanchnic nerve (GSN). The GSN activation by stressors such as exercise causes excessive splanchnic vasoconstriction, which may contribute to the decompensation of chronic HF via volume redistribution from the splanchnic vascular bed to the central compartment. Accordingly, for example, GSN ablation for volume management has been proposed as a potential therapeutic intervention to increase unstressed blood volume. Here we provide a comprehensive review of the role of splanchnic circulation in the pathogenesis of HF and potential novel treatment options for redistributing blood volume to improve symptoms and prognosis in patients with HF.

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.

Determinants and reference values for blood volume and total hemoglobin mass in women and men

Blood volume (BV) is an important clinical parameter and is usually reported per kg of body mass (BM). When fat mass is elevated, this underestimates BV/BM. One aim was to study if differences in BV/BM related to sex, age, and fitness would decrease if normalized to lean body mass (LBM). The analysis included 263 women and 319 men (age: 10-93 years, body mass index: 14-41 kg/m2 ) and 107 athletes who underwent assessment of BV and hemoglobin mass (Hbmass ), body composition, and cardiorespiratory fitness. BV/BM was 25% lower (70.3 ± 11.3 and 80.3 ± 10.8 mL/kgBM ) in women than men, respectively, whereas BV/LBM was 6% higher in women (110.9 ± 12.5 and 105.3 ± 11.2 mL/kgLBM ). Hbmass /BM was 34% lower (8.9 ± 1.4 and 11.5 ± 11.2 g/kgBM ) in women than in men, respectively, but only 6% lower (14.0 ± 1.5 and 14.9 ± 1.5 g/kgLBM )/LBM. Age did not affect BV. Athlete's BV/BM was 17.2% higher than non-athletes, but decreased to only 2.5% when normalized to LBM. Of the variables analyzed, LBM was the strongest predictor for BV (R2  = .72, p < .001) and Hbmass (R2  = .81, p < .001). These data may only be valid for BV/Hbmass when assessed by CO re-breathing. Hbmass /LBM could be considered a valuable clinical matrix in medical care aiming to normalize blood homeostasis.

Estimated plasma volume is not a robust indicator of the severity of congestion in patients with heart failure

BACKGROUND

Congestion is the main cause of morbidity and a prime determinant of survival in patients with heart failure (HF). However, the assessment of congestion is subjective and estimation of plasma volume (ePV) has been suggested as a more objective measure of congestion. This study aimed to explore the relationships and interactions between ePV, the severity of congestion and survival using a nationwide registry.

METHODS

Of the 1054 patients with HF enrolled in the registry, 769 had sufficient data to calculate ePV (using the Duarte, Kaplan, and Hakim equations) and relative plasma volume status (rPVS), and these patients were subsequently included in the present analysis. The severity of congestion was assessed using a 6-point congestion score (CS). Patients were divided into three groups according to the degree of congestion.

RESULTS

Out of four equations tested, only ePVDuarte and rPVS were statistically higher in patients with severe congestion as compared to patients with no congestion (p<0.001 for both). Both ePVDuarte (r = 0.197, p<0.001) and rPVS (r = 0.153, p<0.001) showed statistically significant correlations with CS and both had a modest accuracy (70.4% for ePVDuarte and 69.4% for rPVS) to predict a CS ≥3. After a median follow up of 496 days, both ePVDuarte (OR:1.14,95%CI:1.03-1.26, p = 0.01) and rPVS (OR:1.02, 95%CI:1.00-1.03, p = 0.03) were associated with all-cause mortality after adjusting for demographic and clinical variables. However, none of the indices were associated with mortality following the introduction of CS to the models (p>0.05 for both).

CONCLUSIONS

Elevated ePVDuarte and rPVS were indicators of congestion but with a limited robustness, and either parameter could be clinically useful when a comprehensive clinical evaluation of congestion is not feasible.

Patient Selection and End Point Definitions for Decongestion Studies in Acute Decompensated Heart Failure: Part 2

Congestion is the most common manifestation of acute decompensated heart failure (ADHF). Residual congestion despite initial medical therapy is common and is recognized to be associated with worse outcomes; however, there are currently no standardized definition regarding decongestion end point. In the second part of this 2-part review, we provide a critical appraisal of decongestion definitions previously used in ADHF studies, review alternative metrics to define severity of volume overload, and propose a more granular 4-class congestion grading scheme and decongestion end point definitions that could potentially be included in future ADHF trials and consensus definitions.

