Inferior Vena Cava and Hemodynamic Congestion

Blood Volume Analysis and Cardiorenal Syndrome: From Bench to Bedside

BACKGROUND

This review delves into the intricate landscape of cardiorenal syndrome (CRS) and highlights the pivotal role of blood volume analysis (BVA) in improving patient care and outcomes.

SUMMARY

BVA offers a direct and highly accurate quantification of intravascular volume, red blood cell volume, and plasma volume, complete with patient-specific norms. This diagnostic tool enhances the precision of diuretic and red cell therapies, significantly elevating the effectiveness of conventional care.

KEY MESSAGES

Our objectives encompass a comprehensive understanding of how BVA informs the evaluation and treatment of CRS, including its subtypes, pathophysiology, and clinical significance. We delve into BVA principles, techniques, and measurements, elucidating its diagnostic potential and advantages compared to commonly used surrogate measures. We dissect the clinical relevance of BVA in various CRS scenarios, emphasizing its unique contributions to each subtype. By assessing the tangible impact of BVA on patient outcomes through meticulous analysis of relevant clinical studies, we unveil its potential to enhance health outcomes and optimize resource utilization. Acknowledging the challenges and limitations associated with BVA's clinical implementation, we underscore the importance of multidisciplinary collaboration among cardiologists, nephrologists, and other clinicians. Finally, we identify research gaps and propose future directions for BVA and CRS, contributing to ongoing advancements in this field and patients affected by this complicated clinical syndrome.

Echocardiography for Volume Assessment in Acute Myocardial Infarction

Background Errors caused by improper volume estimation increase acute mortality rates in acute myocardial infarction (AMI). We aimed to determine volume status in AMI patients using echocardiography and to correlate the findings with clinical outcomes. Methods This cross-sectional, single-center study was performed at a tertiary care center in India between August 2017 and September 2020 involving AMI patients. We performed echocardiography for all patients. Parameters such as left ventricle (LV) and atrium size, LV end-diastolic pressure, inferior vena cava (IVC) size and size variation, velocity stroke volume, and velocity time integral variation were measured. B-lines were recorded by scanning 32 regions on the anterior chest in the supine position using cardiac probes of echocardiography. Results A total of 184 patients were enrolled in the study with male predominance (82.1%). The mean age of patients was 58.2 ± 10.7 years. Dilated (>2.1 cm) and collapsible (<50%) IVC, and B-lines were significantly associated with heart failure (HF) (p<0.001; r=0.87 and p<0.001; r=0.74, respectively). The area under receiver operating characteristics (AUROC) curve to diagnose HF at a cut-off value of >10 for B-lines was 0.897 (0.842-0.951). AUROC curve for IVC size in diagnosing hypovolemia was 0.063 (0.000-0.130). Conclusions Volume status based on IVC size and B-lines detected by echocardiography has a strong prognostic value in AMI patients and should be included in the routine assessment of these patients.

Associations among preoperative transthoracic echocardiography variables and cerebral near-infrared spectroscopy values at baseline before anesthesia in patients undergoing cardiac surgery: a retrospective observational study

Cerebral tissue oximetry with near-infrared spectroscopy (NIRS) is used to monitor cerebral oxygenation during cardiac surgery. To date, reduced baseline cerebral NIRS values have been attributed to reduced cerebral blood flow primarily based on a significant positive correlation between left ventricular ejection fraction (LVEF) and baseline rSO₂ measured with the INVOS 5100C oximeter. Reportedly, however, rSO₂, but not StO₂ measured with the FORESIGHT Elite oximeter, correlated with LVEF. We, thus, investigated associations among baseline NIRS values measured with three different oximeters before anesthesia for cardiac surgery and preoperative transthoracic echocardiography (TTE) variables, including LVEF, to examine whether there are inter-device differences in associations among baseline NIRS values and TTE variables. Using Spearman's correlation coefficient, we retrospectively investigated associations among 15 preoperative TTE variables, including LVEF, and baseline NIRS values, including rSO₂, StO₂, and TOI with the NIRO-200NX oximeter in 1346, 515, and 301 patients, respectively. Only rSO₂ (p < 0.00001), but not TOI or StO₂ (p > 0.05), positively correlated with LVEF. On the other hand, baseline rSO₂, TOI, and StO₂ consistently, negatively correlated with the left atrial diameter index (LADI), early diastolic transmitral flow velocity (E), E-to-early diastolic mitral annular velocity ratio (E/e'), estimated right ventricular systolic pressure (eRVP), and inferior vena cava diameter index (IVCDI) (p < 0.0005 to p < 0.00001). Because all of these five TTE variables could be positively associated with right as well as left ventricular filling pressure, our results indicated that reduced baseline NIRS values were consistently associated not with reduced LVEF but with TTE findings indicative of elevated biventricular filling pressure. Our data suggest that regional venous congestion greatly contributes to reduced baseline NIRS values in patients undergoing cardiac surgery.

