The Role Bubbles Test in Detection of Porto-pulmonary Shunt in Liver Cirrhosis Patients by Echocardiography and Its Correlation with Right Ventricular Indices

Liver Cirrhosis is a pathological process that represents the last stage of any chronic liver disease. It is marked by fibrosis and alteration of normal hepatic tissue into irregular, abnormal nodules, known as regenerative nodules.   This transformation is irreversible and affects the whole liver. Histologically, cirrhosis is considered an all-or-nothing diagnosis, although clinically it is classified as compensated or decompensated. Decompensated cirrhosis, which is identified by the presence of ascites, variceal hemorrhage, encephalopathy, or jaundice, is a complication that results from the main consequence of cirrhosis: portal hypertension and liver failure  {1}.Hepatopulmonary  syndrome (HPS) is vasodilation in the pulmonary circulation leads to arterial hypoxemia, the main sign of hepato pulmonary syndrome. Normal pulmonary capillaries are 8 µm wide, and red blood cells, which are slightly less than 8 µm wide, pass through them one at a time, helping oxygenate the blood. In hepato pulmonary syndrome, the pulmonary capillaries can be as wide as 500 µm, allowing red blood cells to travel through them in groups of several cells. Because of this, many red blood cells don't get oxygen, which is like a right-to-left shunt  {2}. Epidemiology  : HPS is thought to be present in between 4% and 32% of cases of liver cirrhosis. The incidence of HPS in individuals assessed for LT is approximately 10–30%. HPS is usually detected in the sixth decade of life, exhibiting no significant association with gender, the a etiology of underlying liver disease, or the Model for End-Stage Liver Disease (MELD). The determined five-year survival rate was 20% for individuals with HPS, in contrast to 32–63% for individuals without HPS. {4},

Intra-pulmonary vascular dilatation (IPVD) and intra-pulmonary shunting are relatively frequent findings among patients with liver cirrhosis and portal hypertension. Several Middle Eastern studies evaluated the prevalence of pulmonary vascular abnormalities using contrast-enhanced echocardiography.

An Iraqi study conducted among patients with chronic liver disease and portal hypertension demonstrated intrapulmonary vascular dilatation in approximately 36.6% of cirrhotic patients using contrast echocardiography {5} .

 Similarly, an Iranian study reported pulmonary shunting in 23.7% of patients with liver cirrhosis. {6}.

Furthermore, an Egyptian study demonstrated intrapulmonary vascular dilatation in approximately 20% of cirrhotic patients {7} .

This study aims to --detect intrapulmonary  vascular shunt in patients with liver cirrhosis using contrast echocardiography (bubbles test).

--To evaluate the correlation between Porto-pulmonary hypertension in patients with liver cirrhosis and the right ventricular-pulmonary artery (RV-PA) coupling index (TAPSE/mPAP).

--To evaluate the predictive value of right ventricular (RV) echocardiographic parameters for a positive bubble test in patients with liver cirrhosis

Table 1: Distribution of patients with liver cirrhosis according to socio-demographic characteristics including age and sex. Mean age of patients was (54.92 ± 11.04) years. Older patient was 72.0 years and younger patient was 35.0 years. Patients with age (< 50.0 years) represent only 7 patients (28.0%). More than half of patients were males (N=13, 52.0%).

Table 1: Distribution of patients with liver cirrhosis according to socio-demographic characteristics (N=25)

Figure 3.1: Distribution of patients with liver cirrhosis according to bubble test  including (positive and negative). Patients with positive bubble test represent only 7 patients (28.0%) and patients with negative bubble test represent 18 patients (72.0%).

Figure 3.1 : Distribution of patients with liver cirrhosis according to bubble test (N=25)

Figure 3.2 : Distribution of patients with liver cirrhosis according to echocardiographic parameters  including (high probability ,low probability ). Patients with  high probability  represent only 8 patients (32.0%) and patients with low probability  represent 17 patients (68.0%).

Figure 3.2: Distribution of patients with high probability of POPHT  according to echocardiographic parameters .(N=25)

Table 2: The comparison between patients with liver cirrhosis and control group according to socio-demographic characteristics including age and sex. There was no significant mean differences of age between patients with liver cirrhosis in comparison to control group. There was no significant association between liver cirrhosis and sex of patient.