Patient Selection and End Point Definitions for Decongestion Studies in Acute Decompensated Heart Failure: Part 1

Despite recent advances in the treatment of patients with chronic heart failure, acute decompensated heart failure remains associated with significant mortality and morbidity because many novel therapies have failed to demonstrate meaningful benefit. Persistent congestion in the setting of escalating diuretic therapy has been repeatedly shown to be a marker of poor prognosis and is currently being targeted by various emerging device-based therapies. Because these therapies inherently carry procedural risk, patient selection is key in the future trial design. However, it remains unclear which patients are at a higher risk of residual congestion or adverse outcomes despite maximally tolerated decongestive therapy. In the first part of this 2-part review, we aimed to outline patient risk factors and summarize current evidence for early recognition of high-risk profile for residual congestion and adverse outcomes. These factors are classified as relating to the following: (1) previous clinical course, (2) severity of congestion, (3) diuretic response, and (4) degree of renal impairment. We also aimed to provide an overview of key inclusion criteria in recent acute decompensated heart failure trials and investigational device studies and propose potential criteria for selection of high-risk patients in future trials.

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.

A semi-automated device rapidly determine circulating blood volume in healthy males and carbon monoxide uptake kinetics of arterial and venous blood

We examined whether a semi-automated carbon monoxide (CO) rebreathing method accurately detect changes in blood volume (BV) and total hemoglobin mass (tHb). Furthermore, we investigated whether a supine position with legs raised reduced systemic CO dilution time, potentially allowing a shorter rebreathing period. Nineteen young healthy males participated. BV and tHb was quantified by a 10-min CO-rebreathing period in a supine position with legs raised before and immediately after a 900 ml phlebotomy and before and after a 900 ml autologous blood reinfusion on the same day in 16 subjects. During the first CO-rebreathing, arterial and venous blood samples were drawn every 2 min during the procedure to determine systemic CO equilibrium in all subjects. Phlebotomy decreased (P < 0.001) tHb and BV by 166 ± 24 g and 931 ± 247 ml, respectively, while reinfusion increased (P < 0.001) tHb and BV by 143 ± 21 g and 862 ± 250 ml compared to before reinfusion. After reinfusion BV did not differ from baseline levels while tHb was decreased (P < 0.001) by 36 ± 21 g. Complete CO mixing was achieved within 6 min in venous and arterial blood, respectively, when compared to the 10-min sample. On an individual level, the relative accuracy after donation for tHb and BV was 102-169% and 55-165%, respectively. The applied CO-rebreathing procedure precisely detect acute BV changes with a clinically insignificant margin of error. The 10-min CO-procedure may be reduced to 6 min with no clinical effects on BV and tHb calculation. Notwithstanding, individual differences may be of concern and should be investigated further.

Acute Cardiorenal Syndrome: An Update

The complex dynamic pathophysiological interplay between the heart and kidney causes a vicious cycle of worsening renal and/or cardiovascular function. Acute decompensated heart failure causing worsening renal function defines Type 1 cardiorenal syndrome (CRS). Altered hemodynamics coupled with a multitude of nonhemodynamic factors namely pathological activation of the renin angiotensin aldosterone system and systemic inflammatory pathways mechanistically incite CRS type 1. A multipronged diagnostic approach utilizing laboratory markers, noninvasive and/or invasive modalities must be implemented to enable timely initiation of effective treatment strategies. In this review, we discuss the pathophysiology, diagnosis, and emerging treatment options for CRS type 1.

New Insight in Cardiorenal Syndrome: From Biomarkers to Therapy

Cardiorenal syndrome consists in the coexistence of acute or chronic dysfunction of heart and kidneys resulting in a cascade of feedback mechanisms and causing damage to both organs associated with high morbidity and mortality. In the last few years, different biomarkers have been investigated with the aim to achieve an early and accurate diagnosis of cardiorenal syndrome, to provide a prognostic role and to guide the development of targeted pharmacological and non-pharmacological therapies. In such a context, sodium-glucose cotransporter 2 (SGLT2) inhibitors, recommended as the first-line choice in the management of heart failure, might represent a promising strategy in the management of cardiorenal syndrome due to their efficacy in reducing both cardiac and renal outcomes. In this review, we will discuss the current knowledge on the pathophysiology of cardiorenal syndrome in adults, as well as the utility of biomarkers in cardiac and kidney dysfunction and potential insights into novel therapeutics.

