Abstract
Background and Aim:
Assessment of volume status plays a critical role in the therapeutic management of patients with heart failure (HF) and chronic kidney disease (CKD). Echocardiography and bioelectrical impedance analysis (BIA) are two noninvasive methods frequently used to evaluate body fluid distribution. This study aimed to investigate the correlation between parameters obtained from these two methods in hospitalized patients.
Methods:
In this cross-sectional study, 40 patients with concurrent HF and CKD admitted to a tertiary hospital were evaluated. Demographic data, medical history, medication usage, and echocardiographic and BIA parameters were collected. Associations between variables were analyzed using correlation and regression models, with statistical significance defined as P < 0.05.
Results:
A significant correlation was found between inferior vena cava diameter and total body water (TBW) (ρ = 0.332, P = 0.037). Reduced left ventricular ejection fraction (EF) was associated with increased left atrial volume (LAV) and LAV index (P < 0.001). Among echocardiographic indices, right ventricular diameter showed strong positive correlations with TBW (ρ = 0.610, P < 0.001), intracellular water (ρ = 0.597, P < 0.001), and extracellular water (ECW) (ρ = 0.571, P < 0.001). E-wave velocity correlated positively with ECW ratio (ρ = 0.434, P = 0.005) and negatively with segmental phase angle (ρ = –0.398, P = 0.011). Patients with pulmonary congestion on computed tomography had lower segmental phase angle values (P = 0.027), and those with pleural effusion showed higher ECW ratios (P = 0.047). However, no significant correlations were observed between systolic pulmonary artery pressure (SPAP), tricuspid regurgitation gradient, and BIA-derived indices. Among laboratory markers, serum creatinine was significantly associated with the body cell mass index (P = 0.049), whereas NT-proBNP and CA125 were not. Clinically, patients with lower limb edema had higher ECW ratios (P = 0.045), and those with pulmonary rales exhibited lower stroke volume index (SVI) values (P = 0.027).
Conclusion:
The findings suggest that echocardiography and BIA provide complementary insights into volume assessment in patients with HF and CKD. Significant correlations between selected parameters indicate that combining these modalities may enhance diagnostic accuracy. However, further large-scale studies are warranted to validate the clinical utility of these findings.
Keywords: Bioelectrical impedance analysis, chronic kidney disease, echocardiography, heart failure, volume status assessment
INTRODUCTION
Accurate clinical assessment of fluid status in patients with heart failure (HF) and chronic kidney disease (CKD) remains challenging and carries substantial risks. These range from hypovolemia – resulting in intradialytic hypotension and loss of residual renal function – to chronic fluid overload, leading to excessive interdialytic weight gain, hypertension, left ventricular hypertrophy, and edema.[1] Traditional clinical approaches, such as physical examination, weight monitoring, and fluid removal guided by symptomatic hypotension (“probing dry weight”), are often imprecise, time-consuming, and poorly reproducible.[2]
Although gold-standard methods like isotopic dilution offer high accuracy, their cost and complexity limit their routine clinical use.[3] Consequently, bioelectrical impedance analysis (BIA) has gained traction as a non-invasive, bedside technique to assess fluid distribution and body composition.[4] Techniques such as single- and multifrequency BIA provide estimates of fluid compartments, whereas resistance and reactance are used for more refined modeling.[5]
Echocardiography also offers valuable insights into volume status by evaluating cardiac chamber dimensions, function, and dynamic changes.[5,6] For example, an enlarged inferior vena cava (IVC) with reduced respiratory variation suggests volume overload, whereas a collapsed IVC with pronounced variability indicates hypovolemia.[7] Doppler measurements further enhance the assessment by evaluating blood flow in major vessels.[7]
Despite several studies comparing BIA and echocardiography in HF and CKD, there remains no consensus on the most reliable outcome parameters, and reported findings are often inconsistent.[7,8] Given the complexity of cardiorenal syndromes, identifying accurate, reproducible, and clinically relevant markers is critical.[9] This study seeks to address current gaps by providing an updated analysis of the comparative utility of BIA and echocardiography in evaluating fluid status in patients with HF and CKD.
METHODS
Study design and population
This was a prospective observational cohort study designed to evaluate the correlation between echocardiographic and BIA parameters in assessing volume status among patients with HF and CKD. The study was conducted in a non-interventional format, aiming to compare the diagnostic performance of two non-invasive methods for fluid assessment in a hospitalized patient population.
The study population comprised patients admitted to Imam Hossein Hospital with a confirmed diagnosis of both chronic HF and CKD during the year 2023–2024. Patient eligibility was determined based on clinical criteria. Inclusion criteria were: age ≥18 years, confirmed diagnosis of HF with left ventricular ejection fraction (EF) <50%, and CKD with an estimated glomerular filtration rate (sGFR) below 60 mL/min/1.73 m2, as calculated using the Cockcroft–Gault formula. Participants were also required to provide written informed consent. Exclusion criteria included inability or unwillingness to provide informed consent, severe cognitive impairment or psychiatric illness interfering with participation, hemodynamic instability requiring intensive care admission, history of cardiac surgery or heart transplantation, ongoing dialysis treatment, pregnancy or breastfeeding, and the presence of implanted electronic devices such as pacemakers or defibrillators that could interfere with BIA measurements.
Measurement
Upon enrollment, comprehensive data were collected from each of 40 participants, including demographic and clinical characteristics (age, sex, comorbidities such as diabetes, hypertension, or ischemic heart disease), and current medications (name, dose, and frequency). Echocardiographic assessments were performed by a certified cardiologist specialized in echocardiography. Key variables included EF, right ventricular systolic velocity (S’), left ventricular end-diastolic and end-systolic diameters, left atrial diameter, and stroke volume index (SVI). BIA measurements were conducted at the bedside using a multifrequency device to quantify total body water (TBW), extracellular water (ECW), intracellular water (ICW), body cell mass index (BCI), and hydration status.
Definition of terms
HF is a condition, in which the heart cannot pump blood effectively, leading to reduced cardiac output and symptoms such as fatigue, dyspnea, and fluid retention; it is defined in this study as an EF below 50%.[10] CKD involves a gradual decline in kidney function, typically defined as an eGFR below 60 mL/min/1.73 m2, and is classified into five stages based on severity.[11] Cardiorenal syndrome (CRS) is defined as a disorder of the heart and kidneys in which acute or chronic dysfunction of one organ may induce dysfunction of the other,[12] more recently, CRS has been redefined as a progressive combination of both cardiac and renal dysfunction, with additional clinical qualifiers such as valve status and volume state.[13] BIA is a non-invasive technique that measures tissue resistance to a low-level electrical current to estimate body composition and fluid status, including TBW, ECW, and ICW.[14] Echocardiography is a safe, ultrasound-based imaging method used to evaluate heart structure, function, and blood flow in real time, supporting the diagnosis and management of various cardiac conditions.[15]
Statistical analysis
Data were analyzed using IBM SPSS Statistics (IBM Corp., Armonk, NY, USA) and R software (R Foundation for Statistical Computing, Vienna, Austria). Continuous variables were described using means and standard deviations (mean ± SD), and categorical variables were summarized as frequencies and percentages (n, %). Between-group comparisons for continuous variables were performed using independent t-tests or Mann–Whitney U tests, depending on data normality. Categorical variables were compared using the Chi-square test or Fisher’s exact test. Pearson or Spearman correlation coefficients were calculated to examine associations between echocardiographic and BIA indices. Multiple linear regression models were applied to identify predictors of discordance between the two methods. P < 0.05 was considered statistically significant in all analyses. The sample size was calculated based on data from a previous study by Dogrul RT et al., which reported a correlation coefficient of 0.4 between E-wave velocity and ECW in ESRD patients.[16] With α = 0.05 and power = 80%, the required sample size was determined to be 52 patients.
Ethical considerations
All participants received clear verbal and written information regarding the study’s objectives and procedures. Informed consent was obtained from all eligible individuals before inclusion. No additional costs were imposed on participants, and all expenses related to diagnostic assessments were covered by the study budget. The study involved no deviation from standard medical care, and patient confidentiality was strictly maintained. The research protocol was reviewed and approved by the Ethics Committee of Shahid Beheshti University of Medical Sciences under the code IR.SBMU.MSP.REC.1402.558.