Systemic ventricular function in Fontan patients at rest and after exercise at altitude

OBJECTIVE

Physical activity at high altitude is expected to pose risks for patients with Fontan circulation and to impair systemic ventricular function. This study aims to determine the effect of high-altitude hypoxia on ventricular function in Fontan patients at rest and after exercise. We hypothesize that systemic ventricular function deteriorates under hypoxic conditions in Fontan patients.

METHODS

In this prospective study, 21 Fontan patients (NYHA class I-II) and 21 age-, gender- and body mass index-matched healthy controls were enrolled (median age 17.9 and 16.9 years). Transthoracic echocardiography was performed at rest, after peak (PE) and after continuous exercise (CE) in normoxia and hypoxia at simulated altitude (2,500 m above sea level). The effect of hypoxia on echocardiographic parameters was quantified by linear mixed-effects models and the difference between normoxia and hypoxia (Δ= hypoxia-normoxia).

RESULTS

At rest, cardiac output (CO) estimated by outflow tract velocity time integral × heart rate and annular plane systolic excursion (APSE) were lower in hypoxia compared to normoxia in Fontan patients (CO: Δ = -12.0%, n.s.; APSE: Δ = -9.6%, p < 0.001), an increase was observed in controls (CO: Δ = 8.5%, n.s.; APSE: Δ = 2.5%, n.s.). Other parameters of systolic and diastolic function did not show relevant changes. After exercise under hypoxic conditions, Fontan patients did not show relevant deterioration of systolic function compared to normoxia. Late, active diastolic filling reflected by A-wave velocity remained unchanged in Fontan patients, but increased in controls. Under hypoxic conditions, CO and workload were higher after CE than PE in Fontan patients (CO: PE Δ = 1,530 vs. CE 1630), whereas controls showed higher work load and CO estimates after PE than CE as expected (CO: PE Δ = 2,302 vs. CE 2149).

CONCLUSION

Fontan patients clinically tolerated short-term altitude exposure up to two hours and exercise and showed no consistent deterioration of systolic systemic ventricular function, but parameters of myocardial contractility, heart rate and cardiac output did not increase as observed in controls. This is likely to be multifactorial and may include intrinsic cardiac dysfunction as well as preload inadequacy and the lack of augmented atrial contraction. CE may be better tolerated than PE.

Fluid Removal With Ultrasound Guided Protocol Improves the Efficacy and Safety of Dehydration in Post-Resuscitated Critically Ill Patients: A Quasi-Experimental, Before and After Study

Fluid overload is associated with increased morbidity and mortality in critically ill patients. However, researches rarely study the precise start or end point of fluid removal and no protocol was developed to control the fluid removal process. We hypothesized that individualized fluid removal with ultrasound-guided protocol could improve the efficacy and safety of fluid removal in post-resuscitated critically ill patients. A quasi-experimental, before and after trial was conducted to identify the benefits of ultrasound-guided fluid removal. Fluid removal was performed either following the doctor's experience in Control group, or abiding the ultrasound guided protocol in Ultrasound group. The study end points were the start time, end time, length of fluid removal, and the complications related to fluid removal. A total of 85 subjects were finally analyzed in this study. The fluid removal was started earlier, completed quicker and ended earlier (21.0 ± 14.6 h vs. 35.1 ± 26.5 h, 49.8 ± 32.6 vs. 93.0 ± 42.8 h, 69.0 ± 32.2 h vs. 126.4 ± 52.5 h, P < 0.05) in Ultrasound group than in Control. The subjects had more daily negative fluid balance and urine output (-990.4 ± 636.1 mL vs. -723.6 ± 549.5 mL, 2425.8 ± 886.7 mL vs. 1560.7 ± 1125.3 mL, P < 0.05) in Ultrasound group. The time of lung B-lines to reduce to zero was shorter and B-line at the end point was less (49.5 ± 36.6 h vs. 75.6 ± 58.8 h, 0[1] vs. 0[0], P < 0.05) in Ultrasound group. The length of intensive care unit stay in shock subgroup had a tendency to shorten (96.1 ± 61.5 h vs. 174.6 ± 132.0 h, P > 0.05) in Ultrasound group. We concluded that fluid removal with individualized ultrasound-guided protocol improves the efficacy and safety of dehydration in critically ill patients.

