Assessment of portal hypertension in humans

Splenic T1ρ as a noninvasive biomarker for portal hypertension

BACKGROUND

There is a need for noninvasive methods for the diagnosis and monitoring of portal hypertension (PH).

PURPOSE

To 1) assess the correlation of liver and spleen T₁ and T_1ρ measurements with portal pressures in patients with chronic liver disease, and 2) to compare the diagnostic performance of the relaxation parameters with radiological assessment of PH.

STUDY TYPE

Prospective.

SUBJECTS

Twenty-five patients (M/F 16/9, mean age 56 years, range 21-78 years) undergoing portal pressure (hepatic venous pressure gradient [HVPG]) measurements.

FIELD STRENGTH/SEQUENCE

1.5T abdominal MRI scan, including T_1ρ and T₁ mapping.

ASSESSMENT

Liver and spleen T_1ρ and T₁ , radiological PH score, and (normalized) spleen length were evaluated.

STATISTICAL TESTS

Spearman correlation of all MRI parameters with HVPG was assessed. The diagnostic performance of the assessed parameters for prediction of PH (HVPG ≥5 mmHg) and clinically significant PH (CSPH, HVPG ≥10 mmHg) was determined by receiver operating characteristic (ROC) analysis.

RESULTS

The mean HVPG measurement was 7.8 ± 5.3 mmHg (PH, n = 18 [72%] including CSPH, n = 9 [36%]). PH score, (normalized) spleen length and spleen T_1ρ significantly correlated with HVPG, with the strongest correlation found for spleen T_1ρ (r = 0.613, P = 0.001). Spleen T_1ρ was the only parameter that showed significant diagnostic performance for assessment of PH (area under the curve [AUC] 0.817, P = 0.015) and CSPH (AUC = 0.778, P = 0.024). Normalized spleen length also showed significant diagnostic performance for prediction of CSPH, with a slightly lower AUC (= 0.764, P = 0.031). The radiological PH score, T_1ρ and T₁ of the liver and T₁ of the spleen, did not show significant diagnostic performance for assessment of CSPH (P > 0.075).

DATA CONCLUSION

Spleen T_1ρ showed a significant correlation with portal pressure and showed improved diagnostic performance for prediction of CSPH compared to radiological assessment. These initial results need confirmation in a larger cohort.

LEVEL OF EVIDENCE

1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;52:787-794.

Noninvasive prediction of portal pressure with MR elastography and DCE-MRI of the liver and spleen: Preliminary results

BACKGROUND

Portal hypertension (PH), defined by hepatic venous pressure gradient (HVPG) ≥5 mmHg and clinically significant PH, defined by HVPG ≥10 mmHg, are complications of chronic liver disease.

PURPOSE

To assess the diagnostic performance of MR elastography (MRE) and dynamic contrast-enhanced MRI (DCE-MRI) of the liver and spleen for the prediction of PH and clinically significant PH, in comparison with a qualitative PH imaging scoring system.

STUDY TYPE

IRB-approved prospective study.

POPULATION

In all, 34 patients with chronic liver disease who underwent HVPG measurement.

FIELD STRENGTH/SEQUENCE

1.5/3T examination including 2D-GRE MRE (n = 33) and DCE-MRI of the liver/spleen (n = 28).

ASSESSMENT

Liver and spleen stiffness were calculated from elastogram maps. DCE-MRI was analyzed using model-free parameters and pharmacokinetic modeling. Two observers calculated qualitative PH imaging scores based on routine images.

STATISTICAL TESTS

Imaging parameters were correlated with HVPG. Receiver operating characteristic (ROC) analysis was performed for prediction of PH and clinically significant PH.

RESULTS

There were significant correlations between DCE-MRI parameters (liver time-to-peak, r = 0.517 / P = 0.006, liver distribution volume, r = 0.494 / P = 0.009, liver upslope, r = -0.567 / P = 0.002), liver stiffness (r = 0.478 / P = 0.016), PH imaging score (r = 0.441 / P = 0.009), and HVPG. ROC analysis provided significant area under the ROC (AUROCs) for PH (liver upslope 0.765, liver stiffness 0.809, spleen volume/diameter 0.746-0.731, PH imaging score 0.756) and for clinically significant PH (liver and spleen perfusion parameters 0.733-0.776, liver stiffness 0.742, PH imaging score 0.742). The ratio of liver stiffness to liver upslope had the highest AUROC for diagnosing PH (0.903) and clinically significant PH (0.785).

