State of the art: advanced imaging of the right ventricle and pulmonary circulation in humans (2013 Grover Conference series)

Dietary intake and glutamine-serine metabolism control pathologic vascular stiffness

Perivascular collagen deposition by activated fibroblasts promotes vascular stiffening and drives cardiovascular diseases such as pulmonary hypertension (PH). Whether and how vascular fibroblasts rewire their metabolism to sustain collagen biosynthesis remains unknown. Here, we found that inflammation, hypoxia, and mechanical stress converge on activating the transcriptional coactivators YAP and TAZ (WWTR1) in pulmonary arterial adventitial fibroblasts (PAAFs). Consequently, YAP and TAZ drive glutamine and serine catabolism to sustain proline and glycine anabolism and promote collagen biosynthesis. Pharmacologic or dietary intervention on proline and glycine anabolic demand decreases vascular stiffening and improves cardiovascular function in PH rodent models. By identifying the limiting metabolic pathways for vascular collagen biosynthesis, our findings provide guidance for incorporating metabolic and dietary interventions for treating cardiopulmonary vascular disease.

Characterization of pulmonary arterial stiffness using cardiac MRI

Pulmonary arterial stiffness (PAS) is a pathologic hallmark of all types of pulmonary hypertension (PH). Cardiac MRI (CMR), a gold-standard imaging modality for the evaluation of pulmonary flow, biventricular morphology and function has been historically reserved for the longitudinal clinical follow-up, PH phenotyping purposes, right ventricular evaluation, and research purposes. Over the last two decades, numerous indices combining invasive catheterization and non-invasive CMR have been utilized to phenotype the character and severity of PAS in different types of PH and to assess its clinically prognostic potential with encouraging results. Many recent studies have demonstrated a strong role of CMR derived PAS markers in predicting long-term clinical outcomes and improving currently gold standard risk assessment provided by the REVEAL calculator. With the utilization of a machine learning strategies, strong diagnostic and prognostic performance of CMR reported in multicenter studies, and ability to detect PH at early stages, the non-invasive assessment of PAS is on verge of routine clinical utilization. In this review, we focus on appraising important CMR studies interrogating PAS over the last 20 years, describing the benefits and limitations of different PAS indices, and their pathophysiologic relevance to pulmonary vascular remodeling. We also discuss the role of CMR and PAS in clinical surveillance and phenotyping of PH, and the long-term future goal to utilize PAS as a biomarker to aid with more targeted therapeutic management.

The investigation and diagnosis of pulmonary hypertension in adults with congenital heart disease

Pulmonary hypertension is not uncommon in adult patients with congenital heart disease and can significantly affect their exercise capacity, quality of life and prognosis. Timely identification and management of pulmonary hypertension in these patients is important. Patients must be allocated to the correct diagnostic group and treatment decided upon, including offering pulmonary arterial hypertension therapies to those who are most likely to benefit.

In this paper, we provide an overview of the diagnostic modalities that are used to investigate and diagnose pulmonary hypertension in modern adult congenital heart disease practice. Emphasis is placed on echocardiography, which is the modality of choice for raising the suspicion of PH, and cardiac catheterisation, which is fundamental in establishing the diagnosis. Other modalities, such as cardiac magnetic resonance imaging and computed tomography can provide complementary information on anatomy and physiology.

Combining all this information into a clinical diagnosis and management plan requires clinical expertise and a multidisciplinary approach, especially when managing this rare and complex group of patients.

Cardiac MRI in Pulmonary Hypertension: From Magnet to Bedside

Pulmonary hypertension (PH) is a disease characterized by progressive rise of pulmonary artery (PA) pressure, which can lead to right ventricular (RV) failure. It is usually diagnosed late because of the nonspecificity of its symptoms. RV performance and adaptation to an increased afterload, reflecting the interaction of the PA and RV as a morphofunctional unit, constitute a critical determinant of morbidity and mortality in these patients. Therefore, early detection of dysfunction may prevent treatment failure. Cardiac MRI constitutes one of the most complete diagnostic modalities for diagnosing PH. It allows evaluation of the morphology and hemodynamics of the PA and RV. Several cine steady-state free-precession (SSFP)-derived parameters (indexed RV end-diastolic volume or RV systolic volume) and phase-contrast regional area change have been suggested as powerful biomarkers for prognosis and treatment. Recently, new cardiac MRI sequences have been added to clinical protocols for PH evaluation, providing brand-new information. Strain analysis with myocardial feature tracking can help detect early RV dysfunction, even with preserved ejection fraction. Four-dimensional flow cardiac MRI can enhance assessment of advanced RV and PA hemodynamics. Late gadolinium enhancement (LGE) imaging may allow detection of replacement fibrosis in PH patients, which is associated with poor outcome. T1 mapping may help detect interstitial fibrosis, even with normal LGE imaging results. The authors analyze the imaging workup of PH with a focus on the role of morphologic and functional cardiac MRI in diagnosis and management of PH, including some of the newer techniques. Online supplemental material is available for this article. ^©RSNA, 2020.