Assessment of Volume Status in Hospitalized Patients With Chronic Heart Failure

Assessment of volume status in hospitalized patients with heart failure is a critically important diagnostic skill that clinicians utilize frequently. However, accurate assessment is challenging and there is often significant inter-provider disagreement. This review serves as an appraisal of current methods of volume assessment amongst different categories of evaluation including patient history, physical exam, laboratory analysis, imaging, and invasive procedures. Within each category, this review highlights methods that are particularly sensitive or specific, or those that carry impactful positive or negative likelihood ratios. Utilization of the information that this review provides will allow clinicians to determine volume status of hospitalized heart failure patients more accurately and more precisely in order to provide appropriate and effective therapies.

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.

Reshaping Treatment of Heart Failure with Preserved Ejection Fraction

Current data indicate that in the community, approximately 50% of patients with heart failure (HF) have preserved left ventricular (LV) ejection fraction (LVEF)—the so-called HFpEF. Treatment of HFpEF has been considered an unmet need for decades. We believe that the main underlying reasons have been (a) the ever-changing LVEF cut-offs used for HF classification; (b) controversies regarding the definition of the LVEF normal range; (c) the fact that HFpEF does not represent a phenotype, but a category of diseases with entirely different characteristics (hypertensive heart disease, valvular heart disease (VHD), hypertrophic cardiomyopathy (HCM) etc.); (d) the lack of recognition that hypertensive HFpEF is the most common and important HFpEF phenotype; (e) the assumption that neurohormonal overactivity is absent in HF patients with a LVEF > 45−50% which has been proven to be wrong. Current HFpEF trials, in which the vast majority of the participants suffered from hypertension (HTN), whereas VHD and HCM were absent, demonstrated that neurohormonal and sodium-glucose cotransporter 2 (SGLT2) inhibitors are effective in HF patients over a wide LVEF range. Thus, restricting these lifesaving treatments to HF patients with reduced LVEF is not justified anymore and it should be additionally considered for HFpEF patients suffering from HTN.

Estimated plasma volume status is a modest predictor of true plasma volume excess in compensated chronic heart failure patients

Plasma volume and especially plasma volume excess is a relevant predictor for the clinical outcome of heart failure patients. In recent years, estimated plasma volume based on anthropometric characteristics and blood parameters has been used whilst direct measurement of plasma volume has not entered clinical routine. It is unclear whether the estimation of plasma volume can predict a true plasma volume excess. Plasma volume was measured in 47 heart failure patients (CHF, 10 female) using an abbreviated carbon monoxide rebreathing method. Plasma volume and plasma volume status were also estimated based on two prediction formulas (Hakim, Kaplan). The predictive properties of the estimated plasma volume status to detect true plasma volume excess > 10% were analysed based on logistic regression and receiver operator characteristics. The area under the curve (AUC) to detect plasma volume excess based on calculation of plasma volume by the Hakim formula is 0.65 (with a positive predictive value (PPV) of 0.62 at a threshold of - 16.5%) whilst the AUC for the Kaplan formula is 0.72 (PPV = 0.67 at a threshold of - 6.3%). Only the estimated plasma volume status based on prediction of plasma volume by the Kaplan formula formally appears as an acceptable predictor of true plasma volume excess, whereas calculation based on the Hakim formula does not sufficiently predict a true plasma volume excess. The low positive predictive values for both methods suggest that plasma volume status estimation based on these formulas is not suitable for clinical decision making.

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

Expansion in blood volume (BV) is a well-recognized response to arterial underfilling secondary to impaired cardiac output in heart failure (HF). However, the effectiveness of this response in terms of outcomes remains inadequately understood. Prospective analysis was undertaken in 110 patients with HF hospitalized and treated for fluid overload. BVs were measured in a compensated state at the hospital discharge using the indicator-dilution methodology. Data were analyzed for composite 1-year HF-related mortality/first rehospitalization. Despite uniform standard of care, marked heterogeneity in BVs was identified across the cohort. The cohort was stratified by BV expansion greater than or equal to +25% above normal (51% of cohort), mild-moderate expansion (22%), and normal BV (27%). Kaplan-Meier (K-M) survival estimates and regression analyses revealed BV expansion (greater than or equal to +25%) to be associated with better event-free survival relative to normal BV (P = 0.038). Increased red blood cell mass (RBCm; RBC polycythemia) was identified in 43% of the overall cohort and 70% in BV expansion greater than or equal to +25%. K-M analysis demonstrated polycythemia to be associated with better outcomes compared with normal RBCm (P < 0.002). Persistent BV expansion to include RBC polycythemia is common and, importantly, associated with better clinical outcomes compared with normal total BV or normal RBCm in patients with chronic HF. However, compensatory BV expansion is not a uniform physiological response to the insult of HF with marked variability in BV profiles despite uniform standard of care diuretic therapy. Therefore, recognizing the variability in volume regulation pathophysiology has implications not only for impact on clinical outcomes and risk stratification but also potential for informing individualized volume management strategies.NEW & NOTEWORTHY The novel findings of this study demonstrate that intravascular volume profiles among the patients with chronic heart failure (HF) vary substantially even with similar clinical compensation. Importantly, a profile of blood volume (BV) expansion (compared with a normal BV) is associated with lower HF mortality/morbidity. Furthermore, RBC polycythemia is common and independently associated with improved outcomes. These observations support BV expansion with RBC polycythemia as a compensatory mechanism in chronic HF.