DATA CONCLUSION

These preliminary results suggest that the combination of liver stiffness and perfusion metrics provide excellent accuracy for diagnosing PH, and fair accuracy for clinically significant PH. Combined MRE and DCE-MRI outperformed qualitative imaging scores for prediction of PH.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1091-1103.

Simultaneous measurement of hepatic and splenic stiffness using MR elastography: preliminary experience

PURPOSE

To compare MR elastography (MRE) using a single and a dual driver excitation for the quantification of hepatic and splenic stiffness (HS and SS), and to investigate the performance of HS and SS measured with single or dual driver excitation for the detection of liver cirrhosis in subjects with liver disease.

PATIENTS AND METHODS

This prospective HIPAA compliant and IRB approved study involved 49 subjects who underwent MRE at 3.0T, comparing three different acquisition methods (single driver on the liver, single driver on the spleen and dual driver acoustic excitation). A Mann-Whitney test was used to assess changes in stiffness values. Bland-Altman analysis was used to compare single and dual driver configurations for each organ. Performance for detection of liver cirrhosis was assessed using ROC analysis. Pearson correlation was used to estimate the dependence of HS and SS on spleen size.

RESULTS

There were 40 noncirrhotic and 9 cirrhotic patients. There was good agreement between stiffness values measured with a single or a dual driver (Bland-Altman limits of agreement -14.3 % to 18.9 % and -18.1 % to 29.7 %, CV 6.4 % and 9.4 %, for HS and SS. respectively). HS and SS were higher in subjects with liver cirrhosis (p < 0.001), with excellent detection performance (AUROC range 0.87-0.93). SS correlated strongly with spleen size (r = 0.69, p < 0.001), while HS showed weak correlation (r = 0.38, p = 0.006).

CONCLUSION

Using a dual acoustic driver configuration, hepatic and splenic stiffness can be simultaneously estimated with good concordance with single driver measurement.

Stroke volume response to liver graft reperfusion stress in cirrhotic patients

INTRODUCTION

In patients with advanced cirrhosis, stressful stimuli may reveal a silent reduced cardiac performance. During liver transplantation (LT), graft reperfusion strongly stresses the heart and may unmask latent myocardial dysfunction.

AIM

The objective of this study was to assess heart response to acutely increased preload after liver graft reperfusion and correlate this response with preoperative data and outcome.

METHODS

Preoperative clinical, echocardiographic, and hemodynamic data, and patient outcome were retrospectively recorded for 235 liver recipients who had no known cardiac disease. Myocardial dysfunction was defined as less than 10 % increase of stroke volume after graft reperfusion (non-responder).

RESULTS

We found 84 (35.7 %) non-responder patients. The non-responders showed higher Model for end-stage liver disease scores (p = 0.046), left atrial diameter (LAD) (p = 0.040), hepatic vein pressure gradient (p = 0.055), and hyperdynamic state than responders. The percentages of patients with hyponatremia (p = 0.048) and alcohol etiology (p = 0.025) were also higher among non-responders. Independent predictors of inadequate cardiac response in the multivariate analysis were low preoperative systemic vascular resistance (SVRI) [odds ratio (OR) 3.09, 95 % CI 1.15-4.82; p = 0.027] and enlargement of LAD (OR 2.08, 95 % CI 1.49-2.74; p = 0.044). Non-response was associated with higher rates of early cardiovascular events [hazard ratio (HR) 2.84, 95 % CI 1.09-4.22; p = 0.039] and higher length of intensive care unit stay (p = 0.038). No differences were found in 1-year survival rates.

CONCLUSIONS

Latent cardiac dysfunction among LT recipients, considered to be abnormal stroke volume response to unclamping of portal vein, is very prevalent. SVRI and LAD were independent predictors of inadequate responses. This condition deserves special attention since it may aggravate the early postoperative course of LT.