RESULTS
Table 1 presents the demographic characteristics, medical history, and medication usage of the study participants. The mean age of the patients was 68 years (SD = 14), with an average weight of 89 kg (SD = 84) and a mean height of 168 cm (SD = 10). The majority of participants were male, comprising 75.0% (n = 30) of the sample, while females accounted for 25.0% (n = 10). In terms of past medical history, 50.0% (n = 20) of patients had congestive HF, 35.0% (n = 14) had hypertension, and 25.0% (n = 10) had ischemic heart disease. CKD and diabetes mellitus were each reported in 30.0% (n = 12) of participants. Other comorbidities included chronic obstructive pulmonary disease (12.5%), coronary artery bypass grafting (17.5%), atrial fibrillation (7.5%), stroke (5.0%), and hyperlipidemia (7.5%). Regarding drug history, the most frequently used medications were aspirin (57.5%), atorvastatin (52.5%), and furosemide (37.5%). Other commonly prescribed drugs included pantoprazole (25.0%), bisoprolol (20.0%), insulin (15.0%), and allopurinol (7.5%). A smaller proportion of participants were taking clopidogrel, apixaban, losartan, or other medications, each reported in <15% of the cohort.
Table 1.
Demographic characteristics, medical history, and medication usage of the study participants
| Variable | n (%) |
|---|---|
| Demographics | |
| Age (years), mean±SD | 68±14 |
| Weight (kg), mean±SD | 89±84 |
| Height (cm), mean±SD | 168±10 |
| Gender | |
| Male | 30 (75.0) |
| Female | 10 (25.0) |
| Past medical history | |
| Congestive HF | 20 (50.0) |
| Hypertension | 14 (35.0) |
| Ischemic heart disease | 10 (25.0) |
| CKD | 12 (30.0) |
| Chronic obstructive pulmonary disease | 5 (12.5) |
| Cardiac cirrhosis | 1 (2.5) |
| Diabetes mellitus | 12 (30.0) |
| Coronary artery bypass grafting | 7 (17.5) |
| Benign prostatic hyperplasia | 1 (2.5) |
| Atrial fibrillation | 3 (7.5) |
| DVT/PTE | 2 (5.0) |
| Anemia | 1 (2.5) |
| Cerebrovascular accident (stroke) | 2 (5.0) |
| Hyperlipidemia | 3 (7.5) |
| Coronary artery disease | 1 (2.5) |
| Medication classes | |
| Diuretics | 18 (45.0) |
| Antihypertensives (including β-blockers, ACE inhibitors/ARBs, calcium channel blockers) | 16 (40.0) |
| Antiplatelets/anticoagulants | 32 (80.0) |
| Lipid-lowering agents (statins) | 21 (52.5) |
| Antidiabetic agents (oral/injectable) | 9 (22.5) |
| Gastroprotective agents (e.g., proton pump inhibitors) | 10 (25.0) |
| Other medications (e.g., uric acid–lowering, respiratory, CNS) | 7 (17.5) |
ACE: Angiotensin converting enzyme, ARB: Angiotensin receptor blocker, DVT/PTE: Deep vein thrombosis/pulmonary thromboembolism
Table 2 presents the association between clinical findings and chest CT imaging results with bioelectrical impedance parameters. Among the clinical signs, patients with lower limb edema had a significantly higher ECW ratio compared to those without edema (0.405 vs. 0.381, P = 0.045). No other impedance parameters showed statistically significant differences in this group. Regarding chest computed tomography (CT) findings, patients with pulmonary congestion demonstrated significantly lower segmental phase angle values compared to those without congestion (5.0 vs. 6.9, P = 0.027). Additionally, pleural effusion was associated with a lower segmental phase angle (4.7 vs. 7.5, P = 0.004) and a higher ECW ratio (0.407 vs. 0.392, P = 0.047). Other imaging findings, including cardiomegaly, did not show significant associations with BIA indices. Summary of findings: The correlation coefficients and statistical tests suggest that among BIA parameters, the ECW ratio and Segmental Phase Angle are the most sensitive to clinical signs of fluid overload, such as lower limb edema, pulmonary congestion, and pleural effusion. These findings emphasize the potential utility of BIA for fluid status assessment in HF patients.
Table 2.
Association between clinical findings and chest computed tomography imaging results with bioelectrical impedance parameters
| Clinical finding/imaging result | TBW | ICW | ECW | BCI | TBW/FFM | Segmental phase angle | ECW ratio |
|---|---|---|---|---|---|---|---|
| JVP distention | |||||||
| Absent | 37.8±10.1 | 22.9±6.2 | 14.9±4.0 | 32.7±8.8 | 73.9±0.7 | 6.0±2.8 | 0.396±0.017 |
| Present | 45.7±15.1 | 27.0±9.1 | 18.6±6.3 | 38.4±13.2 | 74.1±0.8 | 5.0±2.2 | 0.407±0.025 |
| P | 0.153 | 0.260 | 0.083 | 0.285 | 0.394 | 0.175 | 0.153 |
| Rales on lung auscultation | |||||||
| Absent | 34.9±12.9 | 21.2±8.0 | 13.7±4.9 | 30.4±11.5 | 73.5±0.4 | 5.2±1.6 | 0.395±0.021 |
| Present | 44.1±14.1 | 26.1±8.4 | 17.9±5.9 | 37.2±12.2 | 74.1±0.8 | 5.4±2.5 | 0.404±0.024 |
| P | 0.321 | 0.499 | 0.241 | 0.528 | 0.064 | 0.718 | 0.367 |
| Lower limb edema | |||||||
| Absent | 38.2±7.2 | 23.6±4.0 | 14.6±3.2 | 33.8±5.8 | 73.4±0.5 | 6.2±0.6 | 0.381±0.013 |
| Present | 43.6±14.5 | 25.8±8.7 | 17.7±6.0 | 36.8±12.5 | 74.1±0.8 | 5.3±2.5 | 0.405±0.023 |
| P | 0.488 | 0.700 | 0.342 | 0.739 | 0.080 | 0.136 | 0.045 |
| Wheezes on auscultation | |||||||
| Absent | 43.4±14.3 | 25.8±8.5 | 17.6±6.0 | 36.7±12.4 | 74.1±0.8 | 5.3±2.5 | 0.404±0.023 |
| Present | 38.0±10.0 | 23.5±5.7 | 14.5±4.2 | 33.6±8.3 | 73.4±0.2 | 6.0±0.4 | 0.381±0.011 |
| P | 0.620 | 0.901 | 0.495 | 0.951 | 0.162 | 0.264 | 0.106 |
| Reduced breath sounds on auscultation | |||||||
| Absent | 41.9±13.8 | 24.9±8.4 | 17.0±5.6 | 35.3±12.2 | 74.1±0.8 | 5.3±2.7 | 0.406±0.023 |
| Present | 46.3±14.8 | 27.7±8.3 | 18.6±6.6 | 39.7±11.9 | 74.0±0.8 | 5.5±1.4 | 0.397±0.024 |
| P | 0.515 | 0.413 | 0.750 | 0.388 | 0.844 | 0.282 | 0.289 |
| Chest CT: Pulmonary congestion | |||||||
| Absent | 48.0±15.3 | 29.1±8.8 | 18.9±6.6 | 41.7±12.7 | 73.9±0.7 | 6.9±3.2 | 0.391±0.017 |
| Present | 41.9±13.7 | 24.8±8.2 | 17.1±5.8 | 35.3±11.8 | 74.1±0.8 | 5.0±2.1 | 0.406±0.024 |
| P | 0.344 | 0.146 | 0.554 | 0.128 | 0.576 | 0.027 | 0.094 |
| Chest CT: Cardiomegaly | |||||||
| Absent | 43.5±18.3 | 26.1±10.9 | 17.4±7.5 | 37.4±15.5 | 73.9±0.8 | 6.1±3.0 | 0.400±0.020 |
| Present | 43.0±13.0 | 25.5±7.7 | 17.5±5.5 | 36.3±11.2 | 74.1±0.8 | 5.2±2.2 | 0.404±0.024 |
| P | 0.961 | 0.846 | 0.783 | 0.796 | 0.390 | 0.364 | 0.604 |
| Chest CT: Pleural effusion | |||||||
| Absent | 45.9±15.2 | 27.9±9.0 | 18.1±6.3 | 39.9±12.8 | 74.1±0.8 | 7.5±3.4 | 0.392±0.015 |
| Present | 42.2±13.8 | 24.9±8.2 | 17.2±5.8 | 35.4±11.9 | 74.0±0.8 | 4.7±1.5 | 0.407±0.024 |
| P | 0.492 | 0.281 | 0.779 | 0.267 | 0.938 | 0.004 | 0.047 |
Values are mean±SD. P values from group comparisons. TBW=Total body water, ICW; Intracellular water, ECW=Extracellular water, BCI=Body cell index, TBW/FFM=TBW/free fat mass ratio, ECW ratio=ECW ratio, JVP=Jugular venous pressure, SD=Standard deviation
Supplementary Table 1 highlights the significant associations between clinical or imaging findings and echocardiographic parameters. Patients with jugular venous pressure (JVP) distention exhibited significantly lower EF (19.4 vs. 31.9, P = 0.001), larger left ventricular diameters in both diastole (6.1 vs. 4.9 cm, P < 0.001) and systole (5.0 vs. 3.7 cm, P = 0.001), and greater left atrial diameter (4.32 vs. 3.72 cm, P = 0.005), along with increased left atrial volume (LAV) (89.7 vs. 62.6 mL, P = 0.002) and LAV index (LAVI) (60.73 vs. 39.06 mL/m2, P = 0.001). These patients also had elevated E-wave velocity (91.3 vs. 54.4 cm/s, P = 0.002), A-wave velocity (69.0 vs. 66.2 cm/s, P = 0.036), and E/A ratio (2.21 vs. 0.94, P < 0.001), as well as increased IVC diameter (2.2 vs. 1.8 cm, P = 0.003), right atrial volume (75.6 vs. 47.9 mL, P = 0.001), and slightly reduced right ventricular systolic motion (7.2 vs. 8.3 cm/s, P = 0.044). Presence of rales on lung auscultation was associated with lower stroke volume index (15.57 vs. 24.40 mL/m2, P = 0.027), higher IVC diameter (2.1 vs. 1.7 cm, P = 0.020), higher tricuspid regurgitation gradient (TRG) (42 vs. 28 mmHg, P = 0.024), and elevated E-wave velocity (84.9 vs. 28.6 cm/s, P = 0.008). Lower limb edema also correlated with lower stroke volume index (15.76 vs. 25.00 mL/m2, P = 0.025). Patients with wheezing showed significantly lower pulmonary artery systolic pressure (29 vs. 55 mmHg, P = 0.030), TRG (21 vs. 41 mmHg, P = 0.023), and E-wave velocity (18.1 vs. 82.5 cm/s, P = 0.035). Reduced breath sounds were associated with significantly higher A-wave velocity (75.8 vs. 43.6 cm/s, P = 0.015), E/A ratio (2.29 vs. 1.60, P = 0.043), and LAV (99.8 vs. 73.7 mL, P = 0.005). Among imaging findings, pulmonary congestion on CT was associated with increased systolic pulmonary artery pressure (56 vs. 46 mmHg, P = 0.039) and TRG (43 vs. 29 mmHg, P = 0.002). Hyperinflation on CT was linked to reduced left ventricular end-diastolic (29 vs. 55 mmHg, P = 0.003) and end-systolic (21 vs. 41 mmHg, P = 0.012) diameters, as well as lower E-wave velocity (18.1 vs. 82.5 cm/s, P = 0.009) and LAV (95.0 vs. 80.1 mL, P = 0.015). Cardiomegaly on CT was significantly associated with lower right ventricular transverse systolic pressure (11.4 vs. 14.9 mmHg, P = 0.019).