Diuresis-Related Weight Loss Reflects Interstitial Compartment Decongestion with Minimal Impact on Intravascular Volume Expansion or Outcomes in Post-Acute Heart Failure: Metrics of Decongestion and Volume Status

BACKGROUND

Findings from heart failure (HF) studies linking diuresis-related weight loss to clinical decongestion and outcomes are mixed. Differential responses of interstitial and intravascular volume compartments to diuretic therapy and heterogeneity in volume profiles may confound the clinical interpretation of weight loss in patients with HF.

METHODS AND RESULTS

Data were prospectively collected in hospitalized patients requiring diuresis. Plasma volume (PV) was measured using I-131-labelled albumin indicator-dilution methodology. The cohort was stratified by tertiles of weight loss and analyzed for interstitial fluid loss relative to changes in PV and HF-related morality or first rehospitalization. Among 92 patients, the admission PV was expanded +42% (4.7 ± 1.2 L) above normal with significant variability (14% normal PV, 18% mild-moderate expansion, and 68% with large PV expansion [>+25% above normal]). With diuresis there were proportional decreases in interstitial volume (-6.5 ± 4.4%) and PV (-7.5 ± 11%); however, absolute decreases in the PV (-254 mL, interquartile range -11 to -583 mL) were less than 10% of interstitial volume loss (-5040 mL, interquartile range -2800 to -7989 mL); greater interstitial fluid loss did not translate into better outcomes (log-rank P = .430).

CONCLUSIONS

Diuresis-related decreases in weight reflect fluid loss from the interstitial compartment with only minor changes in the PV and without an impact on outcomes. Further, the degree of PV expansion at hospital admission does not drive the magnitude of the diuresis response, even with a wide spectrum of body weights; interstitial fluid overload is preferentially targeted and PV relatively preserved. Therefore, greater interstitial fluid loss reflects clinical decongestion, but not better outcomes, and a limited association with intravascular volume profiles potentially confounding weight loss as a prognostic metric in HF.

Estimated plasma volume status in heart failure: clinical implications and future directions

Congestion is one of the main predictors of poor outcome in patients with heart failure (HF). Assessing and monitoring congestion is essential for optimizing HF therapy. Among the various available methods, serial measurements of estimated plasma volume (ePVS) using routine blood count and/or body weight (e.g., the Strauss, Duarte, Hakim formulas) may be useful in HF management. Further prospective study is warranted to determine whether ePVS can help optimize decongestion therapy (loop diuretics, mineralocorticoid receptor antagonists, SGLT2i) in various HF settings. This narrative review summarizes the recent evidence supporting the association of ePVS with clinical congestion and outcome(s) and discusses future directions for monitoring ePVS in HF.

Time course of red cell volume and plasma volume over six months in compensated chronic heart failure

Background

In patients with chronic heart failure (CHF), volume overload is usually described as an expansion of plasma volume (PV). Additional red cell volume (RCV) expansion also occurs in a relevant fraction of compensated CHF patients. So far, little is known about the stability of these vascular volumes and possible volume excess in compensated CHF patients over time.

Methods and results

This study aims at quantification of blood volume and its components, RCV and PV (raw values and adjusted for sex and anthropometric characteristics, expressed as per cent of the expected normal value), using an abbreviated carbon monoxide (CO) rebreathing method (aCORM) in 14 patients (two women) with systolic CHF at baseline and at a follow‐up visit after approximately 6 months. While a vast heterogeneity was observed concerning RCV (82% to 134% of normalized alues) and PV (72% to 131% of normalized values), the vascular volumes showed a mean change of 1.2% and −1.3% after a mean follow‐up of 183 days.

Conclusions

The vascular volumes including individual volume excess appear to be stable in compensated CHF patients. The reason for this individual volume response concerning both RCV and PV in CHF remains unclear and deserves further clarification.