Phenotypic polymorphism of haptoglobin: a novel risk factor for the development of infection in liver cirrhosis

The α-chain alleles 1 and 2 of haptoglobin (Hp) molecule account for three phenotypes, which have biologically important differences in their antioxidant, scavenging, and immunomodulatory properties and may thereby influence the course of inflammatory diseases. A follow-up observational study was conducted to assess the association between haptoglobin phenotype and the development of clinically significant bacterial infections in patients with liver cirrhosis. Sera of 336 patients with liver cirrhosis of various etiologies and 384 healthy subjects were investigated. Haptoglobin phenotypes were determined by gel electrophoresis and assigned corresponding genotype. Haptoglobin phenotype distributions of patients and controls was similar (Hp1-1: 10.7% vs 11.5%, Hp2-1: 47.9% vs 46.1% and Hp2-2: 41.4% vs 42.4%). The probability of clinically significant bacterial infections was calculated for each haptoglobin phenotype (Hp1-1: 50.0%, Hp2-1: 36.0% and Hp2-2: 26.6%, p = 0.039). In a logistic regression analysis, Hp1-1 phenotype (p = 0.015, OR: 2.74, 95% CI: 1.22-6.13), Child-Pugh stage (p = 0.038, OR: 1.40, 95% CI: 1.02-1.91) and presence of co-morbidities (p < 0.001, OR: 2.64, 95% CI: 1.63-4.27) were independently associated with infections. In a Cox regression analysis, Hp1-1 phenotype (p = 0.014), Child-Pugh stage C (p < 0.001), and presence of co-morbidities (p = 0.004) were associated with time to first infectious episode. Phenotypic haptoglobin polymorphism was independent predictor for risk and time to first clinically significant bacterial infectious episode.

Acute and long-term effects of inhaled iloprost in portopulmonary hypertension

Portopulmonary hypertension (PoPH) is a serious condition without an established treatment. Drugs used to treat pulmonary hypertension may have detrimental effects on portal hypertension. This study was designed to assess in patients with PoPH the acute effects of inhaled iloprost (iILO) on pulmonary and hepatic hemodynamics and to evaluate the clinical outcome after 12 months of treatment. We conducted 2 separate studies. In the first one, 21 patients with PoPH were acutely tested with 2.8 microg of iILO. Pulmonary and hepatic hemodynamics were assessed at the baseline and through 60 minutes after iILO. In the second one, we retrospectively evaluated 12 patients treated with iILO (30 microg/day) for more than 1 year. The 6-minute walk distance (6MWD), functional class (FC), and echocardiogram were analyzed at the baseline and after 12 months of treatment. In the acute study, iILO rapidly reduced pulmonary artery pressure (PAP; -16% + or - 8%, P < 0.001) and pulmonary vascular resistance (-18% + or - 14%, P < 0.001). The cardiac output did not change initially but decreased after 30 minutes. The hepatic venous pressure gradient (HVPG) and hepatic blood flow did not vary through the study. Pulmonary vasodilation induced by iILO was inversely related to HVPG. In the long-term evaluation, iILO improved FC by 1 or more in 7 patients (P = 0.04) and increased 6MWD by 67 + or - 59 m at 12 months (P < 0.001). No change in systolic PAP was observed. Two patients died because of hepatic complications, and 4 additional patients presented clinically significant events that were related to hepatic disease in 2 and worsening of pulmonary hypertension in 2. We conclude that in patients with PoPH, iILO produces rapid and selective pulmonary vasodilation without altering the hepatic hemodynamics. Its long-term use may provide sustained improvements in symptoms and exercise tolerance in some patients with PoPH. A randomized, controlled trial is warranted to establish its clinical role in this serious condition.

A novel microbubble construct for intracardiac or intravascular MR manometry: a theoretical study

It has been demonstrated that gas-filled microbubble contrast agents, based on their volume changes, can serve as pressure probes in an MR field. It was recently reported that such an MR-based pressure measurement with microbubbles at 1.5 T must make use of microbubbles that have a volumetric magnetic susceptibility difference with the blood of at least 34 ppm in SI units. In this work, we show through analytical approximations and numerical simulations that such a microbubble formulation can be achieved by coating typical lipid-shelled microbubbles with particles of high dipole moment. Through finite-element simulations we demonstrate that the effective volumetric magnetic susceptibility of a coated microbubble is dependent on the radius, the shell volume fraction and the magnetic susceptibility of the particulates on the shell. Our calculations suggest that a suitable microbubble formulation which will be MR-sensitive to small pressure changes at 1.5 T must be 2-3 microm in radius and be uniformly coated with single-domain magnetic nanoparticles, such as magnetite, at shell volume fractions below 5%.

