Emerging role of cardiovascular magnetic resonance imaging in the management of pulmonary hypertension

The Right Ventricle in Pulmonary Hypertension

The right ventricle plays a pivotal role in patients with pulmonary hypertension (PH). Its adaptation to pressure overload determines a patient's functional status as well as survival. In a healthy situation, the right ventricle is part of a low pressure, high compliance system. It is built to accommodate changes in preload, but not very well suited for dealing with pressure overload. In PH, right ventricular (RV) contractility must increase to maintain cardiac output. In other words, the balance between the degree of RV contractility and afterload determines stroke volume. Hypertrophy is one of the major hallmarks of RV adaptation, but it may cause stiffening of the ventricle in addition to intrinsic changes to the RV myocardium. Ventricular filling becomes more difficult for which the right atrium tries to compensate through increased stroke work. Interaction of RV diastolic stiffness and right atrial (RA) function determines RV filling, but also causes vena cava backflow. Assessment of RV and RA function is critical in the evaluation of patient status. In recent guidelines, this is acknowledged by incorporating additional RV parameters in the risk stratification in PH. Several conventional parameters of RV and RA function have been part of risk stratification for many years. Understanding the pathophysiology of RV failure and the interactions with the pulmonary circulation and right atrium requires consideration of the unique RV anatomy. This review will therefore describe normal RV structure and function and changes that occur during adaptation to increased afterload. Consequences of a failing right ventricle and its implications for RA function will be discussed. Subsequently, we will describe RV and RA assessment in clinical practice.

Risk Stratification in Pulmonary Arterial Hypertension, Update and Perspectives

Risk stratification in pulmonary arterial hypertension (PAH) is crucial in assessing patient prognosis. It serves a prominent role in everyday patient care and can be determined using several validated risk assessment scores worldwide. The recently published 2022 European Society of Cardiology (ESC)/European Respiratory Society (ERS) guidelines underline the importance of risk stratification not only at baseline but also during follow-up. Achieving a low-risk status has now become the therapeutic goal, emphasising the importance of personalised therapy. The application of these guidelines is also important in determining the timing for lung transplantation referral. In this review, we summarise the most relevant prognostic factors of PAH as well as the parameters used in PAH risk scores and their evolution in the guidelines over the last decade. Finally, we describe the central role that risk stratification plays in the current guidelines not only in European countries but also in Asian countries.

Left Ventricular Fibrosis Assessment by Native T1, ECV, and LGE in Pulmonary Hypertension Patients

Cardiac magnetic resonance imaging (MRI) is emerging as an alternative to right heart catheterization for the evaluation of pulmonary hypertension (PH) patients. The aim of this study was to compare cardiac MRI-derived left ventricle fibrosis indices between pre-capillary PH (PrePH) and isolated post-capillary PH (IpcPH) patients and assess their associations with measures of ventricle function. Global and segmental late gadolinium enhancement (LGE), longitudinal relaxation time (native T1) maps, and extracellular volume fraction (ECV) were compared among healthy controls (N = 25; 37% female; 52 ± 13 years), PH patients (N = 48; 60% female; 60 ± 14 years), and PH subgroups (PrePH: N = 29; 65% female; 55 ± 12 years, IpcPH: N = 19; 53% female; 66 ± 13 years). Cardiac cine measured ejection fraction, end diastolic, and end systolic volumes and were assessed for correlations with fibrosis. LGE mural location was qualitatively assessed on a segmental basis for all subjects. PrePH patients had elevated (apical-, mid-antero-, and mid-infero) septal left ventricle native T1 values (1080 ± 74 ms, 1077 ± 39 ms, and 1082 ± 47 ms) compared to IpcPH patients (1028 ± 53 ms, 1046 ± 36 ms, 1051 ± 44 ms) (p < 0.05). PrePH had a higher amount of insertional point LGE (69%) and LGE patterns characteristic of non-vascular fibrosis (77%) compared to IpcPH (37% and 46%, respectively) (p < 0.05; p < 0.05). Assessment of global LGE, native T1, and ECV burdens did not show a statistically significant difference between PrePH (1.9 ± 2.7%, 1056.2 ± 36.3 ms, 31.2 ± 3.7%) and IpcPH (2.7 ± 2.7%, 1042.4 ± 28.1 ms, 30.7 ± 4.7%) (p = 0.102; p = 0.229 p = 0.756). Global native T1 and ECV were higher in patients (1050.9 ± 33.8 and 31.0 ± 4.1%) than controls (28.2 ± 3.7% and 1012.9 ± 29.4 ms) (p < 0.05). Cardiac MRI-based tissue characterization may augment understanding of cardiac involvement and become a tool to facilitate PH patient classification.