Heart Failure Outcomes With Volume-Guided Management

OBJECTIVES

This study performed a retrospective outcome analyses of a large cohort of mixed ejection fraction patients admitted for acute heart failure (HF), whose inpatient care was guided by individual quantitative blood volume analysis (BVA) results.

BACKGROUND

Decongestion strategies in patients hospitalized for HF are based on clinical assessment of volume and have not integrated a quantitative intravascular volume metric.

METHODS

Propensity score control matching analysis was performed in 245 consecutive HF admissions to a community hospital (September 2007 to April 2014; 78 ± 10 years of age; 50% with HF with reduced ejection fraction [HFrEF]; and 30% with Stage 4 chronic kidney disease). Total blood volume (TBV), red blood cell volume (RBCV), and plasma volume (PV) were measured at admission by using iodine-131-labeled albumin indicator-dilution technique. Decongestion strategy targeted a TBV threshold of 6% to 8% above patient-specific normative values. Anemia was treated based on cause. Hematocrit (Hct) measurements were monitored to assess effectiveness of interventions. Control subjects derived from Centers for Medicare and Medicaid Services data were matched 10:1 for demographics, comorbidity, and year of treatment.

RESULTS

Although 66% of subjects had PV expansion, only 37% were hypervolemic (TBV >10% excess). True anemia (RBCV ≥10% deficit) was present in 62% of subjects. Treatment of true anemia without hypervolemia resulted in a rise in peripheral Hct of 2.7 ± 2.9% (p < 0.001), and diuretic treatment of hypervolemia in cases without anemia caused a 4.5 ± 3.9% (p < 0.001) increase in peripheral Hct at 11.3 ± 7.5 days after admission. Subjects had lower 30-day rates of readmission (12.2% vs. 27.7%, respectively; p < 0.001), of 30-day mortality (2.0% vs. 11.1%, respectively; p < 0.001), and of 365-day mortality (4.9% vs. 35.5%, respectively; p < 0.001) but longer lengths of stay (7.3 vs. 5.6 days, respectively; p < 0.001) than control subjects.

CONCLUSIONS

Retrospective outcomes using volume-guided HF therapy versus propensity-matched controls support the benefit of BVA in guiding volume management and reducing death and rehospitalization due to HF.

Influence of the Respiratory Cycle on Caudal Vena Cava Diameter Measured by Sonography in Healthy Foals: A Pilot Study

Background

Intravascular volume assessment in foals is challenging. In humans, intravascular volume status is estimated by the caudal vena cava (CVC) collapsibility index (CVC‐CI) defined as (CVC diameter at maximum expiration [CVC_max] – CVC diameter at minimal inspiration [CVC_min])/CVC_max × 100%.

Hypothesis/Objectives

To determine whether the CVC could be sonographically measured in healthy foals, determine differences in CVC_max and CVC_min, and calculate inter‐ and intrarater variability between 2 examiners. We hypothesized that the CVC could be measured sonographically at the subxiphoid view and that there would be a difference between CVC_max and CVC_min values.

Animals

Sixty privately owned foals <1‐month‐old.

Methods

Prospective study. A longitudinal subxiphoid sonographic window in standing foals was used. The CVC_max and CVC_min were analyzed by a linear mixed effect model. Inter‐rater agreement and intrarater variability were expressed by Bland‐Altman and intraclass correlation coefficients, respectively.

Results

Measurements were attained from 58 of 60 foals with mean age of 15 ± 7.9 days and mean weight of 75.7 ± 17.7 kg. The CVC_max was significantly different from CVC_min (D = 0.515, SE = 0.031, P < 0.001). Inter‐rater agreement of the CVC‐CI differed by an average of −0.9% (95% limits of agreement, −12.5 to +10.7%). Intrarater variability of CVC_max was 0.540 and 0.545, of CVC_min was 0.550 and 0.594, and of CVC‐CI was 0.894 and 0.853 for observers 1 and 2, respectively.