Pharmacologic and interventional paradigms of diuretic resistance in congestive heart failure: a narrative review

Diuretic volume reduction continues to be the mainstay of congestive heart failure (CHF) management globally. However, diuretic resistance is a critical topic that lacks standardized evidence-based management guidelines accounting for mechanisms of diuretic resistance, renal function, and co-morbidities. Major healthcare utilization consequences result from this. The authors herein reconcile the definition of renal functional decline with emphasis on biomarker-driven assessment. Novel goal-directed treatment approaches are reviewed including hypertonic saline, acetazolamide, sodium-glucose transporter inhibition, sequential nephron blockade and Elabela-APJ axis targeting are reviewed, as well as percutaneous visceral splanchnic sympathectomy (converting a volume-focused to a distribution-focused paradigm).

Plasma Volume Status and Its Association With In-Hospital and Postdischarge Outcomes in Decompensated Heart Failure

BACKGROUND

Prior analyses suggest an association between formula-based plasma volume (PV) estimates and outcomes in heart failure (HF). We assessed the association between estimated PV status by the Duarte-ePV and Kaplan Hakim (KH-ePVS) formulas, and in-hospital and postdischarge clinical outcomes, in the ASCEND-HF trial.

METHODS AND RESULTS

The KH-ePVS and Duarte-ePV were calculated on admission. We assessed associations with in-hospital worsening HF, 30-day composite cardiovascular mortality or HF rehospitalization and 180-day all-cause mortality. There were 6373 (89.2%), and 6354 (89.0%) patients who had necessary characteristics to calculate KH-ePVS and Duarte-ePV, respectively. There was no association between PV by either formula with in-hospital worsening HF. KH-ePVS showed a weak correlation with N-terminal prohormone BNP, and with measures of decongestion such as body weight change and urine output (r < 0.3 for all). Duarte-ePV was trending toward an association with worse 30-day (adjusted odds ratio 1.07, 95% confidence interval [CI] 1.00-1.15, P = .058), but not 180-day outcomes (adjusted hazard ratio 1.03, 95% CI 0.97-1.09, P = .289). A continuous KH-ePVS of >0 (per 10-unit increase) was associated with improved 30-day outcomes (adjusted odds ratio 0.75, 95% CI 0.62-0.91, P = .004). The continuous KH-ePVS was not associated with 180-day outcomes (adjusted hazard ratio 1.05, 95% CI 0.98-1.12, P = .139).

CONCLUSIONS

Baseline PV estimates had a weak association with in-hospital measures of decongestion. The Duarte-ePV trended toward an association with early clinical outcomes in decompensated HF, and may improve risk stratification in HF.

Pathophysiology of Diuretic Resistance and Its Implications for the Management of Chronic Heart Failure

Diuretic resistance implies a failure to increase fluid and sodium (Na+) output sufficiently to relieve volume overload, edema, or congestion, despite escalating doses of a loop diuretic to a ceiling level (80 mg of furosemide once or twice daily or greater in those with reduced glomerular filtration rate or heart failure). It is a major cause of recurrent hospitalizations in patients with chronic heart failure and predicts death but is difficult to diagnose unequivocally. Pharmacokinetic mechanisms include the low and variable bioavailability of furosemide and the short duration of all loop diuretics that provides time for the kidneys to restore diuretic-induced Na+ losses between doses. Pathophysiological mechanisms of diuretic resistance include an inappropriately high daily salt intake that exceeds the acute diuretic-induced salt loss, hyponatremia or hypokalemic, hypochloremic metabolic alkalosis, and reflex activation of the renal nerves. Nephron mechanisms include tubular tolerance that can develop even during the time that the renal tubules are exposed to a single dose of diuretic, or enhanced reabsorption in the proximal tubule that limits delivery to the loop, or an adaptive increase in reabsorption in the downstream distal tubule and collecting ducts that offsets ongoing blockade of Na+ reabsorption in the loop of Henle. These provide rationales for novel strategies including the concurrent use of diuretics that block these nephron segments and even sequential nephron blockade with multiple diuretics and aquaretics combined in severely diuretic-resistant patients with heart failure.