Corrected MRI Pulmonary Transit Time for Identification of Combined Precapillary and Postcapillary Pulmonary Hypertension in Patients With Left Heart Disease

BACKGROUND

The identification of combined precapillary and postcapillary pulmonary hypertension (CpcPH) in patients with pulmonary hypertension (PH) due to left heart disease (LHD) can influence therapy and outcome and is currently based on invasively determined hemodynamic parameters.

PURPOSE

To investigate the diagnostic value of MRI-derived corrected pulmonary transit time (PTTc) in PH-LHD sub-grouped according to hemodynamic phenotypes.

STUDY TYPE

Prospective observational study.

POPULATION

A total of 60 patients with PH-LHD (18 with isolated postcapillary PH [IpcPH] and 42 with CpcPH), and 33 healthy subjects.

FIELD STRENGTH/SEQUENCE

A 3.0 T/balanced steady-state free precession cine and gradient echo-train echo planar pulse first-pass perfusion.

ASSESSMENT

In patients, right heart catheterization (RHC) and MRI were performed within 30 days. Pulmonary vascular resistance (PVR) was used as the diagnostic "reference standard." The PTTc was calculated as the time interval between the peaks of the biventricular signal-intensity/time curve and corrected for heart rate. PTTc was compared between patient groups and healthy subjects and its relationship to PVR assessed. The diagnostic accuracy of PTTc for distinguishing IpcPH and CpcPH was determined.

STATISTICAL TESTS

Student's t-test, Mann-Whitney U-test, linear and logistic regression analysis, and receiver-operating characteristic curves. Significance level: P < 0.05.

RESULTS

PTTc was significantly prolonged in CpcPH compared with IpcPH and normal controls (17.28 ± 7.67 vs. 8.82 ± 2.55 vs. 6.86 ± 2.11 seconds), and in IpcPH compared with normal controls (8.82 ± 2.55 vs. 6.86 ± 2.11 seconds). Prolonged PTTc was significantly associated with increased PVR. Furthermore, PTTc was a significantly independent predictor of CpcPH (odds ratio: 1.395, 95% confidence interval: 1.071-1.816). The area under curve was 0.852 at a cut-off value of 11.61 seconds for PTTc to distinguish between CpcPH and IpcPH (sensitivity 71.43% and specificity 94.12%).

DATA CONCLUSION

PTTc may be used to identify CpcPH. Our findings have potential to improve selection for invasive RHC for PH-LHD patients.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Non-Invasive Cardiac Output Determination Using Magnetic Resonance Imaging and Thermodilution in Pulmonary Hypertension

Magnetic resonance imaging (MRI) can be used to measure cardiac output (CO) non-invasively, which is a paramount parameter in pulmonary hypertension (PH) patients. We retrospectively compared stroke volume (SV) obtained with MRI (SV_MRI) in six localisations against SV measured with thermodilution (TD) (SV_TD) and against each other in 24 patients evaluated in our PH centre using Bland and Altman (BA) agreement analyses, linear correlation, and intraclass correlation (ICC). None of the six tested localisations for SV_MRI reached the predetermined criteria for interchangeability with SV_TD, with two standard deviations (2SD) of bias between 24.1 mL/beat and 31.1 mL/beat. The SV_MRI methods yielded better agreement when compared against each other than the comparison between SV_MRI and SV_TD, with the best 2SD of bias being 13.8 mL/beat. The inter-observer and intra-observer ICCs for CO_MRI were excellent (inter-observer ICC between 0.889 and 0.983 and intra-observer ICC between 0.991 and 0.999). We could not confirm the interchangeability of SV_MRI with SV_TD based on the predetermined interchangeability criteria. The lack of agreement between MRI and TD might be explained because TD is less precise than previously thought. We evaluated a new method to estimate CO through the pulmonary circulation (COp) in PH patients that may be more precise than the previously tested methods.

