Patients with TR undergoing transthoracic echocardiography were prospectively assessed from October 2022 to June 2024 in 3 centers. Exclusion criteria were hospital admission due to decompensated congestive heart failure, ongoing intravenous diuretic therapy at the time of echocardiography, presence of cirrhosis, and end-stage kidney disease (stage V). These exclusions were applied to minimize congestion bias and ensure the interpretability of portal and renal venous studies.

TR severity was evaluated using biplane VC width and 2D PISA-derived EROA and classified according to the proposed 5-grade system.5,6,17 The etiology of TR was determined following recommendations from the Tricuspid Valve Academic Research Consortium.18 Hepatic, portal, and intrarenal venous ultrasound images were acquired by independent operators after standard echocardiographic assessment. TR grading was blinded to portal and renal ultrasound findings, and venous ultrasound interpretation was performed in a central core laboratory blinded to TR classification. Clinical data were extracted from local electronic health records, and a basic physical examination, including assessment of peripheral edema, was performed in all patients. Ethics approval was obtained from the local institutional review board, and written informed consent was secured from all participants.

Venous Doppler studies of the hepatic, portal, and intrarenal veins were performed using echocardiographic sector transducers (frequency range 2.5-5MHz) with patients in the left lateral decubitus position. Hepatic and portal veins were identified through a transhepatic acoustic window using color Doppler (velocity scale ∼30cm/s). The right kidney was examined using a transhepatic approach to obtain a longitudinal view, and interlobar vessels were visualized with color Doppler (velocity scale 8-16cm/s). Pulse-wave Doppler was acquired with ECG synchronization, ensuring optimal alignment during sustained expiration while avoiding Valsalva maneuvers. Low wall filter settings and appropriately adjusted velocity scales were used. This methodology has been previously validated in studies of venous congestion.13,14

Hepatic vein flow was reported as the presence or absence of revHV. Portal vein flow was analyzed by measuring peak (Vmax) and nadir (Vmin) velocities during the cardiac cycle. The portal pulsatility fraction (PPF) was calculated as:

The presence of portal systolic flow reversal (revP) was also recorded. As shown in figure 1, intrarenal venous flow pattern was categorized as continuous, biphasic, monophasic (monR), or intrarenal venous systolic flow reversal (revR).

Figure 1.

Examples of hepatic, intrarenal, and portal vein flow patterns evaluated. Hepatic vein flow was assessed by the presence or absence of hepatic vein systolic flow reversal (revHV). Intrarenal venous flow was assessed as continuous, biphasic, monophasic (monR), or reversal (revR) flow pattern. Portal vein flow was assessed quantitatively as a percentage of pulsatility (portal pulsatility fraction [PPF]) and qualitatively as the presence of portal systolic flow reversal (revP), equivalent to a PPF >100%.

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Two observers independently analyzed hepatic, portal, and intrarenal venous patterns. Intraobserver variability was assessed by repeat analysis performed by a single observer after a 1-month interval.

Categorical variables are expressed as counts and percentages, and continuous variables as mean±standard deviation or median with interquartile range (IQR), depending on the distribution assessed by the Shapiro-Wilk test. Group comparisons for categorical variables were performed using the chi-square test or Fisher exact test, as appropriate. Continuous variables were compared using the unpaired t-test or Mann-Whitney U-test, depending on distribution. Ordinal variables were analyzed using one-way ANOVA or the Kruskal–Wallis test. The diagnostic accuracy of hepatic, portal, and intrarenal venous flow indices was assessed using receiver operating characteristic (ROC) curve analysis. Cutoff values of PPF for grades III, IV, and V TR were determined using ROC curves, the proportion of correctly classified cases, and the Youden index. A sensitivity analysis was performed according to different definitions of TR severity (per protocol using both VC and EROA, VC alone, and EROA alone).

Inter- and intraobserver reproducibility was assessed using the Cohen kappa coefficient for categorical variables (hepatic, portal, and intrarenal flow patterns) and mean difference with intraclass correlation coefficients for continuous variables (PPF%). A 2-sided P value<.05 was considered statistically significant. All analyses were conducted with Stata software, version 14 (StataCorp, College Station, United States).