Table 2: The comparison between patients with liver cirrhosis and control group according to socio-demographic characteristics (N=50)

- The mean differences of Right Atrial Volume Index (RAVI) and right atrial area (cm²) according to study group including (liver cirrhosis and control group). There was significant mean elevation of Right Atrial Volume Index (RAVI) and right atrial area (cm²) among patients with liver cirrhosis in comparison to control group. As showed in Figure  (3.3, 3.4) 

Figure 3.3: Significant mean elevation of Right Atrial Volume Index (RAVI) among patients with liver cirrhosis in comparison to control group (P=0.009*)

Figure 3.4: Significant mean elevation of Right atrial area (cm²) among patients with liver cirrhosis in comparison to control group (P=0.031*)

Table 3: The mean differences of echocardiographic markers including (TAPSE  (mm), FAC (%), S`1, S`2, RV Basal (mm), RV Mid (mm) and RV Length (mm)  according to study group including (liver cirrhosis and control group). There was significant mean elevation of TAPSE  (mm), RV Basal (mm) and RV Mid (mm) among patients with liver cirrhosis in comparison to control group.

Table 3: : The mean differences of echocardiographic markers according to study group (N=50)

Figure 3.5: Significant mean elevation of RV Basal (mm) and RV Mid (mm) among patients with liver cirrhosis in comparison to control group (P<0.001* and P=0.018*)

- The mean differences of  mPAP (mmHg), TAPSE / mPAP  according to study group including (liver cirrhosis and control group). There was significant mean elevation of mPAP (mmHg)  among patients with liver cirrhosis in comparison to control group. There was significant mean reduction of TAPSE / mPAP among patients with liver cirrhosis in comparison to control group.

. As showed in Figure  (3.6 , 3.7 ) .

Figure 3.6: Significant mean elevation of mPAP (mmHg) among patients with liver cirrhosis in comparison to control group (P<0.001* )

Figure 3.7: Significant mean reduction of TAPSE / mPAP among patients with liver cirrhosis in comparison to control group (P<0.001*)

Table 4: The correlation between age of patient (years) and study markers including (TAPSE / mPAP ) among patients with Liver cirrhosis. There was significant negative linear correlation between age of patient (years) and TAPSE / mPAP among patients with liver cirrhosis

Table 4: The mean differences of TAPSE / mPAP and TAPSE / PASP according to sex of patient with liver cirrhosis (N=25)

Table 5: The correlation between Right Atrial Volume Index and study markers including (TAPSE /mPAP ) among patients with Liver cirrhosis. There was  no significant  correlation between Right Atrial Volume Index and TAPSE / mPAP  among patients with liver cirrhosis

Table 5: The correlation between age of patient and study markers including (TAPSE / MPAP ) among patients with Liver cirrhosis (N=25)

Liver cirrhosis is usually associated with complex cardio-pulmonary alterations that occur due to hyper dynamic circulation, pulmonary vascular changes, and a intra-pulmonary shunt, all of which may affect the right side of the heart. Recently non-invasive echocardiographic parameters have been useful for assessing the  Right ventricular – pulmonary artery (RV-PA) coupling index as a  marker of RV adaption to pulmonary vascular load  in cirrhotic patients. In our  analysis, we found that 28% of patients with liver cirrhosis have a positive bubble test, characterized by an appearance of delayed micro-bubbles of agitated saline on the left side of the heart after six cardiac cycles following  Right atrial opacification, suggesting intra-pulmonary vascular dilatation (IPVD). The findings demonstrate the existence of intra-pulmonary vascular dilatation (IPVD), resulting from elevated production of vasodilators, such as nitric oxide, in the context of liver cirrhosis. The vascular alterations result in a ventilation-perfusion imbalance and an intra-pulmonary shunt. However, IPVD alone does not confirm the diagnosis of hepato-pulmonary syndrome (HPS), which necessitates the evaluation of arterial hypoxemia using arterial blood gas analysis (ABG). These findings are consistent with Santos et al. (2024 ) in which 32% of patients demonstrated IPVD  {25}, potentially advancing to HPS.  While  Verstraeten  et al. (2026 )  documented a prevalence of Hepato-pulmonary Syndrome (HPS) of roughly 17% among patients referred for liver transplantation. {26}. The relatively high prevalence identified in this study may be related to the use of contrast echocardiography without arterial blood gas measurements to diagnose arterial hypoxemia.  Moreover, contrast echocardiography is a highly sensitive diagnostic technique for detecting subclinical IPVD .