Clinical Application of 4D Flow MR Imaging to Pulmonary Hypertension

Pulmonary hypertension (PH) is characterized by elevated pulmonary arterial pressure (PAP). Although right-heart catheterization is the gold standard method for the diagnosis of PH by definition, various less-invasive imaging tests have been used for screening, detection of underlying diseases-causing PH, and monitoring of diseases. Among them, 4D flow MRI is an emerging and unique imaging test that allows for comprehensive visualization of blood flow in the right heart and proximal pulmonary arteries. The characteristic blood flow pattern observed in patients with PH is vortical flow formation in the main pulmonary artery. Recent studies have proposed the use of these findings to determine not only the presence of PH but also estimate the mean PAP. Other applications of 4D flow MRI for PH include measurement of wall shear stress, helicity, and 3D flow balance in the pulmonary arteries. It is worth noting that 4D flow has also the potential for longitudinal follow-ups. In this review, the clinical definition of PH, summary of conventional imaging tests, characteristics of pulmonary arterial flow as shown by 4D flow MRI, and clinical application of 4D flow MRI in the management of patients with PH will be discussed.

Right ventricular end-systolic remodeling index on cardiac magnetic resonance imaging: comparison with other functional markers in patients with chronic thromboembolic pulmonary hypertension

BACKGROUND

Cardiac magnetic resonance imaging (CMR) can provide important metrics of pulmonary hypertension. In the current study, we investigated whether the CMR-derived right ventricular end-systolic remodeling index (RVESRI) could be a metric in assessing the function and hemodynamics of chronic thromboembolic pulmonary hypertension (CTEPH).

METHODS

A total of 64 patients (45±14 years, 37 males), including 46 patients with CTEPH and 18 patients with chronic pulmonary thromboembolism (CTE), were retrospectively enrolled. All patients underwent right heart catheterization and CMR within 7 days. RVESRI, right ventricular eccentricity index, right ventricular end-diastolic and end-systolic volume index, right ventricular ejection fraction, right ventricular cardiac output, and strain were analyzed on cine images of CMR. Hemodynamic parameters including mean pulmonary arterial pressure, pulmonary vascular resistance, and cardiac output were obtained from right heart catheterization.

RESULTS

RVESRI of all patients was 1.50 (IQR, 1.26-1.90). Compared with CTE patients, RVESRI in patients with CTEPH was significantly increased (U=27.5, P<0.001). The interclass correlation coefficients of intra-observer reproducibility and inter-observer reproducibility for RVESRI measurement were 0.96 (95% CI, 0.93-0.97) and 0.99 (95% CI, 0.98-0.99), respectively. RVESRI positively correlated with right ventricular end-diastolic and end-systolic volume index and right ventricular global longitudinal strain (r=0.79, 0.83, 0.62, P<0.001), while it was negatively correlated with right ventricular ejection fraction (r=-0.64, P<0.001), right ventricular cardiac output (r=-0.50, P<0.001), and right ventricular eccentricity index (r=-0.81, P<0.001). RVESRI had a positive correlation with mean pulmonary arterial pressure (r=0.65, P<0.001) and pulmonary vascular resistance (r=0.69, P<0.001), while it was negatively correlated with cardiac output (r=-0.64, P<0.001). The receiver operating characteristic curve indicated that RVESRI >1.35 had a sensitivity of 97.8% and specificity of 83.3% in predicting mean pulmonary arterial pressure ≥25 mmHg, and its area under the curve (AUC) was 0.96±0.02. Meanwhile, the AUC of RVESRI was similar to RVEI (Z=1.635, P=0.102) and was more than the diameter of the main pulmonary artery (MPA) (Z=2.26, P=0.02) and the ratio of the MPA and ascending aorta diameter (MPA/AAo) (Z=3.826, P<0.001) in predicting mean pulmonary arterial pressure ≥25 mmHg.