Reproducibility of the CO rebreathing technique with a lower CO dose and a shorter rebreathing duration at sea level and at 2320 m of altitude

Total hemoglobin mass (Hb_mass) is routinely assessed in studies by the carbon monoxide (CO) rebreathing. Its clinical application is often hindered due to the consequent rise in carboxyhemoglobin (%HbCO) and the concern of CO toxicity. We tested the reproducibility of the CO rebreathing with a CO dose of 0.5 mL/kg body mass (CO_0.5) compared to 1.5 mL/kg (CO_1.5) and when shortening the CO rebreathing protocol. Therefore, CO rebreathing was performed 1×/day in eight healthy individuals on four consecutive days. On each day, either CO_0.5 (CO_0.5-1 and CO_0.5-2) or CO_1.5 (CO_1.5-1 and CO_1.5-2) was administered. Venous blood samples to determine %HbCO and quantify Hb_mass were obtained prior to, and at 6 (T₆), 8 (T₈) and 10 min (T₁₀) of CO rebreathing. This protocol was tested at sea level and at 2320 m to investigate the altitude-related measurement error. At sea level, the mean difference (95% limits of agreement) in Hb_mass between CO_0.5-1 and CO_0.5-2 was 26 g (-26; 79 g) and between CO_1.5-1 and CO_1.5-2, it was 17 g (-18; 52 g)_. The respective typical error (TE) corresponded to 2.4% (CO_0.5) and 1.5% (CO_1.5), while it was 6.5% and 3.0% at 2320 m. With CO_0.5, shortening the CO rebreathing resulted in a TE for Hb_mass of 4.4% (T₈ vs. T₁₀) and 14.1% (T₆ vs T₁₀) and with CO_1.5, TE was 1.6% and 5.8%. In conclusion, the CO dose and rebreathing time for the CO rebreathing procedure can be decreased at the cost of a measurement error ranging from 1.5-14.1%.

Empagliflozin in Heart Failure: Diuretic and Cardiorenal Effects

BACKGROUND

Sodium-glucose cotransporter-2 inhibitors improve heart failure-related outcomes. The mechanisms underlying these benefits are not well understood, but diuretic properties may contribute. Traditional diuretics such as furosemide induce substantial neurohormonal activation, contributing to the limited improvement in intravascular volume often seen with these agents. However, the proximal tubular site of action of the sodium-glucose cotransporter-2 inhibitors may help circumvent these limitations.

METHODS

Twenty patients with type 2 diabetes mellitus and chronic, stable heart failure completed a randomized, placebo-controlled crossover study of empagliflozin 10 mg daily versus placebo. Patients underwent an intensive 6-hour biospecimen collection and cardiorenal phenotyping at baseline and again after 14 days of study drug. After a 2-week washout, patients crossed over to the alternate therapy with the above protocol repeated.

RESULTS

Oral empagliflozin was rapidly absorbed as evidenced by a 27-fold increase in urinary glucose excretion by 3 hours (P<0.0001). Fractional excretion of sodium increased significantly with empagliflozin monotherapy versus placebo (fractional excretion of sodium, 1.2±0.7% versus 0.7±0.4%; P=0.001), and there was a synergistic effect in combination with bumetanide (fractional excretion of sodium, 5.8±2.5% versus 3.9±1.9%; P=0.001). At 14 days, the natriuretic effect of empagliflozin persisted, resulting in a reduction in blood volume (-208 mL [interquartile range, -536 to 153 mL] versus -14 mL [interquartile range, -282 to 335 mL]; P=0.035) and plasma volume (-138 mL, interquartile range, -379 to 154±453 mL; P=0.04). This natriuresis was not, however, associated with evidence of neurohormonal activation because the change in norepinephrine was superior (P=0.02) and all other neurohormones were similar (P<0.34) during the empagliflozin versus placebo period. Furthermore, there was no evidence of potassium wasting (P=0.20) or renal dysfunction (P>0.11 for all biomarkers), whereas both serum magnesium (P<0.001) and uric acid levels (P=0.008) improved.

CONCLUSIONS

Empagliflozin causes significant natriuresis, particularly when combined with loop diuretics, resulting in an improvement in blood volume. However, off-target electrolyte wasting, renal dysfunction, and neurohormonal activation were not observed. This favorable diuretic profile may offer significant advantage in the management of volume status in patients with heart failure and may represent a mechanism contributing to the superior long-term heart failure outcomes observed with these agents. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03027960.

The Cardiorenal Syndrome in Heart Failure

Abnormal fluid handling leads to physiologic abnormalities in multiple organ systems. Deranged hemodynamics, neurohormonal activation, excessive tubular sodium reabsorption, inflammation, oxidative stress, and nephrotoxic medications are important drivers of harmful cardiorenal interactions in patients with heart failure. Accurate quantitative measurement of fluid volume is vital to individualizing therapy for such patients. Blood volume analysis and pulmonary artery pressure monitoring seem the most reliable methods for assessing fluid volume and guiding decongestive therapies. Still the cornerstone of decongestive therapy, diuretics' effectiveness decreases with progression of heart failure. Extracorporeal ultrafiltration, an alternative to diuretics, has been shown to reduce heart-failure events.