Conclusions and Clinical Importance

These results indicate it is possible to reliably measure the CVC sonographically in healthy foals, and the CVC‐CI may prove useful in assessing the intravascular volume status in hypovolemic foals.

Involvement of systemic venous congestion in heart failure

Systemic venous congestion has gained significant importance in the interpretation of the pathophysiology of acute heart failure, especially in the development of renal function impairment during exacerbations. In this study, we review the concept, clinical characterisation and identification of venous congestion. We update current knowledge on its importance in the pathophysiology of acute heart failure and its involvement in the prognosis. We pay special attention to the relationship between abdominal congestion, the pulmonary interstitium as filtering membrane, inflammatory phenomena and renal function impairment in acute heart failure. Lastly, we review decongestion as a new therapeutic objective and the measures available for its assessment.

An Admission-to-Discharge BNP Increase Is a Predictor of Six-Month All-Cause Death in ADHF Patients: Inferences from Multivariate Analysis Including Admission BNP and Various Clinical Measures of Congestion

BACKGROUND

According to some authors, a single isolated measurement of serum B-type natriuretic peptide (BNP) executed on hospital admission would not be a sufficiently accurate method to predict the outcome of patients with acute decompensated heart failure (ADHF).

AIMS

To verify this assumption, a retrospective study was conducted on patients hospitalized for ADHF. Our main objective was to ascertain whether there was any difference in midterm mortality among patients with increasing BNP at discharge as compared with those with decreasing BNP at discharge.

METHODS

Medical records were examined so as to make a partition of the ADHF patient population into two groups, the former characterized by a rise in BNP during hospitalization, and the latter exhibiting a decrease in BNP in the measurement taken at hospital discharge.

RESULTS

177 patients were enrolled in a retrospective study. Among them, 53 patients (30%) had increased BNP at the time of discharge, whereas 124 (70%) showed decreases in serum BNP during their hospital stay. The group with patients who exhibited BNP increases at the time of discharge had a higher degree of congestion evident in the higher frequency of persistent jugular venous distention and persistent orthopnea at discharge. Moreover, patients with increased BNP at the time of discharge had a lower reduction in inferior vena cava maximum diameter (1.58 ± 2.2 mm vs. 6.32 ± 1.82 mm; p (one-way ANOVA) = 0.001). In contrast, there was no significant difference in weight loss when patients with increased BNP at discharge were compared with those with no such increase. A total of 14 patients (7.9%) died during the six-month follow-up period. Multivariable Cox proportional-hazards regression analysis revealed that a BNP increase at the time of discharge was an independent predictor of six-month all-cause mortality after adjustment for persistent jugular venous distention, persistent orthopnea, reduction in inferior vena cava maximum diameter at discharge, weight loss, serum urea, systolic blood pressure at admission, and BNP at admission (hazard ratio = 30.5424; 95% CI: 1.7409-535.8294, p = 0.0199).

CONCLUSIONS

Among patients with a history of ADHF, more elevated BNP levels at the time of discharge from the hospital compared with those detected at admission identify a patient subset with a higher grade of congestion and higher six-month mortality.

Noninvasive Assessment of Pulmonary Artery Pressure in Patients with Extracardiac Conduit Total Cavopulmonary Connection