Supplementary Table 1.
Association between clinical and imaging findings with continuous echocardiographic parameters
| Condition | EF | LVEDD | LVESD | LAD | SVI | LAV | LAVI | Right ventricular function/right ventricular systolic motion | Right ventricular function/right ventricular transverse systolic pressure | Right ventricular diameter |
|---|---|---|---|---|---|---|---|---|---|---|
| JVP distention | ||||||||||
| Absent | 31.9±10.5 | 4.9±0.9 | 3.7±1.0 | 3.72±0.74 | 18.65±6.48 | 62.6±20.3 | 39.06±21.62 | 8.3±1.8 | 13.7±2.8 | 3.3±0.8 |
| Present | 19.4±9.2 | 6.1±0.8 | 5.0±0.9 | 4.32±0.55 | 15.39±5.21 | 101.8±32.3 | 60.73±21.43 | 7.2±1.7 | 11.4±5.3 | 3.6±0.7 |
| P | 0.001 | 0 | 0.001 | 0.005 | 0.04 | 0 | 0.001 | 0.044 | 0.047 | 0.159 |
| Rales on lung auscultation | ||||||||||
| Absent | 31.3±10.3 | 4.8±1.5 | 3.6±1.5 | 3.40±1.19 | 24.40±8.01 | 66.7±45.1 | 39.83±26.19 | 8.7±1.1 | 14.6±1.9 | 3.2±0.8 |
| Present | 22.6±11.1 | 5.9±0.9 | 4.7±1.1 | 4.21±0.56 | 15.57±4.87 | 91.6±32.6 | 55.23±23.15 | 7.5±1.8 | 11.9±4.9 | 3.6±0.7 |
| P | 0.101 | 0.099 | 0.095 | 0.124 | 0.027 | 0.104 | 0.114 | 0.073 | 0.14 | 0.469 |
| Lower limb edema | ||||||||||
| Absent | 26.7±12.6 | 5.3±1.3 | 4.2±1.5 | 3.93±1.01 | 25.00±8.19 | 66.0±33.4 | 38.63±21.66 | 8.1±0.8 | 13.3±1.5 | 3.6±1.0 |
| Present | 23.2±11.2 | 5.8±1.0 | 4.6±1.1 | 4.14±0.65 | 15.76±5.09 | 90.9±34.0 | 54.91±23.57 | 7.5±1.8 | 12.1±4.9 | 3.5±0.7 |
| P | 0.5 | 0.382 | 0.521 | 0.52 | 0.025 | 0.19 | 0.208 | 0.34 | 0.454 | 0.737 |
| Wheezes on auscultation | ||||||||||
| Absent | 23.6±11.5 | 5.8±1.0 | 4.5±1.1 | 4.14±0.65 | 16.03±5.61 | 88.8±33.9 | 53.57±23.63 | 7.5±1.8 | 12.0±4.8 | 3.6±0.7 |
| Present | 22.5±3.5 | 5.6±1.7 | 4.6±1.3 | 3.90±1.27 | 24.50±2.12 | 95.0±53.7 | 55.87±31.63 | 9.5±0.7 | 15.0±0.0 | 3.2±1.0 |
| P | 0.802 | 0.828 | 1 | 0.803 | 0.054 | 0.95 | 1 | 0.086 | 0.235 | 0.618 |
| Reduced breath sounds on auscultation | ||||||||||
| Absent | 25.7±11.9 | 5.6±1.1 | 4.3±1.1 | 4.06±0.75 | 16.61±5.88 | 85.0±37.9 | 51.39±25.51 | 7.7±1.9 | 11.9±4.9 | 3.4±0.7 |
| Present | 17.7±6.4 | 6.2±0.8 | 5.1±1.0 | 4.31±0.37 | 16.05±5.77 | 99.8±19.0 | 59.76±17.00 | 7.1±1.3 | 12.9±4.2 | 4.0±0.6 |
| P | 0.086 | 0.066 | 0.102 | 0.117 | 0.82 | 0.044 | 0.069 | 0.385 | 0.976 | 0.01 |
| Chest CT: Pulmonary congestion | ||||||||||
| Absent | 24.7±12.3 | 5.4±1.0 | 4.3±0.9 | 4.13±0.90 | 17.02±5.46 | 95.7±56.7 | 50.25±30.37 | 7.7±1.8 | 12.4±3.4 | 3.5±0.8 |
| Present | 23.2±11.1 | 5.8±1.0 | 4.6±1.2 | 4.13±0.62 | 16.31±5.94 | 87.4±27.0 | 54.55±22.07 | 7.6±1.8 | 12.1±5.0 | 3.6±0.7 |
| P | 0.745 | 0.257 | 0.498 | 0.747 | 0.624 | 0.71 | 0.335 | 0.825 | 0.905 | 0.878 |
| Chest CT: Cardiomegaly | ||||||||||
| Absent | 28.3±10.3 | 5.2±1.4 | 3.8±1.4 | 3.74±1.01 | 21.50±8.71 | 82.3±39.3 | 48.70±26.06 | 8.3±1.8 | 14.9±3.3 | 3.3±0.7 |
| Present | 22.1±11.2 | 5.9±0.8 | 4.7±1.0 | 4.24±0.50 | 14.99±3.66 | 91.0±33.0 | 55.14±23.06 | 7.4±1.7 | 11.4±4.8 | 3.6±0.7 |
| P | 0.108 | 0.064 | 0.086 | 0.053 | 0.075 | 0.527 | 0.382 | 0.076 | 0.019 | 0.261 |
| Chest CT: Pleural effusion | ||||||||||
| Absent | 29.8±10.2 | 5.4±1.2 | 4.2±1.2 | 4.06±0.92 | 18.80±7.31 | 83.7±54.6 | 46.68±32.16 | 7.8±1.8 | 12.9±3.0 | 3.6±0.9 |
| Present | 21.4±10.9 | 5.9±1.0 | 4.7±1.1 | 4.15±0.58 | 15.67±5.09 | 90.9±25.1 | 56.02±20.09 | 7.5±1.8 | 11.9±5.2 | 3.5±0.7 |
| P | ||||||||||
| Hyperinflation on CT | ||||||||||
| Absent | 23.6±11.5 | 5.8±1.0 | 4.5±1.1 | 4.14±0.65 | 16.03±5.61 | 88.8±33.9 | 53.57±23.63 | 7.5±1.8 | 12.0±4.8 | 3.6±0.7 |
| Present | 22.5±3.5 | 5.6±1.7 | 4.6±1.3 | 3.90±1.27 | 24.50±2.12 | 95.0±53.7 | 55.87±31.63 | 9.5±0.7 | 15.0±0.0 | 3.2±1.0 |
| P | 0.069 | 0.146 | 0.34 | 0.154 | 0.206 | 0.13 | 0.08 | 0.695 | 0.33 | 0.754 |
| JVP distention | ||||||||||
| Absent | 1.8±0.3 | 50±22 | 38±19 | 54.4±29.5 | 66.2±18.9 | 0.94±0.52 | 4.5±1.2 | 6.4±1.7 | 62.6±20.3 | 47.9±14.7 |
| Present | 2.2±0.4 | 56±13 | 41±11 | 91.3±33.5 | 69.0±95.4 | 2.21±0.81 | 4.2±1.3 | 6.1±1.5 | 89.7±30.7 | 75.6±33.3 |
| P | 0.003 | 0.111 | 0.129 | 0.002 | 0.036 | 0 | 0.488 | 0.675 | 0.002 | 0.001 |
| Rales on lung auscultation | ||||||||||
| Absent | 1.7±0.2 | 46±30 | 28±8 | 28.6±24.5 | 48.8±13.3 | 1.17±1.10 | 3.5±0.9 | 6.0±1.4 | 66.7±45.1 | 49.5±17.5 |
| Present | 2.1±0.4 | 55±14 | 42±13 | 84.9±33.0 | 70.3±81.3 | 1.84±0.91 | 4.3±1.3 | 6.2±1.6 | 82.5±28.8 | 68.5±32.0 |
| P | 0.02 | 0.175 | 0.024 | 0.008 | 0.478 | 0.149 | 0.109 | 0.635 | 0.207 | 0.162 |
| Lower limb edema | ||||||||||