A total of 143 patients were prospectively enrolled, with a mean age of 76 years; 73% were female. Baseline characteristics, including past medical history, clinical features, physical examination, and invasive right heart measurements, are detailed in table 1. According to the proposed 5-grade classification, 14 patients (9.7%) had mild (I) TR, 30 (21%) had moderate (II), 52 (36%) had severe (III), 30 (21%) had massive (IV), and 17 (12%) had torrential (V) TR. Patients with higher TR grades tended to present with worse functional class, more frequent basal peripheral edema, and greater basal oral diuretic requirements. The most common TR etiology was ventricular functional TR, observed in 73 patients (51%). Atrial functional TR was present in 56 patients (39%), lead-associated TR in 29 (20%), and mixed etiologies in 23 (16%); these were associated with higher TR grades, whereas primary etiologies were less common, observed in 11 patients (8%) (table 2).

Higher TR grades were significantly associated with larger left atrial size but not with larger left ventricular size. For the right atrium (both area and volume), right ventricle (mid-diameter and area), tricuspid annulus, and inferior vena cava diameters, there was a statistically significant trend toward larger measurements with higher TR grades. Regarding right ventricular function, TAPSE (tricuspid annular plane systolic excursion) showed a nonsignificant trend toward lower values with increasing TR grades, and no differences in fractional area change were observed between groups.

Hepatic vein flow was interpretable in 96% of patients, intrarenal venous flow in 98%, and portal vein flow in 99%. Hepatic, portal, and intrarenal venous flow patterns for every TR grade are summarized in table 3.

Patients with grade III TR had a revHV pattern in 94.2% of cases, a monR in 70.6%, and a median PPF of 59% (IQR, 41%-67%). Grade IV TR patients had a revHV pattern in 96.7% of cases, a monR pattern in 89.3%, and a median PPF of 96% (IQR, 64%-100%). Finally, all patients with grade V TR exhibited a revHV pattern, and 62.5% displayed an revR pattern; the remainder had a monR pattern. Portal venous flow was consistently pathologic in grade V patients, with 75% showing a revP pattern and a median PPF of 147% (IQR, 119%-169%).

A sensitivity analysis was performed to assess the risk of bias related to the definition of TR severity (per protocol using both VC and EROA, VC alone, or EROA alone) and revealed no significant differences between methods (table 1S).

A post hoc power calculation using a chi-square goodness-of-fit test with an α error of 0.05 and an effect size of 0.3 had a power (1 − β) of 0.833.

Intraobserver agreement in hepatic, portal, and intrarenal pattern classification was very high, and the standard deviation of PPF measurement was 3.3%, with a very high intraclass correlation coefficient. Interobserver agreement was high for portal and intrarenal pattern classification and adequate for hepatic vein classification; the standard deviation of PPF measurement was 8.1% (table 4), with a high intraclass correlation coefficient.

Regarding the use of hepatic, portal, and intrarenal venous flow patterns for TR severity grading, the main findings of this study can be summarized as follows: a) revHV patter had good sensitivity for diagnosing at least grade III TR but showed poorer performance in discriminating between TR grades III, IV, and V; b) PPF may differentiate among grade III, grade IV, and grade V TR, with cutoff values of ≥ 40% for grade III, ≥ 80% (including 100%) for grade IV, and >100% for grade V TR; c) monR had higher specificity for the diagnosis of grade III TR than the revHV pattern. Severely impaired intrarenal flow, characterized by monR and revR patterns, was commonly found in TR grades IV and V; and d) systolic flow reversal patterns in intrarenal (revR) and portal (revP) veins appeared to have high specificity for the diagnosis of grade V TR.

These results invite exploration of these parameters as supportive or complementary tools when diagnostic uncertainty exists between adjacent TR grades, after quantitative assessment has been completed. Figure 2 offers a visual summary—reflecting our group's opinion—of how these parameters may be applied when grading TR within the 5-grade classification. Figure 3 provides representative examples of a patient in each TR grade and the corresponding venous flow patterns observed. Figure 4 presents a summary of the methods and results.