Dzikowska-Diduch et al. (2024 )  finding was  supports  that IPVD may manifest without hypoxemia as an initial phase of pulmonary vascular involvement in cirrhotic patients {27} .

Porto-pulmonary hypertension is a type of pulmonary hypertension linked  with  portal hypertension that results from   liver dysfunction, which reduces the hepatic  clearance of vasoactive agents like endothelin, serotonin, and inflammatory mediators. These substances induced vasoconstriction and endothelial remodeling, thereby elevating PVR and mPAP and increasing RV afterload. In our study, the prevalence of suspected   Porto-pulmonary hypertension                ( POPHT) in patients with liver cirrhosis was 32%, based  on echocardiographic measures.  Huang Ds et al. (2026 ) and Gupta A et al. (2022) , they were found this rate  ranged from 1.6% to 9.3%, where the diagnosis was confirmed by  right heart catheterization RHC {28,29}.

Our findings are close to  Kumar A .et al. (2024 )  that reporting a prevalence of 29.5% when  echocardiography is used as a screening modality {30} . The similarities and differences between our results and earlier studies support the utility of echocardiography as a screening modality for identifying suspected subclinical Porto-pulmonary hypertension in patients with liver cirrhosis; however, the echocardiographic findings may overestimate the prevalence compared with  right heart catheterization, which remains the cornerstone diagnostic method for POHT. However, this outcome may indicate the sensitivity of non-invasive echocardiographic examination in detecting the potential for subclinical pulmonary vascular alterations, suggestive of POPHT  rather than definitively  confirming  the diagnosis via right heart catheterization.

Our analysis , revealed   RAA and RAVI parameters were significantly increased in patients with liver cirrhosis, which  may reflected right atrial remodeling and dilation .Theses finding may related to chronic hemodynamic alteration that associated with liver cirrhosis, including increased right side filling pressures and possible  pulmonary vascular changes . Consequently, a persistent increase in R.V  pressure  may lead to backward transmission pressure and progression to RA, resulting in RA dilatation and elevated  right atrial pressure RAP  , similar  observation was revealed in the study by Gupta A et al. (2022) , who reported increased pulmonary artery pressure  and echocardiographic manifestation of right sided involvement in cirrhotic patient with POPHT  {28} .

These findings in line with  observation  by  Zhang K et al.  study that documented the effect of POPHT on RA, including remodeling, chamber dilatation in patient with end stage liver cirrhosis  {31} .

Furthermore, patients with liver cirrhosis usually have hyper dynamic circulation, with systemic vasodilation, elevated cardiac output, and increased venous return to the atrium. These hemodynamic changes increase R.V. preload linked to pulmonary vascular alterations, resulting in right ventricular remodeling prior to affecting right ventricular systolic function.

This pathophysiology correlates with our findings: RV dimensions were markedly greater in patients with liver cirrhosis compared to controls. Although Fractional area changes  FAC is an indicator of RV systolic function, it remained preserved ,not  significant (P values = 0.318) . In addition : we observed that RV S′ displayed no significant difference between the studied groups.( P=0.145). In contrast, Nasr FM et al.  ( 2015 ) .observed significantly increased tricuspid annular S′ velocity in cirrhotic patients, which may be due to the hyper-dynamic circulation and increased cardiac output that occur with liver cirrhosis. {32} .. And ,In line with Zhang K et al. (2019 ) study , that founded the  right ventricular remodeling  in patients with end stage liver cirrhosis  have preserved systolic function was reported. {30}

Whereas Enenche AA et al. (2024 )  research documented RV dilation and remodeling associated with a significant reduction in FAC. {33 }

This may be explained by right ventricular structural changes that develop before  systolic dysfunction becomes obvious. This disparity may be explained by variability in disease severity, disease duration, patient selection and the degree of concomitant hemodynamic changes between the studied groups .

Overall, these analyses suggest that RV dilatation in cirrhotic patients manifests as an early sub-clinical compensatory response  to  hyper-dynamic circulation and altered pulmonary  hemodynamics  rather than established R.V. failure. 