Mitochondria in the Pulmonary Vasculature in Health and Disease: Oxygen-Sensing, Metabolism, and Dynamics

In lung vascular cells, mitochondria serve a canonical metabolic role, governing energy homeostasis. In addition, mitochondria exist in dynamic networks, which serve noncanonical functions, including regulation of redox signaling, cell cycle, apoptosis, and mitochondrial quality control. Mitochondria in pulmonary artery smooth muscle cells (PASMC) are oxygen sensors and initiate hypoxic pulmonary vasoconstriction. Acquired dysfunction of mitochondrial metabolism and dynamics contribute to a cancer-like phenotype in pulmonary arterial hypertension (PAH). Acquired mitochondrial abnormalities, such as increased pyruvate dehydrogenase kinase (PDK) and pyruvate kinase muscle isoform 2 (PKM2) expression, which increase uncoupled glycolysis (the Warburg phenomenon), are implicated in PAH. Warburg metabolism sustains energy homeostasis by the inhibition of oxidative metabolism that reduces mitochondrial apoptosis, allowing unchecked cell accumulation. Warburg metabolism is initiated by the induction of a pseudohypoxic state, in which DNA methyltransferase (DNMT)-mediated changes in redox signaling cause normoxic activation of HIF-1α and increase PDK expression. Furthermore, mitochondrial division is coordinated with nuclear division through a process called mitotic fission. Increased mitotic fission in PAH, driven by increased fission and reduced fusion favors rapid cell cycle progression and apoptosis resistance. Downregulation of the mitochondrial calcium uniporter complex (MCUC) occurs in PAH and is one potential unifying mechanism linking Warburg metabolism and mitochondrial fission. Mitochondrial metabolic and dynamic disorders combine to promote the hyperproliferative, apoptosis-resistant, phenotype in PAH PASMC, endothelial cells, and fibroblasts. Understanding the molecular mechanism regulating mitochondrial metabolism and dynamics has permitted identification of new biomarkers, nuclear and CT imaging modalities, and new therapeutic targets for PAH. © 2020 American Physiological Society. Compr Physiol 10:713-765, 2020.

EXPRESS: Statement on imaging and pulmonary hypertension from the Pulmonary Vascular Research Institute (PVRI)

Pulmonary hypertension (PH) is highly heterogeneous and despite treatment advances it remains a life-shortening condition. There have been significant advances in imaging technologies, but despite evidence of their potential clinical utility, practice remains variable, dependent in part on imaging availability and expertise. This statement summarizes current and emerging imaging modalities and their potential role in the diagnosis and assessment of suspected PH. It also includes a review of commonly encountered clinical and radiological scenarios, and imaging and modeling-based biomarkers. An expert panel was formed including clinicians, radiologists, imaging scientists, and computational modelers. Section editors generated a series of summary statements based on a review of the literature and professional experience and, following consensus review, a diagnostic algorithm and 55 statements were agreed. The diagnostic algorithm and summary statements emphasize the key role and added value of imaging in the diagnosis and assessment of PH and highlight areas requiring further research.

Non-invasive Multimodality Cardiovascular Imaging of the Right Heart and Pulmonary Circulation in Pulmonary Hypertension

Pulmonary hypertension (PH) is defined as resting mean pulmonary arterial pressure (mPAP) ≥25 millimeters of mercury (mmHg) via right heart (RH) catheterization (RHC), where increased afterload in the pulmonary arterial vasculature leads to alterations in RH structure and function. Mortality rates have remained high despite therapy, however non-invasive imaging holds the potential to expedite diagnosis and lead to earlier initiation of treatment, with the hope of improving prognosis. While historically the right ventricle (RV) had been considered a passive chamber with minimal role in the overall function of the heart, in recent years in the evaluation of PH and RH failure the anatomical and functional assessment of the RV has received increased attention regarding its performance and its relationship to other structures in the RH-pulmonary circulation. Today, the RV is the key determinant of patient survival. This review provides an overview and summary of non-invasive imaging methods to assess RV structure, function, flow, and tissue characterization in the setting of imaging's contribution to the diagnostic, severity stratification, prognostic risk, response of treatment management, and disease surveillance implications of PH's impact on RH dysfunction and clinical RH failure.

Pulmonary Hypertension in Intensive Care Units: An Updated Review

Pulmonary hypertension (PH) is a condition associated with high morbidity and mortality. Patients with PH who require critical care usually have severe right ventricular (RV) dysfunction. Although different groups of PH have different etiologies, pulmonary vascular dysfunction is common in these groups. PH can lead to increased pulmonary artery pressure, which can ultimately cause RV failure. Clinicians should be familiar with the presentations of this disease and diagnostic tools. The contributing factors, if present (e.g., sepsis), and coexisting conditions (e.g., arrhythmias) should be identified and addressed accordingly. The preload should be optimized by fluid administration, diuretics, and dialysis, if necessary. On the other hand, the RV afterload should be reduced to improve the RV function with pulmonary vasodilators, such as prostacyclins, inhaled nitric oxide, and phosphodiesterase type 5 inhibitors, especially in group 1 PH. Inotropes are also used to improve RV contractility, and if inadequate, use of ventricular assist devices and extracorporeal life support should be considered in suitable candidates. Moreover, vasopressors should be used to maintain systemic blood pressure, albeit cautiously, as they increase the RV afterload. Measures should be also taken to ensure adequate oxygenation. However, mechanical ventilation is avoided in RV failure. In this study, we reviewed the pathophysiology, manifestations, diagnosis, monitoring, and management strategies of PH, especially in intensive care units.