Rapid nuclear medicine blood volume analysis for emergency assessment

Assessment of fluid status can play a critical role in the diagnosis and management of emergent conditions such as trauma, shock, decompensated heart failure, syncope, and hypertension. Unfortunately, common methods are all qualitative and/or indirect, and often inaccurate. With the recent introduction of a modernized method of nuclear medicine blood volume analysis (NM-BVA), offering results in 90 min or less as well as improved precision and ease of performance, this decade-old technique is for the first time a viable tool in the emergent setting. In this review, we discuss the history of NM-BVA, the modern method, and our institution’s experience implementing this method.

Relationship between plasma volume and essential blood constituents in patients with heart failure and preserved ejection fraction

INTRODUCTION

Notwithstanding recent progress on molecular mechanisms underlying heart failure with preserved ejection fraction (HFpEF), multiple pathophysiological aspects of this condition including the basis of anaemia and other haematological disorders remain unresolved. In this study, we sought to determine the relationship of plasma volume (PV), a plausible confounding factor for the concentration of solutes in blood, with key haematological markers in HFpEF patients.

METHODS

Total circulating PV was determined with high precision, automated carbon monoxide rebreathing in 24 stable HFpEF patients (70 ± 8 years, left ventricular ejection fraction = 55±5%) and 18 healthy age- and sex-matched control (HC) individuals. Linear regression analyses were performed to determine the association of PV with a comprehensive set of haematological variables.

RESULTS

Haematocrit (40·1 ± 4·9 versus 43·6 ± 2·7%, P = 0·004) and haemoglobin concentration (131 ± 16 versus 142 ± 7 g l^-1 , P = 0·003) were reduced in HFpEF patients compared with HC individuals. In regression analyses, PV was negatively associated with haematocrit (r = -0·45, P = 0·029) and haemoglobin concentration (r = -0·44, P = 0·030) in HFpEF patients, whereas these variables were not associated with PV in HC individuals (P≥0·198). Regarding blood electrolytes, PV was negatively associated with K⁺ (r = -0·43, P = 0·036) and Ca²⁺ (r = -0·44, P = 0·032) in HFpEF patients but not in HC individuals (P≥0·734). None of the above associations were detected in HFpEF patients when using ideal instead of measured PV.

CONCLUSION

The blood concentration of routine markers of anaemia and electrolyte balance is specifically and linearly associated with PV in HFpEF patients. Excess or deficit of circulating PV may confound clinical diagnosis in this population.

The Effect of Positive Airway Pressure Treatment of Obstructive and Central Sleep Apnea on the Recurrence of Atrial Fibrillation/Flutter Postintervention

STUDY OBJECTIVES

A strong association between sleep-disordered breathing (SDB) and atrial fibrillation and/or atrial flutter (AF) has consistently been observed in epidemiologic and interventional studies. The effect of positive airway pressure (PAP) on AF recurrence is inconclusive. This study sought to evaluate the effectiveness of PAP therapy for SDB on AF recurrence.

METHODS

This was a single-center, retrospective study conducted at a tertiary referral center. All adult patients who had SDB on polysomnography and underwent AF intervention (ablation or cardioversion) following polysomnography from January 1992-December 2014 were analyzed. Primary outcome was time to first-documented recurrence of AF after AF intervention by Kaplan-Meier estimates.

RESULTS

Among 30,188 patients with obstructive and central SDB, 429 had this diagnosis before AF intervention; 269 were "PAP-adherent users," the remaining 160 were "PAP-nonusers." Patients in both groups had similar age, sex, body mass index (BMI), ejection fraction, left atrial volume index (LAVI), antiarrhythmic medications, diabetes mellitus, systemic hypertension, and heart failure diagnoses. Time to recurrence of AF postintervention was no different in PAP-adherent users and nonusers (4.8 and 4.1 months respectively, P = .7). Cardioversion (compared to catheter ablation) was the strongest independent predictor of recurrent AF (hazard ratio [HR] 2.02, 95% confidence interval [CI] 1.39-2.94, P < .001). BMI and LAVI were also significant predictors of recurrence in adjusted analyses (HR 1.01, 95% CI 1.003-1.023, P = .10 and HR 1.01, 95% CI 1.001-1.019, P = .024 respectively).