In our study, we observed a significantly increase in Tricuspid annular plane systolic excursion  TAPSE  among cirrhotic patients, which may have resulted from hyper-dynamic circulation, leading to systemic vasodilation and increased venous return, thereby augmenting RV preload and increasing longitudinal RV motion associated with liver cirrhosis.

This result coincides with Celiker Guler E et al. (2023 )  study that documented sub-clinical changes in RV performance due to hyper-dynamic circulation and altered pulmonary hemo-dynamics {34} .

 In  the present  study  , this ratio of  TAPSE / mPAP  was  statically significantly reduced (the ability of RV  contractility to adapt to  increased pulmonary afterload).  Fortuni F et al. (2023 ) studies have demonstrated the clinical importance of the  TAPSE / mPAP ratio as a surrogate marker of the right ventricular- pulmonary arterial coupling index, reflecting the ability of R.V. contractility relative to PA load {35}.

Importantly Silic V et al . (2025 ) . were found  mPAP may be elevated in patients with liver cirrhosis secondary to hyper-dynamic circulation, increased cardiac output  , and changes in pulmonary hemodynamics, which may not necessarily represent true pulmonary hypertension {36}.   Therefore, the TAPSE/mPAP ratio may provide a more comprehensive assessment of R.V. adaptation rather than depend on isolated conventional parameters alone.  Accordingly, this ratio serves as a sign for early RV-PA uncoupling and sub-clinical cardio-pulmonary involvement in patients with liver cirrhosis. Since it's a newly emerging parameter ,the studies  about this ratio are limited globally, especially regarding Porto-pulmonary hypertension in liver cirrhosis   and there are no similar studies within the country and region to compare with.

The  current study , show significant negative  correlation between age and the TAPSE/mPAP ratio, which may indicate a gradual deterioration in right ventricular-pulmonary artery coupling with advancing age. This can be attributed  by age-associated alterations in cardio-pulmonary hemodynamics, including increasing pulmonary vascular stiffness and a gradual decrease in right ventricular functional reserve.  Furthermore :  it is related to the chronic hemodynamic alterations associated with prolonged hepatic cirrhosis. Also ; we observed no correlation between  TAPSE/mPAP ratio and Right atrial volume index

At present ,there are no studies support or against this correlation in  patients have Porto-pulmonary hypertension.                   

In the present study, there were no statistically significant differences in age and sex distribution between cirrhotic patients and control group . This similar demographic finding across groups reduces the potential confounding effects of age- and sex-related cardio-pulmonary vascular changes in cirrhotic patients on echocardiographic findings.

Therefore, all echocardiographic findings are more likely related to the pathophysiological effects of liver cirrhosis rather than to demographic differences between the studied group.

- This research supports  the  role of echocardiographic study as a noninvasive  tool for detecting early sub-clinical  cardio-pulmonary abnormalities and  identifying cirrhotic patients who may benefit from further diagnostic evaluation for HPS , POPHT . 

-.Elevated TAPSE  in patients with liver cirrhosis may reflect  hyper-dynamic circulation, which could raise suspicion of HPS, especially in patients presenting hypoxemia or related clinical symptoms. Thus , further evaluation with an agitated  contrast saline  echocardiographic  (bubbles test  ) may be warranted .

-Right-sided  dilation may raise suspicion of POPHT  , which occurred due to pressure overload in a patient with liver cirrhosis  , requiring further assessment of pulmonary hemodynamics.

-TAPSE /mPAP was a useful non-invasive echocardiographic  marker for  assessment of the right ventricular –pulmonary arterial  coupling index;  its reduction represented  RV –PA uncoupling. - TAPSE /mPAP was associated with advancing age, which may contribute to the gradual deterioration of the R.V-P.A. coupling index in elderly patients.

LIMITATIONS :

Limited  study time and small  number of available patients  , which impacted  patient recruitment  and data collection; thus , the findings may not represent the entire population of patients with liver cirrhosis and should be interpreted with caution.

-Limited previous research is available in the country or neighboring countries that addresses the RV-PA coupling index (TAPSE/mPAP ratio) in patients with liver cirrhosis, to compare with the present findings. 

-A limited invasive hemodynamic method (RHC) to confirm pulmonary hypertension and R.V-P.A coupling could not be established.

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