Figure 2.

Summary of hepatic, portal, and intrarenal venous flow patterns across the 5-grade tricuspid regurgitation (TR) classification, based on the findings of this study. Hepatic, portal, and intrarenal venous flow patterns are shown in alignment with the 5-grade TR classification, matched to the most representative TR grade according to the diagnostic performance observed in this study. The presence of hepatic vein systolic flow reversal (revHV), monophasic intrarenal flow (monR), and portal pulsatility fraction (PPF) >40% were most commonly associated with severe (grade III) or greater TR. A PPF >80%, including 100%, was associated with massive (grade IV) TR, while PPF >100%—corresponding to portal systolic flow reversal (revP)—and intrarenal venous systolic flow reversal (revR) were observed in cases of torrential (grade V) TR.

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Figure 3.

Representative cases of hepatic, portal, and intrarenal venous ultrasound for each tricuspid regurgitation (TR) grade. Five representative cases are shown, one for each TR grade. Patient age, sex, TR etiology, and quantitative parameters are provided. EROA, effective regurgitant orifice area; IVC, inferior vena cava diameter; PPF, portal pulsatility fraction; revHV, hepatic vein systolic flow reversal; revP, portal systolic flow reversal; revR, intrarenal venous systolic flow reversal; VC, vena contracta.

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Figure 4.

Central illustration. This study aimed to describe hepatic, portal, and intrarenal venous flow patterns in tricuspid regurgitation (TR) using the 5-grade classification system and to explore their potential role in TR grading, similar to the use of hepatic vein systolic flow reversal (revHV) for severe TR. The study included 143 prospective TR cases, excluding those with heart failure decompensation. TR severity was assessed using biplane vena contracta (VC) width and 2D effective regurgitant orifice area (EROA). Results indicated that revHV did not effectively discriminate between TR grades III, IV, and V. However, portal pulsatility fraction (PPF) showed promise in distinguishing severe, massive, and torrential TR, with optimal thresholds of PPF >40% for grade III, PPF >80% for grade IV, and PPF >100% for grade V. Monophasic intrarenal flow (monR) demonstrated high specificity for grade III or greater TR, while intrarenal venous systolic flow reversal (revR) and portal systolic flow reversal (revP) showed high specificity for grade V TR. In conclusion, hepatic, portal, and intrarenal venous flow patterns are associated with the extended TR grades and may serve as additional parameters in TR grading.

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Accurate diagnosis and grading of TR with the 5-grade classification is clinically relevant, as higher severity is associated with worse outcomes. One study19 reported increased mortality in patients with EROA >0.7cm2, while another20 found survival differences between torrential TR and less severe grades using EROA >0.8cm2. Patients with VC width >14mm showed higher rates of cardiovascular events (death or heart failure hospitalization), suggesting worse prognosis in massive vs severe TR, but no additional difference in torrential TR.21 In contrast, another study found that torrential TR (VC >21 mm) was associated with higher event rates than massive TR.22 These findings suggest prognostic differences within the 5-grade classification, although results vary depending on whether VC or EROA is used.

Data on venous Doppler ultrasound patterns also suggest clinical relevance in various settings. One study related monR in heart failure to unplanned hospitalizations and cardiovascular death.12 Another found that portal and intrarenal flow alterations (PPF >50% and monR) were independently associated with acute kidney disease after cardiac surgery.23 Additional studies found hepatic, portal, and intrarenal venous patterns correlated with invasive right atrial pressure,16 which has also been related to outcomes in secondary TR.24,25 Portal vein alterations (PPF) predicted a composite outcome (adverse renal outcomes or death) in intensive care patients.14 Discontinuous intrarenal venous patterns were associated with worsening renal function in acute heart failure,26 and another study found intrarenal and portal venous patterns predicted in-hospital mortality.27 These findings support the prognostic value of hepatic, portal and intrarenal venous ultrasound patterns in various settings, although their role in TR remains unexplored.