CONCLUSIONS

RVESRI measured on CMR is a simple and reproducible metric in assessing right ventricular function and hemodynamics in CTEPH patients.

An autopsy case of pulmonary arterial hypertension in an elderly patient with multimorbidity: a case report

Background

There is an increasing number of elderly patients with pulmonary arterial hypertension (PAH), and their characteristics differ from those of young or middle-aged patients with this condition.

Case summary

A 73-year-old woman with a history of myocardial infarction and cardiovascular risk factors was admitted to the hospital with 2-week exertional dyspnoea. Her initial diagnosis was heart failure with preserved ejection fraction, but the symptoms persisted despite receiving treatment with diuretics. Additional tests showed a significant decrease in diffusing capacity of carbon monoxide and findings suggestive of severe pulmonary hypertension (PH). Contrast-enhanced computed tomography of the chest, and pulmonary angiography, showed no narrowing or obstruction of the pulmonary arteries. Right heart catheterization revealed haemodynamic data implying pre-capillary PH. Her condition gradually deteriorated to World Health Organization functional class IV, and sequential combination therapy with tadalafil, macitentan, and selexipag was initiated with a PAH diagnosis; however, she died 1 month later. Pathological findings in autopsy were consistent with PAH, and some parts of the lungs revealed the presence of obstructive and interstitial lung disease.

Discussion

The majority of elderly patients with PAH might have multimorbidity. However, there is no specific treatment strategy. It is associated with diagnostic delay and worse prognosis; therefore, early suspicion and comprehensive tests, including right heart catheterization, are essential for better management.

The heart in congenital diaphragmatic hernia: Knowns, unknowns, and future priorities

There is growing recognition that the heart is a key contributor to the pathophysiology of congenital diaphragmatic hernia (CDH), in conjunction with developmental abnormalities of the lung and pulmonary vasculature. Investigations to date have demonstrated altered fetal cardiac morphology, notably relative hypoplasia of the fetal left heart, as well as early postnatal right and left ventricular dysfunction which appears to be independently associated with adverse outcomes. However, many more unknowns remain, not least an understanding of the genetic and cellular basis for cardiac dysplasia and dysfunction in CDH, the relationship between fetal, postnatal and long-term cardiac function, and the impact on other parts of the body especially the developing brain. Consensus on how to measure and classify cardiac function and pulmonary hypertension in CDH is also required, potentially using both non-invasive imaging and biomarkers. This may allow routine assessment of the relative contribution of cardiac dysfunction to individual patient pathophysiological phenotype and enable better, individualized therapeutic strategies incorporating targeted use of fetal therapies, cardiac pharmacotherapies, and extra-corporeal membrane oxygenation (ECMO). Collaborative, multi-model approaches are now required to explore these unknowns and fully appreciate the role of the heart in CDH.

Unsolved problems in CDH follow-up

In patients affected by CDH, survival beyond the neonatal period continues to increase thanks to technological and pharmacological improvements. Conversely, patients, families and caregivers are more and more frequently facing "new" complex late comorbidities, including chronic pulmonary and cardiac dysfunctions, neurodevelopmental challenges, and specific nutritional requirements, that often require ongoing long-term medical or surgical care. Therefore, late morbidity is now a key focus in clinical care of CDH. The aims of this paper are to stress some of the most important "unsolved problems" for CDH patients at long-term follow-up.