| Absent | 1.9±0.3 | 41±17 | 33±12 | 59.0±24.0 | 51.7±14.7 | 1.23±0.95 | 4.2±1.1 | 6.3±1.6 | 66.0±33.4 | 61.3±21.4 |
| Present | 2.1±0.4 | 55±16 | 41±14 | 81.0±36.9 | 69.4±80.3 | 1.81±0.94 | 4.3±1.3 | 6.2±1.6 | 82.1±30.3 | 67.1±32.1 |
| P | 0.278 | 0.173 | 0.217 | 0.248 | 0.697 | 0.242 | 0.938 | 0.877 | 0.317 | 0.939 |
| Wheezes on auscultation | ||||||||||
| Absent | 2.1±0.4 | 55±15 | 41±13 | 82.5±34.1 | 69.0±79.1 | 1.77±0.93 | 4.3±1.3 | 6.2±1.6 | 80.1±29.7 | 67.6±31.7 |
| Present | 1.7±0.1 | 29±2 | 21±1 | 18.1±23.9 | 51.0±17.0 | 1.65±1.63 | 3.1±0.1 | 5.4±0.7 | 95.0±53.7 | 47.5±14.8 |
| P | 0.086 | 0.03 | 0.023 | 0.035 | 0.84 | 0.814 | 0.082 | 0.351 | 0.756 | 0.214 |
| Reduced breath sounds on auscultation | ||||||||||
| Absent | 2.1±0.4 | 52±17 | 39±14 | 78.0±36.8 | 75.8±87.4 | 1.60±0.96 | 4.5±1.2 | 6.2±1.7 | 73.7±31.0 | 63.4±33.8 |
| Present | 2.1±0.4 | 58±14 | 45±11 | 82.8±36.4 | 43.6±9.7 | 2.29±0.70 | 3.6±1.4 | 6.1±1.2 | 99.8±19.0 | 75.2±22.3 |
| P | 0.879 | 0.149 | 0.05 | 0.65 | 0.015 | 0.043 | 0.095 | 0.856 | 0.005 | 0.067 |
| Chest CT: Pulmonary congestion | ||||||||||
| Absent | 1.9±0.3 | 46±22 | 29±7 | 55.3±41.7 | 57.5±23.5 | 1.72±1.34 | 4.2±1.3 | 6.7±2.0 | 69.4±41.3 | 67.1±54.6 |
| Present | 2.1±0.4 | 56±14 | 43±14 | 85.3±32.9 | 70.9±86.4 | 1.78±0.83 | 4.3±1.3 | 6.1±1.5 | 83.8±27.1 | 66.5±23.6 |
| P | 0.333 | 0.039 | 0.002 | 0.07 | 0.912 | 0.671 | 0.709 | 0.611 | 0.236 | 0.155 |
| Chest CT: Cardiomegaly | ||||||||||
| Absent | 2.0±0.6 | 49±22 | 34±11 | 51.3±47.5 | 58.4±15.3 | 1.31±0.91 | 3.9±1.0 | 5.9±1.1 | 82.3±39.3 | 58.7±19.9 |
| Present | 2.1±0.4 | 55±14 | 42±14 | 87.4±28.5 | 71.1±88.4 | 1.91±0.92 | 4.3±1.3 | 6.3±1.7 | 80.5±28.1 | 68.9±33.8 |
| P | 0.397 | 0.206 | 0.064 | 0.024 | 0.49 | 0.089 | 0.307 | 0.527 | 0.987 | 0.437 |
| Chest CT: Pleural effusion | ||||||||||
| Absent | 2.1±0.6 | 42±11 | 32±7 | 53.5±30.3 | 61.6±21.7 | 1.26±1.09 | 4.8±1.5 | 6.7±1.4 | 60.9±35.7 | 67.2±49.3 |
| Present | 2.1±0.4 | 58±16 | 43±14 | 87.9±34.4 | 70.3±89.7 | 1.95±0.82 | 4.1±1.2 | 6.0±1.6 | 87.5±25.7 | 66.4±23.7 |
| P | ||||||||||
| Hyperinflation on CT | ||||||||||
| Absent | 2.1±0.4 | 55±15 | 41±13 | 82.5±34.1 | 69.0±79.1 | 1.77±0.93 | 4.3±1.3 | 6.2±1.6 | 80.1±29.7 | 67.6±31.7 |
| Present | 1.7±0.1 | 29±2 | 21±1 | 18.1±23.9 | 51.0±17.0 | 1.65±1.63 | 3.1±0.1 | 5.4±0.7 | 95.0±53.7 | 47.5±14.8 |
| P | 0.987 | 0.003 | 0.012 | 0.009 | 0.238 | 0.02 | 0.26 | 0.2 | 0.015 | 0.333 |
LVESD; Left ventricular end-systolic diameter, LVEDD=Left ventricular end-diastolic diameter, EF=Ejection fraction, LAVI=Left atrial volume index, LAV=Left atrial volume, SVI=Stroke volume index, LAD=Left atrial diameter, JVP=Jugular venous pressure, CT=Computed tomography
Table 3 summarizes the associations between BIA indices and echocardiographic parameters. The most robust correlations were observed between right ventricular diameter (RVD) and fluid-related BIA measures: TBW [ρ = 0.610, P < 0.001; Figure 1], ICW [ρ =0.597, P < 0.001; Figure 2], and ECW [ρ = 0.571, P < 0.001; Figure 3]. In addition, ECW ratio showed a significant positive correlation with E-wave velocity [ρ = 0.434, P = 0.005; Figure 4], whereas segmental phase angle demonstrated a significant negative correlation with E-wave velocity [ρ =–0.398, P = 0.011; Figure 5]. These findings highlight the potential utility of BIA-derived indices, particularly water distribution parameters and phase angle, in reflecting right ventricular structural changes and diastolic filling patterns. These univariate correlations suggest that TBW, ICW, ECW, and phase angle may serve as indicators of cardiac remodeling and diastolic function. To determine whether these associations persist independently of other variables, we performed a multivariate regression analysis. The results [Table 3] showed that RVD remained significantly associated with TBW (regression coefficient: 9.456, 95% CI: 0.986 to 17.927, P = 0.031), ICW (5.697, 95% CI: 0.452 to 10.941, P = 0.035), and ECW (3.986, 95% CI: 0.586 to 7.386, P = 0.025). Right atrial volume exhibited a significant inverse association with ECW (–0.233, 95% CI:–0.445 to–0.021, P = 0.034). Although segmental phase angle and ECW ratio showed borderline associations with certain echocardiographic parameters, these did not reach conventional levels of statistical significance (P > 0.05). No other variables in the model demonstrated statistically significant associations with impedance-derived fluid indices.
Table 3.
