Magnetic resonance relaxometry of the liver - a new imaging biomarker to assess right heart failure in pulmonary hypertension

Liver T1 Mapping Derived From Cardiac Magnetic Resonance Imaging: A Potential Prognostic Marker in Idiopathic Dilated Cardiomyopathy

BACKGROUND

Hepatic alterations are common aftereffects of heart failure (HF) and ventricular dysfunction. The prognostic value of liver injury markers derived from cardiac MRI studies in nonischemic dilated cardiomyopathy (DCM) patients is unclear.

PURPOSE

Evaluate the prognostic performance of liver injury markers derived from cardiac MRI studies in DCM patients.

STUDY TYPE

Prospective.

POPULATION

Three hundred fifty-six consecutive DCM patients diagnosed according to ESC guidelines (age 48.7 ± 14.2 years, males 72.6%).

FIELD STRENGTH/SEQUENCE

Steady-state free precession, modified Look-Locker inversion recovery T1 mapping and phase sensitive inversion recovery late gadolinium enhancement (LGE) sequences at 3 T.

ASSESSMENT

Clinical characteristics, conventional MRI parameters (ventricular volumes, function, mass), native myocardial and liver T1, liver extracellular volume (ECV), and myocardial LGE presence were assessed. Patients were followed up for a median duration of 48.3 months (interquartile range 42.0-69.9 months). Primary endpoints included HF death, sudden cardiac death, heart transplantation, and HF readmission; secondary endpoints included HF death, sudden cardiac death, and heart transplantation. Models were developed to predict endpoints and the incremental value of including liver parameters assessed.

STATISTICAL TESTS

Optimal cut-off value was determined using receiver operating characteristic curve and Youden method. Survival analysis was performed using Kaplan-Meier and Cox proportional hazard. Discriminative power of models was compared using net reclassification improvement and integrated discriminatory index. P value <0.05 was considered statistically significant.

RESULTS

47.2% patients reached primary endpoints; 25.8% patients reached secondary endpoints. Patients with elevated liver ECV (cut-off 34.4%) had significantly higher risk reaching primary and secondary endpoints. Cox regression showed liver ECV was an independent prognostic predictor, and showed independent prognostic value for primary endpoints and long-term HF readmission compared to conventional clinical and cardiac MRI parameters.

DATA CONCLUSIONS

Liver ECV is an independent prognostic predictor and may serve as an innovative approach for risk stratification for DCM.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY: Stage 2.

Laterality of CT-measured hepatic extracellular volume fraction in patients with chronic thromboembolic pulmonary hypertension

PURPOSE

This study examines the hepatic extracellular volume fraction (ECV) disparity between the left and right lobes (ECV_left and ECV_right) in patients with chronic thromboembolic pulmonary hypertension (CTEPH), its association with right heart catheterization (RHC) metrics, and with intolerance to increased pulmonary hypertension (PH)-targeted medication dosages.

METHODS

We retrospectively analyzed 72 CTEPH-diagnosed patients who underwent equilibrium-phase abdominal dual-energy CT (DECT) and RHC. Hepatic ECVs, derived from DECT's iodine maps using circular regions of interest in the liver and aorta, were correlated with RHC parameters via Spearman's rank correlation and lobe differences through the Wilcoxon signed-rank test. Logistic regression assessed cases with ECV_left exceeding ECV_right by > 0.05, while receiver operating characteristic curve analysis gauged ECVs' predictive power for medication intolerance.

RESULTS

Of the 72 patients (57 females; median age 69), ECV_total (0.24, IQR 0.20-0.27) moderately correlated with RHC parameters (rs = 0.28, -0.24, 0.3 for mean pulmonary arterial pressure, cardiac index [CI], and pulmonary vascular resistance index, respectively). ECV_left significantly surpassed ECV_right (0.25 vs. 0.22, p < 0.001), with a greater ECV_left by > 0.05 indicating notably lower CI (p < 0.001). In 27 patients on PH medication, ECV_left effectively predicted medication intolerance (AUC = 0.84).