Hemodynamic analysis of esophageal varices in patients with liver cirrhosis using color Doppler ultrasound

AIM: To study the portal hemodynamics and their relationship with the size of esophageal varices seen at endoscopy and to evaluate whether these Doppler ultrasound parameters might predict variceal bleeding in patients with liver cirrhosis and portal hypertension.

METHODS: One hundred and twenty cirrhotic patients with esophageal varices but without any previous bleeding were enrolled in the prospective study. During a 2-year observation period, 52 patients who had at least one episode of acute esophageal variceal hemorrhage constituted the bleeding group, and the remaining 68 patients without any previous hemorrhage constituted the non-bleeding group. All patients underwent endoscopy before or after color Doppler-ultrasonic examination, and images were interpreted independently by two endoscopists. The control group consisted of 30 healthy subjects, matched to the patient group in age and gender. Measurements of diameter, flow direction and flow velocity in the left gastric vein (LGV) and the portal vein (PV) were done in all patients and controls using color Doppler unit. After baseline measurements, 30 min after oral administration of 75 g glucose in 225 mL, changes of the diameter, flow velocity and direction in the PV and LGV were examined in 60 patients with esophageal varices and 15 healthy controls.

RESULTS: The PV and LGV were detected successfully in 115 (96%) and 105 (88%) of 120 cirrhotic patients, respectively, and in 27 (90%) and 21 (70%) of 30 healthy controls, respectively. Among the 120 cirrhotic patients, 37 had F1, 59 had F2, and 24 had F3 grade varices. Compared with the healthy controls, cirrhotic group had a significantly lower velocity in the PV, a significantly greater diameter of the PV and LGV, and a higher velocity in the LGV. In the cirrhotic group, no difference in portal flow velocity and diameter were observed between patients with or without esophageal variceal bleeding (EVB). However, the diameter and blood flow velocity of the LGV were significantly higher for EVB (+) group compared with EVB (-) group (P<0.01). Diameter of the LGV increased with enlarged size of varices. There were differences between F1 and F2, F1 and F3 varices, but no differences between F2 and F3 varices (P = 0.125). However, variceal bleeding was more frequent in patients with a diameter of LGV >6 mm. The flow velocity in the LGV of healthy controls was 8.70±1.91 cm/s (n = 21). In patients with liver cirrhosis, it was 10.3±2.1 cm/s (n = 12) when the flow was hepatopetal and 13.5±2.3 cm/s (n = 87) when it was hepatofugal. As the size of varices enlarged, hepatofugal flow velocity increased (P<0.01) and was significantly different between patients with F1 and F2 varices and between patients with F2 and F3 varices. Variceal bleeding was more frequent in patients with a hepatofugal flow velocity >15 cm/s (32 of 52 patients, 61.5%). Within the bleeding group, the mean LGV blood flow velocity was 16.6±2.62 cm/s. No correlation was observed between the portal blood flow velocity and EVB. In all healthy controls, the flow direction in the LGV was hepatopetal, toward the PV. In patients with F1 varices, flow direction was hepatopetal in 10 patients, to-and-fro state in 3 patients, and hepatofugal in the remaining 18. The flow was hepatofugal in 91% patients with F2 and all F3 varices. Changes in diameter of the PV and LGV were not significant before and after ingestion of glucose (PV: 1.41±1.5 cm before and 1.46±1.6 cm after; LGV: 0.57±1.7 cm before and 0.60±1.5 cm after). Flow direction in the LGV was hepatopetal and to-and-fro in 16 patients and hepatofugal in 44 patients before ingestion of glucose. Flow direction changed to hepatofugal in 9 of 16 patients with hepatopetal and to-and-fro blood flow after ingestion of glucose. In 44 patients with hepatofugal blood flow in the LGV, a significant increase in hepatofugal flow velocity was observed in 38 of 44 patients (86%) with esophageal varices. There was a relationship between the percentage changes in flow velocity and the size of varices. Patients who responded excessively to food ingestion might have a high risk for bleeding. The changes of blood flow velocity in the LGV were greater than those in the PV (LGV: 28.3±26.1%, PV: 7.2±13.2%, P<0.01), whereas no significant changes in the LGV occurred before and after ingestion of glucose in the control subjects.