CONCLUSIONS

Our study found no effect of PAP treatment of SDB on time to recurrence of AF post-AF intervention. Increased risk of recurrent AF was associated with high BMI and LAVI. These findings may affect the clinical management of AF.

Heart Failure With Preserved Ejection Fraction In Perspective

Approximately half of the patients with signs and symptoms of heart failure have a left ventricular ejection fraction that is not markedly abnormal. Despite the historically initial surprise, heightened risks for heart failure specific major adverse events occur across the broad range of ejection fraction, including normal. The recognition of the magnitude of the problem of heart failure with preserved ejection fraction in the past 20 years has spurred an explosion of clinical investigation and growing intensity of informative outcome trials. This article addresses the historic development of this component of the heart failure syndrome, including the epidemiology, pathophysiology, and existing and planned therapeutic studies. Looking forward, more specific phenotyping and even genotyping of subpopulations should lead to improvements in outcomes from future trials.

Diuretic Resistance in Heart Failure

PURPOSE OF REVIEW

Diuretic resistance (DR) occurs along a spectrum of relative severity and contributes to worsening of acute heart failure (AHF) during an inpatient stay. This review gives an overview of mechanisms of DR with a focus on loop diuretics and summarizes the current literature regarding the prognostic value of diuretic efficiency and predictors of natriuretic response in AHF.

RECENT FINDINGS

The pharmacokinetics of diuretics are impaired in chronic heart failure, but little is known about mechanisms of DR in AHF. Almost all diuresis after administration of a loop diuretic dose occurs in the first few hours after administration and within-dose DR can develop. Recent studies suggest that DR at the level of the nephron may be more important than defects in diuretic delivery to the tubule. Because loop diuretics induce natriuresis, urine sodium (UNa) concentration may serve as a functional, physiological, and direct measure for diuretic responsiveness to a given loop diuretic dose. Identifying and targeting individuals with DR for more aggressive, tailored therapy represents an important opportunity to improve outcomes. A better understanding of the mechanistic underpinnings of DR in AHF is needed to identify additional biomarkers and guide future trials and therapies.

A Novel Fluorescent Clinical Method to Rapidly Quantify Plasma Volume

OBJECTIVES

To determine the performance of a rapid fluorescent indicator technique for measuring plasma volume (PV).

METHODS

This was an open-label, observational evaluation of a two-component intravenous visible fluorescent dye technique to rapidly measure PV in 16 healthy subjects and 16 subjects with chronic kidney disease (8 stage 3 and 8 stage 4 CKD), at 2 clinical research sites. The method consisted of a single intravenous injection of 12 mg of a large 150-kDa carboxy-methyl dextran conjugated to a fluorescent rhodamine-derived dye as the PV marker (PVM), and 35 mg of a small 5-kDa carboxy-methyl dextran conjugated to fluorescein, the renal clearance marker. Dye concentrations were quantified 15 min after the injections for initial PV measurements using the indicator-dilution principle. Additional samples were taken over 8 h to evaluate the stability of the PVM as a determinant of PV. Blood volumes (BV) were calculated based on PV and the subject's hematocrit. Pharmacokinetic parameters were calculated from the plasma concentration data taken over several days using noncompartmental methods (Phoenix WinNonlin®). Linear correlation and Bland-Altman plots were used to compare visible fluorescent injectate-measured PV compared to Nadler's formula for estimating PV. Finally, 8 healthy subjects received 350 mL infusion of a 5% albumin solution in normal saline over 30 min and a repeat PV determination was then carried out.

RESULTS

PV and BV varied according to weight and body surface area, with PV ranging from 2,115 to 6,234 mL and 28.6 to 41.9 mL/kg when weight adjusted. Both parameters were stable for > 6 h with repeated plasma measurements of the PVM. There was no difference between healthy subjects and CKD subjects. Overall, there was general agreement with Nadler's estimation formula for the mean PV in subjects. A 24-h repeat dose measurement in 8 healthy subjects showed PV variability of 98 ± 121 mL (mean = 3.8%). Additionally, following an intravenous bolus of 350 mL of a 5% albumin solution in normal saline in 8 healthy subjects, the mean (SD) measured increase in PV was 356 (±50.0) mL post-infusion. There were no serious adverse events reported during the study.

CONCLUSIONS

This minimally invasive fluorescent dye approach safely allowed for rapid, accurate, and reproducible determination of PV, BV, and dynamic monitoring of changes following fluid administration.