Linear regression analysis of echocardiographic parameters associated with bioelectrical impedance indices
| Name of variable | TBW | ICW | ECW | ||||||
|---|---|---|---|---|---|---|---|---|---|
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| Regression Coefficient (95% CI) | P | ρ (P) | Regression Coefficient (95% CI) | P | ρ (P) | Regression Coefficient (95% CI) | P | ρ (P) | |
| EF | −0.218 (−0.848 to 0.412) | 0.471 | –0.298 (0.062) | −0.186 (−0.576 to 0.204) | 0.324 | –0.290 (0.070) | −0.053 (−0.306 to 0.200) | 0.660 | –0.282 (0.078) |
| LVEDD | −0.518 (−17.718 to 16.681) | 0.949 | 0.376 (0.017) | −1.047 (−11.695 to 9.601) | 0.836 | 0.360 (0.023) | 0.332 (−6.572 to 7.236) | 0.919 | 0.382 (0.015) |
| LVESD | −3.862 (−16.804 to 9.079) | 0.532 | 0.317 (0.046) | −1.532 (−9.544 to 6.480) | 0.688 | 0.320 (0.044) | −2.158 (−7.353 to 3.037) | 0.388 | 0.303 (0.058) |
| LAD | 4.226 (−9.140 to 17.593) | 0.509 | 0.262 (0.102) | 2.697 (−5.578 to 10.972) | 0.496 | 0.261 (0.104) | 1.613 (−3.753 to 6.978) | 0.53 | 0.270 (0.092) |
| SVI | −0.023 (−0.977 to 0.931) | 0.960 | –0.049 (0.764) | −0.056 (−0.646 to 0.535) | 0.842 | –0.038 (0.815) | 0.046 (−0.337 to 0.429) | 0.8 | –0.066 (0.688) |
| LAV | 0.482 (−0.057 to 1.021) | 0.076 | 0.257 (0.109) | 0.264 (−0.070 to 0.598) | 0.112 | 0.252 (0.117) | 0.214 (−0.003 to 0.430) | 0.052 | 0.227 (0.159) |
| LAVI | −0.368 (−0.774 to 0.037) | 0.072 | –0.048 (0.767) | −0.225 (−0.476 to 0.026) | 0.075 | –0.056 (0.733) | −0.142 (−0.305 to 0.021) | 0.082 | –0.055 (0.738) |
| TR | 4.976 (−6.741 to 16.693) | 0.378 | 0.050 (0.759) | 3.088 (−4.166 to 10.342) | 0.377 | 0.042 (0.798) | 1.765 (−2.938 to 6.468) | 0.434 | 0.018 (0.913) |
| Right ventricular function/right ventricular systolic motion | −0.935 (−5.328 to 3.457) | 0.655 | –0.071 (0.662) | −0.239 (−2.959 to 2.480) | 0.853 | –0.035 (0.831) | −0.628 (−2.391 to 1.135) | 0.458 | –0.105 (0.520) |
| Right ventricular function/right ventricular transverse systolic pressure | −0.300 (−1.601 to 1.002) | 0.629 | –0.331 (0.037) | −0.157 (−0.963 to 0.649) | 0.682 | –0.307 (0.054) | −0.119 (−0.641 to 0.404) | 0.633 | –0.343 (0.030) |
| RVD | 9.456 (0.986 to 17.927) | 0.031 | 0.610 (0.000) | 5.697 (0.452 to 10.941) | 0.035 | 0.597 (0.000) | 3.986 (0.586 to 7.386) | 0.025 | 0.571 (0.000) |
| IVC diameter | 11.563 (−6.488 to 29.614) | 0.191 | 0.332 (0.037) | 6.069 (−5.107 to 17.244) | 0.264 | 0.301 (0.059) | 5.773 (−1.473 to 13.018) | 0.11 | 0.327 (0.039) |
| IVC/respiratory variation ratio | −2.710 (−17.813 to 12.393) | 0.706 | –0.331 (0.037) | −0.986 (−10.336 to 8.364) | 0.824 | –0.274 (0.087) | −1.626 (−7.689 to 4.436) | 0.574 | –0.357 (0.024) |
| SPAP | −0.196 (−0.814 to 0.421) | 0.506 | –0.034 (0.833) | −0.098 (−0.480 to 0.285) | 0.592 | –0.078 (0.633) | −0.092 (−0.340 to 0.156) | 0.442 | 0.000 (0.998) |
| TRG | −0.005 (−0.488 to 0.478) | 0.983 | –0.166 (0.305) | −0.040 (−0.339 to 0.259) | 0.776 | –0.211 (0.191) | 0.033 (−0.161 to 0.227) | 0.72 | –0.122 (0.454) |
| E-wave velocity | 0.049 (−0.150 to 0.248) | 0.606 | 0.194 (0.229) | 0.012 (−0.111 to 0.136) | 0.832 | 0.088 (0.589) | 0.035 (−0.045 to 0.115) | 0.362 | 0.272 (0.090) |
| A-wave velocity | −0.040 (−0.107 to 0.027) | 0.224 | –0.284 (0.089) | −0.019 (−0.061 to 0.022) | 0.338 | –0.272 (0.103) | −0.020 (−0.047 to 0.008) | 0.144 | –0.286 (0.086) |
| E/A ratio | −0.689 (−10.764 to 9.386) | 0.885 | 0.355 (0.031) | −0.799 (−7.037 to 5.438) | 0.787 | 0.297 (0.074) | 0.055 (−3.989 to 4.100) | 0.977 | 0.403 (0.013) |
| Septal E-wave velocity | −1.262 (−6.863 to 4.339) | 0.636 | 0.071 (0.661) | −0.255 (−3.723 to 3.212) | 0.877 | 0.063 (0.698) | −1.003 (−3.251 to 1.245) | 0.355 | 0.083 (0.611) |
| Lateral E-wave velocity | 1.346 (−2.870 to 5.562) | 0.505 | 0.268 (0.094) | 0.968 (−1.643 to 3.578) | 0.44 | 0.253 (0.116) | 0.404 (−1.288 to 2.096) | 0.617 | 0.240 (0.135) |
| LAV | −0.152 (−0.507 to 0.203) | 0.375 | 0.124 (0.447) | −0.073 (−0.293 to 0.147) | 0.489 | 0.091 (0.579) | −0.083 (−0.225 to 0.060) | 0.235 | 0.121 (0.458) |
| Right atrial volume | −0.454 (−0.982 to 0.074) | 0.086 | 0.250 (0.119) | −0.223 (−0.550 to 0.104) | 0.166 | 0.227 (0.159) | −0.233 (−0.445 to−0.021) | 0.034 | 0.226 (0.162) |
|
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| Name of variable | TBW/FFM | Segmental phase angle | ECW ratio | ||||||
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| Regression Coefficient (95% CI) | P | ρ (P) | Regression Coefficient (95% CI) | P | ρ (P) | Regression Coefficient (95% CI) | P | ρ (P) | |
|
| |||||||||
| EF | 0.015 (−0.039 to 0.068) | 0.564 | –0.016 (0.923) | −0.008 (−0.131 to 0.116) | 0.896 | –0.110 (0.499) | 0.001 (0.000 to 0.002) | 0.06 | 0.012 (0.939) |
| LVEDD | 0.318 (−1.134 to 1.771) | 0.646 | 0.145 (0.372) | −1.209 (−4.579 to 2.160) | 0.454 | –0.014 (0.933) | 0.016 (−0.014 to 0.046) | 0.27 | 0.122 (0.455) |
| LVESD | −0.193 (−1.285 to 0.900) | 0.711 | 0.053 (0.746) | 0.812 (−1.723 to 3.347) | 0.503 | 0.061 (0.708) | −0.012 (−0.035 to 0.010) | 0.263 | 0.053 (0.747) |
| LAD | 0.208 (−0.921 to 1.336) | 0.699 | 0.070 (0.669) | 1.552 (−1.067 to 4.170) | 0.225 | –0.003 (0.983) | −0.004 (−0.028 to 0.019) | 0.695 | 0.114 (0.484) |
| SVI | 0.014 (−0.066 to 0.095) | 0.712 | –0.007 (0.967) | −0.038 (−0.225 to 0.149) | 0.669 | –0.028 (0.862) | 0.001 (−0.001 to 0.002) | 0.34 | –0.007 (0.964) |
| LAV | 0.019 (−0.026 to 0.065) | 0.382 | –0.046 (0.780) | 0.024 (−0.082 to 0.129) | 0.638 | 0.067 (0.681) | 0.000 (−0.001 to 0.001) | 0.602 | –0.009 (0.957) |