CONCLUSION

In CTEPH patients, hepatic ECV correlated with RHC metrics, where elevated left lobe ECV suggested reduced CI and potential medication intolerance.

Use of Real-Time Cine MRI to Assess the Respirophasic Variation of the Inferior Vena Cava-Proof-of-Concept and Validation Against Transthoracic Echocardiography

BACKGROUND

In clinical practice, the right heart filling status is assessed using the respirophasic variation of the inferior vena cava (IVC) assessed by transthoracic echocardiography (TTE) showing moderate correlations with the catheter-based reference standard.

PURPOSE

To develop and validate a similar approach using MRI.

STUDY TYPE

Prospective.

POPULATION

37 male elite cyclists (mean age 26 ± 4 years).

FIELD STRENGTH/SEQUENCE

Real-time balanced steady-state free-precession cine sequence at 1.5 Tesla.

ASSESSMENT

Respirophasic variation included assessment of expiratory size of the upper hepatic part of the IVC and degree of inspiratory collapse expressed as collapsibility index (CI). The IVC was studied either in long-axis direction (TTE) or using two transverse slices, separated by 30 mm (MRI) during operator-guided deep breathing. For MRI, in addition to the TTE-like diameter, IVC area and major and minor axis diameters were also assessed, together with the corresponding CIs.

STATISTICAL TESTS

Repeated measures ANOVA test with Bonferroni correction. Intraclass correlation coefficient (ICC) and Bland-Altman analysis for intrareader and inter-reader agreement. A P value <0.05 was considered statistically significant.

RESULTS

No significant differences in expiratory IVC diameter were found between TTE and MRI, i.e., 25 ± 4 mm vs. 25 ± 3 mm (P = 0.242), but MRI showed a higher CI, i.e., 76% ± 14% vs. 66% ± 14% (P < 0.05). As the IVC presented a noncircular shape, i.e., major and minor expiratory diameter of 28 ± 4 mm and 21 ± 4 mm, respectively, the CI varied according to the orientation, i.e., 63% ± 27% vs. 75% ± 16%, respectively. Alternatively, expiratory IVC area was 4.3 ± 1.1 cm2 and showed a significantly higher CI, i.e., 86% ± 14% than diameter-based CI (P < 0.05). All participants showed a CI >50% with MRI versus 35/37 (94%) with TTE. ICC values ranged 0.546-0.841 for MRI and 0.545-0.704 for TTE.

CONCLUSION

Assessment of the respirophasic IVC variation is feasible with MRI. Adding this biomarker may be of particular use in evaluating heart failure patients.

LEVEL OF EVIDENCE

1 TECHNICAL EFFICACY STAGE: 2.

A novel clinical prediction scoring system of high-altitude pulmonary hypertension

Background

High-altitude pulmonary hypertension (HAPH) is a common disease in regions of high altitude where performing right heart catheterization (RHC) is challenging. The development of a diagnostic scoring system is crucial for effective disease screening.

Methods

A total of 148 individuals were included in a retrospective analysis, and an additional 42 residents were prospectively enrolled. We conducted a multivariable analysis to identify independent predictors of HAPH. Subsequently, we devised a prediction score based on the retrospective training set to anticipate the occurrence and severity of HAPH. This scoring system was further subjected to validation in the prospective cohort, in which all participants underwent RHC.

Results

This scoring system, referred to as the GENTH score model (Glycated hemoglobin [OR = 4.5], Echocardiography sign [OR = 9.1], New York Heart Association-functional class [OR = 12.5], Total bilirubin [OR = 3.3], and Hematocrit [OR = 3.6]), incorporated five independent risk factors and demonstrated strong predictive accuracy. In the training set, the area under the curve (AUC) values for predicting the occurrence and severity of HAPH were 0.851 and 0.832, respectively, while in the validation set, they were 0.841 and 0.893. In the validation set, GENTH score model cutoff values of ≤18 or >18 points were established for excluding or confirming HAPH, and a threshold of >30 points indicated severe HAPH.