CONCLUSION: Hemodynamics of the PV is unrelated to the degree of endoscopic abnormalities in patients with liver cirrhosis. The most important combinations are endoscopic findings followed by the LGV hemodynamics. Duplex-Doppler ultrasonography has no value in the identification of patients with cirrhosis at risk of variceal bleeding. Hemodynamics of the LGV appears to be superior to those of the PV in predicting bleeding.

Treatment of portal hypertension with NCX-1000, a liver-specific NO donor. A review of its current status

Portal hypertension, a life threatening complication of liver cirrhosis, results from increased intrahepatic resistance and increased portal blood inflow through a hyperdynamic splanchnic system. The increased intrahepatic vascular tone is the result of an enhanced activity of endogenous vasoconstrictors and a deficiency of nitric oxide (NO) release by sinusoidal endothelial cells. These pathophysiological events provide the rational basis for using NO-based therapies for the treatment of portal hypertension. Clinical studies have demonstrated that nitrate therapy results in a significant reduction of portal pressure as assessed by hepatic venous portal gradient but causes vasodilation in both systemic arterial and venous vascular beds, aggravating the progression of the vasodilatory syndrome of cirrhotic patients. For this reason, the ideal drug for the treatment of portal hypertension should act by decreasing intrahepatic vascular resistance, without worsening the splanchnic/systemic vasodilatation. NCX-1000 is the prototype of a family of NO-releasing derivatives of ursodeoxycholic acid (UDCA). These compounds are releasing selectively, from parenchymal and non-parenchymal hepatic cells, biologically active NO into the liver microcirculation with no detectable effect on systemic circulation. Preclinical studies have shown that long- and short-term administration of NCX-1000 to rodents with chronic liver injury protects against the development of portal hypertension and reduces the intrahepatic hyperreactivity to alpha1-adrenoceptor agonists. The finding of increased liver nitrite/nitrate content in NCX-1000-treated animals together with an increase in cGMP levels in their liver homogenates suggests that this nitro-compound behaves as a liver-selective NO donor. In contrast to conventional NO-donors such as isosorbide mono- and di-nitrate, which are also used for primary and secondary prevention of gastrointestinal bleeding, NCX-1000 has no effect on mean arterial pressure in either normal or cirrhotic animals indicating the absence of adverse systemic effect. In summary, these data suggest that NCX-1000 may provide a novel therapy for the treatment of patients with portal hypertension.

Screening in liver disease: report of an AASLD clinical workshop

This report summarizes an AASLD Clinical Workshop that was presented at Digestive Diseases Week 2003 on screening in liver diseases. As newer diagnostic tests become available, many liver diseases and complications of liver disease can be detected at an early asymptomatic stage. In many cases, early detection can lead to earlier treatment and an improved outcome. However, screening for liver diseases in asymptomatic persons has the potential for adverse consequences, including discrimination and stigmatization. The cost of screening programs is significant, and access to screening tests varies in different countries. Future screening programs require careful planning and implementation to balance the benefits, risks, and cost-effectiveness. This review outlines the concepts of screening and their application to a broad range of liver diseases.

Nitric oxide and portal hypertension: a nitric oxide-releasing derivative of ursodeoxycholic acid that selectively releases nitric oxide in the liver

Portal hypertension, a common consequence of chronic liver diseases, is directly responsible for most complications of cirrhosis. In liver microcirculation, nitric oxide is considered a major fine tuner of vascular tone by counterbalancing vasoconstrictors (sympathetic nervous activity, the renin-angiotensin system, and endothelin-1) in normal and cirrhotic livers. The deficiency of endothelial nitric oxide release is a key factor in the hemodynamic abnormalities associated with the dynamic component of portal hypertension. Conventional nitric oxide donors release nitric oxide into the blood stream, causing systemic hypotension and progression of vasodilatory syndrome in cirrhotic patients. NCX1000 is a nitric oxide-releasing derivative of ursodeoxycholic acid-derived compounds, being capable of selectively releasing nitric oxide into the liver circulation. Administration of NCX1000 to portal hypertensive rats decreases intrahepatic resistance providing a novel therapy for the treatment of portal hypertension.