| LAVI | −0.014 (−0.048 to 0.021) | 0.411 | –0.054 (0.742) | −0.045 (−0.124 to 0.035) | 0.246 | –0.100 (0.540) | 0.000 (−0.001 to 0.001) | 0.901 | 0.018 (0.910) |
| TR | 0.151 (−0.838 to 1.141) | 0.748 | 0.056 (0.733) | 1.171 (−1.124 to 3.466) | 0.292 | 0.043 (0.793) | −0.008 (−0.028 to 0.013) | 0.425 | –0.033 (0.838) |
| Right ventricular function/right ventricular systolic motion | −0.196 (−0.567 to 0.175) | 0.275 | –0.096 (0.557) | −0.455 (−1.316 to 0.405) | 0.276 | –0.003 (0.985) | −0.005 (−0.013 to 0.002) | 0.158 | –0.114 (0.482) |
| Right ventricular function/right ventricular transverse systolic pressure | 0.004 (−0.106 to 0.114) | 0.934 | –0.137 (0.401) | 0.048 (−0.207 to 0.303) | 0.691 | –0.060 (0.711) | 0.000 (−0.002 to 0.003) | 0.762 | –0.052 (0.748) |
| RVD | 0.373 (−0.342 to 1.088) | 0.282 | 0.211 (0.192) | 0.653 (−1.006 to 2.312) | 0.413 | 0.338 (0.033) | 0.001 (−0.013 to 0.016) | 0.852 | –0.004 (0.979) |
| IVC diameter | 0.309 (−1.215 to 1.833) | 0.67 | 0.089 (0.587) | 0.963 (−2.574 to 4.499) | 0.569 | 0.039 (0.809) | 0.018 (−0.013 to 0.050) | 0.237 | 0.160 (0.324) |
| IVC/respiratory variation ratio | 0.220 (−1.056 to 1.495) | 0.717 | –0.215 (0.182) | 0.015 (−2.944 to 2.974) | 0.991 | 0.038 (0.817) | −0.006 (−0.032 to 0.020) | 0.629 | –0.208 (0.198) |
| SPAP | −0.008 (−0.060 to 0.044) | 0.750 | 0.022 (0.894) | −0.015 (−0.136 to 0.106) | 0.793 | –0.289 (0.071) | 0.000 (−0.001 to 0.001) | 0.925 | 0.311 (0.051) |
| TRG | 0.014 (−0.026 to 0.055) | 0.465 | 0.113 (0.489) | −0.034 (−0.129 to 0.060) | 0.449 | –0.287 (0.073) | 0.001 (0.000 to 0.001) | 0.123 | 0.252 (0.116) |
| E-wave velocity | 0.010 (−0.007 to 0.026) | 0.246 | 0.246 (0.127) | −0.032 (−0.071 to 0.007) | 0.100 | –0.398 (0.011) | 0.000 (0.000 to 0.001) | 0.094 | 0.434 (0.005) |
| A-wave velocity | −0.002 (−0.008 to 0.003) | 0.384 | 0.062 (0.715) | −0.001 (−0.014 to 0.012) | 0.900 | 0.056 (0.741) | 0.000 (−0.000 to 0.000) | 0.218 | –0.121 (0.477) |
| E/A ratio | −0.033 (−0.884 to 0.818) | 0.935 | 0.121 (0.476) | −0.859 (−2.833 to 1.115) | 0.366 | –0.159 (0.346) | 0.013 (−0.005 to 0.030) | 0.146 | 0.283 (0.089) |
| Septal E-wave velocity | −0.106 (−0.579 to 0.367) | 0.637 | 0.222 (0.168) | 0.539 (−0.558 to 1.637) | 0.31 | 0.027 (0.869) | −0.008 (−0.018 to 0.002) | 0.093 | 0.037 (0.821) |
| Lateral E-wave velocity | −0.165 (−0.521 to 0.191) | 0.336 | 0.006 (0.970) | −0.246 (−1.072 to 0.580) | 0.534 | 0.073 (0.654) | −0.005 (−0.012 to 0.002) | 0.174 | –0.035 (0.829) |
| LAV | −0.014 (−0.044 to 0.016) | 0.348 | 0.081 (0.620) | −0.007 (−0.076 to 0.063) | 0.836 | –0.020 (0.904) | 0.000 (−0.001 to 0.000) | 0.244 | 0.057 (0.725) |
| Right atrial volume | −0.030 (−0.075 to 0.014) | 0.167 | –0.092 (0.572) | 0.001 (−0.103 to 0.104) | 0.99 | 0.146 (0.369) | −0.001 (−0.002 to 0.000) | 0.086 | –0.074 (0.649) |
TBW=Total body water, ICW=Intracellular water, ECW=Extracellular water, TBW/FFM=TBW/free fat mass ratio, EF=Ejection fraction, LVEDD=Left ventricular end-diastolic diameter, LVESD=Left Ventricular End-Systolic diameter, LAD=Left atrial diameter, SVI=Stroke volume index, LAV=Left atrial volume, LAVI=LAV index, TR=Tricuspid regurgitation, SPAP=Systolic pulmonary artery pressure, TRG=Tricuspid regurgitation gradient, E/A ratio=E-wave to A-wave, ECW ratio=ECW ratio, IVC=Inferior vena cava, RVD=Right ventricular diameter
Figure 1.
Scatter plot showing the correlation between total body water and right ventricular diameter. A significant positive correlation was observed (ρ = 0.610, P < 0.001)
Figure 2.
Scatter plot showing the correlation between intracellular water and right ventricular diameter. $a significant positive correlation was found (ρ = 0.597, P < 0.001)
Figure 3.
Scatter plot showing the correlation between extracellular water and right ventricular diameter. A significant positive correlation was observed (ρ = 0.571, P < 0.001)
Figure 4.
Scatter plot showing the correlation between extracellular water ratio and e-wave velocity. A significant positive correlation was detected (ρ = 0.434, P = 0.005)
Figure 5.
Scatter plot showing the correlation between segmental phase angle and e-wave velocity. A significant negative correlation was observed (ρ =–0.398, P = 0.011)
Supplementary Table 2 summarizes the associations between clinical and imaging findings and categorical echocardiographic parameters. A significant association was observed between JVP distention and IVC/respiratory variation ratio (P = 0.003) as well as the presence of pleural effusion (P = 0.021). Patients with JVP distention more frequently demonstrated reduced IVC respiratory variation and a higher incidence of pleural effusion. Among clinical signs, the presence of rales on lung auscultation was significantly associated with abnormal IVC/respiratory variation ratios (P = 0.038). Wheezing was significantly associated with the severity of tricuspid regurgitation (P = 0.038), where moderate regurgitation was more prevalent among patients with this symptom. From imaging findings, pulmonary congestion on chest CT was significantly related to the severity of tricuspid regurgitation (P = 0.037). In addition, pleural effusion was significantly associated with the presence of pericardial effusion (P = 0.018), indicating a potential overlap between fluid accumulation in different anatomical compartments.
Supplementary Table 2.