Conclusions

The GENTH score model, combining laboratory and echocardiography indicators, represents an effective tool for distinguishing potential HAPH patients and identifying those with severe HAPH. This scoring system improves the clinical screening of HAPH diseases and offers valuable insights into disease diagnosis and management.

Novel Liver Injury Phenotypes and Outcomes in Pulmonary Arterial Hypertension

Background

Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are disorders of the pulmonary vasculature that cause right ventricular dysfunction. Systemic consequences of right ventricular dysfunction include damage to other solid organs, such as the liver. However, the profiles and consequences of hepatic injury due to PAH and CTEPH have not been well-studied.

Methods

We aimed to identify underlying patterns of liver injury in a cohort of PAH and CTEPH patients enrolled in 15 randomized clinical trials conducted between 1998 and 2012. We used unsupervised machine learning to identify liver injury clusters in 13 trials and validated the findings in two additional trials. We then determined whether these liver injury clusters were associated with clinical outcomes or treatment effect heterogeneity.

Results

Our training dataset included 4,219 patients and our validation dataset included 1,756 patients with complete liver laboratory panels (serum total bilirubin, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, and albumin). Using k-means clustering paired with factor analysis, we identified four unique liver phenotypes (no liver injury, hepatocellular injury, cholestatic injury, and combined injury patterns). Patients in the cholestatic injury liver cluster had the shortest time to clinical worsening and highest chance of worsening World Health Organization functional class. Randomization to the experimental arm was associated with a transition to healthier liver clusters compared to randomization to the control arm. The cholestatic injury group experienced the greatest placebo-corrected treatment benefit in terms of six-minute walk distance.

Conclusions

Liver injury patterns were associated with adverse outcomes in patients with PAH and CTEPH. Randomization to active treatment of pulmonary hypertension in these clinical trials had beneficial effects on liver health compared to placebo. The independent role of liver disease (often subclinical) in determining outcomes warrants prospective studies of the clinical utility of liver phenotyping for PAH prognosis and contribution to clinical disease.

Prognostic Value of Hepatic Native T1 and Extracellular Volume Fraction in Patients with Pulmonary Arterial Hypertension

Background

Right heart failure may lead to impaired liver perfusion and venous congestion, resulting in different extents of liver fibrosis. However, whether hepatic tissue deterioration determined by native T1 mapping and extracellular volume fraction using cardiac magnetic resonance imaging is associated with poor outcomes in patients with pulmonary arterial hypertension remains unclear.

Methods and Results

A total of 131 participants with pulmonary arterial hypertension (mean age, 36±13 years) and 64 healthy controls (mean age, 44±18) between October 2013 and December 2019 were prospectively enrolled. Hepatic native T1 and extracellular volume fraction values were measured using modified Look–Locker inversion recovery T1 mapping sequences. The primary end point was all‐cause mortality; the secondary end point was all‐cause mortality and repeat hospitalization attributable to heart failure. Cox regression models and Kaplan–Meier survival analysis were used to identify the association between variables and clinical outcome. During a median follow‐up of 34.5 months (interquartile range: 25.3–50.8), hepatic native T1 (hazard ratio per 30‐ms increase, 1.22 [95% CI, 1.07–1.39]; P =0.003) and extracellular volume fraction (hazard ratio per 3% increase, 1.18 [95% CI, 1.04–1.34]; P =0.010) values were associated with a higher risk of death. In the multivariate Cox model, hepatic native T1 value (hazard ratio per 30‐ms increase, 1.15 [95% CI, 1.04–1.27]; P =0.009) remained as an independent prognostic factor for the secondary end point.

Conclusions

Hepatic T1 mapping values were predictors of adverse cardiovascular events in participants with pulmonary arterial hypertension and could be novel imaging biomarkers for poor prognosis recognition.