Vascular remodeling of the small pulmonary arteries and measures of vascular pruning on computed tomography

Pulmonary hypertension is characterized histologically by intimal and medial thickening in the small pulmonary arteries, eventually resulting in vascular “pruning.” Computed tomography (CT)-based quantification of pruning is associated with clinical measures of pulmonary hypertension, but it is not established whether CT-based pruning correlates with histologic arterial remodeling. Our sample consisted of 138 patients who underwent resection for early-stage lung adenocarcinoma. From histologic sections, we identified small pulmonary arteries and measured the relative area comprising the intima and media (VWA%), with higher VWA% representing greater histologic remodeling. From pre-operative CTs, we used image analysis algorithms to calculate the small vessel volume fraction (BV5/TBV) as a CT-based indicator of pruning (lower BV5/TBV represents greater pruning). We investigated relationships of CT pruning and histologic remodeling using Pearson correlation, simple linear regression, and multivariable regression with adjustment for age, sex, height, weight, smoking status, and total pack-years. We also tested for effect modification by sex and smoking status. In primary models, more severe CT pruning was associated with greater histologic remodeling. The Pearson correlation coefficient between BV5/TBV and VWA% was –0.41, and in linear regression models, VWA% was 3.13% higher (95% CI: 1.95–4.31%, p < 0.0001) per standard deviation lower BV5/TBV. This association persisted after multivariable adjustment. We found no evidence that these relationships differed by sex or smoking status. Among individuals who underwent resection for lung adenocarcinoma, more severe CT-based vascular pruning was associated with greater histologic arterial remodeling. These findings suggest CT imaging may be a non-invasive indicator of pulmonary vascular pathology.

Advances in the management of pulmonary arterial hypertension

The management of pulmonary arterial hypertension (PAH) has significantly evolved over the last decades in the wake of more sensitive diagnostics and specialized clinical programs that can provide focused medical care. In the current era of PAH care, 1-year survival rates have increased to 86%–90% from 65% in the 1980s, and average long-term survival has increased to 6 years from 2.8 years. The heterogeneity in the etiology and disease course has opened doors to focusing research in phenotyping the disease and understanding the pathophysiology at a cellular and genetic level. This may eventually lead to precision medicine and the development of medications that may prevent or reverse pulmonary vascular remodeling. With more insight, clinical trial designs and primary end-points may change to identify the true survival benefit of pharmacotherapy. Identifying responders from non-responders to therapy may help provide individualized patient-centered care rather than an algorithm-based approach. The purpose of this review is to highlight the latest advances in screening, diagnosis, and management of PAH.

Abnormal pulmonary flow is associated with impaired right ventricular coupling in patients with COPD

Cor Pulmonale or right ventricular (RV) dysfunction due to pulmonary disease is an expected complication of COPD resulting primarily from increased afterload mediated by chronic alveolar hypoxemia and resulting hypoxic pulmonary vasoconstriction. Early detection of elevated RV afterload has been previously demonstrated by visualization of abnormal flow patterns in the proximal pulmonary arteries. Prior analysis of helicity in the pulmonary arteries in pulmonary hypertension patients has demonstrated a strong association between helicity and increased RV afterload. However, these flow hemodynamics have yet to be fully explored in patients with COPD. We hypothesized that patients with COPD will have abnormal pulmonary flow as evaluated by 4D-Flow MRI and associated with RV function and pulmonary arterial stiffness. Patients with COPD (n = 15) (65 years ± 6) and controls (n = 10) (58 years ± 9) underwent 4D-Flow MRI to calculate helicity. The helicity was calculated in the main pulmonary artery (MPA) and along the RV outflow tract (RVOT)-MPA axis. Main pulmonary arterial stiffness was measured using the relative area change (RAC). We found COPD patients had decreased helicity relative to healthy controls in the MPA (19.4 ± 7.8vs 32.8 ± 15.9, P = 0.007) and reduced helicity along the RVOT-MPA axis (33.2 ± 9.0 vs 43.5 ± 8.3, P = 0.010). Our investigation indicates a strong association between helicity along the MPA-RV outflow tract axis and RV function and suggests that 4D-Flow MRI might be a sensitive tool in evaluating RV-pulmonary arterial coupling in COPD.