Association between clinical and imaging findings with categorical echocardiographic features
| Condition | TR | IVC/respiratory variation ratio | Pericardial effusion | Pleural effusion | Sonographic B line | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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| No, n (%) | Mild, n (%) | Moderate, n (%) | Severe, n (%) | Reduced, n (%) | Normal, n (%) | No, n (%) | Mild, n (%) | Moderate, n (%) | No, n (%) | Mild, n (%) | Moderate, n (%) | No, n (%) | Yes, n (%) | |
| JVP distention | ||||||||||||||
| Absent | 2 (40.0) | 4 (50.0) | 7 (28.0) | 0 | 5 (17.9) | 8 (66.7) | 12 (48.0) | 1 (16.7) | 0 | 4 (57.1) | 9 (30.0) | 0 | 10 (31.3) | 3 (37.5) |
| Present | 3 (60.0) | 4 (50.0) | 18 (72.0) | 2 (100.0) | 23 (82.1) | 4 (33.3) | 13 (52.0) | 5 (83.3) | 9 (100.0) | 3 (42.9) | 21 (70.0) | 3 (100.0) | 22 (68.8) | 5 (62.5) |
| P | 0.486 | 0.003 | 0.021 | 0.177 | 0.177 | |||||||||
| Rales on lung auscultation | ||||||||||||||
| Absent | 0 | 2 (25.0) | 2 (8.0) | 0 | 1 (3.6) | 3 (25.0) | 4 (16.0) | 0 | 0 | 2 (28.6) | 2 (6.7) | 0 | 3 (9.4) | 1 (12.5) |
| Present | 5 (100.0) | 6 (75.0) | 23 (92.0) | 2 (100.0) | 27 (96.4) | 9 (75.0) | 21 (84.0) | 6 (100.0) | 9 (100.0) | 5 (71.4) | 28 (93.3) | 3 (100.0) | 29 (90.6) | 7 (87.5) |
| P | 0.409 | 0.038 | 0.264 | 0.184 | 0.792 | |||||||||
| Lower limb edema | ||||||||||||||
| Absent | 0 | 1 (12.5) | 2 (8.0) | 0 | 1 (3.6) | 2 (16.7) | 2 (8.0) | 1 (16.7) | 0 | 2 (28.6) | 1 (3.3) | 0 | 3 (9.4) | 0 |
| Present | 5 (100.0) | 7 (87.5) | 23 (92.0) | 2 (100.0) | 27 (96.4) | 10 (83.3) | 23 (92.0) | 5 (83.3) | 9 (100.0) | 5 (71.4) | 29 (96.7) | 3 (100.0) | 29 (90.6) | 8 (100.0) |
| P | 0.834 | 0.150 | 0.481 | 0.065 | 0.368 | |||||||||
| Wheezes on auscultation | ||||||||||||||
| Absent | 5 (100.0) | 6 (75.0) | 25 (100.0) | 2 (100.0) | 27 (96.4) | 11 (91.7) | 23 (92.0) | 6 (100.0) | 9 (100.0) | 6 (85.7) | 29 (96.7) | 3 (100.0) | 31 (96.9) | 7 (87.5) |
| Present | 0 | 2 (25.0) | 0 | 0 | 1 (3.6) | 1 (8.3) | 2 (8.0) | 0 | 0 | 1 (14.3) | 1 (3.3) | 0 | 1 (3.1) | 1 (12.5) |
| P | 0.038 | 0.527 | 0.532 | 0.448 | 0.277 | |||||||||
| Reduced breath sounds on auscultation | ||||||||||||||
| Absent | 5 (100.0) | 6 (75.0) | 18 (72.0) | 0 | 19 (67.9) | 10 (83.3) | 20 (80.0) | 4 (66.7) | 5 (55.6) | 5 (71.4) | 23 (76.7) | 1 (33.3) | 24 (75.0) | 5 (62.5) |
| Present | 0 | 2 (25.0) | 7 (28.0) | 2 (100.0) | 9 (32.1) | 2 (16.7) | 5 (20.0) | 2 (33.3) | 4 (44.4) | 2 (28.6) | 7 (23.3) | 2 (66.7) | 8 (25.0) | 3 (37.5) |
| P | 0.066 | 0.315 | 0.349 | 0.276 | 0.479 | |||||||||
| Chest CT: pulmonary congestion | ||||||||||||||
| Absent | 2 (40.0) | 4 (50.0) | 2 (8.0) | 0 | 5 (17.9) | 3 (25.0) | 7 (28.0) | 1 (16.7) | 0 | 1 (14.3) | 6 (20.0) | 1 (33.3) | 5 (15.6) | 3 (37.5) |
| Present | 3 (60.0) | 4 (50.0) | 23 (92.0) | 2 (100.0) | 23 (82.1) | 9 (75.0) | 18 (72.0) | 5 (83.3) | 9 (100.0) | 6 (85.7) | 24 (80.0) | 2 (66.7) | 27 (84.4) | 5 (62.5) |
| P | 0.037 | 0.605 | 0.193 | 0.788 | 0.167 | |||||||||
| Chest CT: cardiomegaly | ||||||||||||||
| Absent | 0 | 4 (50.0) | 5 (20.0) | 0 | 4 (14.3) | 5 (41.7) | 8 (32.0) | 1 (16.7) | 0 | 3 (42.9) | 6 (20.0) | 0 | 6 (18.8) | 3 (37.5) |
| Present | 5 (100.0) | 4 (50.0) | 20 (80.0) | 2 (100.0) | 24 (85.7) | 7 (58.3) | 17 (68.0) | 5 (83.3) | 9 (100.0) | 4 (57.1) | 24 (80.0) | 3 (100.0) | 26 (81.3) | 5 (62.5) |
| P | 0.133 | 0.057 | 0.134 | 0.267 | 0.256 | |||||||||
| Chest CT: pleural effusion | ||||||||||||||
| Absent | 1 (20.0) | 4 (50.0) | 5 (20.0) | 0 | 5 (17.9) | 5 (41.7) | 10 (40.0) | 0 | 0 | 4 (57.1) | 6 (20.0) | 0 | 9 (28.1) | 1 (12.5) |
| Present | 4 (80.0) | 4 (50.0) | 20 (80.0) | 2 (100.0) | 23 (82.1) | 7 (58.3) | 15 (60.0) | 6 (100.0) | 9 (100.0) | 3 (42.9) | 24 (80.0) | 3 (100.0) | 23 (71.9) | 7 (87.5) |
| P | 0.292 | 0.111 | 0.018 | 0.072 | 0.361 | |||||||||
TR=Tricuspid regurgitation, JVP=Jugular venous pressure, CT=Computed tomography, IVA=Inferior vena cava
Table 4 displays the associations between laboratory variables and bioelectrical impedance measurements. Among the examined markers, serum creatinine was significantly associated with body cell index (BCI), showing a negative regression coefficient (–0.104, 95% CI: –0.208 to –0.001, P = 0.049), indicating a statistically significant inverse relationship. No other significant associations were observed between impedance parameters and laboratory values, including log-transformed NT-pro BNP, CA125, or hematocrit. While the association between hematocrit and ECW ratio approached significance (P = 0.069), it did not meet the threshold for statistical relevance.
Table 4.
Linear regression analysis of laboratory markers associated with bioelectrical impedance parameters
| Name of variable | Logarithm of NT-proBNP | CA125 | Serum creatinine | Hematocrit | ||||
|---|---|---|---|---|---|---|---|---|
|
|
|
|
|
|||||
| Regression coefficient (95% CI) | P | Regression coefficient (95% CI) | P | Regression coefficient (95% CI) | P | Regression coefficient (95%CI) | P | |
| TBW | 0.095 (−0.715 to 0.905) | 0.813 | −17.962 (−191.760 to 155.837) | 0.835 | −0.070 (−0.615 to 0.476) | 0.796 | −3.506 (−18.487 to 11.474) | 0.637 |
| ICW | −0.034 (−0.768 to 0.699) | 0.925 | 20.924 (−136.531 to 178.380) | 0.788 | 0.224 (−0.270 to 0.719) | 0.362 | −0.348 (−13.919 to 13.224) | 0.959 |
| ECW | −0.132 (−1.205 to 0.940) | 0.803 | 22.191 (−208.058 to 252.440) | 0.846 | 0.030 (−0.692 to 0.753) | 0.932 | 8.906 (−10.940 to 28.753) | 0.368 |
| BCI | −0.022 (−0.176 to 0.132) | 0.771 | 4.788 (−28.250 to 37.826) | 0.77 | −0.104 (−0.208 to−0.001) | 0.049 | −0.068 (−2.916 to 2.779) | 0.961 |
| TBW/FFM | −0.262 (−0.828 to 0.303) | 0.351 | −31.456 (−152.772 to 89.859) | 0.601 | −0.318 (−0.699 to 0.063) | 0.099 | 5.243 (−5.214 to 15.700) | 0.315 |
| Segmental phase angle | −0.051 (−0.217 to 0.114) | 0.530 | −24.732 (−60.181 to 10.716) | 0.165 | 0.083 (−0.028 to 0.195) | 0.137 | −0.967 (−4.022 to 2.089) | 0.524 |
| ECW ratio | 10.943 (−31.541 to 53.246) | 0.603 | 119.358 (−9000.297 to 9239.013) | 0.979 | 11.973 (−16.654 to 40.599) | 0.401 | −727.463 (−1513.530 to 58.603) | 0.069 |
NT-pro BNP: N-terminal pro–B-type natriuretic peptide, TBW: Total body water, ICW: Intracellular water, ECW: Extracellular water, BCI: Body cell index, TBW/FFM: TBW/free fat mass ratio, ECW ratio: Extracellular water ratio, CI: Confidence interval, CA125: Cancer antigen 125.
Table 5 is a single combined table summarizing all the significant associations from Tables 2-4. It keeps the data concise and highlights only meaningful correlations.
Table 5.