To assess quantitative measurement of mean pulmonary artery pressure (PAP) in extracardiac total cavopulmonary connection (TCPC) patients by noninvasive echocardiographic inferior vena cava collapsibility index (IVC-CI) and also correlation between the peripheral vein pressure and mean PAP. In 19 TCPC patients with at least 1-year follow-up after completion of TCPC, complete echocardiography including IVC-CI was recorded. All patients underwent cardiac catheterization for mean PAP pressure, peripheral vein pressure (PVP) and contrast study. Different cutoff points of mean PAP were analyzed, and based on the highest cutoff point, patients were categorized into two groups: mean PAP < 17 mmHg (acceptable) and > = 17 mmHg (high) for comparison analysis. Between 2006 and 2015, from 43 patients who had undergone TCPC, nineteen patients with a mean age 12.9 ± 6.6 years and mean follow-up time of 3.4 ± 1.9 years were included in this study. Mean PAP was 14.6 ± 3.97 (range 8-22 mmHg). Thirteen (68 %) patients had PAP < 17 mmHg. No significant statistical difference was detected with respect to age, sex, type of congenital heart disease and fenestration between these two groups. But, right ventricular dominancy was more prevalent in the high PAP group (50 % vs. 7.7 % P value 0.03). IVC-CI had a correlation with mean PAP (r 0.67, P < 0.001). IVC-CI < 21.8 % can predict PAP > = 17 mmHg with 83 % sensitivity and 100 % specificity. Regression analysis proposed an equation for PAP measurement: PAP (mmHg) = 20.2097-0.1796 × (IVC-CI), (r2 = 0.56). Peripheral vein pressure measurement also showed a good correlation with mean PAP and may be used to estimate PAP with the following equation: PAP (mmHg) = 0. 8675 × PVP, (r 0.90, P < 0.0001). In conclusion, IVC-CI as noninvasive and peripheral vein pressure measurement as a minimal invasive method may be useful for quantitative estimation of PAP in patients with extracardiac TCPC.

Change of Serum BNP Between Admission and Discharge After Acute Decompensated Heart Failure Is a Better Predictor of 6-Month All-Cause Mortality Than the Single BNP Value Determined at Admission

Background

B-type natriuretic peptide (BNP) is regarded as a reliable predictor of outcome in patients with acute decompensated heart failure (ADHF). However, according to some scholars, a single isolated measurement of serum BNP at the time of hospital admission would not be sufficient to provide reliable prognostic information.

Methods

A retrospective study was carried out on patients hospitalized for ADHF, who had then undergone follow-up of at least 6 months, in order to see if there was any difference in midterm mortality among patients with rising BNP at discharge as compared to those with decreasing BNP at discharge. Medical records had to be carefully examined to divide the case records into two groups, the former characterized by an increase in BNP during hospitalization, and the latter showing a decrease in BNP from the time of admission to the time of discharge.

Results

Ultimately, 177 patients were enrolled in a retrospective study. Among them, 53 patients (29.94%) had increased BNPs at the time of discharge relative to admission, whereas 124 (70.06%) exhibited decreases in serum BNP during their hospital stay. The group with patients who exhibited BNP increases at the time of discharge had higher degree of congestion evident in the higher frequency of persistent jugular venous distention (odds ratio: 3.72; P = 0.0001) and persistent orthopnea at discharge (odds ratio: 2.93; P = 0.0016). Moreover, patients with increased BNP at the time of discharge had a lower reduction in inferior vena cava maximum diameter (1.58 ± 2.2 mm vs. 6.32 ± 1.82 mm; P = 0.001 (one-way ANOVA)). In contrast, there was no significant difference in weight loss when patients with increased BNP at discharge were compared to those with no such increase. A total of 14 patients (7.9%) died during the 6-month follow-up period. Cox proportional hazard analysis revealed that BNP increase at the time of discharge was an independent predictor of 6-month all-cause mortality after adjustment for age, sodium at discharge, creatinine at discharge and New York Heart Association (NYHA) class at discharge (hazard ratio 34.49; 95% confidence intervals: 4.55 - 261.06; P = 0.001).

Conclusions

Among patients with recent ADHF, increased BNP at the time of discharge from the hospital entailed a higher grade of congestion and higher 6-month mortality.

Estimating Right Atrial Pressure Using Ultrasounds: An Old Issue Revisited With New Methods

Knowledge of the right atrial pressure (RAP) values is critical to ascertain the existence of a state of hemodynamic congestion, irrespective of the possible presence of signs and symptoms of clinical congestion and cardiac overload that can be lacking in some conditions of concealed or clinically misleading cardiac decompensation. In addition, a more reliable estimate of RAP would make it possible to determine more accurately also the systolic pulmonary arterial pressure with the only echocardiographic methods. The authors briefly illustrate some of the criteria that have been implemented to obtain a non-invasive RAP estimate, some of which have been approved by current guidelines and others are still awaiting official endorsement from the Scientific Societies of Cardiology. There is a representation of the sometimes opposing views of researchers who have studied the problem, and the prospects for development of new diagnostic criteria are outlined, in particular those derived from the matched use of two- and three-dimensional echocardiographic parameters.