Right ventricular involvement in cardiac sarcoidosis demonstrated with cardiac magnetic resonance

AIMS

Cardiac involvement in sarcoidosis is reported in up to 30% of patients. Left ventricular involvement demonstrated by contrast-enhanced cardiac magnetic resonance has been well validated. We sought to determine the prevalence and distribution of right ventricular late gadolinium enhancement in patients diagnosed with pulmonary sarcoidosis.

METHODS AND RESULTS

We prospectively evaluated 87 patients diagnosed with pulmonary sarcoidosis with contrast-enhanced cardiac magnetic resonance for right ventricular involvement. Pulmonary artery pressures were non-invasively evaluated with Doppler echocardiography. Patient characteristics were compared between the groups with and without right ventricular involvement, and right ventricular enhancement was correlated with pulmonary hypertension, ventricular mass, volume, and systolic function. Left ventricular late gadolinium enhancement was demonstrated in 30 patients (34%). Fourteen patients (16%) had right ventricular late gadolinium enhancement, with sole right ventricular enhancement in only two patients. The pattern of right ventricular enhancement consisted of right ventricular outflow tract enhancement in 1 patient, free wall enhancement in 8 patients, ventricular insertion point enhancement in 10 patients, and enhancement of the right side of the interventricular septum in 11 patients. Pulmonary arterial hypertension correlated with the presence of right ventricular enhancement (P < 0.001). Right ventricular enhancement correlated with systolic ventricular dysfunction (P < 0.001), hypertrophy (P = 0.001), and dilation (P < 0.001).

CONCLUSIONS

Right ventricular enhancement was present in 16% of patients diagnosed with pulmonary sarcoidosis and in 48% of patients with left ventricular enhancement. The presence of right ventricular enhancement correlated with pulmonary arterial hypertension, right ventricular systolic dysfunction, hypertrophy, and dilation.

Relationship of Right Ventricular Size and Function with Respiratory Status in Duchenne Muscular Dystrophy

The relationship between pulmonary function and right ventricle (RV) in Duchenne muscular dystrophy (DMD) has not been evaluated. Using cardiac magnetic resonance (CMR), we describe the relationship of RV size and function with spirometry in a DMD cohort. Fifty-seven boys undergoing CMR and pulmonary function testing within 1 month at a single center (2013-2015) were enrolled. Comparisons of RV ejection fraction (RVEF) and end-diastolic volume index (RVEDVI) were made across categories of percent forced vital capacity (FVC%), and relationships were assessed. Mean age was 15.5 ± 3.5 years. Spirometry and CMR were performed within 3.9 ± 4.1 days. Median FVC% was 92.0 % (67.5-116.5 %). Twenty-three (40 %) patients had abnormal FVC% (<80 %) of which 13 (57 %) had mild (FVC% 60-79 %), 6 (26 %) had moderate (FVC% 40-59 %), and 4 (17 %) had severe (FVC <40 %) reductions. Mean RVEF was 58.3 ± 3.7 %. Patients with abnormal FVC% were older and had lower RVEF and RVEDVI. Both RVEF and RVEDVI were significantly associated with FVC% (r = 0.31, p = 0.02 and r = 0.39, p = 0.003, respectively). In a large DMD cohort, RVEF and RVEDVI were related to FVC%. Worsening respiratory status may guide monitoring of cardiac function in these patients.

Imaging the heart in pulmonary hypertension: an update

Noninvasive imaging of the heart plays an important role in the diagnosis and management of pulmonary hypertension (PH), and several well-established techniques are available for assessing performance of the right ventricle, the key determinant of patient survival. While right heart catheterisation is mandatory for establishing a diagnosis of PH, echocardiography is the most important screening tool for early detection of PH. Cardiac magnetic resonance imaging (CMRI) is also a reliable and practical tool that can be used as part of the diagnostic work-up. Echocardiography can measure a range of haemodynamic and anatomical variables (e.g. pericardial effusion and pulmonary artery pressure), whereas CMRI provides complementary information to echocardiography via high-resolution, three-dimensional imaging. Together with echocardiography and CMRI, techniques such as high-resolution computed tomography and positron emission tomography may also be valuable for screening, monitoring and follow-up assessments of patients with PH, but their clinical relevance has yet to be established. Technological advances have produced new variants of echocardiography, CMRI and positron emission tomography, and these permit closer examination of myocardial architecture, motion and deformation. Integrating these new tools into clinical practice in the future may lead to more precise noninvasive determination of diagnosis, risk and prognosis for PH.