Associations between clinical, imaging, echocardiographic, and laboratory markers and bioelectrical impedance indices in 40 patients with heart failure
| Marker type | Variable | Bioelectrical Impedance Index | Regression coefficient/mean±SD | P |
|---|---|---|---|---|
| Clinical | Lower limb edema | ECW ratio | 0.405±0.023 versus 0.381±0.013 | 0.045 |
| Imaging (chest CT) | Pulmonary congestion | Segmental phase angle | 5.0±2.1 versus 6.9±3.2 | 0.027 |
| Pleural effusion | Segmental phase angle | 4.7±1.5 versus7.5±3.4 | 0.004 | |
| Pleural effusion | ECW ratio | 0.407±0.024 versus 0.392±0.015 | 0.047 | |
| Echocardiography | RVD | TBW | 9.456 (0.986 to 17.927) | 0.031 |
| RVD | ICW | 5.697 (0.452 to 10.941) | 0.035 | |
| RVD | ECW | 3.986 (0.586 to 7.386) | 0.025 | |
| Right atrial volume | ECW | −0.233 (−0.445 to−0.021) | 0.034 | |
| E-wave velocity | Segmental phase angle | 0.434±0.005 | 0.005 | |
| Laboratory | Serum creatinine | (BCI) | −0.104 (−0.208 to−0.001) | 0.049 |
BCI=Body cell index, ECW=Extracellular water, ECW ratio=ECW ratio, TBW=Total body water, ICW=Intracellular water, RVD=Right ventricular diameter, CT=Computed tomography
DISCUSSION
This study aimed to investigate the correlation between echocardiographic parameters and BIA indices in the assessment of volume status among patients with HF and CKD. The findings revealed several significant associations, suggesting that the two methods provide complementary information. Specifically, clinical signs such as jugular venous distention and rales were associated with echocardiographic markers of volume overload and impaired cardiac function, whereas BIA measurements reflected corresponding changes in fluid compartments. Notably, RVD showed a consistent relationship with multiple BIA-derived fluid indices, and pleural effusion and lower limb edema were linked to elevated ECW ratios. In addition, pulmonary congestion was associated with reduced segmental phase angles, and serum creatinine was inversely correlated with body cell index, indicating a connection between renal function and cellular hydration. These results support the potential utility of combining BIA and echocardiography for a more comprehensive evaluation of fluid status in this high-risk population.
The findings of our study are largely explainable within known physiological frameworks. An increase in LAV and LAVI is commonly regarded as a marker of elevated left ventricular filling pressures.[17] When the left ventricle fails to effectively eject blood, pressure rises in the left atrium, often resulting in atrial enlargement.[18] This pressure elevation may extend backward into the pulmonary venous system, leading to pulmonary congestion and symptoms such as dyspnea. Furthermore, left atrial enlargement is associated with an increased risk of atrial arrhythmias, including atrial fibrillation, which can negatively impact patient prognosis.[19]
Pleural effusion, or the accumulation of fluid in the pleural space, can occur due to various causes such as heart failure, infections, or malignancies.[20] In patients with HF, elevated venous pressures may lead to fluid leakage into the pleural cavity, impairing gas exchange and producing symptoms such as shortness of breath and chest discomfort.[20] In BIA, the ECW/TBW ratio serves as an indicator of extracellular fluid accumulation. An elevated ECW/TBW ratio may reflect the presence of pleural effusion and a general increase in body fluid volume.[21,22]
The absence of significant correlations between some echocardiographic and BIA parameters may stem from the complex interplay of physiological factors. For instance, systolic pulmonary artery pressure (SPAP) can be influenced by variables such as fluid status, right ventricular function, and pulmonary vascular resistance – factors that may not be directly captured through bioimpedance measurements.[23] Similarly, left ventricular EF is modulated by preload, afterload, and myocardial contractility, which may not be linearly reflected in impedance-derived indices. These complexities underscore the notion that each diagnostic modality provides distinct but complementary insights into the patient’s hemodynamic status, and their combined use may offer a more comprehensive clinical evaluation.[24]
BIA has notable limitations in the assessment of volume status, particularly in patients with HF and CKD. One of the primary concerns is its sensitivity to hydration-related fluctuations. The technical aspects of BIA measurement, including the accuracy of current sources and circuit design, can influence its reliability across different body segments.[25] Awareness of these technical limitations is critical when interpreting impedance-derived fluid indices in clinical settings. BIA estimates total and compartmental body water based on electrical conductivity through tissues, a measurement influenced by factors such as electrolyte imbalance, skin temperature, and recent fluid intake.[26] HF is a prevalent condition linked with significant morbidity and mortality on a global scale, characterized by a 5-year mortality rate of approximately 50% following the initial diagnosis. Electrolyte imbalances, particularly those involving potassium and sodium, pose critical considerations in the management of HF, as they may necessitate modifications in therapeutic strategies and have associations with patient prognosis.[27] In HF patients, fluid distribution is often altered due to congestion and intercompartmental shifts, which can lead to inaccurate estimates of TBW and ECW.[28] Moreover, BIA assumes stable fluid distribution, a condition often unmet in clinical settings where patients experience acute volume shifts or rapid changes in hydration, thereby limiting its reliability in dynamic clinical environments.[29]
Another critical limitation lies in BIA’s dependence on predictive equations derived from general populations. These assumptions may not accurately reflect individual conditions, especially in patients with severe muscle wasting, obesity, or edema.[30] In HF and CKD populations, reduced lean body mass and abnormal fluid retention patterns may distort impedance readings and lead to misinterpretation of hydration status.[22] In addition, BIA is less effective at detecting localized fluid overload, such as pleural effusions or ascites, as it provides a global rather than regional evaluation of fluid status. These limitations underscore the importance of using complementary imaging modalities, such as echocardiography or lung ultrasound, to obtain a more precise assessment of fluid status in this complex patient population.[31]
Several previous studies have explored the utility of BIA in assessing fluid status, each from a distinct perspective. The systematic review by Meyne et al. and the present study both emphasized the clinical relevance of BIA in patients with HF and CKD, though Mein’s work focused on its prognostic value for outcomes such as mortality and cardiovascular events, whereas our study examined its correlation with echocardiographic and thoracic imaging findings.[8] Similarly, Hussein et al. assessed BIA in CKD patients but concentrated on clinical thresholds for fluid overload, highlighting tools such as FO/ECV and CNR, in contrast to our emphasis on imaging correlations, including associations between pleural effusion and the ECW/TBW ratio, and between TBW and IVC diameter.[32] Hur et al. investigated BIA in dialysis patients and reported volume overload risks specific to dialysis modality, while our study included non-dialysis patients and extended the evaluation to include cardiac and pulmonary imaging, revealing significant relationships between fluid indices and imaging features relevant to HF and CKD.[33] Matthie et al. focused on the technical validation of BIA, particularly the limitations of single-frequency devices in distinguishing between fluid compartments, whereas our study validated BIA markers clinically through their correlation with imaging and hemodynamic parameters, reinforcing their practical value in the management of fluid status in HF and CKD patients.[34]
This study has several strengths and limitations. A key strength lies in its integrated approach, combining BIA with echocardiographic and chest CT findings to evaluate volume status in patients with HF and CKD, providing a multidimensional assessment rarely addressed in previous research. The use of multiple objective measurement tools enhances the clinical applicability and relevance of the findings. However, limitations include the relatively small sample size, which may reduce the generalizability of results and limit statistical power in subgroup analyses. In addition, the cross-sectional design precludes any causal inference, and the absence of follow-up data prevents evaluation of long-term clinical outcomes. The reliance on noninvasive techniques such as BIA, which can be affected by hydration shifts, body composition variability, and measurement assumptions, also presents potential sources of bias. Despite these limitations, the study provides valuable insights into the complementary role of BIA and cardiac imaging in fluid status assessment.
CONCLUSION
The findings of this study indicate that BIA and echocardiography can serve as complementary tools in assessing volume status in patients with HF and CKD. Significant correlations were observed between specific indices of both methods, such as the association between IVC diameter and TBW, as well as reduced left ventricular EF with increased LAV and LAVI. Imaging findings also revealed that pleural effusion was significantly associated with a higher ECW/TBW ratio, highlighting the potential of BIA in detecting fluid overload. However, certain parameters, such as systolic pulmonary artery pressure (SPAP), did not show a significant relationship with BIA measures. These results suggest that while BIA provides valuable information on body fluid distribution and composition, echocardiography remains essential for evaluating cardiac function. The integration of these non-invasive modalities may enhance the accuracy of volume assessment in this patient population. Nevertheless, larger and more diverse studies are warranted to confirm these findings and establish their clinical utility.
Ethical approval
The study was conducted in accordance with the Declaration of Helsinki and was approved by the institutional ethics committee of Shahid Beheshti University of Medical Sciences (Ethics Code: IR.SBMU.MSP.REC.1402.558).
Informed consent
Written informed consent was obtained from all participants prior to their enrollment in the study.
Data availability statement
The data supporting the findings of this study are not publicly available. Requests for access to the data should be directed to the corresponding author.
Authors’ contributions
F. O., A. A. N., and F. S. contributed to the study design, data collection, and analysis. M. H. A. participated in data interpretation and manuscript revision. All authors reviewed and approved the final version of the manuscript.
Acknowledgments
The authors would like to thank the staff of Imam Hossein Hospital for their support and assistance during the study.
Conflicts of interest
There are no conflicts of interest.
Funding Statement
Nil.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data supporting the findings of this study are not publicly available. Requests for access to the data should be directed to the corresponding author.