In our study, we identified PPF as a continuous parameter that may help discriminate among TR grades and found that signs of extreme hemodynamic alteration in target organs (such as revP and revR) were more associated with grade V than with grade III TR. These findings reflect the hemodynamic impact of TR on the kidneys and liver at advanced stages of the disease, with evidence of further damage in the extended grades (grades IV and V), beyond what is observed in grade III, reinforcing the rationale behind a 5-grade classification.

These signs are target-organ based and are not affected by the complexity of the jet, valve anatomy, lead-induced artifacts, or tricuspid repair devices, as VC and EROA methods sometimes are.28 Similar to revHV, these signs are affected by right atrial pressure but have better specificity for higher TR grades owing to their distance from the atria. Therefore, their use in combination with current quantitative assessment may be useful for TR grading, particularly in patients with a challenging echocardiographic window and in those with higher TR grades.

However, several factors are worth considering. The pathophysiological basis of hepatic, portal, and intrarenal venous flow systolic alterations is related to the TR V wave and central venous pressure, both influenced by intravascular congestion, right ventricular function, and other factors. Therefore, in our opinion, patients with overt decompensated congestive heart failure should be excluded from assessments using these parameters to avoid overestimating TR severity. Some degree of intravenous congestion is frequently present in patients with significant TR and correlates with disease severity (table 1). To differentiate baseline congestion related to symptomatic TR from overt heart failure decompensation, the exclusion criterion for this study was hospital admission and/or intravenous diuretic therapy. Because decompensated patients were excluded from the present study to minimize bias related to severe congestion, the reported diagnostic performance cannot be extrapolated to them. However, patients with baseline congestion related to symptomatic TR are represented in this study, and the results may apply to them. It is also worth noting that venous flow alterations are influenced by the respiratory cycle and intra-abdominal pressure; therefore, image acquisition must be performed in expiration and avoid Valsalva maneuvers. In this study, no ventilated patients were included, and the validity of this technique in such patients should be further explored. Pathological conditions of the liver and kidneys, such as cirrhosis and end-stage kidney disease, may blunt or artifactually alter venous flow,29–31 and therefore this approach should also be avoided in these patients. Considering these factors is crucial for ensuring the reproducibility and reliability of the technique.

This study has some limitations. First, as previously discussed, these results cannot be applied to patients with overt decompensated heart failure, as they were excluded from this study. Future research is needed to clarify whether these techniques may have a role in this population.

Second, in our study, the biplanar VC and 2D PISA EROA were the classifying variables and therefore the comparative standard, even though in some cases they were discrepant at the time of staging TR. As commonly observed in clinical practice, up to 13% of patients had a discrepancy between VC and EROA, which made it difficult to classify them into a single severity group. According to the study protocol, these patients were classified into the nearest matching severity group by the operator in charge of TR staging, following current guideline-based parameters (including additional criteria such as regurgitant volume and 3D VC area, when available). As a final criterion, the protocol established that biplanar VC would take precedence over EROA. To minimize potential bias from this discrepancy, we conducted a sensitivity analysis, which showed no significant impact on the performance of the studied patterns regardless of the TR grade definition used (by protocol, VC only, or EROA only). Further details are provided in table 1S. In addition, we observed a tendency for VC values to be lower than EROA for a given TR grade. This discrepancy is likely because 2D transthoracic echocardiography may underestimate the largest VC diameter compared with 3D and transesophageal echocardiography when assessing biplanar VC, as previously reported.18,31,32 These challenges in TR assessment reflect current clinical practice, where staging parameters may not always align perfectly, and some patients may require additional signs and measurements for more accurate grading. The systematic use of 3D techniques, such as VC area assessment, could help address these limitations.

Another limitation is the sample size. Although post hoc power analysis indicated adequate power to detect significant differences between groups, larger cohorts are needed to better define and characterize the performance of these parameters in TR grading and, particularly, to more precisely delineate the differences between higher TR grades. Studies with larger sample sizes and an external validation cohort are necessary to confirm our findings, assess their generalizability to other populations and clinical settings, further explore their implications, and improve our understanding of the potential and practicality of this approach.

Future research should also evaluate whether alterations in portal and intrarenal venous flow have prognostic significance in patients with TR and assess whether these markers can independently stratify risk in this population.